Background Pembrolizumab is approved for multiple cancer types at 200 mg and 2 mg/kg dose every 3 weeks (Q3W). We used a model-based approach to compare the exposure of pembrolizumab 400 mg dose every 6 weeks (Q6W) with the Q3W regimens. Methods The Q6W dose was selected by matching exposure with the 200 mg and 2 mg/kg Q3W doses. Concentration-time profiles were simulated using the established population pharmacokinetic model of pembrolizumab based on 2993 subjects from five clinical trials across tumour types. Efficacy was bridged by evaluating projections of average concentration over the dosing interval (Cavg) and trough concentration (Cmin) at steady state (ss). Safety was bridged by ensuring that concentrations were below those at 10 mg/kg dose every 2 weeks (Q2W), the maximum clinical dose. Results The 400 mg Q6W dose had similar predicted exposure (Cavg,ss, geometric mean ∼1% higher) as the 200 mg Q3W dose. Fewer than 1% of subjects had transiently lower Cmin,ss than that observed for 200 mg and 2 mg/kg Q3W. Despite these reductions, similar target saturation is expected. The predicted peak concentrations (Cmax,ss) for 400 mg Q6W were substantially (∼65%) lower than the 10 mg/kg Q2W dose. Conclusions Exposures expected for pembrolizumab 400 mg Q6W were similar to the 200 mg and 2 mg/kg Q3W and below the 10 mg/kg Q2W regimens. Established exposure-response relationships for pembrolizumab over a 5-fold dose range (2 mg/kg Q3W to 10 mg Q2W) support that clinical efficacy and safety of 400 mg Q6W would be similar to the 200 mg and 2 mg/kg Q3W doses across tumour types. Clinical trial registration numbers NCT01295827, NCT01704287, NCT01866319, NCT01905657, NCT02142738.
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