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ROSEVILLE, Minnesota– What to do if you’re an EnteroMedics Inc. investor?

The company, which is developing a device that uses electricity to treat obesity and diabetes, Thursday said data from a key clinical trial showed its VBLOC therapy “remain encouraging, with signs of clinically meaningful weight loss and control of obesity.” Furthermore, patients using a more advanced version of the Maestro device for 14 hours a day lost weight and demonstrated significantly reduced levels of HbA1c (glycated hemoglobin) levels in the blood.

Sounds good. One major problem: EnteroMedics is a company dangling precariously off a cliff. Last fall, Enter0Medics said initial results from its Empower clinical study failed to meet its goals.

Huh? Didn’t I just say the company reported positive results this week?

Let’s back up for a second. EnteroMedics, founded in 2002, heads a class of promising start-ups pioneering the use of neuromodulation to treat obesity. Leptos Biomedical Inc. in Fridley, IntraPace Inc. of Mountain View, Calif., and MetaCure USA Inc. in Orangeburg, N.Y., all seek to control hunger by shooting electrical impulses into the digestive system.

Medtronic Inc. also is researching this area. In 2005, the company formed a new unit, Medtronic Obesity Management, after purchasing Transneuronix Inc., which focused on developing a pacemaker-like device to stimulate the stomach.

But EnteroMedics is far ahead of the pack; its Maestro device shoots electricity into the vargus nerve, blocking signals from the brain to the stomach and pancreas that cause feelings of hunger, fullness and satisfaction. The Food and Drug Administration will decide on whether to grant pre-market approval sometime this quarter.

Everything seemed fine until last October when EnteroMedics dropped a bombshell: Initial results from the Empower studies of more than 400 patients showed the company did not hit its designed targets. People who used the Maestro device lost weight — but so did the people who didn’t.

In every clinical trial, there are two groups of patients: The treated group receive the actual therapy while a control group gets a placebo or standard treatment. The results are then compared. Ideally, treated patients should demonstrate a higher degree of efficacy than the control group.

That didn’t happen with Empower. The number of patients showing an excess weight loss (EWL) of greater than 25 percent were identical in the treated and control groups. Du-oh! At 12 months, the patients who used the real device for more than 9 hours a day demonstrated an average EWL of 23.1 percent compared to 22.6 percent in the control group.

At the JP Morgan Healthcare conference in San Francisco Thursday, EnteroMedics CEO Mark Knudson said evidence showed the body in the control group somehow blocked electrical signals on the vargus nerve without the use of the device, an unexpectedly powerful placebo effect. He also noted the effect was gradual in the control group while treated patients experienced an immediate blocking effect.

The result doesn’t necessarily mean Maestro doesn’t work. It just means the control group did just as well. But whether that’s good enough for the FDA remains to be seen. And given the mood of the FDA these days, I wouldn’t hold my breath.

“We don’t know how the FDA is going to react” to the data, Knudson said.

If the FDA rejects Maestro, EnteroMedics is finished. Given the poor economy, finding investors willing to continue writing checks would be next to impossible. (EnteroMedics did say Thursday that it raised another $4.8 million.)

Just look at what happened last fall. After the company reported the disappointing Empower results, EnteroMedics stock plummeted from $5.40 a share to less than $1 a share in just a few days. The company now trades around 70 cents a share. EnteroMedics also immediately reduced its workforce by 40 percent to 33 employees.

Hang on to your hats EnteroMedics investors. It’s going to be a bumpy ride.