The FDA has granted Fast Track Designation to QRX003, Ashburn, Virginia-based Quoin Pharmaceuticals Ltd.'s (Nasdaq: QNRX) investigational topical serine protease inhibitor lotion, for the treatment of peeling skin syndrome (PSS) — a rare genetic skin disorder with no approved treatment anywhere in the world. The designation, announced September 22, follows IND clearance in July 2026 and a Rare Pediatric Disease Designation granted earlier this month, and makes QRX003 the only compound in active company-sponsored clinical development for PSS.
PSS is a rare autosomal recessive genodermatosis caused by loss-of-function variants in the corneodesmosin gene (CDSN), resulting in excessive shedding of the superficial epidermis along with severe chronic pain and pruritus. QRX003 acts as a broad-spectrum serine protease inhibitor, designed to counter excessive protease activity and skin shedding. Its mechanism was originally developed around kallikrein dysregulation in Netherton syndrome, while in PSS it is intended to reduce proteolytic breakdown of already-compromised corneodesmosomes.
Quoin plans to initiate a Phase II/III study in PSS in the second half of 2026, enrolling up to 12 pediatric and adult patients across sites in the US and Europe. The 48-week protocol calls for twice-daily application to more than 80% of body surface area, with an interim data review at 24 weeks. The company is targeting a 2028 approval for the indication. The IND was supported by observations from an ongoing investigator-led single-subject pediatric study, in which improvements were recorded across the Modified Ichthyosis Area Severity Index (M-IASI), Investigator's Global Assessment (IGA), pruritus, and a pediatric quality-of-life measure (CDLQI) after more than 15 months of treatment, with no adverse events reported.
The PSS designation is the second Fast Track status granted to QRX003; the FDA granted the same designation for Netherton Syndrome on March 11, 2026. In NS, interim Phase II/III data from study CL-QRX003-004 reported in August 2026 showed that four of six participants achieved the primary endpoint of a 1-grade or greater improvement in IGA at Week 12 (66.7%; p=0.0087 vs. a pre-specified alpha of 0.0215), with no treatment-related serious adverse events. Quoin said it expects to complete enrollment of all 20 participants in CL-QRX003-004 by end of 2026 and report topline data in Q2 2027, with a potential NDA filing to follow.