The advent of transcatheter heart valves has had a seismic effect on valvular disease: more patients can be treated more safely and more cheaply than ever before. The trouble is, the devices have only been approved for the replacement of two of the four valves in the human heart.
Abbott Laboratories (ABT) is attempting to extend the percutaneous approach to a third valve. Its MitraClip device is designed to repair, rather than replace, a malformed mitral valve. On March 20, an FDA panel will decide whether to advise the agency to allow this. But with efficacy data from its pivotal trial, Everest II, less than superb, Abbott must hope that the lack of a non-surgical alternative will swing the panel's vote.
The MitraClip is implanted using a catheter inserted into the femoral vein in the leg and threaded through to the heart. It is then used to pin the mitral valve's two leaflets together, partially closing them, with the intention of preventing valvular regurgitation -- the backflow of blood from the left ventricle into the left atrium.
Abbott is taking a cautious approach to U.S. approval, seeking the FDA's blessing in patients too sick to undergo open-heart surgery. This is a similar strategy to that employed by Edwards Lifesciences (EW) when it was seeking approval of the transcatheter aortic valve implantation (TAVI) device Sapien, still the only transcatheter heart valve on the U.S. market (see: "Therapeutic focus -- Transcatheter aortic valves boosted by guidelines," Oct. 1, 2012).
Approval of Sapien was subsequently expanded from patients entirely ineligible for surgery to include those with more moderate disease. Abbott will doubtless aim to walk the same path.
The first step on that journey is to get MitraClip past the adcom, and the Everest II results will be key here. In Abbott's favor are data showing that the device was significantly safer than surgery, and that the two interventions showed similar cure rates, with 21% of MitraClip recipients and 20% of surgically treated patients being free from grade 3+ or 4+ mitral regurgitation at one year.
A green light is by no means assured, though. The trial’s primary endpoint, a combination of 12-month rates of death, surgery for mitral valve dysfunction, and grade 3+ or 4+ mitral regurgitation -- the most severe grades -- significantly favored surgery. Rates of death were the same in both arms, at 6%, so MitraClip's failure was solely based on the necessity for revision surgery.
MitraClip was CE marked five years ago, and analysts from JPMorgan suggest that sales in Europe could reach $140 million this year. Joanne Wuensch, a BMO analyst, expects European sales to double in 2013, aided by reimbursement in Germany, which began last month. But the FDA is harder to please than the European authorities. Abbott must hope that MitraClip's safety will see it through.