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