Population pharmacokinetics of weight-based compared with fixed dosing of CAP256V2LS, a broadly neutralizing antibody for HIV prevention in women.

Introduction: In the development of broadly neutralizing monoclonal antibodies (bNAb) for HIV prevention, there is a need for simpler dosing strategies. This study assessed whether fixed dosing achieves comparable systemic bNAb concentrations to weight-based dosing across a range of weights.

Methods: The CAPRISA 012B trial was a first-in-human, Phase 1 dose-escalation study conducted in young, HIV-negative women (median age 25 years; IQR: 22-29) in South Africa, evaluating the subcutaneous administration of CAP256V2LS alone and in combination with VRC07-523LS. Weight-based dosing between 5 and 20 mg/kg was assessed. A fixed 1200 mg dose of CAP256V2LS and VRC07-523LS, administered alone or in combination, was evaluated in women weighing from 59.5 kg to 93.2 kg, with a median weight of 78.3 kg (IQR: 67.2-81.5). A population pharmacokinetic model was developed to describe and predict the concentration-time profiles of CAP256V2LS in participants. Model-based simulations then extended this analysis across a broader hypothetical weight range (34.2-119 kg).

Results: Model-based simulations revealed comparable exposure between the 1200 mg fixed-dose and the 20 mg/kg weight-based dosing regimens. Inter-individual variability in bioavailability and clearance was 0.212 and 0.019, respectively, and was consistent across both fixed-dose and weight-based dosing, regardless of the route of administration. Weight-based dosing of CAP256V2LS led to a mean wastage of 265.8 mg for the 5 mg/kg dose, 433.4 mg for the 10 mg/kg dose, and 324.2 mg for the 20 mg/kg dose.

Conclusions: For women weighing 60-93 kg, a fixed-dose of 1200 mg of CAP256V2LS produced similar adverse events and pharmacokinetic profiles as weight-based dosing. The fixed dose reduced variability in the plasma concentrations and product wastage compared with weight-based dosing.