Acurx Announces Presentation of a Scientific Poster at the Premier International C. difficile Symposium (ICDS) Demonstrating Superior In Vitro Kill Kinetics of Ibezapolstat vs. Vancomycin and Fidaxomicin (Standards of Care) in Clostridioides difficile and Vancomycin-Resistant Enterococcus Co-Cultures
- The microbiome of patients experiencing recurrent CDI is frequently dominated by overgrowths of Enterococcus species
- This study evaluated the in vitro bactericidal and molecular efficacy of ibezapolstat (IBZ), vancomycin (VAN), and fidaxomicin (FDX) against C. difficile and Enterococcus in standalone and complex co-culture environments
- These findings demonstrate that Enterococcus creates a protective microenvironment that actively impairs C. difficile killing using standard of care antibiotic regimens
- IBZ maintained superior bactericidal activity under co-culture conditions, including further decreasing Clostridioides difficile toxin B (TcdB) expression while simultaneously eradicating vancomycin-resistant bacterial overgrowth
- Acurx has previously been granted FDA QIDP and Fast-Track Designation and has received SME (Small and Medium-sized Enterprise) designation by the EMA
STATEN ISLAND, N.Y., Sept. 14, 2026 /PRNewswire/ -- Acurx Pharmaceuticals, Inc. (NASDAQ: ACXP) a late clinical stage biopharmaceutical company developing a new class of antibiotics for difficult-to-treat bacterial infections, announced today that a scientific poster entitled: Comparative In Vitro Killing Kinetics of Ibezapolstat and Comparator Antibiotics in Clostridioides difficile and Vancomycin-resistant Enterococcus Co-Cultures was presented at the 9th International C. difficile Symposium held in Bled, Slovenia from September 8-10, 2026. The poster was presented by Dr. Eugenie Bassères, Research Scientist, University of Houston College of Pharmacy.
All vancomycin-resistant Enterococcus (VRE) strains demonstrated high-level resistance to VAN (MIC >128 μg/mL), whereas IBZ and FDX exhibited equivalent lower susceptibility thresholds (MIC range: 2–16 μg/mL). In monoculture, IBZ displayed potent bactericidal activity against C. difficile non-inferior to FDX (p ≥ 0.2381). Enterococcus co-culture with C. difficile created severe microbial interference that impaired C. difficile killing across all antibiotic arms, decreasing killing by up to 2.90 logs; however, IBZ maintained the highest residual anti-C. difficile performance (5.51-log reduction), significantly outperforming VAN (p = 0.0112). Conversely, C. difficile presence exerted negligible interference on VRE killing, where IBZ and FDX maintained robust anti-VRE killing while VAN remained inactive. At the transcriptional level, all treatments significantly suppressed TcdB gene abundance compared to the experimental laboratory control while IBZ showed statistically significant superiority over the other two antibiotics in decreasing the VanA cluster (ibezapolstat, vancomycin and fidaxomicin)
The study was performed at the University of Houston laboratory of Kevin Garey, PharmD, MS, FIDSA, Professor and Chair, University of Houston College of Pharmacy, and Principal Investigator for microbiology and microbiome aspects of the ibezapolstat clinical trial program. Commenting on the significance of the results of the study, Dr. Garey stated: "These new data add to the growing body of evidence supporting ibezapolstat's unique antibacterial pharmacology to kill C. difficile while preserving the microbiome. Prior studies have shown that Enterococcus increases the severity of C. difficile infection. This study adds in vitro evidence that ibezapolstat doesn't cause overgrowth of vancomycin-resistant Enterococcus and also maintains killing efficacy against C. difficile strains."
Robert J. DeLuccia, Executive Chairman of Acurx, stated: "If these results are validated in our Phase 3 registration program, and ultimately in clinical practice, for the treatment of patients with CDI, ibezapolstat's activity has the potential to reduce the nosocomial emergence of the critical pathogen VRE while treating CDI." He further stated: "Adding to the totality of data on ibezapolstat from studies such as this increase our confidence in a successful outcome of our clinical trial program and continue to elevate our favorable product profile and attractive value proposition, including in-market competitive advantage compared to vancomycin and fidaxomicin, the current standards of care for acute CDI, particularly for the reduction of recurrence".
