Palbociclib and Pembrolizumab In Central Nervous System Metastases

This is a non-randomized, parallel cohort, Phase II study. Phase II clinical trials test the safety and effectiveness of an investigational intervention to learn whether the intervention works in treating a specific disease. "Investigational" means that the intervention is being studied. The study will be conducted in two independent cohorts. The first cohort (Cohort 1) is comprised of participants with measurable CNS metastases from solid tumors (including patients whose primary cancers are from lung, breast or melanoma) harboring specific alterations, and participants receive the study drug palbociclib. The second cohort (Cohort 2) will evaluate the efficacy and safety of the combination of pembrolizumab and palbociclib in recurrent brain metastases from breast cancer or melanoma. Palbociclib is being studied for use in the treatment of a broad range of cancers. This type of drug inhibits cell growth in the cells called cyclin-dependent kinases which promote tumor cell proliferation. The U.S. Food and Drug Administration (FDA) has not approved palbociclib for participants with central nervous system metastases, but it has been approved for other uses. Researchers hope to study the effects of pembrolizumab. The U.S. Food and Drug Administration (FDA) has approved pembrolizumab for some diseases, but not central nervous system metastases. Many cancers use specific pathways (such as PD-1/PD-L1 and CTLA-4) to evade the body's immune system. Pembrolizumab works by blocking the PD-1/PD-L1 pathways and thus releasing the brakes on the immune system so it can stop or slow cancer. In some tumor diagnoses, there may be a correlation between a specific marker (PD-L1 status) and activity of types of immunotherapies. Participants in any cohort will receive study treatment as long as they do not experience intolerable side effects and their disease does not worsen, and will be followed for 2 years after their study treatment ends.