Regeneron Pharmaceuticals will make its newly approved gene therapy for a rare, genetic form of hearing loss available for free in the U.S. The company hasn't yet decided how much it will charge in other countries, Regeneron CEO Leonard Schleifer told CNBC on Friday."We haven't set a price yet, but they should pay their fair share outside the United States," Schleifer said in an interview with CNBC's Becky Quick.