Motexafin gadolinium for the treatment of metastatic renal cell carcinoma: Phase II study results

Background: Thioredoxin reductase (Trx) has been implicated in activation of hypoxia-inducible factor-1 alpha, which is overexpressed in > 85% of renal cell carcinomas (RCCs). We evaluated the safety and efficacy of motexafin gadolinium (MGd), a Trx inhibitor, as a single-agent therapy for metastatic RCC. Patients and Methods: Patients with metastatic RCC were infused daily with MGd 5 mg/kg on days 1-5 and days 15-19 of each 28-day cycle. Patients were evaluated for response on days 21-28 of every third cycle. Those with tumor response or stable disease (SD) continued treatment for <= 12 cycles. Twenty-five patients with confirmed metastatic RCC were enrolled. All were evaluable for toxicity, and 20 were evaluable for response. Results: While no clinical responses were observed, 8 patients had SD after 3 treatment cycles, as did 4 after 6 cycles. Median overall survival was 10.1 months, and median progression-free survival was 2.7 months. The most common treatment-related toxicities were grade 1/2 pain, nausea, skin discoloration, fatigue, blisters, and headache. The most common grade 3 toxicity was hypophosphatemia, observed in 5 patients. MGd was reasonably tolerated, and disease stabilization was observed in several patients with metastatic RCC. Conclusion: These results show promise for the use of MGd in combination with other molecularly targeted therapies in previously treated patients with metastatic RCC. However, further investigation of MGd alone for metastatic RCC is not recommended.