A randomized, double-blind, placebo-controlled phase 2 study of intratympanic OTO-313 in patients with moderate to severe subjective tinnitus.

PURPOSE: This was a randomized, double-blind, placebo-controlled Phase 2 study to evaluate the efficacy and safety of intratympanic OTO-313 in patients with subjective unilateral tinnitus. METHODS: Patients with moderate to severe unilateral tinnitus of 2-12 months duration were enrolled. A single intratympanic injection of OTO-313 or placebo was administered to the affected ear and patients were evaluated during a 16-weeks follow-up period. Efficacy was assessed using the Tinnitus Functional Index (TFI), daily ratings of tinnitus loudness and annoyance, and Patient Global Impression of Change (PGIC). RESULTS: Intratympanic administration of OTO-313 and placebo produced reductions in tinnitus with a similar percentage of TFI responders at Weeks 4, 8, 12, and 16. Reductions in daily ratings of tinnitus loudness and annoyance, and PGIC scores were also similar between OTO-313 and placebo groups. No significant differences in mean TFI scores between OTO-313 and placebo were observed for pre-specified strata regarding tinnitus duration (≥ 2 to ≤ 6 months and > 6 to ≤ 12 months) and TFI baseline scores (≥ 32 to ≤ 53 points and ≥ 54 to 100 points), although the results numerically favored OTO-313 in patients in the ≥ 2 to ≤ 6 months strata. These results also demonstrated an unexpectedly high placebo response particularly amongst patients with chronic tinnitus, despite training implemented to mitigate placebo response. OTO-313 was well-tolerated with a similar incidence of adverse events compared to placebo. CONCLUSIONS: OTO-313 did not demonstrate a significant treatment benefit relative to placebo due in part to a high placebo response. OTO-313 was safe and well-tolerated.

Efficacy of Intratympanic OTO-104 for the Treatment of Ménière's Disease: The Outcome of Three Randomized, Double-Blind, Placebo-Controlled Studies.

OBJECTIVE: To determine the efficacy of intratympanic OTO-104 for the treatment of Ménière's disease. STUDY DESIGNS: Three randomized, double-blind, placebo-controlled, multicenter studies of OTO-104 in patients with Ménière's disease. SETTING: The United States and throughout Europe. PATIENTS: Individuals with Ménière's disease aged 18 to 85 years. INTERVENTIONS: All three studies were conducted according to a similar protocol, whereby after a 1-month lead-in period, eligible patients received a single intratympanic injection of either 12 mg OTO-104 (otic formulation of dexamethasone in thermosensitive poloxamer) or placebo (1:1) and were observed for 3 months. MAIN OUTCOME MEASURES: The primary efficacy endpoint was measured by the number of definitive vertigo days (DVDs) at month 3. Secondary objective was OTO-104 safety and tolerability including adverse events, audiometry, tympanometry, and otoscopic examinations. RESULTS: Although OTO-104 demonstrated numerically greater reductions in DVD compared with placebo across all three studies, statistical significance versus placebo (primary efficacy endpoint) was only achieved in one study, the AVERTS-2 study (n = 174, p = 0.029). Secondary vertigo efficacy endpoints were statistically significant at month 3 in that study including vertigo severity, the effect of vertigo on daily activity (days at home sick or bedridden), and vertigo frequency. In the AVERTS-1 study, which did not meet the primary endpoint, a subgroup analysis of the 115 patients (69.7% of study population) who did not previously receive intratympanic steroid injections demonstrated that OTO-104 patients had significantly lower mean DVD at month 3 than patients receiving placebo (1.9 for OTO-104 versus 3.0 for placebo; p = 0.045). Importantly, a significant placebo response was observed across studies in Ménière's disease patients. OTO-104 and the intratympanic injection procedure were well tolerated. CONCLUSIONS: In all three high-quality, randomized, double-blind, placebo-controlled, multicenter studies, a single intratympanic injection of 12 mg OTO-104 demonstrated numerically greater reductions in vertigo versus placebo in patients with Ménière's disease, but statistical separation from placebo was demonstrated in only one of the studies. OTO-104 was safe and well tolerated.(Otonomy, Inc. funded; NCT02717442, NCT02612337, NCT03664674).

A neurotrophic approach to treating hearing loss: Translation from animal models to clinical proof-of-concept.

