EA049106B1 - INJECTION COMPOSITION - Google Patents

Abstract

The invention provides pharmaceutical compositions, methods for their preparation, and their use. The pharmaceutical compositions comprise a salt of an optionally substituted dimethyltryptamine compound, a buffer that is separate from the salt, and water. The compositions have a pH of about 3.5 to about 6.5 and an osmolality of about 250 to about 350 mOsm/kg. Optionally, such compositions are suitable for injection, being both stable and clinically acceptable, and have potential use in the treatment of psychiatric or neurological disorders.

Description

Field of technology

The present invention relates to pharmaceutical compositions, methods for their preparation and their use. The pharmaceutical compositions comprise a salt of an optionally substituted dimethyltryptamine compound, a buffer that is separate from the salt, and water. The compositions have pH values from about 3.5 to about 6.5 and osmolality from about 250 to about 350 mOsm/kg. Optionally, such compositions are suitable for injection, being both stable and clinically acceptable, and have potential use in the treatment of mental or neurological disorders.

State of the art

Classic hallucinogenic drugs have shown preclinical and clinical promise in the treatment of psychiatric disorders (Carhart-Harris and Goodwin, Neuropsychopharmacology 42, 2105–2113 (2017)). In particular, psilocybin has shown significant improvements on a number of depression and anxiety rating scales in randomized, double-blind studies (Griffiths et al. Journal of Psychopharmacology, 30(12), 1181–1197 (2016)).

^№Dimethyltryptamine (DMT) also has therapeutic value as a short-acting hallucinogenic substance. A review of studies on the biosynthesis and metabolism of DMT in the brain and peripheral tissues, methods and results for detecting DMT in body fluids and the brain, new sites of action of DMT, and new data on the possible physiological and therapeutic role of DMT is provided by S. A. Barker in Front. Neurosci., 12, 536, 1-17 (2018). This review describes that DMT has a possible therapeutic role in the treatment of depression, obsessive-compulsive disorder, and substance abuse disorders.

Injection of saline solutions of DMT fumarate salts into human volunteers is described in S. Timmermann et al., Sci. Rep., 9, 16324 (2019). The effects of DMT fumarate on the power spectrum and signal diversity of human brain activity were recorded using multivariate EEG and compared with the results obtained with placebo (saline) injection. It was found that, compared with the results obtained with placebo, DMT fumarate suppressed alpha power and normalized/increased the possibility of delta and theta signals. Alpha signal power has been associated with high-level psychological functioning, top-down predictive processing and related feedback, while theta and delta signal power are classically associated with REM sleep dreaming and related fantasy states. These results are described as linking the injection of DMT fumarate with a feeling of deep immersion in an entirely different world.

According to the Human Metabolism Database (HMDB), dimethyltryptamine is degraded relatively rapidly in solution (see, in particular, http://www.hmdb.ca/metabolites/HMDB0005973). Therefore, there is a need in the art for injectable DMT solutions that are stable for longer periods of time and are clinically acceptable. The present invention satisfies this need.

Brief description of the essence of the invention

The present invention relates to pharmaceutical compositions, optionally suitable for injection, comprising a salt of an optionally substituted dimethyltryptamine compound, a buffer that is separate from the salt, and water, wherein the compositions have pH values from about 3.5 to about 6.5 and typical osmolalities from about 250 to about 350 mOsm/kg. Human serum has a pH of about 7.4 (typically in the range of 7.35 to 7.45, see G. K. Schwalfenberg, J. Environ. Public Health, 2012; 2012:727630), and it is apparent that a preferred composition of the salts of the optionally substituted dimethyltryptamine compounds is isotonic at pH 7.4. It has now been discovered that compositions described in or adapted from the prior art have suboptimal shelf life when stored at ambient conditions. The present invention is aimed at solving this problem of creating pharmaceutical compositions, optionally suitable for injection, with a significantly reduced amount of degradation products compared to known compositions when stored under stress conditions. This indicates an improved shelf life compared to such pharmaceutical compositions described in the prior art.

Accordingly, in view of the first aspect, the present invention provides a pharmaceutical composition, optionally suitable for injection, comprising a salt of a dimethyltryptamine compound optionally substituted with deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy or at position 4 with monohydrogen phosphate; a buffer that is separate from the salt; and water, wherein the composition has a pH of from about 3.5 to about 6.5 and an osmolality of from about 250 to about 350 mOsm/kg.

In terms of a second aspect, the present invention provides a kit suitable for preparing a composition according to the first aspect, said kit comprising a salt of a dimethyltryptamine compound optionally substituted with deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy, or at position 4 with monohydrogen phosphate; and a buffer which is separately

- 1 049106 nym from salt.

In terms of the third aspect, the present invention provides a method for producing a pharmaceutical composition according to the first aspect, comprising reacting a salt, a buffer, water and, optionally, a tonicity adjusting agent. In some embodiments, the composition or formulation according to the first and second aspects comprises a tonicity adjusting agent.

Because of the instability of dimethyltryptamine in solution, solutions containing dimethyltryptamine are typically prepared immediately before use or immediately before use, i.e., storage of dimethyltryptamine solutions is avoided. Alternatively, dimethyltryptamine solutions are frozen. The inventors have found that when using a buffer separate from the salt, the resulting compositions are more stable than compositions prepared without a buffer separate from the salt. In addition, when using a container adapted to prevent penetration of ultraviolet light, the resulting compositions are more stable than compositions stored in containers allowing penetration of ultraviolet light.

Thus, from the viewpoint of the fourth aspect, the present invention provides the use of a buffer for reducing the degradation of an injectable pharmaceutical composition of a salt of a dimethyltryptamine compound optionally substituted with deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy or at position 4 with monohydrogen phosphate.

From the point of view of the fifth aspect, the present invention provides a composition according to the first aspect for use in therapy.

In terms of a sixth aspect, the present invention provides a composition according to the first aspect for use in a method for treating a mental or neurological disorder in a patient.

From the viewpoint of the seventh aspect, the present invention provides a method for treating a mental or neurological disorder, comprising administering to a patient in need thereof a composition according to the first aspect.

Additional aspects and embodiments of the present invention will be apparent from the following discussion.

Detailed description of the invention

In the present description, one or more aspects of the invention may be combined with one or more features given in the description to define separate embodiments of the invention.

In the following discussion, reference is made to a number of terms which should be understood to have the meanings given below unless the context clearly indicates otherwise. The nomenclature used in this document to define compounds, in particular the compounds described herein, shall conform to the rules of the International Union of Pure and Applied Chemistry (IUPAC) for chemical compounds, in particular the IUPAC Compendium of Chemical Terminology (Gold Book) (see A. D. Jenkins et al., Pure & Appl. Chem., 1996, 68, 2287-2311). For the avoidance of doubt, if any rule of the IUPAC conflicts with a definition given in this document, this definition shall prevail.

References made in this document to the singular of a noun include the plural of that noun and vice versa, unless the context otherwise requires.

Throughout this specification, the word "comprise" or variations such as "includes" or "including" shall be understood to imply the inclusion of the stated element, integer, or step, or group of elements, integers, or steps, but not the exclusion of any other element, integer, or step, or group of elements, integers, or steps.

The term "comprising" or "variants" shall be understood to imply the inclusion of the stated element, integer or step, or group of elements, integers or steps, and the exclusion of any other element, integer or step, or group of elements, integers or steps.

The term "about" is used herein when specifying a number or value to mean values that are within ±5% of the stated value. For example, if a pH range of about 3.5 to about 6.5 is stated, pH values from 3.3 to 6.8 are included.

The compositions according to the present invention are suitable for therapy and can be administered to a patient in need thereof. The term patient as used herein preferably refers to a mammal. Typically, the mammal is a human, but may also refer to a domestic mammal. This term does not extend to laboratory mammals.

The term treatment defines a therapeutic treatment of a patient aimed at reducing or stopping the rate of progression of a disorder or at alleviating or curing the disorder. Prevention of the disorder by treatment is also included. References to prevention herein do not require complete prevention of the disorder: instead, its progression may be slowed by treatment in accordance with the present invention. Typically, the treatment is not prophylactic, and the composition is administered to a patient diagnosed or suspected of having the disorder.

As is known in the art, mental or neurological disorders are disorders that may be associated with one or more cognitive impairments. As used herein, the term psychiatric disorder is a clinically significant behavioral or psychological syndrome or pattern that occurs in an individual and is associated with ongoing distress (e.g., a painful symptom) or disability (i.e., impairment in one or more important areas of functioning) or with a significantly increased risk of death, pain, disability, or serious loss of freedom.

The diagnostic criteria for the mental or neurological disorders mentioned in this document are presented in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).

As used herein, the term obsessive-compulsive disorder (OCD) is defined by the presence of either obsessions or compulsions, but usually both. Symptoms may cause significant functional impairment and/or distress. An obsession is defined as an unwanted, persistent thought, image, or impulse that repeatedly occurs in a person's mind. A compulsion is a repetitive behavior or mental act that a person is driven to perform. Typically, OCD manifests as one or more obsessions that lead to the acceptance of the compulsive state. For example, an obsession about germs may lead to a compulsion to clean, or an obsession about food may lead to a compulsion to overeat, eat too little, or vomit after eating (i.e., an obsession about food may manifest as an eating disorder). A compulsion can be either overt and observable by others, such as checking to see if a door is locked, or a covert mental action that cannot be observed, such as repeating a certain phrase in your mind.

The present invention provides a composition or kit according to the first and second aspects of the invention for use in a method for treating an eating disorder. The term eating disorder includes anorexia nervosa, bulimia and binge eating disorder (BED). Symptoms of anorexia nervosa include eating too little food and/or exercising too much in order to maintain body weight as low as possible. Symptoms of bulimia include eating a large amount of food in a very short period of time (i.e., binge eating) and then deliberately vomiting, using laxatives, eating too little food and/or exercising too much in order to prevent weight gain. Symptoms of BED include regularly eating large portions of food until unpleasantly full and, as a result, feeling upset or guilty.

As used herein, the term depressive disorder includes major depressive disorder, persistent depressive disorder, bipolar disorder, bipolar depression, and depression in terminally ill patients.

As used herein, major depressive disorder (MDD, also referred to as major depression or clinical depression) is defined as the presence of five or more of the following symptoms over a two-week or longer period (also referred to herein as a major depressive episode) most of the day, nearly every day:

depressive mood, such as feeling sad, empty, or tearful (in children and adolescents, depressive mood may manifest as persistent irritability);

significantly decreased interest or lack of pleasure in all or most activities;

significant weight loss without dieting, weight gain, or decreased or increased appetite (in children, failure to gain the expected weight);

insomnia or increased desire to sleep;

either restlessness or slowed behavior that can be observed by others;

fatigue or loss of energy;

feelings of worthlessness or excessive or inappropriate guilt;

problems making decisions or problems thinking or concentrating; recurring thoughts of death or suicide, or a suicide attempt.

At least one symptom must be either depressed mood or loss of interest or pleasure.

Persistent depressive disorder, also known as dysthymia, is defined as a patient having both of the following:

A. Depressed mood most of the time nearly every day for at least two years. Children and adolescents may have an irritable mood and the time frame is at least a year.

B. During depression, a person experiences at least two of the following symptoms:

Either overeating or lack of appetite.

Sleeps too much or has difficulty sleeping.

Fatigue, lack of energy.

Poor self-esteem.

Difficulty concentrating or making decisions. The term used in this document is

- 3 049106 min Treatment-resistant major depressive disorder describes MDD in which an adequate response to adequate treatment with standard care therapy cannot be achieved.

As used herein, the term bipolar disorder, also known as manic-depressive illness, is a disorder that causes unusual shifts in mood, energy, activity levels, and ability to perform daily tasks.

There are two distinct subcategories of bipolar disorder; all involve marked changes in mood, energy, and activity levels. These moods range from periods of extremely heightened, elevated, and energetic behavior (known as manic episodes, defined below) to periods of intense sadness, depression, or hopelessness (known as depressive episodes). Less severe manic periods are known as hypomanic episodes.

Bipolar I disorder - is defined by manic episodes that last at least 7 days, or manic symptoms that are so severe that the person requires immediate hospitalization. Depressive episodes usually also occur, usually lasting at least 2 weeks. Depressive episodes with mixed features (the simultaneous presence of depressive and manic symptoms) are also possible.

Bipolar II disorder is defined by a pattern of depressive episodes and hypomanic episodes, but not the full-blown manic episodes described above.

As used in this document, the term bipolar depression is defined as an individual who experiences depressive symptoms with a preceding or concomitant episode of manic symptoms but does not meet the clinical criteria for bipolar disorder.

As used herein, the term anxiety disorder includes generalized anxiety disorder, phobia, panic disorder, social anxiety disorder, and post-traumatic stress disorder.

The term generalized anxiety disorder (GAD) as used herein refers to a chronic disorder characterized by long-term anxiety that is not focused on any one object or situation. People with GAD experience non-specific, persistent fear and worry, and are overly preoccupied with everyday activities. GAD is characterized by chronic, excessive worry, accompanied by three or more of the following symptoms: restlessness, fatigue, difficulty concentrating, irritability, muscle tension, and sleep disturbance.

A phobia is defined as a persistent fear of an object or situation that the sufferer will go to great lengths to avoid, usually out of proportion to the actual danger. If the feared object or situation cannot be completely avoided, the sufferer will experience it with marked distress and significant interference with social or occupational functioning.

A patient suffering from panic disorder is defined as a person who experiences one or more brief episodes (also called panic attacks) of intense fear and apprehension, often accompanied by tremors, shaking, confusion, dizziness, nausea and/or difficulty breathing. A panic attack is defined as fear or discomfort that occurs suddenly and reaches its peak in less than ten minutes.

Social anxiety disorder is defined as intense fear and avoidance of negative public attention, public embarrassment, humiliation, or social interaction. Social anxiety often presents with specific physical symptoms, including blushing, sweating, and difficulty speaking.

Post-traumatic stress disorder (PTSD) is an anxiety disorder that results from a traumatic experience. PTSD can result from an extreme situation such as combat, a natural disaster, rape, hostage situations, child abuse, bullying, or even a serious accident. Common symptoms include hypervigilance, flashbacks, avoidance behavior, anxiety, anger, and depression.

As used herein, postpartum depression (PPD, also known as postnatal depression) is a form of depression experienced by either parent of a newborn baby. Symptoms typically develop within 4 weeks after the baby is born and often include intense sadness, fatigue, anxiety, loss of interest or pleasure in hobbies and activities, irritability, and changes in sleeping or eating patterns.

