Abstract
412 Background: VHL is inactivated in most clear cell RCC (ccRCC) tumors giving rise to the HIF hypoxia response program and tumor angiogenesis. Antiangiogenic therapies are active in ccRCC, but resistance develops in all pts. Dual inhibition strategies may be needed to overcome resistance. CRLX101, a novel nano pharmaceutical formulation of camptothecin, has been shown in pre-clinical models to target HIF. We combined CRLX101 with bev in the treatment of pts with refractory mRCC in order to determine the safety and the recommended phase 2 dose (RP2D) of the combination, and to determine the therapeutic activity of treatment. Methods: Pts with mRCC refractory to conventional antiangiogenic therapies (all subtypes) were treated every 2 weeks with bev 10 mg/kg and escalating doses of CRLX101 (12 mg/m2, 15 mg/m2) in a standard 3+3 design with an expansion at the RP2D. Pts were treated until progression, death, or prohibitive toxicity. Adverse events were classified using CTCAE v 4.0. Radiographic results were assessed by RECIST v1.1. Results: 10 pts were enrolled on study – 6 clear cell, 2 papillary, 2 chromophobe. Median prior number of therapies was 2. No dose limiting toxicities were observed. CRLX101 at its single-agent RP2D (15 mg/m2) was safely combined with standard bev. 2 episodes of grade 3 non-infectious cystitis and 1 episode of grade 3 hypertension were observed. All other toxicities were grade 1 or 2. The median progression free survival (PFS) was 7.6 months which exceeded our pre-specified threshold of 16 weeks and has triggered 2nd stage accrual. 3 of 9 evaluable pts (33%) achieved a confirmed partial response (PR) including 1 patient with papillary mRCC; 4 pts (44%) displayed stable disease, and 2 had progressive disease as their best overall response. Conclusions: Our results demonstrate that CRLX101 can be safely combined with bev in pts with refractory mRCC. The RP2D is 15 mg/m2 q2w of CRLX101 with standard bev. Preliminary outcomes to date suggest that clinical benefit, manifest as prolonged PFS, is conferred to pts with all histologic subtypes of mRCC. Clinical trial information: NCT01625936.
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