WO2012098143A1

WO2012098143A1 - Use of inhibitors of atp-sensitive potassium channels for the treatment of hearing loss

Info

Publication number: WO2012098143A1
Application number: PCT/EP2012/050683
Authority: WO
Inventors: Jochen Roeper; Silvi HOIDIS; Jean SMOLDERS; Manuel GROTH
Original assignee: Goethe Universitaet Frankfurt am Main
Current assignee: Goethe Universitaet Frankfurt am Main
Priority date: 2011-01-18
Filing date: 2012-01-18
Publication date: 2012-07-26
Anticipated expiration: 2013-07-18
Also published as: GB201100783D0; GB2487366A

Abstract

The present invention relates to the use of inhibitors of ATP-sensitive potassium channels for the protective (including preventive) therapy or the reduced progression of hearing loss, in particular age-related hearing loss (presbycusis) and/or noise-induced hearing loss (NIHL). Preferred is the systemic or local administration of clinically established sulfonylureas, such as, for example, glibenclamide.

Description

Use of inhibitors of ATP-sensitive potassium channels for the treatment of hearing loss

Presbyacusis is a major form of sensorineural age-related hearing loss that involves the degeneration and irreversible loss of hair cells (HC) in the mammalian inner ear. It affects about 70-80% of the elderly (> 65 years) and currently no protective or curative therapy exists. The pathome- chanisms of presbyacusis are not well understood, but ischemia, oxidative stress and mutations of mitochondrial DNA might, among others, contribute to hair cell loss.

One of the most common causes of hearing deficits is the loss of sensory HC that is due to a variety of factors like as an excessive exposure to noise. The problem is particularly common in the military and in industrial settings. Noise-induced hearing loss (NIHL) is a leading occupational disease, with up to 5% of the population at risk world-wide. The proportion of non-work related NIHL is also on the rise, the causes include increased levels of ambient noise in developed areas from motor vehicles, construction sites, and the constant use of portable music players.

Glibenclamide is an example for the group of sulfonylureas and is used as an oral antidiabetic. Glibenclamide selectively blocks ATP-sensitive potassium channels in β-cel!s of the pancreas, which facilitates insulin release.

Herzog et al. (in: Herzog M, Scherer EQ, Albrecht B, Rorabaugh B, Scofield MA, Wangemann P. CGRP receptors in the gerbil spiral modiolar artery mediate a sustained vasodilation via a transient cAMP-mediated Ca2+-decrease. J Membr Biol. 2002 Oct l; 189(3):225-36) describe the alteration of cochlear blood flow as may be involved in the etiology of inner ear disorders like sudden hearing loss, fluctuating hearing loss and tinnitus. The K+-channel blockers iberiotoxin and glibenclamide partially prevented CGRP- or forskolin-induced vasodilations but failed to reverse these vasodilations. The publication suggests that the vasodilation, amongst others, is mediated by a transient activation of glibenclamide-sensitive KATP channels. Glibenclamide can prevent vasodilation, but not reverse it. Furthermore, a connection with presbycusis is not mentioned.

Wu and Marcus (in: Wu T, Marcus DC. Age-related changes in cochlear endolymphatic potassium and potential in CD-I and CBA/CaJ mice. J Assoc Res Otolaryngol. 2003 Sep;4(3):353-62) describe the CD-I mouse strain as known to have early onset of hearing loss that is progressive with aging, and thus examined whether a disturbance of K+ homeostasis and pathological changes in the cochlear lateral wall were involved in the age-related hearing loss (AHL) of CD-I as compared to the CBA/CaJ strain which has minimal AHL. Old CD-I mice displayed a significantly reduced endolymphatic K+ concentration by 30% in both basal and apical turns. WO 2010/042728 describes a method of inhibiting cellular uptake of pro-nerve growth factor (proNGF) in a cell expressing neurotrophin p75 receptor in a mammal by providing glyburide (glibenclamide) in hearing loss patients. According to WO 2010/042728, the expression, secretion, and signalling by neurotrophins, proneurotrophins, and their receptors has been found to be important for development and maintenance of neurons and hair follicles involved in hearing.