As used in this document, the term substance abuse means a pattern of drug use in which the user uses the substance in amounts or in ways that are harmful to themselves or others.

As used in this document, the term volitional disorder refers to a disorder that includes as a symptom a decrease in motivation to initiate and perform self-directed, goal-directed activity.

The present invention provides a pharmaceutical composition, optionally suitable for injection, comprising a salt of a dimethyltryptamine compound (DMT), optionally substituted

- 4 049106 deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy or at position 4 with monohydrogen phosphate; a buffer that is separate from the salt; and water, wherein the composition has a pH of from about 3.5 to about 6.5 and an osmolality of from about 250 to about 350 mOsm/kg.

The inventors have found that this composition is unexpectedly more stable than compositions prepared at a higher pH (in particular, compositions prepared at a pH that matches human serum, i.e., at a pH of about 7.4). The higher stability of the composition according to the invention compared to the preferred composition is discussed in more detail in the Examples section.

Osmolality is formally defined as the ratio of the negative natural logarithm of the rational activity of water to the molar mass of water, represented by the formula:

-lna _w p osmolality = -----; a,,= —

18,015 ^w p* where p is the partial vapor pressure of water in solution and p* is the partial vapor pressure of pure water. Simply put, osmolality is the number of osmotically active particles (the number of solute particles) in 1 kg of solution. Thus, osmolality depends only on the number of particles and is not related to the molecular weight, size, shape, or charge of the particles (see DK Faria et al., ME Mendes and NM Sumita, J. Bras. Patol. Med. Lab., 53, 1, 38–45 (2017) for a review of serum osmolality measurement). For example, one mole of a non-dissociating substance (e.g., DMT free base) dissolved in 1 kg of water has an osmolality of 1 Osm/kg (1000 mOsm/kg), whereas one mole of a substance that dissociates into two separate species in solution (e.g., DMT fumarate) dissolved in 1 kg of water has an osmolality of 2 Osm/kg (2000 mOsm/kg).

When a first solution is defined herein as being isotonic with a second solution, the solutions have the same osmolality. For example, when a composition is defined as being isotonic with human serum, the composition has the same osmolality as human serum. The osmolality of human serum is typically between about 275 and about 300 mOsm/kg (L. Hooper et al., BMJ Open, 2015; 5(10):e008846).

The composition (i.e., according to the present invention) is optionally suitable for injection, which means that it meets the pharmacopoeial requirements for sterility, contaminants and pyrogens (see, for example, the United States Pharmacopeial Convention, General Requirements / (1) Injections, p. 33). Sometimes the composition contains microbial growth inhibitors (e.g., antimicrobial preservatives) and/or antioxidants.

Compositions suitable for injection have a pH of about 3 to 9 and an osmolality of about 250 to about 600 mOsm/kg. pH values above 9 are described by I. Usach et al. in Adv. Ther., 36, 2986-2996 (2019) and are associated with tissue necrosis (cell death in tissue), while values below 3 are reported to cause pain and phlebitis (inflammation of the veins). Osmolality values above 600 mOsm/kg are also reported to cause pain. The pH and osmolality of the composition according to the invention are in the ranges reported to be suitable for injection.

The composition comprises a salt of a DMT compound optionally substituted with deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy, or at position 4 with monohydrogen phosphate, referred to herein as a DMT compound. The compositions according to the present invention may comprise one or more DMT compounds. For the avoidance of doubt, the compositions comprise an optionally substituted DMT salt if they comprise optionally substituted DMT ions and ions that counteract the charge of the optionally substituted DMT ions (counter ions). Accordingly, the salt of optionally substituted DMT in the composition can be formed, for example, by reacting optionally substituted DMT as a free base with an aqueous solution containing an excess of buffer relative to the molar amount of optionally substituted DMT.

The compound DMT is optionally substituted with deuterium, where the deuterium atom is a hydrogen atom with an extra neutron. The compound DMT is also optionally substituted at the 4- or 5-position with acetoxy or methoxy or at the 4-position with monohydrogen phosphate. The term acetoxy (often abbreviated OAc) defines the monovalent group derived from acetic acid by the removal of a hydrogen atom from the OH group. The term methoxy (often abbreviated OMe) defines the monovalent group derived from methanol by the removal of a hydrogen atom from the OH group. The term monohydrogen phosphate defines the divalent group of the formula HPO ₄ , derived from phosphoric acid by the removal of a proton from two of the three OH moieties, and thus denotes a substituent of the formula -OP(O)(OH)O ^- .

In some embodiments, the dimethyltryptamine compound is optionally substituted at position 5 with methoxy or at position 4 with acetoxy or monohydrogen phosphate.

If the compound DMT is substituted at position 4 with monohydrogen phosphate, this should reflect the fact that psilocybin (also known as [3-(2-dimethylaminoethyl)-1-indol-4-yl]dihydrogen phosphate) in water typically has monohydrogen phosphate at position 4, which is generally considered to be the predominant form due to the pKa values of the two terminal oxygen atoms of the phosphate, which are estimated to be 1.3 and 6.5. It should also be understood that the form of psilocybin containing monohydrogen phosphate exists as a zwitterion

- 5 049106 ion (i.e., an inner salt) in which the nitrogen atom of the dimethylamino group is protonated. Thus, this form is, and psilocybin should be considered as a salt of the compound DMT substituted at position 4 by monohydrogen phosphate.

In some embodiments, the dimethyltryptamine compound is optionally substituted with deuterium at one or more positions selected from the α, β, and dimethyl carbon atoms. In further embodiments, the dimethyltryptamine compound is optionally substituted at one or more positions selected from the α and β carbon atoms, such as the α carbon.

For the avoidance of doubt, positions 4, 5, α and β of the optionally substituted DMT salt refer to the positions labeled in the structure below (substitution not shown).

The composition comprises a buffer that is separate from the salt, i.e., the buffer is not simply a counterion for the optionally substituted DMT. For example, when the salt is dimethyltryptamine fumarate (i.e., the fumaric acid salt of dimethyltryptamine), an amount of buffer is needed in excess of the amount of buffer provided by the fumarate. The term buffer is well known in the art and refers to a chemical substance that, when included in a composition, resists a change in pH upon addition of an acid or base to the composition. In the composition, the buffer comprises a weak acid and its conjugate base. A suitable buffer comprises an acid with a pKa value within ±1 of the desired pH of the composition. For example, if the desired pH of the composition is about 4.0, a suitable buffer comprises a weak acid with a pKa value from about 3.0 to about 5.0. If the buffer acid has more than one pKa value (i.e., each acid molecule is capable of donating more than one proton), then for the buffer to be suitable, at least one of the pKa values must be within the desired pH range.

The weak acid and the conjugate base of the buffer are in equilibrium with each other. According to Le Chatelier's principle (if a constraint (e.g., a change in the concentration of a reactant) is applied to a system at equilibrium, the equilibrium will shift to counteract the effect of the constraint), adding an acid or base to a composition shifts the equilibrium position in favor of the conjugate base or the weak acid, respectively. Consequently, the concentration of free protons in the composition (and hence the pH) is relatively unchanged.

As described above, the composition of the present invention has a pH of from about 3.5 to about 6.5. In some embodiments, the buffer comprises an acetate salt and acetic acid (pKa = 4.75); a citrate salt and citric acid (pKa = 3.13, 4.76, and 6.40); an ascorbate salt and ascorbic acid (pKa = 4.17 and 11.6); a benzoate salt and benzoic acid (pKa = 4.20); a phosphate salt and phosphoric acid (pKa = 2.14, 7.20, and 12.37); an oxalate salt and oxalic acid (pKa = 1.25 and 4.14); or a formate and formic acid (pKa = 3.75). The pKa values given in this document are those given at 25°C in water. Typically, a buffer contains only one of the pairs listed above, i.e., one acid and its conjugate base.

In some embodiments, the buffer comprises an acetate salt and acetic acid; a citrate salt and citric acid; an ascorbate salt and ascorbic acid; a benzoate salt and benzoic acid; or a phosphate salt and phosphoric acid.

In some embodiments, the pH of the composition is from about 3.75 to about 6.5, such as from about 3.75 to about 5.75. Often, the pH of the composition is from about 3.75 to about 4.25, typically about 4.0. In such embodiments, the buffer often comprises an acetate salt and acetic acid; a citrate salt and citric acid; an ascorbate salt and ascorbic acid; a benzoate salt and benzoic acid; an oxalate salt and oxalic acid; or a formate salt and formic acid. Sometimes, the buffer comprises an acetate salt and acetic acid; a citrate salt and citric acid; an ascorbate salt and ascorbic acid; or a benzoate salt and benzoic acid.

In some embodiments, the buffer comprises an acetate salt and acetic acid, often sodium acetate and acetic acid or potassium acetate and acetic acid.

The concentration of the buffer in the composition is typically high enough to withstand significant changes in the pH of the composition when the composition is stored for two weeks (i.e., the pH typically fluctuates by less than about 0.1 pH units), and low enough that the osmolality of the composition is within a desired range. One skilled in the art can evaluate and achieve suitable buffer concentrations. Often, the buffer concentration is from about 15 mM to about 75 mM, such as from about 20 mM to about 30 mM. In some embodiments, the buffer concentration is about 25 mM.

- 6 049106

As described above, the composition comprises a salt of a DMT compound optionally substituted with deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy, or at position 4 with monohydrogen phosphate.

A salt contains an acid and a DMT compound, or a salt contains a DMT compound substituted at position 4 by monohydrogen phosphate. An example of a salt containing an acid and a DMT compound is dimethyltryptamine fumarate, which is a salt of dimethyltryptamine with fumaric acid. P. H. Stahl and C. G. Wermuth reviewed pharmaceutical salts and the acids they contain in Handbook of Pharmaceutical Salts:

Properties, Selection and Use, Weinheim/Zurich:Wiley-VCH/VHCA, 2002. The acids described in this review are suitable acids for inclusion in the salt.

The salt may contain an acid selected from the group consisting of fumaric acid, tartaric acid, citric acid, acetic acid, lactic acid, gluconic acid, 1-hydroxy-2-naphthoic acid, 2,2-dichloroacetic acid, 2-hydroxyethanesulfonic acid, 2-oxoglutaric acid, 4-acetamidobenzoic acid, 4-aminosalicylic acid, adipic acid, ascorbic acid, aspartic acid, benzenesulfonic acid, benzoic acid, camphoric acid, camphor-10-sulfonic acid, decanoic acid, hexanoic acid, octanoic acid, carbonic acid, cinnamic acid, cyclamic acid, dodecylsulfuric acid, ethane-1,2-disulfonic acid, ethanesulfonic acid, formic acid, galactaric acid, gentisic acid, glucoheptonic acid, glucuronic acid, glutamic acid, glutaric acid, glycerophosphoric acid, glycolic acid, hippuric acid, hydrobromic acid, hydrochloric acid, isobutyric acid, lactobionic acid, lauric acid, maleic acid, malic acid, malonic acid, mandelic acid, methanesulfonic acid, naphthalene-1,5-disulfonic acid, naphthalene-2-sulfonic acid, nicotinic acid, nitric acid, oleic acid, oxalic acid, palmitic acid, pamoic acid, phosphoric acid, propionic acid, pyroglutamic acid (-L), salicylic acid, sebacic acid, stearic acid, succinic acid, sulfuric acid, thiocyanic acid, toluenesulfonic acid and undecylenic acids.

In some embodiments, where the salt comprises an acid and a DMT compound, the acid is a Bronsted acid having a pKa at 25°C in water of about 3 to about 5. In these embodiments, the Bronsted acid can act as a counterion to the DMT compound and as a buffer. Thus, the composition can be stabilized to a greater extent, i.e., the degradation of the DMT compound can be further reduced, when the salt comprises such an acid.

In some embodiments, the salt comprises a Bronsted acid having a pKa at 25°C of from about 3 to about 5 and a compound of Formula I.

n

Formula I wherein R ⁴ and R ⁵ are both H, and each ^x H and each Y H are independently selected from H and D, or one of R ⁴ and R ⁵ is H and the other is acetoxy or methoxy, each ^Y H is H, and each ^x H is independently selected from H and D, or the salt comprises a compound of formula I wherein R ⁴ is monohydrogen phosphate, R ⁵ is H, and each ^Y H and each ^x H is H.

In some embodiments, ^R4 and ^R5 are both H. In these embodiments, the DMT compound is any compound or combination of N,N-dimethyltryptamine, a-monodeutero-N-dimethyltryptamine, a,a@-dideutero-N-dimethyltryptamine, a,b-dideutero-N-dimethyltryptamine, a,a,b-trideutero-N-dimethyltryptamine, α,β,β-trideutero-N-dimethyltryptamine, and a,a,b,b-tetradeutero-N-dimethyltryptamine. Often, the DMT compound is N,N-dimethyltryptamine.

In some embodiments, ^R4 , ^R5 , and each YH are H, and each ^xH is independently selected from H and D. In these embodiments, the DMT compound is any compound or combination of N,N-dimethyltryptamine, a-monodeutero-N-dimethyltryptamine, and α,αdideutero-N-dimethyltryptamine.

Partially deuterated and deuterated N,N-dimethyltryptamine compounds can be synthesized by following the reaction schemes (synthetic schemes) shown in Schemes 1 and 2 below. The chemistry depicted in the schemes is described by P. E. Morris and C. Chiao (Journal of Labelled Compounds AndRadio

- 7 049106 pharmaceuticals, Vol. XXXIII, No. 6, 455-465 (1993)). Partially deuterated and deuterated N,N-dimethyltryptamine compounds can also be synthesized according to the synthesis scheme shown in Scheme 3.

Here, the terms a,a-dideutero-N-dimethyltryptamine compounds and a-protio,adeutero-N-dimethyltryptamine compounds are denoted as deuterated (or fully deuterated) N-dimethyltryptamine and partially deuterated N-dimethyltryptamine, respectively. Thus, a deuterated (or fully deuterated) N,N-dimethyltryptamine compound strictly refers to a XA-dimethyltryptamine compound in which both protons at position a are replaced by deuterium atoms. The term partially deuterated N,N-dimethyltryptamine compound strictly refers to an N,N-dimethyltryptamine compound in which one of the two protons at position a is replaced by deuterium atom. A deuterated N,N-dimethyltryptamine compound as used herein is any N,N-dimethyltryptamine compound substituted with two deuterium atoms at the a-position, and a partially deuterated N,N-dimethyltryptamine compound is any N,N-dimethyltryptamine compound with one hydrogen atom and one deuterium atom at the α-position.

