Randomized phase II trial of durvalumab (anti-PDL1) and tremelimumab (anti-CTLA4) administered in combination versus sequentially for the treatment of recurrent platinum-resistant non-clear cell ovarian cancer (NCT03026062)

Abstract

<h3>Objectives:</h3> Single agent immune checkpoint blockade (ICB) has demonstrated response rates of 5-15% in patients with recurrent high-grade ovarian cancer (HGOC), with another 15-40% of patients achieving stable disease. Combination ICB using ipilimumab and nivolumab resulted in improved response rates in a mixed population with platinum resistant and sensitive disease. The objective of the current trial was to evaluate sequential versus combination CTLA4 and PDL1 blockade strategies for extending progression free survival (PFS) in patients with platinum resistant/refractory HGOC. <h3>Methods:</h3> Patients were required to have pathologically confirmed platinum resistant or refractory epithelial ovarian cancer, no prior immunotherapy, and PS=0-1 for enrollment. The current abstract includes data only on subjects with high grade serous ovarian cancer (HGSOC), as enrollment of patients with clear cell histology is still ongoing. The primary endpoint was PFS and response was assessed using modified RECIST v1.1. Unlimited numbers of prior regimens were allowed. Patients were adaptively randomized to sequential arm: tremelimumab (3mg/kg q4 weeks x 4 doses) followed by durvalumab (1.5g IV q4 weeks for up to 9 doses) upon progression, or the combination arm: tremelimumab (1mg/kg IV plus durvalumab 1.5g IV q4wk for up to 4 doses followed by durvalumab monotherapy for up to 9 doses). For the Bayesian adaptive randomization, the probability of being assigned to an arm was proportional to the likelihood the arm had better PFS, such that patients were more likely to be randomized to the more effective arm. <h3>Results:</h3> A total of 61 subjects were adaptively randomized to sequential treatment (n=38) or combination therapy (n=23). 46 (79%) patients had wild-type breast cancer gene (<i>BRCA</i>). Median prior lines of therapy was 4 (range: 1-10). There was no difference in median PFS in the sequential arm (1.84 months; 95% CI: 1.77 – 2.17)) compared with the combination arm (1.87 months; 95% CI: 1.77 – 2.43), p=0.402. Similarly, median OS in the sequential and combination arms were 10.61 months (5.95 – 15.34) and 7.26 (4.24 – 15.57), respectively (p=0.810). In the sequential arm no objective responses were observed, although 12 patients (31.6%) exhibited stable disease. In the combination arm, 2 patients had partial response (8.7%) while one additional patient (4.4%) had stable disease. The adverse event profile was consistent with that previously reported for immune checkpoint therapy. <h3>Conclusions:</h3> There was no difference in the median PFS between the combination and sequential durvalumab plus tremelimumab treatment strategy arms in a heavily pretreated population of patients with platinum resistant/refractory HGOC. Response rates were comparable to prior reports, though the combination regimen did not add significant benefit as has been previously described with combination of ipilimumab/nivolumab. Further exploration into subpopulations that may have increased benefit from ICB is warranted.