INTRODUCTION: Delta-like protein 3 (DLL3), an atypical Notch ligand, is expressed in small cell lung cancer (SCLC) tumors but is not detectable in normal adult tissues. Rovalpituzumab tesirine (Rova-T) is an antibody-drug conjugate containing a DLL3-targeting antibody tethered to a cytotoxic agent pyrrolobenzodiazepine via a protease-cleavable linker. Efficacy and safety of Rova-T compared with topotecan as second-line therapy in patients with SCLC expressing high levels of DLL3 (DLL3-high) was evaluated.

METHODS: TAHOE was an open-label, 2:1 randomized, phase 3 study comparing Rova-T with topotecan as second-line therapy in DLL3-high advanced or metastatic SCLC. Rova-T (0.3 mg/kg) was administered intravenously on Day 1 of a 42-day cycle for 2 cycles, with 2 additional cycles available to patients who met protocol-defined criteria for continued dosing. Topotecan (1.5 mg/m2) was administered intravenously on Days 1-5 of a 21-day cycle. The primary endpoint was overall survival (OS).

RESULTS: Patients randomized to Rova-T (n=296) and topotecan (n=148) were included in efficacy analyses. The median age was 64 years, and 77% had extensive disease at initial diagnosis. Median OS (95% CI) was 6.3 months (5.6-7.3) in the Rova-T arm and 8.6 months (7.7, 10.1) in the topotecan arm (hazard ratio, 1.46 [95% CI: 1.17-1.82]). An independent data monitoring committee recommended that enrollment be discontinued due to shorter OS observed with Rova-T compared with topotecan. Safety profiles for both drugs were consistent with previous reports.

CONCLUSIONS: Compared with topotecan, which is the current standard second-line chemotherapy, Rova-T showed an inferior OS and higher rates of serosal effusions, photosensitivity reaction, and peripheral edema in patients with SCLC. Significant unmet therapeutic need remains in this population.