Phase 2 Trial Data Show That Novel Antibiotic Led to 96% Cure Rate for C diff Infection


Iberzaplstat was non-inferior to standard of care vancomycin, was safe and tolerable, and will advance into a phase 3 trial.

In a recent phase 2 trial, approximately 96% of patients with Clostridioides difficile (C diff) infection (CDI) who received antibiotic iberzaplstat (Acrux Pharmaceuticals) experienced clinical cure, according to a press release. Iberzaplstat demonstrated non-inferiority to vancomycin (Vancocin; Pfizer)—a standard of care antibiotic used to treat CDI—which had a cure rate of approximately 81%, according to a previous assessment.

Image credit: Jo Panuwat D |

Image credit: Jo Panuwat D |

“Since there is only one other antibiotic besides vancomycin approved for treatment of this serious disease, there is a clear need for more first-line therapeutic agents in our armamentarium,” said Stuart Johnson, MD, a professor of medicine at Loyola University and Acurx Scientific Advisory Board member, in the press release.

C diff is a primary cause of health care-associated infections in hospitals; in the United States, approximately 500,000 people will be diagnosed annually. Certain antibiotics, such as vancomycin, are an approved first line treatment for CDI, however up to 40% of patients treated with antibiotics will experience recurrence.

Investigators conducted the 2-part phase 2 trial to evaluate the clinical efficacy of iberzaplstat in treating CDI. The phase 2a segment of the trial consisted of a multicenter, open-label, and single-arm study that evaluated ibezapolstat at 450 mg twice daily for 10 days in 10 patients with diarrhea as a symptom of CDI.

The results of the study showed high efficacy for the medication—all 10 patients were 100% cured at the trial’s end. In addition, no patients experienced recurrence in the 28 days following treatment, and the trial was concluded because of this success. Additionally, data showed ibezapolstat was safe and tolerable, with only 3 patients experiencing mild gastrointestinal-related adverse events (AEs) which resolved without treatment.

The phase 2b segment was a double-blind, randomized, active-controlled, and non-inferiority trial comparing a 10-day regimen of iberzaplstat at 450 mg taken every 12 hours to vancomycin at 125 mg taken every 6 hours. Iberzapolstat showed non-inferiority based on appearance, dosing times, and number of capsules administered.

According to the study investigators, there will be more analyses to come that will look at pharmacokinetics and microbiome changes. Moreover, investigators will evaluate changes inbacterial diversity and abundance during and after therapy, studying the levels of healthy gut microbiota like Actinobacteria and Firmicute phylum species.

“Our previous data showed that ibezapolstat unexpectedly spares other Firmicutes along with the important Actinobacteria phylum necessary for maintaining a healthy microbiome,” saidinvestigator Kevin Garey, PharmD, MS, professor and chair, University of Houston College of Pharmacy and Acurx Scientific Advisory Board member in the press release. “These characteristics… suggest that ibezapolstat may reduce the likelihood of CDI recurrence."

The US Centers for Disease Control and Prevention designated November as C diff Awareness Month, and treatments like ibeszapolstat could offer more treatment options to patients. Currently, phase 3 trials are planned for next year.

“These ibezapolstat observed clinical cure rate results are impressive for an investigational antibiotic in a phase 2 trial for CDI,” said executive Acurx chairman Robert J. DeLuccia in the press release. “They greatly enhance our scientific evidence base and, in our view, provide robust support for an anticipated End-of-Phase 2 FDA Meeting…with advancement into Phase 3 clinical trials.”


Acurx Announces Positive Top-Line Ibezapolstat Phase 2 Efficacy Results with 96% Clinical Cure Rate in Patients with C. difficile Infection. Acurx Pharmaceuticals. News Release. November 2, 2023. Accessed on November 20, 2023.

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