The investigational once-monthly oral preexposure prophylaxis (PrEP) drug alimatravir could be manufactured for as little as $3 per person per year, according to an analysis presented July 28 at the annual meeting of AIDS 2025 in Rio de Janeiro.

Yet Merck’s preliminary access plan does not extend its voluntary licenses to all low- and middle-income countries with substantial or rising HIV incidence — including several countries participating in phase 3 trials — and the company has not committed to the $3 annual price estimated in the analysis, Samuel Cross, MD, a physician researcher at Christchurch Hospital in Te Whatu Ora, New Zealand, told attendees.

Merck signed seven voluntary licensing agreements in July with generic manufacturers to prepare production in 129 low- and middle-income countries. That current access plan leaves out low- and middle-income countries across the world that have an estimated 230,000 new HIV acquisitions a year, including seven countries in Latin America whose estimated 112,000 new HIV acquisitions per year make up 80% of HIV incidence in that region.

Four of the countries excluded are among the 17 where the EXPrESSIVE phase 3 trials assessing alimatravir are taking place with approximately $180 million in funding from the Gates Foundation. Brazil has an estimated 55,000 new HIV infections a year, Colombia has 13,000, Peru has 6500, and Argentina has 5000.

Increased Access Linked to Reduced HIV Acquisitions

While the African countries included in Merck’s access plan have seen a 55% drop in HIV acquisitions from 2010 to 2024, the Latin American countries excluded from the plan have seen a 12% increase. Cross also noted that wealthier countries, such as the Bahamas, Barbados, and Seychelles, were included in the agreement, whereas lower income ones such as Argentina, Mexico, and Brazil were left out.

“Alimatravir for $3 a year could be the cheapest HIV prevention drug the world has ever seen worldwide, but it needs to be $3 everywhere, not just some places,” Cross said.

Joseph Cherabie, MD, MSc, FIDSA, senior medical director of clinical research and special programs at Howard Brown Health in Chicago, told Medscape Medical News he found the modeling study interesting.

“Decreasing the cost of the drug and increasing the availability of generic options, especially globally, would of course increase access and decrease HIV acquisition in vulnerable populations, and a once-a-month drug is appealing to many,” said Cherabie, who was not involved in the study.

Low Cost to Increase Access

Cross explained that PrEP needs to be given to tens of millions of people to have a significant effect on the HIV epidemic. With only an estimated 2.3 million people taking PrEP globally right now, “this is having little to no effect on the epidemic, especially in lower-middle-income countries,” he said. If PrEP use remains at current levels, HIV incidence will rise worldwide, with an estimate 1.45 million infections per year by the year 2030, according to UNAIDS.

For mass treatment to be affordable, PrEP needs to be available at a very low cost, he said. Currently, oral tenofovir disoproxil fumarate and emtricitabine (TDF/FTC) costs an estimated $40 a year, the dapivirine vaginal ring fell from $156 in 2025 to $71 in 2026, cabotegravir is about $160 per year, and lenacapavir is projected to cost about $100 a year. While all of these cost less than they did at initial market — particularly the injectable long-acting PrEP that initially cost over $20,000 per person per year — the costs “still are not cheap enough to use en masse,” Cross said. “So how cheap is cheap?”

He noted the costs of 10 generic common medications in the UK National Health Services that all cost less than $1, including atorvastatin, sertraline, warfarin, amoxicillin, and metformin. With the nucleoside reverse transcriptase translocation inhibitor alimatravir, formerly MK-8527, currently in phase 3 trials and close to potential regulatory approval, Cross’s team set out to determine how cheaply the molecule could be produced.

At a dose of 11 mg/mo, a year’s dosage is 132 mg, substantially less than TDF/FTC’s 500 mg/d. He noted that the cost of 12 tablets of TDF/FTC — the number that would be needed of alimatravir — is $1.31 through the Clinton Health Access Initiative, and other oral PrEP drugs similarly ranged from $1.15 to $1.70 for 12 tablets. “So that’s the ballpark we’re thinking of,” Cross said.

The researchers searched the Trade Vision LLC database from January 2020 to December 2025 for records of exports to India of alimatravir’s active pharmaceutical ingredient. They calculated a weighted average of this ingredient per kg, combined it with the dosing assumption of 11 mg/mo, and estimated drug production costs that covered formulation, loss of the ingredient in production, packaging, transportation and tariffs, profit margin, and taxation.

The cost of the active ingredient based on two shipments of the drug from Merck to a lab in India was $9138/kg during early production phase. That set the initial cost of just the active pharmaceutical ingredient at $1.21 per person per year. They added the cost of formulation ($0.01), packaging ($0.10), and excipients and 5% loss of the ingredient ($0.28) and then added 21% to account for transportation, tariffs and labor, which came to $1.80 per person per year. Adding in profit at 30% and taxation at 27%, the cost came to $2.49 per person per year, which rounds up to about $3 per person per year.

That calculation is based on alimatravir’s current cost, which is more than 17 times higher than other antiretrovirals, so the cost has the potential to fall by 90% after increased economies of scale, Cross said. “Once these drugs hit the market, the API price comes down dramatically,” he said.

He added that the methodology his team used has previously correctly predicted the production cost for drugs for HIV, hepatitis B and C, tuberculosis, and cancer, among other conditions.

Generic Mass Production Needed

Limitations of the study include lack of current information on alimatravir’s efficacy and adherence in the trials, whose design differs from the PURPOSE trials that assessed lenacapavir and could result in sub-optimal adherence.

In addition, lowering the cost of the drug to $3/y will require coordination of generic mass production, procurement, and supply.

“We need to consider robust long-term financing, reliable forecasts by demand of demand by country for procurement, integration with HIV testing and treat programs, simple delivery and adherence support, as well as support and care for key populations at highest risk of HIV,” Cross said.

To achieve what Cross proposes, Cherabie said generic production and licensing approval are both necessary.

“These agreements already exist for many drugs that are used to treat HIV and often go into effect if there is a need for the drug or if the drug has been present for a while,” Cherabie said. “The major barrier to this, though, is drug company pricing and their choice to enforce patents, so if a drug company decides it wants to increase access, this is the path they take, but they are the ultimate decider.”

Though Cherabie noted that efficacy data for alimatravir is still to come, cost is going to be the leading barrier to access in the US, and that will be amplified globally.

“If drug companies truly want to end the HIV epidemic, then they can bring down the costs of these drugs,” Cherabie said. “That having been said, if they can at least guarantee access to trial participants post conclusion of the trials, that would be a welcome step.”

The research was funded by the International Treatment Preparedness Coalition and UNITAID. One coauthor reported receiving research support and/or speaking, travel, or advisory board fees from Roche, Gilead Sciences, ViiV Healthcare, Merck, Adcock Ingram, and Johnson & Johnson. Cherabie reported having no disclosures.

Tara Haelle has covered science and medicine for nearly two decades and is author of Vaccination Investigation and The Informed Parent: A Science-Based Resource for Your Child’s First Four Years. She is based in Dallas.