Sotatercept is a breakthrough, first-in-class biologic, recently approved by the Food and Drug Administration (FDA) for the treatment of pulmonary arterial hypertension (PAH). Exposure-response (E-R) analyses and pharmacokinetic/pharmacodynamic (PK/PD) modeling were performed for sotatercept after intravenous and subcutaneous (SC) administrations. Clinical endpoints included 6-minute walk distance (6MWD), pulmonary vascular resistance (PVR), and probability of N-terminal pro-B natriuretic peptide (NT-proBNP) concentrations < 300 pg/mL for efficacy, and hemoglobin (Hgb) for safety from two Phase 1 studies, two Phase 2 studies, and one Phase 3 study. E-R models using nonlinear mixed effect modeling approach were developed for 6MWD and PVR, while Cox proportional hazards model and semi-mechanistic PK/PD model were used for NT-proBNP and Hgb. Covariate analyses were conducted to identify significant predictors of variability for each of these clinical endpoints. Modeling results showed that increasing sotatercept average concentration (Cavg) at week 24 is associated with increased predicted 6MWD, increased probability of NT-proBNP concentration < 300 pg/mL, decreased predicted PVR, and increased Hgb which was clinically manageable. All these responses approached their corresponding plateaus at a Cavg range associated with the dose of 0.7 mg/kg Q3W SC. Statistically relevant covariates included age and iron supplementation which slightly increased Hgb-mediated effect for 6MWD, PAH disease duration, and baseline therapy infusion with prostacyclin for PVR, and WHO functional class for NT-proBNP. The magnitudes of the impact of these covariates are not clinically meaningful. Taken together, these results support an appropriate benefit-risk profile for the FDA-approved target dose for sotatercept of 0.7 mg/kg Q3W SC.
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