Discovery of [11C]MK-8056: A Selective PET Imaging Agent for the Study of mGluR2 Negative Allosteric Modulators

Modification of potent, selective metabotropic glutamate receptor 2 negative allosteric modulator (mGluR₂ NAM) led to a series of analogues with excellent binding affinity, lipophilicity, and suitable physicochemical properties for a PET tracer with convenient chemical handles for incorporation of a ¹¹C or ¹⁸F radiolabel. [¹¹C]MK-8056 was synthesized and evaluated in vivo and demonstrated appropriate affinity, selectivity, and physicochemical properties to be used as a positron emission tomography tracer for mGluR₂.

Pyridyl amides as potent inhibitors of T-type calcium channels

A novel series of amide T-type calcium channel antagonists were prepared and evaluated using in vitro and in vivo assays. Optimization of the screening hit 3 led to identification of the potent and selective T-type antagonist 37 that displayed in vivo efficacy in rodent models of epilepsy and sleep.

Short-acting T-type calcium channel antagonists significantly modify sleep architecture in rodents

A novel phenyl acetamide series of short-acting T-type calcium channel antagonists has been identified and evaluated using in vitro and in vivo assays. Heterocycle substitutions of the 4-position of the phenyl acetamides afforded potent and selective antagonists that exhibited desired short plasma half-lives across preclinical species. Lead compound TTA-A8 emerged as a compound with excellent in vivo efficacy as indicated by its significant modulation of rat sleep architecture in an EEG telemetry model, favorable pharmacokinetic properties, and excellent preclinical safety. TTA-A8 recently progressed into human clinical trials, and in line with our predictions, preliminary studies (n = 12) with a 20 mg oral dose afforded a high C max of 1.82 ± 0.274 μM with an apparent terminal half-life of 3.0 ± 1.1 h.

Discovery of 1,4-substituted piperidines as potent and selective inhibitors of T-type calcium channels

The discovery of a novel series of potent and selective T-type calcium channel antagonists is reported. Initial optimization of high-throughput screening leads afforded a 1,4-substituted piperidine amide 6 with good potency and limited selectivity over hERG and L-type channels and other off-target activities. Further SAR on reducing the basicity of the piperidine and introducing polarity led to the discovery of 3-axial fluoropiperidine 30 with a significantly improved selectivity profile. Compound 30 showed good oral bioavailability and brain penetration across species. In a rat genetic model of absence epilepsy, compound 30 demonstrated a robust reduction in the number and duration of seizures at 33 nM plasma concentration, with no cardiovascular effects at up to 5.6 microM. Compound 30 also showed good efficacy in rodent models of essential tremor and Parkinson's disease. Compound 30 thus demonstrates a wide margin between CNS and peripheral effects and is a useful tool for probing the effects of T-type calcium channel inhibition.