Scioderm has signed a definitive agreement to be acquired by Amicus Therapeutics (NASDAQ: FOLD), a biotech developing treatments for rare and orphan diseases. The transaction, which is valued at up to $847 million, will be paid in cash and stock, with multiple amounts contingent on clinical, regulatory and sales milestones. Redmile Group has made a $50 million debt commitment for the deal; Leerink Partners and J.P. Morgan acted as financial advisors. Scioderm is backed by Lightstone Ventures and Morgenthaler, among others, and had raised $36 million in VC prior to the agreement, including a $20 million round late last year that valued the company at $108 million. The acquisition is expected to close before the end of 3Q.