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
You may not be if
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.
