HIV-positive Kaposi sarcoma and immune checkpoint blockade.

63 Title: HIV-Positive Kaposi Sarcoma and Immune Checkpoint Blockade Background: Kaposi sarcoma (KS) is an incurable, virally mediated malignancy arising in HIV-positive patients. We report the first observations on the safety and efficacy of checkpoint blockade in these patients. Methods: We identified eight evaluable patients with HIV-related Kaposi sarcoma who received ≥1 dose of checkpoint blockade. Data on demographics, treatment efficacy, and the effects on immune function (HIV and HHV8 viral load, CD4 count) and toxicity were curated. Results: Median age was 45.5 years (range, 38-63); all men; median, one prior regimen; all were treated with nivolumab 3mg/kg IV days 1 and 14 of each 28-day cycle. PD-L1 expression was assessed retrospectively and was low in 3 out of 4 patients with available data. All patients were receiving anti-retroviral therapy. The majority (75%) had preserved CD4 count and undetectable HIV viral load (Table). The response rate (RR) was 62.5% (5 of 8 patients) with 1 complete remission and 4 partial remissions; the remaining 3 patients have stable disease. Median follow up to date is 3.5 months and no patients has discontinued therapy. No grade >2 toxicities were noted. Most common side effects included fatigue, gastrointestinal discomfort, pruritis, and onycholysis. There was an overall increase in CD4 counts. Conclusions: Preliminary observations suggest that checkpoint blockade with nivolumab has low toxicity and high anti-tumor activity in KS. Additionally, patients experienced improvement in CD4 count. [Table: see text]