If desired, compositions containing amounts of N,N-dimethyltryptamine and deuterated N,N-dimethyltryptamine compounds, with the relative proportions of N,N-dimethyltryptamine to deuterated N,N-dimethyltryptamine compounds and partially deuterated N,N-dimethyltryptamine compounds, can be controlled by varying the ratio of lithium aluminum hydride to lithium aluminum deuteride in the reducing agent. It should be understood that in such compositions, R ⁴ , R ⁵ and each YH is H, and each ^x H is independently selected from H and D, i.e., the DMT compound is any compound or combination of N,N-dimethyltryptamine, α-monodeuteroN,N-dimethyltryptamine and α,α-dideutero-N,N-dimethyltryptamine. The relative proportions may be further varied by adding one or more of N,N-dimethyltryptamine, α,αdideutero-N,N-dimethyltryptamine, and α,α,β,β-tetradeutero-N,N-dimethyltryptamine to the compositions described above.

Scheme 1. Synthetic route to partially deuterated N,N-dimethyltryptamine compounds

Scheme 2. Synthetic route to partially deuterated N,N-dimethyltryptamine compounds

- 8 049106

CifiH^nN^Oa

Mol. May.: 304.34

Scheme 3. Synthetic route to partially deuterated N,N-dimethyltryptamine compounds.

Identification of the compositions obtained in the reduction step of schemes 1 and 2 can, if desired, be achieved by chromatographic separation of the components of the mixtures by conventional means available to the skilled person, in combination with spectroscopic and/or mass spectrometric analysis.

Alternative compositions can be prepared by mixing N-dimethyltryptamine, prepared according to Scheme 1 or Scheme 2, when the reducing agent is lithium aluminum hydride exclusively, with a deuterated N-dimethyltryptamine compound, prepared according to Scheme 1 or Scheme 2, when the reducing agent is lithium aluminum deuteride exclusively.

The compositions described above may be further modified by adding one or more deuterated or partially deuterated N,N-dimethyltryptamine compounds. The starting products of such deuterated or partially deuterated N,N-dimethyltryptamine compounds may be obtained, for example, by the chromatographic separation described above.

In some embodiments, R ⁴ is acetoxy and R ⁵ is H, or R ⁵ is acetoxy and R ⁴ is H. According to some embodiments, R ⁴ is acetoxy and R ⁵ is H, such that the DMT compound is any compound or combination of 4-acetoxy-N-dimethyltryptamine, 4-acetoxy-a-monodeutero-N-dimethyltryptamine, and 4-acetoxy-a,a-dideutero-N-dimethyltryptamine. For example, the DMT compound is 4-acetoxy-N-dimethyltryptamine.

In some embodiments, R ⁴ is H and R ⁵ is methoxy, or R ⁵ is H and R ⁴ is methoxy. According to some embodiments, R ⁴ is H and R ⁵ is methoxy, such that the DMT compound is any compound or combination of 5-methoxy-N-dimethyltryptamine, 5-methoxy-a-monodeutero-N-dimethyltryptamine, and 5-methoxy-a,a-dideutero-N-dimethyltryptamine. For example, the DMT compound is 5-methoxy-N-dimethyltryptamine.

Scheme 4 shows art-known schemes for synthesizing DMT compounds in which the R ¹ substituent is hydrogen or the R ⁴ or R ⁵ substituent if different from hydrogen, as defined in formula I; each R ² is methyl, and HX refers to acids described herein with which the DMT compounds described herein can form salts.

- 9 049106

Scheme 4. Synthetic route to optionally substituted N,N-dimethyltryptamine compounds.

If desired, mixtures of compounds of formula I can be prepared containing controlled proportions of optionally ^R4- or ^R5- substituted DMT and the same optionally ^R4- or ^R5- substituted DMT, but by α-mono- and/or α,α-di-deuteration, by reducing 2-(3-indolyl)-I,L-dimethylacetamide with the desired ratio of lithium aluminum hydride and lithium aluminum deuteride.

For more detailed information on the synthesis of DMT compounds, see the Examples section of this document.

In some embodiments, the salt is an optionally substituted dimethyltryptamine compound and an acid selected from the group consisting of fumaric acid, tartaric acid, citric acid, acetic acid, lactic acid, and gluconic acid, typically fumaric acid.

Accordingly, salt may contain:

any compound or combination of N,N-dimethyltryptamine, a-monodeutero-I,L-dimethyltryptamine, a,a-dideutero-L,L-dimethyltryptamine, a,β-dideutero-L,L-dimethyltryptamine, α,α,β-trideutero-L,L-dimethyltryptamine, a,β,β-trideutero-L,L-dimethyltryptamine, and a,α,β,β-tetradeutero-L,L-dimethyltryptamine; or any compound or combination of 4-acetoxy-L,L-dimethyltryptamine, 4-acetoxy-a-monodeutero-L,L-dimethyltryptamine, and 4-acetoxy-a,α-dideutero-L,L-dimethyltryptamine; or any compound or combination of 5-methoxy-L,L-dimethyltryptamine, 5-methoxy-a-monodeutero-L,L-dimethyltryptamine and 5-methoxy-a,a-dideutero-L,L-dimethyltryptamine; and an acid selected from the group consisting of fumaric acid, tartaric acid, citric acid, acetic acid, lactic acid and gluconic acid, typically fumaric acid.

In some embodiments, the salt is DMT fumarate, meaning it contains DMT and fumaric acid.

The DMT compound can have a purity of about 80 to 100%. Sometimes the purity is about 90 to 100%, for example about 95 to 100%. Usually the DMT compound has a purity of about 99 to 100%, i.e., a purity greater than or equal to 99%. The purity percentages here are determined using HPLC.

It is particularly preferred to prepare the compositions of the present invention with a drug substance containing an optionally substituted DMT compound or a salt thereof with a purity of greater than 99%. By drug substance is meant, as understood in the art, an active ingredient intended to provide pharmacological activity or other direct action in the diagnosis, cure, amelioration, treatment or prevention of disease or to affect the structure or any function of the patient concerned, but does not include intermediates used in the synthesis of such an ingredient. It is understood that the drug substance may contain one or more such active ingredients.

Compositions prepared with less pure drug substance show higher levels of related substances, indicating a lower shelf life. Accordingly, preferred embodiments of any aspect of the present invention comprise a drug substance comprising an optionally substituted dimethyltryptamine compound or salt thereof having a purity greater than or equal to 99% as measured by HPLC. Particularly preferred embodiments comprise a drug substance comprising an optionally substituted

- 10 049106 a purified dimethyltryptamine compound or a salt thereof having a purity of greater than or equal to 99.5%, even more preferably 99.7%, and even more preferably 99.9%, as measured by HPLC. The concentration of the DMT compound in the composition may be any desired concentration, so long as the osmolality of the composition is from about 250 to about 350 mOsm/kg. The DMT compound may be at a concentration of from about 0.001 to about 28 mg/mL, such as from about 2.5 mg/mL to about 28 mg/mL. Accordingly, in some embodiments, the composition of the present invention comprises the DMT compound at a concentration of from 2.5 mg/mL to 28 mg/mL, including any integer value therein. A concentration of 28 mg/mL DMT provides approximately 148 mOsm/kg (approximately 296 mOsm/kg when counterions are taken into account). This allows an additional 54 mOsm/kg to be provided by other components of the formulation, such as buffer.

In some embodiments, the concentration of the DMT compound in the composition is about 2.5 mg/mL, which provides about 13.2 mOsm/kg (about 26.4 mOsm/kg when taking into account counterions).

As described above, the composition of the present invention has an osmolality of about 250 to about 350 mOsm/kg. As described above, the injectable composition may have an osmolality of about 250 to about 600 mOsm/kg. In some embodiments, the osmolality of the composition is about 250 to about 500 mOsm/kg or about 250 to about 400 mOsm/kg. In some embodiments, the osmolality of the composition of the present invention is about 275 to about 325 mOsm/kg, such as about 280 to about 310 mOsm/kg. Typically, the osmolality of the composition is about 295 to about 305 mOsm/kg. In some embodiments, the composition is isotonic with human serum.

Sometimes, the concentration of the optionally substituted DMT salt and the buffer in the composition provides the desired osmolality. Alternatively, the desired osmolality can be achieved by including one or more tonicity adjusting agents in the composition. Thus, in some embodiments, the composition further comprises a tonicity adjusting agent. A tonicity adjusting agent is defined herein as a chemical that, when included in a composition, increases the osmolality of the composition. As described above, osmolality is the amount of osmotically active particles (the number of solute particles) in 1 kg of solution. Thus, a chemical that acts as a solute when included in a composition falls within the definition of a tonicity adjusting agent.

If the composition further comprises a tonicity adjusting agent, the concentration of the tonicity adjusting agent depends on the concentration of other components in the composition, such as optionally substituted DMT and a buffer. For example, if the osmolality of the composition without the tonicity adjusting agent is about 60 mOsm/kg, at least about 190 mOsm/kg will be provided by the tonicity adjusting agent (e.g., 95 mM sodium chloride). Inclusion of a tonicity adjusting agent is often preferred in low concentration compositions suitable for intravenous administration, such as compositions containing about 2.5 mg/mL of the DMT compound. In higher concentration compositions, such as compositions containing the DMT compound at concentrations greater than about 5 mg/mL, the tonicity adjusting agent may be less preferred or absent.

M. F. Powell, T. Nguyen, and L. Baloian presented a review of excipients suitable for parenteral administration (administration not via the mouth or alimentary canal) in PDA J. Pharm. Sci. Technol., 52, 238–311 (1998). All soluble excipients listed in this review article that can be administered intravenously will contribute to osmolality when added to the formulation and thus can be considered tonicity enhancing agents.

In some embodiments, the tonicity adjusting agent is any one or a combination thereof selected from the group consisting of sodium chloride; potassium chloride; dextrose; glucose; mannitol; phosphoric acid; lactose; sorbitol; sucrose; a phosphate salt such as sodium phosphate or potassium phosphate; acetic acid; an acetate salt such as sodium acetate, potassium acetate or ammonium acetate; alanine; ethyl alcohol; citric acid; a citrate salt such as sodium citrate or potassium citrate; arginine; ascorbic acid; an ascorbate salt such as potassium ascorbate or sodium ascorbate; benzyl alcohol; calcium chloride; creatinine; edetic acid; an edetate salt such as sodium edetate or calcium edetate; glycine; glycerin; histidine; lactic acid; magnesium chloride; polyethylene glycol; propylene glycol; sodium bicarbonate; sodium hydroxide; hydrochloric acid; lactic acid; lactate salts such as potassium lactate or sodium lactate; tartaric acid and tartrate salts such as sodium tartrate or potassium tartrate.

Some of the tonicity adjusting agents listed above may be used to buffer the composition (e.g., acetate salt, acetic acid, citrate salt, citric acid, ascorbate salt, ascorbic acid, phosphate salt, phosphoric acid). For the avoidance of doubt, if one of the tonicity adjusting agents listed above is used as a buffer, it is also not a specified tonicity adjusting agent, i.e., if the composition

- 11 049106 position additionally contains a tonicity regulating agent, then said tonicity regulating agent differs from the buffer.

Often the tonicity adjusting agent is any one or combination of agents selected from the group consisting of sodium chloride, potassium chloride, dextrose, glucose, mannitol, lactose, sorbitol, and sucrose. Typically, the tonicity adjusting agent is sodium chloride.

In some embodiments, the composition comprises sodium chloride at a concentration of from about 120 mM to about 140 mM, such as from about 125 mM to about 135 mM. Sometimes, the concentration of sodium chloride in the composition is about 130 mM.

In some embodiments, the composition consists essentially of an optionally substituted DMT salt, a buffer, water, and optionally a tonicity adjusting agent. This means, for example, that the presence of additional components in the composition is permitted provided that the amounts of such additional components do not significantly adversely affect the essential characteristics of the composition. Given that the purpose of including an optionally substituted DMT salt, a buffer, water, and an optional tonicity adjusting agent in the composition is to obtain a pharmaceutical composition of optionally substituted DMT, optionally suitable for injection and stable for at least several weeks upon storage, it should be understood that the inclusion of components that significantly detrimentally affect the stability of the composition or its suitability for injection (e.g., its osmolality or pH) is excluded from the composition. On the other hand, it should be understood that the presence of any components that do not significantly adversely affect the stability of the composition or its suitability for injection is included. Such components include antioxidants and antimicrobial preservatives. For a review of pharmaceutical excipients and their properties, including those with antioxidant and antimicrobial properties, see P. P. J. Sheskey, W G Cook and C. G. Cable, Handbook of Pharmaceutical Excipients, Eighth Edition, Pharmaceutical Press, London 2017.

Antioxidants commonly used in aqueous injection compositions include ascorbic acid, citric acid, tartaric acid, sodium metabisulfite and thiol derivatives.

Antimicrobial preservatives commonly used in injectable formulations include methylparaben (methyl parahydroxybenzoate), ethylparaben (ethyl parahydroxybenzoate) and propylparaben (npropyl parahydroxybenzoate), benzoic acid, benzyl alcohol, chlorobutanol, phenol, and sodium benzoate.

In certain embodiments, the composition comprises a salt, a buffer, water, and optionally a tonicity agent, i.e., the presence of any other components is excluded.

Often the composition will have an oxygen content of less than 2 ppm, such as from 0.1 ppm to 2 ppm. A skilled person can determine the oxygen content of the composition using any suitable method known in the art, such as using a dissolved oxygen meter (e.g. the Jenway 970 Enterprise dissolved oxygen meter, available from Keison Products: http://www.keison.co.uk/products/jenway/970.pdf).

The composition can be stored in any suitable container. In some embodiments, in order to further reduce the degradation of the composition, the composition is stored in a container adapted to prevent ultraviolet light penetration, such as a dark glass bottle. In other cases, the container in which the composition is stored is not adapted (and can be, for example, made of transparent glass) to protect against ultraviolet radiation, optionally provided by secondary packaging (for example, packaging inside which a container containing the composition can be placed). Often, the container is airtight, and the composition is stored in an inert atmosphere, such as nitrogen or argon, typically nitrogen. The composition can be stored at room temperature, i.e., at a temperature of from about 20 to about 30 ° C, or at lower temperatures, for example, from about 2 to about 8 ° C. Alternatively, to further reduce the degradation of the composition, it can be stored in a freezer.

