Evaluation of the immunogenicity of the synthetic α-melanocyte-stimulating hormone (α-MSH) analogue afamelanotide ([Nle4-D-Phe7]-α-MSH, Scenesse®) in erythropoietic protoporphyria patients by ELISA detecting both anti-afamelanotide and anti-α-MSH antibodies.
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.


CONCLUSIONS
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.
Unilabs Dr. Weber, St. Gallen, Switzerland.
Stephan
S
Lengweiler
Saskia
S
Kreim
Jasmin
J
Barman-Aksözen
Marcus
M
Maurer
Elisabeth I
EI
Minder
D000906:Antibodies / Q000097:blood*; D057176:Compassionate Use Trials; D004343:Drug Implants; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D017092:Porphyria, Erythropoietic / Q000097:blood / Q000188:drug therapy* / Q000276:immunology*; D011237:Predictive Value of Tests; D013997:Time Factors; D016896:Treatment Outcome; D000521:alpha-MSH / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000276:immunology / Q000627:therapeutic use
D000906:Antibodies; D004343:Drug Implants; D000521:alpha-MSH; C534526:afamelanotide