By Brendan Pierson

Dec 10 (Reuters) - Philadelphia's transportation authority has filed a class action lawsuit accusing Gilead Sciences Inc of charging "exorbitant" prices for its blockbuster hepatitis C drug Sovaldi.

The lawsuit, filed Tuesday in federal court in Philadelphia by the Southeastern Pennsylvania Transportation Authority, seeks an unspecified amount of money damages.

Sovaldi, a highly effective treatment for hepatitis C, costs $1,000 per pill in the United States, or $84,000 for a typical 12-week course. The drug sells for much less in some other countries.

The lawsuit claims that Gilead's pricing is an abuse of its patent monopoly on the drug and violates federal antitrust laws.

Gilead's "limited rights as a patent holder do not translate into a license to price gouge consumers," the lawsuit said.

The transportation authority, which said it has paid more than $2.4 million for Sovaldi for its employees, is seeking to represent a class of everyone in the United States who has paid for Sovaldi or has not been able to afford needed Sovaldi treatment.

Sovaldi has brought in more than $8.5 billion for Gilead in the first three quarters of 2014, just under half the company's total sales.

Gilead did not immediately respond to an email seeking comment.

The case is Southeastern Pennsylvania Transportation Authority, individually and on behalf of all others similarly situated, v. Gilead Sciences Inc, U.S. District Court, Eastern District of Pennsylvania, No. 2:14-cv-06978.

(Reporting by Brendan Pierson,; Editing by Alexia Garamfalvi and Richard Chang)