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Phase 3 Trial Initiated on Absorb BVS
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Abbott has announced the initiation of the randomized controlled ABSORB III clinical trial on its Absorb Bioresorbable Vascular Scaffold to support regulatory filings in the United States.
The trial will compare the Absorb Bioresorbable Vascular Scaffold (BVS) with the company’s Xience family of drug-eluting stents. Besides eluting the drug everolimus, the BVS is made of polylactide, a dissolvable material commonly used in medical implants such as dissolving sutures.
The ABSORB III trial will enroll approximately 2,250 patients, mostly from in the United States, and the primary endpoint will be target lesion failure at 1 year. Additionally, a subset of patients will be evaluated on novel endpoints, including vasomotion.
This news follows the recent international launch of the BVS in Europe and parts of Latin America and Asia, and the recent regulatory approval and launch in India.
Perspective
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Dean J. Kereiakes
Conceptually, the fully bioabsorbable platform takes flexibility and conformability to a whole new level. There are probably at least eight or nine reasons why a completely bioabsorbable platform might be better than a metal platform. Some of the reasons include that it allows for adaptive remodeling, the “Glagov effect,” which allows the vessel to accommodate atherosclerosis before an obstruction becomes evident; there is a return of normal auto-regulatory function; microcirculatory function is often abnormal downstream from the stented segment with metal platform stents, particularly first-generation DES, which isn’t going to be a problem with bioabsorbable stents; and side branch access or imaging, whether with MR or CT, are not going to be issues with the BVS.
Another thing that has been observed with BVS that is not seen with metal-platform stents is positive remodeling or an actual increase in vessel area. Specifically, as observed by IVUS, there was a 7% increase in lumen area from 6 months to 2 years after BVS. This positive remodeling effect that occurs with BVS is distinctly unusual and is likely a good thing. An additional issue that is very current is neoatherosclerosis. DES are susceptible to this, as are bare-metal stents. Neoatherosclerosis should not be an issue with BVS.
The limitations of BVS are that it has thick struts, is not as deliverable as some current metal platform stents and use in complex anatomy, particularly calcified vessels, is not well defined at this point. In fact, these issues are not going to be resolved after the ABSORB trial has enrolled because of multiple angiographic exclusions. So, a question mark with BVS will be general applicability and whether there is incremental benefit beyond 1 year compared with Xience Promus based on a reduction in late (beyond 1 year) target lesion failure.
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