JP5520361B2 - Delivery of modulators of glutamate-mediated neurotransmission to the inner ear - Google Patents

Description

  The present invention relates to devices and methods for delivering drugs to the inner ear to treat inner ear disorders such as tinnitus. In particular, the present invention relates to the use of modulators of L-glutamate mediated neurotransmission (MGMN). Specifically, the present invention relates to excess NMDA receptor mediated without causing hearing loss associated with suppression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor mediated signals. It relates to delivering an N-methyl-D-aspartate (NMDA) receptor antagonist to the round window niche of the inner ear so as to suppress the signal. In particular, the present invention relates to D-2-amino-5-phosphonopentanoate (D-AP5), dizocilpine (MK 801), 7-chloroquinurenate (D-AP5), a round window niche of the inner ear to treat tinnitus. 7-CK), and delivery of NMDA receptor antagonists such as, but not limited to, gacyclidine (GK-11).

  Some injuries, such as infections, vascular disorders, or sound of sufficient intensity and duration, will damage the ear and cause temporary or permanent hearing loss. Hearing loss can range from mild to severe. It may also be related to symptoms such as tinnitus in which reverberant sounds, stuttering, voiced frictional sounds, or tapping sounds that occur in the head when no external sound is present. Repeated sound overstimulation or other injuries can accumulate throughout life and cause permanent damage that cannot be treated at this time. Hearing impairments have a major impact on an individual's ability to communicate, and even minor impairments can adversely affect the quality of life of the general public. Unfortunately, even though such hearing loss is preventable, our environment is becoming noisy and more and more people are at risk.

  L-glutamate (glutamate) is the most important afferent neurotransmitter in the auditory system, and it converts the mechanical displacement of the basement membrane into the activity of primary auditory afferent nerve fibers (cochlear sensory hair cells ( (See, for example, Puel (1995) Neurobiol 47: 449-476 for a review). The ionotropic receptors with which glutamate interacts during rapid excitatory synaptic transmission include agonists, namely N-methyl-D-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazole Included are three types of receptors named for their sensitivity to propionate (AMPA) and kainate (kainic acid). Glutamate can also act through metabotropic receptors (ie, receptors that undergo activation linked to an intracellular biochemical cascade). Analysis of glutamate receptors by gene expression, immunocytochemistry, and in situ hybridization reveals that primary auditory neurons are NMDA (NR1 and NR2A-D), AMPA (GluR2-4), and kainate (GluR5-7) receptor subunits And was shown to express high affinity kainate binding proteins (KA1 and KA2) (Puel (1995) supra). This suggests that all these receptors coexist on primary auditory neurons.

  In addition to rapid excitability, glutamate is also involved in excitotoxicity, a form of neuronal degeneration in the cochlea. This excitotoxicity can occur, for example, when large amounts of glutamate are released in the cochlea or when recycling is incomplete. Cochlear excitotoxicity is involved in sudden hearing loss and tinnitus induced by ischemia or noise (Pujol et al. (1999) Ann NY Acad Sci. 884: 249-54; Pujol et al. (1992) NeuroReport 3 : 299-302; Puel et al. (1994) J. Comp. Neurol. 341: 241-256; Puel (1995), supra).

  Excitotoxicity can generally be characterized by a two-step mechanism. In the first stage, glutamate causes overactivation of the ionic glutamate receptor, which is cation permeable. This causes excessive ion permeation, osmotic swelling, free radical generation, and neuronal death. The second stage of glutamate excitotoxicity (which may occur after strong and / or repetitive injury) consists of a cascade of metabolic events triggered by Ca2 + entry. This causes neuronal death in the spiral ganglion. Neosynapse formation and functional recovery are accompanied by upregulation of NMDA and metabotropic glutamate receptors.

  The prevention of excitotoxicity has been studied using various antagonists of the counterionic glutamate receptor. Perfusion of the glutamate antagonist quinurenate in the cochlea prevents sound-induced synaptic damage in guinea pigs (Puel et al. (1998) NeuroReport 9: 2109-2114). The AMPA receptor antagonism can block the excitotoxic effect of glutamate (glutamic acid) in the cochlea, for example, by intracochlear injection of a selective AMPA receptor antagonist. Intracochlear perfusion of 6,7-dinitroquinoxaline-2,3-dione (DNQX) for 10 minutes before or simultaneously with AMPA perfusion prevented most of the occurrence of radial dendritic swelling (Puel et al. al., (1991), supra). When both DNQX and D-AP5 (NMDA receptor antagonist D-2-amino-5-phosphonopentanoate) are perfused in the cochlea, all radial dendrites are almost completely protected from AMPA perfusion (Puel et al. (1994) J. Comp Neurol 341: 241-256). However, the use of cochlear perfusion in the clinic is impractical and may be unacceptable for humans when considered comprehensively, as it may cause permanent damage to the cochlea. Systemic delivery of a compound that modulates glutamate activity results in severe side effects such as memory loss and stupor, especially when delivered systemically at a dosage sufficient to treat the inner ear.

Puel (1995) Neurobiol 47: 449-476 Pujol et al. (1999) Ann N Y Acad Sci. 884: 249-54 Pujol et al. (1992) NeuroReport 3: 299-302 Puel et al. (1994) J. Comp. Neurol. 341: 241-256 Puel et al. (1998) NeuroReport 9: 2109-2114.

  As is apparent from the foregoing, there is a great need for devices and methods for effective and practical clinical treatment of inner ear disorders such as hearing loss and related symptoms (eg tinnitus). The present invention addresses this problem.

  The invention features methods and devices for delivering locally to and through the middle ear agents that modify glutamate-mediated neurotransmission to treat inner ear disorders such as tinnitus. .

  In one embodiment, the present invention is directed to directly interacting an agent with sensory hair cells to reduce glutamate release or interacting with neurons to reduce synaptic transmission or indirectly. Delivering an agent that modulates synaptic transmission to the inner ear by modulating endogenous factors that result in reduced synaptic transmission (eg, by administering a dopamine agonist).

  In other related embodiments, the present invention directly interacts with a glutamate receptor to reduce glutamate binding (e.g., reduce glutamate binding to one or more counterionic receptors or NMDA). By acting as an antagonist to a glutamate receptor, such as a receptor), or indirectly by modulating endogenous factors that result in reduced glutamate binding to the glutamate receptor (e.g., modulating the glycine site of the PCP site). Delivery) of agents that alter post-synaptic glutamate-mediated neurotransmission.

  An animal model that causes tinnitus by administration of salicylate was prepared. In this model, excessive signaling is mediated by NMDA receptors rather than AMPA receptors. In the present invention, tinnitus is treated by blocking excess signal with specific NMDA receptor antagonists.

  In particular, the present invention relates to D-AP5 (a specific NMDA antagonist, D-2-amino-5-phosphonopentanoate) (Clin Med J) at or near the round window niche of the inner ear to treat tinnitus. (Engl) 2002 Jan; 115 (1): 89-93), dizocilpine (MK 801) (J Neurotrauma 2000 Nov; 17 (11): 1079-93), 7-chloroquinurenate or gacyclidine (GK-11) Delivery of NMDA receptor antagonists such as, but not limited to, (Curr Opin Investig Drugs 2001 Jun, 2 (6): 814-9). According to this method, excess NMDA receptor-mediated signals that cause tinnitus are suppressed without causing undesired hearing loss associated with suppression of AMPA receptor-mediated signals.

  One advantage of the present invention is that the delivery of the drug directly to the inner ear avoids the possibility of toxicity and side effects (e.g. memory loss or stupor) that can be associated with systemic delivery of glutamate-mediated neurotransmitter modulators. Is Rukoto.

  In one aspect, the invention features treating an inner ear disorder by perfusing the agent across the round window membrane to deliver an agent that modulates glutamate-mediated neurotransmission in the inner ear.

  Another advantage of the present invention is that when the modulator of glutamate-mediated neurotransmission is an NMDA-specific receptor, these agents are less toxic in a form of hearing loss than other non-NMDA-specific receptor modulators of glutamate activity. It is.

  Another advantage is that by using the present invention, modulators of glutamate-mediated neurotransmission can be delivered accurately and precisely over a given period of time in relatively small amounts. Long-term drug delivery devices eliminate the need for regular dosing by the patient, improving patient compliance with the specified therapeutic regimen, especially with the specified prophylactic regime before the onset of symptoms To do. This is particularly useful in populations that are more difficult to comply with such medications, such as infants and the elderly.

  Another advantage of the present invention is that modulators of glutamate-mediated neurotransmission can be delivered to the inner ear in a small amount with accuracy and precision that allows long-term use of such compounds for the treatment of inner ear disorders.

