Obesity device before FDA panel despite not meeting primary endpoints

Maestro System--Courtesy of EnteroMedics

An implantable device to treat morbid obesity with vagal nerve blocking therapy will be considered by the FDA's Gastroenterology-Urology Devices panel on June 17. Its chances going into the meeting don't look great: The panel documents point out that it didn't meet either of its primary efficacy endpoints and the panel date was already delayed once in March. Still, while the 12-month data aren't good, at 18 months the device looks a bit more promising.

The very first question from the panel in newly release documents addresses the lack of efficacy data. The primary effectiveness endpoint was to demonstrate at least a 10% improvement over control in excess weight lost as measured by body mass index after 12 months.

The Maestro System from EnteroMedics, which includes an implantable device that intermittently blocks inter-abdominal vagus nerve signaling, showed that 24.4% of excess weight was lost, while the control group shed 15.9% of excess weight. The difference between the two groups was 8.5%, not the 10% improvement that's the standard for demonstrating efficaciousness in weight loss.

In addition, the secondary co-primary effectiveness endpoint also was not met. It had two parts: that at least 55% of subjects lost at least 20% of their excess weight and that at least 45% of subjects lost at least 25% of their excess weight. Of the data for subjects using the Maestro System, 52.5% of the subjects lost at least 20% of their excess weight, while 38.3% lost at least 25% of their excess weight.

Although neither of the effectiveness endpoints were met at 12 months, the company provided 18-month results that are better. At this time point, patients on vagal nerve therapy had lost 25.2% of their excess weigh while the sham control group lost 11.7%--that's a difference of 13.5%, which exceeds the 10% threshold.

EnteroMedics also made a mixed case with data on co-morbidities. For patients with the Maestro System at 12 months, mean HDL cholesterol ("good cholesterol") increased more than for the sham group; LDL cholesterol ("bad cholesterol") fell more than for control; and triglycerides fell less than for control.

The system met the safety endpoint of less than 15% of treatment subjects requiring implant or revision procedures at 12 months.

The panel is also considering whether it should require a five-year, post-approval effectiveness study. If it votes in favor of the device, given the mixed data, this seems a likely requirement.

The Maestro System consists of a subcutaneously implanted neuroregulator and two electrodes that are placed near the ribs. It's recharged via an external mobile charger and transmit coil worn by the patient. The device intermittently blocks vagal nerve signals during the patient's waking hours.

Microcap EnteroMedics was down 7% to $1.50 in early trading on the release of the FDA panel documents. It had already fallen hard when the panel was pushed back in March.

- here are the FDA panel documents