Water-Free Cyclosporine 0.1% in Dry Eye Disease: Formulation Rationale, Clinical Evidence, and Unresolved Questions.

Dry eye disease (DED) is a chronic, multifactorial ocular surface disorder driven by interacting mechanisms including inflammation, tear-film instability, hyperosmolar stress, and neurosensory dysfunction. Although topical cyclosporine is an established anti-inflammatory treatment for DED, conventional formulations may be limited by poor aqueous solubility, variable ocular penetration, delayed onset of effect, and instillation discomfort. Water-free cyclosporine ophthalmic solution 0.1% was developed to address these challenges by dissolving cyclosporine in a preservative-free semifluorinated alkane vehicle, perfluorobutylpentane (F4H5), with ethanol as a formulation aid, avoiding oils, surfactants, and aqueous excipients. This review summarizes the pharmacologic rationale, preclinical evidence, clinical trial programme, safety profile, and current therapeutic role of water-free cyclosporine 0.1% in DED. Across available studies, including Phase 2, ESSENCE-1, ESSENCE-2, and a Phase 3 trial in China, treatment consistently improved objective ocular surface signs, particularly total corneal fluorescein staining, with separation from vehicle observed as early as 2 weeks in pivotal trials. In pooled ESSENCE-1 and ESSENCE-2 analyses including 1162 patients, more than 50% of treated patients achieved a clinically relevant ≥3-grade improvement in total corneal fluorescein staining after 2 weeks. A 1-year open-label extension further suggested sustained efficacy and acceptable long-term safety. In contrast, superiority over vehicle for symptom endpoints at early primary time points has been less consistent, likely reflecting symptom-sign discordance in DED, short controlled follow-up, population heterogeneity, and the lubricating properties of the vehicle. Overall, water-free cyclosporine 0.1% represents a credible addition to anti-inflammatory therapy for moderate-to-severe DED, especially when rapid improvement in corneal staining and good drop tolerability are priorities. However, the evidence base remains largely vehicle-controlled and industry-linked, with limited head-to-head comparison against other immunomodulators.