Vita Golubovskaya

Chimeric antigen receptor (CAR) T cell therapy has emerged as a pioneering cancer treatment, achieving unprecedented success in treating certain hematological malignancies such as lymphomas and leukemias. However, as more cancer patients receive CAR-T cell therapies, treatment-associated secondary primary malignancies are increasingly being reported partly due to unexpected CAR transgene insertion, raising serious safety concerns. To address this issue, we describe here a nonviral, non-integrating approach to generate transient CAR-T cells using mRNA. We electroporated T cells with modified mRNA encoding a human epidermal growth factor receptor 2 (HER2)-specific CAR and generated transient HER2-targeted CAR-T cells. The CAR was efficiently expressed on the T cell surface 1 day after electroporation, increased by day 2, and dramatically declined by day 5. The transient CAR-T cells exhibited potent cytotoxicity against HER2-positive SKOV-3 ovarian cancer cells and secreted high levels of IFN-ϒ. This protocol provides a step-by-step guide for developing small-scale transient CAR-T cells without permanent CAR transgene integration, describing detailed procedures for preparation of CAR mRNA, activation and transfection of T cells, assessment of CAR expression, and in vitro analysis of CAR-T cell function. This method is suitable for transient CAR-T cell generation in both preclinical and clinical studies.

Chimeric antigen receptor (CAR) T cell therapy has emerged as a pioneering cancer treatment, achieving unprecedented success in treating certain hematological malignancies such as lymphomas and leukemias. However, as more cancer patients receive CAR-T cell therapies, treatment-associated secondary primary malignancies are increasingly being reported partly due to unexpected CAR transgene insertion, raising serious safety concerns. To address this issue, we describe here a nonviral, non-integrating approach to generate transient CAR-T cells using mRNA. We electroporated T cells with modified mRNA encoding a human epidermal growth factor receptor 2 (HER2)-specific CAR and generated transient HER2-targeted CAR-T cells. The CAR was efficiently expressed on the T cell surface 1 day after electroporation, increased by day 2, and dramatically declined by day 5. The transient CAR-T cells exhibited potent cytotoxicity against HER2-positive SKOV-3 ovarian cancer cells and secreted high levels of IFN-ϒ. This protocol provides a step-by-step guide for developing small-scale transient CAR-T cells without permanent CAR transgene integration, describing detailed procedures for preparation of CAR mRNA, activation and transfection of T cells, assessment of CAR expression, and in vitro analysis of CAR-T cell function. This method is suitable for transient CAR-T cell generation in both preclinical and clinical studies.

The human epidermal growth factor receptor 2 (HER2) is a transmembrane tyrosine kinase receptor and tumor-associated antigen abnormally expressed in various types of cancer, including breast, ovarian, and gastric cancer. HER2 overexpression is highly correlated with increased tumor aggressiveness, poorer prognosis, and shorter overall survival. Consequently, multiple HER2-targeted therapies have been developed and approved; however, only a subset of patients benefit from these treatments, and relapses are common. More potent and durable HER2-targeted therapies are desperately needed for patients with HER2-positive cancers. In this study, we developed a lipid nanoparticle (LNP)-based therapy formulated with mRNA encoding a novel HER2-CD3-Fc bispecific antibody (bsAb) for HER2-positive cancers. The LNPs efficiently transfected various types of cells, such as HEK293S, SKOV-3, and A1847, leading to robust and sustained secretion of the HER2-CD3-Fc bsAb with high binding affinity to both HER2 and CD3. The bsAb induced potent T-cell-directed cytotoxicity, along with secretion of IFN-λ, TNF-α, and granzyme B, against various types of HER2-positive tumor cells in vitro, including A549, NCI-H460, SKOV-3, A1847, SKBR3, and MDA-MB-231. The bsAb-mediated antitumor effect is highly specific and strictly dependent on its binding to HER2, as evidenced by the gained resistance of A549 and A1847 her2 knockout cells and the acquired sensitivity of mouse 4T1 cells overexpressing the human HER2 extracellular domain (ECD) or epitope-containing subdomain IV to the bsAb-induced T cell cytotoxicity. The bsAb also relies on its binding to CD3 for T-cell recruitment, as ablation of CD3 binding abolished the bsAb’s ability to elicit antitumor activity. Importantly, intratumoral injection of the HER2-CD3-Fc mRNA-LNPs triggers a strong antitumor response and completely blocks HER2-positive tumor growth in a mouse xenograft model of human ovarian cancer. These results indicate that the novel HER2-CD3-Fc mRNA-LNP-based therapy has the potential to effectively treat HER2-positive cancer.

This Special Issue in Cancers, “Cell Therapy, Bispecific Antibodies and other Immunotherapies Against Cancer”, includes interesting reports and reviews on cell therapies and bispecific antibodies

Natural killer (NK) cells are cytotoxic lymphocytes that are critical for the innate immune system. Engineering NK cells with chimeric antigen receptors (CARs) allows CAR-NK cells to target tumor antigens more effectively. In this report, we present novel CAR mRNA-LNP (lipid nanoparticle) technology to effectively transfect NK cells expanded from primary PBMCs and to generate functional CAR-NK cells. CD19-CAR mRNA and BCMA-CAR mRNA were embedded into LNPs that resulted in 78% and 95% CAR expression in NK cells, respectively. BCMA-CAR-NK cells after transfection with CAR mRNA-LNPs killed multiple myeloma RPMI8226 and MM1S cells and secreted IFN-gamma and Granzyme B in a dose-dependent manner in vitro. In addition, CD19-CAR-NK cells generated with CAR mRNA-LNPs killed Daudi and Nalm-6 cells and secreted IFN-gamma and Granzyme B in a dose-dependent manner. Both BCMA-CAR-NK and CD19-CAR-NK cells showed significantly higher cytotoxicity, IFN-gamma, and Granzyme B secretion compared with normal NK cells. Moreover, CD19-CAR-NK cells significantly blocked Nalm-6 tumor growth in vivo. Thus, non-viral delivery of CAR mRNA-LNPs can be used to generate functional CAR-NK cells with high anti-tumor activity.

