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J Med Chem. 2017 Sep 28;60(18):7764-7780. doi: 10.1021/acs.jmedchem.7b00604. Epub 2017 Sep 13.

Discovery and Characterization of (R)-6-Neopentyl-2-(pyridin-2-ylmethoxy)-6,7-dihydropyrimido[2,1-c][1,4]oxazin-4(9H)-one (PF-06462894), an Alkyne-Lacking Metabotropic Glutamate Receptor 5 Negative Allosteric Modulator Profiled in both Rat and Nonhuman Primates.

Author information

1
Neuroscience and Pain Medicinal Chemistry, ‡Pharmacokinetics, Dynamics, and Metabolism, and §Neuroscience and Pain Research Unit, Pfizer Inc. , Cambridge, Massachusetts 02139, United States.
2
Pharmaceutical Sciences, ⊥Pharmacokinetics, Dynamics, and Metabolism, #Biostatistics, Early Clinical Development, ∇Drug Safety Research and Development, and ○BioImaging Center, Pfizer Inc. , Groton, Connecticut 06340, United States.

Abstract

We previously observed a cutaneous type IV immune response in nonhuman primates (NHP) with the mGlu5 negative allosteric modulator (NAM) 7. To determine if this adverse event was chemotype- or mechanism-based, we evaluated a distinct series of mGlu5 NAMs. Increasing the sp3 character of high-throughput screening hit 40 afforded a novel morpholinopyrimidone mGlu5 NAM series. Its prototype, (R)-6-neopentyl-2-(pyridin-2-ylmethoxy)-6,7-dihydropyrimido[2,1-c][1,4]oxazin-4(9H)-one (PF-06462894, 8), possessed favorable properties and a predicted low clinical dose (2 mg twice daily). Compound 8 did not show any evidence of immune activation in a mouse drug allergy model. Additionally, plasma samples from toxicology studies confirmed that 8 did not form any reactive metabolites. However, 8 caused the identical microscopic skin lesions in NHPs found with 7, albeit with lower severity. Holistically, this work supports the hypothesis that this unique toxicity may be mechanism-based although additional work is required to confirm this and determine clinical relevance.

PMID:
28817277
DOI:
10.1021/acs.jmedchem.7b00604
[Indexed for MEDLINE]

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