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EnteroMedics: A Preview of the Weight-Loss Zapper FDA Panel

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NEW YORK ( TheStreet) -- EnteroMedics and its VBLOC "fat-zapping" implantable medical device will be the focus of an FDA advisory panel meeting next Tuesday, June 17. If FDA follows historical form, the agency's review of VBLOC's safety and efficacy will be available publicly tomorrow morning. 

I'm eager to read the FDA review to see how the agency interprets data from two clinical trials in which obese patients on VBLOC therapy failed to achieve statistically significant "excess weight loss" compared to patients implanted with a sham devices . EnteroMedics is seeking FDA approval of VBLOC on the basis of two studies which failed their respective primary efficacy endpoints. This seems like a Hail Mary regulatory strategy, but EnteroMedics argues for a more holistic view of the VBLOC data: Sure, the pre-specified efficacy endpoints of the studies were not met, the company argues, but VBLOC-treated patients still lost weight and the pacemaker-like device is safe, so it should be approved. 

Normally, I'd say EnteroMedics has a low single-digit probability of convincing the experts on Tuesday's panel to recommend approval, but VBLOC is a medical device.  Anyone who follows the FDA and medical device reviews knows strange things can (and often do) happen. (Remember Mela Sciences ?) If the FDA review of VBLOC tomorrow is relatively benign, EnteroMedics just might have a decent shot at a positive panel vote, despite the device's mediocre weight-loss profile.

Of course, if FDA slams VBLOC, EnteroMedics will be in a heap of trouble Tuesday. 

Let's go way back to February 2013 when EnteroMedics announced results from the phase III "RECHARGE" study, which is the more important of the two VBLOC studies and will garner the most discussion next week. 

RECHARGE failed. VBLOC-treated patients achieved a 24.4% average excess weight loss (EWL) compared to 15.9% for patients implanted with a sham device. To meet the study's pre-specified "super-superiority" primary efficacy endpoint, the difference in EWL needed to be at least 20%. The reported difference of 8.5% didn't come close. (A second, co-primary efficacy endpoint also failed.)

EnteroMedics wants to throw out the "super-superiority" EWL requirement designed into the trial, arguing that the 8.5% EWL difference favoring VBLOC over sham control is statistically significant and clinically meaningful. 

Okay, but will FDA agree? We'll know more tomorrow when the agency's briefing documents are released. The 20% "super-superiority" EWL efficacy margin was designed into the VBLOC study for a reason. Obviously, companies developing medical devices or drugs don't design pivotal clinical trials with pre-specified endpoints that are more difficult to achieve than necessary. 

My hunch here is FDA required the super-superiority efficacy margin because the double-blinded RECHARGE study isn't really blinded at all. Patients know if the VBLOC implanted in their chest is active because they feel the electrical shocks being applied to their vagus nerve. Sham devices aren't turned on, hence no shock, no sensation.