Characterization and Interspecies Scaling of rhTNF- α Pharmacokinetics with Minimal Physiologically Based Pharmacokinetic Models.

Tumor necrosis factor- α (TNF- α ) is a soluble cytokine and target of specific monoclonal antibodies (mAbs) and other biologic agents used in the treatment of inflammatory diseases. These biologics exert their pharmacological effects through binding and neutralizing TNF- α , and thus they prevent TNF- α from interacting with its cell surface receptors. The magnitude of the pharmacological effects is governed not only by the pharmacokinetics (PK) of mAbs, but also by the kinetic fate of TNF- α We have examined the pharmacokinetics of recombinant human TNF- α (rhTNF- α ) in rats at low doses and quantitatively characterized its pharmacokinetic features with a minimal physiologically based pharmacokinetic model. Our experimental and literature-digitalized PK data of rhTNF- α in rats across a wide range of doses were applied to global model fitting. rhTNF- α exhibits permeability rate-limited tissue distribution and its elimination is comprised of a saturable clearance pathway mediated by tumor necrosis factor receptor binding and disposition and renal filtration. The resulting model integrated with classic allometry was further used for interspecies PK scaling and resulted in model predictions that agreed well with experimental measurements in monkeys. In addition, a semimechanistic model was proposed and applied to explore the absorption kinetics of rhTNF- α following s.c. and other routes of administration. The model suggests substantial presystemic degradation of rhTNF- α for s.c. and i.m. routes and considerable lymph uptake contributing to the overall systemic absorption through the stomach wall and gastrointestinal wall routes of dosing. This report provides comprehensive modeling and key insights into the complexities of absorption and disposition of a major cytokine.