In this issue of Cancer, Garcia et al report results from a phase 2 trial of ramucirumab in patients with metastatic renal cell carcinoma (mRCC).1 Ramucirumab, an immunoglobulin G1 (IgG1) monoclonal antibody with affinity for the extracellular domain of vascular endothelial growth factor receptor-2 (VEGFR2), was recently granted priority review by the US Food and Drug Administration on the basis of the phase 3 REGARD trial (ramucirumab monotherapy for previously treated advanced gastric or gastroesophageal junction adenocarcinoma). 2 In that study, patients with advanced gastric cancer who had failed prior platinum-based or fluoropyrimidine-based therapy and received ramucirumab with best supportive care (BSC) had a prolongation in both progression-free survival (PFS) and overall survival (OS) compared with patients who received ramucirumab alone. Even more recently, the phase 3 RAINBOW trial (ramucirumab plus paclitaxel vs placebo plus paclitaxel in the treatment of metastatic gastroesophageal junction and gastric adenocarcinoma after disease progression on first-line platinum-containing and fluoropyrimidine-containing combination therapy) suggested a benefit of OS with the combination of paclitaxel and ramucirumab (vs paclitaxel with placebo) in a similar setting.3 These data come on the heels of results from a separate, negative phase 3 trial of ramucirumab in metastatic breast cancer. 4 With the mixed pool of results amassed thus far, what will be the ultimate fate of ramucirumab in mRCC?The results reported by Garcia et al provide several key insights but may be insufficient to fully address this question. The trial evaluated 40 patients with mRCC who had received prior therapy with sorafenib and/or sunitinib. The study failed to meet its primary endpoint, reporting an objective response rate (ORR) of just 5.1%. The selection of ORR as a primary endpoint in phase 2 trials has been the subject of much debate, especially given that all phase 3 trials in mRCC to date that have led to drug approvals have used PFS. The PFS data from this phase 2 experience (7.1 months) is perhaps more encouraging than the observed ORR. Acknowledging the caveats of any cross-trial comparison, these data compare favorably to the PFS associated with everolimus in a phase 3 trial of daily oral everolimus for RCC (the RECORD-1 trial) (4.0 months) and with axitinib in a phase 3 trial of axitinib versus sorafenib in advanced RCC (the AXIS trial) (6.7 months). 5,6 Although the eligibility criteria of the current study closely mirror those in RECORD-1, it is worth noting that AXIS only permitted 1 prior line of therapy (either cytokine or targeted therapy)-in the subset of patients receiving axitinib after prior sunitinib, a more modest PFS of 4.8 months was observed. Of course, results from the phase 2 ramucirumab experience are tempered by the absence of an independent radiographic review, which would have a bearing on both ORR and PFS.Garcia et al posit several paths forward for ramucirumab, suggesting further development as a single ...