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Armata Pharmaceuticals Presents Positive Phase 2a Study Results on AP-SA02

On October 22, 2025, Armata Pharmaceuticals, Inc., a California-based biotechnology firm trading on the NYSE American under the ticker ARMP, showcased remarkable outcomes from their Phase 2a diSArm study. This trial focuses on their bacteriophage cocktail, AP-SA02, as a potential therapeutic solution for complicated Staphylococcus aureus bacteremia (SAB). The significant findings were the highlight of a late-breaking oral presentation at IDWeek 2025 in Atlanta, Georgia.

The abstract of the study, titled "A Phase 2a Randomized, Double-Blind, Controlled Trial of the Efficacy and Safety of an Intravenous (IV) Bacteriophage Cocktail (AP-SA02) vs. Placebo in Combination with Best Available Antibiotic Therapy (BAT) in Patients with Complicated Staphylococcus aureus Bacteremia," earned its place among the coveted late-breaking abstracts. Dr. Loren G. Miller, a prominent figure in infectious diseases at UCLA and Harbor-UCLA Medical Center, led the presentation.

Dr. Miller announced that this study provides groundbreaking confirmation of the efficacy of intravenous phage therapy for S. aureus bacteremia within a randomized clinical trial context. This study's compelling data opens doors for a Phase 3 superiority study, which, if successful, could establish phage therapy as a standard of care for this severe and often lethal infection.

Study Overview

The Phase 2a study included a total of 42 participants, with 29 patients receiving AP-SA02 in conjunction with BAT and 13 receiving placebo (only BAT). Notably, the study found methicillin-resistant S. aureus (MRSA) constituted approximately 38% of the infections in both treatment groups.

Clinical responses were meticulously tracked at two points—Day 12 (after one week of therapy) and the End of Study (EOS) four weeks post-therapy. Results on Day 12 revealed:

• - 88% clinical response rate in the AP-SA02 group versus 58% in the placebo group (p = 0.047) as evaluated by blinded site investigators.
• - 83% response rate based on the adjudication committee's assessment for the AP-SA02 group against 58% for placebo.

At later assessments, the placebo group exhibited a distressing 25% rate of non-response/relapse at both follow-up points, contrasting the 0% observed in the AP-SA02 group. These results reflect a sharp distinction in treatment outcome, further supporting the therapy's potential value.

Safety and Efficacy

Evaluation of patient safety was a crucial element of the diSArm study. AP-SA02 was well-tolerated, with no serious adverse events attributable to the study medication. Just 6% of participants in the AP-SA02 group reported treatment-emergent adverse events, compared to 0% in the placebo group.

Moreover, insights gleaned from this study illustrate the inherent genomic flexibility of AP-SA02, showcasing its capacity to evolve rapidly in response to diverse strains of S. aureus. Through careful selection and characterization of phage variants, Armata aims to maximize therapeutic effectiveness tailored to individual patient isolates, emphasizing the cocktail's complex and adaptive design.

Future Directions

The results from this study bolster Armata's plans for transitioning AP-SA02 into a pivotal Phase 3 trial anticipated for 2026, contingent upon feedback from the U.S. FDA. The company is actively collaborating with the FDA regarding a potential trial design aimed at establishing AP-SA02 as a formidable alternative treatment for complicated SAB.

Conclusion

In conclusion, the diSArm study marks a significant stride for Armata Pharmaceuticals in the clinical exploration of bacteriophage therapies. Armed with evidence supporting its efficacy and safety, the company stands poised to contribute vital advancements to the treatment landscape of challenging bacterial infections, advocating for phage therapy's integration into clinical practice. The evolving dialogue around these promising findings will echo in the biotechnology community long after IDWeek 2025 concludes.