Nirogacestat in Patients With Kaposi Sarcoma

Inclusion Criteria: * Biopsy-proven KS involving skin with or without visceral involvement either newly diagnosed or refractory to or intolerant of one or more prior therapies. * Patients must have cutaneous lesion(s) amenable to six total biopsies (minimum size of biopsy to be 4 mm), either six lesions \> 4 mm or one large lesion measuring 20 mm that can undergo serial biopsy, and at least five additional lesions measurable for assessment with no improvement over the past month. * Hemoglobin ≥ 8 g/dL (within three months prior to study entry) * Absolute neutrophil count (ANC) ≥ 1,000 cells/mm\^3 (within three months prior to study entry) * Platelet count ≥ 100,000/mm\^3 (within three months prior to study entry) * Calculated (method of Cockcroft-Gault) creatinine clearance (CrCl) ≥ 60 mL/min (within three months prior to study entry) (CrCl may also be obtained by the 24-hour collection method at the investigator's discretion) * Total bilirubin should be ≤ 1.5x upper limit of normal (ULN) (within three months prior to study entry). If, however, the elevated bilirubin is felt to be secondary to atazanavir therapy, patients will be allowed to enroll on protocol if the total bilirubin is ≤ 3.5 mg/dL provided that the direct bilirubin is normal * Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase \[SGOT\]) and alanine aminotransferase (ALT) (serum glutamic pyruvate transaminase \[SGPT\]) ≤ 3x ULN (within three months prior to study entry) * Life expectancy…