Khan, Waseem Asrar

8106 Background: Bcl-2 family proteins are expressed in SCLC and are associated with chemotherapy resistance. AT-101 is an oral, pan Bcl-2 family protein inhibitor (Bcl-2, Bcl-XL, Mcl-1, and Bcl-w) and potent inducer of proapoptotic proteins. AT-101 has demonstrated activity in SCLC models, including those that express Mcl-1 and are resistant to other Bcl-2 inhibitors. The P1 portion of the study was previously reported. Methods: Pts ≥18 years of age, PS 0–1, with relapsed or refractory SCLC after first line chemotherapy with measurable disease per RECIST were eligible. Pts were stratified into 2 cohorts; cohort A ≥ 60 days and cohort B < 60 days relapse from prior chemotherapy and treated with T 1.25 mg/m2 daily and AT-101 40 mgs daily on days 1–5, q21 along with the use of myeloid growth factors. Adverse Events (AEs) were graded by the NCI CTCAE v. 3.0. Efficacy assessments (RECIST) were performed every 6-weeks. A 2-stage design was used with power/alpha of 80%/0.05 to detect a RR of > 25% and > 5%, in cohort A and B respectively. Results: 36 pts enrolled: ages 41–76; cohort A/B 23/13. The PR/SD/PD/NE rates were 17%/70%/9%/4% and 8%/54%/23%/15%, in cohorts A/B respectively. The median times to progression (TTP) were 18 and 13 weeks, respectively. The most common (>20 %) AEs (all grades): anemia (64%); neutropenia (53%); nausea (47%); fatigue (44%); thrombocytopenia (42%); dyspnoea (25%); and vomiting (22%). Most common Grade 3/4 related events (>5%): neutropenia (31%); thrombocytopenia (25%); anemia (14%); and asthenia (6%). No ileus was reported. Conclusions: AT-101 can be safely combined with T. The observed toxicities were consistent with the known rates of G4 cytopenias of T alone. The response rates observed did not meet the criteria for additional enrolment; however, many patients had a best response of SD and the median TTP in both cohorts was favorable compared to historical controls. Additional trials of AT-101 in SCLC are ongoing. [Table: see text]