Nevertheless, according to Sato et al (2006) as cited by WO 2010/042728, the neurotrophin receptor p75 may play a significant role in the maintenance of cochlear function, and mice carrying a mutation in the p75 gene could be a good animal model of early onset progressive hearing loss. Furthermore, the neurotrophin receptor p75 is not an ATP-sensitive potassium channel. Presbycusis is not described in WO 2010/042728.

US 2007-248690 describe the use of a composition for the treatment of the symptoms of neurotoxicity, which may be manifested auricularly as tinnitus, Meniere's Disease and hearing loss. The composition for alleviating symptoms of neurotoxicity comprises at least one glutamate antagonist; at least one cAMP stimulating agent; at least one antioxidant; and vitamin B12. As a glutamate antagonist, optionally a glutathione promoting agent (taurine) can be used. Presbycusis is not described, as this condition is not related to neurotoxicity. A similar disclosure is found in US 2005-129783, which is related to neurophysiological conditions. Presbycusis is not described.

Finally, Kocher (in: Kocher, "Presbycusis: Reversible with anesthesia drugs?", Medical Hypotheses, 72, 2009, 157-159) describes that the author, as a patient, experienced a reversal of high- frequency hearing loss during a 2-day period following abdominal surgery with general anesthesia. A possible role is noted for anesthetic agents such as lidocaine, propofol, or fentanyl. Nevertheless, this publication is purely speculative, and other publications show that for example the intratympanic administration of dexamethasone in a group of patients with unilateral Meniere's disease (Shea's stage IV) showed no benefit over placebo for the treatment of hearing loss and tinnitus (Silverstein H et al., Dexamethasone inner ear perfusion for the treatment of Meniere's disease: a prospective, randomized, double-blind, crossover trial. Am J Otol. 1998 Mar; 19(2): 196-201).

WO 2005/025293 describes fused ring heterocycles as potassium channel modulators, in particular in the treatment of diseases through the modulation of potassium ion flux through voltage-dependent potassium channels, such as central or peripheral nervous system disorders (e.g., migraine, ataxia, Parkinson's disease, bipolar disorders, trigeminal neuralgia, spasticity, mood disorders, brain tumors, psychotic disorders, myokymia, seizures, epilepsy, hearing and vision loss, Alzheimer's disease, age-related memory loss, learning deficiencies, anxiety and motor neuron diseases, maintaining bladder control or treating urinary incontinence). WO 2005/025293 relates to the modulation of "voltage-dependent" potassium-channels, and therefore channels different in molecular composition, functional and pharmaceutical properties from those in the present invention.

In view of the above, an ongoing demand exists for the development of new and effective treatments for the protective (including preventive) therapy or the reduced progression of hearing loss, in particular age-related hearing loss (presbycusis) and/or noise-induced hearing loss (NHL). In a first aspect of the present invention, this object of the present invention is solved by an inhibitor of an ATP-sensitive potassium channel for use in the treatment of hearing loss, preferably age-related hearing loss (presbycusis) and/or and noise-induced hearing loss (NIHL). Further preferred is the use of glibenclamide for the production of a medicament for the treatment of hearing loss, preferably age-related hearing loss (presbycusis) and/or noise-induced hearing loss (NIHL). Another aspect of the present invention relates to a method for treatment of hearing loss, preferably age-related hearing loss (presbycusis) and/or noise-induced hearing loss (NIHL), comprising administering to a patient in need thereof a therapeutically effective amount of an inhibitor of an ATP-sensitive potassium channel.

In the context of the present invention, treatment shall include both cell-protective (including preventive) therapy or the reduced progression and/or actual treatment of the disease symptoms of hearing loss, preferably, age-related hearing loss and/or noise-induced hearing loss (NIHL) as described herein, which can be alleviated and/or even completely abolished using said treatment.

Preferred is an inhibitor of an ATP-sensitive potassium channel according to the present invention, wherein said ATP-sensitive potassium channel is selected from ATP-sensitive potassium channels of the plasma membrane that comprise Ki_r6.1 and/or Ki_r6.2-type subunits as well as sulfonylurea receptors (SURl/SUR2a/b), and combinations thereof. More preferred is the inhibitor of an ATP-sensitive potassium channel according to the present invention, wherein said ATP-sensitive potassium channel is selected from ATP-sensitive potassium channels comprising an Ki_r6.2-type subunit, as well as a SUR1 subunit.

