OA05.03 Single-Agent Rovalpituzumab Tesirine, a Delta-Like Protein 3 (DLL3)-Targeted Antibody-Drug Conjugate (ADC), in Small-Cell Lung Cancer (SCLC)

SCLC is one of the most deadly malignancies. Rovalpituzumab tesirine (SC16LD6.5, Rova-T) is a first-in-class ADC directed against DLL3, a novel target identified in tumor initiating cells and expressed in over 80% of SCLC cases. Seventy-four patients with progressive SCLC after at least one previous systemic therapy were enrolled in a first-in-human study (NCT01901653), irrespective of DLL3 expression, including 68 at active doses of 0.2-0.4 mg/kg administered intravenously every 3 or 6 weeks. Available archived tumor tissue (n=48) was assessed retrospectively by immunohistochemistry for DLL3. Among 60 evaluable subjects, active dose levels resulted in a confirmed objective response rate (ORR) of 18% and a confirmed clinical benefit rate (CBR; stable disease or better) of 68%. Among 26 evaluable subjects with DLL3 expression in at least 50% of tumor cells (DLL3-high), confirmed ORR and CBR were 39% and 89%, respectively. Median duration of response was 5.6 months. One-year survival rates among all and DLL3-high subjects were 18% and 32%, respectively. Among primary sensitive relapse patients, confirmed ORR and CBR among all subjects were 24% (8/33) and 67% (22/33); and among DLL3-high subjects were 53% (8/15) and 100% (15/15), with one-year survival rates of 17% and 33%, respectively. Among primary resistant/refractory relapse patients, confirmed ORR and CBR among all subjects were 12% (3/25) and 72% (18/25); and among DLL3-high subjects were 18% (2/11) and 73% (8/11), with one-year survival rates of 21% and 29%, respectively. The most common grade 3 or higher toxicities included thrombocytopenia (12%), serosal effusions (11%), and skin reactions (8%). ADC pharmacokinetics were linear with a terminal half-life of 10 - 14 days and anti-therapeutic antibodies did not develop. Rovalpituzumab tesirine demonstrates encouraging single-agent anti-tumor activity with a manageable safety profile, including among patients with disease resistant or refractory to primary chemotherapy. Further development of rovalpituzumab tesirine in SCLC is warranted.