Phase Ib study of pembrolizumab in combination with bevacizumab for the treatment of metastatic renal cell carcinoma: Big Ten Cancer Research Consortium BTCRC-GU14-003.

Abstract

559 Background: Renal cell carcinoma (RCC) tumor vasculature is abnormal and does not provide nutritive blood flow, which results in regions of hypoxia. This hypoxia contributes to the immune tolerance of tumor cells by impeding the homing of cytotoxic T cells into tumor parenchyma. In addition, tumor angiogenesis enhances activity of myeloid-derived suppressor cells (MDSC) and tumor-associated macrophages (TAM) that suppress innate anti-cancer immunity. It has been demonstrated in preclinical models that antiangiogenic therapy decreased the number of MDSCs and changed polarization of TAMs from an immunosuppressive (M2-like) to an immunostimulatory (M1-like) phenotype. We hypothesized that therapy with bevacizumab will normalize the tumor vasculature, promote M1-like phenotype of TAMs, and thus potentiate the immunotherapeutic activity of pembrolizumab. As a prerequisite to testing this hypothesis, the objective of this study was to establish the safe dose of bevacizumab when used in combination with pembrolizumab. Methods: Our subject population included males and females (age > 18 y) with metastatic clear cell RCC after failure of at least one systemic therapy. In this Phase Ib dose escalation study, pembrolizumab (200 mg fixed dose every 3 weeks) was given in combination with bevacizumab (either at 10 mg/kg or 15 mg/kg every 3 weeks). The primary endpoint was to establish the maximum safe dose. Results: 12 subjects have been enrolled: 10 males (ages 33-68 y, mean: 52.7, median: 54.5) and 2 females (ages 61 and 62 y). To date 3 patients have received 1 cycle; 2 patients have received 2, 3, and 4 cycles each; and there are single patients who have received 5, 6, and 7 cycles each. No dose-limiting toxicity or serious adverse events related to the study drug have been reported. There were no grade 3 or 4 drug-related toxicities noted, and the most common grade 1 and 2 toxicities were diarrhea, fatigue, fever, hypertension, nausea, rash, and rigors. Conclusions: The 200 mg fixed dose of pembrolizumab and 15 mg/kg dose of bevacizumab, both given every 3 weeks, was determined to be safe and recommended for a multicenter Phase 2 study that is ongoing. Clinical trial information: NCT02348008.