Dr. Robert Ryan, founder and CEO of Durham-based drug firm, is stepping down just months after the company focused on rare diseases was sold in a deal that ultimately could be worth $1 billion.

The Triangle Business Journal’s Jason deBruyn reported the news Thursday.

“We have had a very successful year at Scioderm, moving Zorblisa through the development process, so that this therapy can hopefully be available to families with Epidermolysis Bullosa as quickly as possible,” Ryan said in an email quoted by TBJ.

In August, Scioderm said it would acquired by Amicus Therapeutics of Cranbury, N.J., for $229 million, and the deal could grow to nearly $1 billion if Scioderm’s lead drug compound achieves certain clinical, regulatory and sales milestones.

Ryan was to join the executive team at Amicus, based on the original deal announcement.

Scioderm has begun phase three clinical trials of Zorblisa, its topical therapy for the treatment of blisters and lesions in patients with epidermolysis bullosa (EB), a rare genetic disease of the connective tissue.

“We believe we are well-positioned to rapidly complete the clinical development of Zorblisa and to make Zorblisa commercially available for all EB patients as quickly as possible,” said John F. Crowley, chairman and chief executive officer of Amicus and board member of Scioderm, at the time of the deal.

Amicus estimates that EB, which affects an estimated 30,000 to 40,000 people in the United States and 400,000 people worldwide, may be a potential $1 billion-plus global market opportunity.

“This combination of Amicus and Scioderm is a major win for EB patients,” said Ryan. “With the added resources and expertise that Amicus provides for the Zorblisa program, we are more confident than ever in our potential for success and our ability to deliver significant benefits to patients and families living with the devastating effects of EB.”

Zorblisa is a potential first-to-market therapy for EB. In 2013 it received “breakthrough therapy” designation from the U.S. Food and Drug Administration, a status given to drugs that demonstrate early clinical evidence of significant improvement over available therapy. The designation is intended to accelerate the development and review of medicines for serious or life-threatening conditions.

In phase two clinical trials Zorblisa was the first treatment to show significant benefit in wound closure across all major subtypes of the disease.