Lead Optimization and Avoidance of Reactive Metabolite Leading to PCO371, a Potent, Selective, and Orally Available Human Parathyroid Hormone Receptor 1 (hPTHR1) Agonist

We have previously shown that the
oral administration of the small
molecule hPTHR1 agonist PCO371 and its lead compound, 1 (CH5447240) results in PTH-like calcemic and hypophostemic activity
in thyroparathyroidectomized rats. However, 1 was converted
to a reactive metabolite in a human liver microsome assay. In this
article, we report on the modification path that led to an enhancement
of PTHR1 agonistic activity and reduction in the formation of a reactive
metabolite to result in a potent, selective, and orally active PTHR1
agonist 1-(3,5-dimethyl-4-(2-((4-oxo-2-(4-(trifluoromethoxy)­phenyl)-1,3,8-triazaspiro[4.5]­dec-1-en-8-yl)­sulfonyl)­ethyl)­phenyl)-5,5-dimethylimidazolidine-2,4-dione
(PCO371, 16c). This compound is currently being evaluated
in a phase 1 clinical study for the treatment of hypoparathyroidism.