Across-Species Scaling of Monoclonal Antibody Pharmacokinetics Using a Minimal PBPK Model

Purpose: To examine the across-species scalability of monoclonal antibody (mAb) pharmacokinetics (PK) and assess similarities in tissue distribution across species using a recently developed minimal PBPK (mPBPK) model. Methods: Twelve sets of antibody PK data from various species were obtained from the literature, which were jointly and individually analyzed. In joint analysis, vascular reflection coefficients for tissues with either tight (σ ₁ ) or leaky endothelium (σ ₂ ) were assumed consistent across species with systemic clearance allometrically scaled (CL∈=∈-rfaut·BW ^b ). Four parameters (σ ₁, σ ₂, a, and b) were estimated in the joint analysis. In addition, the PK from each species was individually analyzed to assess species similarities in tissue distribution. Results: Twelve mAb PK profiles were well-captured by the mPBPK model in the joint analysis. The estimated σ ₁ ranged 0.690 to 0.999 with an average of 0.908; and σ ₂ ranged 0.258 to 0.841 with an average of 0.579. Clearance was reasonably scaled and b ranged 0.695 to 1.27 averaging 0.91. Predictions of plasma concentrations for erlizumab and canakinumab in humans using parameters obtained from fitting animal data were consistent with actual measurements. Conclusions: Therapeutic mAbs given IV usually exhibit biexponential kinetics with their distribution properties best captured using physiological concepts. The mPBPK modeling approach may facilitate efforts in translating antibody distribution and overall PK across species.