  A further advantage is that a therapeutically effective dose of a modulator of glutamate-mediated neurotransmission can be achieved at a relatively low volumetric rate such that damage or injury to the easily damaged structures of the middle ear and / or inner ear is minimized, e.g. It can be delivered at about 0.01 μl / day to 2 ml / day.

  These and other objects, advantages, and features of the present invention will be apparent to those of ordinary skill in the art upon reading the details of the procedures and compositions described more fully below.

FIG. 1 is a schematic diagram of the ear showing the outer ear, the middle ear, and the inner ear and clearly showing the round window. FIG. 2 shows two graphs comparing the effects of short time cochlear perfusion and long time round window perfusion. These graphs represent the average amplitude of the CAP as a function of the intensity of the 8 kHz tone burst stimulus. The mean threshold was calculated from 5 separate animals. Note that both short-term intracochlear and long-round round window applications of riluzole reduce CAP amplitude in a dose-dependent manner. However, when the drug was applied to the round window, the effect was 1/10 the potency. FIG. 3 shows the protective effect of riluzole on acoustic injury induced by loud noise. Two days after 30 minutes exposure to continuous sound, CAP audiograms (threshold fluctuations as a function of sound frequency) were measured. The threshold variation was calculated as the difference between the recorded values before and after 2 days of exposure to a 6 kHz continuous tone. Shown is the threshold variation recorded after 30 minutes exposure to 120 dB SPL in the presence of artificial perilymph (red curve, control). Note that 100 μM riluzole shows a clear protective effect either when applied directly in the cochlea (blue curve, intra) or when applied to the round window (green curve, RW). “N” is the number of test animals. FIG. 4A shows the results of an experiment that determines the ability of perfused glutamate antagonists to suppress salicylate-induced excitement. This is the result of an initial recording with an auditory nerve fiber coding with a spontaneous rate of 8 spikes / second at 8 kHz. Intracochlear perfusion of control artificial perilymph (AP) containing 100 μM indomethacin (open bars) did not alter the spontaneous activity of auditory nerve fibers. In contrast, application of 5 mM sodium salicylate (NaSal; black bar) reversibly increased spontaneous firing of auditory nerve fibers. FIG. 4B shows the results obtained with neural fiber coding with a spontaneous rate activity of 7 spikes / second at 9 kHz. Blocking AMPA receptors (open bars) with 50 μM AMPA agonist GYKI 53784 (Neuropharm. 30 1959-1973, 2000) blocked both spontaneous activity and activity induced by 5 mM NaSal (black bars). . FIG. 4C shows the results obtained with nerve fiber coding with a spontaneous rate of 5 spikes / second at 7,5 kHz. Sodium salicylate was applied continuously. Repeated application of NMDA antagonist 7 CK (50 μM, n = 5) (open bar) suppressed auditory nerve excitation induced by Na salicylate, but not spontaneous fiber activity. FIG. 4D shows that repeated application of the NMDA antagonist gacyclidine (50 μM, n = 5) suppressed auditory nerve excitation induced by Na salicylate but not fiber spontaneous activity. ing. Figure 5A shows the number of positive responses to sound when delivering salicylate from day 2 to day 5 as a percentage (score%) vs. period in days relative to the total exposure to the sound. Show. FIG. 5B shows the results representing the number of responses (false positives) without sound when delivering salicylate on days 2-5. Using this behavioral paradigm, treatment with saline solution (daily intraperitoneal injection for 4 days) did not change either the score or the number of false positives. In contrast, sodium salicylate treatment (daily ip injection for 4 days at 300 mg / kg / day) resulted in a reversible decrease in score and a dramatic increase in the number of false positives. FIG.5C shows composite action potential (CAP) audiograms in behavior-trained animals recorded before (day 0), during (days 3 and 4), and after treatment (day 6). Results are shown. CAP thresholds were measured for tone bursts with a rise / fall time of 1 ms and a duration of 9 ms presented at a rate of 10 times per second using electrodes implanted in the round window for a long time. Salicylate treatment (daily intraperitoneal injection for 4 days at 300 mg / kg / day) resulted in 30 dB hearing loss over the frequency range of 2 to 26 kHz. FIG. 5D shows the CAP threshold variation at 10 kHz before, during and after salicylate processing. The CAP threshold variation was calculated as the dB difference between the day 0 hearing threshold and the day hearing threshold. In order to avoid changes due to hearing loss, the intensity of sounds that cause behavioral responses was adjusted as a function of CAP threshold variation. FIG. 5E shows that no significant decrease in score was observed when salicylate was delivered on days 2-5. FIG. 5F shows that a false positive response still remained after salicylate treatment. This indicates that the increase in the number of false positive responses during sodium salicylate treatment was not due to hearing loss but to the occurrence of tinnitus. The drug was applied into the cochlea fluid using gel foam placed in a round window. (G) Note that the score did not change. In contrast, application of 50 μM 7-CK round window prevented the generation of false positive responses. These findings suggest that cochlear NMDA receptor activation is required to induce tinnitus with sodium salicylate. From this experiment it can be concluded that round window perfusion of NMDA antagonists suppresses tinnitus induced by salicylate. FIG. 6 shows a comparison of the effects of NMDA antagonists on tinnitus induced by salicylate. Artificial perilymph (AP, n = 10) only, or MK 801 (10 μM, n = 10), 7-chloroquinurenate (7-CK, 50 μM, n = 10), or gacyclidine (50 μM, n = 10) The number of false positive responses measured at the last salicylate treatment (day 4) in animals with gel foam soaked in) is shown. Compared to AP alone, the topical application of MK 801, 7-CK, or gacyclidine significantly reduced the occurrence of false positive responses.

  Before describing the devices and methods of the present invention for treating inner ear disorders, it is understood that the present invention is not limited to the specific procedures, devices, therapeutic formulations, and syndromes described. There must be. Of course, they can take many forms. Also, the terminology used herein is for the purpose of describing particular embodiments only and is intended to limit the scope of the invention which is limited only by the appended claims. It must be understood that it is not a thing.

  It should be noted that as used in this specification and the appended claims, the singular includes the plural referent unless the context clearly differs. Thus, for example, reference to “a drug delivery device” includes a plurality of such devices, and reference to “a delivery method” includes references to equivalent steps and methods known to those skilled in the art. The same applies to other cases.

  Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods, devices and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods, devices and materials are now described.

  All publications mentioned in this specification are herein incorporated by reference for the purpose of illustrating and disclosing the compositions and procedures described in the publications that may be used in connection with the invention described herein. Shall be incorporated. The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. It should not be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention.

Definitions As used herein, the term “inner ear disorder caused by abnormal glutamate-mediated neurotransmission” refers to symptoms caused by overstimulation or understimulation of glutamate receptors, eg, tinnitus, sudden onset of ischemia This is associated with sexual deafness, sudden deafness caused by noise, and the like.

  The term “subject” means any subject, generally a mammal (eg, human, dog, cat, horse, cow, ungulate, pig, etc.) for which treatment of an inner ear disorder is desired.

  The acronym CAP means the combined action potential in microvolts.

  The term “implantation site” is used to relate to a body site of a subject into which a drug delivery device is introduced.

  The terms `` agents that modulate glutamate-mediated neurotransmission '', `` modulators of glutamate-mediated neurotransmission '', `` glutamate neuromodulators '' refer to glutamate release (presynaptic modulators of glutamate-mediated neurotransmission) or glutamate receptors Agents that act either directly or indirectly to increase or decrease glutamate binding activity (a postsynaptic modulator of glutamate-mediated neurotransmission) are intended to be included.

  Reference to one compound as a “derivative” of another compound means that the derivative has been or may have been prepared from the underlying compound and shares the core structural components.

  An “analog” is a compound that is structurally and functionally related to another compound; compounds and analogs share high structural similarity and have similar biological functions, and isomers Is included.

  A “pharmaceutical composition” is a mixture containing a drug (defined below).

  The term “formulation” (or “pharmaceutical formulation”) refers to a pharmaceutically acceptable excipient or carrier (eg, a solvent, specifically water, phosphate buffered saline, or other acceptable substance). Means any drug used in combination. The formulation is directed to one or more agents (drugs) that modulate glutamate-mediated neurotransmission, such as NMDA receptor antagonists, AMPA receptor antagonists, and kainate (kainic acid) receptor antagonists, or more than one receptor of that type. It can contain active ingredients.

