New Eye Drop Formulation Based on Desonide and Xanthan Gum in Dry Eye Disease: Nonclinical Studies.

Background/Objectives: A novel ophthalmic formulation, XanterDES, containing 0.2% xanthan gum and 0.025% desonide sodium phosphate (DES), was developed to alleviate ocular surface discomfort and irritation. This study aimed to evaluate its pharmacodynamic properties and to characterize its rheological behavior and mucoadhesive characteristics, compared to another formulation containing 0.2% hyaluronic acid and 0.001% hydrocortisone (HYD). Methods: A rabbit (New Zealand White) model of LPS-induced uveitis was used to test different concentrations of DES on ocular markers of inflammation. The efficacy of XanterDES and HYD on induced dry eye was evaluated by assessing tear volume and corneal damage in C57BL/6 mice exposed to a controlled environmental chamber. The rheological and mucoadhesive properties of XanterDES and HYD were assessed using a HAAKE RheoStress RS600 rheometer and a TA-XT2 texture analyzer, respectively. Results: In the uveitis model, unlike DES 0.25%, a low concentration of 0.025% DES showed a significant inhibitory activity localized to the eye surface and effectively reduced corneal edema. In the dry eye model, XanterDES demonstrated superior efficacy compared to HYD, effectively preventing both tear volume reduction and corneal damage. XanterDES also demonstrated pseudoplastic and enhanced mucoadhesive properties compared to HYD. Conclusions: The ancillary anti-inflammatory effects of a low dose of DES combined with the biophysical properties of xanthan gum are supportive of a favorable therapeutic profile, promoting the maintenance or restoration of ocular surface homeostasis while minimizing the risk of adverse effects typically associated with standard-dose corticosteroids. The comparison with another low-dose corticosteroid highlights the superiority of XanterDES in pharmacodynamic and biophysical performance.