Submitted October 30, 2008
Accepted April 10, 2009
Hexavalent bispecific antibodies represent a new class of anticancer therapeutics: 1. properties of anti-CD20/CD22 antibodies in lymphoma
Edmund A. Rossi*, David M. Goldenberg, Thomas M. Cardillo, Rhona Stein, and Chien-Hsing Chang
IBC Pharmaceuticals, Inc., Morris Plains, NJ, United States
Garden State Cancer Center, Center for Molecular Medicine and Immunology, Belleville, NJ, United States
Immunomedics, Inc., Morris Plains, NJ, United States
* Corresponding author; email: erossi{at}immunomedics.com.
The Dock-and-Lock (DNL) method is a new technology for generating multivalent antibodies. Here, we report in-vitro and in-vivo characterizations of 20-22 and 22-20, a pair of humanized hexavalent anti-CD20/22 bispecific antibodies (bsAbs) derived from veltuzumab (v-mab) and epratuzumab (e-mab). 22-20 was made by site-specific conjugation of e-mab to four Fabs of v-mab. 20-22 is of the opposite configuration, comprising v-mab and four Fabs of e-mab. Each bsAb was found to translocate both CD22 and CD20 into lipid rafts, and to induce apoptosis and growth inhibition without second-antibody crosslinking, and to be significantly more potent in killing lymphoma cells in-vitro than their parental antibodies. Although both bsAbs triggered antibody-dependent cellular toxicity, neither displayed complement-dependent cytotoxicity. Intriguingly, 22-20 and 20-22 killed human lymphoma cells in preference to normal B cells ex-vivo, whereas the parental v-mab depleted malignant and normal B cells about equally. In-vivo studies in Daudi tumors revealed 20-22, despite having a shorter serum half-life, had anti-tumor efficacy comparable to equimolar v-mab. 22-20 was less potent than 20-22, but more effective than e-mab and control bsAbs. These results indicate multiple advantages of hexavalent anti-CD20/22 bsAbs over the individual parental antibodies, and suggest that these may represent a new class of cancer therapeutics.
