title: Analysis of samples from patients treated with ReFacto for the presence of anti-SQ-peptide specific antibodies.
abstract: ReFacto lacks the major part of the B-domain, except for 14 amino acid residues from the N-terminal and C-terminal ends, which are linked into a 14 amino acid SQ-peptide tail in the C-terminal end of the 90 kD heavy chain, thereby introducing a new peptide sequence in the factor VIII (FVIII) molecule. Therefore, samples from some of the patients enrolled in the ReFacto clinical trials were analyzed for the emergence of anti-SQ-peptide antibodies in addition to determinations for inhibitors by Bethesda assay and for anti-FVIII antibodies by enzyme-linked immunosorbent assay (ELISA). An anti-peptide ELISA was developed using six partially overlapping 15-16 mer peptides covering the SQ-linker region. Results from ReFacto-treated anti-FVIII antibody-positive or -negative patients were compared with those for normal healthy adults and patients treated with other FVIII products. The pattern was compared with that for SQ-peptide specific monoclonal antibodies, each recognizing three or four overlapping SQ-peptides. Antibodies recognizing mainly one of the SQ-peptides were found in samples in some individuals from all investigated groups. This means that the anti-SQ reactivity found in patients treated with ReFacto is not induced by the SQ-sequence of the molecule but rather by some other agent, giving rise to antibodies cross-reactive with SQ-peptides.
authors.affiliation: Department of Biopharmaceutical Development, Biovitrum AB, Stockholm, Sweden. margareta.wiken@biovitrum.com
authors.forename: Margareta
authors.initials: M
authors.lastname: Wikén
authors.forename: Katarina
authors.initials: K
authors.lastname: Sjöberg
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D001323:Autoantibodies / Q000097:blood*; D016022:Case-Control Studies; D003429:Cross Reactions / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005169:Factor VIII / Q000235:genetics / Q000276:immunology* / Q000627:therapeutic use; D008040:Genetic Linkage / Q000276:immunology; D006467:Hemophilia A / Q000188:drug therapy / Q000276:immunology; D006801:Humans; D051379:Mice; D010446:Peptide Fragments / Q000276:immunology; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology / Q000627:therapeutic use
chemical_list: D001323:Autoantibodies; D010446:Peptide Fragments; D011994:Recombinant Proteins; C427184:recombinant factor VIII SQ; D005169:Factor VIII