Exhibit 99.1 Amylyx Pharmaceuticals Reports Fourth Quarter and Full Year 2023 Financial Results • Reported $380.8 million in net product revenue for the full year 2023, including$108.4 million in the fourth quarter • Delivered $49.3 million in net income for the full year 2023, including$4.7 million in the fourth quarter, and ended the year with cash, cash equivalents and short-term investments of $371.4 million • Management to host conference call and webcast today at 8:00 a.m. Eastern Time CAMBRIDGE, Ma ...