Population pharmacokinetic modeling of molibresib and its active metabolites in patients with solid tumors: A
Anu Shilpa Krishnatry1, Alexander Voelkner2, Arindam Dhar3
1Clinical Pharmacology Modelling and Simulation, GlaxoSmithKline, Collegeville, PA, USA.
Abstract:
Molibresib (GSK525762) is an investigational, orally bioavailable, small-molecule bromodomain and extraterminal (BET) protein inhibitor for the treatment of advanced solid tumors. Molibresib was initially evaluated in a first-time-in-human (FTIH) study BET115521 consisting of two parts: Part 1 of the study (dose escalation) was conducted in 94 patients with nuclear protein in testis midline carcinoma and other solid tumors, and Part 2 (expansion cohort) was conducted in 99 patients with different solid tumor types. Molibresib is metabolized by cytochrome P450 3A4 enzymes to produce two major active metabolites that are equipotent to the parent molecule. The metabolites are measured together after full conversion of one to the other and reported as an active metabolite composite (GSK3529246). The molibresib pharmacokinetic (PK) profile has been characterized by a decrease in exposure over time, with the decrease more pronounced at higher doses, and accompanied by a slight increase of the metabolite concentrations. Autoinduction of molibresib metabolism was suspected and confirmed in vitro. Here we report the development of a semimechanistic liver-compartment population PK model using PK data from the FTIH study, which adequately describes the autoinduction of molibresib clearance and the PK of both molibresib and GSK3529246. Covariate analysis indicated body weight had a significant effect on the volume of distribution of molibresib and GSK3529246, and higher levels of aspartate aminotransferase resulted in the lower clearance of GSK3529246. This model was used to simulate individual patient exposures based on covariate information for use in future alternative dosing strategies and exposure-response analyses.
Insights
Molibresib, a novel bromodomain and extraterminal (BET) protein inhibitor, shows autoinduction of metabolism in patients with advanced solid tumors. A population pharmacokinetic model was developed to describe its behavior and inform future dosing strategies.
Area of Science:
- Pharmacology
- Oncology
- Drug Metabolism
Background:
- Molibresib (GSK525762) is an investigational oral small-molecule inhibitor targeting bromodomain and extraterminal (BET) proteins for advanced solid tumors.
- Initial clinical evaluation in a first-in-human study (BET115521) involved dose escalation and expansion cohorts across various solid tumor types.
Purpose of the Study:
- To develop a semimechanistic liver-compartment population pharmacokinetic (PK) model for molibresib and its active metabolite composite (GSK3529246).
- To characterize the PK profile, including autoinduction of metabolism, and identify influencing covariates.
Main Methods:
- Utilized PK data from the BET115521 first-in-human study.
- Developed a semimechanistic liver-compartment population PK model.
- Performed covariate analysis to assess factors affecting PK parameters.
Main Results:
- The developed PK model adequately described the autoinduction of molibresib clearance and the PK of molibresib and GSK3529246.
- Body weight significantly impacted the volume of distribution for both molibresib and GSK3529246.
- Elevated aspartate aminotransferase levels were associated with reduced GSK3529246 clearance.
Conclusions:
- The PK model successfully captures molibresib autoinduction and metabolite PK.
- The model provides a basis for simulating patient exposures and optimizing future dosing strategies.
- Understanding PK variability is crucial for effective exposure-response analyses in clinical development.
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