(T0930-01-05) Preclinical Subcutaneous Injectability and Local Tolerability of an Antibody-Drug Conjugate Delivered with Recombinant Human Hyaluronidase PH20 Using a Handheld High-Volume Auto-Injector

Purpose: Antibody-drug conjugates (ADCs) are intended for focused delivery of toxic chemotherapeutics. Typically, ADCs are delivered intravenously due to large dose requirements and concerns of potential toxicities associated with premature payload release if administered via other parenteral routes. Recombinant human hyaluronidase PH20 (rHuPH20) is a highly purified, recombinant form of the naturally occurring human hyaluronidase PH20 enzyme (Frost 2007). rHuPH20 facilitates the rapid delivery of large volumes subcutaneously (SC), while increasing the dispersion and absorption at the SC injection site, thereby reducing the local residence time of the injected drug and associated toxicities (Locke et al 2019). Recently, rapid, large volume, SC drug delivery with rHuPH20 has been conducted using prototype high-volume auto-injectors (HVAIs). SC administration using a HVAI may provide easier at-home delivery by a healthcare professional or caregiver. The purpose of this study was to assess the feasibility and local tolerability of SC administration of an ADC in the absence or presence of rHuPH20, using a HVAI, in a Yucatan miniature pig (minipig) model.

Methods: The minipig was chosen as the preclinical model due to the anatomical and physiological similarities of the skin to that of humans, including epidermal thickness, permeability, general morphology, cellular composition, immunological reactivity, and metabolic properties (Mahl et al 2006, Kang et al 2013). Animals were anesthetized with isoflurane gas and placed in dorsal recumbence. ADC (sacituzumab govitecan) solution was prepared according to the manufacturer’s instructions. Each animal received two 10 mL SC injections to the lower abdominal region. One injection contained the ADC alone (control) and the subsequent injection contained the ADC co-mixed with rHuPH20. Each injection was administered using the HVAI. Quantitative endpoints were assessed that included measurement of injection time, back-leakage, and post-injection swelling. Qualitative endpoints were also assessed using a modified 5-point Draize scoring scale to evaluate erythema, swelling, and induration at the local injection site over time. All qualitative assessments were performed by independent scorers immediately post-injection and at 24, 48, and 72 hours. After the 72 hour observation timepoint, animals were humanely euthanized, and a 12 mm full-thickness tissue punch biopsy was obtained from each injection site. The tissue biopsy was then fixed in 10% formalin, paraffin embedded, sectioned (5 µM), and stained with hematoxylin and eosin. Slides were then evaluated for histopathological findings by an independent pathologist.

Results: HVAI injections that included rHuPH20 were approximately 10% faster than injections of the ADC alone. In addition, injections of ADC + rHuPH20 displayed minimal to no back-leakage of the test solution (0.9 mg vs. 37.0 mg; -98%). Bleb swelling was also significantly (p ≤ 0.05) reduced in both volume and height, indicative of the rapid dispersion of the ADC when co-It injected with rHuPH20. Qualitative assessments of swelling size and induration showed that the HVAI injections of ADC + rHuPH20 were significantly (p ≤ 0.05) smaller and resolved faster than the control ADC injections alone (-42%). In addition, the post-injection blebs (swelling) were significantly (p ≤ 0.05) softer (not indurated) compared to the injections of ADC alone (-55%). By 24 hours post-injection, no swelling or induration was visible for any of the injections. Histopathology of the tissue sections indicated that control injections of the ADC alone showed mild focal epithelial keratosis in all levels of the tissue sample (dermis, SC, muscle) in 33% of injection sites. In contrast, no findings were observed with injections of ADC + rHuPH20.

Conclusion: This study demonstrated that the addition of rHuPH20 can facilitate a rapid 10 mL SC injection of an ADC using a HVAI. Furthermore, the enzyme may potentiate the safe SC administration of an ADC, as it promotes rapid dispersion of drug from the injection site, which resulted in significantly smaller injection site swelling and firmness. Importantly, no histopathological changes occurred for injections of ADC + rHuPH20, whereas 1 out of 3 injections of the ADC alone exhibited pathological findings. This study indicated that SC delivery of an ADC + rHuPH20 delivered using a HVAI is feasible and locally tolerable, and it may provide a potential option as a convenient and tolerable at-home delivery method.

References: 1. Frost GI. Recombinant human hyaluronidase (rHuPH20): an enabling platform for subcutaneous drug and fluid administration. Expert opinion on drug delivery. 2007;4(4):427-40. https://doi.org/10.1517/17425247.4.4.427.
2. Locke KW, Maneval DC, LaBarre MJ. ENHANZE® drug delivery technology: a novel approach to subcutaneous administration using recombinant human hyaluronidase PH20. Drug delivery. 2019;26(1):98-106. https://doi.org/10.1080/10717544.2018.1551442.
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