Krystal Biotech Announces First Patient Dosed in Phase 1/2 Trial of KB801 for the Treatment of Neurotrophic Keratitis

Krystal Biotech announced that the first patient has been dosed in its phase 1/2 clinical trial (EMERALD-1), a 2:1 randomized, double-masked, multicenter, placebo-controlled study evaluating KB801 for the treatment of neurotrophic keratitis (NK).

KB801 is a redosable eye drop gene therapy in development for the treatment of NK, a degenerative corneal disease characterized by damage or loss of function in the neurons innervating the eye leading to corneal epithelial defects, ulcers, and perforation. Left untreated, NK can result in severe vision loss. Although NK is a rare disease with an estimated prevalence in the range of 10 to 50 cases per 100,000, claims data analyses suggest awareness and diagnosis rates are on the rise in the United States. Based on available claims data, an estimated 68,000 patients in the United States had a NK claim in 2024, up over 115% from 31,000 patients with a NK claim in 2020, according to Krystal Biotech.

“Our ophthalmology pipeline is well under way with the dosing of our first patient in EMERALD-1, along with initiation of our phase 3 IOLITE study in DEB,” Suma Krishnan, President, Research & Development, Krystal Biotech, said in a company news release. “Until now, rapid protein clearance rates and high cell turnover in the front of the eye have severely limited the therapeutic potential of biologics and gene therapies for the treatment of corneal epithelial defects and other front of the eye diseases. We now have an opportunity to drive sustained expression and repeat administration of therapeutic biologic payloads with a simple eye drop application and look forward to delivering meaningful benefit to NK patients in need.”

EMERALD-1 is a randomized, double-masked, multicenter, placebo-controlled study evaluating KB801, administered as an eye drop, for the treatment of NK. Up to 27 adults with Stage 2 or Stage 3 NK, as defined by the Mackie criteria, will be enrolled and randomized 2:1 to receive either KB801, at a concentration of 1010 PFU/mL, or placebo topically to the study eye twice weekly for 8 weeks.

The primary objective of EMERALD-1 is to evaluate the safety and tolerability of topical ocular administration of KB801 in patients with NK. The secondary objective is evaluation of efficacy based on the proportion of patients with complete durable healing of corneal epithelium at 8 weeks, defined as 0 mm corneal fluorescein staining in the area of the corneal lesion at both week 8 and 0 mm corneal fluorescein staining in the same area at week 10, as assessed by a masked reader. Additional exploratory efficacy measures will include change in corneal lesion size from baseline, each assessed at weeks 4, 6, 8, 10, and 20, as well as evaluations of corneal sensation and patient-reported symptom burden.

More details of the EMERALD-1 study can be found at www.clinicaltrials.gov under NCT identifier NCT06999733.

The Company will host an investor conference call and webcast today, Wednesday, July 9, 2025, at 8:30 am ET, to discuss NK, the KB801 program, and clinical study design. Investors and the general public can access the live webcast at: https://www.webcaster4.com/Webcast/Page/3018/52704. For those unable to listen to the live webcast, an archived version will also be available on the Investors section of the Company’s website for at least 30 days.

About KB801

KB801 is a redosable eye drop gene therapy designed to enable sustained, localized expression and secretion of nerve growth factor (NGF) by epithelial cells in the front of the eye for the treatment of neurotrophic keratitis (NK), a rare, degenerative corneal disease that leads to corneal epithelial defects, ulcers, and perforation. Recombinant NGF eye drops have been shown to significantly improve corneal healing and are approved for the treatment of NK in multiple jurisdictions worldwide, but rapid clearance from the eye requires intensive administration six times a day, limiting therapeutic utility. By enabling the cells of the front of the eye to produce NGF locally, KB801 has the potential to significantly reduce the treatment burden for patients while also maintaining more consistent NGF levels in the front of the eye.