WASHINGTON (AP) — For two years, Becky Mourey pushed the Food and Drug Administration to approve an experimental drug for her Lou Gehrig’s disease. She went to members of Congress and health regulators to make the case for Relyvrio, until patient-advocates finally prevailed. In September, Relyvrio became only the third drug approved in the U.S. for ALS, or amyotrophic lateral sclerosis, an incurable neurodegenerative disease that is usually fatal within five years. But patients and physicians who celebrated Relyvrio’s approval several months ago are now contending with the obstacles posed by the U.S. health care system. Their odyssey is an...