Furthermore, additional suitable potassium channels can be identified by the person of skill based on channels based on methods as described in the literature, such as, for example in Shieh et al. (Shieh CC, Coghlan M, Sullivan JP, Gopalakrishnan M Potassium channels: molecular defects, diseases, and therapeutic opportunities Pharmacol Rev. 2000 Dec;52(4):557-94). Over 50 human genes encoding various K(+) channel subunits have been cloned during the past decades, and precise biophysical properties, subunit stoichiometry, channel assembly, and modulation by second messenger and ligands have been elucidated to a large extent. Recent advances in genetic linkage analysis have greatly facilitated the identification of many disease-producing loci, and naturally occurring mutations in various K(+) channels have been identified in diseases such as long-QT syndromes, episodic ataxia/myokymia, familial convulsions, hearing and vestibular diseases, Bartter's syndrome, and familial persistent hyperinsulinemic hypoglycemia of infancy. Shieh et al. aim to 1) provide an understanding of K(+) channel function at the molecular level in the context of disease processes and 2) discuss the progress, hurdles, challenges, and opportunities in the exploitation of K(+) channels as therapeutic targets by pharmacological and emerging genetic approaches.

The present invention is based on the surprising finding that the application of sulfonylureas, such as, for example, glibenclamide in a mouse model showed a clearly protective effect on hearing of aging animals. A similar effect is expected in the human patient, whereby an irreversible loss of the inner and outer hair cells shall be prevented. Nevertheless, the detailed mechanisms for the effect of inhibitors of ATP-sensitive potassium channels are currently not known.

In mouse models of Parkinson Disease, where aging is also the main risk factor, the genetic inactivation of the ATP-sensitive potassium channel (K-ATP) subunit Kir6.2 completely rescued vulnerable dopamine neurons from degeneration (Liss et al. 2005, Nature Neuroscience). Thus, the inventors investigated whether the early age of onset and rapid progression of presbyacusis present in the C57BL/6 mouse genetic background could be prevented by systemically blocking Kir6.2-containing K-ATP channels with the specific inhibitor glibenclamide (sulfonylurea).

The inventors also investigated whether the degree of noise-induced hearing loss could be reduced by systemically blocking Kir6.2-containing K-ATP channels with the specific inhibitor glibenclamide (sulfonylurea).

In general, any suitable inhibitor of an ATP-sensitive potassium channel according to the present invention can be used in order to provide a treatment. In addition to the inhibitors as described herein, such as the sulfonylureas, the person of skill can identify new inhibitors through screening potential inhibitors using known ATP-sensitive potassium channels, such as, for example ATP- sensitive potassium channels comprising SURl/Ki_r6.2-type subunits.

Preferred is the inhibitor of an ATP-sensitive potassium channel according to the present invention, wherein said inhibitor is selected from a sulfonylurea compound containing a central S-phenyl sulfonylurea structure, for example with at least one p-substitution on the phenyl ring, and various groups terminating the urea N' end group, such as acetohexamide, chlorpropamide, tolbutamide, tolazamide, glipizide, gliclazide, glibenclamide (glyburide), gliquidone, gly- clopyramide, glibornuride, and glimepiride. All sulfonylureas contain a central S-phenyl sulfonylurea structure with p-substitution on the phenyl ring and various groups terminating the urea N' end group. Further preferred are a 1. generation or 2. generation sulfonylurea, glinides, and other drugs established to inhibit beta-cell-like ATP-sensitive potassium channels, such as glinides, such as, for example, nateglinide, repaglinide, mitiglinide, meglitinide, gliptins, such as, for example, sitagliptin, vildagliptin, thiazolidinedione derivatives, such as troglitazone, englita- zone, ciclazindol, neomycin, (-)-epigallocatechin-3-gallate (EGCG), a major polyphenolic substance found in green tea, haloperidol, taurine, propofol, thiamylal, phenformin, metformin, benzo[c]quinolizinium compounds MPB-91, cyanoguanidine PNU-99963, midaglizole, LY397364, LY389382, stilbene disulphonates D1DS and SITS, mefloquine, and MCC-134 (l-[4- (lH-imidazol-l-yl)benzoyl]-N-methyI-cyclobutanecarbothioamide).