Currently, there are no approved medicines available for the treatment of hearing loss. However, research over the past two decades has contributed to a growing understanding of the pathological mechanisms in the cochlea that result in hearing difficulties. The concept that a loss of the synapses connecting inner hair cells with the auditory nerve (cochlear synaptopathy) contributes to hearing loss has gained considerable attention. Both animal and human post-mortem studies support the idea that these synapses (ribbon synapses) are highly vulnerable to noise, ototoxicity, and the aging process. Their degeneration has been suggested as an important factor in the speech-in-noise difficulties commonly experienced by those suffering with hearing loss. Neurotrophins such as brain derived neurotrophic factor (BDNF) have the potential to restore these synapses and provide improved hearing function. OTO-413 is a sustained exposure formulation of BDNF suitable for intratympanic administration that in preclinical models has shown the ability to restore ribbon synapses and provide functional hearing benefit. A phase 1/2 clinical trial with OTO-413 has provided initial proof-of-concept for improved speech-in-noise hearing performance in subjects with hearing loss. Key considerations for the design of this clinical study, including aspects of the speech-in-noise assessments, are discussed.

Intratympanic Administration of OTO-313 Reduces Tinnitus in Patients With Moderate to Severe, Persistent Tinnitus: A Phase 1/2 Study.

OBJECTIVE: To evaluate the safety and exploratory efficacy of intratympanic administration of OTO-313 in patients with tinnitus. STUDY DESIGN: Single intratympanic injection of OTO-313 evaluated in a randomized, double-blind, placebo-controlled Phase 1/2 clinical study. SETTING: Tertiary referral centers. PATIENTS: Patients with unilateral tinnitus (moderate-severe) with tinnitus duration 1 to 6 months. INTERVENTIONS: Intratympanic OTO-313. MAIN OUTCOME MEASURES: Safety and change from baseline in tinnitus functional index (TFI), daily ratings of tinnitus loudness and annoyance, and patient global impression of change (PGIC). RESULTS: OTO-313 was well-tolerated with lower incidence of adverse events than placebo. Mean TFI reduction from baseline favored OTO-313 at Week 2, 4, and 8. A clinically meaningful, 13-point improvement on the TFI was observed in 43% (6/14) of OTO-313 patients at both Weeks 4 and 8 versus 13% (2/16) of placebo patients (ad hoc responder analysis, p-value < 0.05). Reductions in daily ratings of tinnitus loudness and annoyance favored OTO-313 compared with placebo. In OTO-313 responders, a strong correlation existed between change from baseline in TFI score and changes in tinnitus loudness, tinnitus annoyance, and PGIC. CONCLUSIONS: OTO-313 was well-tolerated and demonstrated a higher proportion of responders than placebo across consecutive visits (Weeks 4 and 8) supporting further clinical development of OTO-313 for the treatment of tinnitus.

Dipyridyl amines: potent metabotropic glutamate subtype 5 receptor antagonists.

Modulation of the metabotropic glutamate subtype 5 (mGlu5) receptor may be useful in the treatment of a variety of central nervous system disorders. Herein, we report on the discovery, synthesis, and biological evaluation of dipyridyl amines as small molecule mGlu5 antagonists.

Reductions in beta-amyloid concentrations in vivo by the gamma-secretase inhibitors BMS-289948 and BMS-299897.

A primary pathological feature of Alzheimer's disease is beta-amyloid (Abeta)-containing plaques in brain and cerebral vasculature. Reductions in the formation of Abeta peptides by gamma-secretase inhibitors may be a viable therapy for reducing Abeta in Alzheimer's disease. Here we report on the effects of two orally active gamma-secretase inhibitors. BMS-289948 (4-chloro-N-(2,5-difluorophenyl)-N-((1R)-{4-fluoro-2-[3-(1H-imidazol-1-yl)propyl]phenyl}ethyl)benzenesulfonamide hydrochloride) and BMS-299897 (4-[2-((1R)-1-{[(4-chlorophenyl)sulfonyl]-2,5-difluoroanilino}ethyl)-5-fluorophenyl]butanoic acid) markedly reduced both brain and plasma Abeta(1-40) in APP-YAC mice with ED(50) values of 86 and 22 mg/kg per os (po), respectively, for BMS-289948, and 30 and 16 mg/kg po, respectively, for BMS-299897. Both compounds also dose-dependently increased brain concentrations of APP carboxy-terminal fragments, consistent with inhibition of gamma-secretase. BMS-289948 and BMS-299897 (100 mg/kg po) reduced brain and plasma Abeta(1-40) rapidly (within 20min) and maximally within 3 h. BMS-299897 also dose-dependently reduced cortical, cerebrospinal fluid (CSF), and plasma Abeta in guinea pigs with ED(50) values of 30 mg/kg intraperitoneally, without affecting CSF levels of alpha-sAPP. The reductions in cortical Abeta correlated significantly with the reductions in both plasma (r(2) = 0.77) and CSF (r(2) = 0.61) Abeta. The decreases in Abeta were apparent at 3 and 6 h post-administration of BMS-299897, but not at 12h. These results demonstrate that BMS-289948 and BMS-299897 are orally bioavailable, functional gamma-secretase inhibitors with the ability to markedly reduce Abeta peptide concentrations in APP-YAC transgenic mice and in guinea pigs. These compounds may be useful pharmacologically for examining the effects of reductions in beta-amyloid peptides in both animal models and in Alzheimer's disease.

