The Thai Network of People Living with HIV/AIDS (TNP+), a member of the Make Medicines Affordable network, has filed a patent opposition relating to MK-8527, an investigational HIV prevention medicine. The opposition was filed on May 11, 2026 with the Department of Intellectual Property against Thai patent application no. 1601005648, filed by Merck & Co.
Merck’s investigational drug MK-8527 is being researched for HIV PrEP, with preclinical data showing the drug is an “attractive clinical candidate.” It is currently in clinical trials for once-monthly oral HIV-1 pre-exposure prophylaxis. MK-8527 is a nucleoside reverse transcriptase translocation inhibitor, which is a new class of HIV drugs currently under investigation.
Current HIV PrEP options include daily oral pills or two options for long-acting injections (cabotegravir or lenacapavir). MK-8527 could offer an alternative as a monthly pill, which could address challenges around PrEP delivery and adherence, such as stigma.
“MK-8527 could become an additional PrEP option that allows people to choose HIV prevention methods that better fit their lifestyles and different social, personal, and public health needs. Expanding prevention choices is important for addressing the HIV epidemic effectively,” stated Yupha Sukreung, Chairperson of TNP+. “Access to new HIV prevention technologies should not depend on where people live or how much they can afford to pay. Communities around the world are calling for affordable access to MK-8527 and opposing unmerited patent monopolies that could restrict future access.”
Application lacks novelty and inventive step; concerns with application amendments
Chalermsak Kittitrakul, Project Manager for Access to Medicines at TNP+, said that Merck & Co.’s attempts to patent MK-8527 is a practice of evergreening, whereby companies seek additional patent monopolies through minor modifications of existing compounds and technologies. “The repeated expansion of claims in this case further demonstrates attempts to broaden exclusivity beyond the original filing,” Kittitrakul, stated.
TNP+ argues that the application lacks novelty and an ‘inventive step’ which are requiredis required for an IP patent application, as several important elements claimed in the application had already been disclosed in earlier patents and scientific publications. The organization argues that minor modifications of existing compounds should not justify new patents that could unnecessarily prolong market monopolies. TNP+ also challenged certain claims relating to the use of the compounds for treatment or prevention of HIV, arguing that such claims may extend into areas that should not be monopolized under Thai patent law.
“If granted, such patents could negatively affect future competition and access to affordable medicines. Thailand’s patent system should not allow unnecessary extensions of medicine monopolies,” Kittitrakul said.
TNP+ raised concerns regarding multiple amendments made to the patent application during prosecution in Thailand. The opposition states that the application originally contained 24 claims when filed in Thailand in 2016, which was later expanded to 41 claims at the time of publication and subsequently increased to 59 claims through voluntary amendments filed after publication. The repeated expansion of claims “raises concerns that the scope of the patent monopoly could become broader than the original application,” the organization stated, adding that allowing broad amendments after publication could undermine legal certainty and make it more difficult for the public and third parties to assess and challenge the scope of patent claims effectively. The organization further noted that the amended claims appear to reflect claims pursued in related international patent application beyond those originally referenced at the time of filing. According to TNP+, this raises concerns regarding the clarity, consistency, and scope of the claims under examination in Thailand.
Calls grow for the rejection of unmerited patent applications on HIV prevention technologies
TNP+’s challenge against MK-8527 patent applications is the latest in ongoing and growing oppositions from civil society groups globally to oppose unmerited patent applications in order to prevent unnecessary monopolies on medicines that are important for public health. In late 2025, Make Medicines Affordable partner Fundación Ifarma filed a patent opposition in Colombia in relation to MK-8527.