HK40009495B - High-stability packaged solutions of t4 thyroid hormone - Google Patents

Description

FIELD OF THE INVENTION

The present invention relates to the field of pharmaceutical preparations of thyroid hormones. Specifically, the invention relates to a pharmaceutical preparation of thyroid hormone T4 in an alcohol-free water-glycerol solution, suitable for oral administration and characterized by high physical, chemical and microbiological stability. The invention also relates to the use of said pharmaceutical preparation in the treatment of disorders caused by thyroid hormones deficiency.

STATE OF THE ART

The thyroid hormone tetraiodothyronine or thyroxine (T4) is secreted by the follicular cells of the thyroid gland in response to the pituitary-gland hormone TSH, the production of which is regulated in turn by the hypothalamic hormone TRH. The pituitary gland also secretes the T3 hormone (triiodothyronine or liothyronine); in fact, most of the T3 in the body results from conversion of T4 to T3 outside the thyroid gland. T3 is 4-5 times more potent that T4, which means that one mg of T3 has a much greater effect on the body than one mg of T4.

The secretion of thyroid hormones follows a circadian rhythm; the highest levels of T3 and T4 are reached during the night and the early hours of the morning.

T3 and T4 are essential for the normal body growth of children and for the maturation of the various apparatuses, especially the skeleton, and regulate metabolic activity in the adult, influencing the function of every organ and tissue. In particular, T3 and T4 increase oxygen consumption at rest, raising the basal metabolism, the body temperature and the daily calories requirement. They regulate carbohydrate metabolism, promoting glycogenolysis and gluconeogenesis, and increase the activity of the enzymes involved in glucose oxidation. Thyroid hormones are involved in lipolysis and lipogenesis, regulate protein synthesis, exercising a trophic effect on the muscle, and affect the cardiovascular system.

Thyroid hormones are essential to the cardiac function: they increase myocardial contractility (positive inotropic effect), increase the heart rate (positive chronotropic effect) and increase venous return to the heart.

In general, the effect of thyroid hormones is mainly anabolic at low doses, whereas they have a catabolic action at high doses. In situations of physiological deficiency of thyroid hormones, as in the case of primary and secondary hypothyroidism, a treatment based on thyroid hormones is required, administered as such or in the form of sodium salts or hydrates. The treatment continues throughout the patient's life, and the posology (dose and frequency of administration) is customized according to the patient's response.

Selecting the dose is a critical aspect of thyroid hormone treatments: an under-dose leads to a poor response, while an excessive dose can produce toxic symptoms of hyperthyroidism such as tachycardia, sweating, weight loss, nervousness, diarrhoea, bone resorption due to activation of the osteoclasts, and heart problems. It is therefore important for patients to be able to count on reliable formulations in terms of dose accuracy.

T4 and T3 hormones are conveniently administered via the oral route. Although T4 and T3 hormones are both therapeutically effective, the administration of T4 is generally preferred since T3 is too rapidly absorbed from the intestine and this may cause thyroid hormone toxicity (hyperthyroidism). Mixtures of T3 and T4 are also not preferred because the two hormones have different pharmacokinetic and potency, which complicates the establishment of a suitable dosage regime for the patient.

T4 hormone is conveniently administered in the form of solution, which allows a more precise dosing as compared to solid forms; the administration of T4 solutions presents nevertheless some challenges: in fact they are reported to prematurely convert in part to T3 during storage; the extent of conversion is difficult to predict, since the conversion rate may be affected by a variety of environmental conditions. As a consequence, at the time of administration, T4 solutions may be contaminated with non-predictable, sometimes significant levels of T3; this causes inaccuracy of the hormone dose actually administered, with risk of over dosage due to the higher potency of T3; due to the quite higher potency of T3 vs. T4, even small amount of formed T3 may significantly increase the overall dosage of administered hormone, with potential consequences for the patient caused by over-dosing.

A further difficulty derives from the low water solubility of thyroid hormones, causing them to partly precipitate from solutions during storage and/or in consequence of temperature changes; a partial improvement in this area is reported in WO2010/086030 , where the thyroid hormones are formulated in water-alcohol-glycerol solutions showing a good stability; the stability was further enhanced by packaging the solution within containers made of specific polymers. In an attempt to further increase stability, other packaging solutions are described in WO2013072304 , wherein the water-alcohol-glycerol solution was double-packaged (i.e. contained in a plastic container which is contained in a sachet ), or single-packaged in an improved multilayered plastic container. Nevertheless, also in these conditions, a significant degree of instability was observed as regards to conversion of T4 into T3. The publication Boulton et al., Am.J.Health-Syst Pharm., 53, 15 May 1996, pp. 1157-1161, describes solutions extemporaneously prepared by dissolving in water crushed T4 tablets or T4 powders, including glycerol; the solutions, contained in HD-polyethylene bottles, showed a very short shelf stability (up to 8 days in refrigerator); when stored at higher temperatures, significant amounts of T3 degradation product were found after 3 months. Therefore the need is still felt for packaged T4 solutions which remain shelf-stable, particularly at medium/long term, i.e. at 12/18 months, at room temperature, thus allowing storage of the product for a sufficiently long time at normal environmental conditions, as commonly occurring in a pharmacy or a hospital.