In general, the inhibitor according to the invention can be provided to the patient in any suitable and effective manner, such as orally, topically, subcutaneously, systemically, rectally or by injection. Preferred is systemically or locally. Furthermore, the inhibitor according to the invention can be provided to the patient in any suitable and effective pharmaceutically acceptable form, such as in the form of a tablet, eardrops, subcutaneous pellet, drops, droplets, capsule, dragee, powder, suppository and/or gel. Most preferred is the systemic or local administration of already clinically validated and established sulfonylureas, such as, for example glibenclamide. Particularly preferred is the local intracochlear administration, for example via an implanted device, such as, for example, a respectively modified drug eluting electrode, drug reservoir electrode, an electrode coated with a drug-releasing polymer, or the intrascalar application via implantable micro-fluidics technology systems (see, for example, Fiering J, et al., Local drug delivery with a self-contained, programmable, microfluidic system. Biomed Microdevices. 2009 Jun; l l(3):571-8).

In general, the inhibitor according to the invention can be provided to the patient in any suitable and effective amount or dosage, such as in an amount of between 0.1 mg to 10 mg, preferably 0.2 mg to 5 mg, and more preferably between 0.5 mg to 2 mg per dosage as administered. Further preferably, said inhibitor according to the invention is provided in a dosage of between 0.2 mg/kg of body weight to 5 mg/kg of body weight per day, preferably between 0.1 mg/kg of body weight to 2 mg/kg of body weight per day. Furthermore, the inhibitor according to the invention can be provided to the patient over any suitable period of time in one or more dosages per day, preferably said inhibitor is administered over a period of between 4 weeks to 12 months to the patient.

The patient preferably can be a mammalian patient, such as, for example, a human patient, of any age for protection against noise-induced hearing loss, and more preferably a patient having an age of more than 50 years, or 55 years for preventing presbyacusis. In particular, the invention also includes younger patients with an increased risk of noise exposure, such as, for example, soldiers, musicians or hunters.

Another aspect of the present invention relates to a method for treating hearing loss, preferably age-related hearing loss (presbycusis), comprising administering to a patient in need thereof a therapeutically effective amount of an inhibitor of an ATP-sensitive potassium channel as described herein.

Yet another aspect of the present invention then relates to a method for reducing the frequency, occurrence, and/or severity of hearing loss, preferably age-related hearing loss (presbycusis) and/or noise-induced hearing loss (NIHL), comprising administering to a patient in need thereof a therapeutically effective amount of an inhibitor of an ATP-sensitive potassium channel as described herein.

Systemic application of glibenclamide significantly reduces the progression of both, age-related hearing loss in a mouse model of presbyacusis as well as hearing loss a mouse model of noise- trauma (NIHL) . The inventors' results indicate that glibenclamide, a licensed drug in human therapy of diabetes mellitus, promises to have a therapeutic potential against age-related and/or noise-induced hearing loss also in humans. The inventors expect an even larger efficiency combined with smaller systemic side effects by local glibenclamide treatment of the inner ear, for example, by the use of established intratympanic drug delivery systems (see also above).

The present invention will now be explained in the following examples with reference to the accompanying figures, without being limited thereto. For the purposes of the present invention, all references as ci ted herein are incorporated by reference in their entireties.

Figure 1 shows the mean ABR thresholds of wildtype mice at the age of 4 weeks (dashed line, n=7) and age-matched Kir6.2 knockout mice (continuous line, n=l 1).

Figure 2 shows the mean ABR thresholds of wildtype mice at the age of 12 weeks (dashed line, n=7) and age-matched Kir6.2 knockout mice (continuous line, n=l 1).

Figure 3 shows the mean ABR thresholds of wildtype mice at the age of 24 weeks (dashed line, n=7) and age-matched Kir6.2 knockout mice (continuous line, n=l 1).

Figure 4 shows the mean ABR thresholds of 52 week old wildtype mice (n=14; dashed line) and 96 week old Kir6.2 knockout mice (n=5; continuous line). Figure 5 shows the time course of mean ABR thresholds of Kir6.2 knockout mice from 4 weeks up to 52 weeks of age (left panel) and wildtype mice (right panel) from 4 weeks up to 96 weeks of age.

Figure 6 shows the mean ABR-thresholds of 13 C57BL/6 mice treated with Placebo pellets (dashed line) and 13 C57BL/6 mice treated with glibenclamide pellets (continuous line) before treatment on day one (P0).

