Shares of

Neurocrine Biosciences

(NBIX) - Get Report

slipped Wednesday after the company said the results of a midstage clinical trial showed an experimental multiple sclerosis drug didn't work.

The San Diego-based company, which has been conducting MS research since the late 1990s, said it will halt its MS drug efforts to instead continue focusing on conditions like diabetes, congestive heart failure and endometriosis.

The stock was off 54 cents, or 0.8%, to $68.16, but had earlier been as low as $66.95.

The Neurocrine product closest to commercialization is the insomnia treatment Indiplon, which is now before the Food and Drug Administration.

Pfizer

(PFE) - Get Report

is the marketing partner. Neurocrine says the FDA is expected to act in mid-May.

Indiplon also is being reviewed by the Drug Enforcement Administration as a controlled substance. Neurocrine said Wednesday the drug will likely be classified as a Schedule IV drug, the second-mildest DEA designation. Most competing insomnia drugs are Schedule IV drugs.

The company's preclinical MS research indicated there might be a way to reduce the severity and progression of the disease for long periods of time. Because MS is caused by the body's immune system attacking healthy cells in the central nervous system, Neurocrine looked for a way to stop the initial attack. But a clinical trial involving 157 people over nine months didn't meet its goals.

Neurocrine tested the same compound with

Novartis

(NVS) - Get Report

in the 1990s. In July 1999, an independent safety data monitoring committee recommended that a clinical trial be halted to allow Novartis to review the data, Neurocrine says.

The trial was discontinued due to "systemic hypersensitivity-type reactions." Neurocrine reacquired the rights to the compound in January 2000 and commenced a new trial in 2003.