The antitumor activity of an anti-CD22 immunotoxin in SCID mice with disseminated Daudi lymphoma is enhanced by either an anti-CD19 antibody or an anti-CD19 immunotoxin

Abstract

The antitumor activities of immunotoxins (ITs) constructed with deglycosylated ricin A chain (dgA) and either anti-CD19 (HD37) or anti- CD22 (RFB4) monoclonal antibodies were compared in SCID mice with disseminated human Daudi lymphoma (SCID/Daudi). As reported previously, after intravenous injection with Daudi cells, SCID mice develop disseminated lymphoma, which infiltrates the vertebral column and causes paralysis of the hind legs before death. The mean paralysis time (MPT) has been taken as an end point in this tumor model. We have previously reported that early treatment of SCID/Daudi mice with RFB4 coupled to dgA prolongs the MPT in a manner consistent with the killing of 4 logs of tumor cells. In the present study, we show that HD37-dgA kills 2 logs of tumor cells. The lower potency of the HD37-dgA is consistent with its lower IC50 on Daudi cells in vitro. We further show that the antitumor activity of a mixture of HD37-dgA and RFB4-dgA is significantly enhanced in SCID/Daudi mice and is consistent with the killing in excess of 5 logs of tumor cells. However, identical enhancement was observed when a mixture of the RFB4-dgA and the HD37 antibody was administered. In contrast, enhancement was not observed when mice were injected with a mixture of the RFB4 antibody and the HD37-dgA. The results indicate that a “cocktail” of HD37 antibody and RFB4-dgA immunotoxin can have significant antitumor activity in this mouse model of lymphoma and suggest that combinations of particular antibodies and ITs may have cooperative antitumor activity.

Nanobody Based Dual Specific CARs

“…Targeting two or more antigens simultaneously could be an option to reduce outgrowth of antigen escape variants causing relapse and treatment failure. This has been shown earlier in the context of targeted immunotoxin treatments [ 12 , 13 , 14 ]. Different CAR approaches have been tested to achieve bispecificity by (i) mixing two T cell lines, each expressing one CAR specific for one antigen (mixing); (ii) transducing T cells to simultaneously express two different CARs (dual signaling CAR, combining) or (iii) transducing T cells to express one single CAR that consists of two antigen-binding domains in tandem (TanCAR, multiplexing).…”

Evidence to support the cellular mechanism involved in serum IgG homeostasis in humans

“…hIgG1 (k) was purchased from Sigma (St Louis, MO). RFB4 or HD37 [anti-CD22 and anti-CD19 respectively (24)] were used as sources of mIgG1. IgG were labeled with Alexa Fluor 647 (`Alexa 647') using Alexa Fluor 647 succinimidyl ester (Molecular Probes) and the protocol recommended by the manufacturer.…”

Picking the Optimal Target for Antibody-Drug Conjugates

“…In the 1980s, Ellen Vitetta and other investigators began exploring immunotoxins composed of anti-CD19 mAb linked to ricin and other protein toxins. 19,20,21 These agents were highly potent, but the immunogenicity and nonspecifıc toxicity of the protein toxins posed major problems that limited further development. 22,23 CD19 and other coreceptors found on B cells, including CD21, remain appealing targets for ADCs.…”