On November 6, the United States government filed a lawsuit against Gilead Sciences, seeking damages for the company’s alleged infringement of patents related to pre-exposure prophylaxis (PrEP), according to a news release from the Department of Health and Human Services (HHS).

The lawsuit comes several months after advocates revealed that the Centers for Disease Control and Prevention (CDC), which is part of DHHS, holds patents on the use of Truvada (tenofovir disoproxil fumarate/emtricitabine) for PrEP. At that time, Truvada was the only approved PrEP regimen. Since then, the Food and Drug Administration has approved Descovy (tenofovir alafenamide/emtricitabine) as a second option; the new pill is also included in the new lawsuit.

“HHS recognizes Gilead’s role in selling Truvada and Descovy to patients for prevention of HIV. Communities have put these drugs to use in saving lives and reducing the spread of HIV,” said HHS Secretary Alex Azar II. “However, Gilead must respect the U.S. patent system, the groundbreaking work by CDC researchers, and the substantial taxpayer contributions to the development of these drugs. The complaint filed today seeks to ensure that they do.”

After Truvada was approved for HIV treatment in 2004, government-funded researchers at the CDC spearheaded testing to evaluate whether it could also prevent infection; Gilead provided the drug for free for some of this research.

After a series of successful studies in monkeys, Robert Grant, MD, of the University of California at San Francisco, and colleagues showed that once-daily Truvada reduced new infections by more than 90% among mostly gay and bisexual men who used it consistently. Further clinical trials and real-world use indicate that once-daily PrEP is around 99% effective at preventing HIV acquisition if used correctly.

Although Gilead holds patents on the Truvada and Descovy coformulations and the drugs they contain, the federal government separately patented the use of Truvada for HIV prevention. Advocates with the PrEP4All Collaboration researched the government patents and commissioned an outside legal review by patent experts from the Global Health Justice Partnership at Yale Law School and the Yale School of Public Health.

According to this week’s announcement, the United States Patent and Trademark Office has granted four patents to HHS that “protect CDC’s work and the taxpayers’ investment.” These patents entitle the government to license the CDC’s PrEP regimens and receive a “reasonable royalty” for their use.

But so far, all revenues from the sale of Truvada and Descovy for PrEP have gone to Gilead, not the government.

The new lawsuit alleges that Gilead “has willfully and deliberatively induced infringement of the HHS patents,” adding that the company’s conduct was “malicious, wanton, deliberate, consciously wrongful, flagrant, and in bad faith.”

The complaint further alleges that, as a result of such infringement, “Gilead has profited from research funded by hundreds of millions of taxpayer dollars and reaped billions from PrEP through the sale of Truvada and Descovy.” The announcement says HHS has made “multiple attempts” to license its patents to Gilead, but the company has refused.

Truvada sells for around $1,600 per month, and it brought in about $3 billion in sales last year. Gilead offers a patient assistance program and co-pay card that keep out-of-pocket costs low for many individuals who use PrEP, but some people still have trouble affording it, and the cumulative cost is a burden for public health programs that aim to expand the use of the prevention pill.

Advocates have called on Gilead to pay royalties on the use of Truvada forPrEP going forward and retroactively to 2012. They want the government’s royalty revenue to fund a national program that would include the provision of low-cost PrEP and related services, such as lab tests and clinical care, with a focus on communities where PrEP is currently underutilized.

“While yesterday’s action is important, the lawsuit alone will do little to increase access to PrEP," PrEP4All cofounder James Krellenstein said in a statement. “The government must now use these patents to get PrEP to everyone who needs it and create a universal HIV prevention program that alleviates all of the barriers perpetuating the HIV epidemic. This step wouldn’t cost taxpayers a dime.”

In August, Gilead challenged the government’s patents, contesting claims that government-funded researchers had invented PrEP. At press time, Gilead had not responded to a request for a statement on the federal complaint.

[UPDATE: Gilead later issued a statement responding to the lawsuit. “We strongly believe that the patents granted to HHS since 2015 for PrEP and PEP [post-exposure prophylaxis] are not valid and reject any notion of willful infringement. HHS improperly filed for patents without alerting Gilead, despite its obligation to do so, and we have openly explained the defects in the patents since becoming aware of them,” the company said. “As we have presented both to HHS and to the Patent Office, there is compelling evidence demonstrating that the HHS patents are invalid. Published materials clearly show that, well before HHS claims to have invented the concepts of PrEP and PEP in 2006, others had conceived of using an antiretroviral therapy, including Truvada…for both forms of prophylaxis.”]

This week’s lawsuit is only the latest of the company’s legal woes related to its HIV products. An ongoing antitrust lawsuit alleges that Gilead and collaborating drug companies illegally established a near monopoly on HIV combination pills by restricting generic competition. Other lawsuits claim that Gilead withheld the safer tenofovir alafenamide (the version of the drug in Descovy) until patents on the older tenofovir disoproxil fumarate (the version in Truvada) were near expiration, causing some individuals to unnecessarily develop kidney and bone problems related to the older drug.