Abbott Vascular's 2-Year ABSORB III Data Presented; FDA Issues Warning Letter
March 18, 2017—Abbott Vascular announced that data from ABSORB III, the company's United States pivotal trial of its Absorb bioresorbable vascular scaffold, showed that the device had comparable efficacy and safety results to its Xience metallic drug-eluting stent between 1 and 2 years after implantation. The data were presented by Lead Investigator, Stephen Ellis, MD, during a Late-Breaking Trials session at ACC.17, the American College of Cardiology’s 66th annual scientific session in Washington, DC. Dr. Ellis is a cardiologist at the Cleveland Clinic in Cleveland, Ohio.
According to Abbott Vascular, the ABSORB III trial results showed no statistically significant difference in incremental rates of target lesion failure (TLF) and stent thrombosis between 1 and 2 years for Absorb versus Xience. TLF for Absorb was 3.7% vs 2.5% for Xience (P = .18); stent thrombosis was 0.3% for Absorb versus 0% for Xience (P = .31).
Cumulative 2-year TLF rates were higher with Absorb than Xience, particularly when the device was implanted in small vessels, which occurred in 19% of patients in the study. TLF was 11% for Absorb versus 7.9% for Xience (P = .03). However, when implanted in appropriately sized vessels, the difference was smaller and not statistically significant at 9.4% for Absorb versus 7% for Xience (P = .11). When the recommended pre- and postdilatation techniques were used in addition to appropriate vessel sizing, the results for TLF and stent thrombosis were improved even further at 8.7% for Absorb versus 8.2% for Xience (P = .84), demonstrating the devices had similar outcomes, noted the company.
An ongoing study, ABSORB IV, which is expected to enroll a total of 3,000 patients, was started after the implantation technique had evolved. A preliminary analysis of pooled rates (combined for both Absorb and Xience because the study is not yet unblinded) showed stent thrombosis rates of 0.4% at 30 days (n = 2,397) and 0.5% at 1 year (n = 1,415), which were less than half of the stent thrombosis rates observed in ABSORB III (0.9% at 30 days and 1.1% at 1 year).
The 1-year results from ABSORB III, which were presented in October 2015, showed comparable outcomes between Absorb and Xience for the study's primary endpoint of TLF. These data were the basis for the US Food and Drug Administration (FDA) approval in July 2016.
Abbott Vascular advised that when Absorb received FDA approval, the instructions for use specified the avoidance of very small vessels and included optimal implantation guidelines. The company also stated that from the time the ABSORB III study began in 2012, training on the device has evolved based on what has been learned in the medical community and by physician experience. The company's emphasis on implantation techniques for the Absorb device includes a global training program for physicians. In the United States, Abbott requires physicians to undergo comprehensive training before they are able to implant Absorb.
Abbott Vascular noted that as part of a March 18 FDA letter to health care providers, the agency emphasized the importance of following instructions for target vessel selection as outlined in the product label and recommended that physicians use optimal methods when implanting Absorb.