Figure 7 shows the mean ABR-thresholds of 12 C57BL/6 mice treated with Placebo pellets (dashed line) and 10 C57BL/6 mice treated with glibenclamide pellets (continuous line) 13 weeks after pellet implantation (P13W).

Figure 8 shows the mean ABR-thresholds of 13 C57BL/6 mice treated with Placebo pellets (dashed line) and 13 C57BL/6 mice treated with glibenclamide pellets (continuous line) 26 weeks after pellet implantation (P26W).

Figure 9 shows the time course of mean ABR thresholds of the glibenclamide treated mice (left panel) and the placebo group (right panel) from experimental day one (P0) up to 26 weeks after pellet implantation (P26W).

Figure 10 shows in A: Mean ABR-thresholds at the age of 10 weeks (BlOW), two weeks after low dose pellet implantation (27.8 μg/day), of 5 C57BL/6 mice treated with controls pellets (dashed line) and 10 C57BL/6 mice treated with glibenclamide pellets (continuous line). In B: Mean ABR-thresholds of the same groups of animals 14 days after noise exposure. The two audiograms show the permanent sound induced threshold shift (PTS).

Figure 11 shows in A: Mean ABR-thresholds at the age of 10 weeks (BlOW), two weeks after high dose pellet implantation (277.8 μg/day), of 10 C57BL/6 mice treated with control pellets (dashed line) and 10 C57BL/6 mice treated with glibenclamide pellets (continuous line). In B: Mean ABR-thresholds of the same groups of animals 14 days after noise exposure. The two audiograms show the permanent sound induced threshold shift (PTS).

Examples

Example 1 - K-ATP channel knockout mice are protected against presbyacusis

To compare the onset and progression of age-related hearing loss (presbyacusis) in mice with a genetic inactivation of the ATP-sensitive potassium channel (K-ATP) subunit Kir6.2 (Kir6.2KO) in comparison to genetic background controls (C57B16), the inventors determined threshold audiograms from auditory brainstem evoked responses (ABR) to tone-pips (2-45 kHz) from an age of 4 up to 96 weeks. Results are plotted as mean ± SEM. Fishers F-test and Student's t-test were used to assess statistical differences of mean ABR thresholds at a significance level of 0.05 (*) or 0.01 (**).

Wildtype mice of C57BL/6 genetic background developed early-onset presbyacusis with increased thresholds in the high frequency range. In contrast, Kir6.2 knockout (KO) mice showed a statistically significant slowing and reduction of the age-dependent high-frequency hearing loss by about 50 dB at one year of age. At 4 weeks of age ABR thresholds of Kir6.2 KO mice and C57BL/6 mice were similar. However, at higher frequencies (32 and 45.2 kHz) Kir6.2 KO mice showed significantly lower thresholds (Fig. 1).

Typically, age-related hearing loss proceeds from high to low frequencies. In the wildtype mice, it has reached 16 kHz at 12 week of age (Fig. 2). However, a moderate hearing loss also occurs at the lower frequencies (2.8 and 4 kHz). In contrast, there was no significant hearing loss at any frequency in the Kir6.2 KO mice:

At the age of 24 weeks C57BL/6 mice developed a severe hearing loss both at the higher and lower frequencies compared to the Kir6.2KO mice (Fig. 3).

At 96 weeks of age wildtype mice are virtually deaf (dashed line in Fig. 4). The C57BL/6 audiogram at 52 weeks of age showed significant frequency dependent threshold losses between 20 to 45 dB (Fig 4).

In contrast to wildtype mice, which developed early-onset presbyacusis with increased thresholds in the high frequency range, Kir6.2 knockout mice showed a significant slowing of age- dependent hearing loss and reduction of the age-dependent high-frequency hearing loss by about 50 dB at one year of age (Fig. 5). The inventors verified by histological analysis that presbyacusis was associated with hair cell loss. Global genetic inactivation of K- ATP channels containing the Kir6.2 subunit significantly reduces the progression and severity of age-related hearing loss in a mouse model of presbyacusis. As the inventors also detected mRNA and functional expression of Kir6.2-mediated K-ATP channels in cochlear hair cells, the data show that Kir6.2-containing K- ATP channels in hair cells might control the vulnerability for age-related hearing loss. Given the global and unconditional nature of the Kir6.2 knockout model, more indirect and systemic effects cannot be excluded. However, the main systemic effect in the Kir6.2 KO mouse is a diabetic metabolic state with reduced glucose tolerance, which is expected to accelerate presbyacusis. In conclusion, our aging study establishes K-ATP channels as novel and promising drug targets to treat age-related hearing loss.