  The term “therapeutically effective amount” means the amount of therapeutic agent or the rate of delivery of the therapeutic agent that is effective to promote the desired therapeutic effect. In general, the present invention relates to subjects suffering from or at risk for a health condition associated with abnormal glutamate-mediated neurotransmission in the inner ear (e.g., unacceptably high glutamate-mediated Alleviation of such symptoms in subjects who are exposed to noisy traumatic injuries that are believed to be at a level sufficient to induce temporary or permanent hearing loss in the subject through neurotransmission activity.

  The term “sustained release” means a prolonged (drug) release as opposed to a “bolus” release. Sustained release can be, for example, over a period of at least 12 hours, at least 24 hours, at least 2 weeks, at least 1 month, at least 3 months, or longer.

  The term “drug delivery device” is associated with any means for containing and releasing a drug. Here, the drug is released to the subject. The drug delivery device can include a catheter. In this case, the drug is delivered through the catheter. The containment means is not limited to containment in a walled container, including non-injection devices (such as pumps) and injection devices such as gels, viscous or semi-solid materials, or even liquids. It can be any type of containment device. Drug delivery devices are divided into five main groups: inhalation devices, oral devices, transdermal devices, parenteral devices, and suppository devices. Inhalation devices include gasified, misted, emulsified, and microsprayed bronchial inhalers (including nasal inhalers); oral devices most often include pills; In most cases, the skin device includes a patch. Parenteral devices include two subgroups: injection devices and non-injection devices. Non-injectable devices are commonly referred to as “implants” or “non-injectable implants” and include, for example, solid biodegradable polymers and pumps (eg, osmotic pumps, biodegradable implants, electrical diffusion systems, Electroosmotic pressure system, vapor pressure pump, electrolytic pump, bubble pump, piezoelectric pump). Injectable devices are divided into bolus injections that are injected to dissipate and release the drug all at once and depots that remain separately at the injection site and release the drug over time. Depot agents include, for example, oil agents, gel agents, liquid polymer agents and non-polymer agents, and microsphere agents. The drug delivery device of the present invention can be attached to a catheter for delivering drug from the device to a target site. It is also possible to utilize a catheter as a drug delivery device. That is, the drug is placed in a sealed catheter that is essentially a tube having an opening at at least one of the drug delivery ends (although in most cases there is also an opening at the other end to balance the pressure when the drug is delivered). It can be inserted and inserted into the ear, for example through the tympanic membrane, with the drug delivery end seated in the round window niche so that the drug flows from the catheter into the round window niche. This flow can be achieved by capillary action as the drug is absorbed through the round window and more drug is withdrawn from the catheter body through the drug delivery end. A number of drug delivery devices are described in Encyclopedia of Controlled Drug Delivery (1999), Edith Mathiowitz (Ed.), John Wiley & Sons, Inc.

  As used herein, the term “agent” relates to any substance that is intended to alter the physiology of an animal.

  The term “dosage form” is associated with a drug plus drug delivery device.

  “Patterned” or “temporary” delivery of a drug is, for example, an increasing, decreasing, substantially constant or pulsing rate or rate range (eg, the amount of drug per unit time or unit time). Means to deliver the drug so that it changes as expected.

  The expression “substantially continuous” generally means uninterrupted over a preselected drug delivery time (eg, as compared to the time associated with a bolus injection).

  As used herein, the terms “treat”, “treatment” and the like are associated with obtaining a desired pharmacological and / or physiological effect. The effect may be prophylactic in the sense of completely or partially preventing the health condition or its symptoms and / or partially or completely cure the disease and / or adverse effects that can be attributed to the disease. Or it may be therapeutic in the sense of suppression. “Treatment” as used herein includes all treatments of inner ear disorders (eg, including but not limited to hearing loss, tinnitus, etc.) in animals, particularly humans, such as (A) preventing the occurrence of inner ear disorders in subjects who may be affected but not symptomatic at that time; (b) inhibiting inner ear disorders such as hearing loss or tinnitus or other such Stopping the progression of such diseases or disorders; or (c) alleviating the disease, i.e. causing regression and / or amelioration of the disease.

Overview The present invention is capable of delivering a modulator of glutamate-mediated neurotransmission to the inner ear by diffusion through the middle-inner ear membrane (e.g., round window membrane or radial ligament at the base of the radius), and such delivery Is found to be effective in attenuating glutamate-mediated neurotransmission. In particular, we have suppressed excessive NMDA receptor-mediated signals (causing tinnitus in certain cases) without causing undesired hearing loss associated with suppression of AMPA receptor-mediated signals. We found that NMDA receptor antagonists (e.g., but not limited to D-AP5, MK801, 7-chloroquinurenate, or gacyclidine) can be delivered to the round window niche of the inner ear. It was.

  Without being bound by theory, delivering a modulator of glutamate-mediated neurotransmission across the round window membrane is effective in attenuating the action potential and calcium influx associated with glutamate-mediated neurotransmission. As a result of weakening glutamate-mediated neurotransmission, overstimulation of glutamate receptors is avoided or reduced and symptoms usually associated with increased glutamate activity are reduced (e.g., hearing retention or tinnitus symptoms are reduced). Etc.) If the agent used to attenuate neurotransmission is an agent that specifically inhibits NMDA receptor-mediated signals, undesirable effects associated with inhibition of AMPA receptor-mediated signals or signals mediated by other receptors, such as Hearing loss can be avoided.

  Thus, in view of the above, modulation of glutamate-mediated neurotransmission according to the present invention can be achieved in various ways. For example, glutamate receptor stimulation can be reduced by modulating glutamate-mediated neurotransmission at the presynaptic to reduce glutamate release. By administering an agent that acts to reduce glutamate release, presynaptic glutamate neuromodulation can be achieved directly. Agents that interact with one or more glutamate receptors (e.g., compete with glutamate for binding to the receptor, bind to the receptor to affect the affinity or avidity of the receptor for glutamate, or glutamate binding and By administering agents that otherwise reduce the glutamate receptors available for stimulation, post-synaptic glutamate neuromodulation can be achieved directly. As a result, by administering an agent that increases the level of endogenous factors that affect the binding of glutamate to the glutamate receptor (e.g., by administering a dopamine agonist), the post-synaptic glutamate neuromodulation is indirectly Can be achieved.

  Other options include increasing glutamate receptor stimulation, e.g., directly or indirectly causing increased glutamate release (modulation of presynaptic) or directly or indirectly increasing glutamate receptor stimulation. Can cause glutamate-mediated neurotransmission to be modulated.

  Note that the effectiveness of the desired effect of the modulator of glutamate-mediated neurotransmission may not be complete. For example, if a decrease in glutamate receptor stimulation is desired, the modulator of glutamate-mediated neurotransmission may not completely block glutamate activity, and may decrease glutamate neurotransmission stimulation activity overall. Also good. Completely blocking glutamate-mediated neurotransmission can result in at least temporary hearing loss (ie, if there is no glutamate-mediated neurotransmission, auditory nerves are not stimulated and auditory feeling is lost). Fully block glutamate-mediated neurotransmission unless temporary hearing loss as a result of blocking glutamate-mediated neurotransmission may provide protection against exposure to stimuli that may cause permanent hearing loss That is generally undesirable.

Glutamate Neuromodulators and Formulations The formulations of the present invention will include an agent that acts as a direct or indirect modulator of glutamate-mediated neurotransmission by activity before or after glutamate release. Such agents include glutamate binding to a counterionic glutamate receptor (eg, NMDA receptor, AMPA receptor, or kainate receptor) or a metabotropic receptor (eg, mGluR1, 3-5, 7, 8). However, the present invention is not limited to these agents. Additional agents include agents that directly or indirectly reduce glutamate release into the presynaptic region. For a review of suitable glutamate antagonists, steroids, and antioxidants for use in the present invention in the treatment of the inner ear, see Simpson and Davies, (Trends Pharmacol Sci 20, 12 (1999).

  Representative agents include NMDA specific glutamate antagonists such as D-2-amino-5-phosphonopentanoate (D-AP5), dizocilpine (MK 801), 7-chloroquinurenate (7- CK) and gacyclidine (GK-11), but are not necessarily limited thereto. Of the NMDA antagonists, gacyclidine is considered to be one of the preferred compounds. Agents that can be used in the present invention include agents that affect neurotransmitters or neuromodulators such as acetylcholine, GABA, dopamine, enkephalin, dynorphin, and calcitonin gene-related peptides, including those of outer efferent nerves. Mention may also be made of drugs that simulate or block the action. In addition, any drug that acts on sodium channel activity, such as riluzole and dextromethorphan, can be used to treat inner ear disorders such as tinnitus according to the present invention.

