Abstract 1364: Exposure-response (E-R) analysis of efficacy for avelumab in combination with axitinib in patients with advanced renal cell carcinoma (aRCC) in JAVELIN Renal 101

BACKGROUND: Avelumab, a monoclonal antibody targeting PD-L1, is currently approved in the USA in combination with axitinib for the first-line treatment of patients with aRCC. This analysis evaluated the relationship between potential covariates, including avelumab exposure, and the efficacy endpoints progression-free survival (PFS; by blinded independent central review per Response Evaluation Criteria in Solid Tumors [RECIST] criteria) and objective response (OR; per RECIST) in patients with aRCC. METHODS: Exposure metrics for all patients in JAVELIN Renal 101 who received avelumab 10 mg/kg every 2 weeks (Q2W) in combination with axitinib were derived from a population pharmacokinetic model (N=434). E-R analysis for PFS was conducted using parametric time-to-event (TTE) methodology. The hazard distribution was tested using exponential, Weibull, log-normal, and log-logistic distributions. E-R analysis for OR was performed using generalized binomial logistic regression. For OR, the full model included the influence of all potential covariates, while the final model retained statistically significant covariates after stepwise backwards elimination (α=0.15). For PFS, covariates were included in the full model based on forward addition (α=0.05), and the final model was determined using backward elimination (α=0.01). Model evaluation included TTE-visual predictive checks, the likelihood ratio test, the Hosmer-Lemeshow test, and receiver operating characteristic curves. RESULTS: The best fit to the PFS data was the log-normal distribution. Avelumab exposure (cycle 1 day 15 trough concentration) was associated with probability of longer PFS in both univariate and multivariate regression models. In addition, the favorable-risk group, according to baseline Heng criteria, was associated with probability of longer PFS relative to patients with intermediate prognosis using Heng criteria. Similarly, increasing avelumab exposure was associated with a higher probability of achieving OR. However, several factors have confounded the interpretation of the causal relationship between exposure and PFS or OR, including the imbalance of Heng prognostic criteria across exposure quartiles, correlation among covariates, and that data were from a single-dose regimen. No relationship was found between incidence of ADA or baseline PD-L1 status and the efficacy endpoints PFS or OR. CONCLUSION: The E-R analyses were considered exploratory and no definite conclusions could be made on the impact of exposure on PFS or OR, as other variables confounded interpretation of the relationship. Overall, the exposure from avelumab 10 mg/kg IV Q2W in combination with axitinib was associated with a manageable and tolerable safety profile and demonstrated superior efficacy compared with sunitinib in terms of PFS in treatment-naive patients with aRCC. Citation Format: Carlo Bello, Satjit Brar, Joanna C. Masters, Akash Khandelwal, Ana M. Novakovic, Ana Ruiz-Garcia, Jennifer Hibma. Exposure-response (E-R) analysis of efficacy for avelumab in combination with axitinib in patients with advanced renal cell carcinoma (aRCC) in JAVELIN Renal 101 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1364.