A Study of hSTC810 in Combination With Paclitaxel in Relapsed or Refractory Extensive Stage Small Cell Lung Cancer

Inclusion Criteria: * Ability to understand and sign an informed consent form * Male or female ≥ 18 years of age * Histologically or cytologically confirmed SCLC * R/R ES-SCLC on or after platinum-based chemotherapy for SCLC with documented disease progression * At least 1 measurable lesion as defined by RECIST 1.1 * Eastern Cooperative Oncology Group Performance Score (ECOG PS) of 0 or 1 * Life expectancy of at least 3 months * Adequate organ function as described in the protocol * For female or male patients with reproductive potential: Agree to use contraception throughout the study and at least 5 months after the last dose. Exclusion Criteria: * Known active leptomeningeal disease (carcinomatous meningitis) * Known active and uncontrolled central nervous system (CNS) metastases * Treatment with immunotherapy, chemotherapy, targeted small molecule therapy, or any other investigational agent \< 14 days prior to initiation of study treatment * Treatment with radiation therapy \< 14 days prior to initiation of study treatment * Major surgery \< 21 days prior to initiation of study treatment * Received live vaccine \< 30 days prior to initiation of study treatment, including intranasal influenza vaccine * History of another primary malignancy with protocol-defined exceptions * Active or history of autoimmune disease requiring systemic treatment * Receiving high doses of steroids or other immunosuppressive medications * Active hepatitis B or C infection * Active or history of non-infectious pneumonitis requiring treatment with steroids * Active uncontrolled viral, fungal, or bacterial infection including tuberculosis * Pregnant or breastfeeding female patients * History of severe hypersensitivity reaction to a monoclonal antibody treatment * History of severe hypersensitivity reaction or ≥ Grade 3 adverse event (AE) to paclitaxel treatment * History of cerebral vascular event, unstable angina, myocardial infarction, or cardiac symptoms within 6 months prior to screening * QT Corrected for Fridericia's method (QTcF) \> 470 ms at screening * Lack of resolution of any toxicity to max Grade 1 (except alopecia) * Active or history of any condition, therapy, or lab abnormality that may interfere with the patient participation for the full duration of the study * Known psychiatric or substance use disorder * Positive Coronavirus disease 2019 (COVID-19) test at screening