  Representative structures and derivatives or analogs of compounds that can be used in the present invention are described below. Derivatives or analogs useful in the present invention may contain additional or alternative substituents (—R) at various positions. In this case, such substituents can be selected from any suitable group. One skilled in the art can select substituents taking into account the charge and size and position of the substituents to minimize steric hindrance effects and retain functionality. For example, the substituents can be individually selected from the group consisting of hydrogen or halogen and unsubstituted or substituted alkyl, alkenyl, and alkynyl of up to 6 carbon atoms.

D-2-amino-5-phosphonopentanoate (D-AP5) has the following chemical structure.

Derivatives or analogs of D-AP5 useful in the present invention may contain additional or alternative substituents (—R) at various positions as shown below.

7-chloroquinurenate (7-CK) has the following chemical structure:

The 7-CK derivatives or analogs useful in the present invention may contain additional or alternative substituent (—R) groups at various positions as shown below.

Dizocilpine (MK 801) has the following chemical structure.

Derivatives or analogs of MK 801 useful in the present invention may contain additional or alternative substituent (—R) groups at various positions as shown below.

Gacyclidine (GK-11) has the following chemical structure (two racemic structures are shown):

Derivatives or analogs of gacyclidine useful in the present invention may contain additional or alternative substituent (—R) groups at various positions as shown below.

  While the agents described above can be used for delivery according to the present invention, modifications within the scope of the present invention will be apparent to those of skill in the art upon reading the disclosure provided herein.

  Modulators of glutamate-mediated neurotransmission delivered include (but are not limited to) combination therapy (e.g. drug interaction potential), subject age, severity of disorder, recurrence of subject symptoms, etc. May vary depending on various factors, including

  The agent that modulates glutamate-mediated neurotransmission can be provided as any of a variety of formulations adapted for delivery across the middle-inner ear membrane, provided that such The formulation must be stable (ie it must not degrade to an unacceptable amount at body temperature). The concentration of the agent in the formulation can vary from about 0.1% to about 50 or 75% by weight. The agent can be in any form suitable for delivering and diffusing the agent across the middle-inner ear membrane structure, eg, solid, semi-solid, gel, liquid, suspension, emulsion , Osmotic dosage formulations, diffusion dosage formulations, erodible formulations and the like. In one embodiment, the formulation is suitable for delivery using an implantable pump, such as an osmotic pump, coupled to a catheter inserted in the vicinity of the round window niche of the inner ear.

  Pharmaceutical grade organic or inorganic carriers, excipients, and / or diluents can be incorporated into the formulation. To provide a suitable composition, the formulation optionally includes a buffer, e.g., sodium phosphate buffer at physiological pH values, saline, or both (i.e., phosphate buffered saline). sell. Suitable excipients include dextrose, glycerol, alcohols (e.g., ethanol) and the like, as well as one or more thereof, vegetable oil, propylene glycol, polyethylene glycol, benzyl alcohol, benzyl benzoate, dimethyl sulfoxide (DMSO), organics, and the like , May be included. In addition, if desired, the composition may comprise a hydrophobic or aqueous surfactant, dispersant, wetting or emulsifying agent, isotonic agent, pH buffering agent, solubility enhancer, stabilizing agent, preservative, and pharmaceutical preparation. Other typical auxiliary additives utilized in the formulation of can be included. Representative additional active ingredients that may be present in formulations useful in the present invention can include, but are not limited to, D-AP5, MK 801, 7-chloroquinurenate, or gacyclidine. Absent.

  The modulator of glutamate-mediated neurotransmission can be provided as a solution, suspension, and / or precipitate in the formulation.

Health conditions that are amenable to treatment according to the present invention Generally, administration of a formulation according to the present invention results in inner ear disorders caused by overstimulation of glutamate receptors, for example inner ear caused by abnormally increased release of glutamate Inner ear disorders resulting from disorders and / or defects in glutamate receptor signaling that induce abnormally increased glutamate receptor activity can be treated (eg, prophylactically or post-occurrence). Of particular interest are inner ear disorders that may require long-term therapy, for example, therapy from several days (e.g., about 3-10 days) to several weeks (e.g., about 2 weeks or 4 weeks-6). Management of chronic and / or persistent inner ear disorders (eg tinnitus) that require treatment for up to a week), months or years, up to a period that includes the remaining life of the subject. Subjects who are not currently suffering from a disease or condition but are susceptible to such a disease or condition may particularly benefit from prophylactic management using the devices and methods of the present invention. Inner ear disorders that are amenable to therapy according to the present invention may include long-term episodes with alternating periods of relatively no symptoms or virtually constant symptoms of varying severity.

  Specific examples of symptoms, diseases, disorders, and physiological responses that are amenable to management according to the present invention include tinnitus, cochlear ischemia, noise exposure, hearing loss due to presbycusis, but are not necessarily limited to these is not.

Delivery of glutamate neuromodulators according to the present invention Generally, glutamate-mediated neurotransmission modulator formulations have a volumetric rate that is compatible with delivery to the inner ear via the middle ear and abnormal glutamate-mediated neurotransmission (e.g., glutamate Delivered in a therapeutically effective dose for the management of disorders caused by receptor overstimulation.

  In general, administration of a modulator of glutamate-mediated neurotransmission according to the present invention may range from several hours (e.g., 2 hours, 12 hours, or 24 hours to 48 hours, or more) to several days (e.g., 2 to Up to 5 days or more), up to several months or years. Typically, delivery is from a period of several days (1, 2, 7, 14 days) to about 1 month to about 3 months or 6 months or 9 months or about 12 months or longer. Can continue. The modulator of glutamate-mediated neurotransmission can be, for example, about 2 hours to about 72 hours, about 4 hours to about 36 hours, about 12 hours to about 24 hours, about 2 days to about 30 days, about 5 days to about 20 days, About 7 days or more, about 10 days or more, about 100 days or more, about 1 week to about 4 weeks, about 1 month to about 24 months, about 2 months to about 12 months, about 3 months to about 9 Individuals may be administered for a period of months, about 1 month or more, about 2 months or more, or about 6 months or more; or other periods within these ranges, including increments as needed. In certain embodiments, the formulation is delivered to the subject over a preselected time without requiring re-access to the device and / or without requiring refilling of the device. In these embodiments, formulations with high concentrations of glutamate-mediated neurotransmission modulators are of particular interest.

  Preferably, delivery of the formulations of the present invention is performed in a patterned manner, in a substantially continuous manner, or in a substantially constant preselected rate or rate range (e.g., amount or unit of agent per unit time). The volume of the formulation over time). Preferably, the agent is about 0.01 μl / day to about 2 ml / day, preferably about 0.04 μl / day to about 1 ml / day, generally about 0.2 μl / day to about 0.5 ml / day, typically Is delivered at a low volumetric rate of about 2.0 μl / day to about 0.25 ml / day.

  Long-term dosing is convenient for the subject and can be administered to outpatients if the long-term dose is simple and the patient's health is acceptable (see below for how to achieve delivery). Details). Long-term delivery can also improve patient compliance and provide more accurate dosing (eg, when using a controlled release drug delivery device). Implanted drug delivery devices (e.g., osmotic pumps) in that they reduce the risk of infection associated with external pumps or other methods that require repeated skin destruction and / or maintenance of the dosing port. Have further advantages.

  In one embodiment, the drug delivery device delivers a substantially continuous agent at a preselected rate to the membrane of the middle ear to the inner ear (e.g., to the round window membrane or the annulus ligament at the base of the radius). I will provide a. In this embodiment, the agent is about 0.1 μg / hour to about 200 μg / hour, usually about 0.25 μg / hour or 3 μg / hour to about 85 μg / hour, typically about 5 μg / hour to about 100 μg / hour. Can be delivered at a rate of In certain exemplary embodiments, the modulator of glutamate-mediated neurotransmission is delivered at a rate of about 0.1 μg / hr, 0.25 μg / hr, 1 μg / hr, generally up to about 200 μg / hr.

  One skilled in the art can readily determine the appropriate amount of a particular modulator of glutamate-mediated neurotransmission based on, for example, the relative potency of these agents and their effectiveness in animal models. The actual dose of drug delivered will depend on various factors such as the potency and other properties of the drug used (eg, hydrophilicity, rate of diffusion across the round window membrane, etc.).

