Effect of berahyaluronidase alfa on subcutaneous absorption and local tolerability of ALT-P7, an antibody-drug conjugate in preclinical studies.

Subcutaneous (SC) delivery of antibody-drug conjugates (ADCs) poses distinct challenges including the potential for local toxicity associated with cytotoxic payloads. The present study evaluated the effect of berahyaluronidase alfa (BHα) on the pharmacokinetics and local tolerability of ALT-P7, a HER2-targeting ADC, following SC injection in Yucatan minipigs and intradermal (ID) injection in Sprague-Dawley rats. ALT-P7 was administered intravenously (IV) or SC at the inguinal or dorsal site in minipigs (n = 3-5 per group), with or without BHα co-administration as a pre-mixed formulation or by sequential pre-injection. In rats, ALT-P7 was administered IV or ID with or without BHα. Serum concentrations of ALT-P7 and plasma concentrations of free monomethyl auristatin E (MMAE) were determined by ELISA and LC-MS/MS, respectively, and analyzed by non-compartmental analysis and a population pharmacokinetic model to characterize the effect of BHα on absorption kinetics. Local tolerability was assessed by macroscopic observation and severity grading of injection-site reactions and by histopathological examination. In minipigs, BHα accelerated SC absorption of ALT-P7 at both the inguinal and dorsal sites in a dose- and method-dependent manner, increasing the fraction directed to the rapid absorption pathway, while overall systemic exposure remained comparable. SC injection of ALT-P7 without BHα induced dermatologic reactions including erythema and vesicle formation. BHα was associated with reduced incidence and severity, and model-based prediction indicated correspondingly lower local ADC and payload exposure at the injection site. Comparable payload-to-ADC exposure between the IV and SC routes, together with the modeling results, was consistent with minimal presystemic payload release during the absorption process. Consistent findings were observed in rats, in which BHα significantly increased the bioavailability of ALT-P7 following ID injection. Together, this study quantitatively characterized how the dose and administration method of BHα modulate the SC absorption of ALT-P7. BHα-mediated acceleration of absorption was associated with attenuated local dermatologic toxicity and with model-predicted reductions in ADC residence and local exposure at the injection site.