The safety of recombinant human hyaluronidase PH20 in nonclinical models: An overview of toxicology, pharmacology, and impact of anti-PH20 antibodies.

Hyaluronan (HA) is a glycosaminoglycan that forms a gel-like barrier in the subcutaneous (SC) space, limiting bulk fluid flow and the dispersion of SC-administered therapeutics. Recombinant human hyaluronidase PH20 (rHuPH20) facilitates the rapid delivery of co-administered therapeutics by depolymerizing HA in the SC space. Administration of rHuPH20 can induce the formation of anti-rHuPH20 antibodies, or anti-drug antibodies (ADAs), with the potential to bind endogenous PH20 hyaluronidase in the adult testes and epididymis. Using a variety of relevant animal models and multiple dose regimens of rHuPH20 across the full spectrum of animal development, we demonstrated that rHuPH20 administration resulted in the formation of ADAs. Although these ADAs can bind both the recombinant rHuPH20 enzyme and recombinant versions of animal model-specific hyaluronidases, they had no impact on fertility parameters (as measured by sperm concentration and motility, litter size, and litter viability) or fetal development. We present the result of our nonclinical studies in order of the developmental lifecycle, beginning with adults. Toxicology studies that extend beyond the standard package are also presented. These studies demonstrate the favorable safety profile of rHuPH20 and ADAs in nonclinical models. Additionally, we identified substantial safety margins for clinically relevant doses of rHuPH20.

Safety of recombinant human hyaluronidase PH20 for subcutaneous drug delivery.

INTRODUCTION: The glycosaminoglycan hyaluronan forms a gel-like substance, which presents a barrier to bulk fluid flow in the subcutaneous (SC) space, limiting SC drug delivery volume and administration rates. Recombinant human hyaluronidase PH20 (rHuPH20) acts locally to temporarily remove this barrier, facilitating rapid SC delivery of large volumes and/or high doses of sequentially or co-administered therapeutics. AREAS COVERED: An extensive clinical and post-marketing dataset of safety and immunogenicity of rHuPH20 in its current applications with approved therapeutics demonstrates that rHuPH20 acts locally, without measurable systemic absorption at the SC doses used in the approved products, and is well tolerated in combination with several co-administered therapeutic agents across diverse patient groups. The immunogenicity profile demonstrates no adverse effects associated with treatment-emergent rHuPH20 antibody responses. Immunogenicity to monoclonal antibodies co-formulated with rHuPH20 shows no clinical difference between SC and intravenous administration. Safety assessments of patient subsets for special populations, including children, elderly patients, and pregnant women, raise no additional safety concerns. EXPERT OPINION: The benefits of SC administration for patients and healthcare systems often outweigh those of intravenous administration, driving future initiation of SC-only drug development programs. Injection devices allowing large-volume SC administration could be facilitated by incorporating co-formulated biologics containing rHuPH20.