Pharmacologic Characterization of ALD403, a Potent Neutralizing Humanized Monoclonal Antibody Against the Calcitonin Gene-Related Peptide

Abstract

ALD403 is a genetically engineered, humanized immunoglobulin G1 monoclonal antibody that inhibits the action of human calcitonin gene-related peptide (CGRP). Clinical trial data indicate that ALD403 is effective as a preventive therapy for migraine and has an acceptable safety profile. For preclinical characterization of ALD403, rabbit antibodies targeting <i>α</i>-CGRP were humanized and modified to eliminate fragment crystallizable (Fc) <i>γ</i> receptor (Fc<i>γ</i>R) and complement interactions. The ability of ALD403 to inhibit CGRP-induced cAMP production was assessed using a cAMP bioassay (Meso Scale Discovery). The IC₅₀ for inhibition of cAMP release was 434 and 288 pM with the rabbit-human chimera antibody and the humanized ALD403, respectively. ALD403 inhibited <i>α</i>-CGRP binding with an IC₅₀ of 4.7 × 10^-11 and 1.2 × 10^-10 M for the <i>α</i>-CGRP and AMY1 receptors, respectively. ALD403 did not induce antibody-dependent cellular cytotoxicity or complement-dependent cytotoxicity and did not stably interact with any of the Fc<i>γ</i>R mediating these functions, exhibiting only weak binding to Fc<i>γ</i>RI. ALD403 significantly lowered capsaicin-induced blood flow responses in rodents at all time points starting at 5 minutes postapplication in a dose-dependent manner. In conclusion, ALD403 is a potent functional ligand inhibitor of <i>α</i>-CGRP‒driven pharmacology. SIGNIFICANCE STATEMENT: α-Calcitonin gene-related peptide blockade by ALD403 was assessed via radiolabeled ligand displacement, in vitro inhibition of cell signaling, and in vivo inhibition of capsaicin-induced vasodilation. Lack of engagement of fragment crystallizable-mediated immune-effector functions by ALD403 was shown.