PURPOSE: Ectoine is a natural molecule originally found in extremophilic bacteria as an osmolyte, a low molecular weight compound that helps regulate osmotic pressure and maintain cellular homeostasis. Ectoine forms a net-like structure that surrounds macromolecules with a shield of water, protecting cells against environmental stressors including dryness. As such, there is growing interest in ectoine as an osmoprotectant for dry eye. This study compared a novel, preservative-free drop combining 2.0% ectoine and 0.25% hyaluronic acid (ArtE) with an existing, widely used eye drop, containing 0.1% hyaluronic acid (HA) in the treatment of mild-to-moderate dry eye disease (DED).

METHODS: At baseline, patients chose ArtE or HA drops; recruitment was limited per site and stratified by baseline TBUT (<5 vs >5 s) to avoid bias. Both products were used 1-2 drops/eye up to 6 times/day for 28 (+3) days. The primary endpoint was change in TBUT in the 'decisive eye', analysed for non-inferiority (Δ=25% of reference mean) using ANCOVA adjusting for baseline TBUT, centre and gender. Change in TBUT was also evaluated by a t-test for each treatment separately. Secondary endpoints included patient- and investigator-assessed symptom/clinical-sign scores, ocular surface disease index (OSDI), tear flow (Schirmer II test), corneal fluorescein staining (CFS), global efficacy/tolerability, adverse events (AEs) and compliance.

RESULTS: 75 adults were treated (ArtE n=35; HA n=30). ArtE met the pre-determined non-inferiority criterion versus HA for the primary endpoint. Assessing each treatment separately, in the decisive eye, mean TBUT increased by 2.5 s with ArtE (p=0.0010) and by 1.1 s with HA (p=0.1686). Symptoms/clinical signs and quality of life improved in both groups (mean total OSDI change, ArtE vs HA, was -17.5 vs -17.2). Tear flow increased from baseline by 1.8 vs 0.8 mm/5 min (ArtE vs HA). No serious AEs occurred; of 6 AEs reported, 5 (all considered severe: headache, ataxia, and bilateral eye pain) occurred in 1 patient with several comorbidities. Overall, tolerability was rated as 'very good'; 79.4% and 71.4% would continue use with ArtE and HA, respectively.

CONCLUSIONS: In routine care, preservative-free ArtE eye drops were comparable to HA drops over 4 weeks of treatment. Both treatments improved symptoms and OSDI-measured quality of life and were well tolerated with few, non-serious adverse events.