Example 2 - Pharmacological inhibition of ATP-sensitive potassium channels reduces age- related hearing loss in a mouse model of presbyacusis

Methods

Wild-type C57BL/6 mice (8 week old males, obtained from Charles River WIGA GmbH, Germany) were implanted with subcutaneous pellets, releasing glibenclamide (glyburide) at a concentration of 27.8 μg per day over a period of up to 7 months. An age matched control group was implanted with placebo pellets (pellets without glibenclamide). Pellets were obtained from Innovative Research of America (Sarasota, FL). The occurrence and progression rates of age- related hearing loss were monitored by recording auditory brainstem response (ABR) thresholds. All data are plotted as mean ± SEM. Fishers F-test and Student's t-test were used to assess statistical differences of mean ABR thresholds at a significance level of 0.05 (*) or 0.01 (**).

Results

Male C57BL/6 mice implanted at 8 weeks of age with glibenclamide pellets for chronic application over a period of up to 7 months showed a delayed onset of and significantly (p<0.05) less age-related hearing loss compared to placebo-treated controls.

Before treatment at 8 weeks, no statistically significant differences in ABR thresholds were detected between the experimental and placebo groups (Fig. 6).

Thirteen weeks after pellet implantation mice treated with glibenclamide showed less age-related hearing loss compared to the placebo group. Note the lower ABR thresholds in the glibencla- mide-treated group compared to the placebo-treated group, especially at the higher frequencies (p<0.05). For instance, at 22.6 kHz the threshold of the glibenclamide-treated group was about 15 dB below that of the placebo-treated control group (Fig. 7).

Another 13 weeks later (P26W) the age-related hearing loss at 22.6 kHz in the glibenclamide- treated group was 23 dB less than in the control group (Fig. 8). Age-related hearing loss in humans and rodents typically progresses from high to low frequencies and has reached 16 kHz at this age in the control group.

The progression of age-related hearing loss was delayed and of smaller amplitude in glibenclamide-treated mice compared to placebo-treated animals (Fig. 9). At 32 kHz the age-related threshold elevation in both the glibenclamide treated and control group was substantial, but significantly (p > 0.05) smaller in the glibenclamide-treated group. At 22.6 kHz and 16 kHz the protective effect of glibenclamide was obvious.

Systemic application of glibenclamide significantly reduces the progression of age-related hearing loss in a mouse model of presbyacusis. The inventors' results indicate that glibenclamide, a licensed drug in human therapy of diabetes mellitus, promises to have a therapeutic potential against age-related hearing loss also in humans. The inventors expect an even larger efficiency combined with smaller systemic side effects by local glibenclamide treatment of the inner ear, for example by the use of already established intratympanic drug delivery systems or the ones as described above.

Example 3: Protective effect of the ΚΑτρ-blocker glibenclamide on sound trauma in C57B1/6 mice

In addition to the protective effect of glibenclamide, a specific KATP-channel blocker, on age related hearing loss in C57B1/6 mice, the systemic administration of this sulfonylurea also reduces sound-trauma induced threshold shifts thereby being protective against for various forms of acute sound trauma.

Experiments were performed on male C57B1/6 mice at the age of 8 weeks (obtained from Charles River WIGA GmbH, Germany). Auditory brainstem response (ABR) thresholds were measured in the frequency range of 2 to 45.2 kHz. After initial recordings of auditory thresholds, mice were implanted with pellets comprising the KATP-channel blocker glibenclamide at a concentration of either 27.8 μg/day or 277.8 μg/day. As a control the inventors also applied placebo pellets to age- matched C57B1/6 mice. Pellets were obtained from Innovative Research of America (Sarasota, FL).

Two weeks after pellet implantation ABR thresholds of the two groups were measured again and the animals were exposed to noise in the frequency range of 8-16 kHz at a sound pressure level of 112 dB for 120 minutes.

