Abstract CT155: Phase 2 study of sacituzumab govitecan (IMMU-132), an anti-Trop-2/SN-38 antibody-drug conjugate (ADC), in patients with pretreated metastatic small-cell lung cancer (mSCLC)

Introduction: Sacituzumab govitecan (IMMU-132) is an antibody-drug conjugate (ADC) delivering SN-38, a topoisomerase-1 inhibitor, to mSCLC cells expressing Trop-2. We are studying the safety/tolerability and efficacy of IMMU-132 in patients with relapsed/refractory mSCLC who had received a platinum-containing first-line regimen. Experimental Procedure: Patients received 8 or 10 mg/kg IV IMMU-132 on days 1 and 8 of repeated 21-day cycles. Objective tumor response (ORR) was determined by RECISTv1.1 in patients receiving at least one treatment cycle, and progression-free survival (PFS) and overall survival (OS) in all patients by Kaplan-Meier methods. (ClinicalTrials.gov, NCT01631552) Summary of New Unpublished Data: A total of 53 patients (23/30 M/F, median 63 years old) with 1-7 (median 2) prior lines of therapy were enrolled between November, 2013 and June, 2016. Immunohistochemistry of evaluable archival tumor specimens for Trop-2 expression (N=26) showed 92% positivity (61% moderately to strongly positive). They received up to 32 treatment cycles (median 5); the most frequent Grade >3 adverse events were neutropenia (34%), fatigue (13%) and diarrhea (9%). Four patients did not complete one cycle of treatment. In the other 49 patients (14 at 8 mg/kg, 35 at 10 mg/kg), there were 7 confirmed PRs and 21 SDs as best response. The resulting ORR rate was 14% (7/49), with a median duration and time-to-progression of a response of 4.0 and 7.6 mos, respectively, and the clinical benefit rate (PR+SD >4 mos) was 35% (17/49). The ORR rate was similar in pts who were sensitive (>3 mos response) or resistant (