A Phase I/Ii Trial Of Pazopanib Alternating With Bevacizumab In Treatment-Naive Metastatic Clear Cell Renal Cell Carcinoma (Ccrcc) Patients: Phase I Results.

561 Background: Pazopanib as single agent and bevacizumab plus interferon were approved for use in metastatic RCC (MRCC) based on their ability to modulate the vasculature and prolong progression free survival. VEGF levels rose unopposed while using VEGF tyrosine kinase inhibitors (TKI) without break. We hypothesized that adding a break as well as bevacizumab which removes VEGF could prolong PFS in MRCC pts. Methods: This phase I trial was conducted in VEGF treatment naïve MRCC pts. This trial utilized a unique regimen of alternating Pazopanib (day 1-28) with bevacizumab (on days 36 and 50) in a 10-week cycle. The study employed a classic 3+3 design for dose escalation (dose levels in table 1). Safety utilized CTCAE version 4.0 and response evaluation was done using RECIST 1.1 criteria. The primary endpoint of this phase I trial was to find the recommended phase 2 dose (RP2D) of this novel regimen. Key secondary endpoints included objective response rate (ORR), safety/ toxicity and pharmacokinetics. Phase I safety committee acknowledged the completion and approved reporting of Phase I portion of this study. Results: This phase I study was conducted at two academic centers. Twenty-five pts were enrolled in the phase I portion. Median age was 64 years and 68% were male patients. The Commonest adverse events (AE) included fatigue (64%), diarrhea (52%), hypertension (48%), nausea (36%), dysgeusia (36%), vomiting (24%) and proteinuria (28%). The commonest grade 3/4 AE of more than 5% frequency included hypertension (20%) and proteinuria (12%). The dose levels 1 and 4 were expanded due to one DLT each and RP2D was established at dose level 4. The ORR was 25% among evaluable pts who completed at least one cycle of therapy (n=20). The median PFS of the ITT cohort (n=25) was 20.9 months. Conclusions: These data demonstrate that this novel regimen could be safely tested in a phase II trial. The safety and efficacy data suggest that this novel regimen could be optimal for MRCC patients with favorable/intermediate risk. Clinical trial information: NCT01684397. [Table: see text]