By Bill Berkrot

April 22 (Reuters) - Bristol-Myers Squibb Co said its lead experimental drug for nonalcoholic steatohepatitis, or NASH, significantly reduced liver fat versus placebo, according to data from a mid-stage trial presented at a medical meeting on Saturday.

NASH, a progressive fatty liver disease tied to obesity and diabetes, afflicts about 5 percent of the population and is poised to become the leading cause of liver transplants. Many companies are developing drugs for the complex disease for which there are no approved treatments.

The 16-week, 74-patient trial tested the subcutaneously-injected drug, BMS-986036, at two dosing regimens versus placebo in adults whose NASH was confirmed by liver biopsy. Both the 10 mg dose given daily and a 20 mg once-a-week injection met the main goal of significantly reducing liver fat.

Liver fat was reduced 6.8 percent with the daily injections and 5.2 percent for the weekly dose compared with 1.3 percent for placebo.

In addition, the Bristol-Myers drug reduced biomarkers for fibrosis, the scarring that can lead to cirrhosis, cancer and liver failure, as well as measures of liver stiffness and enzymes indicative of liver injury, data showed.

"These data suggest that BMS-986036 may be effective in patients with NASH, many of whom will experience disease progression due to the lack of available treatment options," Dr. Arun Sanyal, the study's primary investigator from Virginia Commonwealth University in Richmond, said in a statement.

"The results of this study show that BMS-986036 had beneficial effects on three important components in the treatment of NASH: liver fat, liver injury and fibrosis," said Sanyal, a leader in the field who presented the data at the European Association for the Study of the Liver (EASL) conference in Amsterdam.

The drug is a pegylated, or long acting, version of a natural human hormone called fibroblast growth factor 21, a regulator of metabolism believed to be effective because of the varied metabolic drivers of the disease.

The Bristol drug also led to improvements in cholesterol and triglycerides, researchers reported. At least one NASH drug further along in development from another company led to a rise in "bad" LDL cholesterol, which caused some concern.

There were no deaths, serious side effects or discontinuations due to adverse side effects reported among patients who received the Bristol drug. The most frequently reported side effects were diarrhea, nausea and frequent bowel movements, none of which were considered severe, the company said. (Reporting by Bill Berkrot; Editing by Cynthia Osterman)