TY - JOUR
T1 - A comparison of the in vitro and in vivo activities of IgG and F(ab′)2 fragments of a mixture of three monoclonal anti-Her-2 antibodies
AU - Spiridon, Camelia I.
AU - Guinn, Sarah
AU - Vitetta, Ellen S.
PY - 2004/5/15
Y1 - 2004/5/15
N2 - Purpose: We have demonstrated previously that a mixture of three anti-Her-2 monoclonal antibodies (MAbs) that bind to different epitopes on the extracellular domain of Her-2 expressed on a human breast cancer cell line has more potent antitumor activity than the individual MAbs both in vitro and in xenografted severe combined immunodeficient mice. Because the activity of Herceptin is Fc dependent, we determined whether this would also be the case when a mixture of these three anti-Her-2 MAbs was used. Experimental Design: IgG and highly purified F(ab′)2 fragments of the anti-Her-2 MAbs and Herceptin were prepared and evaluated for their ability to induce cell death, inhibit vascular endothelial growth factor secretion, and mediate antibody-dependent cellular cytotoxicity and complement-mediated cytotoxicity in vitro. They were also compared for their abilities to induce regression of large BT474 tumors in severe combined immunodeficient mice. Results: All of the F(ab′)2 fragments were >95% pure and, as expected, did not mediate antibody-dependent cellular cytotoxicity or complement-dependent cytotoxicity in vitro. The in vitro antiproliferative and proapoptotic effects of the IgGs and F(ab′)2 fragments were similar. In contrast, the IgGs had significant antitumor activity in vivo, whereas their F(ab′)2 fragments were only marginally effective even at 5-fold higher doses to offset their shorter half-lives. Conclusions: These results confirm the importance of the Fc portion of Herceptin for optimal in vivo activity and demonstrate that even a mixture of three anti-Her-2 MAbs that are highly effective at inducing cell death in vitro requires Fc-mediated effector function for optimal in vivo activity.
AB - Purpose: We have demonstrated previously that a mixture of three anti-Her-2 monoclonal antibodies (MAbs) that bind to different epitopes on the extracellular domain of Her-2 expressed on a human breast cancer cell line has more potent antitumor activity than the individual MAbs both in vitro and in xenografted severe combined immunodeficient mice. Because the activity of Herceptin is Fc dependent, we determined whether this would also be the case when a mixture of these three anti-Her-2 MAbs was used. Experimental Design: IgG and highly purified F(ab′)2 fragments of the anti-Her-2 MAbs and Herceptin were prepared and evaluated for their ability to induce cell death, inhibit vascular endothelial growth factor secretion, and mediate antibody-dependent cellular cytotoxicity and complement-mediated cytotoxicity in vitro. They were also compared for their abilities to induce regression of large BT474 tumors in severe combined immunodeficient mice. Results: All of the F(ab′)2 fragments were >95% pure and, as expected, did not mediate antibody-dependent cellular cytotoxicity or complement-dependent cytotoxicity in vitro. The in vitro antiproliferative and proapoptotic effects of the IgGs and F(ab′)2 fragments were similar. In contrast, the IgGs had significant antitumor activity in vivo, whereas their F(ab′)2 fragments were only marginally effective even at 5-fold higher doses to offset their shorter half-lives. Conclusions: These results confirm the importance of the Fc portion of Herceptin for optimal in vivo activity and demonstrate that even a mixture of three anti-Her-2 MAbs that are highly effective at inducing cell death in vitro requires Fc-mediated effector function for optimal in vivo activity.
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U2 - 10.1158/1078-0432.CCR-03-0549
DO - 10.1158/1078-0432.CCR-03-0549
M3 - Article
C2 - 15161714
AN - SCOPUS:2542460202
SN - 1078-0432
VL - 10
SP - 3542
EP - 3551
JO - Clinical Cancer Research
JF - Clinical Cancer Research
IS - 10
ER -