The poster is available on Acurx Pharmaceuticals' website: www.acurxpharma.com
Acurx previously reported the successful outcome of a Type C Meeting conducted with FDA on July 13, 2026 to discuss ibezapolstat's Phase 3 clinical program and scope of its planned NDA. The Agency stated that it is open to further discussion at a Pre-NDA Meeting regarding the possibility of submitting an NDA with only a single Phase 3 trial, depending on the totality of the clinical data plus any other supportive data that Acurx may generate by that milestone. The Agency noted that determination of acceptability of one Phase 3 clinical trial for an NDA is made on a case-by-case basis, taking into consideration such factors as the magnitude, consistency, and overall robustness of the efficacy results; generalizability of the results to the US population; relevance of the results to US patient care and clinical practice guidelines; Phase 2 data; and an adequate safety database. The Agency acknowledged Acurx's planned clinical trial in recurrent CDI (rCDI) and noted the data from this rCDI trial, if successful, will support an NDA submission. If the IBZ-ASPIRE trial does not meet these criteria, then a second trial consistent with the agreement reached at the end of Phase 2 (EOP2) meeting on April 27, 2024 is recommended.
The currently planned IBZ-ASPIRE trial is of non-inferiority design with the primary efficacy analysis in the Modified Intent-To-Treat (mITT) population. This will result in approximately 550 subjects in the mITT population, randomized in a 1:1 ratio to either ibezapolstat or standard-of-care vancomycin. The Agency also agreed with the overall trial design and evaluation criteria and further agreed that the trial testing criteria, if successful, could support indications for both the acute treatment and the reduction of recurrence of CDI. In the event non-inferiority of ibezapolstat to vancomycin for Clinical Cure of CDI is demonstrated, further analyses will be conducted to test for superiority for reduction of recurrence and for clinical cure of CDI.
Acurx also previously announced that it is conducting a new clinical trial (IBZ-PATHFINDER) in patients with multiply recurrent C. difficile Infection (rCDI) while its program in the broader CDI patient population is ready to advance to Phase 3 international clinical trials (IBZ-ASPIRE), subject to receiving appropriate funding. This new IBZ-PATHFINDER clinical trial in rCDI involves an open-label pilot trial to gain experience with IBZ in patients with multiply-recurrent CDI with at least 3 episodes of CDI within the past 12 months.
About the International C. difficile Symposium (ICDS)
The International C. difficile Symposium (ICDS) is established as the premier venue for the review of Clostridium difficile research. The first meeting was held in Kranjska Gora in 2004, the 2nd in Maribor in 2007, while all earlier meetings were in Bled in 2010, 2012, 2015 and in 2018. ICDS in 2020 was held virtually. The 2026 meeting will provide a forum for the C. difficile community to exchange knowledge across disciplines, from epidemiology and diagnostics to clinical trials and basic research, fostering innovative approaches to understanding pathogenesis and improving disease control.
About the Ibezapolstat Phase 2 Clinical Trial
The completed multicenter, open-label single-arm segment (Phase 2a) study was followed by a double-blind, randomized, active-controlled, non-inferiority, segment (Phase 2b) at 28 US clinical trial sites which together comprise the Phase 2 clinical trial. (see https://clinicaltrials.gov/ct2/show/NCT04247542). This Phase 2 clinical trial was designed to evaluate the clinical efficacy of ibezapolstat in the treatment of CDI including pharmacokinetics and microbiome changes from baseline and continue to test for anti-recurrence microbiome properties seen in the Phase 2a trial, including the treatment-related changes in alpha diversity and bacterial abundance and effects on bile acid metabolism. (Data published in Lancet, August 2025 https://www.thelancet.com/journals/lanmic/article/PIIS2666-5247(25)00054-0/fulltext).
About Ibezapolstat
Ibezapolstat is the Company's lead antibiotic candidate planning to advance to international Phase 3 clinical trials to treat patients with C. difficile infection. Ibezapolstat is a novel, orally administered antibiotic, being developed as a Gram-Positive Selective Spectrum (GPSS®) antibacterial. It is the first of a new class of DNA polymerase IIIC inhibitors under development by Acurx to treat bacterial infections. Ibezapolstat's unique spectrum of activity, which includes C. difficile but spares other Firmicutes and the important Actinobacteria phyla, appears to contribute to the maintenance of a healthy gut microbiome.
In June 2018, ibezapolstat was designated by the U.S. Food and Drug Administration (FDA) as a Qualified Infectious Disease Product (QIDP) for the treatment of patients with CDI and will be eligible to benefit from the incentives for the development of new antibiotics established under the Generating New Antibiotic Incentives Now (GAIN) Act. In 2019, FDA granted "Fast Track" designation to ibezapolstat for the treatment of patients with CDI. The CDC has designated C. difficile as an urgent threat highlighting the need for new antibiotics to treat CDI.