Hereditary angioedema and peptides — the rare-disease indication where the entire modern therapeutic class engages a peptide pathway

Why this dossier exists

Hereditary angioedema is the rare-disease indication where every clinically meaningful therapeutic developed over the past two decades engages the kallikrein-kinin pathway — and where the peptide pharmacology of that pathway is what licenses the medicines. The disorder is a serpin-deficiency state in which absent or dysfunctional C1 esterase inhibitor (C1-INH) leaves the contact system unrestrained, plasma kallikrein cleaves high-molecular-weight kininogen to liberate bradykinin, and bradykinin acting at the vascular B2 receptor produces the cycles of subcutaneous, submucosal, gastrointestinal, and laryngeal swelling that define the disease. The modern therapeutic landscape contains a B2-receptor antagonist decapeptide, a recombinant kallikrein-inhibiting peptide, plasma-derived and recombinant C1-INH protein concentrates, a humanized anti-plasma-kallikrein monoclonal antibody, an oral small-molecule kallikrein inhibitor, an antisense oligonucleotide targeting prekallikrein mRNA, and an anti-factor-XIIa monoclonal antibody. Eight molecules across five mechanism classes, all converging on the same peptide-pathway target — this is the cleanest mechanism-to-therapeutic-class indication in this corpus.

Prevalence is approximately 1.1 to 1.6 per 100,000 for C1-INH-deficient HAE in the systematic review of European epidemiology by Aygören-Pürsün E, Magerl M, Maetzel A, Maurer M, Orphanet J Rare Dis 2018, 13:73, with a Danish nationwide survey (Bygum A, Br J Dermatol 2009, 161:1153–1158) producing a point estimate of 1.41 per 100,000. The disease is autosomal-dominant for the C1-INH-deficient forms (HAE-1 and HAE-2), with causative mutations in SERPING1 on chromosome 11q12-q13.1 producing low antigen (HAE-1, approximately 85% of cases) or normal-antigen-with-low-function (HAE-2, approximately 15%). The historical mortality driver was untreated laryngeal angioedema. The retrospective cohort of Bork K, Hardt J, Witzke G, J Allergy Clin Immunol 2012, 130:692–697 followed 728 patients from 182 families and found laryngeal-attack mortality concentrated overwhelmingly in undiagnosed patients (63 deaths from asphyxiation) versus diagnosed patients (7 deaths) — establishing that diagnosis itself, more than any specific therapy, is the dominant survival variable. The earlier Mayo Clinic Proceedings review of 58 affected families (Bork K, Siedlecki K, Bosch S et al., Mayo Clin Proc 2000, 75:349–354) reported death by asphyxiation in approximately 40% of affected family members across multigenerational cohorts before modern targeted therapy was available — the foundational statistic behind the "untreated laryngeal HAE carries 30-40% mortality" framing that recurs across the disease literature.

The HAE editorial center in this corpus is the icatibant peptide page — the B2-receptor antagonist decapeptide that anchors on-demand acute treatment and is the only HAE molecule in this corpus that meets the strict peptide-as-API definition. The dossier walks the surrounding context: the disease taxonomy, the kallikrein-kinin pathway biology, the on-demand-versus-prophylaxis treatment dichotomy, the eight modern molecules and the trials that approved them, and the practical considerations (trigger avoidance, self-injection training, emergency action plans, family screening) that structurally limit self-managed HAE pharmacology to specialist supervision.