Eli Lilly and Co. said a potential treatment for acute schizophrenia failed in a late-stage study that compared patients taking the drug to those taking a placebo.

The Indianapolis drugmaker said Wednesday that patients taking the drug, labeled pomaglumetad methionil, showed no difference in progress compared to those taking a placebo. A control group of patients taking another drug, risperidone, which goes by the brand name Risperdal, did show a difference.

Lilly said the study was one of two late-stage trials being conducted to support use of the drug, also known as mGlu2/3, as a stand-alone treatment for acute schizophrenia. The company plans to continue the second study as well as a mid-stage trial that uses the drug in combination with some atypical antipsychotics to help determine its fate.

The drugmaker is studying pomaglumetad methionil to see whether it can work as an antipsychotic without side effects like weight gain that come with current treatments.

Lilly lost U.S. patent protection for its all-time, best-selling drug, the antipsychotic Zyprexa, last fall. It also faces more patent expirations in the next few years that will expose some of its best-selling drugs to cheaper, generic competition. Some analysts are concerned about the drugmaker's ability to replace the lost revenue.

Lilly has said it will depend on sales from developing countries, its animal health business and its pipeline of drugs under development, among other revenue sources. A company spokeswoman said Wednesday Lilly has 12 potential treatments in late-stage clinical testing.

Company shares fell 20 cents, to $42.66 each, in morning trading Wednesday, while broader trading indexes slipped less than 1 percent.