Nikhil Prasad Fact checked by:Thailand Medical News Team Jun 26, 2026 1 hour, 12 minutes ago
Medical News: Researchers Discover Potent Antiviral Effects in Laboratory and Animal Studies
Scientists have identified an old antifolate drug called aminopterin as a promising new candidate in the fight against Mpox, formerly known as monkeypox. The drug, originally developed decades ago for cancer treatment, was found to dramatically reduce monkeypox virus replication in laboratory experiments while also easing virus-related inflammation in infected animals. The findings could pave the way for a new treatment option at a time when effective therapies for Mpox remain limited.
Researchers found that the decades-old drug aminopterin sharply reduced Mpox virus replication and inflammation
in both laboratory and animal studies
The research was conducted by scientists from the Interdisciplinary Eye Research Institute (EYE-X Institute), Bengbu Medical University, the Key Laboratory of Infection and Immunity of Anhui Higher Education Institutes, Bengbu Medical University, the School of Public Health at Fujian Medical University, the Institute for Hepatology, National Clinical Research Center for Infectious Diseases at Shenzhen Third People's Hospital, and the Medical School of Nanjing University, all in China.
Why Better Mpox Treatments Are Needed
Mpox has spread to more than 100 countries in recent years, infecting tens of thousands of people worldwide. Although many patients recover without major complications, the virus can cause severe illness in vulnerable individuals, particularly those with weakened immune systems.
Current treatment options are limited. Existing antiviral drugs were originally developed for smallpox and have shown mixed success against Mpox, highlighting the need for additional therapies that work through different biological mechanisms.
Aminopterin Stands Out from Similar Drugs
The researchers tested four drugs belonging to the antifolate family. Surprisingly, only aminopterin showed powerful antiviral activity against the monkeypox virus. Other related medications, including methotrexate, pemetrexed, and LSN3213218, failed to significantly slow viral growth.
In laboratory-grown monkey kidney cells and human skin fibroblast cells, aminopterin reduced viral replication at extremely low concentrations while showing relatively little toxicity to healthy cells. This high selectivity suggests the drug can target infected cells effectively without causing excessive damage to normal tissues.
This
Medical News report highlights that the researchers found aminopterin not only lowered the amount of virus present but also protected infected cells from the destructive effects normally caused by viral infection.
How the Drug Stops the Virus
Further experiments revealed that aminopterin works during the earliest stages of infection. The drug partially blocked the virus from attaching to cells and produced an even stronger effect by preventing the virus from replicating after entering the cells.
The investigators estimated that aminopterin reduced viral attachment by about 20 percent while suppressing viral replication by approximately 70 percent. This combination significantly reduced the production of new virus particles.
Scientists believe the drug may interfere with the virus through mechanisms beyond its traditional role of blocking folate metabolism, suggesting previously unknown antiviral properties that deserve further investigation.
Encouraging Results in Animal Studies
The team also evaluated aminopterin in Spanish dormice, an animal species that naturally develops Mpox infection similar to humans.
Untreated infected animals became lethargic, lost weight, developed enlarged spleens, and suffered extensive lung damage marked by inflammation, bleeding, and destruction of normal lung structure.
Animals receiving aminopterin recovered more quickly. Many regained weight, showed improved activity levels, had smaller spleens, and maintained healthier lung tissue with far less inflammation.
Researchers also found substantially lower amounts of viral DNA in the lungs, spleen, liver, kidneys, and intestines of treated animals, indicating that the drug reduced the spread of infection throughout the body.
Reduced Harmful Inflammation
Beyond lowering viral levels, aminopterin also decreased several inflammatory molecules that are known to contribute to severe illness, including IL-1β, IL-6, TNF-α, and IFN-γ.
This dual action may prove especially valuable because severe viral infections often cause excessive inflammation that damages healthy tissues. By reducing both viral replication and inflammatory responses, aminopterin could potentially lessen disease severity through two complementary mechanisms.
Conclusion
Although the findings are highly encouraging, the researchers caution that much more work remains before aminopterin could become a treatment for people with Mpox. The experiments involved only one viral strain and one animal model, while the drug is also known to carry significant toxicity at higher doses. Future studies must determine safer dosing strategies, evaluate additional virus strains, clarify exactly how the drug blocks infection, and ultimately confirm its safety and effectiveness in human clinical trials. Even so, the discovery identifies aminopterin as a promising new antiviral candidate with a unique dual ability to suppress both viral replication and harmful inflammation, making it one of the more intriguing potential additions to the limited arsenal against Mpox.
The study findings were published in the peer reviewed journal: Microbiology Spectrum.
https://journals.asm.org/doi/10.1128/spectrum.01581-25
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Medical News.
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https://www.thailandmedical.news/articles/monkeypox
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