SUMMARY OF THE INVENTION

It was now unexpectedly found that the unwanted premature conversion of T4 to T3 in packaged solution can be significantly reduced if T4 is formulated in water-glycerol, alcohol-free solutions. The invention thus relates to highly stable alcohol-free water-glycerol solutions of T4 thyroid hormone, with a reduced amount of T3 impurity, ready-to-use packaged via container arrangements as defined by the claims suitable to maintain a general stability of the solution. The container are multi-barrier ones, in which several layers of different materials separate the solution from contact with the external environment.

DETAILED DESCRIPTION OF THE INVENTION

For the purpose of the present invention, the term "alcohol-free solution" means that the solution is exempt from low-molecular weight alcohols; the term "low molecular weight alcohol" means an alkanol with molecular weight lower than 80 Dalton: e.g. methanol, ethanol, propane, propanediol, isopropanol, and similar alcohols; the term "alcohol-free" remains thus compatible with the presence of glycerol in the solution (whose molecular weight is 92.1 Daltons).

The packaging used in the present invention is a multi-barrier one, i.e. one in which several layers of different materials separate the solution from contact with the external environment as defined by the claims, wherein the T4 solution is contained in the innermost container. The packaging is composed as follows:

1. (a) one-component LDPE plastic container, placed in a sealed sachet consisting of laminated films made of different materials which are: polyethylene, aluminium and polyethylene terephthalate.

Preferably, the plastic container is squeezable by manual compression; also preferably, said container has a thickness of between 150 and 1000 µm, more preferably between 200 and 800 µm, e.g. 600µm ± 15%. Included is also the variant in which more than one LDPE plastic containers, each filled with the solution of T4, are contained within a single sachet containing all of them.

The sachet consists of laminated films made of different materials according to the following combinations: polyethylene, aluminium and polyethylene terephthalate.

An important contribution to the stability of the T4 solution is given by the sum of thicknesses of all the films making up the sachet, i.e. the overall thickness of the sachet made of the specific laminated films mentioned above: this should be preferably comprised within the range of 40 to 100 µm, more preferably of 50 to 90 µm; these conditions advantageously combine an effective protection form T4 degradation to T3, while avoding using excessive packaging material; if desired, values higher than 90 µm may also be used in the present invention, although they are not preferred. Examples of the above described packaging arrangements (not in association with alcohol-free solutions of T4 hormone) are described in the patent application WO2013/072304 .

The water-glycerol solution used in the present invention can typically contain a T4:glycerol weight ratio comprised between 0.004:1000 and 0.4:1000 (i.e. 4 to 400 ppm). If the solution is formulated as a dose unit form, the suitable dose unit will typically contain from 5 to 350µg (or preferably 5 to 250µg) in 1 g of glycerol.

All ratios and amounts of glycerol are herein calculated based on glycerol as pure substance; in practice however, glycerol is handled as a concentrated solution in water, typically at 85% w/w; it is thus understood that the water component of the present solutions may be derived, at least in part, from the water content of commercial glycerol; the water content of glycerol 85% is normally sufficient to obtain the solutions according to the invention; the addition of further amounts of water remains in any case possible within the scope of the invention.

The present T4 solutions contain a reduced amount of T3 impurity, where "reduced" means that T3 may be present at a maximum concentration of 2.5% , preferably 2.0%, more preferably 1.8%. Said values of T3 impurity are calculated herein as follows: (T3µg/mL being present in the sample / T4µg/mL being present in the sample) *100. The reduced amount of T3 impurity is consequence of the high level of storage stability reached (in terms of limited T4 to T3 conversion), as supported in the experimental section; in particular, at the end of the stability period (25°C±2°C/60±5% R.H.), the pharmaceutical preparation according to the invention showed a T4 content of not less than 95% of the initial concentration, and total impurities within the standard acceptability criteria.

Moreover, the pharmaceutical preparation according to the invention guarantees the absence of microbiological contamination, with TAMC (total aerobic microbial count) values ≤ 100 CFU/g, TYMC (total yeast and mould count) values ≤ 10 CFU/g, and absence of E. coli, thus being practical to use and not liable to accidental contamination.