Delivery of glutamate neuromodulators to the inner ear according to the present invention can be accomplished in various ways. These include filling the middle ear with a solution or other carrier containing the agent. See, for example, Shea (1997) Otolaryngol Clin North Am. 30 (6): 1051-9. It is also possible to achieve delivery of the agent by inserting gelatin or Gelfoam ^™ containing the agent. For example, Silverstein (1984) Ann Otol Rhinol Laryngol Suppl. 112: 44 8; Lundman et al. (1992) Otolaryngol 112: 524; Nedzelski et al. (1993) Am. J. Otol. 14: 278-82; Silverstein et al. (1996) Ear Nose Throat J 75: 468-88; Ramsay et al. (1996) Otolaryngol. 116: 39; Ruan et al. (1997) Hear Res 114: 169; Wanamaker et al. (1998) Am. See J. Otology 19: 170; Arriaga et al. (1998) Laryngoscope 108: 1682-5; and Husmann et al. (1998) Hear Res 125: 109. It is also possible to achieve delivery of the agent by inserting hyaluronan or hyaluronic acid mixed with the agent. See, for example, WO 97/38698; Silverstein et al. (1998) Am J Otol. 19 (2): 196 201; for the use of fibrin glue or other fibrin-based media in the delivery of agents to the inner ear. See, for example, Balough et al. (1998) Otolaryngol. Head Neck Surg. 119: 427-31; Park et al. (1997) Laryngoscope 107: 1378-81.

Delivery of glutamate neuromodulators to the inner ear according to the present invention can be accomplished using IntraEAR® Round Window μ-Cath ^™ products and Round Window E-Cath ^™ products. Both of these products are licensed under FDA and European CE Mark approval. Round Window μ-Cath ^TM and Round Window E-Cath ^TM products are uniquely designed duals that enable controlled fluid delivery to the round window membrane of the middle ear that physicians have used to treat a variety of ear disorders And triple lumen microcatheter. These catheters feature a unique tip designed to allow the surgeon to secure the middle ear round window niche. These catheters can be left in place for weeks and can be coupled to a syringe or pump (eg, from Disetronic Medical Systems) for continuous delivery of treatment fluid to the inner ear. With the dual lumen design, the treating physician can add and remove fluids or flush the device without increasing air or fluid pressure. Additional electrodes are built into the E-Cath design so that the physician can record electrical signals related to ear activity. Such InnerEar catheters are described in US Pat. Nos. 6,045,528; 5,421,818; 5,476,446; and 5,474,529. All of which are hereby expressly incorporated by reference. Such a catheter can be used in conjunction with the drug delivery device described below.

Delivery of Drugs Using Controlled Release Devices In general, drug release methods or devices suitable for use in the present invention include drug reservoirs for holding drug formulations or any other group capable of holding drugs. Contains a material or matrix (eg, polymer, bonded solid, etc.) The drug release device is well known in the art and suitable for delivery of drugs to the round window to facilitate perfusion of the drug into the round window or other inner ear-inner ear across the inner ear membrane A variety of implantable drug delivery systems can be selected.

  In certain embodiments, the delivery device is a device adapted for delivery of the formulation over an extended period of time. Such a delivery device may be adapted for administration of the formulation over a period of hours to weeks or longer. Drug delivery provides treatment or prevention for hearing loss, tinnitus, or other inner ear disorders. In general, modulators of glutamate-mediated neurotransmission are administered to an individual for at least 1 week, or at least several weeks, 1 month, 2 months, 3 months, 6 months, 1 year, or longer .

  The drug delivery device of the present invention may rely on a diffusion system, a convection system, or an erosion system (eg, an erosion-based system). For example, the drug release device can be an osmotic pump, an electroosmotic pump, a vapor pressure pump, or an osmotic burst matrix. In this case, for example, the drug is incorporated into the polymer, which provides for the release of the drug formulation simultaneously with the degradation of the drug-impregnated polymeric material (eg, biodegradable drug-impregnated polymeric material). In other embodiments, the drug delivery device relies on an electrical diffusion system, electrolytic pump, bubble pump, piezoelectric pump, hydrolysis system, and the like.

  When a drug delivery catheter or other delivery device is used in conjunction with a controlled release device, as a result of capillary action, as a result of pressure generated from the drug release device, by diffusion, by electrical diffusion, or by device and / or Electroosmotic pressure through a catheter (eg, the IntraEAR® catheter described above) can deliver the drug through the drug delivery catheter from the reservoir of the controlled release device to the round window membrane.

  Drug delivery devices are generally capable of transporting drug formulations in amounts and concentrations as required therapeutically, and sufficiently remove the formulation from attack by biological processes over the duration of implantation and delivery. Must be protected. Thus, the outer surface is preferably made of a material that has the property of reducing the risk of leakage, cracking, breakage, or distortion so that its contents are not uncontrolledly discharged under stresses that may be experienced during use. . The drug reservoir must be biocompatible (eg, substantially non-responsive to the subject's body or body fluid).

  Suitable materials are well known in the art. For example, the reservoir material can comprise a non-reactive polymer or a biocompatible metal or alloy. Suitable polymers include acrylonitrile polymers such as acrylonitrile butadiene polymers; halogenated polymers such as polytetrafluoroethylene, polyurethane, polychlorotrifluoroethylene, copolymers of tetrafluoroethylene and hexafluoropropylene; polyethylene vinyl Acetate (EVA), polyimide; polysulfone; polycarbonate; polyethylene; polypropylene; polyvinyl chloride acrylic copolymer; polycarbonate-acrylonitrile-butadiene-styrene; polystyrene; cellulosic polymers; . Additional representative polymers are described in the Handbook of Common Polymers, Scott and Roff, CRC Press, Cleveland Rubber Co., Cleveland, Ohio.

  Suitable metal materials for use in drug release device reservoirs include stainless steel, titanium, platinum, tantalum, gold, and alloys thereof; gold-plated alloy iron; platinized titanium, stainless steel, tantalum, Gold, and their alloys and other alloy irons; cobalt chromium alloys; and titanium steel coated stainless steel, titanium, platinum, tantalum, gold, and alloys thereof.

Exemplary materials used for the polymeric matrix include, but are not necessarily limited to, biocompatible polymers, including biostable polymers and biodegradable polymers. Typical biostable polymers include silicone, polyurethane, polyether urethane, polyether urethane urea, polyamide, polyacetal, polyester, polyethylene-chlorotrifluoroethylene, polytetrafluoroethylene (PTFE or “Teflon ^™ ”), styrene These include but are not necessarily limited to butadiene rubber, polyethylene, polypropylene, polyphenylene oxide-polystyrene, poly-a-chloro-p-xylene, polymethylpentene, polysulfone and other related biostable polymers. . Representative biodegradable polymers include polyanhydrides, cyclodextrans, polylactic acid-glycolic acid, polyorthoesters, n-vinyl alcohol, polyethylene oxide / polyethylene terephthalate, polyglycolic acid, polylactic acid, and other Related bioabsorbable polymers include, but are not necessarily limited to these.

  Another well-known drug delivery device is the “depot” of an injectable biodegradable sustained release device. This is generally not containerized and can act as a reservoir for the drug, from which the drug is released. Depots include polymeric and non-polymeric materials and can take the form of solids, liquids, or semi-solids. For example, the depot used in the present invention is a high viscosity liquid, such as a non-polymer water-insoluble liquid carrier material, specifically sucrose acetate isobutyrate (SAIB) or US Pat. No. 5,747,058 and May be other compounds described in US Pat. No. 5,968,542, both of which are expressly incorporated herein by reference. For references, see generally “Encyclopedia of Controlled Drug Delivery” 1999, published by John Wiley & Sons Inc, edited by Edith Mathiowitz. SAIB is, for example, one or more solvents such as, but not limited to, benzyl benzoate, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), or mixtures thereof. Can be formulated with any non-hydroxyl solvent. In certain embodiments, it may be desirable to use a solvent such as ethanol, methanol, or glycerol. Propellants can be added when the formulation is administered as a spray. Solvents can be added to SAIB at a solvent ratio of about 5% to about 50%.

  An exemplary device for controlled delivery of drugs to the inner ear according to the present invention is described in PCT Publication WO 00/33775. The device generally comprises a drug delivery unit comprising a carrier medium material that includes one or more therapeutic agents. The carrier medium material is designed to release the agent over time in a controlled manner, and is shaped and sized to place at least a portion of the device in a round window niche.

Drug release devices based on mechanical or electromechanical infusion pumps are also typically used in conjunction with a catheter that is implanted and functionally connected to deliver the drug to the round window membrane, It may be suitable for use in the present invention. Examples of such devices include those described in US Pat. Nos. 4,692,147; 4,360,019; 4,487,603; 4,360,019; 4,725,852, and the like. In general, the drug delivery method of the present invention can be accomplished using any of a variety of refillable and non-replaceable pump systems. In general, pumps and other convection systems are preferred. This is because they generally provide a more consistent controlled release over time. Osmotic pumps are particularly preferred because they combine the advantages of more consistent controlled release and relatively small size. Of the osmotic pumps, the DUROS ^™ osmotic pump is particularly preferred (see, eg, WO 97/27840 and US Pat. Nos. 5,985,305 and 5,728,396).

