Evaluation of the Immunogenicity of the Synthetic α-Melanocyte-Stimulating Hormone (α-MSH) Analogue Afamelanotide ([Nle4-<smlcap>D</smlcap>-Phe7]-α-MSH, Scenesse®) in Erythropoietic Protoporphyria Patients by ELISA Detecting Both Anti-Afamelan

Afamelanotide is an α-melanocyte-stimulating hormone (α-MSH) agonist with proven efficacy in photodermatoses such as erythropoietic protoporphyria (EPP). This peptide drug, repeatedly administered over prolonged time, may induce anti-drug antibodies (ADA). Here, we describe a new ELISA method developed to monitor the occurrence of ADA against afamelanotide as well as against α-MSH. Covalent binding instead of absorption of antigen onto the microtitre wells prevented antigen leakage and enabled extensive washings followed by lower background. The cut-off between antibody-negative and -positive sera was determined. Inhibition of the antigen-antibody reaction by excess soluble antigen tested for specificity. The sensitivity of the ELISA was 608 and 1,390 ng/ml of specific ADA against afamelanotide and α-MSH, respectively. This ELISA method enabled us to investigate the occurrence of ADA during long-term administration of afamelanotide. No immunoreactivity was found in 23 of the 26 EPP patients exposed to the drug for up to 6 years. Pre-existing immunoreactivity against afamelanotide as well as α-MSH was found in 3 patients, whose titres did not change during afamelanotide administration. <b><i>Conclusion:</i></b> The new ELISA is suitable to determine ADA against afamelanotide and α-MSH. Afamelanotide did not elicit ADA during long-term administration in patients with EPP. © 2014 S. Karger AG, Basel