Abstract 3622: An antibody-based multifaceted approach targeting the human transferrin receptor for the treatment of multiple myeloma

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL We previously developed an antibody-avidin fusion protein (ch128.1Av) targeting the human transferrin receptor 1 (TfR1, CD71) that demonstrates direct in vitro cytotoxicity against malignant hematopoietic cells. This cytotoxicity is due to its ability to decrease TfR1 levels leading to lethal iron deprivation. We now report that ch128.1Av shows the ability to bind the Fc gamma receptors and the complement component C1q, suggesting that is capable of eliciting Fc-mediated effector functions such as antibody-dependent cytotoxicity (ADCC) and complement-mediated cytotoxicity (CDC). Additionally, in two disseminated multiple myeloma xenograft mouse models, we show that a single dose of ch128.1Av results in significant anti-tumor activity including long-term survival. Interestingly, the parental antibody without avidin (ch128.1) also shows remarkable in vivo anti-cancer activity despite its lack of in vitro cytotoxicity. Finally, we demonstrate that ch128.1Av is not toxic to pluripotent hematopoietic progenitor cells using the Long-Term Cell-Initiating Culture (LTC-IC) assay suggesting that these important progenitors would be preserved in different therapeutic approaches, including the in vitro purging of cancer cells for autologous transplantation and in vivo passive immunotherapy. Our results suggest that ch128.1Av and ch128.1 may be effective in the therapy of human multiple myeloma and potentially other hematopoietic malignancies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3622. doi:10.1158/1538-7445.AM2011-3622