Patent Description:
Among the hearing diseases, sensorineural hearing loss (SNHL) is the most common type of permanent hearing loss, accounting for about <NUM>% of reported hearing loss. In most cases, SNHL results from ageing (presbycusis) or exposition either to excessive noise levels or to ototoxic chemicals, causing damage to inner and outer hair cells and leading to transient or permanent hearing loss (increase of hearing thresholds). There is currently no available pharmacological treatment to SNHL and hearing medical devices (such as hearing aids or cochlear implants) are the only solution helping the patient to hear.

Besides the destruction of cochlear hair cells, over-exposition to noise can also cause disruption of synaptic connections between inner hair cells and auditory nerve fibers of spiral ganglion neurons, known as excitotoxicity. Then, disconnected spiral ganglion neurons gradually die and disappear over time. The consequence is a cochlear synaptopathy, which may be either a hidden form of hearing loss or associated with a hearing loss. Patients suffering from cochlear synaptopathy have a speech-in-noise intelligibility deficit. In addition, cochlear synaptopathy is often associated to the occurrence of tinnitus and/or hyperacusis. However, there are currently no available treatments for cochlear synaptopathy.

Therefore, the present invention aims at providing means for treating hearing diseases such as hearing loss, cochlear synaptopathy and tinnitus, in particular the hearing loss being sensorineural hearing loss.

In the prior art, <CIT> describes the use of tetrahydropyridine derivatives to prepare medicines for treating diseases causing demyelination such as multiple sclerosis. However, there is nothing in the prior art suggesting that <NUM>-phenyl-tetrahydropyridine derivatives could lead to an improvement of the hearing function.

Yet, the inventors of the present invention have surprisingly discovered that <NUM>-phenyl-tetrahydropyridine derivatives, such as paliroden and xaliproden, lead to an improvement of the hearing function, an improvement of speech intelligibility in silence, an improvement of speech-in-noise intelligibility and exhibit a beneficial effect following noise exposure with auditory brainstem response (ABR) threshold shift reduction.

The present invention relates to a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof, for use in the treatment of a hearing disease in a subject, wherein formula (I) is:
<CHM>
wherein.

Preferably, at least one of R<NUM> and R<NUM> is a hydrogen atom, more preferably R<NUM> and R<NUM> are each a hydrogen atom.

Preferably, A is a biphenyl radical or a non-substituted <NUM>-naphthyl radical.

Preferably, the salt is a hydrochloride salt or a fumarate salt of the compound of formula (I).

Advantageously, said compound is administered to the subject by oral route or by trans-tympanic route. More advantageously, said compound is administered to the subject by oral route or by trans-tympanic route, wherein the administration by trans-tympanic route consists in an injection between the eardrum and the round window by means of a needle which crosses the eardrum. Even more preferably, the compound is administered to the subject by trans-tympanic route, wherein the administration by trans-tympanic route consists in an injection between the eardrum and the round window by means of a needle which crosses the eardrum.

Advantageously, said compound is administered by trans-tympanic route at a dose ranging from <NUM>µg to <NUM>, between once a month and once every <NUM> months. Preferably, said administration by trans-tympanic route consists in an injection between the eardrum and the round window by means of a needle which crosses the eardrum.

Preferably, the hearing disease is selected from the group consisting of unilateral or bilateral hearing loss, unilateral or bilateral tinnitus, unilateral or bilateral hyperacusis, hidden hearing loss such as cochlear synaptopathy associated with a normal threshold, speech-intelligibility deficit, unilateral or bilateral temporary auditory threshold shift, central auditory processing disorder, unilateral or bilateral auditory recruitment, acoustic neuroma, single sided deafness, excitotoxicity, ototoxicity such as drug-induced ototoxicity and any combination thereof. More preferably, the hearing disease is selected from the group consisting of unilateral and bilateral hearing loss such as a unilateral and bilateral sensorineural hearing loss, unilateral or bilateral tinnitus, unilateral or bilateral hyperacusis, hidden hearing loss such as cochlear synaptopathy associated with a normal threshold, and speech-intelligibility deficit.

Preferably, the hearing disease is a unilateral or bilateral sensorineural hearing loss selected from the group consisting of unilateral or bilateral noise-induced sensorineural hearing loss, unilateral or bilateral inflammation-induced sensorineural hearing loss, unilateral or bilateral sudden idiopathic sensorineural hearing loss, unilateral or bilateral ototoxic chemicals-induced sensorineural hearing loss and unilateral or bilateral aged-induced sensorineural hearing loss such as presbycusis. More preferably, the hearing disease is a unilateral or bilateral sensorineural hearing loss selected from the group consisting of unilateral or bilateral noise-induced sensorineural hearing loss and unilateral or bilateral aged-induced sensorineural hearing loss.

Preferably, the hearing disease is a unilateral or bilateral inflammation-induced sensorineural hearing loss caused by a chronic inflammatory disease, more preferably said chronic inflammatory disease is selected from the group consisting of diabetes, chronic kidney disease, inflammatory bowel diseases and rheumatoid arthritis.

Preferably, the hearing disease is a unilateral or bilateral hearing loss with a tonal audiometric threshold above <NUM> dB at <NUM> contiguous frequencies optionally associated with unilateral or bilateral tinnitus. More preferably, the hearing disease is a unilateral or bilateral hearing loss with a tonal audiometric threshold from <NUM> dB to <NUM> dB at <NUM> contiguous frequencies optionally associated with unilateral or bilateral tinnitus, the tonal audiometric threshold being measured by auditory brainstem response or pure-tone audiometry.

Preferably, the hearing disease is selected from the group consisting of labyrinthine dysfunction, vestibular neuronitis, acute unilateral vestibulopathy, benign paroxysmal positional vertigo, vertigo of central origin, Meniere's disease, Meniere's syndrome and any combination thereof.

In one embodiment, said subject is wearing at least one hearing device.

Advantageously, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject during a cochlear surgery, for example during a cochlear implant surgery.

Advantageously, said subject is a mammalian animal with an eardrum, preferably said mammalian animal with an eardrum is selected from the group consisting of a human, a cat, a dog and a non-human primate animal, more preferably said mammalian animal with an eardrum is a dog.

The present invention also relates to a pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof according to the invention, and at least one pharmaceutically acceptable excipient selected from the group consisting of poloxamers, polyethoxylated castor oil, phospholipids, triglycerides and any combination thereof.

The present invention also relates to a pharmaceutical transtympanic composition comprising a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof according to the invention, and a combination of a mixture of polyoxyethylated triglycerides and poloxamers, said pharmaceutical composition being a thermoreversible gel.

The present invention further relates to a pharmaceutical composition for use in the treatment of a hearing disease in a subject, said pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof according to the invention, and at least one pharmaceutically acceptable excipient. Preferably, said hearing disease is as defined in the present description.

In one embodiment, the trans-tympanic administration consists in the administration of an active agent or a composition in the external ear canal, wherein said active agent or the active agent of said composition is able to cross the eardrum, for example by diffusion. The formulation of the active agent or of the composition may be any formulation suitable for administration in the external ear canal. Preferably, the formulation of the active agent or of the composition is selected from the group consisting of a semi-solid formulation, gel formulation and liquid formulation. The liquid formulation may be selected from the group consisting of a suspension, an emulsion and a solution. The gel formulation may be selected from the group consisting of a thermoreversible gel, hydrogel, glycerin-based gel, conjugated gal, crosslinked gel and alginate-based gel. The formulation of the active agent or of the composition may be an osmotic dosage formulation, a diffusion dosage formulation or an erodible formulation. More preferably, the formulation of the active agent or of the composition is selected from the group consisting of a gel formulation and a liquid formulation, for example an ear gel or ear drops.

In another embodiment, the trans-tympanic administration consists in an injection between the eardrum and the round window by means of a needle which crosses the eardrum. After the trans-tympanic injection, the injected substance diffuses through the round window to the cochlea. Preferably, the gauge of the needle is from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, even more preferably from <NUM> to <NUM>, even more preferably from <NUM> to <NUM>. In particular, the gauge of the needle may be selected from the group consisting of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. More preferably, the needle is a <NUM> gauge-needle (=<NUM> needle). Advantageously, the needle is selected from the group consisting of a trans-tympanic injection needle and a spinal needle. More advantageously, the needle is a trans-tympanic injection needle. For example, the needle may be the product "MediPlast ENT, Otology, Trans- Intratympanic Injection Needle, Single Use With Luer-lock <NUM> x <NUM>" marketed by company Mediplast®. Preferably, the formulation of the active agent or of the composition is selected from the group consisting of a semi-solid formulation, gel formulation and liquid formulation. The liquid formulation may be selected from the group consisting of a suspension, an emulsion and a solution. The solution may be a mucoadhesive solution, in particular a lipid-based mucoadhesive solution. The gel formulation may be selected from the group consisting of a thermoreversible gel, hydrogel, glycerin-based gel, conjugated gal, crosslinked gel and alginate-based gel. The formulation of the active agent or of the composition may be an osmotic dosage formulation, a diffusion dosage formulation or an erodible formulation. More preferably, the formulation of the active agent or of the composition is selected from the group consisting of a gel formulation and a liquid formulation. Even more preferably, the formulation of the active agent or of the composition is selected from the group consisting of a thermoreversible gel and a solution; the solution is in particular a mucoadhesive solution, more particularly a lipid-based mucoadhesive solution.