In terms of the second aspect, the present invention provides a kit suitable for preparing a composition according to the first aspect, said kit comprising a salt of a DMT compound optionally substituted with deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy, or at position 4 with monohydrogen phosphate; and a buffer that is separate from the salt.

A kit for obtaining a composition according to the first aspect is also proposed, comprising:

a first composition comprising a salt of a DMT compound optionally substituted with deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy, or at position 4 with monohydrogen phosphate; and a second composition comprising a buffer that is separate from the salt, wherein the first and second compositions are mixed with water and, optionally, a tonicity enhancing agent, and the resulting mixture forms the composition of the first aspect.

For the avoidance of doubt, embodiments relating to the optionally substituted DMT salt and the buffer of the first aspect of the invention as defined herein employ mu

- 12 049106 tatis mutandis to the second aspect. For example, the optionally substituted DMT salt of the kit may comprise a Bronsted acid having a pKa at 25°C of from about 3 to about 5, and the compound of formula I and/or the buffer may comprise an acetate salt and acetic acid.

The optionally substituted DMT salt in the kit may be a solid, such as a powder or crystals. To improve the disintegration of the optionally substituted DMT salt in solid form, the salt may be lyophilized (freeze-dried) before inclusion in the kit. Lyophilization of the salt involves freezing it in the presence of a solvent (usually water) and separating the solvent from the salt by sublimation.

The kit may further comprise a tonicity adjusting agent. When the kit further comprises a tonicity adjusting agent, the embodiments relating to the optional tonicity enhancing agent of the first aspect of the invention as defined herein apply mutatis mutandis to the second aspect. For example, the tonicity adjusting agent may be any one or a combination of agents selected from the group consisting of sodium chloride, potassium chloride, dextrose, glucose, mannitol, lactose, sorbitol and sucrose.

In terms of the third aspect, the present invention provides a method for preparing the pharmaceutical composition of the first aspect, which is typically a solution. The method comprises reacting an optionally substituted salt of DMT, a buffer, water and optionally a tonicity adjusting agent. For the avoidance of doubt, embodiments of the first aspect of the invention apply mutatis mutandis to the third aspect. For example, the salt may be DMT, the buffer may comprise acetic acid and an acetate salt, and/or sodium chloride may be used as the tonicity adjusting agent.

It should be understood that the reaction according to the method can be achieved in a variety of ways. Often, the optionally substituted DMT salt is dissolved in water to form a first solution, to which a buffer is added and dissolved to form a second solution. If a tonicity agent is used, it is often added and dissolved in the second solution.

In some embodiments, an aqueous solution of a buffer is reacted with a salt, wherein the aqueous solution has a pH of about 3.5 to about 6.5, such as a pH of about 3.75 to about 6.5. Sometimes, the aqueous solution has a pH of about 3.75 to about 5.75, such as a pH of about 3.75 to about 4.25. In some embodiments, the aqueous solution has a pH of about 4.0.

The optionally substituted DMT salt in the composition can be prepared by reacting optionally substituted DMT free base with an aqueous solution containing an amount of a buffer suitable for stabilizing the pH and acting as a counterion to the optionally substituted DMT upon protonation. Accordingly, the method of the invention can include reacting optionally substituted dimethyltryptamine free base with a buffer, water and, optionally, a tonicity adjusting agent.

In some embodiments, the method further comprises adjusting the pH of the solution resulting from the reaction. Since the pH of the solution resulting from the reaction is typically low, adjusting the pH often involves reacting the solution with a suitable base. A skilled artisan can evaluate which bases are suitable for adjusting the pH of the solution resulting from the reaction without risking decomposition of the optionally substituted DMT salt.

Often, the pH of the solution resulting from the reaction is adjusted with any solution selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, ammonium hydroxide, calcium hydroxide, and magnesium hydroxide. In some embodiments, the pH is adjusted with sodium hydroxide or potassium hydroxide.

As described above, to further improve the decomposition of the composition, it may be desirable to minimize the overall oxygen content in the container in which the composition is stored, wherein the oxygen content in the container is balanced between the composition and the headspace (if any) within the container. Accordingly, it may be desirable to store the composition in an inert atmosphere, such as by purging the headspace to reduce the oxygen content from about 20% typically present in air to less than, for example, 0.5%. Additionally or alternatively, in some embodiments, the method further comprises bubbling the solution obtained from the reaction with an inert gas, such as nitrogen or argon, typically nitrogen.

Thus, from the viewpoint of the fourth aspect, the present invention provides the use of a buffer for reducing the degradation of an injectable pharmaceutical composition of a salt of a dimethyltryptamine compound optionally substituted with deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy or at position 4 with monohydrogen phosphate.

For the avoidance of doubt, the embodiments of the first aspect of the invention apply mutatis mutandis to the fourth aspect. In particular, the embodiments of the first aspect relating to the buffer and the optionally substituted DMT salt apply mutatis mutandis to the fourth aspect. For example, the buffer according to the fourth aspect may comprise an acetate salt and acetic acid; phos

- 13 049106 a phosphate salt and phosphoric acid; a citrate salt and citric acid; an ascorbate salt and ascorbic acid; or a benzoate salt and benzoic acid; and/or an optionally substituted DMT salt according to the fourth aspect may comprise a Bronsted acid having a pKa at 25°C from about 3 to about 5.

As described above, DMT has a possible therapeutic role in the treatment of depression, obsessive-compulsive disorder and substance abuse disorders (S. A. Barker, 2018, supra). Thus, in terms of the fifth aspect, the present invention provides a composition according to the first aspect for use in therapy.

In terms of the sixth aspect, the present invention provides a composition according to the first aspect for use in a method for treating a mental or neurological disorder in a patient. Often, the mental or neurological disorder is selected from the group consisting of (i) obsessive-compulsive disorder, (ii) depressive disorder, (iii) anxiety disorder, (iv) substance abuse and (v) volitional disorder. Often, the disorder is selected from the group consisting of major depressive disorder, treatment-resistant major depressive disorder, postpartum depression, obsessive-compulsive disorder and an eating disorder such as compulsive eating disorder.

In terms of the seventh aspect, the present invention provides a method for treating a mental or neurological disorder, comprising administering to a patient in need thereof a composition according to the first aspect. The mental or neurological disorder may be any of those described in connection with the sixth aspect. For example, the disorder may be selected from the group consisting of major depressive disorder, treatment-resistant major depressive disorder, postpartum depression, obsessive-compulsive disorder and an eating disorder such as compulsive eating disorder.

For treating a disorder, the composition comprises an effective amount of a DMT compound, i.e. an amount sufficient to reduce or stop the rate of progression of the disorder, or to alleviate or cure the disorder and thus to obtain the desired therapeutic or inhibitory effect.

The composition is not necessarily suitable for injection, so therapeutic administration thereof typically involves injection of the composition.

The composition may be suitable for bolus injection, in which a discrete amount of the optionally substituted DMT salt is administered in a single injection, such that the concentration of DMT in the body is rapidly increased. Bolus injections are typically administered intravenously (directly into a vein), intramuscularly (into a muscle), intradermally (under the skin), or subcutaneously (into fatty tissue or skin).

Alternatively, the composition may be suitable for inhalation, preferably in the form of an aerosol, such as a nasal spray.

Each reference referenced by this document is hereby incorporated by reference in its entirety, as if the entire contents of each reference were set forth herein in its entirety.

The invention can be further understood by reference to the following non-limiting claims and the examples that follow them:

1. A pharmaceutical composition, optionally suitable for injection, comprising a salt of a dimethyltryptamine compound optionally substituted with deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy or at position 4 with monohydrogen phosphate; a buffer that is separate from the salt; and water, wherein the composition has a pH of from about 3.5 to about 6.5 and an osmolality of from about 250 to about 350 mOsm/kg.

2. The composition according to claim 1, characterized in that the pH is from about 3.75 to about 6.5.

3. The composition according to claim 1, characterized in that the pH is from about 3.75 to about 5.75.

4. The composition according to claim 1, characterized in that the pH is from about 3.75 to about 4.25.

5. The composition according to claim 1, characterized in that the pH is from about 3.75 to about 4.0.

6. The composition according to any one of claims 1-5, characterized in that the composition has an osmolality of from about 275 to about 325 mOsm/kg.

7. The composition according to any one of claims 1-5, characterized in that the composition has an osmolality of from about 280 to about 310 mOsm/kg.

8. The composition according to any one of claims 1-5, characterized in that the composition has an osmolality of from about 295 to about 305 mOsm/kg.

9. A composition according to any one of claims 1 to 8, characterized in that the dimethyltryptamine compound is optionally substituted at position 5 with methoxy or at position 4 with acetoxy or monohydrogen phosphate.

10. A composition according to any one of claims 1 to 9, characterized in that the dimethyltryptamine compound is optionally substituted with deuterium at one or more positions selected from carbon atoms α, β and dimethyl.

11. A composition according to any one of paragraphs 1-9, characterized in that the dimethyltryptamine compound

- 14 049106 is optionally substituted with deuterium at one or more positions selected from carbon atoms α and β.

12. A composition according to any one of claims 1 to 9, characterized in that the dimethyltryptamine compound is optionally substituted with deuterium once or twice at the α-carbon atom.

13. A composition according to any one of claims 1 to 8, characterized in that the salt comprises a Bronsted acid having a pKa of from about 3 to about 5, and a compound of formula I

Formula I wherein R ⁴ and R ⁵ are both H, and each ^x H and each YH are independently selected from H and D, or one of R ⁴ and R ⁵ is H and the other is acetoxy or methoxy, each YH is H, and each ^x H is independently selected from H and D, or the salt comprises a compound of formula I wherein R ⁴ is monohydrogen phosphate, R ⁵ is H, and each YH and each ^x H is H.

14. The composition according to claim 13, characterized in that R ⁴ and R ⁵ both represent H.

15. The composition according to claim 14, characterized in that each YH is H, and each ^x H is independently selected from H and D.

16. The composition according to claim 13, characterized in that R ⁴ is acetoxy, and R ⁵ is H.

17. The composition according to claim 13, characterized in that R ⁴ is H, and R ⁵ is methoxy.

18. The composition according to any one of claims 1-14, characterized in that the optionally substituted dimethyltryptamine compound is dimethyltryptamine.

19. A composition according to any one of claims 1 to 18, wherein the salt is an optionally substituted dimethyltryptamine compound and an acid selected from the group consisting of fumaric acid, tartaric acid, citric acid, acetic acid, lactic acid and gluconic acid.

20. The composition according to claim 19, characterized in that the acid is fumaric acid.

21. The composition according to any one of claims 1 to 20, characterized in that the optionally substituted dimethyltryptamine compound is more than 99% pure according to HPLC.

22. The composition of any one of claims 1-21, wherein the optionally substituted dimethyltryptamine compound is in a concentration of from about 0.001 to about 28 mg/ml.

23. The composition of any one of claims 1-22, wherein the optionally substituted dimethyltryptamine compound is in a concentration of from about 2.5 to about 28 mg/ml.

24. The composition according to any one of claims 1-23, characterized in that the concentration of the optionally substituted dimethyltryptamine compound is about 2.5 mg/ml.

25. A composition according to any one of claims 1 to 24, characterized in that the buffer often comprises an acetate salt and acetic acid; a phosphate salt and phosphoric acid; a nitrate salt and citric acid; an ascorbate salt and ascorbic acid; a benzoate salt and benzoic acid; an oxalate salt and oxalic acid; or a formate salt and formic acid.

26. A composition according to any one of claims 1 to 24, wherein the buffer often comprises an acetate salt and acetic acid; a phosphate salt and phosphoric acid; a nitrate salt and citric acid; an ascorbate salt and ascorbic acid; or a benzoate salt and benzoic acid.

27. A composition according to any one of paragraphs 1-24, characterized in that the buffer contains an acetate salt and acetic acid.

28. The composition according to claim 27, characterized in that the buffer contains sodium acetate and acetic acid or potassium acetate and acetic acid.

29. The composition according to any one of claims 1-28, characterized in that the composition contains a buffer at a concentration of from about 15 mM to about 75 mM.

30. The composition according to claim 29, characterized in that the concentration of the buffer is from about 20 mM to about 30 mM.

31. The composition according to claim 29, characterized in that the buffer concentration is approximately 25 mM.

32. A composition according to any one of paragraphs 1-31, characterized in that the composition additionally contains an agent that regulates tonicity.

33. A composition according to any one of paragraphs 1-32, characterized in that the composition consists essentially of

- 15 049106 salt, buffer, water and, optionally, a tonicity adjusting agent.

34. A composition according to any one of claims 1 to 32, characterized in that the composition consists of a salt, a buffer, water and, optionally, a tonicity adjusting agent.

35. A composition according to any one of paragraphs 32-34, characterized in that the tonicity regulating agent is sodium chloride.

36. The composition according to claim 35, characterized in that the composition contains sodium chloride in a concentration of from about 120 mM to about 140 mM.

37. The composition according to claim 35, characterized in that the concentration of sodium chloride is from about 125 mM to about 135 mM.

38. The composition according to claim 35, characterized in that the concentration of sodium chloride is approximately 135 mM.

39. A composition according to any one of claims 1 to 38, having an oxygen content of less than 2 ppm.

40. The composition according to claim 39, having an oxygen content of 0.1 to 2 ppm.

41. A composition according to any one of claims 1 to 40, stored in a container adapted to prevent penetration of ultraviolet light.

42. The composition according to item 41, characterized in that the container is a bottle made of amber-colored glass.

43. A kit suitable for preparing a composition according to any one of claims 1 to 42, wherein said kit comprises a salt of a dimethyltryptamine compound optionally substituted with deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy, or at position 4 with monohydrogen phosphate; and a buffer that is separate from the salt.

44. A method for preparing a pharmaceutical composition according to any one of claims 1-42, comprising reacting a salt, a buffer, water and, optionally, a tonicity adjusting agent.

45. The method according to claim 44, characterized in that the aqueous solution of the buffer interacts with the salt, wherein the pH of the aqueous solution has the value specified in any of claims 1-5.

46. The method according to claim 44 or 45, characterized in that the method comprises reacting optionally substituted dimethyltryptamine in free base form with a buffer, water and, optionally, a tonicity adjusting agent.

47. The method according to any one of paragraphs 44-46, further comprising adjusting the pH of the solution obtained as a result of the interaction.

48. The method according to claim 47, characterized in that the pH is adjusted with sodium hydroxide or potassium hydroxide.

