Abrogation of antibody responses in rats to murine monoclonal antibody 791T/36 by treatment with daunomycin-cis-aconityl-791T/36 conjugates.

The majority of monoclonal antibodies in clinical use are of murine origin. It is now well-established that patients generate an antibody response to the mouse immunoglobulin which restricts repeated administration. Pre-sensitization of patients to mouse antibody is screened by hypersensitivity to i.d. administered antibody. This study shows that low doses of mouse antibody administered either i.d. or s.c. are highly immunogenic and suggests that a serological assay would be a safer method of screening for anti-mouse antibodies. Rats treated with monoclonal antibody linked via an acid labile cis-aconityl bond to daunomycin failed to produce a primary response to this conjugate. They were also rendered immunologically unresponsive to subsequent challenges with the unconjugated monoclonal antibody. The induced state of immunological unresponsiveness to free antibody persisted in the rats for 18 weeks and although antibody-cis-aconityl-daunomycin pre-treated animals eventually responded to the fourth challenge with free antibody, at week 25, the response was still significantly less than in the free antibody-pre-treated and challenged animals. These studies show that the use of antibody-cis-aconityl-daunomycin conjugates may provide an approach for the control of human responses to mouse immunoglobulin.