The behavioral profile of the potent and selective mGlu5 receptor antagonist 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP) in rodent models of anxiety.

Previous reports have demonstrated the anxiolytic effect of the potent and systemically active metabotropic glutamate subtype 5 (mGlu5) receptor antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP) in rodents. Here, we present evidence for the anxiolytic activity of a novel mGlu5 receptor antagonist, 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP), in rats and compare its profile to the benzodiazepine receptor agonist diazepam. MTEP occupied mGlu5 receptors in a dose-dependent manner with essentially full receptor occupancy at the highest dose tested (10 mg/kg, i.p.). At doses appropriate for mGlu5 receptor-mediated effects, MTEP significantly reduced fear-potentiated startle and increased punished responding in a modified Geller-Seifter conflict model consistent with an anxiolytic-like profile. In both models, the magnitude of the anxiolytic-like response was similar to that seen with diazepam. In contrast, MTEP decreased unpunished responding to a lesser extent than diazepam and had no effect on rotarod performance when administered either alone or in combination with ethanol. Repeated dosing with MTEP in this model eliminated the increase in punished responding observed with acute dosing. The present results suggest that mGlu5 receptor antagonists lack the side effects seen with benzodiazepines, such as sedation and ethanol interaction, and provide insight into a possible role for mGlu5 receptor antagonists in the modulation of mood disorders.

5-[(2-Methyl-1,3-thiazol-4-yl)ethynyl]-2,3'-bipyridine: a highly potent, orally active metabotropic glutamate subtype 5 (mGlu5) receptor antagonist with anxiolytic activity.

Structure-activity relationship studies leading to the discovery of a new, orally active mGlu5 receptor antagonist are described. The title compound, 5-[(2-methyl-1,3-thiazol-4-yl)ethynyl]-2,3'-bipyridine, is highly potent in vitro, has good in vivo receptor occupancy, and is efficacious in the rat fear-potentiated startle model of anxiety following oral dosing.

Discovery of novel modulators of metabotropic glutamate receptor subtype-5.

A series of potent and selective mGluR5 antagonists were synthesized and evaluated in vitro and in vivo. It was found that a pyridyl functionality is a potential replacement for acetonitrile in the lead structure, with 2-pyridyl being most favored. Additionally, the benzoxazole moiety could also be replaced by other heterobicyclic rings such as imidazothiazole.

In vivo receptor occupancy of mGlu5 receptor antagonists using the novel radioligand [3H]3-methoxy-5-(pyridin-2-ylethynyl)pyridine).

In vivo receptor occupancy of mGlu5 receptor antagonists was quantified in rat and mouse brain using the mGlu5 receptor selective antagonist [3H]3-methoxy-5-(pyridin-2-ylethynyl)pyridine) ([3H]methoxy-PEPy). Administration of [3H]methoxy-PEPy (50 microCi/kg i.v.) to mGlu5 receptor-deficient mice revealed binding at background levels in forebrain, whereas wild-type mice exhibited 14-fold higher binding in forebrain relative to cerebellum. Systemic administration of the mGlu5 receptor antagonists 2-methyl-6-(phenylethynyl)pyridine (MPEP) and 3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (MTEP) reduced the binding of [3H]methoxy-PEPy in rats and mice, reflecting mGlu5 receptor occupancy by these compounds. MPEP (10 mg/kg i.p.) and MTEP (3 mg/kg i.p.) maintained >75% receptor occupancy for 2 h in rats, while in mice MPEP and MTEP achieved >75% occupancy for only 30 and 15 min, respectively. Compound levels in plasma were substantially lower in mice suggesting species differences in receptor occupancy result from differences in absorption or metabolism of the compounds. These findings demonstrate that [3H]methoxy-PEPy is useful for determining the occupancy of mGlu5 receptors in the brain.

