Phase 1b DSP-0390 EBP (cholesterol biosynthesis) inhibitor plus PD‑L1 mAb atezolizumab

This single-center Phase 1b pilot at Washington University in St. Louis tests whether adding DSP‑0390—an oral small-molecule inhibitor of emopamil-binding protein (EBP), a late-step sterol isomerase in de novo cholesterol biosynthesis—can safely deepen/extend benefit from maintenance immunotherapy with atezolizumab, Genentech/Roche’s PD‑L1–blocking monoclonal antibody. Patients have extensive-stage small cell lung cancer (ES‑SCLC) with no progression after induction platinum-etoposide chemoimmunotherapy that included an anti–PD‑L1 agent (atezolizumab or durvalumab). The study uses a safety lead-in with two DSP‑0390 dose levels (120 mg and 180 mg daily, 21‑day cycles) given with atezolizumab administered per usual local standard dosing, followed by treatment at the determined safe DSP‑0390 dose until progression/toxicity (up to 2 years). DSP‑0390 is owned/developed by Sumitomo Pharma (Sumitomo Pharma Oncology), and the commercial/scientific angle is “metabolic rewiring” (cholesterol dependence) as a way to potentially sensitize SCLC to checkpoint blockade in a maintenance setting. Today’s post-induction care for ES‑SCLC has commonly been ongoing PD‑L1 maintenance (atezolizumab or durvalumab), and as of October 2025 the maintenance landscape also includes lurbinectedin plus atezolizumab for eligible patients—so this trial explores a distinct, oral targeted-metabolism add-on rather than another cytotoxic.