Median age of all randomized patients (N=748) was 64 years; 78.00% had TNM stage IV disease. At futility analysis of the subset with DLL3-high tumors, the hazard ratio for OS was 1.07 (95% confidence interval: 0.84-1.36) favoring the placebo arm,with median OS of 8.50 and 9.80 months in the Rova-T and placebo arms,respectively; futility criteria were met. Rova-T significantly improved PFS versus placebo by investigator assessment (4.00 versus 1.40 mo,hazard ratio=0.48, p < 0.001).

The recommended phase II dose (RP2D) was 0.30 mg/kg every 6 weeks (q6w) for two cycles. At the RP2D, grade 3/4 adverse events included anemia (17.00%), thrombocytopenia (15.00%), and elevated aspartate aminotransferase (8.00%). Responses were confirmed in 15/145 patients (10.34%) treated at 0.30 mg/kg, including 9/69 patients (13.04%) with NEC/NET. Rova-T at 0.30 mg/kg q6w had manageable toxicity, with antitumor activity observed in patients with NEC/NET, melanoma, MTC, and glioblastoma.

In pooled patients with NEC/NET expressing a high level of DLL3 (50% DLL3-positive tumor cells), the ORR was 17.14% (6/35) and 34.29% (12/35) had a BOR (all PRs). In those with NEC/NET expressing a low level of DLL3 (1-49% DLL3-positive tumor cells), the ORR was 8.82% (3/34) and the BOR rate was 14.70% (5/34) (all PRs). The median PFS values for pooled patients with NEC/NET expressing high and low levels of DLL3 were 4.30 months (95% CI, 2.7-6.1) and 3.30 months (95% CI, 2.40-4.80), respectively. The median OS values for patients expressing high and low levels of DLL3 were 7.40 months (95% CI, 5.60-13.10) and 7.10 months (95% CI, 4.30-9.90), respectively.

Progressive small-cell lung cancer (SCLC) who had previously been treated with at least one prior line of platinum-containing chemotherapy were enrolled if they were naive to PD-1/PD-L1targeting agents, had ECOG performance status 0-1, measurable disease per RECIST v1.1 or disease evaluable by tumor antigen assessment, and adequate bone marrow, cardiac, hepatic, and renal functions.

All patients (N = 35) were included in response analyses. Five patients (14.29%) overall achieved a PR per investigator assessment,with no patients achieving a CR. One patient each had a PR in the 0.20 and 0.30 mg/kg Q3W dose groups, and 3 patients in the 0.40 mg/kg Q9W dose group, fourteen (40.00%) patients achieved stable disease as their best overall response,and 5 had no or an non-evaluable posttreatment scan.

Nineteen patients had tumor samples that were able to be assessed for DLL3 expression by immunohistochemistry. DLL3-positive expression by immunohistochemistry (DLL3 >0%) was confirmed in 17 patients; 5 were DLL3 high (75.00% DLL3 positive cells). Of DLL3-positive patients, 2 (11.80%) achieved a PR, including 1 patient in the 0.20 mg/kg Q3W cohort and 1 DLL3-high patient in the 0.40 mg/kg Q9W cohort.