Inclusion Criteria:

- ≥ 18 years old

- Histologically confirmed renal cell carcinoma with clinically or pathologically
confirmed progression

- Ineligible for interleukin-2 (IL-2) treatment and/or have had 2 or fewer prior
treatments

- Measurable disease

- Hemoglobin ≥ 9 mg/dL

- ECOG performance status of 0, 1, or 2

- Willing and able to provide written informed consent

Exclusion Criteria:

- Inadequate bone marrow, renal and liver function by laboratory criteria

- Absolute neutrophil count < 1500/µL;

- Platelet count < 100,000/µL;

- AST or ALT > 2 x upper limit of normal (ULN);

- Alkaline phosphatase > 5 x ULN;

- Total bilirubin > 2 x ULN;

- Creatinine > 2.0 mg/dL.

- Evidence of central nervous system metastases within past year

- Uncontrolled hypertension

- Known history of porphyria, G6PD deficiency or HIV