The high level of storage stability reached by the present water-glycerol solutions, makes it advantageously unnecessary to introduce stabilizers in the composition, (e.g. pH correcting agents, buffers, chelating agents, etc.); when so-formulated, the compositions of the invention involve the additional advantage of avoiding unnecessary administration of additives to the patient and reducing the complexity/cost of the final medicinal product.

The pharmaceutical preparation according to the invention is conveniently used to treat disorders associated with thyroid hormone T3 and/or T4 deficiency. It is preferably administered orally, i.e. it is suitable for oral administration. It is noted that, although the present T4 solutions do not contain T3 (or contain it in extremely low amounts), their use extends to treat T3 deficiency since T4 is physiologically converted into T3 by the organism after administration.

A further aspect of the invention therefore relates to the use of a water-glycerol solution of thyroid hormone T4 in a packaging as described above, to prepare a medicament for the treatment of disorders associated with thyroid hormone T3 and/or T4 deficiency; the medicament is preferably suitable for oral administration.

A further aspect of the invention relates to a pharmaceutical preparation of a water-glycerol solution of thyroid hormone T4 in a packaging as described above, for use in the treatment of disorders associated with thyroid hormone T3 and/or T4 deficiency; the preparation is preferably suitable for oral administration.

A further aspect of the invention relates to a method of treating disorders associated with thyroid hormone T3 and/or T4 deficiency comprising administering a water-glycerol solution of thyroid hormone T4 packaged as described above, to a patient in need thereof; the solution is preferably suitable for oral administration.

The present invention thus provides new packaged solutions of T4, being advantageously more stable to an unwanted premature conversion of T4 in T3. The increased stability ensures a more reproducible and constant amount of administered hormone, avoiding any possible overdosing due to excessive administration of T3 impurities. The non-use of volatile alcohols like ethanol brings a further advantage in that the formulation does not suffer from accidental reduction of alcohol content, which reflects in an unwanted variation of hormone solubility/stability of the solution. Furthermore, the absence of such alcohols in the present water-glycerol solutions did not substantially change the overall stability of the solution in terms of T4 potency, total impurities and microbial contamination, thus resulting in a preparation meeting all the acceptability criteria for pharmaceutical use.

EXPERIMENTALS

The following acronyms are herein used: polyethylene (PE), polyethylene terephthalate (PET), ethylene vinyl alcohol copolymer resins (EVOH), polyvinyl chloride (PVC), polyvinylidene chloride (PVdC), polyvinyl acetate (PVA), cyclic olefin copolymers (COC), polyamides (PA), polystyrene (PS), polycarbonate (PC).

EXAMPLE 1: water-ethanol-glycerol T4 solution (reference)

The reference formulation was prepared in accordance with example 1 of WO2013/072304 . Accordingly, one liter of water-alcohol solution containing 100 µg/mL of T4 is prepared as follows, using the qualitative/quantitative composition listed below:

1) T4	0.105 g
2) ethanol (96%)	243 g
3) glycerol (85%)	861 g

The T4 was solubilized in ethanol in a suitable dissolver, under continuous stirring at ambient temperature. When a clear solution free of visible non-solubilized residues was obtained, glycerol was added, and a homogenous, clear, colourless solution was obtained under gentle stirring at ambient temperature. The solution was filtered (0.8 µm), and was then ready for packaging. The final T4 concentration in solution was 100 µg/mL. Following the same method, further solutions were prepared having the final concentrations of 25 µg/mL, 50 µg/mL, 75 µg/mL.

The packaging arrangement, made according to example 3 of WO2013/072304 , was as follows: single-dose container with a nominal volume of 1.10 mL made of one-component LDPE plastic (600 µm thick) contained in a sealed sachet (PET/Al/PE). Characteristics of sachet:

• Stratified film with high gas and light barrier:
• Polyethylene terephthalate 12 µm, (value to be considered ± 5-6%);
• Al 9 µm, (value to be considered ± 5-6%);
• Polyethylene 50 µm (values to be considered ± 5-6%);
• Overall thickness: 71 µm.
• Oxygen permeability: 0.1-0.2 cc/m2/day
• Water vapor permeability: 0.1-0.2 g/m2/day

The oxygen permeability was measured in accordance with ASTM Standard D-3985.

The water permeability was measured in accordance with ASTM Standard E-398.

The prototypes were prepared on a laboratory scale, using an automatic pipette (Gilson P-1000) to fill disposable containers with 1.1 mL of the water-glycerol-ethanol solution previously described, after which the containers were sealed with a Pentaseal-lab benchtop sealing machine. They were then packaged in a hermetically sealed sachet of the type described above.

EXAMPLE 2 : water-glycerol T4 solution

A number of solutions were prepared according to the previous reference Example 1, replacing the water-ethanol-glycerol solution described therein with the alcohol-free water-glycerol solution in accordance with the present invention. Accordingly, the following growing amounts of T4 hormone were dissolved in 1.222 g of glycerol 85%: 25µg, 50µg, 75µg, 100µg, obtaining the respective final concentrations of: 25µg/mL, 50µg/mL, 75µg/mL, 100µg/mL.

