With phase 2 update, Krystal Biotech eyes phase 3 for rare skin disease gene therapy

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Krystal Biotech's epidermolysis bullosa treatment uses a viral vector to deliver working copies of the COL7A1 gene directly to the patient’s skin cells and heal wounds. (Pixabay)

Krystal Biotech unveiled data from a small phase 2 study showing its topical gene therapy closed the majority of wounds in patients with a rare skin disorder. The company is waiting on data for how long the wounds stayed closed after treatment before it moves the program into phase 3. It expects to start the pivotal trial by the end of the year. 

Pittsburgh-based Krystal Biotech is developing the therapy, KB103, for the most severe form of epidermolysis bullosa, a disease caused by mutations in the COL7A1 gene usually diagnosed in infancy. Babies born with the more severe form will have widespread blistering and areas where there is no skin. This can lead to other problems, such as vision loss, or difficulty eating due to blistering and scarring in the mouth and esophagus. 

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There is no approved drug for severe, generalized recessive dystrophic epidermolysis bullosa (RDEB)—current treatments focus on preventing blisters from forming and managing symptoms. Krystal’s treatment uses a viral vector to deliver working copies of the COL7A1 gene directly to the patient’s skin cells and heal wounds. 

RELATED: Krystal files for IPO to move gene therapies into clinic 

Krystal enrolled four patients—two adults and two adolescents—in the phase 2 study, called GEM-2. The investigators picked out three wounds up to 20 square centimeters in size for the trial, randomizing two-thirds of the wounds to receive KB103 and one-third to receive placebo. One of the adult patients dropped out of the trial because the site was too hard to get to, so the team ended up evaluating six treated wounds and three placebo-treated wounds, the company said in a statement. 

The KB103-treated wounds included four recurring wounds—which open and close spontaneously—and two chronic wounds, defined as wounds that stayed open for more than three months. Five of the six wounds closed completely during the trial, taking an average of 23 days to heal. The less severe recurring wounds took an average of 19 days to close completely. 

The one wound that didn’t heal was particularly gnarly—the patient reported that it had been open for more than four years. Ninety days after treatment, it had closed 42%. The other chronic wound in the study took 41 days to close completely. None of the placebo-treated wounds closed fully during the three-month study. 

Krystal also announced updated data from a phase 1 study of KB103 in two patients with smaller wounds. The investigators selected two wounds per patient of up to 10 square centimeters in size to receive either KB103 or placebo. Both treated wounds in the phase 1 trial closed fully, taking an average of 12 days. As of the last follow-up visit, both the wounds had stayed closed for more than six months. 

“New treatments for patients suffering from EB are desperately needed, especially one that provides a convenient, painless way to administer treatment for patients suffering with this debilitating disease and to reduce their travel burden,” said principal investigator, Peter Marinkovich, M.D., an associate professor of dermatology at Stanford University, in the statement. “These exciting data in the Phase 1/2 trials are supportive of this very promising new approach for treating this debilitating disease.” 

RELATED: Fibrocell, Castle Creek ink rare disease gene therapy pacts worth up to $135M 

Krystal isn’t the only player developing a gene therapy for epidermolysis bullosa. FibroCell is working on an autologous gene therapy for RDEB, that is, one that is made from the patient’s own cells. FibroCell takes fibroblasts—cells that make collagen—and genetically modifies them to express the COL7 gene. Unlike Krystal’s topical treatment, FibroCell’s FCX-007 is injected into the patient’s wounds using a lentiviral vector. 

FibroCell licensed FCX-007 out to Castle Creek Pharma in April to usher it through the clinic and onto the market. The phase 3 study is slated to start before the end of the year and will enroll 15 to 20 patients. Castle Creek is working on its own treatment for a type of epidermolysis bullosa caused by a different mutation. 

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