Mechanistic model of hormonal contraception.

Contraceptive drugs intended for family planning are used by the majority of married or in-union women in almost all regions of the world. The two most prevalent types of hormones associated with contraception are synthetic estrogens and progestins. Hormonal based contraceptives contain a dose of a synthetic progesterone (progestin) or a combination of a progestin and a synthetic estrogen. In this study we use mathematical modeling to understand better how these contraceptive paradigms prevent ovulation, special focus is on understanding how changes in dose impact hormonal cycling. To explain this phenomenon, we added two autocrine mechanisms essential to achieve contraception within our previous menstrual cycle models. This new model predicts mean daily blood concentrations of key hormones during a contraceptive state achieved by administering progestins, synthetic estrogens, or a combined treatment. Model outputs are compared with data from two clinical trials: one for a progestin only treatment and one for a combined hormonal treatment. Results show that contraception can be achieved with synthetic estrogen, with progestin, and by combining the two hormones. An advantage of the combined treatment is that a contraceptive state can be obtained at a lower dose of each hormone. The model studied here is qualitative in nature, but can be coupled with a pharmacokinetic/pharamacodynamic (PKPD) model providing the ability to fit exogenous inputs to specific bioavailability and affinity. A model of this type may allow insight into a specific drug's effects, which has potential to be useful in the pre-clinical trial stage identifying the lowest dose required to achieve contraception.

A phase 1 pooled PK/PD analysis of bone resorption biomarkers for odanacatib, a Cathepsin K inhibitor.

To develop a framework for evaluating the resorption effects of Cathepsin K (CatK) inhibitors and to inform dose regimen selection, a pharmacokinetic/pharmacodynamic (PK/PD) model for odanacatib (ODN) was developed based upon data from Phase 1 studies. Pooled PK/PD data from 11 studies (N = 249) were fit reasonably to a population inhibitory sigmoid Emax model. Body weight on E0 (baseline uNTx/Cr, urinary N-terminal telopeptide normalized by creatinine) and age on Emax (fractional inhibition of the biomarker response) were significant covariates for biomarker response. Simulations of typical osteoporosis patients (by age, sex and weight) indicated minimal differences between sexes in concentration-uNTx/Cr relationship. There was no evidence that regimen (daily vs. weekly dosing) influenced the PK/PD relationship of resorption inhibition for odanacatib. PK/PD models based on data from odanacatib (ODN) Phase 1 studies demonstrated that uNTx/Cr was an appropriate bone resorption biomarker for assessment of the effects of a CatK inhibitor. The models also identified the determinants of response in the PK/PD relationship for ODN (body weight on E0 and age on Emax).

Phase II dose-finding study on ovulation inhibition and cycle control associated with the use of contraceptive vaginal rings containing 17ß-estradiol and the progestagens etonogestrel or nomegestrol acetate compared to NuvaRing.

PURPOSE: To identify at least one contraceptive vaginal ring that effectively inhibits ovulation and demonstrates cycle control that is non-inferior to NuvaRing® (Merck Sharp & Dohme B.V., The Netherlands) in terms of an unscheduled bleeding incidence, with a non-inferiority margin of 10%. METHODS: This was a randomised, active controlled, parallel group, multicentre, partially blinded trial in healthy women 18-35 years of age. Subjects received one of six contraceptive vaginal rings with an average daily release rate of 300 µg 17ß-estradiol (E2) and various rates of either etonogestrel (ENG; 75, 100, or 125 µg/day) or nomegestrol acetate (NOMAC; 500, 700, or 900 µg/day), or the active control NuvaRing® (ENG/ethinylestradiol 120/15 µg), for three 28-day cycles. RESULTS: Ovulation inhibition was observed in all groups as confirmed by absence of progesterone concentrations compatible with ovulation (>16 nmol/L) and absence of ultrasound evidence of ovulation. All investigational rings provided good cycle control, with the ENG-E2 125/300 µg/day group being associated with the best cycle control based on the numerically lowest incidence of unscheduled bleeding and absence of scheduled bleeding. Non-inferiority to NuvaRing® with respect to the incidence of unscheduled bleeding could not be concluded for any of the investigational ring groups. The safety profile was consistent with the known safety profile of combined estrogen/progestin contraceptives and similar across all groups. CONCLUSIONS: Contraceptive rings releasing 300 µg E2 and 75-125 µg/day of ENG or 500-900 µg/day of NOMAC provided adequate ovulation inhibition and cycle control and are generally well-tolerated. While non-inferiority to NuvaRing® was not met, among the investigational rings, the ENG-E2 125/300 ring provided the best cycle control.

Cryo-EM structures of inhibitory antibodies complexed with arginase 1 provide insight into mechanism of action.

Human Arginase 1 (hArg1) is a metalloenzyme that catalyzes the hydrolysis of L-arginine to L-ornithine and urea, and modulates T-cell-mediated immune response. Arginase-targeted therapies have been pursued across several disease areas including immunology, oncology, nervous system dysfunction, and cardiovascular dysfunction and diseases. Currently, all published hArg1 inhibitors are small molecules usually less than 350 Da in size. Here we report the cryo-electron microscopy structures of potent and inhibitory anti-hArg antibodies bound to hArg1 which form distinct macromolecular complexes that are greater than 650 kDa. With local resolutions of 3.5 Å or better we unambiguously mapped epitopes and paratopes for all five antibodies and determined that the antibodies act through orthosteric and allosteric mechanisms. These hArg1:antibody complexes present an alternative mechanism to inhibit hArg1 activity and highlight the ability to utilize antibodies as probes in the discovery and development of peptide and small molecule inhibitors for enzymes in general.

Early Clinical Development Planning via Biomarkers, Clinical Endpoints, and Simulation: A Case Study to Optimize for Phase 3 Dose Selection.

BACKGROUND: This study investigated a framework that leverages the relationship between biomarkers and a target clinical endpoint to optimize an early development plan. METHODS: Different biomarker designs were assessed for proof of concept (PoC) and dose finding (DF) to improve phase 2b (Ph2b) design as well as phase 3 (Ph3) dose choice. A case study using a Bayesian trivariate normal distribution model for 2 biomarkers and a clinically relevant endpoint was utilized with simulation to assess performance characteristics. RESULTS: We found the following: (1) at typical sample sizes for early development trials, biomarkers appear useful for PoC but not for clinical endpoint DF; and (2) even with large amounts of prior information and near perfect correlation between biomarkers and clinical endpoints, Ph2b variability is only overcome by increased Ph2b sample sizes to improve Ph3 dose choice. CONCLUSIONS: For highly variable clinical endpoints, the fastest path should be to demonstrate PoC by biomarkers and then go directly to Ph2b to measure the target clinical endpoint.