For nearly four years, the U.S. government and HIV drugmaker Gilead Sciences have been battling over the patent for the HIV prevention meds Truvada and Descovy. The case goes to federal court this week. The jury is to be selected on Tuesday, May 2, and the trial is expected to last six days, reports The Washington Post.

The trial has been a long time coming, with many twists and detours along the way, and it marks a rare case in which the federal government—on behalf of the Centers for Disease Control and Prevention (CDC)—is aggressively suing a drugmaker over patent infringement. The government seeks over $1 billion, according to Reuters, noting that Gilead made over $2 billion from sales of Truvada and Descovy just last year.

Here’s a primer on the lawsuit so far.

On November 6, 2019, the federal government filed a complaint against drugmaker Gilead Sciences over the patents for Truvada and Descovy—two meds used as pre-exposure prophylaxis (PrEP) to prevent HIV. (Descovy is an updated version of Truvada; both tablets contain two different meds. The tablets are taken daily to prevent HIV and also prescribed as treatment for some people living with HIV.)

The Food and Drug Administration (FDA) approved Truvada as PrEP in 2012 and Descovy as PrEP in 2019. Truvada was initially approved in 2004 as treatment for people living with HIV, while Descovy was approved in 2016. So why did it take the federal government three years to initiate legal action?

In March 2019, the activist group PrEP4All claimed that the CDC held the patent for Truvada’s use as PrEP because researchers with federal grants (and additional funding from the Bill & Melinda Gates Foundation) were the first to prove that the drug worked very well as prevention. The advocates wanted royalties from Gilead to fund a national PrEP program to make the med accessible to everyone regardless of their ability to pay. (For background, see this POZ article.)

In November 2019, the government filed a patent lawsuit against Gilead regarding Truvada as PrEP, including the updated version Descovy. (You can read the Department of Health and Human Services press release here.)

In April 2020, Gilead fired back with a breach-of-contract lawsuit, alleging that the government had secured its patents by breaching five contracts with the pharmaceutical manufacturer. (Read Gilead’s statement about that here.)

In December 2020, the judge said the government could not dismiss Gilead’s claims. The drugmaker also alleged that it suffered damages in the form of harm to its reputation and the likelihood that it would receive less favorable license terms.

Fast-forward a year and…not much happened. Spurred by the lack of action, in January 2022, PrEP4All and HIV advocates sent letters to federal health officials demanding an update on the drug patent lawsuit United States v. Gilead.

As the case slowly moved forward, Gilead kept many of its documents under seal, allegedly to protect sensitive information. In March of this year, PrEP4All and the Public Interest Patent Law Institute urged the court to review the situation, alleging that Gilead was over-redacting files. As Bloomberg reported, Gilead agreed to make public nearly two thirds of the files that were under seal.

The court case between the U.S. government and Gilead is but one of several lawsuits involving HIV drugs. For other examples, all from last year, see:

PrEP has made other national headlines lately. In September 2022, a district judge in Texas ruled that requiring health insurance to cover PrEP as HIV prevention violates the religious beliefs of a Christian-owned company. In March 2023, a federal judge in Texas struck down the mandate that health insurance must cover many preventive health care services, including some cancer and diabetes screenings, HIV tests and PrEP. The ongoing case could jeopardize access to preventive care.

Meanwhile, PrEP4All and other advocates continue to urge lawmakers and the White House to create a national PrEP program.