Preliminary Assessment of Safety and Tolerability of Dostarlimab in Combination Antiretroviral Therapy (cART) Refractory HIV Associated Kaposi Sarcoma

This is a phase 1b, open label, single arm study evaluating the safety and tolerability of the drug dostarlimab in combination antiretroviral therapy (cART) refractory HIV-associated Kaposi Sarcoma (KS), a rare type of cancer usually seen in people with the HIV infection. Dostarlimab is a type of immunotherapy, and is a monoclonal antibody that has been designed to inhibit the receptor programmed death-1 (PD-1). One of the two ligands for PD-1 has been shown to be upregulated in KS patients, the PDL-1 ligand. By preventing PDL-1 form binding to PD-1, dostarlimab increases the body's immune response to attack more cancer cells. The safety profile of dostarlimab in this specific cancer has not been explored. The primary aim of this study is therefore to provide confirmatory evidence of safety of dostarlimab in KS patients and to preliminary evaluate its effects on HIV reservoirs and assess how it causes its anti-cancer effects through studying tumour tissue before and after treatment. This study will be conducted in two parts and will recruit a total of up to 20 patients. Upon completion of screening investigations inclusive of a fresh tumour biopsy within a 28-days window, patients will receive dostarlimab at the fixed dose of 500 mg dose every 3 weeks for the first 4 doses followed by a fixed 1000 mg dose every 6 weeks. Treatment will be continued until loss of clinical benefit, unacceptable toxicity, patients' withdrawal or completion of a total of 48 weeks of treatment. Part 1 will consist of 6 patients being dosed and observed for toxicity for 21 days following first dose. A trial steering committee will evaluate any treatment related adverse events (AEs) and dose-limiting toxicities (DLTs) reported before deciding on whether to continue onto part 2, where a further 14 patients may be enrolled.