Newly Approved Weight Loss Device Blocks the Vagus Nerve

We have known for a long time that the brain regulates hunger and fullness. The brain also regulates energy balance and adipose tissue energy stores. The brain receives signals from throughout the body, including the gut. The signals come through afferent nerves and through circulating hormones. This knowledge led to research to manipulate the signals sent to the brain from the stomach and intestines. As it turns out, the vagus nerves, the two major nerves that carry signals to and from the brain, became a treatment target.

VBLOC vagal blocking therapy delivered via the Maestro System is now approved to treat adults age 18 to 65 years with a body mass index (BMI) of 40 to 45 kg/m2 or >35 kg/m2 and 1 or more obesity-related complications. The device is indicated for patients who have tried to lose weight in a supervised weight management program within the past 5 years.

The device blocks the abdominal vagus nerves to help control hunger between meals and promote fullness earlier after eating, according to the device’s manufacturer EnteroMedics Inc. Electrical pulses are intermittently sent by a rechargeable pulse generator to electrodes that are surgically implanted on the trunks of the abdominal vagus nerves (Figure). The pulse generator is controlled using an external clinician programmer to allow physicians to tailor therapy as necessary. The specific mechanisms underlying the weight loss effect of the device are unknown, according to the U.S. Food and Drug Administration (FDA).

The device is designed to operate for up to 8 years and stimulation may be stopped at any point if needed.

Clinical Trial Findings
The device was evaluated in a clinical trial involving 233 patients with a BMI of ≥35 who received the activated device (experimental group) and 76 patients who received only an inactivated pulse generator (pulse generator). All patients also participated in a weight management program, including 17 individual consultations with an advisor, in which they were taught how to modify their meal plan, level of physical activity, and behavior.

After 12 months, the experimental group lost an average of 8.5% more excess weight than the control group. Approximately half (52.5%) of the patients in the experimental group lost at least 20% of their excess weight, and 38.3% lost at least 25% of their excess weight compared with 32.5% and 23.4% in the placebo group, respectively. For comparison, the reported weight loss as a percentage of excess body weight after 1 to 2 years, is 50% to 72% following vertical banded gastroplasty, 33% to 58% following sleeve gastrectomy, and 48% to 85% following Roux-en-Y gastric bypass.

The experimental group did not meet the primary outcome of a significantly greater percentage of excess weight loss (defined as ≥10%) compared with the control group. However, an FDA Advisory Committee found that 18-month data from the study was supportive of sustained weight loss, and agreed that the benefits of the device outweighed the risks in patients who met the indication criteria. In addition, approval was based on an FDA-sponsored survey indicating that patients would accept risks associated with this surgically implanted device given amount of expected weight loss.

Side Effects Profile
Serious adverse events reported in the clinical study included nausea, pain at the pulse generator implant site, vomiting, and surgical complications. Other adverse events included pain, heartburn, problems swallowing, belching, mild nausea, and chest pain. The device is contraindicated in people who have liver cirrhosis, portal hypertension, esophageal varices, clinically significant hiatal hernia, other implantable devices (eg, pacemakers, defibrillators, neurostimulators), or who are at high risk for surgical complications. In addition, patients who need magnetic resonance imaging, or shortwave, microwave, or therapeutic ultrasound diathermy in the near future should not receive the device.

As part of the approval, EnteroMedics is conducting a 5-year post-approval study following at least 100 patients to monitor safety and effectiveness data.

March 19, 2015

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