Pembrolizumab Plus Lenvatinib in Previously Treated Classic Kaposi Sarcoma (PULSAR)

Inclusion Criteria: Have a histologically confirmed diagnosis of classic (or endemic) KS Progression or inadequate response to at least one prior systemic chemotherapy Presence of measurable disease by PET-CT scan and/or dermatological examination KS with at least 10 cutaneous and/or mucosal lesions, or involving more than one limb segment or with involvement >3% body surface KS with at least 4 lesions ≥ 5mm KS with at least 1 superficial lesion willing to provide tissue from cutaneous and/or mucosal biopsy at baseline At least 4 weeks washout for all KS specific therapies including chemotherapy (both systemic and intralesional) and radiotherapy Be ≥ 18 years of age at the time of signing informed consent Have an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 or 1 Have adequately controlled blood pressure (BP) with or without antihypertensive medications, defined as BP ≤150/90 mm Hg and no change in antihypertensive medications within 1 week prior to randomization. Exclusion Criteria: Has a known history of human immunodeficiency virus (HIV) infection (HIV 1/2 antibodies detected at screening). Has a known history of Hepatitis B (defined as Hepatitis B surface antigen [HBsAg] reactive) or known active Hepatitis C virus (defined as HCV RNA [qualitative] is detected) infection. Note: no testing for Hepatitis B and Hepatitis C is required unless mandated by local health authority. Has active autoimmune disease that has required systemic treatment in the past 2 years (i.e. with use of disease modifying agents, corticosteroids or immunosuppressive drugs). Replacement therapy (eg., thyroxine, insulin, or physiologic corticosteroid replacement therapy for adrenal or pituitary insufficiency, etc.) is not considered a form of systemic treatment. Patients with vitiligo, type I diabetes mellitus, hypothyroidism, psoriasis not requiring systemic treatment are permitted to enroll. Has received prior therapy with an anti-PD-1, anti-PD-L1, or anti-PD-L2 agent, or with an agent directed to another stimulatory or co-inhibitory T-cell receptor (eg, CTLA-4, OX 40, CD137). Has received prior radiotherapy within 2 weeks of start of study intervention. Participants must have recovered from all radiation-related toxicities, not require corticosteroids, and not have had radiation pneumonitis.