Background and Objective <p>Hereditary angioedema presents as recurrent, unpredictable, and often debilitating attacks of cutaneous/submucosal swelling. This study assessed the characteristics and treatment patterns of patients receiving long-term prophylaxis with the plasma kallikrein inhibitor lanadelumab in US clinical practice.</p> Methods <p>This retrospective longitudinal study, based on a physician panel-based medical chart review, included patients with a diagnosis of hereditary angioedema due to C1 esterase inhibitor deficiency/dysfunction (HAE-C1INH-Type1/2), initiating lanadelumab in/after August 2018 (index date), and with ≥ 3 months’ post-index follow-up (Part 1, <i>N</i> = 186) and, additionally, a dosing interval extension after initiating lanadelumab 300 mg every 2 weeks (Part 2, <i>N</i> = 75).</p> Results <p>Patients in Part 1 were predominantly aged ≥ 18 years (95.7%) with HAE-CINH-Type1 (90.3%); Part 2 included a higher proportion of patients with HAE-C1INH-Type2 (28.0% vs 9.7%). In Part 1, 115/165 (69.7%) patients with hereditary angioedema attack information experienced 371 attacks in the 3 months pre-index; these were mostly mild/moderate (60.4%) and most commonly affected the lips (38.0%) and hands (32.9%). In total, 19/155 (12.3%) patients had 39 attacks during the post-index period (mean ± standard deviation [interquartile range] attack rate: 0.1 ± 0.3 [0.0, 0.0] per month). In Part 2, a dosing interval extension was enabled by well-controlled disease (74/75, 98.7%); most patients (86.7%) transitioned from every 2 weeks to every 4 weeks dosing. Among patients with attack information, 7/72 (9.7%) experienced a hereditary angioedema attack while receiving an initial every 2 weeks dosing regimen and 4/75 (5.3%) after an extended-interval dosing regimen.</p> Conclusions <p>Lanadelumab dosing intervals can be individualized to maintain effective disease control. A dosing interval extension may be considered in well-controlled disease.</p>