The purpose of this study is to evaluate the efficacy and safety of ZL-1310 compared to Investigator's Choice Therapy in participants with relapsed Small Cell Lung Cancer.

Inclusion Criteria:

• Age >/= 18 years, or considered an adult by local regulations, at the time of consent
• Signed informed consent
• Histologically or cytologically confirmed SCLC. Received 1L platinum-based systemic therapy and had documented disease progression during or after the most recent systemic therapy. Or received 2L tarlatamab is allowed.
• Measurable disease according to RECIST v1.1 as assessed by the investigator.
• Participants with a history of treated and stable or untreated and asymptomatic CNS metastases based on criteria per protocol.
• Adequate organ and marrow function
• Eastern Cooperative Group (ECOG) performance status of 0 or 1
• Life expectancy of at least 3 months
• Participants must be willing to undergo a tumor biopsy or provide archived tumor tissue sample at Screening
• Participants must be willing and able to comply with protocol for the duration of the study

Exclusion Criteria:

• Received more than one line of systemic therapy for Extensive-Stage SCLC.
• Received any prior ADC with topoisomerase 1 inhibitor payload
• Participants with another known malignancy with exceptions defined in the protocol.
• History or suspected ILD/pneumonitis based on criteria per protocol
• Clinically severe pulmonary compromise resulting from intercurrent pulmonary illnesses.
• Receipt of anti-cancer treatment known to treat cancers within 3 weeks before the first dose of study treatment.
• Prior radiotherapy before study treatment based on criteria per protocol
• Unresolved toxicity of Grade >/= 2 from previous anti-cancer treatment, except for alopecia and skin pigmentation.
• Known infection or active infection defined in the protocol.
• Clinically significant active cardiovascular disease or history of arterial thromboembolic event within 6 months prior to the first dose of study treatment based on criteria per protocol.