Testing the Combination of the Anti-cancer Drugs XL184 (Cabozantinib) and Nivolumab in Patients With Advanced Cancer and HIV

Inclusion Criteria: * Age \>= 18 years. Children are excluded from this study, but will be eligible for future pediatric trials * For the six-patient safety cohort, subjects must have histologically or cytologically confirmed advanced solid tumors that are metastatic or recurrent, and require palliative systemic treatment, for which there are either Food and Drug Administration (FDA) approved indications for XL184 (cabozantinib) or nivolumab or have at least phase 2 data clearly indicating activity (such as renal cell carcinoma \[RCC\], hepatocellular carcinoma \[HCC\], medullary thyroid carcinoma \[MTC\], melanoma, non-small cell lung cancer \[NSCLC\], head and neck cancer, urothelial carcinoma, small cell lung cancer \[SCLC\], radioiodine-refractory differentiated thyroid cancer, ovarian cancer, castration-resistant prostate carcinoma \[CRPC\], and triple-negative breast cancer \[TNBC\]). Subjects must have progressed, or are intolerant, or decline systemic therapy associated with clinically significant survival benefit if checkpoint blockade is not an approved or accepted treatment. The expansion cohort is limited to subjects with KS. Histologic, cytologic, and pathologic confirmation of KS is required * Any number of prior cancer therapies will be permitted, including treatment naive subjects. (Note: For KS, treatment naive asymptomatic subjects will be permitted. But treatment naive KS subjects with visceral symptomatic disease or complicated KS HHV 8 disease including …