An open label, multicenter, phase I/II study of RP1 as a single agent and in combination with PD1 blockade in patients with solid tumors.

Abstract

TPS2671 Background: RP1 is an attenuated oncolytic HSV-1 that expresses a fusogenic glycoprotein from gibbon ape leukemia virus (GALV-GP R-) and GM-CSF. RP1 induces potent GALV-GP R- enhanced immunogenic cell death and host anti-tumor immunity in murine tumor models and increases PD-L1 expression. This clinical trial (NCT03767348) was designed to test the hypotheses that RP1 is safe when given alone and together with nivolumab (phase 1) and has efficacy together with nivolumab in four tumor types (phase 2). Methods: The primary goals of this clinical trial in a total of ~150 patients are to define the safety profile of RP1 alone and together with nivolumab, determine the recommended phase 2 dose (phase 1), and then in four phase 2 cohorts, to determine objective response rate in patients with melanoma, non-melanoma skin cancer, urothelial carcinoma and MSI-H solid tumors. Secondary objectives include duration of response, CR rate, PFS, viral shedding, and immune biomarker analysis. Patients with advanced cancer who failed prior therapy were eligible for the phase I component. In Phase 2 patients with histologic diagnoses of the four tumor types (N=30 for each) and who meet safety criteria for nivolumab treatment are eligible. Prior treatment with checkpoint blockade is not allowed except for the melanoma cohort. In the phase 1 portion patients are treated by intra-patient dose escalation of virus (range, 104 - 108 PFU) by intratumoral injection every two weeks for 5 total doses followed by 12 patients dosed 8 times at the RP2D in combination with nivolumab. Phase 1 patients were divided into two groups based on presence of clinically accessible lesions amenable to direct injection or those with visceral/deep lesions requiring image guidance for injection. In the phase 2 portion patients will receive the RP2D for eight injections and nivolumab will be given starting with the second RP1 injection. For the phase 1 portion, a modified 3+3 dose escalation design is used to assess safety and in the phase 2 portion, statistical analysis will be performed using a two-stage three-outcome optimum design with objective responses determined by RECIST criteria. As of February 11, 2019, 27 patients have been enrolled. Clinical trial information: NCT03767348.