"Treating" or "treatment" refers to any action which makes it possible to prevent, delay, reduce in severity and/or frequency or suppress at least one symptom associated with a pathological condition, or to prevent, slow down or suppress the underlying cause of a pathological condition, or the improvement or remediation of damage. In one embodiment, "treatment" refers to a curative treatment. In another embodiment, "treatment" refers to a preventive treatment. In another embodiment, "treatment" refers to a preventive and/or curative treatment.

"Unilateral or bilateral" refers to a hearing disease that may affect either one ear (this is a unilateral hearing disease) or both ears (this is a bilateral hearing disease). A unilateral hearing disease may affect either the right ear or the left ear.

"Xaliproden" refers to the chemical molecule <NUM>-[<NUM>-(<NUM>-naphthyl)ethyl]-<NUM>-(<NUM>-trifluoromethylphenyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydropyridine, of the following chemical formula:
<CHM>.

The present invention relates to a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof, for use in the treatment of a hearing disease in a subject.

The present invention also relates to a method of treating a hearing disease by administering to a subject in need thereof an effective amount of a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof.

Any references to methods of treatment in this description are to be interpreted as references to the compounds, pharmaceutical compositions or medicaments of the present invention for use in those.

The present invention also relates to the use of a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof for the treatment of a hearing disease in a subject.

Preferably, at least one of R<NUM> and R<NUM> is a hydrogen atom. More preferably, R<NUM> and R<NUM> are each a hydrogen atom.

According to one embodiment, in the above formula (I):.

According to a preferred embodiment, formula (I) is:
<CHM>
According to this embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is <NUM>-[<NUM>-(<NUM>-biphenylyl)ethyl]-<NUM>-(<NUM>-trifluoromethylphenyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydropyridine, also named paliroden, or a pharmaceutically acceptable salt and/or solvate thereof.

According to another preferred embodiment, formula (I) is:
<CHM>
According to this embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is <NUM>-[<NUM>-(<NUM>-naphthyl)ethyl]-<NUM>-(<NUM>-trifluoromethylphenyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydropyridine, also named xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof.

Advantageously, the salt is selected from the group consisting of a hydrochloride salt, a fumarate salt and a besylate salt of the compound of formula (I). More advantageously, the salt is selected from the group consisting of a hydrochloride salt and a fumarate salt of the compound of formula (I).

According to a preferred embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is a fumarate salt of <NUM>-[<NUM>-(<NUM>-biphenylyl)ethyl]-<NUM>-(<NUM>-trifluoromethylphenyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydropyridine, also named paliroden fumarate.

According to another preferred embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is a hydrochloride salt of <NUM>-[<NUM>-(<NUM>-naphthyl)ethyl]-<NUM>-(<NUM>-trifluoromethylphenyl)-<NUM>,<NUM>,<NUM>,<NUM>-tetrahydropyridine, also named xaliproden hydrochloride.

According to the present invention, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof as defined above is for use in the treatment of a hearing disease in a subject.

According to one embodiment, the hearing disease is selected from the group consisting of unilateral or bilateral hearing loss, unilateral or bilateral tinnitus, hidden hearing loss such as cochlear synaptopathy associated with a normal threshold, otosclerosis such as non-obliterative and obliterative otosclerosis involving oval window and cochlear otosclerosis, acoustic neuroma, single sided deafness, ototoxicity such as drug-induced ototoxicity, labyrinthine dysfunction, vestibular neuronitis, excitotoxicity, autoimmune inner ear disease, acute unilateral vestibulopathy, benign paroxysmal positional vertigo, vertigo of central origin, Meniere's disease, Meniere's syndrome, unilateral or bilateral auditory recruitment, diplacusis, unilateral or bilateral hyperacusis, unilateral or bilateral temporary auditory threshold shift, central auditory processing disorder and any combination thereof.

Advantageously, the unilateral or bilateral hearing loss is selected from the group consisting of unilateral or bilateral sensorineural hearing loss, unilateral or bilateral cochlear synaptopathy associated with an increased threshold, and unilateral or bilateral mixed conductive and sensorineural hearing loss. Preferably, the unilateral or bilateral sensorineural hearing loss is selected from the group consisting of unilateral or bilateral noise-induced sensorineural hearing loss, unilateral or bilateral inflammation-induced sensorineural hearing loss, unilateral or bilateral sudden idiopathic sensorineural hearing loss, unilateral or bilateral ototoxic chemicals-induced sensorineural hearing loss and unilateral or bilateral aged-induced sensorineural hearing loss such as presbycusis. More preferably, the unilateral or bilateral sensorineural hearing loss is selected from the group consisting of unilateral or bilateral noise-induced sensorineural hearing loss, unilateral or bilateral aged-induced sensorineural hearing loss such as presbycusis, and unilateral or bilateral inflammation-induced sensorineural hearing loss. The unilateral or bilateral inflammation-induced sensorineural hearing loss may be induced by a chronic inflammatory disease. Even more preferably, the unilateral or bilateral sensorineural hearing loss is selected from the group consisting of unilateral or bilateral noise-induced sensorineural hearing loss and unilateral or bilateral aged-induced sensorineural hearing loss such as presbycusis. Preferably, the unilateral or bilateral cochlear synaptopathy associated with an increased threshold is selected from the group consisting of unilateral or bilateral noise-induced cochlear synaptopathy associated with an increased threshold, unilateral or bilateral inflammation-induced cochlear synaptopathy associated with an increased threshold, and unilateral or bilateral aged-induced cochlear synaptopathy associated with an increased threshold. In particular, the unilateral or bilateral noise-induced cochlear synaptopathy associated with an increased threshold may be induced by chronic noise exposure. In particular, the unilateral or bilateral inflammation-induced cochlear synaptopathy associated with an increased threshold may be induced by a chronic inflammatory disease.

According to a preferred embodiment, the hearing disease is selected from the group consisting of unilateral and bilateral sensorineural hearing loss, unilateral and bilateral cochlear synaptopathy associated with an increased threshold, unilateral or bilateral tinnitus, cochlear synaptopathy associated with a normal threshold, acoustic neuroma, sudden idiopathic hearing loss, drug-induced hearing loss, single sided deafness, excitotoxicity, ototoxicity, drug-induced ototoxicity, labyrinthine dysfunction, vestibular neuronitis, acute unilateral vestibulopathy, benign paroxysmal positional vertigo, vertigo of central origin, Meniere's disease and Meniere's syndrome.

According to a preferred embodiment, the hearing disease is selected from the group consisting of unilateral or bilateral hearing loss, unilateral or bilateral tinnitus, hidden hearing loss such as cochlear synaptopathy associated with a normal threshold, otosclerosis such as non-obliterative and obliterative otosclerosis involving oval window and cochlear otosclerosis, acoustic neuroma, single sided deafness, ear infection, ototoxicity such as drug-induced ototoxicity, excitotoxicity, acute unilateral vestibulopathy, vestibular neuronitis and any combination thereof.

According to a more preferred embodiment, the hearing disease is selected from the group consisting of unilateral or bilateral hearing loss, unilateral or bilateral tinnitus, hidden hearing loss such as cochlear synaptopathy associated with a normal threshold, single sided deafness, acute unilateral vestibulopathy, vestibular neuronitis, unilateral or bilateral auditory recruitment, diplacusis, unilateral or bilateral hyperacusis, unilateral or bilateral temporary auditory threshold shift, central auditory processing disorder and any combination thereof.

According to a more preferred embodiment, the hearing disease is selected from the group consisting of unilateral or bilateral tinnitus, unilateral or bilateral auditory recruitment, diplacusis, unilateral or bilateral hyperacusis, unilateral or bilateral temporary auditory threshold shift, central auditory processing disorder and any combination thereof. These hearing diseases correspond to those of the classes H93. <NUM> and H93. <NUM> of the International Classification of Diseases ICD-<NUM>, version <NUM>.

According to a more preferred embodiment, the hearing disease is selected from the group consisting of unilateral or bilateral hearing loss, unilateral or bilateral tinnitus, hidden hearing loss such as cochlear synaptopathy associated with a normal threshold and any combination thereof.

According to a more preferred embodiment, the hearing disease is selected from the group consisting of unilateral or bilateral hearing loss, unilateral or bilateral tinnitus, hidden hearing loss such as cochlear synaptopathy associated with a normal threshold and any combination thereof, wherein the unilateral or bilateral hearing loss is selected from the group consisting of unilateral or bilateral sensorineural hearing loss, unilateral or bilateral mixed conductive and sensorineural hearing loss, and unilateral or bilateral cochlear synaptopathy associated with an increased threshold. Preferably, the hearing disease is a unilateral or bilateral hearing loss, wherein the unilateral or bilateral hearing loss is selected from the group consisting of <NUM>) a unilateral or bilateral sensorineural hearing loss, such as a noise-induced sensorineural hearing loss, or an aged-induced sensorineural hearing loss such as presbycusis, and <NUM>) a unilateral or bilateral cochlear synaptopathy associated with an increased threshold, such as a noise-induced cochlear synaptopathy associated with an increased threshold or an aged-induced cochlear synaptopathy associated with an increased threshold.