In one embodiment, the drug release device is a continuous drug release device in the form of an osmotic drive device. Preferred osmotically driven drug release systems can provide drug release at a rate in the range of about 0.1 μg / hr to about 200 μg / hr and can be from about 0.25 μl / day to about 100 μl / day (ie, about 0.0004). μl / hr to about 4 μl / hr), preferably about 0.04 μl / day to about 10 μl / day, generally about 0.2 μl / day to about 5 μl / day, typically about 0.5 μl / day to about 1 μl A system that can be delivered at a volumetric rate per day. In one embodiment, the volume / hour delivery rate is substantially constant (e.g., delivery is generally at a rate of about ± 5% to 10% of the volume over the time period described above, e.g., about Done at a volumetric velocity of ~)
In general, drug delivery devices suitable for use in the present invention are low doses, such as from about 0.1 μg / hr to about 200 μg / hr, preferably as low as about nanoliter to microliter per day, for example. The drug can be delivered at a rate. In one embodiment, a volume rate of about 0.01 μl / day to about 2 ml / day is achieved by delivering about 80 μl / hour for 24 hours. The delivery rate over 24 hours varies by about ± 5% to 10% over that time. Representative osmotic drive devices suitable for use in the present invention include U.S. Pat.Nos. 3,760,984; 3,845,770; 3,916,899; 3,923,426; 3,987,790; 3,995,631; No. 3,916,899; No. 4,016,880; No. 4,036,228; No. 4,111,202; No. 4,111,203; No. 4,203,440; No. 4,203,442; No. 4,210,139; No. 4,327,725; No. 4,627,850; No. 4,865,845; No. 5,057,318; No. 5,059,423; No. 5,112,614; No. 5,137,727; No. 5,234,692; No. 5,234,693; No. 5,728,396; However, it is not necessarily limited to these.

Delivery using a drug delivery catheter In some embodiments, it may be desirable to provide a drug delivery catheter with a drug delivery device, for example, where the implant site and the desired delivery site are not identical. A drug delivery catheter generally has a first end (ie, a “proximal” end) associated with the drug release device of the drug delivery device and a second for delivering the drug-containing formulation to the desired delivery site. A substantially hollow elongate member having an end (or "distal" end). When using a drug delivery catheter, the formulation contained in the drug reservoir moves through the drug delivery catheter by communicating the lumen of the drug delivery catheter with the drug reservoir in the drug delivery device, thereby creating a round window. The first end of the drug delivery catheter can be operably coupled to a drug delivery device for delivery from a delivery outlet of a catheter positioned to deliver the agent to the membrane. In one embodiment, the catheter is positioned at least partially within the round window niche so that the agent is delivered to the round window membrane.

  The body of the catheter defines a lumen having a diameter adapted to provide a leak-free delivery of the drug formulation. When the drug delivery device delivers the drug by convection (eg, in the case of an osmotic drug delivery system), the size of the catheter lumen extending from the reservoir of the drug release system is determined by Theeuwes (1975) J. Pharm. Sci. 64: 1987- It can be designed as described in 91.

  The body of the catheter can take any shape (eg, curved, substantially straight, tapered, etc.). The distal end of the drug delivery catheter may have one or more openings.

  The drug delivery catheter can be made from any of a variety of suitable materials. Impermeable materials suitable for use in making a controlled drug release device as described above are generally suitable materials for use in making a drug delivery catheter. Typical materials include polymers; metals; glasses; polyolefins (high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), polypropylene (PP), etc.); nylon Polyethylene terephthalate; Silicones; Urethanes; Liquid crystal polymers; PEBAX®; HYTREL®; TEFLON®; Perfluoroethylene (PFE) Perfluoroalkoxy resins (PFA); Poly (methyl methacrylate) ) (PMMA); polymer, metal, and / or glass multilaminate; Nitinol;

  In order to facilitate placement of the drug delivery catheter and / or to impart other desirable properties to the catheter, the drug delivery catheter may include additional materials or agents (e.g., external or internal catheter body surface (s)). ) Overcoating). For example, infection at the site of implantation and drug delivery by applying a silver coating to the inner wall and / or outer wall of the drug delivery catheter, or by applying an antimicrobial agent treatment or treatment with an antimicrobial agent The risk of symptoms can be further reduced.

  In one embodiment, the drug delivery catheter is primed with a drug-containing formulation. For example, the drug is substantially pre-filled before implantation. Priming the drug delivery catheter reduces the delivery start-up time, ie the time associated with the movement of the drug from the drug delivery device to the distal end of the drug delivery catheter.

Delivery of glutamate neuromodulators to the device middle-inner ear membranes used in the present invention (e.g., round window membrane or round window niche for perfusion across the radial ligament of the rib base) This can be achieved using a delivery device as described in patent 5,421,818. This patent includes a reservoir for a therapeutic agent and, in various embodiments, fluid transfer means (eg, pores, semi-permeable membranes, etc.) that deliver fluid material to the round window membrane and then diffuse into the inner ear. And various treatment systems are described. In other embodiments, the device includes a plurality of reservoir portions and multiple stem portions designed to be implanted in endolymphatic sac and endolymphatic vessels using, for example, standard microsurgical techniques. In still other embodiments, the device includes a reservoir portion for holding a liquid pharmaceutical substance therein, and first and second stems. The second stem can be delivered to the inner ear from the reservoir portion so that the first stem is present, for example, in an opening formed in the base / annular ligament of the patient. Can be present in the outer ear canal of the outside.

  Other devices suitable for use with the present invention are described in US Pat. No. 6,045,528. The device described in this patent includes one or more fluid transfer tubes coupled to a cover member, which can be disposed on or at least partially within the round window niche. In some embodiments, a liquid-resistant fluid receiving zone is formed in the round window niche. The cover member may have a plate-like structure or may include a compressible material.

  PCT Publication WO 00/04854 describes other devices suitable for use in the present invention. The device includes a fluid transfer tube that includes one or more passages therethrough. An inflatable bladder is attached to the tube and sized to be inserted at least partially into the inner lumen of the ear (eg, round window niche). Upon inflation, the bladder engages the inner sidewall of the inner cavity and a portion of the bladder and tube is secured within the inner cavity, allowing fluid transfer to and from the inner cavity.

Implantation Site and Delivery Site In certain embodiments, the drug delivery device can be implanted at any suitable implantation site using methods and devices well known in the art. Implanted sites include subdermal, subcutaneous, intramuscular, or other suitable sites in the subject's body, such as subcutaneous sites near the ear (eg, behind the ear canal) It is not limited to. Subcutaneous implantation sites are preferred because they allow for convenient implantation and removal of the drug delivery device. Delivery of the drug from the drug delivery device at the implantation site remote from the delivery site can be accomplished by providing a drug delivery device with a catheter.

  The drug delivery device may be completely or at least partially within the inner lumen of the ear, but in a preferred embodiment is at least partially within the round window niche. For example, it is disposed away from the round window membrane, or is disposed in contact with and / or adjacent to the membrane.

  A variety of methods can be used to insert an agent or device containing an agent into the ear to deliver the agent to the middle-inner ear membrane. For example, an agent formulation can be injected into the middle ear via the tympanic membrane and to facilitate contact between the agent formulation and the middle-inner ear membrane, for example, specially in a round window niche It is possible to arrange. Alternatively, the drug delivery device can be inserted into the middle ear to deliver the agent to the middle ear, or more directly into the round window membrane structure. In other embodiments, the drug delivery device is placed external to the middle ear and the catheter or other drug delivery tube operably attached to the drug delivery device causes the device's reservoir to the middle ear, eg, positive The drug is delivered to the round window membrane.

  Insertion of the drug delivery device can be accomplished by passing the device or a portion of the device through the eardrum or under the eardrum (using a suitable microsurgical instrument of conventional design). The tympanic membrane preferably has an incision that can penetrate the drug delivery device or a portion thereof. Alternatively, the device or a portion thereof can be inserted into the middle ear under the ear canal tympanic valve. Proper orientation and / or insertion of the drug delivery device can be achieved using, for example, a conventional surgical microscope or otoscope device of the type disclosed in U.S. Pat.No. 5,419,312 to Arenberg et al. Can be achieved.

  The placement of the drug delivery device is such that the drug from the device contacts at least a portion of the middle-inner ear membrane. By utilizing in the ear a filling material of the type normally used for medical applications, the drug delivery device can be secured in its desired location within the inner lumen of the ear. When the agent reaches the round window membrane, it is released from the drug delivery device and travels through the membrane or other structure that provides the interface between the middle ear and the inner ear into the inner ear.

