A Study to Test How Well ZL-1310 may Work Compared to Therapies Selected by the Investigator in Treating Patients with Relapsed Small Cell Lung Cancer

Prior treatment

• Received more than one line of systemic therapy, other than tarlatamab, for SCLC.
• Received any prior ADC with a topoisomerase I inhibitor payload.
• Clinically severe pulmonary compromise (including but not limited to baseline oxygen saturation of <90% on room air) resulting from intercurrent pulmonary illnesses including but not limited to any underlying pulmonary disorder and potential pulmonary involvement caused by any autoimmune, connective tissue, or inflammatory disorders. Participants who have prior pneumonectomy resulting in severe pulmonary compromise or who require continuous supplemental oxygen.
• Received radiotherapy within 2 weeks to non-thoracic area or within 4 weeks to the thoracic area prior to the first dose of study treatment or received >30 Gy of thoracic radiotherapy.

Other illness

• History of (non-infectious) ILD/pneumonitis that required corticosteroids, current ILD/pneumonitis of any grade, or suspected ILD/pneumonitis that cannot be ruled out by imaging at Screening.

• Histologically or cytologically confirmed SCLC. Mixed histology and/or transformed SCLC from non-small cell lung cancer are not allowed.
• Received 1L platinum-based systemic therapy and had documented disease progression during or after the most recent systemic therapy. Prior lines of systemic therapies are defined as follows: − Prior 1L therapy should be platinum-based chemotherapy in combination with an anti-PD-(L)1 agent. o Exception: combination with an anti-PD-(L)1 agent is not required in cases where the participant is considered to be ineligible to receive an anti-PD-(L)1 agent. o Maintenance therapy with an anti-PD-(L)1 agent and/or lurbinectedin and/or tarlatamab does not count as a separate line of therapy. o Platinum-based systemic therapy for limited-stage SCLC is considered 1L systemic therapy if disease progression occurs within 6 months of completion of platinum-based chemotherapy. − 2L systemic therapy is not allowed, except for tarlatamab.
• Measurable disease according to RECIST v1.1.
• Participants with a history of treated and stable CNS metastases are eligible.
• Participants with untreated and asymptomatic CNS metastases must not require steroids and/or anti-convulsants, nor local therapy as determined by the investigator per local guidelines.
• Eastern Cooperative Oncology Group performance status of 0 or 1.
• Life expectancy of at least 3 months.
• Adequate organ and marrow function.
• Must be willing to undergo a tumor biopsy or must provide archived tumor tissue sample at Screening.