According to a more preferred embodiment, the hearing disease is selected from the group consisting of unilateral or bilateral sensorineural hearing loss such as noise-induced sensorineural hearing loss or aged-induced sensorineural hearing loss such as presbycusis, unilateral or bilateral cochlear synaptopathy associated with an increased threshold, unilateral or bilateral tinnitus, hidden hearing loss such as cochlear synaptopathy associated with a normal threshold and any combination thereof.

According to a more preferred embodiment, the hearing disease is selected from the group consisting of unilateral or bilateral sensorineural hearing loss such as noise-induced sensorineural hearing loss or aged-induced sensorineural hearing loss such as presbycusis, unilateral or bilateral tinnitus and any combination thereof.

According to a more preferred embodiment, the hearing disease is a combination of a unilateral or bilateral sensorineural hearing loss, such as noise-induced sensorineural hearing loss or aged-induced sensorineural hearing loss, and unilateral or bilateral tinnitus.

According to a more preferred embodiment, the hearing disease is a combination of unilateral or bilateral tinnitus and a hidden hearing loss such as cochlear synaptopathy associated with a normal threshold.

According to a more preferred embodiment, the hearing disease is a combination of a unilateral or bilateral sensorineural hearing loss, such as noise-induced sensorineural hearing loss or aged-induced sensorineural hearing loss, and a hidden hearing loss such as cochlear synaptopathy associated with a normal threshold.

According to a more preferred embodiment, the hearing disease is a combination of a unilateral or bilateral sensorineural hearing loss, such as noise-induced sensorineural hearing loss or aged-induced sensorineural hearing loss, and a unilateral or bilateral cochlear synaptopathy associated with an increased threshold.

According to a more preferred embodiment, the hearing disease is a combination of a unilateral or bilateral tinnitus, and a unilateral or bilateral cochlear synaptopathy associated with an increased threshold.

According to a more preferred embodiment, the hearing disease is a unilateral or bilateral sensorineural hearing loss, preferably the unilateral or bilateral sensorineural hearing loss is selected from a noise-induced sensorineural hearing loss and an aged-induced sensorineural hearing loss such as presbycusis.

According to a more preferred embodiment, the hearing disease is unilateral or bilateral tinnitus.

According to a more preferred embodiment, the hearing disease is a hidden hearing loss such as cochlear synaptopathy associated with a normal threshold.

According to a more preferred embodiment, the hearing disease is a unilateral or bilateral cochlear synaptopathy associated with an increased threshold.

Preferably, the hearing disease according to the invention is not induced by a decrease or an increase in TGF-β (Transforming Growth Factor β).

Preferably, the hearing disease according to the invention is not induced by a demyelinating disease nor by a demyelination of the auditory nerve.

In one embodiment, the hearing disease according to the invention is an inflammation-induced unilateral or bilateral sensorineural hearing loss caused by a chronic inflammatory disease, preferably said chronic inflammatory disease is selected from the group consisting of diabetes preferably type <NUM> diabetes, chronic kidney disease, inflammatory bowel diseases and rheumatoid arthritis.

In one embodiment, the hearing disease according to the invention is an inflammation-induced unilateral or bilateral cochlear synaptopathy associated with an increased threshold caused by a chronic inflammatory disease, preferably said chronic inflammatory disease is selected from the group consisting of diabetes preferably type <NUM> diabetes, chronic kidney disease, inflammatory bowel diseases and rheumatoid arthritis.

In another embodiment, the hearing disease according to the invention is a sensorineural hearing loss that is not caused by diabetes, chronic kidney disease, inflammatory bowel diseases or rheumatoid arthritis, preferably the hearing disease according to the invention is a sensorineural hearing loss that is not caused by a chronic inflammatory disease.

In another embodiment, the hearing disease according to the invention is a unilateral or bilateral cochlear synaptopathy associated with an increased threshold that is not caused by diabetes, chronic kidney disease, inflammatory bowel diseases or rheumatoid arthritis, preferably the hearing disease according to the invention is a unilateral or bilateral cochlear synaptopathy associated with an increased threshold that is not caused by a chronic inflammatory disease.

According to an embodiment, the hearing disease is a unilateral or bilateral hearing loss with a tonal audiometric threshold above <NUM> dB at <NUM> contiguous frequencies, optionally associated with unilateral or bilateral tinnitus, the tonal audiometric threshold being measured by auditory brainstem response or pure-tone audiometry. According to a preferred embodiment, the hearing disease is a unilateral or bilateral hearing loss with a tonal audiometric threshold from <NUM> dB to <NUM> dB at <NUM> contiguous frequencies, optionally associated with unilateral or bilateral tinnitus, the tonal audiometric threshold being measured by auditory brainstem response or pure-tone audiometry. According to another embodiment, the hearing disease is a unilateral or bilateral hearing loss with a tonal audiometric threshold greater than or equal to <NUM> dB at <NUM> contiguous frequencies, optionally associated with unilateral or bilateral tinnitus, the tonal audiometric threshold being measured by auditory brainstem response or pure-tone audiometry. According to preferred embodiment, the hearing disease is a bilateral hearing loss with a tonal audiometric threshold greater than or equal to <NUM> dB at <NUM> contiguous frequencies, the tonal audiometric threshold being measured by auditory brainstem response or pure-tone audiometry. According to another embodiment, the hearing disease is a unilateral or bilateral hearing loss with a tonal audiometric threshold greater than <NUM> dB at <NUM> contiguous frequencies, optionally associated with unilateral or bilateral tinnitus, the tonal audiometric threshold being measured by auditory brainstem response or pure-tone audiometry. According to preferred embodiment, the hearing disease is a unilateral hearing loss with a tonal audiometric threshold greater than or equal to <NUM> dB at <NUM> contiguous frequencies, associated with unilateral or bilateral tinnitus, the tonal audiometric threshold being measured by auditory brainstem response or pure-tone audiometry.

Advantageously, the subject is wearing at least one hearing device. The subject may be wearing one hearing device. The subject may also be wearing two hearing devices. Indeed, among other advantages, administering a compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, to a subject wearing at least one hearing device, leads to an improvement of speech-in-noise intelligibility.

According to another embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject during a cochlear surgery, for example during a cochlear implant surgery. Indeed, administering a compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, to a subject during a cochlear surgery, for example during a cochlear implant surgery, allowing better preservation of residual hearing and/or facilitating rehabilitation post-surgery (better and/or faster post-surgery rehabilitation). Indeed, cochlear implant surgery is generally safe; however, risks of cochlear implantation include loss of residual hearing.

The inventors have surprisingly discovered that administering a compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, leads to an improvement of the hearing function materialized by a decrease in pure-tone audiometric threshold and/or ABR threshold shift of at least <NUM> dB at three contiguous frequencies.

In addition, the inventors have surprisingly discovered that administering a compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, leads to an improvement of speech intelligibility in silence materialized by a <NUM>% improvement in word recognition score (number of correctly identified words in a list of <NUM> words presented at <NUM> dB above audiometric threshold).

In addition, the inventors have surprisingly discovered that administering a compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, leads to an improvement of speech-in-noise intelligibility materialized by a reduction of <NUM> dB in the SNR (signal-to-noise ratio) necessary to achieve <NUM>% correct word understanding.

Furthermore, the inventors have surprisingly discovered that administering a compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, exhibits a beneficial effect following noise exposure with ABR threshold shifts reduction.

The compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, may be administered to the subject by any suitable administration route. Preferably, the compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, is administered to the subject by any administration route suitable for allowing said compound to reach the inner ear. More preferably, the route suitable for allowing said compound to reach the inner ear is a route selected from the group consisting of a systemic route and a local route. The systemic route may be selected from the group consisting of oral route, intraperitoneal route, intravenous route, intramuscular route, intraarterial route and subcutaneous route. The local route may be selected from the group consisting of external ear route on the eardrum, trans-tympanic route, intrabullar route, intracochlear route and round window niche route.

Thus, the compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, may be administered to the subject by an administration route selected from the group consisting of external ear route on the eardrum, trans-tympanic route, intrabullar route, intracochlear route, round window niche route, oral route, intraperitoneal route, intravenous route, intramuscular route, intraarterial route and subcutaneous route.

Advantageously, the compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject by trans-tympanic route or by oral route. More advantageously, the administration by trans-tympanic route consists in an injection between the eardrum and the round window by means of a needle which crosses the eardrum.

In one embodiment, the compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject by trans-tympanic route. In a preferred embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject by trans-tympanic route in one ear, for example the right ear or the left ear. In another preferred embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject by trans-tympanic route in both ears. Advantageously, the administration by trans-tympanic route consists in an injection between the eardrum and the round window by means of a needle which crosses the eardrum.

In another embodiment, the compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject by oral route. The oral route has the advantages of promoting compliance by the subject and facilitating administration, especially when the subject is a non-human mammal, such as a cat or dog.

