April 2 (Reuters) - A pivotal trial of Gilead Sciences Inc's hepatitis C drug sofosbuvir, sold under the brand name Sovaldi in the United States, showed that the drug is safe and effective in treating Japanese patients infected with a common form of the virus.

Gilead, based in Foster City, California, said on Wednesday it expects to file by mid-year for regulatory approval of the pill in Japan.

The trial involved 153 patients infected with genotype 2 hepatitis C, which the most common form of the liver-destroying virus in Japan and China.

Gilead said the study met its goal, showing that 98 percent of previously-untreated patients achieved undetectable levels of the virus three months after completing 12 weeks of treatment with a combination of sofosbuvir and ribavirin. For previously-treated patients, the response rate was 95 percent.

Side effects seen in the trial included anemia and headache.

Wall Street analysts, on average, have forecast Sovaldi sales of $9.1 billion in 2017, according to Thomson Reuters Pharma.

(Reporting by Deena Beasley; Editing by Marguerita Choy)