49. The method according to any one of paragraphs 44-48, further comprising bubbling the solution obtained as a result of interaction with an inert gas.

50. The method according to paragraph 49, characterized in that the inert gas is nitrogen.

51. Use of a buffer to reduce degradation of an injectable pharmaceutical composition of a dimethyltryptamine salt optionally substituted with deuterium and optionally substituted at position 4 or 5 with acetoxy or methoxy or at position 4 with monohydrogen phosphate.

52. The use according to paragraph 51, characterized in that the salt corresponds to the definition in any of paragraphs 1324.

53. A composition according to any one of claims 1-42 or a kit according to claim 43 for use in therapy

54. The composition defined in any one of claims 1-42, or the kit according to claim 43, for use in a method of treating a mental or neurological disorder in a patient.

55. A composition for use according to claim 54, wherein the mental or neurological disorder is selected from the group consisting of (i) obsessive-compulsive disorder, (ii) depressive disorder, (iii) anxiety disorder, (iv) substance abuse and (v) volitional disorder.

56. A composition for use according to claim 55, wherein the disorder is major depressive disorder.

57. A composition for use according to claim 55, wherein the disorder is treatment-resistant major depressive disorder.

58. A composition for use according to claim 55, wherein the disorder is postpartum depression.

59. A composition for use according to claim 55, wherein the disorder is an obsessive-compulsive disorder.

60. A composition for use according to claim 55, wherein the disorder is an eating disorder.

61. A composition for use according to claim 60, wherein the eating disorder is a compulsive eating disorder.

62. A method for treating a mental or neurological disorder comprising administering to a patient in need thereof a composition as defined in any one of claims 1-42.

63. The method according to claim 62, wherein the mental or neurological disorder corresponds to the op

- 16 049106 definition in any of paragraphs 55-61.

Examples

Example 1.

220.9 g of N,N-DMT (as the free base) were obtained as N,N-DMT fumarate using the chemistry depicted in Scheme 3 above. An additional 4-6 g of the six partially deuterated mixtures were also obtained using modified conditions.

In Scheme 3, a carbodiimide coupling agent EDC.HCl and an additive coupling agent (which enhances the reactivity of the coupling agent) HOBt are used. More generally, a combination of two or more coupling agents comprises an agent selected from (i) a phosphonium coupling agent and a carbodiimide coupling agent selected from DCC, EDC and DIC; and (ii) an additive coupling agent selected from HOBt, HOOBt, HOSu, HOAt, ethyl 2-cyano-2-(hydroxyimino)acetate and DMAP. Often, as shown below, EDC is used, preferably in the form of the HCl salt. Often, as shown below, the additive coupling agent is HOBt. Often, as shown below, EDC is used, preferably in the form of the HCl salt in combination with the additive coupling agent HOBt.

Stage 1: combination of indole-3-acetic acid and dimethylamine

In a 5 L vessel under N ₂ , indole-3-acetic acid (257.0 g, 1.467 mol), hydroxybenzotriazole (HOBt, ~20% wet) (297.3 g, 1.760 mol), and dichloromethane (2313 mL) were charged to give a milky white suspension. 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC.HCl, 337.5 g, 1.760 mol) was then charged portionwise over 5 min at 16-22 °C. The reaction mixture was stirred for 2 h at ambient temperature, after which 2 M dimethylamine in THF (1100 mL, 2.200 mol) was charged dropwise over 20 min at 20-30 °C. The resulting solution was stirred at ambient temperature for 1 h, where HPLC showed 1.1% indole-3-acetic acid and 98.1% of the desired product (designated as step 1). Then 10% K2CO3 (1285 mL) was added to the reaction mixture and stirred for 5 min. The layers were separated and the upper aqueous layer was extracted with dichloromethane (643 mL x 2). The organic extracts were combined and washed with brine (643 mL). The organic extracts were then dried over _MgSO4 , filtered and concentrated in vacuo at 45 °C. This yielded 303.1 g of the crude product of step 1 as an off-white sticky solid. The crude material was then suspended in tert-butyl methyl ether (TBME, 2570 mL) at 50°C for 2 h before cooling to ambient temperature, filtering and washing with TBME (514 mL x 2). The filter cake was then dried in vacuo at 50°C to give stage 1,266.2 g (yield = 90%) as an off-white solid with a purity of 98.5% by HPLC and >95% by NMR.

Stage 2: Receiving DMT.

In a 5 L vessel under nitrogen atmosphere, stage 1 (272.5 g, 1.347 mol) and tetrahydrofuran (THF, 1363 mL) were charged to give an off-white suspension. Then, 2.4 M LiAlH4 in THF (505.3 mL, 1.213 mol) was added dropwise over 35 min at 20-56 °C to give an amber solution. The solution was heated to 60 °C for 2 h, at which time HPLC showed stage 1 ND, desired product designated stage 2, 92.5%), impurity 1 (2.6%), impurity 2 (1.9%). The complete reaction mixture was cooled to ambient temperature and then added dropwise to a solution of 25% Rochelle salt (aq) (2725 mL) over 30 min at 20-30 °C. The resulting milky white suspension was stirred at 20-25 °C for 1 h, after which the layers were separated and the upper organic layer was washed with brine (681 mL). The organic layer was then dried over MgSO4, filtered and concentrated in vacuo at 45 °C. The resulting crude oil was azeotroped from ethanol (545 mL x 2). This gave 234.6 g (yield = 92%) of the step 2 product with a purity of 95.0% by HPLC and >95% by NMR.

Step 3a (i)-(iii): preparation of seed crystals of DMT fumarate.

(i) The product from step 2 (100 mg) was taken up in 8 volumes of isopropyl acetate and heated to 50°C before charging fumaric acid (1 equivalent) as a solution in ethanol. The flask was then left to mature at 50°C for 1 h before being cooled to room temperature and stirred overnight to give a white suspension. The solids were isolated by filtration and dried for 4 h at 50°C to give 161 mg of product (>99% yield). The purity was determined to be 99.5% by HPLC and >95% by NMR.

(ii) When isopropyl acetate was replaced by isopropyl alcohol in method (i), a white suspension was obtained after stirring overnight. The solids were isolated by filtration and dried for 4 h at 50°C to give 168 mg of product (>99% yield). The purity was determined to be 99.8% by HPLC and >95% by NMR.

When isopropyl acetate was replaced by tetrahydrofuran in method (i), a white suspension was obtained after stirring overnight. The solids were isolated by filtration and dried for 4 h at 50 °C to give 161 mg of product (>99% yield). The purity by HPLC was determined to be 99.4% and by NMR to be >95%.

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Powder X-ray diffraction analysis showed that the products from each of the methods 9i) to (iii) were the same, which was designated as Sample A.

Stage 3b: Production of DMT fumarate

A 5 L flanged flask under nitrogen was charged with fumaric acid (152.7 g, 1.315 mol) and the product of Step 2 (248.2 g, 1.315 mol) as a solution in ethanol (2928 mL). The mixture was heated to 75 °C to give a dark brown solution. The solution was filtered into a preheated (80 °C) 5 L jacketed vessel. The solution was then cooled to 70 °C and seeded with Sample A (0.1 wt %), the seeding being allowed to mature for 30 min before cooling to 0 °C at a rate of 5 °C/h. After stirring for an additional 4 h at 0 °C, the mixture was filtered and washed with cold ethanol (496 mL x 2) and then dried at 50 °C overnight. 312.4 g (yield=78%) of the product from Step 3 were obtained with a purity of 99.9% by HPLC and >95% by NMR. XRPD: Sample A.

5-Methoxy-DMT fumarate was prepared similarly to DMT fumarate described immediately above, except for the use of 5-methoxyindole-3-acetic acid.

Synthesis of deuterated mixtures of DMT compounds.

A modified step 2 synthesis using LiAlH4/LiAlD4 solid mixtures was used, using 1.8 equivalents of LiAlH4/LiAlD4 compared to 0.9 equivalents using the process described above for non-deuterated DMT.

Six deuteration reactions were carried out.

An example of the synthesis of a deuterated mixture (using 1:1 LiAlH4:LiAlD4) of DMT compounds:

A 250 mL three-neck flask under nitrogen was charged with LiAlH4 (1.013 g, 26.7 mmol), LiAlD4 (1.120 g, 26.7 mmol), and THF (100 mL). The resulting suspension was stirred for 30 min, after which the product of step 1 (6 g, 29.666 mmol) was charged portionwise over 15 min at 20-40 °C. The reaction mixture was then heated at reflux (66 °C) for 2 h, at which time HPLC showed no product of step 1 remaining. The mixture was cooled to 0 °C and quenched with 25% Rochelle salt (aq) (120 mL) for 30 min at <30 °C. The resulting milky suspension was stirred for 1 h and then allowed to separate. The lower aqueous layer was removed and the upper organic layer was washed with brine (30 mL). The organic layers were then dried over _MgSO4 , filtered and concentrated in vacuo. This yielded 4.3 g of crude material. The crude product was then taken up in ethanol (52 mL) and fumaric acid (2.66 g, 22.917 mmol) was added before heating to 75 °C. The resulting solution was allowed to cool to ambient temperature overnight before further cooling to 0-5 °C for 1 h. The solids were isolated by filtration and washed with cold ethanol (6.5 mL x 2). The filter cake was dried at 50 °C overnight to yield 5.7 g (yield = 63%) of product with a purity of 99.9% by HPLC and >95% by NMR.

Evaluation of the degree of deuteration.

This was achieved using LCMS-SIM (SIM = individual ion monitoring), whereby the analysis result is a separate ion count for each mass of the three deuterated N,N-dimethyltryptamine compounds (N,N-dimethyltryptamine (D0), a-deutero-NM-dimethyltryptamine (D1) and a,a-dideutero-N,N-dimethyltryptamine (D2)) based on the retention time for N,N-dimethyltryptamine. From these ion counts the percentage of each component was then calculated.

For example, %D0=[D0/(D0+D1+D2)]x 100.

HPLC parameters.

System: Agilent 1100/1200 series liquid chromatograph or equivalent.

Column: Triart Phenyl; 150 x 4.6 mm, particle size 3.0 µm (Ex: YMC, Part number: TPH12S031546PTH).

Mobile phase A: Water : Trifluoroacetic acid (100:0.05%) Mobile phase B: Acetonitrile

:Trifluoroacetic acid (100:0.05%) Gradient: Time %A %IN 0 95 5 13 62 38 26 5 95 30.5 5 95 31 95 5

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Flow rate: 1.0 ml/min Stop time: 31 minutes Duration after completion: 4 minutes Volume of administration: 5 µl Vial washing: BUT Column temperature: 30°C in total Wavelength: 200 nm, (4 nm) Standard: BUT

Mass spectrometry parameters

System: Agilent 6100 Series Quadrupole LC/MS or equivalent

Gas flow- 12.0 l/min Temp, gas- 350°С dehumidifier: dehumidifier Pressure 35 psig spray: Fragmenter: BY Reinforcement: 1,00 Connection RT RRT Conc Thinner Detection mass D0 10.64 1.00 0.30 mg/ml SNzSTSNgO (50:50) (+)SIM 189.10 m/z D1 10.64 1.00 0.30 mg/ml SNzSTSNgO (50:50) (+) SIM 190,10 m/z D2 10.64 1.00 0.30 mg/ml SNzSTSNgO (50:50) (+) SIM 191.10 m/z

MS-SIM range - target mass ±0.1 m/z

Data for the six deuteration reactions are presented in Table A below:

Mixture No. (Ratio LiAlH ₄ : LiAlD4) Loading (stage 1) Receiving, stage 3 (exit) HPLC purity NMR purity % Deuteration Do Di D ₂ 1 (SPL028) (0:1) 5g 5.3g (65%) 99.7% >95% 0.7% 2.7% 96.6% 2(1:1) 6g 5,699g (63%) 99.9% >95% 30.0% 48.3% 21.7% 3(1:2) 5g 4,206g (52%) 99.9% >95% 16.5% 46.8% 36.8% 4(1:3) 5g 5,558g (68% 99.8% >95% 9.3% 41.5% 49.2% 5(2:1) 5g 4,218g (52%) 99.9% >95% 47.5% 41.3% 11.2% 6(3:1) 5g 5.0g (62%) 99.4% >95% 57.5% 35.3% 7.4%

For the synthesis of 5-methoxy-N,N-dimethyltryptamine or 4-methoxy-N,N-dimethyltryptamine, 3-indoleacetic acid (see Scheme 3) can be replaced by 5-methoxyindole-3-acetic acid (see the synthesis of a,a-dideutero-5-methoxydimethyltryptamine described below) or 4-methoxyindole-3-acetic acid, respectively, both of which are commercially available (for 5-methoxyindole-3-acetic acid, e.g. from Sigma-Aldrich (code M14935-1G), for 4-methoxyindole-3-acetic acid see, e.g., Aaron Chemicals (code AR00VTP1)).

5-methoxy-N-dimethyltryptamine (see Sigma-Aldrich code M-168-1ML), 4-methoxy-N-dimethyltryptamine (see Cayman Chemical code 9000895), 4-acetoxy-N-dimethyltryptamine (see Cayman Chemical code 14056), and 3-[2-(dimethylamino)ethyl]-N-indol-4-yl phosphate (psilocybin, see Sigma-Aldrich CAS number 520-52-5) are also commercially available.

Synthesis of a,a-dideutero-5-methoxydimethyltryptamine step 1.

To a 100 mL three-neck flask under nitrogen atmosphere were charged 5-methoxyindole-3-acetic acid (3.978 g, 19.385 mmol), HOBt (--20% humidity) (3.927 g, 23.261 mmol), and DCM (40 mL). EDC.HCl (4.459 g, 23.261 mmol) was then added portionwise over 15 min at <30 °C. The reaction mixture was stirred at ambient temperature for 1 h, and then 2 M dimethylamine (14.54 mL, 29.078 mmol) was added dropwise over 15 min at <25 °C. After stirring for 1 h, HPLC showed no starting material remaining. The reaction mixture was then treated with 10% _K2CO3 (20 mL), stirred for 5 min, and allowed to separate. The lower aqueous layer was removed and re-extracted with DCM (10 _mL x 2). The organic extracts were combined, washed with brine (10 mL), then dried over _MgSO4 and filtered. The filtrate was concentrated in vacuo at 45 °C to give 3.898 g of active product (yield = 87%) with a purity of 95.7% by HPLC.

Stage 2.

