James Mulhearn

Characterization of non-nitrocatechol pan and isoform specific catechol-O-methyltransferase inhibitors and substrates.

Reduced dopamine neurotransmission in the prefrontal cortex has been implicated as causal for the negative symptoms and cognitive deficit associated with schizophrenia; thus, a compound which selectively enhances dopamine neurotransmission in the prefrontal cortex may have therapeutic potential. Inhibition of catechol-O-methyltransferase (COMT, EC 2.1.1.6) offers a unique advantage, since this enzyme is the primary mechanism for the elimination of dopamine in cortical areas. Since membrane bound COMT (MB-COMT) is the predominant isoform in human brain, a high throughput screen (HTS) to identify novel MB-COMT specific inhibitors was completed. Subsequent optimization led to the identification of novel, non-nitrocatechol COMT inhibitors, some of which interact specifically with MB-COMT. Compounds were characterized for in vitro efficacy versus human and rat MB and soluble (S)-COMT. Select compounds were administered to male Wistar rats, and ex vivo COMT activity, compound levels in plasma and cerebrospinal fluid (CSF), and CSF dopamine metabolite levels were determined as measures of preclinical efficacy. Finally, novel non-nitrocatechol COMT inhibitors displayed less potent uncoupling of the mitochondrial membrane potential (MMP) compared to tolcapone as well as nonhepatotoxic entacapone, thus mitigating the risk of hepatotoxicity.

[ 18F]Fluoroazabenzoxazoles as potential amyloid plaque PET tracers: Synthesis and in vivo evaluation in rhesus monkey

INTRODUCTION An (18)F-labeled positron emission tomography (PET) tracer for amyloid plaque is desirable for early diagnosis of Alzheimers disease, particularly to enable preventative treatment once effective therapeutics are available. Similarly, such a tracer would be useful as a biomarker for enrollment of patients in clinical trials for evaluation of antiamyloid therapeutics. Furthermore, changes in the level of plaque burden as quantified by an amyloid plaque PET tracer may provide valuable insights into the effectiveness of amyloid-targeted therapeutics. This work describes our approach to evaluate and select a candidate PET tracer for in vivo quantification of human amyloid plaque. METHODS Ligands were evaluated for their in vitro binding to human amyloid plaques, lipophilicity and predicted blood-brain barrier permeability. Candidates with favorable in vitro properties were radiolabeled with (18)F and evaluated in vivo. Baseline PET scans in rhesus monkey were conducted to evaluate the regional distribution and kinetics of each tracer using tracer kinetic modeling methods. High binding potential in cerebral white matter and cortical grey matter was considered an unfavorable feature of the candidate tracers. RESULTS [(18)F]MK-3328 showed the most favorable combination of low in vivo binding potential in white matter and cortical grey matter in rhesus monkeys, low lipophilicity (Log D=2.91) and high affinity for human amyloid plaques (IC(50)=10.5±1.3 nM). CONCLUSIONS [(18)F]MK-3328 was identified as a promising PET tracer for in vivo quantification of amyloid plaques, and further evaluation in humans is warranted.

Benzoxazolinone aryl sulfonamides as potent, selective Na v 1.7 inhibitors with in vivo efficacy in a preclinical pain model

Studies on human genetics have suggested that inhibitors of the Nav1.7 voltage-gated sodium channel hold considerable promise as therapies for the treatment of chronic pain syndromes. Herein, we report novel, peripherally-restricted benzoxazolinone aryl sulfonamides as potent Nav1.7 inhibitors with excellent selectivity against the Nav1.5 isoform, which is expressed in the heart muscle. Elaboration of initial lead compound 3d afforded exemplar 13, which featured attractive physicochemical properties, outstanding lipophilic ligand efficiency and pharmacological selectivity against Nav1.5 exceeding 1000-fold. Key structure-activity relationships associated with oral bioavailability were leveraged to discover compound 17, which exhibited a comparable potency/selectivity profile as well as full efficacy following oral administration in a preclinical model indicative of antinociceptive behavior.

Synthesis and Evaluation of 5-Fluoro-2-aryloxazolo[5,4-b]pyridines as β-Amyloid PET Ligands and Identification of MK-3328.

5-Fluoro-2-aryloxazolo[5,4-b]pyridines were synthesized and investigated as potential (18)F containing β-amyloid PET ligands. In competition binding assays using human AD brain homogenates, compounds 14b, 16b, and 17b were identified as having favorable potency versus human β-amyloid plaque and were radiolabeled for further evaluation in in vitro binding and in vivo PET imaging experiments. These studies led to the identification of 17b (MK-3328) as a candidate PET ligand for the clinical assessment of β-amyloid plaque load.

Identification of second-generation P2X3 antagonists for treatment of pain

A second-generation small molecule P2X3 receptor antagonist has been developed. The lead optimization strategy to address shortcomings of the first-generation preclinical lead compound is described herein. These studies were directed towards the identification and amelioration of preclinical hepatobiliary findings, reducing potential for drug-drug interactions, and decreasing the projected human dose of the first-generation lead.