In 2005, Gilead Sciences notified federal regulators that it was suspending development of a potentially safer, more potent HIV-fighting drug than the one on the market. The company did not restart its Food and Drug Administration application until 2010. Now the five-year delay of a promising drug is at the core of accusations by advocates that Gilead improperly exploited the patent system at the expense of patient health.

An HIV-prevention group called PrEP4All Collaboration filed a petition Wednesday with the U.S. Patent and Trademark Office contending Gilead knew its new, improved drug — approved in 2015 and now part of Gilead’s combination therapies Genvoya and Descovy — was safer. But it alleged Gilead postponed development so it could continue to gain monopoly profits from its older combination HIV drugs, including Viread and Truvada, for a longer period,before those drugs went off patent and faced generic competition.

Gilead used the delaying tactic even though the older drugs posed more risks to bone and kidney health, PrEP4All alleged.

The group is asking the Patent and Trademark Office to reject Gilead’s request for three extra years of patent life on the newer drug, called tenofovir alafenamide, or TAF. Odds of success are steep because the patent office will review such third-
party petitions only in “extraordinary’’ circumstances, according to its rules.

The group’s accusations mirror allegations in class-action civil lawsuits filed in a U.S. District Court in California against the company by patients who took Gilead’s medications and allege their health was compromised by the company’s actions.

Gilead has denied the allegations in the lawsuits. It said Wednesday the activists’ petition before the Patent and Trademark Office also has no merit and appears to be in conflict with laws governing requests for patent extensions.

“Patient safety is of foremost importance to us, and any implication that Gilead delayed the development of a drug known to be safer than [the older drug] is false,’’ said Gilead spokesman Ryan McKeel. He said Gilead has a three-decade track record of “developing and improving upon therapies that address unmet needs.’’

Brand-name drug companies spend heavily on legal strategies intended to extend patent protections on novel drugs, a practice known in the brand pharmaceutical industry as “life-cycle management.’’ Once exclusivity is lost and generic copies enter the market, competition can quickly drive down prices and profits.

Gilead won its patent on TAF in 2010, which is when it restarted its FDA application. Medications used to treat and prevent HIV are made by combining multiple individual drugs, and TAF is a key component of those combination tablets.

If granted, a three-year patent extension on TAF would allow Gilead to maintain monopoly pricing on key pillars of its HIV franchise until 2025 — a government action potentially worth billions of dollars to the company. Gilead reported HIV medication sales of $14.6 billion in 2018.

“Gilead has not only intentionally delayed clinical development of a drug to artificially manipulate its eligibility for a patent-term extension, but it has done so despite the apparent harm to patients,’’ said Christopher Morten, who is supervising attorney at New York University’s Technology Policy and Law Clinic, who filed the petition on behalf of PrEP4All.

As evidence, PrEP4All’s petition cites shifting statements by former Gilead executives, including public remarks in 2011 that seemed to indicate a desire to avoid cannibalizing sales of the old drug, and the expectation that the new drug would be key to maintaining the patent “longevity’’ of the company’s HIV drug franchise.

The petition also cites Gilead’s statements that clinical trials have indicated TAF is safer than the older drug, and a company-funded academic study that found preventing patients from taking the new drug would cause an additional 16,000 deaths over a nine-year span.

Gilead has been embroiled in a separate patent dispute with the Centers for Disease Control over Truvada and Descovy. The government sued Gilead for patent infringement this year after Gilead refused to recognize CDC patents on the use of the drugs for prevention, a use that the government says was invented at CDC labs in Atlanta.

The activists shared Wednesday’s petition with members of Congress who have expressed anger about high drug prices, especially for drugs developed with taxpayer money.

“This is an example of monopoly abuse,’’ said Rep. Lloyd Doggett (D-Tex.), who has introduced amendments to require government negotiation of prices for drugs developed with taxpayer money.

Pharmaceutical patent extensions are granted by the Patent and Trademark Office based on the length of time the FDA takes to review and approve a drug. Third-party objections such as PrEP4All’s are not allowed in such reviews except in “extraordinary’’ situations, according to the agency’s rules. PrEP4All argues that Gilead’s maneuvers in this case rise to the level of extraordinary. The Patent and Trademark Office declined to comment on the petition.