According to an embodiment, the compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject by trans-tympanic route at a dose per ear ranging from <NUM>µg to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, even more preferably from <NUM> to <NUM>, even more preferably about <NUM>. Advantageously, the administration by trans-tympanic route consists in an injection between the eardrum and the round window by means of a needle which crosses the eardrum. According to an embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject by trans-tympanic route at a dose per ear ranging from <NUM>µg to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, even more preferably from <NUM> to <NUM>, even more preferably about <NUM>. According to an embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject by trans-tympanic route at a dose per ear ranging from <NUM>µg to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, even more preferably from <NUM> to <NUM>, even more preferably about <NUM>. According to an embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject by trans-tympanic route at a dose per ear ranging from <NUM>µg to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, even more preferably from <NUM> to <NUM>, even more preferably about <NUM>. According to an embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject by trans-tympanic route at a dose per ear of about <NUM>µg, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>,<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> or <NUM>. Said dose may be administered in one ear, for example the right ear or the left ear, between once a month and once every <NUM> months. Said dose may also be administered in both ears between once a month and once every <NUM> months. Advantageously, the administration by trans-tympanic route consists in an injection between the eardrum and the round window by means of a needle which crosses the eardrum.

According to an embodiment, the compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof is administered to the subject by oral route at a dose ranging from <NUM>µg to <NUM>, preferably from <NUM> to <NUM>, more preferably from <NUM> to <NUM>, even more preferably about <NUM>, said dose being administered between twice a day and once a week, advantageously said dose being administered once a day. This oral dose may in particular be administered to a human.

According to an embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is administered by oral route at a dose ranging from <NUM>/kg/day to <NUM>/kg/day, preferably from <NUM>/kg/day to <NUM>/kg/day, more preferably about <NUM>/kg/day, said dose being administered between twice a day and once a week, advantageously said dose being administered once a day. This oral dose may in particular be administered to a non-human subject.

According to an embodiment, the compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof is administered in a micronized form.

According to an embodiment, the compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof is administered in an atomized form.

In one embodiment, the subject is a mammalian animal with an eardrum. In a preferred embodiment, said mammalian animal with an eardrum is a human. In another preferred embodiment, said mammalian animal with an eardrum is non-human, preferably a non-human mammalian animal with an eardrum selected from the group consisting of a cat, a dog, a horse and a non-human primate such as a monkey.

In a more preferred embodiment, the subject is a dog.

In a more preferred embodiment, the subject is a human, advantageously a human over <NUM> years.

In a more preferred embodiment, the subject is diabetic (type <NUM> diabetes or type <NUM> diabetes, preferably type <NUM> diabetes).

The present invention also relates to a pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof as defined above and at least one pharmaceutically acceptable excipient selected from the group consisting of poloxamers, polyethoxylated castor oil, phospholipids, triglycerides and any combination thereof.

The present invention also relates to a pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof as defined above, wherein said pharmaceutical composition is a thermoreversible gel, and preferably, said pharmaceutical composition is a pharmaceutical trans-tympanic composition.

Advantageously, said pharmaceutical composition is a pharmaceutical trans-tympanic composition, i.e. a pharmaceutical composition intended to be administered by trans-tympanic route.

In one embodiment, said pharmaceutical composition comprises from <NUM> to <NUM> of the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof per mL of said pharmaceutical composition.

In one embodiment, said pharmaceutical composition comprises from <NUM> to <NUM> of paliroden or a pharmaceutically acceptable salt and/or solvate thereof per mL of said pharmaceutical composition.

In one embodiment, said pharmaceutical composition comprises from <NUM> to <NUM> of xaliproden or a pharmaceutically acceptable salt and/or solvate thereof per mL of said pharmaceutical composition.

According to one embodiment, the at least one pharmaceutically acceptable excipient is selected from the group consisting of poloxamers, polyethoxylated castor oil, triglycerides, combinations of phospholipids and triglycerides, and any combination thereof.

According to one embodiment, the at least one pharmaceutically acceptable excipient is selected from the group consisting of poloxamers, triglycerides, and any combination thereof. According to one embodiment, the at least one pharmaceutically acceptable excipient is selected from the group consisting of poloxamers, triglycerides, combinations of phospholipids and triglycerides, and any combination thereof. In one embodiment, the triglycerides are polyoxyethylated.

According to one embodiment, the at least one pharmaceutically acceptable excipient is at least one poloxamer, preferably said poloxamer being selected from the group consisting of poloxamer <NUM>, poloxamer <NUM> and any combination thereof.

According to a preferred embodiment, the at least one pharmaceutically acceptable excipient is a mixture of polyoxyethylated triglycerides, obtained by reacting castor oil with ethylene oxide in a molar ratio of <NUM>:<NUM>. For example, the at least one pharmaceutically acceptable excipient may be the commercialized product Cremophor EL®, which<NPL>.

According to a preferred embodiment, the at least one pharmaceutically acceptable excipient is a combination of poloxamers and a mixture of polyoxyethylated triglycerides, preferably a mixture of polyoxyethylated triglycerides obtained by reacting castor oil with ethylene oxide in a molar ratio of <NUM>:<NUM> such as Cremophor EL®. More preferably, the pharmaceutical composition comprising said excipients is a thermoreversible gel.

According to a preferred embodiment, the at least one pharmaceutically acceptable excipient is a combination of poloxamer <NUM> and a mixture of polyoxyethylated triglycerides, preferably a mixture of polyoxyethylated triglycerides obtained by reacting castor oil with ethylene oxide in a molar ratio of <NUM>:<NUM> such as Cremophor EL®.

According to another preferred embodiment, the at least one pharmaceutically acceptable excipient is a combination of poloxamer <NUM>, poloxamer <NUM> and a mixture of polyoxyethylated triglycerides, preferably a mixture of polyoxyethylated triglycerides obtained by reacting castor oil with ethylene oxide in a molar ratio of <NUM>:<NUM> such as Cremophor EL®.

According to another preferred embodiment, the at least one pharmaceutically acceptable excipient comprises or consists of a combination of:.

wherein the percentages are expressed in relation to the total volume of the pharmaceutical composition.

According to one embodiment, the at least one pharmaceutically acceptable excipient is a combination of phospholipids and triglycerides. Preferably, said combination of phospholipids and triglycerides comprises phosphatidylcholine and medium-chain triglycerides such as caprylic/capric triglycerides. For example, said combination of phospholipids and triglycerides may be the commercialized product Phosal@ <NUM> MCT.

According to an embodiment, the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof is in a micronized form in the pharmaceutical composition.

According to an embodiment, the compound of formula (I), for example paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof is in an atomized form in the pharmaceutical composition.

According to an embodiment, said pharmaceutical composition is a sustained release composition.

In one embodiment, said pharmaceutical composition has a viscosity from <NUM> to <NUM> mPa. In a preferred embodiment, said pharmaceutical composition has a viscosity from <NUM> to <NUM> mPa. s, preferably from <NUM> to <NUM> mPa. s, preferably from <NUM> to <NUM> mPa. s, more preferably about <NUM> mPa. In another preferred embodiment, said pharmaceutical composition has a viscosity from <NUM> to <NUM> mPa. s, preferably from <NUM> to <NUM> mPa. s, more preferably about <NUM> mPa. The viscosity is the dynamic viscosity, measured with a viscometer using the capillary tube method, at <NUM>.

Such a pharmaceutical composition allows a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof, such as paliroden or xaliproden, to be administered by trans-tympanic administration, in particular by injection between the eardrum and the round window by means of a needle which crosses the eardrum. This trans-tympanic administration, in particular by injection between the eardrum and the round window by means of a needle which crosses the eardrum, has the advantage of allowing a higher concentration of the compound of formula (I), such as paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, in the inner ear fluid to be reached (above <NUM> ng/mL, i.e. approximately <NUM>), than the oral administration, while reducing the systemic exposure compared to the oral administration.

The administration of a mucoadhesive composition, by trans-tympanic route, in particular by injection between the eardrum and the round window by means of a needle which crosses the eardrum, allows said composition to adhere to a mucous membrane of the ear, in particular to the mucous membrane of the middle ear. Then, the active agent diffuses through the round window to the cochlea. Thus, the muco-adhesive feature of the composition ensures that the active agent reaches the cochlea. Excipients such as polyethoxylated castor oil, triglycerides and combinations of triglyderides and phospholipids allow to confer the mucoadhesive feature to a composition.

Without wishing to be bound by any theory, it seems that the viscosity of the pharmaceutical composition according to the invention is involved in allowing this composition to remain longer in the middle ear after injection between the eardrum and the round window by means of a needle which crosses the eardrum. Therefore, it allows the compound of formula (I), such as paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, to diffuse for a longer through the round window to the cochlea, ensuring a greater amount of the compound of formula (I), such as paliroden or xaliproden, or a pharmaceutically acceptable salt and/or solvate thereof, to reach the cochlea.

The present invention also relates to a pharmaceutical composition for use in the treatment of a hearing disease in a subject, said pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof as defined above and at least one pharmaceutically acceptable excipient.

The present invention also relates to a method of treating a hearing disease by administering to a subject in need thereof an effective amount of a pharmaceutical composition, said pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof as defined above and at least one pharmaceutically acceptable excipient. The present invention also relates to the use of a pharmaceutical composition for the manufacture of a medicament for the treatment of a hearing disease in a subject, said pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof as defined above.

The present invention also relates to the use of a pharmaceutical composition for the treatment of a hearing disease in a subject, said pharmaceutical composition comprising a compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof as defined above.

Advantageously, said hearing disease is as defined above in the present description.

Said pharmaceutical composition may be administered to the subject by any suitable administration route. Preferably, said pharmaceutical composition is administered to the subject by any administration route suitable for allowing the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof to reach the inner ear. More preferably, the route suitable for allowing the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof to reach the inner ear is a route selected from the group consisting of a systemic route and a local route. The systemic route may be selected from the group consisting of oral route, intraperitoneal route, intravenous route, intramuscular route, intraarterial route and subcutaneous route. The local route may be selected from the group consisting of external ear route on the eardrum, trans-tympanic route, intrabullar route, intracochlear route and round window niche route.

