Florida Cancer Specialists & Research Institute has published promising results from a phase 1/2 clinical trial investigating an innovative approach to enhance immunotherapy effectiveness through gut microbiome modulation. The study, led by Dr. Judy Wang and published in the August 2025 issue of Investigational New Drugs, evaluated the combination of oral bacterial supplement EDP1503 with pembrolizumab in patients with advanced cancers.
Study Design and Patient Population
The open-label study was conducted at multiple sites across the United States and Canada between 2018 and 2021. Researchers investigated the safety, tolerability, and efficacy of EDP1503 both as monotherapy and in combination with pembrolizumab (KEYTRUDA®) in patients with three specific cancer types: advanced microsatellite-stable colorectal cancer, triple-negative breast cancer, and checkpoint inhibitor-relapsed tumors.
Safety and Efficacy Findings
The trial demonstrated that EDP1503 was "generally safe and well tolerated as monotherapy and in combination with pembrolizumab," according to the study authors. More significantly, the combination regimen "demonstrated clinical benefit in a subset of subjects," suggesting potential therapeutic value for this novel approach.
Dr. Wang explained the rationale behind the study: "While immune checkpoint inhibitors have helped many people with cancer, some patients don't respond or may stop responding over time. One reason this can happen is that the gut microbiome and other factors can affect how well the treatment works."
Clinical Implications and Future Directions
The authors concluded that the "emerging anti-tumor activity warrants further large prospective studies," indicating that the preliminary results justify continued investigation of this therapeutic approach. However, they also acknowledged the challenges inherent in this field of research, noting that "comparing studies of live bacterial biotherapeutics can be challenging because of the variability of bacterial strains tested, treatment dosage, and treatment duration."
Despite these challenges, the researchers emphasized that "ongoing studies are evaluating oral bacterial supplementation to improve immunotherapy response," highlighting the growing interest in microbiome-based cancer therapeutics.
Research Partnership and Infrastructure
The study was conducted through a partnership with Sarah Cannon Research Institute, leveraging Florida Cancer Specialists' extensive clinical research infrastructure. FCS provides access to more than 150 clinical trials within 29 clinics and three early-phase Drug Development Units located in Sarasota and Central Florida.
Dr. Manish R. Patel, FCS medical director of drug development, emphasized the broader significance of such research: "Every clinical trial deepens our understanding of cancer and paves the way for better treatments, improved patient care, and brighter outcomes for patients worldwide."
The organization notes that in recent years, the majority of new cancer drugs approved for use in the United States were studied in clinical trials with FCS participation prior to approval, with many beginning as Phase 1 or first-in-human clinical trials at FCS Drug Development Units.
