This is an open, non-controlled, phase I/II study evaluating the safety, tolerability, and anti-tumor efficacy of orellanine treatment in patients with metastatic clear-cell or papillary renal carcinoma. The study will include up to 50 patients. The phase I will consist of 2 parts: an intra-patient dose escalation part, followed by a dose exposure part.. In phase II, up to 30 additional patients will be recruited and treated to better characterize drug safety, tolerability, and preliminary efficacy.