Immunotargeting of daunomycin to localized and metastatic human colon adenocarcinoma in athymic mice

Immunotherapy using IgE or CAR T cells for cancers expressing the tumor antigen SLC3A2

Background

Cancer immunotherapy with monoclonal antibodies and chimeric antigen receptor (CAR) T cell therapies can benefit from selection of new targets with high levels of tumor specificity and from early assessments of efficacy and safety to derisk potential therapies.

Methods

Employing mass spectrometry, bioinformatics, immuno-mass spectrometry and CRISPR/Cas9 we identified the target of the tumor-specific SF-25 antibody. We engineered IgE and CAR T cell immunotherapies derived from the SF-25 clone and evaluated potential for cancer therapy.

Results

We identified the target of the SF-25 clone as the tumor-associated antigen SLC3A2, a cell surface protein with key roles in cancer metabolism. We generated IgE monoclonal antibody, and CAR T cell immunotherapies each recognizing SLC3A2. In concordance with preclinical and, more recently, clinical findings with the first-in-class IgE antibody MOv18 (recognizing the tumor-associated antigen Folate Receptor alpha), SF-25 IgE potentiated Fc-mediated effector functions against cancer cells in vitro and restricted human tumor xenograft growth in mice engrafted with human effector cells. The antibody did not trigger basophil activation in cancer patient blood ex vivo, suggesting failure to induce type I hypersensitivity, and supporting safe therapeutic administration. SLC3A2-specific CAR T cells demonstrated cytotoxicity against tumor cells, stimulated interferon-γ and interleukin-2 production in vitro. In vivo SLC3A2-specific CAR T cells significantly increased overall survival and reduced growth of subcutaneous PC3-LN3-luciferase xenografts. No weight loss, manifestations of cytokine release syndrome or graft-versus-host disease, were detected.

Conclusions

These findings identify efficacious and potentially safe tumor-targeting of SLC3A2 with novel immune-activating antibody and genetically modified cell therapies.

Synthesis of Succinimidoalkylbenzaldehyde Analogues: Potential Bifunctional Linkers for Bioconjugation

A series of novel 4-substituted benzaldehydes containing a succinimide moiety were synthesized as potential bifunctional linkers for the purpose of binding therapeutic drugs to antibodies raised against cancer cells. These potential benzaldehyde linkers varied in the nature of the para functionality so as to provide a range of potential acid labilities. Synthesis of the linkers involved a Williamson ether formation to make the ether linker 1, a Sonagoshira palladium-catalyzed coupling to synthesize the skeleton of the alkyl linker 2, and formation of an amide bond directly from a methyl ester gave the 4-substituted amide linker 3. As an example of the type of acetal that can be produced using these linkers, uridine was used as an analogue of the cytotoxic compound 5-fluorouridine to give the cyclic acetals 19–21.

Lysosomal enzyme delivery by ICAM-1-targeted nanocarriers bypassing glycosylation- and clathrin-dependent endocytosis

Enzyme replacement therapy, a state-of-the-art treatment for many lysosomal storage disorders, relies on carbohydrate-mediated binding of recombinant enzymes to receptors that mediate lysosomal delivery via clathrin-dependent endocytosis. Suboptimal glycosylation of recombinant enzymes and deficiency of clathrin-mediated endocytosis in some lysosomal enzyme-deficient cells limit delivery and efficacy of enzyme replacement therapy for lysosomal disorders. We explored a novel delivery strategy utilizing nanocarriers targeted to a glycosylation- and clathrin-independent receptor, intercellular adhesion molecule (ICAM)-1, a glycoprotein expressed on diverse cell types, up-regulated and functionally involved in inflammation, a hallmark of many lysosomal disorders. We targeted recombinant human acid sphingomyelinase (ASM), deficient in types A and B Niemann-Pick disease, to ICAM-1 by loading this enzyme to nanocarriers coated with anti-ICAM. Anti-ICAM/ASM nanocarriers, but not control ASM or ASM nanocarriers, bound to ICAM-1-positive cells (activated endothelial cells and Niemann-Pick disease patient fibroblasts) via ICAM-1, in a glycosylation-independent manner. Anti-ICAM/ASM nanocarriers entered cells via CAM-mediated endocytosis, bypassing the clathrin-dependent pathway, and trafficked to lysosomes, where delivered ASM displayed stable activity and alleviated lysosomal lipid accumulation. Therefore, lysosomal enzyme targeting using nanocarriers targeted to ICAM-1 bypasses defunct pathways and may improve the efficacy of enzyme replacement therapy for lysosomal disorders, such as Niemann-Pick disease.

Inhibition of Epstein-Barr-virus-transformed human chronic lymphocytic leukaemic B cells with monoclonal-antibody-adriamycin (doxorubicin) conjugates

The anthracyclin antineoplastic agent doxorubicin (Adriamycin) was linked by four different methods of linkage to DalB02, an IgG1 kappa murine monoclonal antibody (mAb) against surface-associated antigens on human chronic lymphocytic leukaemia (CLL) B cells. All the four conjugates fully retained the immunoreactivity of the parent DalB02. When the inhibitory effect of these conjugates was evaluated in vitro against the target D10-1 cells (a clone derived from an Epstein-Barr-virus-transformed human CLL B cell line that binds DalB02) it was observed that one conjugate was more potent than the free drug but the others were not. When 131I-labelled unmodified DalB02 and the 131I-labelled DalB02-containing conjugate that was found to be potent were injected i.v. into nude mice bearing a subcutaneous D10-1 xenograft, the percentages of the injected dose (%ID) of both 131I-DalB02 and the 131I-DalB02-containing conjugate that localized in the tumour were much higher than the %ID of the respective preparations that localized in normal tissues of D10-1-xenografted mice. The systemic toxicity of the conjugate was less than that of the free drug. At an equitoxic dose level, this conjugate was a more effective inhibitor of established D10-1 xenografts than the free drug.

Cure of xenografted human carcinomas by BR96-doxorubicin immunoconjugates

Immunoconjugates (BR96-DOX) were prepared between chimeric monoclonal antibody BR96 and the anticancer drug doxorubicin. The monoclonal antibody binds an antigen related to Lewis Y that is abundantly expressed at the surface of cells from many human carcinomas; it has a high degree of tumor selectivity and is internalized after binding. BR96-DOX induced complete regressions and cures of xenografted human lung, breast, and colon carcinomas growing subcutaneously in athymic mice and cured 70 percent of mice bearing extensive metastases of a human lung carcinoma. Also, BR96-DOX cured 94 percent of athymic rats with subcutaneous human lung carcinoma, even though the rats, like humans and in contrast to mice, expressed the BR96 target antigen in normal tissues.