Purpose: A population pharmacokinetic (PK) analysis of the anti-fibroblast growth factor receptor 2b antibody, bemarituzumab, was performed to evaluate the impact of covariates on the PK and assess whether dose adjustment is necessary for a future phase 3 trial.

Methods: Serum concentration data were obtained from three clinical trials, with 1552 bemarituzumab serum samples from 173 patients, and were analyzed using nonlinear mixed-effects modeling.

Results: A two-compartment model with parallel linear and nonlinear (Michaelis-Menten) elimination from the central compartment best described the bemarituzumab serum concentration data. The final model estimated a typical linear clearance (CL) of 0.311 L/day, volume of distribution in the central compartment (Vc) of 3.58 L, distribution clearance (Q) of 0.952 L/day, volume of distribution in the peripheral compartment (Vp) of 2.71 L, maximum drug elimination by nonlinear clearance (Vmax) of 2.80 μg/day, and Michaelis-Menten constant (Km) of 4.45 μg/mL. Baseline body weight, baseline albumin, gender, and chemotherapy were identified as statistically significant covariates on the PK of bemarituzumab. Given the low interindividual variability of bemarituzumab key PK parameters (CL and Vc) and the small or modest effect of all statistically significant covariates on bemarituzumab exposure at steady-state, no covariate is expected to have clinically meaningful effects on bemarituzumab exposure.

Conclusion: No covariate had a clinically meaningful impact on bemarituzumab exposure. These results indicate that dose adjustment of bemarituzumab is not necessary, based on the aforementioned covariates, for a future phase 3 trial in gastric and gastroesophageal junction adenocarcinoma population with FGFR2b overexpression in combination with mFOLFOX6.