  In general, drug delivery systems and methods offer many advantages and capabilities: (1) The therapeutic agent is delivered repeatedly and continuously into the inner ear through the round window membrane; (2 A) a wide variety of therapeutic agents (e.g., pharmaceutical preparations) are delivered safely and directly to the inner ear; (3) effective drug delivery is achieved without the use of overly invasive surgical procedures; and (4) A simplified method is used to deliver the therapeutic agent into the patient's inner ear without using complex medical procedures, monitoring, and without patient discomfort.

Methods and materials
Experiments were performed using adult guinea pig animal models weighing approximately 250g~300g human inner ear. The animals were anesthetized with urethane (1.4 g / kg, ip) and ventilated. Additional doses of urethane (0.35 g / kg, ip) were administered every 2 hours or more frequently when the animals retracted their limbs in response to pressure applied to the limbs. The rectal temperature was maintained at about 38.5 ± 1 ° C., and the heart rate (normal range 260-330 times / min) was monitored using an EKG electrode. The ear canal was incised in the vicinity of the tympanic ring to expose the eardrum so that the sound reached the eardrum without any obstructions. At the end of the experiment, the animals were euthanized by intracardiac injection of an overdose of pentobarbitone sodium.

Cochlear perfusion
Intracochlear perfusion was generally performed as described in Puel 1995 Neurobiology 47: 449-476. Briefly, after exposing the cochlea to the lower surface and cutting the middle ear muscle, perfuse the selected drug for 10 minutes at a rate of 2.5 microliters / minute through the hole provided in the tympanic floor, The drug was drained from the cochlea through a hole in the vestibule floor. Measurements were taken before and after placebo perfusion and after perfusion of increasing concentrations of the agent. At the end of each experiment, the cannula was flushed with an artificial perilymph to assess the reversibility of the agent's action. The artificial perilymph solution had the following composition: 1.37 mM NaCl; 5 mM KCl; 2 mM CaCl ₂ ; 1 mM MgCl ₂ ; 1 mM NaHCO ₃ ; 11 mM glucose, pH 7.4, osmolarity ( 302 ± 4.2 mosmol / kg H ₂ O). Five to ten guinea pigs were used in each experimental group.

  Formulate D-AP5 and MK 801 by dissolving in water to a final concentration in the range of 1-1000 micromolar and 7-chloro in 100% DMSO to a final concentration of 1-100 micromolar. Chinolenate and gacyclidine were dissolved.

Perfusion across the round window membrane
A long-term delivery model to the inner ear was provided by delivering the drug to the round window membrane for up to 14 days at a drug solution rate of 1 μl / hr using an animal RWE-Cath ^™ attached to an Alzet ^™ Osmotic Pump. In a cochlear perfusion experiment, the Alzet ^™ Osmotic Pump was primed at the highest concentration that did not cause any change in CAP amplitude, increase in CAP latency, or decrease in CM amplitude.

  Experiments were conducted to determine the highest concentration of an agent that provided a meaningful beneficial effect but did not cause changes in CAP amplitude, CAP latency, and did not decrease CM amplitude. A lower concentration (not lower flow rate) was tested if the concentration of the drug caused a change in CAP amplitude, an increase in CAP latency, or a decrease in CM amplitude. Higher concentrations (not higher flow rates) were tested when the drug concentration did not cause any change in CAP amplitude, increased CAP latency, or decreased CM amplitude. Five guinea pigs were used in each experimental group.

Stimulus and recording method An arbitrary function generator (LeCroy Instrument type 9100R) generated tone bursts (1 millisecond rise / fall time, 9 millisecond duration) at a rate of 10 times per second. Amplification and delivery of auditory stimuli was performed in a closed system via a Bruel and Kjaer microphone (type 4134). By changing the tone burst intensity (0-100 dB SPL (sound pressure level) in 5 dB steps), the intensity amplitude function was obtained. From the silver electrode with the Teflon coating (excluding the tip) placed in the third hole in the vestibular floor of the cochlear basal rotation, the complex action potential of the auditory nerve (CAP : N ₁ -P ₁ ), N ₁ latency, cochlear microphone potential (CM), and weighted potential (SP) were recorded. The potential was amplified (Tektronic ™ 503, gain 1000), averaged (256 samples), and stored on a Pentium® PC computer. The sampling rate of the A / D converter was 50 kHz, the dynamic range was 12 bits, and the number of samples per record was 1024. The CAP threshold was defined as the dB SPL required to cause a measurable response (1 microVolt).

Statistical effects analysis of variance (ANOVA) and Newmann-Keuls multiple range test were used to determine the significance of the agent effect (p <0,05). Data are expressed as mean ± standard error.

Salicylate tinnitus model Salicylate (the active ingredient of aspirin) is of particular interest in auditory science because it induces tinnitus in humans. The efficacy of agents treating tinnitus was tested by measuring the firing rate of auditory nerve fibers in the presence of salicylate.

  Methods for recording single unit responses from the auditory nerve during direct application of drugs into the cochlea have already been reported elsewhere (J. Ruel, C. Chen, R. Pujol, RP Bobbin, JL Puel, J Physiol. 518, 667, 1999). Briefly, the test solution was applied in the cochlea using a multi-barrel perfusion pipette (ASI Instruments) placed in a hole provided in the basal rotational tympanic floor and a hole (0.2 mm in diameter) provided in the apex. Spilled from the cochlea. The cochlear nerve was exposed using the retroposterior approach. Extracellular action potentials were recorded from single auditory nerve fibers using glass microelectrodes. After separating single units, spontaneous activity was averaged over 10 seconds. The unit's tuning curve was then determined by a computer controlled threshold tracking program using a 200 millisecond tone burst presented at 3 times / second. The threshold criterion was a difference of 10 spikes / second, ie, a difference of 2 spikes between the tone (200 ms) count interval and the non-tone (200 ms) count interval. The characteristic frequency (CF) was determined by the program, and the frequency tuning of the fiber was determined by measuring Q10dB, defined as the value of CF divided by the bandwidth at 10dB above the CF threshold.

  An important step in the initiation of action potentials is the activation of the postsynaptic receptor by the endogenous neurotransmitter glutamate (Glu) released by sensory endothelium (see other literature (J. Ruel, C. Chen, R. Pujol, RP Bobbin, JL Puel, J Physiol. 518, 667, 1999)). The hypothesis that sodium salicylate modulates rapid cochlear synaptic neurotransmission by acting on the alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA) receptor was proposed. Spontaneous activity and induction induced by sodium salicylate or sound by blocking the AMPA receptor with 50 μM AMPA antagonist GYKI 53784 (Neuropharm. 30 1959-1973, 2000), as shown in FIG. Both activities were blocked. Another possibility was the effect of salicylate on the N-methyl-D-aspartate (NMDA) receptor. Intracochlear perfusion of 10 μM MK 801, 50 μM gacyclidine, 50 μM 7-chloroquinurenic acid (7-CK) did not affect the spontaneous activity of the auditory fiber, whereas NMDA antagonists were induced by sodium salicylate. Excitement was suppressed (Fig. 1c). Thus, the excitatory effect of sodium salicylate on auditory nerve activity requires the activation of cochlear NMDA.

Example 1: Comparison of the effects of short-term cochlear perfusion and long-term round window perfusion of riluzole Short- time cochlear perfusion (AICP) is not practical in humans, so we We investigated whether safe and therapeutic effects could be achieved via (RWCP).

  The effects of short-time cochlear perfusion and long-time round window perfusion were compared. The result is shown in figure 2. These graphs represent the average amplitude of the CAP as a function of the intensity of the 8 kHz tone burst stimulus. The mean threshold was calculated from 5 separate animals. Note that both short-term intracochlear and long-round round window applications of riluzole reduce CAP amplitude in a dose-dependent manner. However, when the drug was applied to the round window, the effect was 1/10 the potency. The goal of the study was to compare the effects of short time cochlear perfusion (AICP) and long time round window perfusion (CRWP) on the normal function of the cochlea. These graphs (FIG. 2) represent the average amplitude of CAP as a function of the intensity of the 8 kHz tone burst stimulus. The mean threshold was calculated from 5 separate animals. Graph A shows that application of riluzole for a short time in the cochlear window reduced the amplitude of CAP. Graph B shows that long-time round window application of riluzole also reduced the amplitude of CAP in a dose-dependent manner. Note that the concentration needs to be increased 10-fold to achieve the same effect on CAP. From this experiment it can be concluded that riluzole retains its activity in the inner ear after prolonged perfusion across the round window membrane.

