START: A phase III study of L-BLP25 cancer immunotherapy for unresectable stage III non-small cell lung cancer.

7500 Background: L-BLP25 is a MUC1 antigen specific cancer immunotherapy. We report results from the phase III START study of L-BLP25 in patients (pts) not progressing after primary chemoradiotherapy (CRT) for stage III NSCLC. Methods: From Jan 2007 to Nov 2011, 1513 pts with unresectable stage III NSCLC that did not progress after CRT (platinum based chemo and ≥50 Gy) were randomized (2:1; double-blind) to L-BLP25 (806 µg lipopeptide) or placebo (PBO) SC weekly x 8 then Q6 weeks until disease progression or withdrawal. Cyclophosphamide 300 mg/m 2 x 1 or saline was given 3 days prior to first L-BLP25/PBO dose. Primary endpoint was overall survival (OS). Results: The primary analysis population (n=1239) was defined prospectively to try to account for a clinical hold by excluding pts randomized 6 months (m) before the hold. Arms were balanced for baseline characteristics. Median age was 61 y; 38.2% had stage IIIA and 61.3% IIIB; 65% had concurrent and 35% sequential CRT. Median OS was 25.6 m with L-BLP25 vs. 22.3 m with PBO (adjusted HR 0.88, 95% CI 0.75-1.03, p=0.123). Secondary endpoints time-to-progression and time-to-symptom-progression support consistency of results: HR 0.87 (95% CI 0.75-1.00, p=0.053) and 0.85 (95% CI 0.73-0.98, p=0.023). In predefined subgroup analyses, pts with concurrent CRT (n=806) had median OS of 30.8 m (L-BLP25) vs. 20.6 m (PBO; HR 0.78, 95% CI 0.64-0.95, p=0.016), while median OS with sequential CRT was 19.4 m (L-BLP25) vs. 24.6 m (PBO; HR 1.12, 95% CI 0.87-1.44, p=0.38; interaction p=0.032, Cox PH model). Sensitivity analyses revealed that there was no OS benefit in pts randomized 6 m before the hold (HR 1.09, CI 0.75-1.56, p=0.663). LEBLP25 was well tolerated with no safety concerns identified and no emergent evidence of immune related adverse events. Conclusions: L-BLP25 maintenance therapy in stage III NSCLC was well tolerated, but did not significantly prolong OS. Sensitivity analyses showed a smaller treatment effect due to the clinical hold, suggesting that longer uninterrupted treatment with L-BLP25 is required. Clinically meaningful prolongation of OS was observed in the predefined subgroup of pts with primary concurrent CRT. Clinical trial information: NCT00409188.