Antibody Name: M195 IgG2a (VH SGII/JH4 VL kIII/JK1)
References: Co, M.S., Avdalovic, N.M., Caron, P.C., Avdalovic, M.V., Scheinberg, D.A. and Queen, C. "Chimaeric and humanized antibodies with specificity for the CD33 antigen" J.Immunol. (1992) 148:1149-1154.
Caron, P.C., Co, M.S., Bull, M.K., Avdalovic, N.M., Queen, C. and Scheinberg, D.A. "Biological and immunological features of humanized M195 (Anti-CD33) monoclonal antibodies" Canc. Res. (1992) 52:6761-6767.
Co, M.S., Scheinberg, D.A., Avdalovic, N.M., McGraw, K., Vasqueq, M., Caron, P.C. and Queen, C. "Genetically engineered deglycosylation of the variable domain increases the affinity of an anti-CD33 monoclonal antibody" Mol. Immunol. (1993) 30:1361-1367.
Donor Antibody: mouse
Acceptor Antibody: Human IgG1/IgG3 | k
Antigen: CD33 (on normal and leukaemic myeloid cells) (p67 protein)
Laboratory: PDL, CA; Memorial Sloan-Kettering Cancer Center
Design: PDL design: maximal seq homology human FRs, taken from the same mAb to reduce "incompatibility in assembly". Build model of mouse mAb, identify FR residues with significant contact with CDR residues. Atypical residues changed to consensus at VH 89,91,104,105,107 and VL 10,63,106. EU is generally chosen because it is the only human mAb in SGI for which the VL sequence is available and because murine mAbs are "most homologous to human SGI".
Frameworks: human EU | EU (51% | 54% homology)
CDRs: All 6 VH and VL,Kabat Definition.
Backmutations: VH G27Y S30T M48I RV66-67KA F89V F91Y G94R E103W Y104G N105Q G107T
VL T10S Y36F M48I I63S E70D V106I
Binding: The humanised IgG3 mAb has HIGHER apparent affinity than the mouse, but is unstable in solution. The IgG1 had MUCH (10-fold) higher affinity than the mouse. Data produced first by Scratchard analysis and later by more accurate competition binding experiments.
Expression: Sp2/0 (ATCC CRL 1581)
Comment: Rationale for so many backmutations is that when anti-tac was tested in cynomolgus monkeys, the HAMA response was directed against CDR not FR. Increase in binding due to removal of glycosylation site at 73:H during humanisation.
Clinical Indication: Acute Myeloid Leukaemia (AML)

explanation of symbols and abbreviations

José Saldanha © 1997-8. Birkbeck College, London WC1E 7HX.