Thus, said pharmaceutical composition may be administered to the subject by an administration route selected from the group consisting of external ear route on the eardrum, trans-tympanic route, intrabullar route, intracochlear route, round window niche route, oral route, intraperitoneal route, intravenous route, intramuscular route, intraarterial route and subcutaneous route.

Advantageously, said pharmaceutical composition is administered to the subject by trans-tympanic route or by oral route. More advantageously, the administration by trans-tympanic route consists in an injection between the eardrum and the round window by means of a needle which crosses the eardrum.

According to a first embodiment, said pharmaceutical composition is administered to the subject by trans-tympanic route. Preferably, said pharmaceutical composition is administered to the subject by trans-tympanic route in one ear, for example the right ear or the left ear. Alternatively, said pharmaceutical composition is administered to the subject by trans-tympanic route in both ears. Advantageously, the administration by trans-tympanic route consists in an injection between the eardrum and the round window by means of a needle which crosses the eardrum. Preferably, the pharmaceutical composition that is administered to the subject by trans-tympanic route, is as defined above in part "pharmaceutical composition" of the present description.

According to a second embodiment, said pharmaceutical composition is administered to the subject by oral route. Preferably, the pharmaceutical composition that is administered to the subject by oral route is in a galenic form selected from the group consisting of drinkable suspensions, granules, capsules and tablets. Preferably, the at least one pharmaceutically acceptable excipient of the pharmaceutical composition that is administered to the subject by oral route is selected from the group consisting of lactose monohydrate, microcrystalline cellulose, corn starch, citric acid, hypromellose, croscarmellose sodium, magnesium stearate, methylcellulose and arabic gum. More preferably, the at least one pharmaceutically acceptable excipient of the pharmaceutical composition that is administered to the subject by oral route comprises a combination of:.

The oral galenic form may be coated, for example with an aqueous film coating system comprising polyvinyl alcohol, such as Opadry® II (for example Opadry® II 32K28708 white).

The administration to a subject by oral route of a pharmaceutical composition comprising a compound of formula (I), such as paliroden or xaliproden, or pharmaceutically acceptable salt and/or solvate thereof allows said compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof, such as paliroden or xaliproden, to reach concentrations in the inner ear fluid that are higher than <NUM> ng/mL (i.e. about <NUM>).

All the features described above for the compound for use (part "compound for use") and all the features described above for the pharmaceutical composition (part "pharmaceutical composition") apply mutatis mutandis for the pharmaceutical composition for use. In particular, all the features described above regarding the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof, the indications, the administration (notably the administration routes, the doses, the form of the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof, the subject), the concentration of the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof in the pharmaceutical composition, the excipients, the form of the compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof in the pharmaceutical composition, the sustained release feature and the viscosity of the pharmaceutical composition, apply mutatis mutandis for the pharmaceutical composition for use.

Two compositions were prepared: composition A and composition B. Composition A is an aqueous solution comprising:.

Composition B is an aqueous solution comprising:.

Composition A and composition B were administered to male Wistar rats (<NUM> animals per active agent and timepoint), as described below.

Composition A was administered to <NUM> male Wistar rats, once, at time T0, via oral injection by gavage, at a dose of <NUM> of composition A per kilogram of the animal, i.e. a dose of <NUM> of paliroden fumarate per kilogram of the animal. The concentration of paliroden in rats plasma and in rats inner ear fluid (IEF) was measured at <NUM> timepoints, <NUM> rats being used at each timepoint for the concentration measurements (in the plasma and optionally in the IEF). The timepoints are T0+1hour, T0+2hours, T0+4hours, T0+6hours, T0+8hours and T0+24hours for the concentration measurement in the rats plasma. The timepoints are T0+2hours, T0+4hours and T0+24hours for the concentration measurement in the rats inner ear fluid, as part of a terminal procedure including cochlea sampling and inner ear fluids collection from both ears of the rats. Bioanalytical methods were validated in both matrices (lithium heparin plasma and inner ear fluid) with a range of <NUM> to <NUM> ng/mL in plasma and <NUM> to <NUM> ng/mL in inner ear fluids.

Composition B was administered to <NUM> others male Wistar rats, once, at time T0, via oral injection by gavage, at a dose of <NUM> of composition B per kilogram of the animal, i.e. a dose of <NUM> of xaliproden hydrochloride per kilogram of the animal. The concentration of xaliproden in rats plasma and in rats inner ear fluid (IEF) was measured at <NUM> timepoints, <NUM> rats being used at each timepoint for the concentrations measurements (in the plasma and optionally in the IEF). The timepoints are T0+1hour, T0+2hours, T0+4hours, T0+6hours, T0+8hours and T0+24hours for the concentration measurement in the rats plasma. The timepoints are T0+2hours, T0+4hours and T0+24hours for the concentration measurement in the rats inner ear fluid, as part of a terminal procedure including cochlea sampling and inner ear fluids collection from both ears of the rats. Bioanalytical methods were validated in both matrices (lithium heparin plasma and inner ear fluid) with a range of <NUM> to <NUM> ng/mL in plasma and <NUM> to <NUM> ng/mL in inner ear fluids.

The results are presented in <FIG> and in the following tables <NUM> and <NUM>:.

As shown in tables <NUM> and <NUM> and in <FIG>, paliroden and xaliproden salts, when administered by oral route, are able to cross the blood-labyrinth barrier and reach the inner ear. They are present in the IEF at concentrations ranging from about <NUM> ng/mL to about <NUM> ng/mL of IEF (approximately <NUM> to <NUM>).

Eight compositions compatible with trans-tympanic injections were prepared: four thermoreversible gel compositions and four lipid-based mucoadhesive solutions. These eight compositions were prepared both with paliroden fumarate as active agent, and with xaliproden hydrochloride as active agent.

The four thermoreversible gel compositions comprising paliroden are as follows:.

The four thermoreversible gel compositions comprising xaliproden are as follows:.

The four lipid-based mucoadhesive solutions comprising paliroden are as follows:.

The four lipid-based mucoadhesive solutions comprising xaliproden are as follows:.

The solubility of respectively paliroden and xaliproden in the compositions was measured. The results are presented in the following table:.

Therefore, the formulated thermoreversible gel compositions and lipid-based mucoadhesive solutions contained a significant portion of paliroden or xaliproden in solution, compared with a solubility of less than <NUM>/mL in water for both molecules. This makes it possible to expect that paliroden or xaliproden will be able to cross the round window membrane and enter the inner ear when administered in compositions 2P to 8P or 2X to 8X respectively.

Among the thermoreversible gel compositions, the highest solubilities of paliroden and xaliproden were obtained respectively in compositions 4P and 4X. These compositions 4P and 4X were shown to gel in less than <NUM> minutes at <NUM> and are usable below <NUM> for injection through a <NUM> needle for trans-tympanic injection.

Among the lipid-based mucoadhesive solutions, the highest solubilities of paliroden and xaliproden were obtained respectively in compositions 7P, 8P and 7X, 8X. Compositions 7P and 7X had viscosity values between <NUM> and <NUM> mPa. Compositions 8P and 8X had viscosity values up to <NUM> mPa. Compositions 7P, 8P, 7X and 8X were shown to be able to pass through a <NUM> needle for transtympanic injection.

Composition 7P and composition 7X as described in example <NUM> were administered to male Wistar rats (<NUM> animals per active agent and timepoint), as described below.

At time T0, <NUM>µL of composition 7P were administered to <NUM> rats, in a single ear via trans-tympanic injection. The dose of paliroden fumarate that has been administered is thus of <NUM>µg in one ear of each rat.

At time T0, <NUM>µL of composition 7X were administered to <NUM> other rats, in a single ear via trans-tympanic injection. The dose of xaliproden hydrochloride that has been administered is thus of <NUM>µg in one ear of each rat.

For the <NUM> rats that have received composition 7P and for the <NUM> rats that have received composition 7X, plasmatic and inner ear expositions were determined via blood and cochlea terminal sampling in order to achieve lithium-heparin plasma and inner ear fluid preparation, at T+<NUM> hour, T+<NUM> hours and T+<NUM> hours. Bioanalytical methods were validated in both matrices (lithium heparin plasma and inner ear fluid) with a range of <NUM> to <NUM> ng/mL for paliroden (fumarate salt) and <NUM> to <NUM> ng/mL for xaliproden (hydrochloride salt).

As shown in tables <NUM> and <NUM> and in <FIG>, paliroden and xaliproden, when administered in a lipid-based mucoadhesive solution via a trans-tympanic injection, are able to cross the round window membrane and rapidly reach high concentrations in the inner ear fluid of approximately <NUM> ng/mL and <NUM> ng/mL respectively (approximately <NUM> and <NUM> in the IEF).

Composition 4P and composition 4X as described in example <NUM> were administered to male Wistar rats (<NUM> animals per active agent and timepoint), as described below.

At time T0, <NUM>µL of composition 4P were administered to <NUM> rats, in a single ear via trans-tympanic injection. The dose of paliroden fumarate that has been administered is thus of <NUM>µg in one ear of each rat.