Another 14 days later, at the age of 12 weeks, the permanent sound induced threshold shift (PTS) were determined for both glibenclamide and vehicle treated animals. All thresholds are plotted as mean ± SEM. Fishers F-test and Student's t-test were used to assess statistical differences of mean ABR thresholds at a significance level of 0.05 (*) or 0.01 (**).

Two weeks after pellet implantation at the age of 10 weeks, no statistically significant differences in ABR thresholds were detected between the experimental and placebo groups (Fig. 10A). After noise exposure there is no difference between the glibenclamide (27.8 μg/day) and the vehicle treated animals all frequencies (Fig. 10B). Both groups show a similar severe permanent threshold shift due to the sound overexposure. The same experimental design was performed with a ten times higher dosage of glibenclamide (277.8 μg/day). Again, two weeks after pellet implantation at the age of 10 weeks no significant difference between the glibenclamide and the vehicle group was observed (Fig. 11 A). But in contrast to the lower dosage the concentration of 277.8 μg glibenclamide per day showed a statistically significant protective effect two weeks after sound overexposure (Fig 1 IB). The systemic application of the high dose of glibenclamide reduces permanent threshold shift after noise exposure in C57B1/6. Especially in the main hearing range of 11.2 to 22.6 kHz the glibenclamide treated animals show significantly better thresholds than the control group (p<0.05).

Systemic application of glibenclamide at a concentration of 277.8 μg/day significantly reduces the threshold shift of C57B1/6 mice after sound overexposure (8-16 kHz, 112 dB SPL, 120 min). Our results indicate that systemic or local treatment with glibenclamide or other sulfonylureas before or shortly after noise exposure promises to possess a cell-protective therapeutic potential against permanent hair cell loss and inner ear damage in humans.

Claims

1. An inhibitor of an ATP-sensitive potassium channel for use in the treatment of hearing loss.

2. The inhibitor of an ATP-sensitive potassium channel according to claim 1, wherein said hearing loss is age-related hearing loss (presbycusis) and/or noise-induced hearing loss (NIHL).

3. The inhibitor of an ATP-sensitive potassium channel according to claim 1 or 2, wherein said ATP-sensitive potassium channel is selected from ATP-sensitive potassium channels of the plasma membrane that comprise Ki_r6.1 and/or Ki_r6.2-type subunits as well as sulfonylurea receptors (SURl/SUR2a/b), and combinations thereof.

4. The inhibitor of an ATP-sensitive potassium channel according to claim 3, wherein said ATP- sensitive potassium channel is selected from ATP-sensitive potassium channels comprising an Ki_r6.2-type subunit.

5. The inhibitor of an ATP-sensitive potassium channel according to any of claims 1 to 4, wherein said inhibitor is selected from a sulfonylurea compound containing a central S-phenyl sulfonylurea structure, for example with at least one p-substitution on the phenyl ring, and various groups terminating the urea N' end group, such as acetohexamide, chlorpropamide, tolbutamide, tolazamide, glipizide, gliclazide, glibenclamide (glyburide), gliquidone, gly- clopyramide, and glimepiride.

6. The inhibitor of an ATP-sensitive potassium channel according to any of claims 1 to 5, wherein said inhibitor is provided locally, e.g. by local intracochlear administration, orally, topically, subcutaneously, systemically, rectally or by injection.

7. The inhibitor of an ATP-sensitive potassium channel according to any of claims 1 to 6, wherein said inhibitor is provided in form of a tablet, eardrops, subcutaneous pellet, drops, droplets, capsule, dragee, powder, suppository or gel.

8. The inhibitor of an ATP-sensitive potassium channel according to any of claims 1 to 7, wherein said inhibitor is provided in an amount of between 0.1 mg to 10 mg, preferably 0.2 mg to 5 mg, and more preferably between 0.5 mg to 2 mg per dosage.

9. The inhibitor of an ATP-sensitive potassium channel according to any of claims 1 to 8, wherein said inhibitor is provided in a dosage of between 0.2 mg/kg of body weight to 5 mg/kg of body weight per day, preferably between 0.1 mg/kg of body weight to 2 mg/kg of body weight per day.

10. The inhibitor of an ATP-sensitive potassium channel according to any of claims 1 to 9, wherein said inhibitor is administered over a period of at least between 4 weeks to 12 months or longer, such as, for example, continuously.