Synergistic anti-tumor effect of pegylated recombinant human hyaluronidase (PEGrHuPH20) with cytotoxic agents following intravenous administration in a hormone refractory prostate cancer xenograft model

A45 Hyaluronan (HA) is a major constituent of the extracellular matrix in many solid tumors, linking proteoglycans into macromolecular aggregates in the surrounding stroma. The systematic administration of HA degrading enzyme hyaluronidase may improve the response to therapeutics by selective reduction of tumor interstitial fluid pressure (IFP). The rationale of this study was to evaluate the therapeutic potential of pegylated recombinant human hyaluronidase (PEGrHuPH20) in combination with Docetaxel a short half-life small molecule a standard of care for advanced-stage hormone resistant prostate cancer, and with liposomal Doxorubicin a long half-life pegylated chemotherapy nanoparticle. We have previously shown that intravascular rHuPH20 results in a rapid and selective IFP reduction in the HA-rich PC3 peritibial tumors concomitant with reduced peritumoral HA and water content. Pegylation of rHuPH20 substantially extends native rHuPH20 plasma half-life from 0.59 min to >24 hrs, resulting in a prolonged decrease of tumor IFP to up to 72 hrs, sustained depletion of peritumoral HA, significant reduction in tumor water content, and >3 fold increase in tumor vascular volume. In vitro application of PEGrHuPH20 to PC3-GFP prostate cancer cells grown in a Matrigel three dimensional matrix demonstrated a significant reduction in tumor colony growth, indicating a requirement of pericellular HA for tumor cell expansion within matrix. We further evaluated the anti-tumor effects and toxicity of PEGrHuPH20 in combination with Docetaxel and liposomal Doxorubicin in the peritibial PC3 xenograft prostate carcinoma model. Male nude mice were inoculated IM with PC3 prostate carcinoma cells adjacent to the right tibial periosteum to generate tumors with high IFP (mean 34 ± 16 mmHg). Treatment was initiated when tumor volumes reached 400-500 mm3 and tumor growth was monitored using ultrasound. IV administration of Docetaxel + PEGrHuPH20 (10 mg/kg + 10K U/mouse) Q7Dx2 on Days 0 and 7 with additional PEGrHuPH20 dosing at 10K U/mouse on Days 3 and 10 resulted in a synergistic tumor growth inhibition over a period of 73 days that was significantly superior to that of 10 mg/kg Docetaxel or 10K U/mouse PEGrHuPH20 alone. This regimen was also effective in the PC3M-luc bone metastasis model. As assessed by body weight, complete blood chemistry and serum clinical chemistry, Docetaxel+PEGrHuPH20 treatment (10 mg/kg +10K U/m) was tolerated relatively well with no significant increase in neutropenia and was markedly better tolerated compared to Docetaxel treatment alone at MTD of 30 mg/kg, Q7Dx2. Treatment with PEGrHuPH20 alone at doses of up to 30K U/m was also well tolerated. Similarly, anti-tumor efficacy of liposomal Doxorubicin + PEGrHuPH20 (6 mg/kg + 10K U/mouse) by Q7Dx3 with additional PEGrHuPH20 dosing at 10K U/mouse was statistically significantly superior to that of liposomal Doxorubicin (6 mg/kg) treatment alone. These data demonstrate that treatment of human PC3 HRPC xenograft tumors with PEGrHuPH20 in combination with two different chemotherapeutic drugs resulted in a substantial increase in anti-tumor activity indicative of synergy. Combination of PEGrHuPH20 with cytotoxic agents may lead to more effective oncology therapies for HA producing tumors with high IFP.