Efficacy of alpha-1,3-galactosyltransferase-expressing allogeneic renal cell carcinoma immunotherapy in patients (pts) with refractory metastatic renal cell carcinoma (mRCC).

Abstract

590 Background: HyperAcute Renal (HAR) immunotherapy consists of two allogeneic renal cancer cell lines that have been genetically modified to express α(1,3)Gal, to which humans have an inherent pre-existing immunity. A previous report demonstrated that HAR is well tolerated in pts with mRCC (2017 GUASCO, abstract: 528). Herein, we report the efficacy of HAR immunotherapy in mRCC. Methods: Pts with refractory clear-cell mRCC were eligible for this phase 1 dose-escalation trial. Concomitant treatment (Rx) with other approved agents was permitted after initial 2 months (m) of HAR monotherapy. The trial followed a standard 3+3 design with cells injected intradermally weekly for 4 weeks then biweekly injections for 10 immunizations (150 x106cells then escalated to 300 x106cells). Co-primary objectives were safety and efficacy. Results: A total of 18 patients were enrolled (4 low dose, 14 high dose) between 06/2015 to 07/2016. Patients received a median of 1 systemic Rx prior to HAR immunotherapy, with 8 patients receiving 2 or more prior agents. IMDC risk categories at the time of initial metastatic disease were: favorable risk (33%), intermediate risk (66%), poor risk (0%). The ORR was 0% with a disease control rate of 50%. Median PFS for patients treated with HAR immunotherapy was 2.0 months (m) (range 1.7-30.3 m). For patients receiving the low dose HAR, median overall survival (OS) was 14.2 m (range 3.6-21.6 m), while median OS for high dose HAR was 25.3 m (5.8-29.3 m). At the time of data cutoff in 09/2018, 7 patients were still living. Detailed clinical data will be presented in the meeting. Conclusions: HAR immunotherapy in refractory mRCC was well tolerated and demonstrated potential efficacy for OS similar to currently approved salvage-line Rx. With a unique mechanism of action, HAR immunotherapy may be a candidate for inclusion in novel combinatorial regimens being developed in salvage therapy setting in pts with mRCC. Clinical trial information: NCT02035358.