Group II mGlu receptor activation suppresses norepinephrine release in the ventral hippocampus and locomotor responses to acute ketamine challenge.

Group II mGlu receptor agonists (eg LY379268 and LY354740) have been shown to reverse many of the behavioral responses to PCP as well as glutamate release elicited by PCP and ketamine. In the present set of experiments, we used in vivo microdialysis to show that, in addition to reversing PCP- and ketamine-evoked glutamate release, group II mGlu receptor stimulation also prevents ketamine-evoked norepinephrine (NE) release. Pretreating animals with the mixed 2/3 metabotropic glutamate (mGlu2/3) receptor agonist LY379268 (0.3-10 mg/kg) dose-dependently inhibited ketamine (25 mg/kg)-evoked NE release in the ventral hippocampus (VHipp). Ketamine hyperactivity was also reduced in a similar dose range. Following our initial observation on NE release, we conducted a series of microinjection experiments to reveal that the inhibitory effects of LY379268 on VHipp NE release may be linked to glutamate transmission within the medial prefrontal cortex. Finally, we were able to mimic the inhibitory effects of LY379268 on ketamine-evoked NE release by using a novel mGlu2 receptor selective positive modulator. (+/-) 2,2,2-Trifluoroethyl [3-(1-methyl-butoxy)-phenyl]-pyridin-3-ylmethyl-sulfonamide (2,2,2-TEMPS, characterized through in vitro GTPgammaS binding) at a dose of 100 mg/kg significantly reduced the NE response. Together, these results demonstrate a novel means to suppress noradrenergic neurotransmission (ie by activating mGlu2 receptors) and may, therefore, have important implications for neuropsychiatric disorders in which aberrant activation of the noradrenergic system is thought to be involved.

[3H]Methoxymethyl-3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine binding to metabotropic glutamate receptor subtype 5 in rodent brain: in vitro and in vivo characterization.

The binding of [3H]methoxymethyl-3-[(2-methyl-1,3-thiazol-4-yl)ethynyl]pyridine (methoxymethyl-MTEP), a potent and selective antagonist for metabotropic glutamate (mGlu)5 receptors, was characterized in rat brain both in vitro and in vivo. Nonspecific binding, as defined with 10 microM 2-methyl-6-(phenylethynyl)-pyridine (MPEP), was less than 10% of total binding in rat brain membranes. The binding of [3H]methoxymethyl-MTEP was of high affinity (K(d) = 20 +/- 2.7 nM), saturable (B(max) = 487 +/- 48 fmol/mg protein), and to a single site. The mGlu5 antagonists methoxymethyl-MTEP and MPEP displaced [3H]methoxymethyl-MTEP binding with IC50 values of 30 and 15 nM, respectively. In vivo administration of [3H]methoxymethyl-MTEP (50 microCi/kg i.v.) revealed 12-fold higher binding in hippocampus (an area enriched in mGlu5 receptors) relative to cerebellum (an area with few mGlu5 receptors) in rats. Similarly, administration of [3H]methoxymethyl-MTEP to mGlu5-deficient mice demonstrated binding at background levels in forebrain, whereas wild-type littermates exhibited 17-fold higher binding in forebrain relative to cerebellum. Systemic administration of unlabeled mGlu5 antagonists methoxymethyl-MTEP and MPEP to rats reduced the binding of [3H]methoxymethyl-MTEP with ID50 values of 0.8 and 2 mg/kg i.p., respectively, 1 h post-treatment. The mGlu5 agonist 2-chloro-5-hydroxyphenylglycine (CHPG) (0.3, 1, and 3 micromol) dose-dependently increased phosphoinositide (PI) hydrolysis in the hippocampus after i.c.v. administration in rats. CHPG-evoked increases in PI hydrolysis were blocked with MPEP at a dose (10 mg/kg i.p.) that markedly reduced [3H]methoxymethyl-MTEP binding in vivo. These results indicate that [3H]methoxymethyl-MTEP is a selective radioligand for labeling mGlu5 and is useful for studying the binding of mGlu5 receptors in rat brain in vitro and in vivo.