Boceprevir is considered one of the most important products being developed by the Kenilworth, N.J., drugmaker, which is being acquired by Merck & Co. (which has Philadelphia-area operations) for $41.1 billion.

Initial results from the late-stage study, called Sprint-1, were reported earlier this year, but on Sunday, Schering-Plough reported the results of patients who had no response to other drugs, a hard-to-treat group called "null responders."

A total of 50 patients were found to be "null responders" after four weeks of standard treatment.

After 28 weeks of treatment, Schering-Plough said 25 percent of the null responders had a "sustained virologic response," meaning their virus levels were too low to measure. After 48 weeks of treatment, 55 percent of patients had a sustained virologic response.

The result was similar to data reported by Vertex Pharmaceuticals Inc. on Wednesday. Vertex said 57 percent of null responders had a sustained response after 48 weeks of treatment with the company's drug telaprevir.

The results were presented in Boston at a meeting of the American Associated for the Study of Liver Diseases.

Also today, Schering-Plough said it was taking an "adopt a village" approach to battling human and animal rabies in two regions of India.

The company said it would provide $200,000 and rabies vaccine from Intervet/Schering-Plough, and work with medical and veterinary caregivers to educate people and to undertake a mass vaccination of dogs.

Rural Indian villages are vulnerable to rabies, according to the World Health Organization, which cites the country as having the highest incidence of human rabies, accounting for an estimated 20,000 of the 55,000 deaths reported worldwide each year.