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A breakthrough moment: Researchers discover new class of antibiotics

The last time a new class of antibiotics reached the market was nearly three decades ago—but that could soon change, thanks to a discovery by researchers at McMaster University.

A team led by researcher Gerry Wright has identified a strong candidate to challenge even some of the most drug-resistant bacteria on the planet: a new molecule called lariocidin. The findings were in the journal Nature on March 26, 2025.

The discovery of the all-new class of antibiotics responds to a critical need for new antimicrobial medicines, as bacteria and other microorganisms evolve new ways to withstand existing drugs. This phenomenon is called antimicrobial resistance—or AMR—and it's one of the top global public health threats, according to the World Health Organization.

"Our old drugs are becoming less and less effective as bacteria become more and more resistant to them," explains Wright, a professor in McMaster's Department of Biochemistry and Biomedical Sciences and a researcher at the university's Michael G. DeGroote Institute for Infectious Disease Research. "About 4.5 million people die every year due to antibiotic-resistant infections, and it's only getting worse."

Wright and his team found that the new molecule, a lasso peptide, holds great promise as an early drug lead because it attacks bacteria in a way that's different from other antibiotics. Lariocidin binds directly to a bacterium's protein synthesis machinery in a completely new way, inhibiting its ability to grow and survive.

"This is a new molecule with a new mode of action," Wright says. "It's a big leap forward for us."

Lariocidin is produced by a type of bacteria called Paenibacillus, which the researchers retrieved from a soil sample collected from a Hamilton backyard.

The research team allowed the soil bacteria to grow in the lab for approximately one year—a method that helped reveal even the slow-growing species that could have otherwise been missed. One of these bacteria, Paenibacillus, was producing a new substance that had strong activity against other bacteria, including those typically resistant to antibiotics.

"When we figured out how this new molecule kills other bacteria, it was a breakthrough moment," says Manoj Jangra, a postdoctoral fellow in Wright's lab.

In addition to its unique mode of action and its activity against otherwise drug-resistant bacteria, the researchers are optimistic about lariocidin because it ticks a lot of the right boxes: it's not toxic to human cells, it's not susceptible to existing mechanisms of antibiotic resistance, and it also works well in an animal model of infection.

Wright and his team are now laser-focused on finding ways to modify the molecule and produce it in quantities large enough to allow for clinical development. Wright says because this new molecule is produced by bacteria—and "bacteria aren't interested in making new drugs for us"—much time and resources are needed before lariocidin is ready for market.

"The initial discovery—the big a-ha! moment—was astounding for us, but now the real hard work begins," Wright says. "We're now working on ripping this molecule apart and putting it back together again to make it a better drug candidate."