One down, three to go, since the US Patent & Trademark must still rule on the remaining three Viread patents. The move comes in response to a challenge made last summer by the Public Patent Foundation because the FDA won’t allow any other entity to distribute Viread in the US. Gilead, which also markets Viread as part of its Atripla combo, claims the four patents offer exclusive rights.

“We have always believed the US PTO would recognize that Viread is a novel product, and we remain confident the office will rule similarly on the remaining three patents under review,” Gregg Alton, Gilead’s general counsel, says in a statement.

We have asked the Public Patent Foundation for a comment and will update if one is received. Earlier this year, by the way, the USPTO invalidated the four Viread patents, but Gilead dismissed the move as a procedural step that allowed the drugmaker to answer questions raised by the challenge.