A phase II trial of low-dose interleukin-2 (IL-2) and bevacizumab in patients with metastatic renal cell carcinoma (mRCC)

Abstract

5103 Background: Interleukin-2 and bevacizumab, a VEGF ligand-binding antibody, have each demonstrated antitumor activity in mRCC. Increased VEGF levels can lead to immunosuppression and resistance to immunotherapy through inhibition of dendritic cell (DC) differentiation and increase in immunosuppressive regulatory T cells (Tregs). To further evaluate the clinical and immunomodulatory effect of low-dose IL-2 and bevacizumab in mRCC, a phase II trial was conducted. Methods: Previously untreated good and intermediate risk mRCC pts received 8-week cycles of IL-2 (250,000 U/kg/d SC D1–5 during week 1 and 125,000 U/kg/d SC D1–5 during weeks 2–6, followed by a 2 week break). Bevacizumab 10mg/kg was administered IV every 2 weeks starting on day -14. Eligibility included RECIST-defined measurable disease, clear cell histology, normal organ function, and prior nephrectomy. A Simon 2 stage phase II design was employed to test the hypothesis of a 40% improvement in the 3-month PFS vs. historical IL-2-treated controls. Overall response rate (ORR) and toxicity were recorded. Exploratory endpoints included activation of circulating DC’s, Tregs and VEGF levels. Results: To date 16 of a planned 35 pts are enrolled. Median age is 59 years (range, 44–67); Eight patients have >1 site of metastasis; median treatment duration is 8 weeks (8–32+). Among 11 pts evaluable for response, 1 PR and 3 SD lasting >3 months have been observed. All pts with SD have demonstrated some degree of tumor shrinkage. Seven pts have discontinued therapy (5 PD, 2 withdrew consent). Most common treatment-related toxicity included fatigue, nausea, diarrhea, and fever. When comparing immune correlates at day 56 of therapy vs. baseline, all pts had an increase in the number of Tregs (median increase 1.65, range; 0.76–10.4; p= 0.008). Similarly, all pts had a decline in VEGF levels (median decline 164.38 pg/ml, range; 2.20–393.04 pg/ml; p= 0.008). No differences in DC activation have been observed. Conclusions: The combination of LD IL-2 and bevacizumab produces antitumor activity and moderate toxicity. Preliminary correlative data demonstrates inhibition of VEGF and increase in Tregs without effect on DC activation. No significant financial relationships to disclose.