Exhibit 99.1 Assertio Reports Fourth Quarter and Full Year 2023 Financial Results Fourth Quarter Net Product Sales $32.5 Million, Cash Flow from Operations of $5.7 Million 2024 Full Year Outlook for Net Product Sales of $110 to $125 Million, Adjusted EBITDA of $20 to $30 Million LAKE FOREST, IL. – March 11, 2024 – Assertio Holdings, Inc. (“Assertio” or the “Company”) (Nasdaq: ASRT), a pharmaceutical company with comprehensive commercial capabilities offering differentiated products to patients, today report ...