ABSTRACT
HYPOTHESIS: SENS-401 (R-azasetron besylate) is effective against severe acoustic trauma-induced hearing loss. BACKGROUND: SENS-401 has calcineurin inhibiting properties and attenuates cisplatin-induced hearing loss in a rat model. Cisplatin-induced and acoustic trauma-induced hearing loss share common apoptotic pathways. METHODS: The dose-response relationship of SENS-401 (6.6âmg/kg BID, 13.2âmg/kg BID, 26.4âmg/kg QD) and treatment time-window (13.2âmg/kg BID starting 24, 72, and 96âh posttrauma) versus placebo for 28 days were evaluated in a male rat model of severe acoustic trauma-induced hearing loss (120âdB SPL, 2âh) using auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAE) measures followed by cochlear outer hair cell (OHC) counting with myosin-VIIa immunolabeling. RESULTS: All SENS-401 doses improved ABR threshold shift and recovery, reaching statistical significance (pâ<â0.05) for ABR threshold recoveries after 28-days treatment. DPOAE amplitude loss and recovery improved markedly for 13.2âmg/kg BID SENS-401, reaching significance after 14 days (pâ<â0.05). Significant improvements in ABR threshold shifts/recovery and DPOAE amplitude loss occurred with up to 96-hours delay in initiating SENS-401 (pâ<â0.05), and in DPOAE amplitude recovery with up to 72-hours delay (pâ<â0.05). Significantly more surviving OHCs were present after SENS-401 treatment compared with placebo after 24 to 96-hours delay posttrauma, with up to 5.3-fold more cells in the basal cochlea turn. CONCLUSIONS: In vivo data support the otoprotective potential of twice daily oral SENS-401. Improvements in hearing loss recovery make SENS-401 a promising clinical candidate for acoustic trauma-induced hearing loss, including when treatment is not initiated immediately.
Subject(s)
Bridged Bicyclo Compounds, Heterocyclic/pharmacology , Evoked Potentials, Auditory, Brain Stem/drug effects , Hearing Loss, Noise-Induced/drug therapy , Hearing Loss, Sensorineural/drug therapy , Oxazines/pharmacology , Acoustic Stimulation/adverse effects , Animals , Bridged Bicyclo Compounds, Heterocyclic/administration & dosage , Bridged Bicyclo Compounds, Heterocyclic/therapeutic use , Cisplatin/toxicity , Hair Cells, Auditory, Outer/drug effects , Hearing Loss, Sensorineural/chemically induced , Male , Otoacoustic Emissions, Spontaneous/drug effects , Oxazines/administration & dosage , Oxazines/therapeutic use , Rats , Rats, WistarABSTRACT
A series of 1,5-disubstituted pyridones was identified as positive allosteric modulators (PAMs) of the metabotropic glutamate receptor 2 (mGluR2) via high throughput screening (HTS). Subsequent SAR exploration led to the identification of several compounds with improved in vitro activity. Lead compound 8 was further profiled and found to attenuate the increase in PCP induced locomotor activity in mice.
Subject(s)
Amino Acids/pharmacology , Bridged Bicyclo Compounds/pharmacology , Excitatory Amino Acid Agonists/pharmacology , Pyridines/pharmacology , Pyridones/pharmacology , Receptors, Metabotropic Glutamate/agonists , Sulfonamides/pharmacology , Allosteric Regulation , Amino Acids/chemistry , Animals , Bridged Bicyclo Compounds/chemistry , Drug Evaluation, Preclinical , Drug Stability , Excitatory Amino Acid Agonists/chemistry , Excitatory Amino Acid Agonists/classification , Humans , Hydrophobic and Hydrophilic Interactions , Mice , Molecular Structure , Motor Activity/drug effects , Pyridines/chemistry , Pyridones/chemistry , Pyridones/classification , Pyridones/isolation & purification , Recombinant Proteins/drug effects , Structure-Activity Relationship , Sulfonamides/chemistryABSTRACT
The ATP-dependent drug efflux pump P-glycoprotein (P-gp) affects the absorption and disposition of many compounds. P-gp may also play role in clinically significant drug-drug interactions. Therefore, it is important to find potential substrates or inhibitors of P-gp early in the drug discovery process. To identify compounds that interact with this transporter, several P-gp assays were validated and compared by testing a set of 28 reference compounds, including inhibitors of cytochrome P450 3A4 (CYP3A4). The assays included in silico predictions, inhibition assays (based on cellular uptake of rhodamine-123 or calcein AM), and functional assays (ATPase activity assay and transcellular transport assay, the latter for a subset of compounds). In addition, species differences were studied in an indirect fluorescence indicator screening assay and test systems expressing porcine, mouse, or human P-gp. Our results suggest that several P-gp assays should be used in combination to classify compounds as substrates or inhibitors of P-gp. Recommendations are given on screening strategies which can be applied to different phases of the drug discovery and development process.