The Department of Justice has launched a review of a government patent for use of a drug that prevents HIV infection, according to a retired Centers for Disease Control scientist who was among scientists who spoke with a department lawyer last week.

Thomas Folks said a Justice Department lawyer visited the CDC in Atlanta on April 16 to question government scientists who pioneered the use of the drug Truvada for prevention.

Folks, who retired from the CDC in 2007, participated in one of the meetings via telephone and helped explain the scientific discoveries his government team made 15 years ago.

The meetings are the first indications the government is considering action against Truvada’s manufacturer, Gilead, which contends the government’s 2015 patent is invalid and has publicly rebuffed requests for royalty payments.

The government has declined to take the rare next step and sue for patent infringement, The Washington Post reported last month.

The lack of action has enraged HIV activists,with some protesters hecklingthe CDC director at a meeting in Virginia on April 1. It also has attracted attention on Capitol Hill. Sen. Debbie Stabenow (D-Mich.) led a small group of senators this week in writing to Health and Human Services Secretary Alex Azar, citing The Post article. The senators said taxpayers should be able to recoup public investments and help make vital drugs more affordable. Read more via Washington Post