The methoxy derivative of step 1 (3.85 g,

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16.586 mmol) and THF (19.25 mL). Then 2.4 M LiAlD ₄ in THF (6.22 mL, 14.927 mmol) was added dropwise over 30 min at <40 °C. The reaction mixture was heated to 60 °C for 1 h, at which time HPLC showed that 0.1% of starting material remained. The reaction mixture was then cooled to ambient temperature and quenched with 25% Rochelle salt (38.5 mL) dropwise over 30 min at <30 °C. The resulting suspension was stirred for 1 h and then allowed to separate. The lower aqueous layer was then removed and the upper organic layer was washed with brine (9.6 mL). The organic layers were then dried over _MgSO4 , filtered and concentrated in vacuo before azeotroping with EtOH (10 mL x 2). This gave 3.196 g of active product (yield = 88%) with a purity of 91.5% by HPLC.

Stage 3.

A 50 mL three-necked flask under nitrogen was charged with fumaric acid (1.675 g, 14.430 mmol) and a solution of the methoxy derivative of step 2 (3.15 g, 14.299 mmol) in EtOH (37.8 mL). The mixture was then heated to 75 °C for 1 h, which did not produce a solution as expected, the mixture was further heated to reflux (78 °C), which still did not produce a solution. Therefore, the suspension was cooled to 0-5 °C, filtered and washed with EtOH (8 mL x 2) before drying at 50 °C overnight. This yielded 3.165 g (yield = 65%) of material with a purity of 99.9% by HPLC.

Development of composition.

A stable formulation isotonic with human serum and suitable for intravenous (IV) bolus administration of DMT fumarate was developed. A suitable method for preparing such a formulation containing DMT fumarate at a concentration of 2.5 mg/mL was also developed. These formulations were prepared and placed under accelerated storage to evaluate stability over several weeks.

All concentrations given below are expressed as free base (i.e. in the absence of the fumarate counterion). To achieve this, a correction factor of 1.59 was applied to the specific batch of drug substance at delivery.

Details of the experiment.

Initial tests.

The solubility of DMT fumarate was assessed at a concentration of 10 mg/mL in a small range of aqueous solvents (water, saline, 20 mM phosphate buffer, and a combination of buffer and saline).

Phosphate buffer (100 ml) was prepared using 219.53 mg of the dibasic form [HPO ₄ ][Na] ₂ with 183.7 mg of the monobasic form [H ₂ PO ₄ ]Na, in both cases the dihydrate salts. The solution was adjusted to pH 7.0 with NaOH (1 M) and then made up to volume. 10 ml of the 10 mg/ml formulation were prepared.

First, a phosphate buffer in combination with saline (20 mM phosphate buffer in 0.45% w/v saline) was tested as a good starting point for obtaining a physiologically acceptable formulation without solubility problems. For its preparation, sodium chloride was first dissolved in water to obtain saline (100 ml, 0.45% w/v). Phosphate salts in the amounts described above were then dissolved in saline and the pH was adjusted with NaOH (1 M).

DMT fumarate was readily soluble in each aqueous solvent. Each solution had a clear beige appearance, which was removed by filtration (using 0.2 µm filters) to yield a clear, colorless solution. The pH of these solutions was in the range of 3-4.

Buffer strength at 30 and 50 mM (as phosphate buffer, pH 7.4, prepared in 0.45% w/v sodium chloride) was tested to evaluate the effect of the buffer on pH control of formulations containing 2 or 2.5 mg/mL DMT fumarate. This range of buffer strengths was chosen to determine the required buffer strength to fix the pH of the formulation at approximately pH 7.4. When formulating injectable formulations, the pH of the formulation is typically matched to the pH of the patient's serum. Human serum has a pH of approximately 7.4. Buffers were prepared as follows. Saline was prepared by dissolving 9 g sodium chloride in 2 L water. Phosphate salts (e.g. 30 mM = dibasic dihydrate (4.29 g), monobasic dihydrate (1.43 g), 50 mM = dibasic dihydrate (7.28 g), monobasic dihydrate (2.25 g)) were dissolved in saline, the pH was adjusted to 7.4 using NaOH (1 M). 9 g NaCl per 2 L of water. The pH was adjusted to pH 7.4 with 1 M NaOH. The initial pH of each solution after preparation was less than pH 7.4. At 20 mM, the initial pH of 5.9 continued to decrease when the solution was stored overnight in the laboratory, indicating that the buffering capacity of the buffer at 20 mM was insufficient. At both 30 mM and 50 mM buffer concentrations, the initial pH values were > 6.5 and remained stable.

Short-term stability was assessed and the data obtained for pH, osmolality and quantification are presented in Tables 1 and 2. The data in Table 2 were obtained with the formulations stored at 40 to 50°C.

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Table 1

Evaluation of short-term stability of the composition

Sample pH Osmolality (mOsm/kg) Quantitative determination (mg/ml) Original 24 h Day 5 Day 7 Original 24 h Day 5 Day 7 Original 24 h Day 5 Day 7 2 mg.ml'UOmM buffer/light ^a 6.74 6.74 - 6.71 239 238 - 244 2,00 2.02 - 2.09 2 mg/ml UZOmM buffer/ ^darkness 6.74 6.73 - 6.72 239 235 - 253 - 1.99 - 2.05 2 mg.ml’UOmM buffer/2-8°C 6.74 6.73 - 6.72 239 238 - 237 1.99 1.96 - 2.09 2 mg.ml ^-1 /50mM buffer/light ^a 6.95 6.96 - 6.95 285 284 - 289 1.95 1.99 - 2.04 2 mg.ml ^-1 /50mM buffer/ ^darkness 6.85 6.98 - 6.95 285 285 - 286 - - - 2.04 2 mg.ml ^-1 /50mM buffer/2-8°C 6.95 6.97 - 6.95 285 284 - 283 1.98 1.98 - 2.08 2.5 mg.ml U50mM buffer/light ^a 6.87 - 6.86 - 288 - 286 - 2.46 - 2.51 -

2.5 mg.ml V50mM buffer/ ^darkness 6.87 - 6.86 - 288 - 287 - 2.43 - 2.60 - 2.5 mg.ml U50mM buffer/2-8°C 6.87 - 6.86 - 288 - 288 - - - 2.57 - ^aЬ Light and darkness at laboratory storage temperature (15-25°C)

Table 2

Evaluation of short-term stability of the composition

Sample pH Quantitative determination (mg/ml) Related substances (%) Original Day 7 Original Day 7 Original Day 7 2.5 mg/ml/50mM buffer 6.88 6.87 2.49 2.38 N.O. <0.02 1,13 2.5 mg/ml/50mM buffer (Ni bubbled) 6.88 6.87 2.49 2.55 N.O. <0.02 N.O. <0.02 2.5 mg/ml/50mM buffer (28°C) 6.88 6.89 2.49 2.53 N.O. <0.02 N.O. <0.02 2.5 mg/ml/50 mM buffer (UV exposure) 6.83 - 2,10 - 3.57 - 2.5 mg/ml/50 mM buffer (control of UV exposure) 6.84 - 2.50 - N.O. <0.02 -

Notably, the preferred buffers stored under ambient conditions (1 week at 40°C), without N2 sparging or UV exposure control, contained 1.13% congeners after 1 week of storage. This was compared to the congeners formed under the same conditions for the Britton-Robinson buffer formulations below.

Development of composition.

Materials.

Details of DMT fumarate used for stability are presented in Table 3, and the excipients used are listed in Table 4.

Table 3

DMT fumarate used for stability studies

Material Batch No. Supplier DMT Fumarate SPL026 Onyx Scientific, Sunderland

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Table 4

Excipients used for formulation development study

Material Batch No. Supplier Purified water Not standardized Elga dispenser, article number ARC37642 Sodium chloride 17D194102 VWR disodium hydrogen orthophosphate dihydrate 1997160 Fisher Chemicals Sodium dihydrogen orthophosphate dihydrate 1724808 Fisher Chemicals 1M sodium hydroxide solution by volume 726144 Scientific Laboratory Supplies Glacial acetic acid 1727841 Fisher Chemicals

Equipment.

The equipment, excluding standard laboratory glassware, used during the studies are listed in Table 5. Calibration and verification of the equipment was performed in accordance with standard operating procedures for all measurements as required.

Table 5

Typical equipment used during formulation development research

Item Manufacturer and model Article Scales Mettler Toledo, МХ5 32721 Scales Sartorius, ME215S 31476 Single mixer Bibby HB502 20234 pH meter Mettler Toledo, MP225 20322 Osmolality Advanced Instruments Osmo 1 38564 Filters Millex MP PES 0.22 pm But Light box Heraeus SunTest 28 694

Osmolality readings.

Osmolality readings were obtained using an Advanced Instruments Osmo 1. A single sample syringe was used to introduce the sample into the osmometer, which utilizes industry-preferred freezing point depression principles to accurately and precisely determine osmolality.

The instrument was verified using 50, 850 and 2000 mOsm/kg H2O calibration standards prior to analysis to confirm accuracy.

pH readings.

pH readings were obtained using a Mettler Toledo MP225 pH meter. The probe electrode was placed in the test solutions in a glass vial with brief stirring at ambient temperature.

The instrument was verified before and after each use using supplied pH buffer solutions ranging from 1.68 to 10.01 to confirm accuracy.

High Performance Liquid Chromatography (HPLC)

The following HPLC parameters were used to evaluate the quantitative content and amount of congeners (substances resulting from the degradation of DMT fumarate) in DMT fumarate solutions that were prepared as part of the formulation development.

Column:

Mobile phase A:

Mobile phase B:

Diluent:

YMC-Triart Phenyl; 150 x 4.6 mm, 3 µm, Water:Trifluoroacetic acid (100:0.05 v/v) Acetonitrile:Trifluoroacetic acid (100:0.05 v/v)

Acetonitrile:Water (50:50)

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Gradient graph:

Time (min) %A %IN 0,0 95 5 13,0 62 38 26,0 5 95 30,5 5 95 31,0 95 5

Flow rate: Column temperature: Injection volume: 1.0 ml.min ¹ zo°c 7.5 µl Needle flush: Seal flush: Water: Acetonitrile (50:50) Water: Acetonitrile (50:50) Analysis time: 35 minutes Detection wavelength: 220 nm

Development of composition.

The solubility of DMT fumarate was initially assessed over a range of different pH values, from pH 4 to pH 10. Then, formulations were prepared with a target concentration of 2.5 mg/mL DMT fumarate over a pH range from pH 4 to pH 9.

Solubility of DMT fumarate at different pH values.

Seven solutions, each containing a concentration of 20 mg/mL DMT fumarate, were prepared in Britton-Robinson (BR) buffer. Once DMT fumarate was dissolved in each test formulation (DMT fumarate was very soluble and only agitation and shaking were required in each), the pH of each test formulation was then adjusted to pH 4, 5, 6, 7, 8, and 9 using sodium hydroxide solution.

The solubility of 20 mg/mL DMT fumarate was confirmed at pH 4, 5, 6, and 7, and these solutions were clear and colorless. The pH 8 sample was turbid, and the pH 9 and pH 10 samples contained sediment. After overnight storage at ambient conditions, the pH of each solution was measured and the results showed no change from the initial pH values. Each sample was then filtered and analyzed for content. Each solution, including the high pH solutions that contained sediment, contained approximately the same content of DMT fumarate.

pH stability.

The pH stability of DMT fumarate at a concentration of 2.5 mg/mL was assessed in 40 mM Britton-Robinson buffer over a buffer pH range of 4 to 9 (nominal). The pH of each formulation was measured upon preparation, after 7 days of storage at 40°C, and then after further storage for an additional 3 days at 40°C and 7 days at 50°C (for a total further storage of 10 days). The formulations were analyzed for content (quantitation) and related substances upon preparation and then after 7 and 17 days of storage.

Two additional aliquots of the pH 7 (nominal) solution were taken for further testing, one sparged with nitrogen and the other exposed to intense ultraviolet light for 4 hours equivalent to 1 ICH unit (200 watt-hours UVR, 0.6 million lux-hours).

During the preparation of each formulation, a drop in pH was observed in the range of 0.14 units (formulation with pH 4) to 1.29 units (formulation with pH 9), which is due to the acidic nature of the drug substance. After preparation, the pH of each formulation remained stable for the two subsequent stability time points (Table 6).

The concentration of DMT fumarate was determined by HPLC during preparation and at two stability determination points (Table 7). All results confirmed the correctness of the preparation with no significant changes at either day 7 or day 17. The only change that occurred during the experiment was a drop in concentration after light stress of an aliquot of the formulation with normal pH 7. This was accompanied by a significant increase in the observed degradation products.

For related substances, only peaks exceeding 0.05% of the total peak area were reported. The summary data for related substances are presented in Table 8, and individual values are given in Table 9 (storage for 7 days at 40°C) and Table 10 (storage for 10 days at 40°C followed by storage for 7 days at 50°C).

Congener peaks were absent upon preparation. At day 7, only the pH 9 formulation contained a peak at a relative retention time of 1.11. With minimal additional peaks observed after 7 days of storage at elevated temperatures, the formulations were further stressed (with increasing storage temperature over time) and upon analysis

- 23 049106 after 17 days of storage, additional peaks were present in several formulations with a clear visible trend of increasing peak number and peak area with increasing pH, ranging from no peaks (pH 4) to 3 peaks with a total peak area of 0.61% (pH 9). The nitrogen-sparged formulation (pH 7) was significantly more stable than its non-sparged counterpart, confirming that oxidation is the degradation pathway. The light-stressed sample was the most degraded sample with a total congener value of 1.68%.

