A phase II trial assessing pazopanib (paz) as third-line therapy for metastatic renal cell carcinoma (mRCC): Clinical outcome and temporal analysis of molecular profile.

Abstract

4571 Background: Paz, an oral vascular endothelial growth factor (VEGF) receptor inhibitor, was assessed in a phase III study conducted in patients (pts) with mRCC who were cytokine-refractory or treatment-naïve (Sternberg et al J Clin Oncol 2010). Clinical outcomes with paz have been associated with a molecular profile (Tran et al Lancet Oncol 2012). The activity of paz in the 3rd-line setting and temporal changes in molecular profile during paz therapy are poorly understood. Methods: Eligibility was limited to pts with 2 prior lines of therapy (including at least 1 VEGF-directed therapy), ECOG PS 0-2, and clear cell histology. Pts received paz 800 mg/daily on a 28d cycle, and were assessed for response by RECIST 1.1 every 2 cycles. A Simon MinMax 2-stage design was employed, with 80% power of declaring an encouraging overall response rate (ORR) of 23% (type I error=10%). Molecular profiles were assessed on a Luminex platform using the Human Cytokine 30-plex Cytokine Immunoassay (Invitrogen) at baseline, 6 mos and 12 mos. Results: 28 pts (20M, 8F) were enrolled, with a median age of 63 (range, 45-86). All patients received at least 2 lines of prior therapy, and 6 pts (21%) had received 2 prior lines of VEGF-directed therapy. In the pre-specified intent-to-treat analysis, 12/28 pts (43%) had a confirmed response (1 CR, 11 PR), with 1 additional unconfirmed PR. 8 pts (29%) had SD as a best response. Median PFS for the cohort was 17.4 mos (95% CI 14.7-NR). No grade 4 treatment-related toxicities were observed. The most common grade 3 toxicities were hypertension (46%) and proteinuria (14%). At baseline, IL-6 was marginally lower in patients who achieved PR/CR (responders) as compared to those who did not (non-responders; P=0.06). Amongst patients still on therapy at 6 months and 12 months, responders had lower levels of HGF, IL-2R, IL-6, IL-8, and VEGF (P<0.05 for each) at both time intervals. Conclusions: Paz demonstrated an ORR of 43%, representing the highest ORR observed to date in a 3rd-line trial in mRCC. At 6 and 12 months, differences in molecular profile emerged between responders and non-responders, potentially underscoring mechanisms of drug resistance. Clinical trial information: NCT01157091.