4D-125

4D-125 is an investigational gene therapy developed by 4D Molecular Therapeutics for the treatment of inherited retinal dystrophies caused by mutations in the RPGR gene, including X-linked retinitis pigmentosa (XLRP). It utilizes a targeted and evolved R100-based adeno-associated virus (AAV) vector designed for efficient intravitreal delivery to photoreceptors in the retina. The therapy delivers a functional copy of the RPGR gene to restore or preserve visual function. Clinical trials have shown that intravitreal administration of 4D-125 is well-tolerated, with no dose-limiting toxicities or serious adverse events observed. The program received FDA Fast Track designation but was discontinued after Phase I/II development for retinitis pigmentosa[1][2][3][5].