A Multicenter, Real-World Experience with Polyhexamethylene Biguanide (PHMB) 0.08% Monotherapy for Treating Acanthamoeba Keratitis: A Retrospective Review of 39 Cases

Introduction: Topical polyhexamethylene biguanide (PHMB) 0.08% (AKANTIOR®, SIFI Italy) is the only licensed medicinal product for the treatment of Acanthamoeba keratitis (AK), demonstrating an 84.9% cure rate in a pivotal clinical trial. This study aimed to evaluate its effectiveness and safety in a routine clinical practice. Methods: We retrospectively reviewed patient charts from ten Italian centers for the treatment of AK with PHMB 0.08% monotherapy. The treatment protocol followed that used in the pivotal trial. The primary outcome was medical cure, defined as a healed epithelium without inflammation and treatment for at least four weeks. Treatment failure was defined as the need for surgery or the use of alternative or additional anti-amoebic treatments (AAT). Secondary outcomes included best-corrected visual acuity (BCVA), time to cure, pain, and corneal scarring. Results: Thirty-nine patients (M/F = 14/25) were evaluated. AK was confirmed by confocal microscopy ± polymerase chain reaction or culture in all cases. Sixteen (41%) had stage 3 AK. Thirty-five (89.7%; 95% confidence intervals 80.2–99.3) achieved medical cure. Four failures occurred: three required corneal surgery and one additional AAT. At the end of treatment, mean (SD) LogMAR BCVA was 0.7 (0.8); the median time to cure was 95 days (Q1–Q3: 63–140 days). Two patients (5.6%) reported residual pain, and 27 (73.0%) had corneal scarring. Four serious adverse events (three hypopyon, one corneal perforation) were reported and considered unlikely to be treatment-related. Conclusions: AKANTIOR cured approximately 90% of patients with AK, indicating that the efficacy observed in the clinical trial can be replicated in clinical practice. Trial Registration: ClinicalTrials.gov identifier, NCT06641882.