At time T0, <NUM>µL of composition 4X were administered to <NUM> other rats, in a single ear via trans-tympanic injection. The dose of xaliproden hydrochloride that has been administered is thus of <NUM>µg in one ear of each rat.

For the <NUM> rats that have received composition 4P and for the <NUM> rats that have received composition 4X, plasmatic and inner ear expositions were determined via blood and cochlea terminal sampling in order to achieve lithium-heparin plasma and inner ear fluid preparation, at T+<NUM> hour, T+<NUM> hours and T+<NUM> hours. Bioanalytical methods were validated in both matrices (lithium heparin plasma and inner ear fluid) with a range of <NUM> to <NUM> ng/mL for paliroden (fumarate salt) and <NUM> to <NUM> ng/mL for xaliproden (hydrochloride salt).

As shown in tables <NUM> and <NUM> and in <FIG>, paliroden and xaliproden, when administered as suspensions in a thermoreversible hydrogel composition via a trans-tympanic injection, are able to cross the round window membrane and rapidly reach high concentrations in the inner ear fluid of approximately <NUM> ng/mL (approximately <NUM> in the IEF) and are sustainably released over <NUM> consecutive days with concentrations in the inner ear fluid at 7days post injection of approximately 600ng/ml (approximately <NUM>) and 100ng/ml (approximately <NUM>) for paliroden and xaliproden respectively.

Fourty-three male Wistar rats were selected and distributed to treatment and control groups, each group comprising between <NUM> to <NUM> rats at the start of the study. Randomization was performed using the ABR threshold in the left ear at <NUM> as a criterium. The "sham" group comprises <NUM> rats, which received neither noise exposure nor trans-tympanic injection. The "untraumatized vehicle" group comprises <NUM> rats, which did not receive noise exposure but received a trans-tympanic injection of placebo (a composition comprising only Cremophor EL®). The "traumatized" group comprises <NUM> rats, which received noise exposure only and no treatment. The "traumatized vehicle" group comprises <NUM> rats, which received noise exposure and a trans-tympanic injection of placebo (a composition comprising only Cremophor EL®). The "traumatized paliroden" group comprises <NUM> rats, which received noise exposure and a trans-tympanic injection of a composition comprising paliroden (fumarate salt), corresponding to composition 7P described in Example <NUM>. The "traumatized xaliproden" group comprises <NUM> rats, which received noise exposure and a trans-tympanic injection of a composition comprising xaliproden (hydrochloride salt), corresponding to composition 7X described in Example <NUM>.

All animals (except sham group) received a bilateral noise exposure at a noise band of <NUM>-<NUM> at <NUM> dB SPL RMS during <NUM> hours (from time T0 to time T0+<NUM> hours).

<NUM>µL of compositions comprising either paliroden or xaliproden as active agent were administered once in both ears of each rat of the treatment groups (<NUM>µL per ear) via trans-tympanic administration by injection between the eardrum and the round window by means of a needle which crosses the eardrum, <NUM> hours after the start of the noise exposure (i.e. at T0+<NUM> hours, thus <NUM> hours after the end of the noise exposure), under isoflurane anesthesia. The compositions correspond respectively to compositions 7P and 7X described in Example <NUM>, i.e. they comprise only Cremophor EL® as excipient and either paliroden (fumarate salt) or xaliproden (hydrochloride salt) as active agent. The dose of paliroden (fumarate salt) that is administered is <NUM>µg per ear of the rats belonging to the "traumatized paliroden" group (<NUM>µg in the <NUM>µL that are injected via trans-tympanic route by injection between the eardrum and the round window by means of a needle which crosses the eardrum). The dose of xaliproden (hydrochloride salt) that is administered is <NUM>µg per ear of the rats belonging to the "traumatized xaliproden" group (<NUM>µg in the <NUM>µL that are injected via trans-tympanic route by injection between the eardrum and the round window by means of a needle which crosses the eardrum).

To summarize, the chronology of the protocol was as follows:.

The results are presented in <FIG> and <FIG>.

The protocol used in this study (<NUM>-<NUM> sound at <NUM> dB SPL RMS, <NUM> hours, sound emitted in open field) induced hearing loss in Wistar rats after noise exposure as demonstrated in all traumatized groups by a significant increase of ABR thresholds at T0 + <NUM> day (see <FIG>). The hearing impairments were still observed at T0 + <NUM> days for the traumatized animals, with threshold shifts superior to <NUM> dB from <NUM> to <NUM> (see <FIG>).

The trans-tympanic administration of the vehicle, alone without combination to noise-trauma, induced an increase of ABR thresholds in comparison to control animals (see <FIG>). Therefore, the groups treated with paliroden (fumarate salt) or xaliproden (hydrochloride salt) were compared to the traumatized vehicle group (and not traumatized untreated group, data not shown), in order to take into consideration the effect of the trans-tympanic injection of vehicle on the ABR thresholds.

Hearing improvement was observed in both paliroden and xaliproden treated groups, as shown in <FIG> and <FIG>.

Paliroden at <NUM>µg/ear and xaliproden at <NUM>µg/ear exhibit a beneficial effect on hearing function in rats, already at one day following noise exposure. with ABR Threshold shifts reduction of approximately 10dB from <NUM> to <NUM> in comparison to the traumatized vehicle group (<FIG>).

This beneficial effect on the hearing function in rats was maintained and extended at <NUM> days post-noise. Paliroden at <NUM>µg/ear and xaliproden at <NUM>µg/ear achieve ABR Threshold shifts reduction of approximately <NUM> dB from <NUM> to <NUM> for xaliproden and approximately <NUM>-<NUM> dB from <NUM> to <NUM> paliroden treatments in comparison to the traumatized vehicle group (<FIG>).

Overall, in addition to the hearing improvement observed at at T0 + <NUM> day, Paliroden at <NUM>µg/ear and xaliproden at <NUM>µg/ear allow an additional hearing recovery of approximately <NUM> to <NUM> dB from <NUM> to <NUM> for xaliproden and from <NUM> to 20dB from <NUM> to <NUM> for paliroden treatments in comparison to the traumatized vehicle group between T0 + <NUM> days and T0 + <NUM> day (<FIG>).

Fifty male Wistar rats were selected and distributed to treatment ("traumatized paliroden" group and "traumatized xaliproden" group) and control groups ("sham" group, "traumatized" group and "traumatized vehicle" group), each group comprising at least <NUM> rats at the end of the study. Randomization was performed using the ABR threshold in the left ear at <NUM> as a criterium. The "sham" group consists in rats (n=<NUM>) that received neither noise exposure nor trans-tympanic injection. The "traumatized" group consists of rats (n=<NUM>) that received noise exposure only and no treatment. The "traumatized vehicle" group consists in rats (n=<NUM>) that received noise exposure and trans-tympanic injection in both ears of <NUM>µL of placebo (a composition comprising Poloxamer <NUM> (<NUM>,<NUM>%w/w), Poloxamer <NUM> (<NUM>%w/w) and Cremophor EL® (<NUM>%w/w) in phosphate buffer pH=<NUM>, the percentages being expressed relative to the total weight of the composition) between the eardrum and the round window by means of a needle which crosses the eardrum, <NUM> hours after the start of the noise exposure (i.e. injection of placebo at T0+<NUM> hours, thus <NUM> hours after the end of the noise exposure) and <NUM> days post-noise exposure, under isoflurane anesthesia. The "traumatized paliroden" group consists in rats (n=<NUM>) that received noise exposure and trans-tympanic injections of a composition comprising paliroden (fumarate salt), corresponding to composition 4P described in Example <NUM>. The "traumatized xaliproden" group consists in rats (n=<NUM>) that received noise exposure and trans-tympanic injections of a composition comprising xaliproden (hydrochloride salt), corresponding to composition 4X described in Example <NUM>.

<NUM>µL of compositions comprising either paliroden or xaliproden as active agent were administered once in both ears of each rat of the treatment groups (<NUM>µL per ear) via trans-tympanic administration by injection between the eardrum and the round window by means of a needle which crosses the eardrum, <NUM> hours after the start of the noise exposure (i.e. at T0+<NUM> hours, thus <NUM> hours after the end of the noise exposure) and <NUM> days post-noise exposure, under isoflurane anesthesia. The compositions correspond respectively to compositions 4P and 4X described in Example <NUM>, i.e. they comprise a mixture of poloxamer <NUM>, poloxamer <NUM> and Cremophor EL® (<NUM>%w/w; <NUM>%w/w and <NUM>%w/w respectively, the percentages being expressed relative to the total weight of the composition) and either paliroden (fumarate salt) or xaliproden (hydrochloride salt) as active agent. The dose of paliroden (fumarate salt) that is administered is <NUM>µg per ear of the rats belonging to the "traumatized paliroden" group (<NUM>µg in the <NUM>µL that are injected via trans-tympanic route by injection between the eardrum and the round window by means of a needle which crosses the eardrum). The dose of xaliproden (hydrochloride salt) that is administered is <NUM>µg per ear of the rats belonging to the "traumatized xaliproden" group (<NUM>µg in the <NUM>µL that are injected via trans-tympanic route by injection between the eardrum and the round window by means of a needle which crosses the eardrum).

