Pharmacokinetics and safety of tanaproget, a nonsteroidal progesterone receptor agonist, in healthy women

Objective: This study aimed to evaluate the pharmacokinetics, pharmacodynamics and safety of the nonsteroidal Progesterone Receptor Agonist, tanaproget.

Methods: A randomized, double-blind, placebo-controlled, sequential-group study of ascending single doses of tanaproget was conducted in healthy, 25- to 45-year-old women on cycle days 8 to 12. Eight subjects (six active, two placebo) per cohort received a dose of 0.1, 0.3, 1, 3, 7 (+/-high-fat meal) or 15 mg.

Results: The maximum concentration (C(max)) of tanaproget occurred approximately 2 to 3 h after administration. The elimination half-life (t(1/2)) ranged from 12 to 30 h, and the oral clearance was approximately 70 L/h. The pharmacokinetics of tanaproget was not noticeably altered with a high-fat meal. All doses of tanaproget decreased cervical mucus scores (using a modified Insler method), indicating poor production and poor quality of cervical mucus. The most frequent treatment-emergent adverse events were vaginal bleeding/spotting, abdominal cramping and vomiting; their incidence was not dose related and most events were mild.

Conclusions: Tanaproget was safe and well tolerated, decreased cervical mucus scores and had a pharmacokinetic profile acceptable for use as a once-daily oral contraceptive.