Table 6

Measurement of pH stability for SPL026 in Britton-Robinson buffer

Nominal pH Original Day 7 ^Ь Day ¹⁷ 4.0 3.86 3.84 3.84 5.0 4.57 4.55 4.52 6.0 5.08 5.07 5.06

6.5 5.33 5.33 5.31 7.0 6,12 6.10 6.10 6.5 with N2 bubbling 6,12 6.18 6.09 7.0 UV light 6.07 ^a - - 7.5 6.60 6.58 6.59 8.0 6.87 6.86 6.84 9.0 7.71 7.72 7.70 ^and pH at the end of testing ^ь 7 days storage at 40°C ^{followed by} 10 days storage at 40°C, then 7 days at 50°C

Table 7

pH stability of SPL026 in Britton-Robinson buffer (quantitative determination)

Nominal pH Concentration (mg.ml ¹ ) Original Day 7 ^Ь Day ¹⁷ Light 4.0 2.47 2.57 2.52 - 5.0 2.50 2.48 2.52 - 6.0 2.51 2.56 2.48 - 6.5 2.49 2.59 2.51 - 7.0 2.54 2.54 2.45 - 7.0 with N2 bubbling 2.54 2.54 2.51 - 7.0 UV light 2.54 - - 2.26 ^a 7.5 2.50 2.55 2.46 - 8.0 2.49 2.49 2.42 - 9.0 2.47 2.41 2.46 - ^and the concentration after completion of light stress (200 watt-hours of UV radiation, 0.6 million lux-hours). This sample was an aliquot of a solution with a pH of 7. ^ь 7 days of storage at 40°C ^{followed by} 10 days of storage at 40°C, then 7 days at 50°C

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Table 8

Quantitative determination of total pH stability related substances for SPL026 in Britton-Robinson buffer

Nominal pH Total amount of related substances (%) Original Day 7 ^Ь Day ¹⁷ Light 4.0 BUT BUT BUT - 5.0 BUT BUT 0,07 - 6.0 BUT BUT 0.09 - 6.5 BUT BUT 0,10 - 7.0 BUT BUT 0.26 - 7.0 with N2 bubbling BUT BUT 0,05 - 7.0 UV light BUT - - 1.68 ^a 7.5 BUT BUT 0.42 - 8.0 BUT BUT 0.58 - 9.0 BUT 0,10 0.61 - N/A - <0.02 area of total peak area ^a % of related substances after completion of light stress (200 watt-hours UV, 0.6 million lux-hours). This sample was an aliquot of a solution at pH 7. ⁷ days storage at 40°C ^{followed by} 10 days storage at 40°C followed by 7 days at 50°C

Table 9

Quantitative determination of selected related substances for pH stability for SPL026 in Britton-Robinson buffer, 7 days storage at 40°C

Nominal pH Day ^A Relative retention time and area percentage of total peak area (peaks>0.05% of total peak area) 0.54 0.62 0.64 0.73 0.74 0.77 0.80 0.81 0.91 0.95 1.06 1,10 1,11 1,17 1,20 1.56 4 7 - 5 7 - 6 7 - 6.5 7 - 6.5 s N ₂ ^a 7 - 7 UV ^{light nose} 0,05 0.17 0.54 0.23 0,15 0,06 0,07 - - - - - - 0.18 0.13 0,10 7 7 - 7.5 7 - 8 7 - 9 7 - ^a Nitrogen purge ^ь UV exposure (200 watt-hours UV, 0.6 million lux-hours) ^c Sub-sample of formulation with pH 7

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Table 10

Quantitative determination of selected related substances for pH stability for SPL026 in Britton-Robinson buffer 10 days storage at 40°C, 7 days at 50°C

Nominal pH Day a Relative retention time and area percentage of total peak area (peaks>0.05% of total peak area) 0.54 0.62 0.64 0.73 0.74 0.77 0.80 0.81 0.91 0.95 1.06 1,10 1,11 1,17 1,20 1.56 4 17 - 5 17 - 0,07 6 17 - 0.09 6.5 17 - 0,10 6.5 cN ₂ ^a 17 - 0,05 7 17 - - - 0.09 - - - - 0,05 - - - - - - 0,12 7.5 17 - - - 0.14 - - - - 0,07 - - - 0,12 - - 0.09 8 17 - - - 0,15 - - - - 0.09 0,05 - - 0.22 - - 0,07 9 17 - - - 0,12 - - - - 0.11 - - - 0,12 - - 0.38 ^a Nitrogen purge

Comparison of the stability of the original composition with compositions buffered with B-R.

As described above, DMT fumarate formulations containing the preferred buffer stored at 40 to 50°C, without N2 sparging or UV light exposure control, contained 1.13% congeners after 1 week of storage. The amounts of congeners that formed in the preferred formulation and formulations B-R upon storage for 1 week at 40 to 50°C are compared in Table 11. DMT fumarate formulations containing buffers B-R stored under the same conditions contained less than 0.02% congeners after 1 week of storage (>5.7 times less congeners than the preferred formulation), indicating the greater stability of formulations B-R.

As described above, when developing injectable compositions, it is typical to match the pH of the composition to the pH of the patient's blood serum. Human blood serum has a pH of about 7.4. Therefore, an obvious composition for the salts of the optionally substituted dimethyltryptamine compounds is a composition with a pH of 7.4. Unexpectedly, the greater stability of the compositions of such salts prepared at pH values of 7.0 or less has been found.

Table 11

Short-term stability evaluation of the preferred composition and compositions of the invention

Sample pH Quantitative determination (mg/ml) Related substances (%) Original Day 7 Original Day 7 Original Day 7 2.5 mg/mL/50 mM phosphate buffered saline, pH 7.4 (preferred formulation) 6.88 6.87 2.49 2.38 N.O. <0.02 1,13 2.5 mg/ml/40 mM buffer B-R, pH 3.86 3.84 2.47 2.57 N.O. <0.02 N.O. <0.02

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4.0 (non-obvious composition) 2.5 mg/ml/40 mM B-R buffer, pH 5.0 (non-obvious composition) 4.57 4.55 2.50 2.48 N.O. <0.02 N.O. <0.02 2.5 mg/ml/40 mM B-R buffer, pH 6.0 (non-obvious composition) 5.08 5.07 2.51 2.56 N.O. <0.02 N.O. <0.02 2.5 mg/ml/40 mM B-R buffer, pH 6.5 (non-obvious composition) 5.33 5.33 2.49 2.59 N.O. <0.02 N.O. <0.02 2.5 mg/ml/40 mM B-R buffer, pH 7.0 (non-obvious composition) 6,12 6.10 2.54 2.54 N.O. <0.02 N.O. <0.02

Development of a candidate composition.

Based on the pH stability evaluation, it was decided to fix the pH of the formulation at pH 4.0 (after storage for a week, formulation B-R at pH 4.0 did not contain peaks corresponding to related substances, indicating that it was the most stable formulation) and to evaluate the use of phosphate and acetate buffer systems at concentrations of 20 mM and 40 mM, as they buffer well at the optimal pH for stability, and to evaluate both sodium chloride and dextrose as tonicity adjusting agents.

Receiving the composition.

Details of each individual formulation (numbered 1 through 8) are presented in Table 12 and Table 13. For each formulation, the desired acid and tonicity agent were dissolved in 80 mL of water. The pH of this solution was then adjusted to pH 4 (±0.5) with 1 M sodium hydroxide. The drug substance was then dissolved, the pH was adjusted to pH 4 (±0.1) with more 1 M sodium hydroxide, then made up to volume with water, and the pH was finally checked and adjusted as necessary. The volume of sodium hydroxide used was documented for each formulation. The composition of each formulation is presented below in Table 12 (saline) and Table 13 (dextrose).

An aliquot of each formulation was removed for quantification/related substances and osmolality testing. The residue of each formulation was filtered (0.2 μm filter size) into a clear glass multidose vial, sparged with nitrogen, capped, and stored (60°C) for 14 days. The 40 mM phosphate/dextrose formulation (formulation 8) was divided into two aliquots, with one aliquot stored in a dark glass multidose vial and the other aliquot stored in a clear glass multidose vial.

Table 12

Candidate formulations SPL026 (saline solution)

Compositions with physiological solution Ingredient Composition number 1 2 3 4 SPL026 398 mg 398 mg 398 mg 398 mg Acetic acid 120 mg (20 mM) 240 mg (40 mM) - - Orthophosphoric acid (85%) - - 231 mg (20mM) 461 mg (40 mM) Sodium chloride 780 mg 720 mg 780 mg 720 mg Sodium hydroxide 38.8 mg 60.8 mg 103.2 mg 185.6 mg Volume obtained (ml) 100 100 100 100

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Table 13

Candidate formulations SPL026 (dextrose)

Compositions with dextrose Ingredient Composition number 5 6 7 8 SPL026 398 mg 398 mg 398 mg 398 mg Acetic acid 120 mg (20 mM) 240 mg (40 mM) - - Orthophosphoric acid (85%) - - 231 mg (20mM) 461 mg (40 mM) Dextrose 4300 mg 3900 mg 4300 mg 3900 mg Sodium hydroxide 27.6 47.2 96.4 mg 175.2 mg Volume obtained (ml) 100 100 100 100

Results.

The results for concentration, osmolality and pH for the compositions upon preparation and after storage at 60°C are presented in Table 14. The results for related substances after storage are presented in Table 15.

All compositions were clear, colorless solutions when prepared. No related substances were present in any of the compositions after preparation.

After removal from storage, all compositions were no longer colourless in appearance but had acquired a beige tint to varying degrees, but all remained transparent, the colour being most pronounced in composition 5 (20 mM acetate buffer/dextrose), which had the highest concentration of related substances.

Osmolality and pH were confirmed to be stable for each formulation tested without significant changes.

The total amount of congeners as peaks greater than 0.05% of the total peak area ranged from 0.07% to 0.52%. These data suggest that saline is a preferred tonicity adjusting agent for SPL026 compared to dextrose.

All day 14 results for the 40 mM phosphate/dextrose formulation stored in amber glass mirrored those for clear glass, confirming that storage in clear/amber glass does not affect stability under these storage conditions, but given the previously noted light instability, amber glass should be used as primary packaging.

Table 14 Results, quantification, osmolality and pH for candidate formulations SPL026 (dextrose)

No. Media composition Concentration (mg.ml ¹ ) Osmolality (mOsm/kg) pH Day 0 14 days, 60 °C Day 0 14 days, 60 °C Day 0 14 days, 60 °C 1 20 mM acetate / saline solution 2.50 2.52 305 300 3.94 3.94 2 40 mM acetate / saline solution 2.54 2.54 307 318 3.98 4.01 3 20 mM phosphate/sa. solution 2.55 2.54 315 319 4.01 4.02 4 40 mM phosphate/sa. solution 2.53 2.46 330 347 4.00 3.99 5 20 mM acetate/dextrose 2.50 2.46 300 308 3.97 4.05 6 40 mM acetate/dextrose 2.51 2.47 304 310 4.02 4.06 7 20 mM phosphate/dextrose 2.55 2.51 320 320 4.02 4.04 8 40 mM phosphate/dextrose 2.58 2.48 339 336 4.01 4.04 8 ^a 40 mM phosphate/dextrose - 2.49 - 334 - 4.02 ^and storage in amber glass

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Table 15 Quantitative determination of related substances for candidate formulations SPL026 after storage at 60°C for 14 days

No. Relative retention time and area percentage of total peak area for peaks >0.05% of total peak area General 0.62 0.72 0.80 0.91 1.60 1.61 1 - - - - - 0.11 0.11 2 - - - - 0,08 0.08 3 - - - - 0.09 0.09 4 - - - - 0,07 0,07 5 0,05 0,05 0,07 0,07 0.08 0,20 0.52 6 - - - - - 0.13 0.13 7 - - - 0,05 - 0.16 0.21 8 - - - 0,05 - 0,15 0,20 8 ^a - - - 0,07 - 0.23 0,30

^and storage in amber glass

Conclusion.

All candidate formulations were stable in terms of osmolality and pH after 14 days of stability evaluation. For formulations 1-3 there was no change in the concentration achieved, and for formulations 5-8 the changes (loss on storage) were small (<0.1 mg.mL ^-1 ). For each candidate formulation, congeners were very low, ranging from 0.07 to 0.52% of the total peak area. More congeners were observed in the dextrose formulations than in the saline formulations.

After review of the data, the next formulation SPL026 (referred to here as SPL026 formulation 10) was selected. It is based on formulation 1 but the acetate buffer content was increased slightly to ensure consistent buffering in the formulation throughout the shelf life but at a low enough level to ensure minimal buffering effects in the blood. Sodium chloride levels were reduced slightly to compensate for the additional acetate but to maintain an iso-osmotic solution. This formulation was prepared and analyzed for quantification, pH, and osmolality during preparation. Detailed preparation data and the results achieved are presented below in Table 16.

Table 16

SPL026, preparation of composition 10 2.5 mg/ml and results

Preparation SPL026 398 mg Acetic acid 150 mg Sodium chloride 760 mg Sodium hydroxide As much as needed to reach pH 4.0 - 40 mg Volume obtained (ml) 100 Result Appearance Transparent colorless solution Osmolality (mOsm/kg) 299 pH 3.96 Quantitative determination (mg/ml-1) 2.49

Technical clinical batches of the composition have the above composition. Clinical batches are manufactured in accordance with Good Manufacturing Practice (GMP). The technical batch is used to obtain stability data before preparation of the clinical batch. Early data from the technical batch helps to determine the shelf life of clinical batches manufactured in accordance with GMP.

Overview of the recommended composition preparation process (batch size 100 ml).

Receiving media.

Obtaining 1M sodium hydroxide solution (100 ml).

1. Weigh 4 g of sodium hydroxide granules into a beaker of suitable size.

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2. Pour 80 ml of water for injection (WFI) into a glass.

3. Stir magnetically to dissolve and allow the solution to cool to laboratory temperature.

4. Add purified water to make a volume of 100 ml.

5. Pour into a type 1 borosilicate glass container. Preparation of composition 10 (2.5 mg/ml).

1. Accurately weigh 760 mg of sodium chloride into a suitable container.

2. Weigh out the required amount of the medicinal substance by the difference into a suitable container (glass weighing boat). Make sure that the mass of the medicinal substance taken includes an adjustment for salt and purity.

3. Carefully transfer the drug sample to a beaker. Rinse the weighing container with water for injection to remove any particulate matter. Add additional water for injection to the drug to % of the required total volume and stir with a magnetic stirrer to dissolve. Add a batch of acetic acid (note that acetic acid is volatile, so this step should be done immediately after weighing).

4. Add pre-weighed sodium chloride.

5. After complete dissolution, bring the pH of the composition to pH 4 (±0.1) by adding dropwise freshly prepared 1M sodium hydroxide solution with constant stirring.

6. Bring to volume in a suitable container and finally check that the pH is pH 4 (±0.1) and adjust if necessary.

7. The solution of the medicinal product is transparent with a very slight beige tint. This colour is removed by filtration (step 6), leaving a colourless solution after filtration.

8. Pass nitrogen through the composition until the measured dissolved oxygen content is below 2 ppm.

9. Filter the solution with a syringe using either 0.22 µm or 0.2 µm into a multi-dose amber glass vial.

Composition stability 10 (technical batch).

Appearance and pH.

