Safety and Efficacy Study of AVB-S6-500 (Batiraxcept) in Patients With Advanced or Metastatic Clear Cell Renal Cell Carcinoma

Inclusion Criteria:

* Age 18 years or older
* Histologically confirmed advanced or metastatic clear cell Renal Cell Carcinoma confirmed by imaging. Phase 1b and Phase 2 Part A: has progressed on/after at least one front-line of treatment; Phase 2 Part B: No prior systemic treatment; Phase 2 Part C: not amenable to curative intent therapy.
* Must have radiologic imaging with a computed tomography (CT) scan or magnetic resonance imaging (MRI) within 28 days of enrollment
* Must have at least one measurable lesion according to RECIST 1.1
* ECOG performance status of 0-1
* Adequate bone marrow, liver and kidney function
* Life expectancy of \>12 weeks
* At least 28 days between termination of prior major surgery or anticancer therapy or 14 days from last radiation therapy and administration of AVB-S6-500

Exclusion Criteria:

* Received prior treatment with cabozantinib (Phase1b and Phase 2 Part A)
* Received prior treatment with nivolumab (Phase 2 Part B)
* Concurrent anti-cancer therapy or any other interventional treatment or other interventional research trial
* History of prior malignancy within the past 3 years except adequately treated basal or squamous cell skin cancer, superficial bladder cancer or carcinoma in situ of the prostate, cervix or breast
* Symptomatic CNS metastasis or metastases
* Active GI disease that would impact absorption of cabozantinib
* Nephrotic range proteinuria at screening
* Evidence of pleural effusion, ascites etc that requires therapeutic intervention within 28 days prior to AVB-S6-500 administration
* Phase 2 Part A and Part B: Has had a major bleed in the last 3 months, uncontrolled hypertension despite treatment with antihypertensives or is not appropriate for treatment with cabozantinib in the Investigator's opinion
* Serious active infection requiring IV antibiotics and/or hospitalization at study entry
* Phase 2 Part B: Has active, known or suspected autoimmune disease, defined as requiring systemic treatment
* Active COVID-19, HIV, Hepatitis B or Hepatitis C virus.