Potent antibacterial activity in surgical wounds with local administration of D-PLEX₁₀₀

Despite significant advances in infection control guidelines and practices, surgical site infections remain a substantial cause of morbidity, prolonged hospitalization, and mortality. The most effective component of SSI reduction strategies is the preoperative administration of intravenous antibiotics; however, systemic antibiotics drug exposure diminishes rapidly and may result in insufficient prophylactic activity against susceptible and resistant SSI pathogens at the wound. D-PLEX₁₀₀ (D-PLEX) is an antibiotic-releasing drug (doxycycline) that is supplied as a sterile powder for paste reconstitution with sterile saline. D-PLEX paste is administered locally into the incision site along the entire length of soft tissue and sternal bone wound surfaces prior to skin closure. A single D-PLEX administration is intended for 30 days of constant antimicrobial prophylaxis in the prevention of incisional SSIs. We evaluated D-PLEX minimal bactericidal concentration (MBC) against a panel of bacteria that is prevalent in the abdominal wall and sternal surgical procedures including doxycycline susceptible and resistant strains. D-PLEX in vivo efficacy was assessed in incisional infection rabbit models (abdominal wall and sternal) challenged with a similar bacterial panel. The D-PLEX drug exposure profile was determined by in vitro release assay, and in vivo by quantitative pharmacokinetic parameters of local and systemic doxycycline concentrations released from D-PLEX after local administration in incisional rabbit models. Analyses of pathogens and variations in antibiotic resistance from wound isolates were determined from patients who participated in a previously reported prospective randomized trial that assessed the SSI rate in D-PLEX plus standard of care (SOC) versus SOC alone in colorectal resection surgery. The D-PLEX MBC values demonstrated >3- Log₁₀ reduction in all the organisms tested relative to untreated controls, including doxycycline-resistant bacteria (i.e., Methicillin-resistant Staphylococcus aureus (MRSA), K. pneumoniae, and P. aeruginosa). In vivo, D-PLEX significantly reduced the bacterial loads in all the bacteria tested in both animal models (p=0.0001) with a marked impact observed in E. Coli (>6.5 Log₁₀ reduction). D-PLEX exhibited a zero-order release kinetics profile in vitro for 30 days (R² = 0.971) and the matched in vivo release profile indicated a constant local release of protein-unbound doxycycline for 30 days at 3-5 mcg/mL with significantly lower (>3 orders of magnitudes) systemic levels. In colorectal surgery patients, where significant SSI reduction was observed, analysis of the positive cultures in the overall population indicated similar pathogen diversity and antibiotic resistance rates in both treatment arms. However, almost all the patients with positive culture in the SOC arm were adjudicated as SSI (94%) compared to only 28% in the D-PLEX arm. The SSI-adjudicated D-PLEX patients also exhibited lower resistance rates to the SOC antibiotics and to MDRs compared to patients in the SOC arm. Thus, D-PLEX provides safe and effective prophylaxis activity against the most prevalent SSI pathogens including doxycycline-susceptible and resistant bacteria. Our findings suggest that D-PLEX is a promising addition to SSI prophylactic bundles and may address the gaps in current SSI prophylaxis. D-PLEX is now evaluated in Phase 3 clinical trial.