Hereditary angioedema: Investigational therapies and future research

The future therapies for hereditary angioedema will likely involve the development of oral agents as alternatives to parenteral administration of drugs, specific targeting of proteins and/or enzymes that are not yet possible (e.g., factor XIIa), new agents that target the β₂ receptor with sustained action properties, testing of products to determine whether the β₁ receptor contributes significantly to attacks of angioedema, disrupting protein synthesis by using RNA technology as an alternative to enzyme inhibition, and, finally, gene therapy to attempt to cure the disease. Complete inhibition of attacks may well require sustained blood levels of C1 inhibitor that exceed 85% of normal, and it may be possible to delete the prekallikrein gene (analogous to familial prekallikrein deficiency), which is the one factor that might alleviate bradykinin formation, even by factor XII-independent initiating mechanisms, with the possible exception of Mannose Associated Serine Protease 1 (MASP-1) cleavage of high molecular weight kininogen (HK). Deletion of the light chain of high-molecular-weight kininogen would eliminate all possibilities for bradykinin formation, except tissue kallikrein cleavage of low-molecular-weight kininogen to support normal physiologic function to at least 50%.