The results of appearance and pH of composition 10 (technical batch) during preparation and subsequent storage at 2-8°C, 25°C/60% relative humidity (RH) and 40°/75% RH are presented in Table 17. At T=0 (initial analysis), the pH was within the specification of 3.8-4.2 and the osmolality was within the specification of 270-330 mOsm/kg (296 mOsm/kg). By T=9 months, no significant changes in appearance occurred upon storage at 2-8°C or 25°C/60% RH. However, at 40°C/75% RH, an obvious change in product color was observed at T=6 months. Signs of color change were observed after 2 and 3 months of storage at 40°C/75% RH compared to other storage conditions, but the color change was obvious after 6 months. There was no change in pH after 9 months of storage at 2-8°C or 25°C/60% RH or 6 months of storage at 40°C/75% RH.

Table 17

Appearance and pH of composition 10 after storage under the specified conditions

Moment Appearance pH Initial (T = 0) A transparent, colorless liquid without visible particles 4.0 2-8°С T= 1 A transparent, colorless liquid without visible particles 4.0 T = 2 A transparent, colorless liquid without visible particles 4.0 T = 3 A transparent, colorless liquid without visible particles 4.0 T = 6 A transparent, colorless liquid without visible particles 4.0 T = 9 A transparent, colorless liquid without visible particles 4.0 25°С/60% RH T= 1 A transparent, colorless liquid without visible particles 4.0 T = 2 A transparent, colorless liquid without visible particles 4.0 T = 3 A transparent, colorless liquid without visible particles 4.0 T = 6 A transparent, colorless liquid without visible particles 4.0 T = 9 A transparent, colorless liquid without visible particles 4.0

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40°С/75% RH T= 1 A transparent, colorless liquid without visible particles 4.0 T = 2 A transparent, colorless liquid without visible particles 4.0 T = 3 A transparent, colorless liquid without visible particles 4.0 T = 6 A clear, light yellow liquid without visible particles 4.0

Particles invisible to the naked eye.

The number of particles invisible to the naked eye in composition 10 (technical batch) during preparation and subsequent storage at 2-8°C, 25°C/60% relative humidity (RH) and 40°C/75% RH is presented in Table 18. After 6 months of storage at 2-8°C, 25°C/60% RH and 40°C/75% RH, no significant changes occurred in terms of particles invisible to the naked eye (see Table 18).

Table 18

Particles invisible to the naked eye in composition 10 after storage under the specified conditions

Moment in time/months Quantity/bottle ¹ Pass/Fail ² >10 microns >25 microns Initial (T = 0) 5 1 Passing 5°С T=6 3 0 Passing 25°С/60% RH T= 1 9 0 Passing T = 6 3 0 Passing 40°С/75% RH T= 1 4 0 Passing T = 6 14 1 Passing

¹ For a filling volume of 10.5 ml ² Number of particles with a diameter of >10 µm per vial <6000 = PASS and number of particles with a diameter of >25 µm per vial <600 = PASS

Extractable volume

The volume recovered from 6 vials of formulation 10 (technical batch) is presented in Table 19. The density used to calculate the volume was taken from the placebo data used in batch production (1.008 g/ ^cm3 ). The volume recovered complies with the NLT specification of 10.0 ml.

Table 19

Extractable volume of composition 10

Sample Sample weight (g) Extractable volume (ml) 1 10,2791 10,1975 2 10,4192 10,3365 3 10,2732 10,1917 4 10,3162 10,2343 5 10,2696 10,1881 6 10,2516 10,1702 Average 10.3 10.2

Recovery percentage

The percent recovery of SPL026 (free base, mg/mL) in Formulation 10 (technical batch) upon preparation and subsequent storage at 2-8°C, 25°C/60% relative humidity (RH) and 40°C/75% RH are presented in Table 20. There was no significant change in the purity of the formulation after 9 months of storage at 2-8°C or 25°C/60% RH and 6 months of storage at 40°C/75% RH. All recoveries compared to theoretical concentration and T=0 were within the specification limits of 90.0-105.0%.

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Table 20

Percent recovery of SPL026 in composition 10 after storage under the specified conditions

Moment in time/ months 1 2 Average Recovery/Theory ¹ (%) Recovery/T = ^O2 (%) Before filtration 2,518 2,506 2.51 100,5 - After filtration 2,516 2,504 2.51 100.4 99.9 ³ Initial (T = 0) 2,503 2,501 2.50 100,1 - 5°С T= 1 2,508 2,508 2.51 100.2 100.3 T = 2 2,538 2,539 2.54 101,5 101,5 T = 3 2,512 2,523 2.52 100.8 100.7 T = 6 2,515 2.525 2.52 100.8 100.7 T = 9 2,511 2,504 2.51 100.3 100.2 25°С/60% RH T= 1 2,508 2,509 2.51 100.3 100.3 T = 2 2,541 2,535 2.54 101,5 101.4 T = 3 2,525 2,524 2.52 101,0 100.9 T = 6 2,497 2,525 2.51 100.4 100.4 T = 9 2.475 2.496 2.49 99.4 99.3 40°С/75% RH T= 1 2,510 2,499 2.50 100,1 100.2 T = 2 2.538 2.536 2.54 101.5 101.4 T = 3 2,505 2,501 2.50 100,1 100,0 T = 6 2,494 2,494 2.49 99.8 99.7

¹ As a percentage of the theoretical 2.5 mg/ml.

² As a percentage of the initial (T = 0) result.

³ As a percentage of the result before filtering.

Purity/related substances.

The purity of SPL026 (free base, mg/mL) and the amount of impurities observed at different retention times in Formulation 10 (technical batch) during preparation and subsequent storage at 2-8°C, 25°C/60% relative humidity (RH) and 40°C/75% RH are presented in Table 21, Table 22 and Table 23, respectively. The total amount of impurities observed in the formulations after 9 months of storage at 2-8°C and 25°C/60% RH slightly increased due to the impurities at RRT 1.04 being observed for the first time and exceeding the LOQ limit under both conditions. An increase in the total amount of impurities was noted for the sample stored at 40°C/75% RH for 2 months. The increase in impurity content observed at RRT 1.60 is noted starting from T=2 months at 40°C/75% RH compared to other storage conditions, which may be due to the higher storage temperature of 40°C.

Table 21

Purity/related substances of SPL026 in composition 10 after storage at 2-8°C

RRT Time/months and quantity Initial (T = 0) 1 2 3 6 9 SPL026 (free base) ¹ 100,0 100,0 100,0 100,0 100,0 100.0 (99.95) 1.04 But But But But But 0,05 1.60 But But <LOQ <LOQ <LOQ <LOQ General ² But But <LOQ <LOQ <LOQ 0,05

¹ The purity of SPL026 is calculated as 100 - the total number of related substances.

² Sum of related substances >0.05%

Table 22

Purity/related substances SPL026 in formulation 10 after storage at 25°C/60%RH

RRT Time/months and quantity Initial (T = 0) 1 2 3 6 9 SPL026 (free base) ¹ 100,0 100,0 100,0 100,0 100,0 100.0 (99.95) 1.04 But But But But But 0,05 1,18 But But <LOQ But But BUT 1.60 But But <LOQ <LOQ <LOQ <LOQ General ² But But <LOQ <LOQ <LOQ 0,05

¹ The purity of SPL026 is calculated as 100 - the total number of related substances.

² Sum of related substances >0.05%

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Table 23

Purity/related substances SPL026 in formulation 10 after storage at 40°C/75%RH

RRT Time point/months and quantity (% w/w) Initial (T = 0) 1 2 3 6 0.49 But But But But 0,05 0.70 But But <LOO <LOO 0.05 0.77 But But But <LOQ <LOQ 0.81 But But <LOQ <LOQ 0,05 0.92 But But <LOQ <LOQ 0,06 SPL026 (free base) ¹ 100,0 100,0 99.9 99.9 99.7 1,19 But But BUT BUT <LOQ 1,22 But But BUT BUT <LOQ 1.60 But But 0,05 0.07 0,10 General ² But But 0,05 0,07 0.31

¹ The purity of SPL026 is calculated as 100 - the total number of related substances.

² Sum of related substances >0.05%

Composition stability 10 (clinical batch).

At T=0 (initial analysis), the pH was within the specification of 3.8-4.2, the osmolality was within the specification of 270-330 mOsm/kg (resulting in 306 mOsm/kg), and the extractable volume was within the NLT of 10.0 mL (resulting in 10.4 mL). In addition, at T=0, the number of particles invisible to the naked eye was 4 particles/vial >10 μm and 0 particles/vial >25 μm, which was well within the specification of 6,000 or less particles/vial >10 μm and 600 or less particles/vial >25 μm. At T=0, the UV-Vis spectrum of the formulation was within the reference spectra (X ^max at 221 ± 3 nm and 279 ± 3 nm), and the signal was observed at a retention time of ± 2% of the reference standard. Finally, at T=0, container lid tightness testing showed no dye penetration and the formulation was sterile and contained <0.01 EU/mL bacterial endotoxins, well within the specification of 20.5 EU/mL.

Appearance and pH.

The results of appearance and pH of composition 10 (clinical batch) during preparation and subsequent storage at 2-8°C, 25°C/60% relative humidity (RH) and 40°/75% RH are presented in Table 24. By T=3 months, no significant changes in appearance occurred during storage at 2-8°C, 25°C/60% RH or 40°C/75% RH. Signs of color change were observed after 3 months. No change in pH was observed.

Table 24

Appearance and pH of composition 10 after storage under the specified conditions

Moment Appearance pH Initial (T = 0) A transparent, colorless liquid, practically without 4.0 2-8°С T= 1 Clear, colorless liquid, virtually particle-free 3.9 T = 3 A clear, pale yellow liquid, virtually free of particles 4.0 25°С/60% RH T= 1 Clear, colorless liquid, virtually particle-free 4.0 T = 3 A clear, pale yellow liquid, virtually free of particles 4.0 40°С/75% RH T= 1 Clear, colorless liquid, virtually particle-free 3.9 T = 3 A clear, pale yellow liquid, virtually free of particles 4.0

Recovery percentage.

The percentage recovery of SPL026 (free base, mg/mL) in formulation 10 (clinical batch) upon preparation and subsequent storage at 2-8°C, 25°C/60% relative humidity (RH) and 40°C/75% RH is presented in Table 25. There was no significant change in the purity of the formulation after 3

- 33,049,106 months storage at 2-8°C or 25°C/60% RH and 40°C/75% RH. All recoveries compared to theoretical concentration and T=0 are within the specification limits of 95.0-105.0%.

Table 25

Percent recovery of SPL026 in composition 10 after storage under the specified conditions

Moment in time/months SPL026 Recovery Percentage (%) Initial (T = 0) 103.6 2-8 °C T= 1 102.9 T = 3 103.2 25°C/60%RH T= 1 102.7 T = 3 103,0 40°C/75%RH T= 1 102.6 T = 3 102.5

Purity/Related Substances

The purity of SPL026 (free base, mg/mL) and the amount of impurities observed at different retention times in Formulation 10 (clinical batch) during preparation and subsequent storage at 2-8°C, 25°C/60% relative humidity (RH) and 40°C/75% RH are presented in Table 26, Table 27 and Table 28, respectively.

Table 26

Purity/related substances of SPL026 in composition 10 after storage at 2-8°C

RRT Time point/months and quantity (% area) Initial (T = 0) 1 3 1,And <LOQ <LOQ <LOQ 1.59-1.60 0,07 0.08 0,07 General ² 0,07 0.08 0,07

² Sum of related substances >0.05%

Table 27

Purity/related substances SPL026 in formulation 10 after storage at 25°C/60%RH

RRT Time point/months and quantity (% area) Initial (T = 0) 1 3 ι,ιι <LOQ <LOQ <LOQ 1.59-1.60 0,07 0.08 0,07 General ² 0,07 0.08 0.07

² Sum of related substances >0.05%

Table 28

Purity/related substances SPL026 in formulation 10 after storage at 40°C/75%RH

RRT Time point/months and quantity (% area) Initial (T = 0) 1 3 0.56 <LOQ <LOQ <LOQ 0,70 <LOQ <LOQ <LOQ 0.82 <LOQ <LOQ <LOQ 0.94 <LOQ <LOQ <LOQ ι,ιι <LOQ <LOQ <LOQ 1.59-1.60 0.07 0,08 0.09 General ² 0.07 0.08 0.09

² Sum of related substances >0.05%

Claims (13)

1. A pharmaceutical composition containing dimethyltryptamine fumarate salt or deuterated dimethyltryptamine fumarate salt, a buffer and water, wherein the composition has a pH of 3.5 ± 5 to 6.5 ± 5% and an osmolality of 250 ± 5 to 350 ± 5% mOsm/kg. 2. The composition according to claim 1, characterized in that the composition is suitable for injections. 3. The composition according to claim 1 or 2, characterized in that the pH is from 3.75 ± 5 to 6.5 ± 5%, or from 3.75 ± 5 to 5.75 ± 5%, or from 3.75 ± 5 to 4.25 ± 5%. 4. A composition according to any one of claims 1 to 3, characterized in that the fumarate salt is a compound of formula I Formula I where R ⁴ and R ⁵ are both H, and each ^x H and each YH are independently selected from H and D. 5. The composition according to claims 1-4, containing dimethyltryptamine substituted with deuterium at one or both α-carbon atoms. 6. A composition according to any one of claims 1 to 5, characterized in that the concentration of optionally substituted dimethyltryptamine is 2.5 ± 5% mg/ml. 7. A composition according to any one of claims 1 to 6, characterized in that the buffer contains an acetate salt and acetic acid, or sodium acetate and acetic acid; or potassium acetate and acetic acid. 8. A composition according to any one of paragraphs 1-7, characterized in that the composition additionally contains an agent that regulates tonicity. 9. A composition according to any one of claims 1 to 8, having an oxygen content of less than 2 ppm. 10. A method for preparing a pharmaceutical composition according to any one of claims 1 to 9, comprising reacting a dimethyltryptamine fumarate salt or a deuterated dimethyltryptamine fumarate salt, a buffer and water. 11. Use of a composition according to any of paragraphs 1-9 in therapy. 12. Use of a composition according to any one of claims 1-9 in a method for treating a mental or neurological disorder in a patient. 13. The use according to claim 12, characterized in that the mental or neurological disorder is selected from the group consisting of (i) obsessive-compulsive disorder, (ii) depressive disorder, (iii) anxiety disorder, (iv) substance abuse and (v) volitional disorder.