The epithelial cell adhesion molecule (EpCAM) is often overexpressed in many types of tumors, including colorectal cancer. We sequenced and humanized an EpCAM mouse antibody and used it to develop bispecific EpCAM-CD3 antibodies. Three different designs were used to generate bispecific antibodies such as EpCAM-CD3 CrossMab knob-in-hole, EpCAM ScFv-CD3 ScFv (BITE), and EpCAM ScFv-CD3 ScFv-human Fc designs. These antibody designs showed strong and specific binding to the EpCAM-positive Lovo cell line and T cells, specifically killed EpCAM-positive Lovo cells and not EpCAM-negative Colo741 cells in the presence of T cells, and increased T cells’ IFN-gamma secretion in a dose-dependent manner. In addition, transfection of HEK-293 cells with EpCAM ScFv-CD3 ScFv human Fc mRNA-LNPs resulted in antibody secretion that killed Lovo cells and did not kill EpCAM-negative Colo741 cells. The antibody increased IFN-gamma secretion against Lovo target cells and did not increase it against Colo741 target cells. EpCAM-CD3 hFc mRNA-LNP transfection of several cancer cell lines (A1847, C30, OVCAR-5) also demonstrated functional bispecific antibody secretion. In addition, intratumoral delivery of the EpCAM-CD3 human Fc mRNA-LNPs into OVCAR-5 tumor xenografts combined with intravenous injection of T cells significantly blocked xenograft tumor growth. Thus, EpCAM-CD3 hFc mRNA-LNP delivery to tumor cells shows strong potential for future clinical studies.

The fundamental problem of dealing with cancer is that cancer cells are so like normal cells that it is very hard to find differences that can be a basis for treatment without severe side effects. The key to successful cancer immunotherapy will be based on a very careful choice of cancer targets that are sufficiently cancer specific not to cause serious side effects. There are two fundamentally different ways to deploy the immune system for such cancer treatments. One is to increase the efficacy of the cancer patient’s own immune system so that it attacks these differences. This has been achieved by “checkpoint blocking” which is very successful but only with a relatively small proportion of cancers. Secondly, one can produce antibodies, or T cells, whose specificity is directed against proteins expressed differentially in cancers. CART cell treatments have proved very effective for some blood cancers but not so far for common solid tumours. Humanised, unmodified monoclonal antibodies have been used extensively for the treatment of certain adenocarcinomas with modest success. However, using antibodies together with the body’s own immune system to treat cancers by engineering monoclonal antibodies that are directed at both a target antigen on the cancer cell surface and also against T cells shows promise for the development of novel immunotherapies. Genes can be found which are expressed highly in some cancers but with a low or absent expression on normal tissues and so are good novel targets. It is so far, only immune-based killing that can kill bystander target negative cells, which is essential for successful treatment since hardly ever will all the cells in a cancer express any desired target. We conclude that, while there still may be many hurdles in the way, engineered bispecific T cell attracting monoclonal antibody-mediated killing of cancer cells may be the most promising approach for achieving novel effective cancer immunotherapies.

BCMA antigen is overexpressed in multiple myeloma cells and has been shown to be a promising target for novel cellular and antibody therapeutics. The humanized BCMA (clone 4C8A) antibody that effectively targeted multiple myeloma in a CAR (chimeric antigen receptor) format was used for designing several formats of bispecific BCMA-CD3 antibodies. Several different designs of univalent and bivalent humanized BCMA-CD3 CrossMAB and BCMA-FAB-CD3 ScFv-Fc antibodies were tested for binding with BCMA-positive cells and T cells and for killing by real time cytotoxic activity and IFN-gamma secretion with CHO-BCMA target cells and with multiple myeloma MM1S and H929 cell lines. All BCMA-CD3 antibodies demonstrated specific binding by FACS to CHO-BCMA, multiple myeloma cells, and to T cells with affinity Kd in the nM range. All antibodies with T cells specifically killed CHO-BCMA and multiple myeloma cells in a dose-dependent manner. The BCMA-CD3 antibodies with T cells secreted IFN-gamma with EC₅₀ in the nM range. In addition, three BCMA bispecific antibodies had high in vivo efficacy using an MM1S xenograft NSG mouse model. The data demonstrate the high efficacy of novel hBCMA-CD3 antibodies with multiple myeloma cells and provide a basis for future pre-clinical and clinical development.

CAR (Chimeric antigen receptor)-T cell therapy has become a very promising type of immunotherapy against hematological cancers. This report is focused on CAR-T cells targeting immune checkpoint proteins expressed on tumor cells. The CD70, CD47, CD80, CD86, B7H3, B7H4, PDL-1, TIGIT CAR-T cells and other CAR-T cells are discussed as an effective approach to deplete tumor cells expressing checkpoint proteins. CAR-T cell therapy targeting checkpoint pathways is a promising therapy to decrease inhibitory signaling pathways. The review highlights future directions and perspectives in CAR-T cells targeting immune checkpoint pathways.

Recently, novel types of immunotherapies such as CAR-T cell therapy demonstrated efficacy in leukemia, lymphoma, and multiple myeloma