Patients with Lou Gehrig’s disease are angry about the possibility that the first new promising treatment in five years could be kept from them despite clinical evidence pointing to its benefits.

The treatment from Amylyx Pharmaceuticals, AMX0035, consists of two medications that are already widely used for other reasons but together could prolong ALS patients’ lives and slow the decline in their abilities to function. But the Food and Drug Administration’s panel of outside advisers voted narrowly in March to turn down Amylyx’s application for approval, citing concerns with the way researchers interpreted the data and the need for more robust clinical evidence from an additional, larger trial.