Interplay between on-demand treatment trials for hereditary angioedema and treatment guidelines.

Over the past two decades, guidelines for the on-demand treatment of hereditary angioedema (HAE) attacks have undergone significant evolution. Early treatment guidelines, such as the Canadian 2003 International Consensus Algorithm, often gated on-demand treatment by attack location and/or severity. Pivotal trials for on-demand injectable treatments (plasma-derived C1 esterase inhibitor [C1INH], icatibant, ecallantide [US only], recombinant C1INH), which were approved in the US and EU between 2008-2014, were designed accordingly. Subsequent post hoc analyses of clinical trial data alongside real-world evidence led to a paradigm shift. In 2013, the US HAE Association guidelines recommended that all attacks, irrespective of location or severity, be considered for treatment as early as possible after onset to minimize morbidity and mortality. This approach remains the cornerstone of current treatment guidelines and has shaped the design of recent clinical trials, such as those for the investigational agents, oral plasma kallikrein inhibitor sebetralstat and oral bradykinin B2 receptor antagonist deucrictibant. This narrative review discusses the evolution of on-demand treatment guidelines, the clinical trial and real-world data that prompted significant revisions, and the subsequent changes to trial designs introduced to facilitate guideline compliance.