XTRA4

XTRA4 is a sterile corneal storage solution designed to preserve donor corneas for keratoplasty at refrigerated temperatures (2-8°C) for up to 14 days. It is supplied as a single-use 20 mL solution in glass vials and is intended for use by physicians and eye bank operators to maintain corneal tissue viability during storage.

XTRA4 uses sodium hyaluronate as its deswelling agent and recombinant human serum albumin (rHSA) as a cell metabolism enhancer, whereas the predicate Optisol-GS uses dextran and chondroitin sulfate as osmotic agents and polypeptides as enhancers. Both contain the same antibiotics (gentamicin sulfate and streptomycin sulfate), are sterile, have 24-month shelf life, and are stored at 2-8°C in similar packaging.

ISO 10993-1 (biocompatibility evaluation), ISO 10993-5:2009 (cytotoxicity), ISO 10993-23:2021 (ocular irritation), ISO 10993-10:2021 (sensitization/GPMT), USP <1207.2> (container closure integrity), USP LAL testing (endotoxin), ASTM D4169 and ISTA3A (transport simulation).

XTRA4 and Optisol-GS share identical indications for use, principle of operation, and storage conditions (2-8°C for up to 14 days). Although XTRA4 uses different osmotic and metabolism-enhancing ingredients, an in vitro study on paired donor corneas demonstrated that XTRA4 preserves corneal endothelium structural integrity and cell density comparably to Optisol-GS on days 1 and 14. Combined with equivalent sterility, packaging, shelf-life, and biocompatibility (no cytotoxicity, ocular irritation, or sensitization), this performance equivalence establishes substantial equivalence despite compositional differences.