Scientists may be on the cusp of curing AIDS.

Researchers at the Wistar Institute in Philadelphia are running the largest randomized clinical trial for an AIDS therapy in the world. The drug they’re testing has shown the potential to reduce the level of HIV in a patient’s blood. That’s the first step toward a cure.

Treatments like this one were unimaginable just a few years ago. Since then, HIV/AIDS has transformed from a death sentence to, in many cases, a manageable chronic disease.

For that transformation, we can thank animal research, the indispensable foundation of most medical and scientific studies. And yet many animal-rights advocates continue to push for prohibition of animal models in biomedical research.

The facts are not on their side.

As recently as 1995, HIV/AIDS was the leading cause of death for Americans ages 25-44. That year, AIDS killed more than 49,500 people around the country. Two decades later, annual deaths from the disease have dropped nearly three-quarters, to 13,700.

More impressive, 20-year-old Americans diagnosed with HIV/AIDS today can, with treatment, expect to reach their early 70s. That’s just a few years shy of the average life expectancy for the general population. Thanks to medication, mothers with HIV can now give birth to HIV-free babies.

These recent advances are almost entirely due to highly effective antiretroviral drugs designed to prevent the virus from multiplying. The research that paved the way for these powerful treatments would have been impossible without research in nonhuman primates.

In the early days of the epidemic, scientists discovered the Simian Immunodeficiency Virus in monkeys. Studying infected macaque monkeys helped scientists understand how HIV/AIDS worked in humans. These monkeys also received some of the first promising antiretroviral drugs.

The first approved AIDS drug was the direct result of early experiments with mice. Known as AZT, the antiretroviral was first shown to suppress mouse retroviral disease in 1986.

Primate models also played a valuable role in the creation of Saquinavir, the first HIV protease inhibitor — a medicine that attacks the virus’ ability to replicate. Before clinical trials began, animal tests demonstrated the drug to be safe for humans.

Today, protease inhibitors are an essential part of the drug cocktails that extend the lives of HIV/AIDS patients around the world.

Despite these achievements, many animal-rights advocates continue to oppose primate models in HIV/AIDS research. They claim that techniques like computer modeling and population studies can replace animal research.

In reality, there is no substitute for primate studies. To ensure that medicines are safe and effective, scientists must study them in living systems that closely resemble those in humans. Abandoning animal testing would halt today’s most promising lines of inquiry.

Consider the ongoing search for an AIDS vaccine, which relies heavily on primate studies.

In 2013, researchers at Oregon Health and Science University successfully tested an experimental vaccine for SIV, the version of HIV that affects monkeys. After administering the vaccine, the researchers exposed the monkeys to a highly potent form of SIV. Half of the monkeys never contracted the virus. Over time, those that did were able to fight off the virus entirely.

This discovery, which could conceivably lead to the eradication of HIV/AIDS, wouldn’t have happened without the use of primates.

In sub-Saharan Africa, more than 1 million people die of AIDS each year. Ending — or restricting — primate studies and other forms of animal research will only delay the eradication of this deadly global disease.

Frankie L. Trull is president of the Foundation for Biomedical Research.