<h3>Objective:</h3> To assess the long-term nasal safety and tolerability of STS101 in the acute treatment of migraine. <h3>Background:</h3> STS101 (dihydroergotamine nasal powder) is a novel investigational product with rapid and easy nasal delivery. The ASCEND study assesses the safety and tolerability of STS101 5.2 mg in the acute treatment of migraine with/without aura over 12 months. <h3>Design/Methods:</h3> ASCEND (NCT04406649) is a multi-center, multiple-dose, open-label study in adults (18–65 years) with migraine. Participants self-administered STS101 for ≤2 doses/24 hours and ≤12 doses/month for acute treatment of migraines for 12 months. This interim analysis included participants exclusively using the STS101 incorporating the second-generation nasal delivery device planned for commercialization. Nasal safety assessments included nasal treatment-emergent adverse events (TEAEs), subjective assessments of nasal irritation, and a smell test (SIT). Objective nasal assessments were done by trained study personnel on a 4-point severity scale to document nasal erythema, edema, rhinorrhea, bleeding, and nasal mucosa ulcerations. <h3>Results:</h3> This population included 344 subjects who treated 5,571 attacks with 6,918 doses of STS101 and was 40.4±10.9 years old (mean±SD), 85.8% female, and 87.5% Caucasian. Overall, 97 subjects (28.2%) reported nasal/local TEAEs; 8 of 344 subjects (2.9%) discontinued the study due to nasal/local TEAEs including nasal burning/discomfort (5), nasal bleeding (1), rhinitis (1), and throat tightness (1). Most frequently reported nasal/local related TEAEs were nasal discomfort (38 [11.0%] subjects; 338 [6.1%] attacks), dysgeusia (26 [7.6%]; 154 [2.8%]), and nasal congestion (14 [4.4%]; 198 [3.6%]). At 12 months, 99.5%, 95.4%, 93.5%, and 94.4% of subjects had no nasal bleeding/ulceration, edema, erythema, or rhinorrhea, respectively. No clinically relevant findings were seen from nasal examinations, subjective nasal irritation assessments, or smell tests. <h3>Conclusions:</h3> Nasal safety data from 5,571 treated attacks demonstrate the safety and tolerability of STS101 for the acute treatment of migraine. <b>Disclosure:</b> Dr. Spierings has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Manistee. Dr. Spierings has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for Lundbeck. Dr. Spierings has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for Lilly. Dr. Spierings has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for Abbvie. Detlef Albrecht has received personal compensation for serving as an employee of Satsuma. Detlef Albrecht has stock in Satsuma. Dr. Rapoport has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for AbbVie, Amgen, Biohaven, Cala Health, Satsuma, Teva Pharmaceutical Industries, Theranica, Xoc and Zosano. Dr. Rapoport has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for AbbVie, Amgen, Biohaven, Lundbeck and Teva Pharmaceutical Industries. Dr. Rapoport has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Neurology Reviews.