Inactivated hemagglutinating virus of Japan envelope (HVJ-E) have an anti-tumor effect and tumor immunity. We conducted an open-label, phase I, dose-escalation study in patients with castration-resistant prostate cancer (CRPC) to determine the safety and efficacy of intratumoral and subcutaneous injection of HVJ-E (GEN0101). Patients with CRPC, who were resistant to or unable to receive standard of care, were included. GEN0101 was injected directly into the prostate and subcutaneously in two 28-day treatment cycles. The primary end points were to evaluate safety and tolerability of GEN0101 and determine its recommended dose. The secondary end points were to analyze anti-tumor effect and tumor immunity. Three patients received 30,000 mNAU of GEN0101 while 6 received 60,000 mNAU. There was no dose-limiting toxicity, and the recommended dose of GEN0101 was defined to be 60,000 mNAU. Radiographically, one patient had stable disease and 2 had progressive disease in the low-dose group, whereas 5 patients had stable disease and one had progressive disease in the high-dose group. Three patients in the high-dose group showed reduction in lymph node metastasis. PSA increase rates in the high-dose group were suppressed more than those in the low-dose group. NK cell activity was enhanced in 2 patients of the low-dose group and in 5 patients in the high-dose group. In conclusions, intratumoral and subcutaneous injections of GEN0101 were well tolerated and feasible to use. The study is registered at UMIN Clinical Trials Registry, number UMIN000017092.
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