Phase 2 dose multi-center, open-label study of ARQ 501, a checkpoint activator, in adult patients with persistent, recurrent or metastatic leiomyosarcoma (LMS)

Abstract

20521 Background: ARQ 501 selectively induces apoptosis in cancer cells by inducing a rapid and sustained increase of the pro- apoptotic protein E2F-1. ARQ 501 has been studied in three phase 1 studies, demonstrating acceptable toxicity and encouraging signs of efficacy. A 54 y/o female with metastatic LMS who failed 7 previous therapies achieved a prolonged PR on ARQ 501 monotherapy. This was consistent with preclinical data, where induction of E2F-1 and corresponding efficacy in human leiomyosarcoma xenografts was observed. Methods: A phase 2 study in adult LMS patients (>3 prior systemic therapies) was initiated to assess ORR, TTP and further characterize the safety of ARQ 501. ORR included CR, PR and SD=4 mo. Four week cycles (ARQ 501 450mg/m2) were repeated until progression, unacceptable toxicity, or another discontinuation criterion. Results: 49 patients were enrolled and 45 received ARQ 501. Data is available for 43 patients (4M/39F, median age, 54). Of the 43, 10 did not reach a protocol defined tumor assessment (4 deaths, 5 PD and 1 lost to follow-up prior to week 8), 19 have been assessed for response per RECIST at eight weeks (7 SD of 8–28+ weeks, 1 PR, 11 PD) and 14 active patients yet to reach first tumor assessment. The most common AEs were: anemia (68%, 21%=G3), hyperbilirubinemia (35%, 6%=G3), fatigue (35%, 0%=G3), nausea (30%, 0%=G3), constipation (24%), hemolysis (21%, 6%=G3), dyspnea (21%), and vomiting (21%). One treatment related death was reported in a 47 y/o Asian male with severe hemolysis following a single infusion of ARQ 501 at 450 mg/m2. The pt was hospitalized, but severe hemolysis led to acute renal failure and the patient expired after 4 days. Conclusions: ARQ 501 was administered to 45 patients with advanced, recurrent or persistent leiomyosarcoma. Several patients have achieved some clinical benefit (1 PR, 3 prolonged SD), further analysis of efficacy data is warranted prior to additional clinical investigation. No significant financial relationships to disclose.