Example 2: Protective effect of riluzole on hearing impairment induced by loud noise As previously shown, short-term cochlear perfusion of riluzole restores hearing after noise-induced hearing loss (Wang et al. al., Neuroscience 2002, 111,635-648). An experiment was conducted to investigate the protective effect of riluzole on hearing impairment induced by loud noise. The results are shown in Figure 3. This figure shows a CAP audiogram (threshold variation as a function of sound frequency) measured 2 days after 30 minutes exposure to continuous sound. The threshold variation was calculated as the difference between the recorded values before and after 2 days of exposure to a 6 kHz continuous tone. Shown is the threshold variation recorded after 30 minutes exposure to 120 dB SPL in the presence of artificial perilymph (red curve, control). Note that 100 μM riluzole shows a clear protective effect either when applied directly in the cochlea (blue curve, intra) or when applied to the round window (green curve, RW). The letter “n” represents the number of test animals.

  The goal of the experiment was to demonstrate that riluzole is effective in protecting the inner ear from noise injury when applied on a round window membrane. An osmotic minipump containing only artificial perilymph was implanted in control animals. Short-term (within 20 minutes) exposure to 120 dB SPL pure tone (6 kHz, 30 minutes) produced a permanent threshold variation of 50-60 dB after 2 days of sound exposure (see Wang et al., Neuroscience, in press) ). A clear recovery of the threshold was observed when 100 μM riluzole was applied in the cochlea. The same effect was obtained when riluzole was applied to a round window. From this experiment, it can be concluded that perfusion of riluzole into the round window membrane is effective in protecting the inner ear from noisy injury.

Example 3: Effect of perfusion of glutamate antagonist on excitability induced by salicylate An experiment was conducted to examine the ability of perfused glutamate antagonists to suppress excitability induced by salicylate. The results are shown in FIG.

  FIG. 4A shows the results obtained with the initial recording by auditory nerve fiber coding with a spontaneous rate of 8 spikes / second at 8 kHz. Intracochlear perfusion of control artificial perilymph (AP) containing 100 μM indomethacin (open bars) did not alter the spontaneous activity of auditory nerve fibers. In contrast, application of 5 mM sodium salicylate (NaSal; black bar) reversibly increased spontaneous firing of auditory nerve fibers.

  FIG. 4B shows the results obtained with neural fiber coding with a spontaneous rate activity of 7 spikes / second at 9 kHz. Blocking AMPA receptors (open bars) with 50 μM AMPA agonist GYKI 53784 (Neuropharm. 30 1959-1973, 2000) blocked both spontaneous activity and activity induced by 5 mM NaSal (black bars). .

  FIG. 4C shows the results obtained with nerve fiber coding with a spontaneous rate of 5 spikes / second at 7,5 kHz. Sodium salicylate was applied continuously. Repeated application of NMDA antagonist 7 CK (50 μM, n = 5) (open bars) suppressed auditory nerve excitation induced by NaSal, but not fiber spontaneous activity.

  Similar results were obtained with 10 μM MK 801 and GK-11. Thus, the excitatory effect of sodium salicylate on auditory nerve activity requires activation of cochlear NMDA but not AMPA receptors. From this experiment it can be concluded that perfusion of glutamate antagonists suppressed auditory nerve excitement induced by salicylate.

Example 4: Effect of NMDA antagonists on salicylate-induced tinnitus To confirm that the excitatory effect of sodium salicylate on auditory nerve fibers causes perception of tinnitus, based on active avoidance behavior, rats A behavioral model was designed. The animals were trained to respond to a conditioned stimulus consisting of a 10 kHz tone burst with a duration of 3 seconds. The results obtained from the experiment are shown in FIG.

  Figure 5A shows the number of positive responses to sound when delivering salicylate from day 2 to day 5 as a percentage (score%) vs. period in days relative to the total exposure to the sound. Show.

  FIG. 5B shows the results representing the number of responses (false positives) without sound when delivering salicylate on days 2-5. Using this behavioral paradigm, treatment with saline solution (daily intraperitoneal injection for 4 days) did not change either the score or the number of false positives. In contrast, sodium salicylate treatment (daily ip injection for 4 days at 300 mg / kg / day) resulted in a reversible decrease in score and a dramatic increase in the number of false positives.

  FIG.5C shows composite action potential (CAP) audiograms in behavior-trained animals recorded before (day 0), during (days 3 and 4), and after treatment (day 6). Results are shown. CAP thresholds were measured for tone bursts with a rise / fall time of 1 ms and a duration of 9 ms presented at a rate of 10 times per second using electrodes implanted in the round window for a long time. Salicylate treatment (daily intraperitoneal injection for 4 days at 300 mg / kg / day) resulted in 30 dB hearing loss over the frequency range of 2 to 26 kHz.

  FIG. 5D shows the CAP threshold variation at 10 kHz before, during and after salicylate processing. The CAP threshold variation was calculated as the dB difference between the day 0 hearing threshold and the day hearing threshold. In order to avoid changes due to hearing loss, the intensity of sounds that cause behavioral responses was adjusted as a function of CAP threshold variation.

  FIG. 5E shows that no significant decrease in score was observed when salicylate was delivered on days 2-5.

  FIG. 5F shows that a false positive response still remained after salicylate treatment. This indicates that the increase in the number of false positive responses during sodium salicylate treatment was not due to hearing loss but to the occurrence of tinnitus. The drug was applied into the cochlea fluid using gel foam placed in a round window. (G) Note that the score did not change. In contrast, application of 50 μM 7-CK round window prevented the generation of false positive responses. These findings suggest that cochlear NMDA receptor activation is required to induce tinnitus with sodium salicylate. From this experiment it can be concluded that round window perfusion of NMDA antagonists suppresses tinnitus induced by salicylate.

Example 4: Comparison of the effects of NMDA antagonists on tinnitus induced by salicylate To prove the hypothesis that salicylate induces false positives via the cochlear NMDA receptor, we placed in the round window of both ears Other NMDA antagonists were applied in the perilymph fluid using the gel foam. Topical application of control artificial perilymph had no effect on either decreasing scores (Figure 6) or increasing the number of false positive responses induced by salicylate (Figure 6). In contrast, topical application of 10 μM MK 801; 50 μM 7-CK or 50 μM gacyclidine significantly reduces the occurrence of salicylate-induced false positive responses, and the decrease in score is still unchanged. Remained (FIG. 6). When compared to control artificial perilymph animals on day 4 (number of false positives 6.2 ± 0.86), the number of false positive responses was 0.7 ± 0.21; 0.7 ± 0.2 for MK 801, 7-CK, and gacyclidine, respectively. It decreased to 0.26 and 1 ± 0.21 (FIG. 5C). Overall, these results provide evidence that salicylate acts on rapid synaptic transmission in the cochlea through activation of NMDA receptors, causing the occurrence of tinnitus.

CONCLUSION From the above experiments, it can be concluded that abnormal glutamate-mediated neurotransmission mediated by NMDA receptors produces human tinnitus and that NMDA receptor antagonists can be used to treat such tinnitus. The present disclosure suggests that specific NMDA receptor antagonists block salicylate-induced tinnitus without causing unwanted hearing loss associated with suppression of AMPA receptor-mediated signals. Such NMDA antagonists include (but are not limited to) D-AP5 (D-2-amino-5-phosphonopentanoate), dizocilpine (MK 801), 7-chloroquinurenate, or An example is gacyclidine (GK-11). Such treatment includes delivery to or near the round window niche of the inner ear, for example, delivery to the middle-inner ear membrane or to the annular ligaments of the rib floor. Analogues and derivatives of such drugs can be used as well.

  While preferred embodiments of the present invention have been described herein, one of ordinary skill in the art would be able to make suitable changes thereto, which are within the scope of the present invention. . For example, the present invention is not limited with respect to the representative composition used or the building material utilized. In this regard, the invention is to be construed in accordance with the only claims that follow.

Claims (3)

Use of gacyclidine in the manufacture of a medicament for treating an inner ear disease caused by abnormal glutamate-mediated neurotransmission in a subject, wherein gacyclidine is administered to the inner ear via a round window membrane, The use as described above, which provides for modulation of glutamate-mediated neurotransmission without causing significant clinical hearing loss associated with inhibition of AMPA receptor-mediated signals, thereby treating inner ear disease in said subject.   The use according to claim 1, wherein gacyclidine is administered by diffusion through the membrane of the middle ear to the inner ear.   The use according to claim 1, wherein the inner ear disease in the subject is tinnitus.

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