<h3>Objective:</h3> To report safety and efficacy in migraine patients who concomitantly used erenumab and INP104 over 24 weeks. <h3>Background:</h3> Breakthrough migraine attacks can occur while a patient is on preventive therapy; therefore, effective acute medications that can be used concomitantly without an increased risk of adverse events (AEs) are needed. INP104 is a combination of dihydroergotamine mesylate (DHE) and Precision Olfactory Delivery approved for the acute treatment of migraine. <h3>Design/Methods:</h3> This was a post hoc analysis of the Phase 3, open-label study (STOP 301) that assessed the safety, tolerability, and exploratory efficacy of INP104 in migraine. Patients used their best usual care during a 28-day screening period. Eligible patients were provided INP104 to nasally self-administer (1.45 mg) with self-recognized attacks over 24 weeks. Concomitant preventive migraine medications were permitted if stable and not contraindicated with DHE. Erenumab was the only approved calcitonin gene-related peptide monoclonal antibody at study initiation. <h3>Results:</h3> Over 24 weeks, 8 patients concomitantly used erenumab and INP104; 5 reported no AEs. Most AEs were mild or moderate in severity. One patient reported severe AEs, which included bronchitis and serious AEs of pulmonary embolism and visual disturbance; none was treatment related. One mild case of abnormal olfactory test in another patient was possibly treatment related. At baseline, 2-hour pain and most bothersome symptom (MBS) freedom was self-reported by 22.0% and 51.5% of patients on their best usual care, respectively. At months 1, 2, 3, 4, 5, and 6, 32.3% and 54.3%, 37.1% and 70.8%, 33.3% and 50.0%, 40.3% and 68.1%, 28.0% and 42.7%, and 26.7% and 33.3% self-reported 2-hour pain and MBS freedom post-INP104, respectively. <h3>Conclusions:</h3> Results suggest that INP104 may be an effective and well-tolerated acute therapy for migraine patients who concomitantly use erenumab as a preventive therapy, with sustained benefits over 6 months. <b>Disclosure:</b> Dr. Ahmed has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for Abbvie. Dr. Ahmed has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Biohaven. Dr. Vann has received personal compensation for serving as an employee of Impel Neuropharma. Dr. Vann has received personal compensation for serving as an employee of Biogen. Dr. Fitzpatrick has received personal compensation for serving as an employee of Impel Pharmaceuticals. Dr. Ray has received personal compensation for serving as an employee of Impel Pharmaceuticals. Dr. Ray has stock in Impel Pharmaceuticals. Dr. Shrewsbury has received personal compensation for serving as an employee of Impel NeuroPharma. Dr. Shrewsbury has received stock or an ownership interest from Impel NeuroPharma. Dr. Aurora has received personal compensation for serving as an employee of Impel Neuropharma. Dr. Aurora has stock in Impel Neurpharma.