Odanacatib, a Selective Cathepsin K Inhibitor, Demonstrates Comparable Pharmacodynamics and Pharmacokinetics in Older Men and Postmenopausal Women

Background: Odanacatib is a cathepsin K inhibitor in development for the treatment of osteoporosis. Evaluation of therapies to ensure that treatment effects are relevant regardless of sex is clinically important. Methods: In this double-blind, randomized controlled trial, older men (aged 50-75 years) and postmenopausal women (aged 45-75 years) were given odanacatib 50 mg once weekly or placebo for 4 weeks. Pharmacodynamic (PD) evaluation measured weighted average inhibition (WAI) of urine amino-terminal cross-linked telopeptide of type I collagen/creatinine (uNTx/Cr) after odanacatib administration. Pharmacokinetic (PK) parameter data were collected, and an analysis of sex as a factor in the PK/PD relationship was conducted. Adverse events were monitored. The hypotheses were that WAI of uNTx/Cr would be >40% (including >40% for the lower limit of the 90% confidence intervals [CIs]) for older men and postmenopausal women, that there would be no important differences in area under the curve from 0 to 168 hours (AUC(0-168) (h)) between men and women, and that odanacatib would be safe and well tolerated. Results: A total of 44 subjects (32 men and 12 women) were randomized. The least squares mean WAI (uNTx/Cr) at week 4 was 42.8% (90% CI, 35.5%-49.3%) for men and 42.7% (90% CI, 30.3% -52.9%) for women; mean values were >40%, but lower bounds were <40% as prespecified in the primary hypothesis. The differences among men and women in PD parameters were not meaningful (0.1; 90% CI, -14.7 to 14.9). PK parameters for both groups were comparable (geometric mean ratio of AUC(0-168) (h) , 0.90; 90% CI, 0.75-1.07).APK/PD analysis found that the EC50 and maximum fractional inhibition were similar in male and female subjects. There were no notable or serious adverse events in this study. Conclusions: Although the primary hypothesis was not met, there were no clinically meaningful differences in PD, PK, or PK/PD parameters between older men and postmenopausal women, supporting further research on odanacatib (50 mg once weekly) as a treatment for male osteoporosis. Odanacatib was generally well tolerated.