Use of anti-CD3 x anti-HER2/neu bispecific antibody for redirecting cytotoxicity of activated T cells toward HER2/neu+ tumors

Relapse after adjuvant chemotherapy or high-dose chemotherapy with stem cel l transplant for highrisk breast cancer remains high and new strategies tha t provide additional antitumor effects are needed. This report describes me thods to generate highly effective HER2/neu-specific cytotoxic T cells by a rming activated T cells with anti-CD3 x anti-HER2/neu bispecific antibody ( BsAb). OKT3 and 9184 (anti-HER2) monoclonal antibodies (mAb) were conjugate d and used to arm T cells that were subsequently tested in binding, cytotox icity, and cytokine secretion assays. Armed T cells aggregated and specific ally killed HER2/neu(+) breast cancer cells. Cytotoxicity emerged after 6 d ays of culture, was higher in armed T cells than unarmed T cells at all eff ector to target ratios (E/T) tested, and increased as the arming dose was i ncreased. At an E/T of 20:1, the mean cytotoxicity of armed activated T cel ls (ATC) from 10 normal subjects increased by 59 +/- 11% (+/-SD) over that seen in unarmed ATC (p < 0.001) and the mean cytotoxicity of armed ATC from 6 cancer patients increased by 32 +/- 9% above that seen for unarmed ATC ( p < 0.0004). After arming, the BsAb persisted on ATC up to 72 h and armed A TC continued to be cytotoxic up to 54 h. The amount of interferon-gamma (IF N-gamma), tumor necrosis factor-alpha (TNF-alpha), and granulocyte-macropha ge colony-stimulating factor (GM-CSF) secreted was 1699, 922, and 3092 pg/m l/10(6) cells per 24 h, respectively, when armed T cells were exposed to a HER2/neu(+) breast carcinoma cell line. These studies show the feasibility and clinical adaptability of this approach for generating large numbers of anti-HER2-specific, cytotoxic T cells for clinical trials.