An antibiotic of last resort, running out of road

Vancomycin has served for more than 60 years as one of medicine's most important reserve antibiotics — a drug doctors turn to specifically when infections have already outmaneuvered other treatments. That reserve status is exactly what makes its declining effectiveness so alarming. As bacteria continue evolving resistance mechanisms, drugs that once worked reliably are losing their power, turning routine surgeries, cancer treatments, and even ordinary infections into considerably higher-stakes medical situations than they were a generation ago. Antibiotic resistance broadly is linked to an estimated 4.7 million deaths worldwide in 2019 alone, a scale that underscores why restoring even one already-approved drug's effectiveness carries real, immediate value.

A new study, published in Nature Communications on June 16, 2026, describes exactly that kind of restoration. Researchers from the Moses laboratory at Cold Spring Harbor Laboratory, working with Professor Howard Hang's team at Scripps Research, found a way to make vancomycin effective again against vancomycin-resistant Enterococcus faecium, commonly abbreviated VREfm — a hospital-acquired infection that has become increasingly common and increasingly difficult to treat as resistance has spread.

Targeting the bacteria's own defense mechanism, not building a new drug

The strategy behind this research reflects a specific and, in some ways, more efficient approach to fighting antibiotic resistance than the traditional path of discovering an entirely new antibiotic compound from scratch. Rather than searching for a novel drug, the research team focused on a bacterial enzyme called secreted antigen A, or SagA, which plays a role in helping resistant bacteria evade vancomycin's effects. The team's approach was to disable that specific enzyme using a small molecule, effectively stripping the bacteria of one of the key defenses that had allowed it to shrug off vancomycin in the first place.

The molecule responsible, called pghi-4, wasn't originally developed with this application in mind at all. It was first synthesized in the Moses laboratory back in 2020, arising from what the researchers describe as fundamental chemical research rather than a targeted antibiotic-discovery program. Sean Moses, describing the origins of the discovery, was direct about its unplanned trajectory: "This discovery came from fundamental chemical research. Reaction development led to the discovery of the first inhibitor of an important enzyme involved in antibiotic resistance." That's a notable detail — a compound developed for entirely different chemistry research purposes turned out, years later, to have a direct and significant medical application nobody had specifically been searching for when the molecule was first created.

How researchers found the compound, and confirmed what it was actually doing

Establishing that SagA specifically was the right target required a careful process of elimination. Researchers first tested what happened when SagA was deleted from resistant bacteria entirely, and found that removing the enzyme had little impact on the bacteria's resistance to other antibiotics tested, including ampicillin, daptomycin, and ceftriaxone. That result was scientifically important precisely because of what it ruled out: if deleting SagA had broadly weakened the bacteria's overall fitness or resistance across the board, it would have been unclear whether any subsequent vancomycin-specific effect reflected a targeted mechanism or simply a generally frailer organism. Instead, the selective pattern — no broad resistance change, but a specific effect on vancomycin susceptibility — indicated that SagA was doing something precise: protecting specifically the site where vancomycin binds to the bacterial cell wall.

With that specific target confirmed, the research team screened a large chemical library searching for compounds capable of chemically disabling SagA, ultimately identifying a class of molecules called β-chloroalkenyl sulfonyl fluorides. Their lead compound within that class, pghi-4, produced results that held up not just in a single laboratory test, but across multiple clinical bacterial isolates — samples drawn from real infections rather than a single standardized lab strain — which considerably strengthens confidence that the effect isn't an artifact specific to one particular bacterial sample.

The numbers behind the restored effectiveness

The core measurable result from this research is striking in its specificity: when drug-resistant E. faecium was treated with both vancomycin and pghi-4 together, the antibiotic's ability to kill the bacteria was restored, reducing the amount of vancomycin needed to achieve that effect by up to eightfold compared to using vancomycin alone against the same resistant strain. That's a substantial reduction in required dosage, with real practical implications — a considerably lower effective dose can mean fewer side effects for patients and a treatment that remains viable against bacteria that would otherwise require doses so high they'd become clinically impractical or unsafe.

