Study of 225Ac-ABD147 to Establish Optimal Dose in Patients With SCLC and LCNEC of the Lung That Previously Received Platinum-based Chemotherapy

The study has 2 parts, Phase 1a and Phase 1b. The goal of Phase 1a is to gather safety, PK and initial efficacy data for 225Ac-ABD147 to better understand best doses for patients with small cell lung cancer (SCLC) and large cell neuroendocrine carcinoma (LCNEC) of the lung following platinum-based chemotherapy. An initial group of patients will also be given an experimental imaging agent called 111In-ABD147 to help understand where ABD147 goes in the body. The goal of Phase 1b is to gather additional safety and efficacy data on 225Ac-ABD147 to determine the best dose and to understand how those doses affect the same types of patients' cancers explored enrolled in Phase 1a.