An FDA advisory panel yesterday narrowly recommended approval for the first-of-a-kind MitraClip heart implant made by Abbott (NYSE:ABT), designed to prevent blood from flowing backward across the mitral valve.
Although 8 panelists on the agency’s Circulatory System Devices Panel unanimously agreed that the MitraClip device is safe, they were evenly split on its effectiveness. Moderator Dr. Jeffrey Borer of State University of New York’s Downstate Medical Center broke the tie with his vote that available data for the device do not demonstrate reasonable assurance of effectiveness.
A majority of panelists, however, said MitraClip’s benefits outweighed its risks, with 5 panelists voting yes and 3 voting no.
Borer attributed his tie-breaker to problems interpreting data pooled from 2 different registries, neither of which were intended to be used as a pivotal data set. The registry data was used to come up with a post-hoc high-risk surgical group.
"I had a great deal of difficulty interpreting the registry data," Borer said. "At the end of the day, it was very difficult for me to know who I could say would benefit from this. I think somebody would. I think that this a potentially beneficial device, but I didn’t know who, and that was my concern, and that’s why I voted no."
"If your right shoe goes into horse poop and your left shoe goes into dog poop, it’s still poop. It’s hard to put these 2 things together and say that’s its even better than the individual," added Dr. Craig Selzman of the University of Utah’s School of Medicine.
The panel’s divided recommendations came after the federal watchdog expressed trepidation about approving the MitraClip in an executive summary released earlier this week.
"FDA believes the evidence necessary for determination of safety and effectiveness sufficient for approval of a first of a kind device should not be based on a retrospective evaluation of registry data re configured to support an indication for use and population for use developed post-hoc," according to the summary.
MitraClip is intended for patients who are too high-risk for open mitral valve surgery (as determined by a cardiac surgeon), but who are healthy enough otherwise to benefit from correction of mitral regurgitation.
The MitraClip device is a single sized, percutaneously implanted mechanical clip, which grasps and coats the mitral valve leaflets, resulting in "fixed approximation of the mitral leaflets throughout the cardiac cycle," according to the FDA. MitraClip, made of metal alloys and polyester fabric, consists of 3 major components: The delivery catheter, a steerable sleeve and the MitraClip device itself.
Originally manufactured by Evalve, which was acquired by Abbott Vascular in September 2009 for $410 million, the MitraClip’s original indication was much broader than the 1 the Abbott is pursuing: All patients with significant mitral valve regurgitation, rather than just those for whom surgery is too risky.
After the FDA ruled that the data from MitraClip’s original clinical trial were insufficient to support approval, Abbott Vascular narrowed the indication and performed additional post-hoc analysis.
MitraClip has been on the market in Europe for 4 years "with good results," according to Abbott Vascular.
The company is pleased with the outcome of the panel and "we look forward to continuing discussions with the agency as it further assesses the MitraClip system," Abbott Vascular chief medical officer Dr. Charles Simonton said in prepared remarks. An Abbott spokesman told MassDevice.com that the company is expecting hear back from the FDA later this year.
The agency isn’t bound by the panel’s determination but often heeds the wisdom of its advisory panels.
Inside the voting
After casting their votes, the panelists explained why they were swayed in either direction.
Walter Reed National Military Medical Center’s Dr. Michael Ferguson said he did not believe MitraClip adequately demonstrated effectiveness.
"I would really like to have this device available for people," Ferguson noted. "It’s a pretty difficult decision, but I think that they just didn’t do a good job of defining the patient population that would benefit and clearly establishing that the patients who would receive the device were not surgical candidates."
While Dr. Valluvan Jeevanandam of the University of Chicago said he believed that there could be patients who would benefit from MitraClip, he also voted no on effectiveness.
"I just hope that it’s not put into patients who would benefit from regular surgery and I think we should put as many safeguards as possible to make sure that doesn’t happen, that this is really put into a very small group of people who are truly inoperable," Jeevanandam stressed.
Despite their questions about the data, a majority of panelists voted that MitraClip’s benefits outweigh its risks.
"The data that the sponsor presented had as many holes as Swiss cheese and the FDA did a fantastic job finding every 1 of them," noted Dr. Gregory Dehmer of Scott & White Healthcare at Texas A&M University. "Nevertheless, valid scientific data is not restricted to just randomized, controlled trials. There are other data that are acceptable, and I think the totality of the data that we see today swayed me to feel like this is a device that has value for a selected group of patients.
"I think the challenge moving forward is for the agency and the sponsor to again heavily reengage themselves and find a solution that would in a limited way allow this device to be available to a select group of patients," Dehmer added.
St. Mary’s Hospital’s Dr. Marc Katz said that even though "there wasn’t a lot of risk data presented," his limited experience with 1 patient who received MitraClip and benefited from it swayed him to vote that the device’s benefits outweigh its risks.
"The patient with multiple sclerosis, a previous stroke and wheelchair-bound was probably the singular patient that I referred for this device to another institution, and she’s done remarkably well with it, so I did have that in the back of my mind," Katz explained.
"I have a hard time saying to patients, ‘OK, they’ve got to wait another 5 years to have this available," he added. "In no way do I think this was an elegant study. I think it was really poor in lot of ways. I think we’re put in a hard position here, but weighing the alternatives and putting the patients out front, that was the deciding factor."