• Histologically confirmed extensive-stage Small Cell Lung Cancer (SCLC); must have failed prior front-line platinum-based therapy including immune therapy with relapse within 6 months followed by failed tarlatamab therapy, if available and appropriate, and no more than 3 total prior lines of systemic therapy (therapy terminated due to toxicity or drug shortage, in the absence of Response Evaluation Criteria In Solid Tumors (RECIST) v1.1 progression, will be considered part of the same line). Sponsor may opt to allow history of treatment free interval from front-line longer than 6 months .

• Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2.

• Patient must have progressed radiographically on or after their most recent line of anticancer therapy and have measurable disease as defined by RECIST v1.1 (radiologically measured by the Investigator).

• The interval from prior antitumor treatment should be at least 2 weeks or 5 half-lives, whichever longer.

• All acute toxic effects (excluding alopecia) of any prior therapy must have resolved to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) version 5.0 Grade ≤ 1 or to the baseline laboratory values as defined in the protocol.

• Patients must use highly effective contraception or true abstinence.

• Ability to swallow capsules intact (without chewing, crushing, or opening).