DeLLphi-308: Subcutaneous Tarlatamab in Participants With Extensive Stage Small Cell Lung Cancer (DeLLphi-308)

* Participants ≥ 18 years of age (or ≥ legal adult age within country if it is older than 18 years) at time of signing informed consent.

* Participants with histologically or cytologically confirmed ES-SCLC that progressed or recurred following at least one line of platinum-based anti-cancer therapy for SCLC.

Note: Participants with prior treatment for LS-SCLC should have also received another regimen for their recurrent, ES-SCLC disease.

* Eastern Cooperative Oncology Group (ECOG) Performance Status (PS) of 0 or 1.

* Participants must have adequate organ function (cardiac, pulmonary, kidney, and liver).

* Participants must be able to have SC injections administered in the abdomen.

* Participants without measurable disease or tumor tissue (fresh biopsy or archival) available may be permitted after discussion with and approval by Amgen Medical Monitor.

* Participants that have received prior DLL3 targeted therapy.

* Participants with untreated or symptomatic brain metastases or those requiring therapy with steroids.

* Note: Participants with asymptomatic brain metastatic lesions are allowed following definitive treatment (Amgen Medical Monitor may approve untreated, asymptomatic brain metastasis if local therapy is not required per investigator judgment).

* Participants with leptomeningeal disease.

* Participants with baseline oxygen requirement.