Trial of Ixazomib for Kaposi Sarcoma

Inclusion Criteria: * Ability to understand and the willingness to sign a written informed consent document * Participants must have histologically or cytologically confirmed cutaneous Kaposi sarcoma. Participants must have measurable disease with a minimum of five bi-dimensionally measurable KS cutaneous marker lesions. If fewer than five bi-dimensionally measurable marker lesions are available, the total surface area of the marker lesion(s) must be \>= 700 mm\^2 * Participants must have documentation of HIV status. If HIV negative, documentation of a negative HIV rapid test within 21 days before enrollment. If HIV positive, documentation of HIV-1 infection by means of any one of the following: * Documentation of HIV diagnosis in the medical record by a licensed health care provider * Documentation of receipt of antiretroviral therapy (ART) (at least two different medications that do not constitute a prescription for pre exposure prophylaxis \[PrEP\]) by a licensed health care provider. Documentation may be a record of an ART prescription in the participant's medical record, a written prescription in the name of the participant for ART, or pill bottles for ART with a label showing the participant's name * HIV-1 ribonucleic acid (RNA) detection by a licensed HIV-1 RNA assay demonstrating \> 1000 RNA copies/mL * Any licensed HIV screening antibody and/or HIV antibody/antigen combination assay confirmed by a second licensed HIV assay such as a HIV-1 Western blot confi…