A Paragon Biosciences company, Castle Creek Pharma raises $71.8 million to develop generic medicine for joint swelling and pain as a skin disease treatment.

Paragon Biosciences is run by Jeff Aronin, who was previously CEO of Marathon Pharmaceuticals, the company that gained FDA approval for an old generic steroid (deflazacort) as a new treatment (Emflaza) for the orphan disease Duchenne muscular dystrophy (DMD). Marathon charged a list price of $89,000 for the treatment – compared to the just over $1000 per year charged by a UK supplier of deflazacort. The pricing scandal forced Marathon to sell the drug (to PTC Therapeutics) and halt operations.

Aronin is now pursuing the repurposing of another generic drug as a treatment for another orphan indication. The drug is diacerein, an oral IL-1β inhibitor used to treat joint swelling or pain in several countries—it has not received approval in the US. It is approved for restricted use in the EU, due to risks of diarrhea and liver problems.

Paragon Biosciences dermatology-focused company Castle Creek Pharma, headed by Marathon’s CNS unit president and general manager Michael Derby, is developing diacerein (CCP-020) as a topical ointment for the treatment of epidermolysis bullosa simplex, a subtype of the already rare genetic condition known as “butterfly skin.” It recently raised $71.8 million from Fidelity Management & Research Company and Valor Equity Partner to continue a Phase II/III study for the drug, for which the FDA has granted a rare pediatric disease designation. Diacerein was shown in an earlier Phase II trial with 17 young EBS patients to reduce the number of blisters by 60% in 40% of the patients compared to placebo.

No discussion about the anticipated price of the drug has yet been offered by Paragon or Castle Creek.