Pharmasset Ltd., a drug development company focused on viral diseases, has reduced its initial public offering plans.

Pharmasset cut the number of shares to be offered to 5 million from 6 million and lowered the price to $9 from between $12 and $12 a share.

The company plans to trade on the NASDAQ under the symbol VRUS.

Venture backers include Burrill & Co., TVM Capital and MPM Capital.