BridgeBio Pharma, Inc. and affiliate company Phoenix Tissue Repair announced data from the Phase 2 trial of PTR-01, an intravenously administered recombinant collagen 7 (rC7) protein replacement therapy, in patients with recessive dystrophic epidermolysis bullosa (RDEB). The data are being shared in a poster at the Society for Investigative Dermatology (SID) Annual Meeting 2022 between May 18 – 21, 2022 in Portland, Oregon. RDEB is a rare genetic disorder caused by mutations in the gene encoding collagen type VII (C7) and is one of the most severe forms of epidermolysis bullosa, characterized by severe and painful skin blistering, as well as extreme fragility and scarring of mucous membranes throughout the body.

There is currently no known cure or effective treatment available for patients suffering from this disease. he Phase 2, open-label study was designed to examine the effect of PTR-01 on wound healing as well as other endpoints, and to evaluate the long-term safety and tolerability of the drug candidate. The data shared at the 2022 SID Annual Meeting demonstrated that PTR-01 was well tolerated when given once per week for 4 weeks and then every other week for 14 weeks.

In addition, treatment with PTR-01 led to rapid, consistent, and durable wound healing as observed in reduction of wound surface area and clinician-reported assessments. Specifically, over 80% of target wounds (21/26) demonstrated a 50% or greater reduction in wound surface area at the end of treatment (day 120) compared to baseline. Notably, this response was observed in a breadth of wound types: recurrent (86%) and chronic (75%); and a range of wound sizes: large (89%) and small (77%), as determined by at least 50% reduction in wound surface area compared to baseline.

Clinician assessment of the same target lesions scored on a 7-pt scale compared to baseline demonstrated similar levels of efficacy and wound improvement. By day 15 after initiating treatment, 15 of 26 wounds (58%) met the response criteria of =2-point increase on the wound-specific scale, and at day 120, 18/26 wounds (69%) met the response criteria. Based on these criteria, four out of six patients who enrolled (67%) were responders since they had =2-point increase on this scale in =50% of their wounds at day 120.

Patient-reported outcomes measuring pain, essential function, mood, activities of daily living and disease impact also showed marked mean and median reductions comparing end of study to baseline. Notably, all patients that completed the study (N=5) reported a decrease in pain over the course of treatment with PTR-01. There was a 36% mean reduction in total pain from end of study compared to baseline as measured on the Instrument for Scoring Clinical Outcomes of Research for Epidermolysis Bullosa (iscorEB) patient reported subdomain scale.

Finally, systemic administration of PTR-01 resulted in rapid deposition of rC7 at the DEJ during the loading phase (first 28 days of treatment) and remained present up to 3 months after treatment.