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 75 patients. The phase I will consist of 3 parts: Part A - an intra-patient dose escalation part, followed by a dose exposure (Part B), followed by a dose expansion (Part C).