A Randomized Phase II Study of Carboplatin and Pemetrexed with or without Selpercatinib (LY3527723) in Participants with Non-Squamous RET Fusion-Positive Stage IV Non-Small Cell Lung Cancer and Progression of Disease on Prior RET Directed Therapy (Lung-MAP Sub-Study)

Disease Related Criteria

a. Participants must have been assigned to S1900F based on biomarker analysis of tissue and/or blood and determined to have RET fusion-positive NSCLC.

b. Participants must be negative for all additional validated oncogenic drivers that could cause resistance to selpercatinib treatment.

c. Participants must have measurable disease documented by CT or MRI.

d. Participants must have a CT or MRI scan of the brain to evaluate for CNS disease within 42 days prior to sub-study randomization.

e. Participants must not have leptomeningeal disease, spinal cord compression or brain metastases unless: (1) metastases have been locally treated and have remained clinically controlled and asymptomatic for at least 14 days following treatment, and prior to sub-study randomization, AND (2) participant has no residual neurological dysfunction and has been off corticosteroids for at least 24 hours prior to sub-study randomization.

Prior/Concurrent Therapy Criteria

a. Participants must have received and developed disease progression during or after an anti-RET inhibitors treatment. The anti-RET inhibitor therapy must be the most recent therapy.

b. Participants must have progressed (in the opinion of the treating physician) following the most recent line of therapy.

c. Participants must have recovered (≤ Grade 1) from any side effects of prior therapy. Participants must not have received any radiation therapy within 14 days prior to sub-study randomization.

d. For participants with Stage IV or recurrent disease, the participant must not have received a platinum-based chemotherapy regimen.

e. Participants must not have received any prior systemic therapy (systemic chemotherapy, TKI, immunotherapy or investigational drug) within 14 days prior to sub-study randomization.

f. Participants must not be planning to receive any concurrent chemotherapy, immunotherapy, biologic or hormonal therapy for cancer treatment while receiving treatment on this study.

g. Participants must not have a prior or concurrent malignancy whose natural history or treatment (in the opinion of the treating physician) has the potential to interfere with the safety or efficacy assessment of the investigational regimen.

h. Participants must not have had a major surgery within 14 days prior to sub-study randomization.