At T+28DAYS, after DPOAE/ABR measures, <NUM> cochleae (all eight (<NUM>) left cochleae and two (<NUM>) right cochleae taken randomly) per group were rapidly sampled and immediately fixed by PFA perfusion (through the round and oval windows with PFA <NUM>% after creating a small hole at the apex) in order to performed ribbon synapse immunostaining and analysis. Cochleae were fixed for <NUM> hour in a <NUM>% PFA solution and decalcified in undiluted RDO (<NUM>/cochlea for a minimum of <NUM> hours). The membranous and sensory spiral containing the organ of Corti are dissected out as a flat surface preparation under a dissecting microscope and immunolabelled with appropriate antibodies:.

Images were acquired on a confocal microscope and the slides were analyzed to i) evaluate by visual observation the presence of OHC (outer hair cells) and IHC (inner hair cells) (based on nuclei staining with CtBP2 and HC cell body staining with phalloidin) and ii) count the number of synaptic ribbons in selected inner hair cells in cochlea regions coding sound of selected frequency (<NUM>, <NUM> and <NUM>).

The number of pre- (CtBP2) and post-synaptic (Homer) labeled spots was counted using Imaris software in <NUM> dimensions for each image. Co-localization of pre- and post-synaptic elements was defined as a distance of maximum <NUM> between CtBP2- and Homer-labeled spots, using an in-house Matlab program to calculate the distances between CtBP2 and Homer labels from the x, y, and z coordinates.

The protocol used in this study (<NUM>-<NUM> sound at <NUM> dB SPL RMS, <NUM> hours, sound emitted in open field) induced permanent hearing loss in Wistar rats after noise exposure, materialized by residual ABR thresholds shifts and DPOAE amplitude reduction from baseline of approximately 20dB at T0 + <NUM> days in all traumatized animals (data not shown).

Xaliproden, Paliroden and vehicle treatment did not show effect on ABR thresholds, DPOAE amplitudes nor ABR Wave I amplitudes at T0 + <NUM> days in comparison to the traumatized animals either untreated or treated with the vehicle.

ABR wave I amplitudes measured at T0 + <NUM> days, mainly reflect the permanent hearing loss and cannot be used to evaluate the treatment of synaptopathy, defined as reduced of ABR wave I amplitudes in animals with normal hearing thresholds comparable to sham group, after noise exposure causing temporary ABR thresholds increase.

Therefore, synaptopathy was investigated by immunohistochemistry on noise-exposed cochlea versus sham cochlea, comparing the number of intact synapses (colocalizing pre- and post-synaptic elements) in traumatized animals with untraumatized control animals and focusing on basal cochlear regions coding higher frequencies (<NUM>, <NUM> and <NUM>) which are mostly affected by the acoustic trauma noise band (see <FIG>).

Paliroden at <NUM>µg/ear and xaliproden at <NUM>µg/ear administered <NUM> hours and <NUM> days post-noise lead to an increase in the number of colocalized ribbons per IHC at <NUM> in comparison to the traumatized vehicle group (<FIG>). Paliroden at <NUM>µg/ear was also found to exhibit similar effect at <NUM>.

Additionally, Paliroden at <NUM>µg/ear and xaliproden at <NUM>µg/ear administered <NUM> hours and <NUM> days post-noise lead to an increase in the number of pre-synaptic elements CtBP2 per IHC at <NUM> and <NUM> in comparison to the traumatized vehicle group (<FIG>).

Overall, Paliroden at <NUM>µg/ear and xaliproden at <NUM>µg/ear administered <NUM> hours and <NUM> days post-noise tend to repair synapse loss in the inner hair cells of rats exposed to noise causing permanent hearing loss, in regions coding high frequency sounds. In human translation, this is expected to enhance the sound coding capabilities of patients and address their intelligibility deficit in noisy environments (hidden hearing loss).

Forty male Wistar rats were selected and evenly distributed to treatment and control groups, each group comprising <NUM> rats at the end of the study. Randomization was performed using the ABR threshold in the left ear at <NUM> as a criterium. The "sham" group consists in rats (n=<NUM>) that received neither noise exposure nor trans-tympanic injection. The "traumatized NaCl" group consists of rats (n=<NUM>) that received noise exposure only and trans-tympanic injections of a saline solution. The "traumatized vehicle" group consists in rats (n=<NUM>) that received noise exposure and trans-tympanic injections of placebo (a composition comprising Poloxamer <NUM> (<NUM>,<NUM>%w/w), Poloxamer <NUM> (<NUM>%w/w) and Cremophor EL® (<NUM>%w/w) in phosphate buffer pH=<NUM>, the percentages being expressed relative to the total weight of the composition). The "traumatized paliroden" group consists in rats (n=<NUM>) that received noise exposure and trans-tympanic injections of a composition comprising paliroden (fumarate salt), corresponding to composition 4P described in Example <NUM>. The "traumatized xaliproden" group consists in rats (n=<NUM>) that received noise exposure and a trans-tympanic injection of a composition comprising xaliproden (hydrochloride salt), corresponding to composition 4X described in Example <NUM>.

<NUM>µL of a saline solution (<NUM>%w/w of NaCl in water) were administered once in both ears of each rat of the "traumatized NaCl" group (<NUM>µL per ear) via trans-tympanic administration by injection between the eardrum and the round window by means of a needle which crosses the eardrum, <NUM> days and <NUM> days post noise exposure, under isoflurane anesthesia.

<NUM>µL of the placebo (a composition comprising Poloxamer <NUM> (<NUM>,<NUM>%w/w), Poloxamer <NUM> (<NUM>%w/w) and Cremophor EL® (<NUM>%w/w) in phosphate buffer pH=<NUM>, the percentages being expressed relative to the total weight of the composition) were administered once in both ears of each rat of the "traumatized vehicle" group (<NUM>µL per ear) via trans-tympanic administration by injection between the eardrum and the round window by means of a needle which crosses the eardrum, <NUM> days and <NUM> days post noise exposure, under isoflurane anesthesia.

<NUM>µL of compositions comprising either paliroden or xaliproden as active agent were administered once in both ears of each rat of the treatment groups (<NUM>µL per ear) via trans-tympanic administration by injection between the eardrum and the round window by means of a needle which crosses the eardrum, <NUM> days and <NUM> days post noise exposure, under isoflurane anesthesia. The compositions correspond respectively to compositions 4P and 4X described in Example <NUM>, i.e. they comprise a mixture of poloxamer <NUM>, poloxamer <NUM> and Cremophor EL® (<NUM>%w/w; <NUM>%w/w and <NUM>%w/w respectively, the percentages being expressed relative to the total weight of the composition) and either paliroden (fumarate salt) or xaliproden (hydrochloride salt) as active agent. The dose of paliroden (fumarate salt) that is administered is <NUM>µg per ear of the rats belonging to the "traumatized paliroden" group (<NUM>µg in the <NUM>µL that are injected via trans-tympanic route by injection between the eardrum and the round window by means of a needle which crosses the eardrum). The dose of xaliproden (hydrochloride salt) that is administered is <NUM>µg per ear of the rats belonging to the "traumatized xaliproden" group (<NUM>µg in the <NUM>µL that are injected via trans-tympanic route by injection between the eardrum and the round window by means of a needle which crosses the eardrum).

At T+<NUM> days, after DPOAE/ABR measures, <NUM> cochlea (all eight (<NUM>) left cochleae and two (<NUM>) right cochleae taken randomly) per group were rapidly sampled and immediately fixed by PFA perfusion (through the round and oval windows with PFA <NUM>% after creating a small hole at the apex) in order to performed ribbon synapse immunostaining and analysis. Cochleae were fixed for <NUM> hour in a <NUM>% PFA solution and decalcified in undiluted RDO (<NUM>/cochlea for a minimum of <NUM> hours). The membranous and sensory spiral containing the organ of Corti are dissected out as a flat surface preparation under a dissecting microscope and immunolabelled with appropriate antibodies:.

Images were acquired on a confocal microscope and the slides were analyzed to i) evaluate by visual observation the presence of OHC and IHC (based on nuclei staining with CtBP2 and HC cell body staining with phalloidin) and ii) count the number of synaptic ribbons in selected inner hair cells in cochlea regions coding sound of selected frequency (<NUM>, <NUM> and <NUM>).

The protocol used in this study (<NUM> to <NUM> sound at <NUM> dB SPL RMS, <NUM> hours, sound emitted in open field) induced permanent hearing loss in Wistar rats after noise exposure, materialized by residual ABR thresholds shifts and DPOAE amplitude reduction from baseline of approximately <NUM> dB at T0 + <NUM> days in all traumatized animals (data not shown).

ABR wave I amplitudes measured at T0 + <NUM> days, mainly reflect the permanent hearing loss and cannot be used to evaluate the treatment of synaptopathy, defined as reduced of ABR wave I amplitudes in animals with normal hearing thresholds comparable to sham group, after noise exposure causing temporary ABR thresholds increase. Indeed, the decrease in wave I amplitude is attributable to synaptopathy only in the context of a trauma with transient deafness. In the case of permanent deafness, even moderate permanent deafness, the wave I amplitude decrease also reflects this permanent deafness and not only the loss of synapses.

Paliroden at <NUM>µg/ear and xaliproden at <NUM>µg/ear, administered <NUM> days and <NUM> days post-noise, lead to an increase in the number of colocalized ribbons per IHC at <NUM> in comparison to the traumatized vehicle and traumatized NaCl groups (<FIG>), which was found statistically significant for Paliroden at this frequency. Paliroden at <NUM>µg/ear was also found to exhibit similar effect at <NUM>.

