AB0457 Clinical equivalence in efficacy between abp 501 and adalimumab in patients with moderate to severe rheumatoid arthritis: a tipping point sensitivity analysis

Background ABP 501 is the first approved biosimilar to adalimumab. Patient withdrawals from clinical trials can result in missing data, which may lead to loss of statistical power and bias of the treatment difference estimate. Therefore, it is critical to examine the potential effects of missing data and analyse the sensitivity of the results under various assumptions on the mechanism of missing data. Objectives To examine and confirm the robustness of the clinical similarity conclusion between ABP 501 and adalimumab reference product (RP) through tipping point sensitivity analyses on ACR20 at week 24, the primary endpoint of the phase 3 study in patients with rheumatic arthritis. Methods The primary analysis for this trial has been previously published. The proportions of patients achieving ACR20/50/70 responses with last observation carried forward imputation at weeks 2, 4, 8, 12, 18 and 24, were similar between ABP 501 and the RP over time. Tipping point sensitivity analyses were used to estimate the difference between ABP 501 and the RP with varying assumptions on the outcomes in patients who withdrew from the study early and those who completed the study. Results The table 1 displays the results of tipping point analyses on the primary endpoint of ACR20 at week 24. There were no scenarios in which the 90% confidence interval (CI) failed to rule out a 12% loss/increase in the ACR20 response. Conclusions The tipping point sensitivity analyses support the findings of the key efficacy analyses in the phase 3 RA study and confirm that the effects of missing data would not change the conclusion of clinical similarity between ABP 501 and the RP. Disclosure of Interest N. Zhang Shareholder of: Amgen Inc., Employee of: Amgen Inc., H. Wang Shareholder of: Amgen Inc., Employee of: Amgen Inc., E. Krishnan Shareholder of: Amgen Inc., Employee of: Amgen Inc.