Patients with ultra-rare diseases worry FDA approach will leave them without treatment

Testing is difficult for drugs for rare diseases, and new rules may make it harder for sufferers to obtain life-saving drugs

US drug regulators have increasingly signaled a focus on faster approvals and rare diseases, but patients with ultra-rare ailments fear they are falling through the cracks, especially given challenges to conducting clinical trials.

One drug, elamipretide, garnered a narrow recommendation from independent advisers for the US Food and Drug Administration (FDA), but the agency rejected the drug's application in May and recommended another potential pathway for approval.