Additionally, Paliroden at <NUM>µg/ear and xaliproden at <NUM>µg/ear administered <NUM> days and <NUM> days post-noise lead to an increase in the number of pre-synaptic and post-synaptic elements (CtBP2 and Homer respectively) per IHC at <NUM> in comparison to the traumatized vehicle and traumatized NaCl groups (<FIG>).

As shown in <FIG>, Paliroden at <NUM>µg/ear and xaliproden at <NUM>µg/ear administered <NUM> hours and <NUM> days post-noise significantly repair synapse loss in the inner hair cells of rats exposed to noise causing permanent hearing loss, in regions coding high frequency sounds. Significantly more orphan pre and post-synaptic elements (green dots and red dots respectively) are found in traumatized animals treated with NaCl or vehicle than animals treated with Paliroden. Significantly more co-localized synaptic elements, leading to intact and functional synapses, are therefore observed upon Paliroden and Xaliproden treatments. In human translation, this is expected to enhance the sound coding capabilities of patients and address their intelligibility deficit in noisy environments (hidden hearing loss).

Twelve male CBA/CaJ mice were selected and evenly distributed to treatment and control groups, each group comprising <NUM> mice at the end of the study. Randomization was performed using the ABR threshold in the left ear at <NUM> as a criterium. The "sham" group consists in mice (n=<NUM>) that received neither noise exposure nor trans-tympanic injection. The "Traumatized" group consists in mice (n=<NUM>) that received noise exposure only. The "traumatized paliroden" group consists in mice (n=<NUM>) that received noise exposure and trans-tympanic injections of a composition comprising paliroden (fumarate salt), corresponding to composition 4P described in Example <NUM>.

All animals (except sham group) received a bilateral noise exposure at a noise band of <NUM>-<NUM> at <NUM> dB SPL RMS during <NUM> hours (from time T0 to time T0+<NUM> hours) in awake conditions.

Five microliters of a composition comprising paliroden as active agent were administered once in both ears of each mice of the treatment groups (<NUM>µL per ear) via trans-tympanic administration by injection between the eardrum and the round window by means of a needle which crosses the eardrum, <NUM> hours post noise exposure, under isoflurane anesthesia. The composition corresponds to composition 4P described in Example <NUM>, i.e. it comprises a mixture of poloxamer <NUM>, poloxamer <NUM> and Cremophor EL® (<NUM>%w/w; <NUM>%w/w and <NUM>%w/w respectively, the percentages being expressed relative to the total weight of the composition) with paliroden (fumarate salt). The dose of paliroden (fumarate salt) that is administered is <NUM>µg per ear of the mice belonging to the "traumatized paliroden" group (<NUM>µg in the <NUM>µL that are injected via trans-tympanic route by injection between the eardrum and the round window by means of a needle which crosses the eardrum).

At T+<NUM> days, after DPOAE/ABR measures, all cochlea (four (<NUM>) left cochleae and four (<NUM>) right cochleae) per group were rapidly sampled and immediately fixed by PFA perfusion (through the round and oval windows with PFA <NUM>% after creating a small hole at the apex) in order to performed ribbon synapse immunostaining and analysis. Cochleae were fixed for <NUM> hour in a <NUM>% PFA solution and decalcified in undiluted RDO (<NUM>/cochlea for a minimum of <NUM> hours). The membranous and sensory spiral containing the organ of Corti are dissected out as a flat surface preparation under a dissecting microscope and immunolabelled with appropriate antibodies:.

The results are presented in <FIG>, <FIG>, <FIG>, <FIG> and <FIG>.

The protocol used in this study (awake noise trauma at <NUM>-<NUM>, <NUM> dB SPL RMS, <NUM> hours, sound emitted in open field) induced temporary hearing loss in CBA/CaJ mice after noise exposure, materialized by temporary ABR thresholds increase and DPOAE amplitude reduction of at least 20dB from baseline at T0 + <NUM> day (<FIG> and <FIG>), with complete recovery observed at T0 + <NUM> days and ABR thresholds as well as DPOAE amplitude returning to normal values identical to those observed in the sham group (less than 10dB difference) (<FIG> and <FIG>).

In such model of temporary hearing loss, synaptopathy is characterized by a persistent significant decrease of ABR waves I at T0+<NUM> days observed in the traumatized groups (Group <NUM>) in comparison to the sham group (Group <NUM>), as shown in <FIG>. At <NUM>, <NUM>, <NUM> and <NUM>, traumatized untreated mice exhibit an immediate ABR wave I amplitude reduction <NUM> day post-noise exposure, ranging from <NUM> to <NUM>% reduction in comparison to untraumatized control mice (sham group). At T0+<NUM> days, these ABR Wave I amplitude decrease were found persistent, in the range of <NUM>% to <NUM>% showing very limited spontaneous recovery.

Paliroden treatment, occurring immediately after auditory evaluation one day post-noise exposure, led to complete recovery of the ABR Wave I amplitudes <NUM> weeks post-noise at all evaluated frequencies (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>). Indeed, ABR Wave I amplitudes in traumatized mice treated with paliroden were found comparable to untraumatized control mice (sham group), at all frequencies.

In a subset analysis (displayed in <FIG> and <FIG>), corresponding to only animals complying with acceptance criteria for noise exposure (i.e. at least <NUM> dB increase in ABR thresholds one day post-noise) and control normal conditions (sham should not exhibit ABR thresholds increase higher than 20dB in comparison to baseline level), the ABR Wave I amplitude recovery achieved by Paliroden treatment was found statistically significant at frequencies of <NUM> (<FIG>), <NUM> (<FIG>), <NUM> (<FIG>) and <NUM> (<FIG>), in comparison to traumatized untreated mice (p values < <NUM>).

Additionally, in this identical subset analysis group, this finding was correlated with a significant decrease in the number of pre-synaptic and post-synaptic elements (CtBP2 and Homer respectively) per IHC at <NUM> in traumatized mice compared to control mice (Sham) (p value < <NUM>; <FIG>). Paliroden at <NUM>µg/ear administered one day post-noise tended to increase the number of pre-synaptic and post-synaptic elements (CtBP2 and Homer respectively) per IHC at <NUM> in comparison to the traumatized untreated groups (<FIG>), resulting in an increase as well as of colocalized ribbons per IHC representing functional synapses at <NUM> (<FIG>). At frequencies ranging from <NUM> to <NUM>, the number of colocalized ribbons per IHC obtained in Paliroden treated mice were found intermediate between traumatized and control mice, and not statistically different to values obtained for control mice (sham).

In another on-going experiment to complete the above described example <NUM>, seventeen additional male CBA/CaJ mice are evenly distributed to treatment and control groups. Randomization is performed using the ABR threshold in the left ear at <NUM> as a criterium. The "sham" group consists in mice (n=<NUM>) that received neither noise exposure nor trans-tympanic injection. The "Traumatized" group consists in mice (n=<NUM>) that receive noise exposure only. The "traumatized paliroden" group consists in mice (n=<NUM>) that receive noise exposure and trans-tympanic injections of a composition comprising paliroden (fumarate salt), corresponding to composition 4P described in Example <NUM>. The "traumatized xaliproden" group consists in mice (n=<NUM>) that receive noise exposure and trans-tympanic injections of a composition comprising xaliproden (hydrochloride salt), corresponding to composition 4X described in Example <NUM>.

Identical procedure to those of Example <NUM> are scheduled on these animals in order to demonstrate similar findings achieved by Xaliproden treatment. The expected results are that both Paliroden and Xaliproden treatment are able to restore ABR wave I amplitudes to normal levels (untraumatized animals), <NUM> weeks post-noise exposure causing temporary hearing loss with persistent sound coding deficiencies due to loss of afferent ribbon synapses at inner hair cell level. As shown for Paliroden, it is expected that Xaliproden repairs ribbon synapses of IHC in cochlea regions coding high frequencies (> <NUM>).

Claim 1:
A compound of formula (I) or a pharmaceutically acceptable salt and/or solvate thereof, for use in the treatment of a hearing disease in a subject, wherein formula (I) is:
<CHM>
wherein
R<NUM> is a halogen atom, a CF<NUM> group, a (C<NUM>-C<NUM>)alkyl group or a (C<NUM>-C<NUM>)alkoxy group;
R<NUM> and R<NUM> are independently a hydrogen atom or a (C<NUM>-C<NUM>)alkyl group; and
A is:
- a phenyl radical substituted by a substituent X, wherein X is:
(a) a group selected from (C<NUM>-C<NUM>)cycloalkyl, (C<NUM>-C<NUM>)cycloalkylmethyl, (C<NUM>-C<NUM>)cycloalkoxy, (C<NUM>-C<NUM>)cycloalkylamino and cyclohexenyl; or
(b) a group selected from phenyl, phenylmethyl, phenylcarbonyl, phenoxy, phenylamino, N-(C<NUM>-C<NUM>)alkyl-phenylamino, phenylthio, phenylsulfinyl and phenylsulfonyl; or
- a <NUM>-naphthyl or <NUM>-naphthyl radical, either non-substituted or substituted in the <NUM>-, <NUM>-, <NUM>- and/or <NUM>-positions by one or two hydroxyl groups, one or two (C<NUM>-C<NUM>)alkoxy groups or a <NUM>,<NUM>-methylenedioxy group.