Beyond laboratory cell cultures, the combination also demonstrated effectiveness in a mouse model of sepsis, with the treatment reducing bacterial burden in infected animals. That's a meaningful additional validation step — a compound that works cleanly against bacteria in a petri dish doesn't always translate into effective treatment within a living organism, where factors like drug distribution, immune system interaction, and metabolism can all complicate results considerably. Demonstrating reduced bacterial burden in an actual infected animal model gives this research a stronger foundation than in vitro results alone would provide.

Why this specific enzyme family mattered so much to hit

Howard Hang, whose Scripps team collaborated on identifying and testing pghi-4, emphasized the broader significance of successfully targeting SagA in the first place: "To demonstrate you can pharmacologically target this enzyme family is a big step forward." SagA belongs to a larger family of cell-wall-remodeling enzymes known as NlpC/P60 peptidoglycan hydrolases — enzymes that, according to the research team, no drug had ever successfully targeted before this study. That distinction matters because it opens an entirely new category of pharmacological intervention against bacterial resistance mechanisms, rather than representing an incremental improvement on an already well-explored drug target.

Hang described the approach as part of a broader and increasingly important category of treatments known as antibiotic adjuvants — compounds that aren't antibiotics in their own right, but that work by helping existing antibiotics function more effectively against bacteria that have otherwise learned to resist them. That's a meaningfully different treatment philosophy than the traditional model of continuously developing new antibiotic compounds to stay ahead of evolving resistance, a race that has become increasingly difficult and expensive to sustain as fewer genuinely new antibiotic classes have been discovered in recent decades.

A resistance mechanism that may make some bacteria more vulnerable, not less

One of the more counterintuitive findings buried in this research involves how the specific resistance mechanism that makes VREfm dangerous might actually create a corresponding vulnerability to this new approach. The study's data suggests pghi-4 and related compounds may be capable of targeting other peptidoglycan-remodeling enzymes beyond SagA specifically — and because VREfm strains tend to carry extra copies of SagA-like enzymes as part of what makes them resistant in the first place, that same genetic trait could make these particular resistant strains more vulnerable to this treatment approach, rather than less.

That's a genuinely encouraging wrinkle for a treatment strategy specifically designed to counter resistance: rather than simply neutralizing one specific defense mechanism while leaving bacteria free to develop entirely new resistance pathways elsewhere, this approach may be exploiting a structural feature that's actually more pronounced in the most resistant bacterial strains — the ones doctors most urgently need better treatment options against.

What comes next, and how far this approach could extend

The Cold Spring Harbor and Scripps research teams aren't treating pghi-4 as a finished product — they're already developing more potent second-generation derivatives designed to couple directly with vancomycin itself, rather than requiring separate co-administration of two distinct compounds. That kind of chemical integration, if successful, could simplify eventual clinical use considerably, turning what's currently a two-part treatment strategy into something closer to a single, modified antibiotic compound.

Hang framed the broader implication of this work in terms that extend well beyond VREfm specifically: the researchers believe the same underlying strategy could eventually be extended to other combinations of resistant bacteria and antibiotics, including notoriously difficult pathogens like tuberculosis and drug-resistant Staphylococcus aureus. That's a considerably larger potential application than this single study's specific results demonstrate on their own — VREfm served as the initial proof-of-concept target, but the broader lesson researchers are drawing is that targeting basic, shared aspects of bacterial physiology, rather than chasing resistance mechanisms one drug and one pathogen at a time, may offer a more durable long-term strategy for staying ahead of bacterial evolution. Whether that broader extension proves successful across additional pathogens remains a question for future research, but this study's results give the underlying approach a genuine, validated starting point to build from.

*This article was researched using publicly available reporting from Nature Communications, Cold Spring Harbor Laboratory, Scripps Research, EurekAlert, ScienceDaily, Mirage News, and News-Medical's coverage of the peer-reviewed study led by researchers at the Moses laboratory and Professor Howard Hang's team. It is intended for informational purposes and is not medical advice.*