Packaging arrangement: single-dose container with a nominal volume of 1.10 mL made of one-component LDPE plastic (600 µm thick) contained in a sealed sachet (PET/Al/PE). Characteristics of sachet: Stratified film with high gas and light barrier: Polyethylene terephthalate 12 µm, Al 12 µm, Polyethylene 45 µm (all values to be considered ±5-6%); Overall thickness: 69 µm.

EXAMPLE 3 Storage stability studies

The packaged solutions obtained in the previous examples 1 and 2 were subjected to storage stability testing with the aim, in particular, to evaluate the extent of conversion of T4 in T3 during storage, in both normal or accelerated conditions. The sealed sachets were thus placed in suitable environmental test chambers, and immediately underwent a stability study under ICH conditions; the equipment used was calibrated and instantly monitored for correct operation. The following tables show the compared performances of the products obtained in Examples 1 and 2. / - / ±

Example 1 (reference)	≤ 2.5	0.3	0.5	0.8	1.0	1.5
Example 2 (invention)	≤ 2.5%	1.0	0.7	0.7	0.7	1.1

/ - / ±

Example 1 (reference)	≤ 2.5	0.3	0.5	0.8	1.0
Example 2 (invention)	≤ 2.5%	0.7	0.9	1.3	0.8

/ - / ±

Example 1 (reference)	≤ 2.5	0.5	1.2	1.3	1.5	2.1
Example 2 (invention)	≤ 2.5%	0.5	0.7	0.8	0.9	1.4

/ - / ±

Example 1 (reference)	≤ 2.5	1.1	1.8	2.0	2.4
Example 2 (invention)	≤ 2.5%	0.6	1.2	1.7	2.2

/ - / ±

Example 1 (reference)	≤ 2.5	1.1	1.0	1.2	1.4	1.8
Example 2 (invention)	≤ 2.5%	0.5	0.8	0.9	1.0	1.5

/ - / ±

Example 1 (reference)	≤ 2.5	1.3	2.2	2.4	2.6
Example 2 (invention)	≤ 2.5%	0.7	1.3	1.8	2.3

7: / - / ±

Example 1 (reference)	≤ 2.5	0.5	1.0	1.3	1.5	2.2
Example 2 (invention)	≤ 2.5%	0.5	0.8	0.8	1.0	1.4

/ - / ±

Example 1 (reference)	≤ 2.5	1.1	1.9	2.4	2.8
Example 2 (invention)	≤ 2.5%	0.7	1.4	1.9	2.2

It can be seen that all the tested samples in accordance with the invention, at substantially all doses, storage times and storage conditions, showed a consistent reduction of conversion in T4 to T3. The aims of the present invention are thus met.

Claims (12)

1. A pharmaceutical preparation of T4 thyroid hormone, in ready-to-use packaging, consisting of a container pre-filled with an alcohol-free water-glycerol solution of hormone T4, said container being a one-component LDPE plastic container, placed in a sealed sachet consisting of laminated films made of polyethylene, aluminium and polyethylene terephthalate.
2. A pharmaceutical preparation according to claim 1, wherein the T4/glycerol weight ratio in said water-glycerol solution is comprised from 4 and 400 ppm.
3. A pharmaceutical preparation according to claims 1-2, wherein said water-glycerol solution contains less than 2.5% of T3 impurity.
4. A pharmaceutical preparation according to claims 1-3, wherein said water-glycerol solution contains less than 2.0 % of T3 impurity.
5. A pharmaceutical preparation according to claims 1-4, wherein said water-glycerol solution contains less than 1.8 % of T3 impurity.
6. A pharmaceutical preparation according to claims 1-5, wherein the preparation is in single-dose form, containing 5 to 350 µg T4 thyroid hormone.
7. A pharmaceutical preparation according to claims 1-6, wherein the preparation is in single-dose form, containing 5 to 250 µg T4 thyroid hormone.
8. A pharmaceutical preparation according to claims 1-7, wherein said plastic container has a thickness of between 150 and 1000 µm.
9. A pharmaceutical preparation according to claims 1-8, wherein said plastic container has a thickness of between 200 and 800 µm.
10. A pharmaceutical preparation according to claims 1-9, wherein said sachet has an overall thickness comprised between 40 and 100 µm.
11. A pharmaceutical preparation according to claims 1-10, wherein said sachet has an overall thickness comprised between 50 and 90 µm.
12. A pharmaceutical preparation according to claims 1-11, for use in the treatment of diseases associated with T3 and/or T4 hormone deficiency.