The company’s technology, a modified herpes simplex virus used to deliver gene therapies, was given the FDA’s new designation based on its approved topical skin cream. What this will mean for Krystal’s still-in-development eye drop is unclear.
On Oct. 14, Krystal Biotech received the second ever Platform Technology Designation from the FDA. Because Sarepta’s designation—the first ever granted—was revoked in July, Krystal’s is the only active designation. With that comes never-before-answered questions.
The designation is meant to accelerate approvals for therapeutics that use the same kinds of technology. Sarepta’s was based on its AAV vector for delivering gene therapies but was later rescinded after a third patient death was associated with the platform this summer. Krystal’s is based on a modified herpes simplex virus (HSV) vector used in the company’s approved topical therapy, Vyjuvek, indicated for the skin condition dystrophic epidermolysis bullosa.
Krystal’s investigational KB801, in Phase I/II trials for a rare corneal disease called neurotropic keratitis, shares the HSV vector, so the designation could accelerate its FDA review. But because KB801 is formulated as an eyedrop, the details are murky, William Blair analyst Sami Corwin told BioSpace. “Krystal is interesting because [KB801] uses the same HSV [vector] but the route of administration is totally different.”
Theoretically, Corwin and her colleagues wrote in a note to investors on Oct. 14, KB801 could benefit from “earlier and more frequent engagement with the FDA” to rapidly advance through the clinic and be on the market by 2028. The analysts also noted that Krystal may be able “to leverage manufacturing and nonclinical safety data from Vyjuvek in future submissions involving the HSV-1 vector.” But, she told BioSpace, FDA commissioner Marty Makary, in discussing the rationale of Platform Technology designations, “has talked about accelerated approvals based on a ‘rational mechanism of action’ which isn’t clearly defined,” in the FDA’s documentation.
When reached for comment, Stéphane Paquette, Krystal’s vice president for corporate development, said that “aspects of the delivery of the vector were not under discussion” between the FDA and the company regarding the platform designation.
Sarfaraz Niazi, an adjunct professor at the University of Illinois’ College of Pharmacy, told BioSpace the FDA requires sponsors to demonstrate that new applications of the platform don’t raise new safety issues.
“In the case of Krystal’s topical-to-ocular transition, the main areas the FDA would scrutinize include differences in tissue exposure, immune environment, and potential off-target effects,” Niazi wrote in an email. “The PTD designation implies that the FDA has found the HSV-1 platform sufficiently well-characterized to warrant cross-application review efficiencies, but it does not pre-clear ocular-specific risks.”
Krystal’s stock is up about 4% to $195.59 per share since receiving the PTD one week ago.
