The objective of this study is to evaluate the Safety, Tolerability, Pharmacokinetics, and Efficacy of BL-M14D1 in Subjects with locally Advanced or Metastatic Small Cell Lung Cancer and Other Neuroendocrine Tumors

To determine the safety profile, maximum tolerated dose (MTD), dose-limiting toxicities (DLTs), and recommended Phase 2 dose (RP2D) of FF-10850 (topotecan liposome injection) in patients with advanced solid tumors including Merkel Cell Carcinoma