Evaluation of a new Riboflavin Formulation (MDV1224) for Transepithelial Corneal Collagen Cross-linking

Abstract

Purpose: The conventional corneal collagen crosslinking (CXL), according to the Dresden protocol, have proved is efficiency for the stabilization of progressive keratoconus. This procedure presents various complications due to the epithelial removal that is indispensable for the riboflavin penetration into the corneal stroma. We wanted to evaluate a new riboflavin formulation allowing to perform a CXL preserving the epihtelium. Room temperature stability as well as in vitro corneal penetration of this new riboflavin-base formulation (MDV1224) has been reported (ARVO 2013, e-abstract C0178). MDV1224 has been obtained from lipophilic riboflavin-base and sodium tetraborate which results in an aqueous solution of various complexes between the borate ion and the ribitol moiety of riboflavin-base. The objective of our study was to evaluate the toxicity and the in vitro stromal penetration of MDV1224 in comparison to a commercial riboflavin phosphate formulation (Ricrolin) used in accordance with the Dresden protocol.

Methods: The assessment of the potential irritant and cytotoxic effects of MDV1224 has been carried out through the model of the reconstituted human corneal epithelium (HCE) provided by SkinEthic Laboratories (Nice, France). MDV1224, its positive control (1% Sodium Dodecyl Sulphate) and its negative control (saline) were placed on the surface of the corneal tissue and left in contact for 10min (irritation test) or 24hr (cytotoxic assay). The results are expressed as percentage of viability (MTT assay) compared to negative control. The transepithelial penetration of MDV1224 after instillation for 30 min on epithelialized rabbit corneas was evaluated in comparison to Ricrolin after instillation on de-epithelialized corneas. Ribloflavin diffusion in the cornea was analyzed by measuring riboflavin concentration in corneas using HPLC method.

Results: MDV1224 was not irritant (viability 95%-100%) or cytotoxic (viability 92%-98%). Stromal riboflavin penetration of MDV1224 was 2154±1247 ng/g and 1608±235 ng/g for Ricrolin.

Conclusions: These preliminary experimental studies suggest that MDV1224 is a promising formulation for riboflavin delivery in CXL treatment, preserving the epithelium. These studies have to be completed by a largest sample and the evaluation of the corneal structural modifications and biomechanics after UVA application.

Keywords: 482 cornea: epithelium • 480 cornea: basic science • 574 keratoconus