by Josep Carreras Leukaemia Research Institute
Comparative in vitro study of engineered CD1a-STAb and CD1a-CAR T cells. (A, B) Schematic diagrams showing the genetic (A) and domain structure (B) of the CD1a-TCE bearing a signal peptide from the human κ light chain signal peptide (S, gray box), the anti-CD1a scFv gene (orange boxes), the anti-CD3 scFv gene (blue boxes), and the Myc and his tags (light yellow box). (C, D) Schematic diagrams showing the genetic (C) and domain structure (D) of the CD1a-CAR bearing the CD8a signal peptide (S, gray box), the anti-CD1a scFv gene (orange boxes), followed by the human CD8 transmembrane domain and the human 4-1BB and CD3ζ endodomains. CD1a-TCE and CD1a-CAR constructs were cloned into a pCCL lentiviral-based backbone containing a T2A-enhanced green fluorescent protein (GFP) cassette (A, C). (E, F) Percentage of reporter GFP (E) and F(ab’)2 (F) expression in CD1a-CAR and CD1a-STAb T cells. One representative transduction out of four independent transductions performed is shown. Numbers represent the percentage of cells staining positive for the indicated marker. (G, H) Percentages of CD4+ and CD8+ T cells (G) and percentages of naïve (TN), effector memory re-expressing CD45RA (TEMRA), central memory (TCM), and effector (TEM) T cells (H) among non-transduced (NT), or CD1a-CAR and CD1a-STAb transduced T cells. (I) Specific cytotoxicity of NT, CD1a-CAR or CD1a-STAb T cells toward CD1a negative (NALM6) or CD1a positive (MOLT4) cells at the indicated E:T ratios after 24 hours. (J) Alive primary cells from three different coT-ALL patients (P1, P2, P3) after 24 hours co-culture at a 1:1 E:T ratio with NT, CD1a-CAR or CD1a-STAb T cells. (K) Specific cytotoxicity of NT, CD1a-CAR or CD1a-STAb T cells toward NALM6 or MOLT4 cells at 1:4 E:T ratio after 2 and 4 hours. (L) Real-time cell cytotoxicity assay with HEK293TCD1a target cells co-cultured with NT, CD1a-CAR or CD1a-STAb T cells at the indicated E:T ratios. Cell index values were determined every 15 min for 80 hours using an impedance-based method. Data from (G–L) is shown as mean±SEM of at least three independent experiments by triplicates (n=9). (M) Cartoon depicting target cell death induction by FasL and perforin/granzymes, and how these pathways can be blocked using anti-Fas mAb or EGTA, respectively. (N) Cytotoxicity of MOLT4 cells at 2 and 4 hours (E:T ratio 1:1) and at 24 hours (E:T ratio 1:4) in the presence or absence of anti-Fas mAb or EGTA. Plots show mean±SEM of two independent experiments with triplicates (n=6). Statistical significance was calculated by one-way (L) or two-way (G–K, N) ANOVA test corrected with a Tukey’s multiple comparisons test (*p<0.05; **p<0.01; ***p<0.001, ****p<0.0001). ALL, acute lymphoblastic leukemia; ANOVA, analysis of variance; CAR, chimeric antigen receptor; E:T, effector:target; STAb, secreting T cell-redirecting antibodies. Credit: Journal for ImmunoTherapy of Cancer (2022). DOI: 10.1136/jitc-2022-005333
Researchers of the Hospital Universitario 12 de Octubre in Madrid and the Josep Carreras Leukaemia Research Institute in Barcelona have developed a cell therapy for a type of leukemia which currently has very few treatment options. This STAb therapy is based on STAb-T cells and could be used for the treatment of T-Cell Acute Lymphoblastic Leukemia (T-ALL) in those patients for whom chemotherapy or bone marrow transplantation have not worked.
STAb-T therapy is an evolution of the so-called CAR-T therapies that are currently revolutionizing cancer treatment. CAR-T therapies are based on the modification of the patient’s own immune cells, the T-lymphocytes, so that they are able to express artificial chimeric receptors that recognize and eliminate tumor cells.
The advantage of the STAb therapy over CAR-T therapy is that, while in the latter the T cell expresses a receptor with a monospecific antibody capable of recognizing one target on the tumor; the STAb therapy is based on the secretion of a special type of bispecific antibody that can recognizes two targets, one on the tumor cell and one on the T cell. In this way, the bispecific antibodies create a kind of artificial bridge that brings therapeutic T cells into contact with tumor cells, facilitating the elimination of the latter and keeping healthy T cells safe.
This distinction is essential in order to treat T-Cell Acute Lymphoblastic Leukemia. In the case of B-Cell Acute Lymphoblastic Leukemia (B-ALL), CAR-T cells recognize a single target and destroy both diseased and healthy B cells, although these patients can lead a normal life thanks to the regular supply of immunoglobulins—antibodies—obtained from healthy donors.
In T-ALL it is more difficult to apply CAR-T therapy, since the cells used to fight the tumor—T-lymphocytes—are the same ones that are diseased and their use can lead to a state of immunodeficiency that is incompatible with life. Moreover, there is no replacement therapy available, as is the case with B-cell leukemias.
T-Cell Acute Lymphoblastic Leukemia is a rapidly progressive type of leukemia resulting from the abnormal proliferation of T-cell lymphoblasts (immature white blood cells) in the bone marrow and blood. It is a so-called rare disease that accounts for about 10–15% of all acute leukemias diagnosed in children and 20–25% of those affecting adults. In total, approximately 100 cases are detected each year in Spain.
Therapeutic innovation at 12 de Octubre Hospital
STAb-T therapy for the treatment of T-ALL was created by the Joint Cancer Immunotherapy Clinical Research Unit of the Hospital Universitario 12 de Octubre and the Spanish National Cancer Research Center (CNIO), and led by Dr. Luis Álvarez-Vallina and the team of the Josep Carreras Leukaemia Research Institute, Dr. Pablo Menéndez and Dr. Diego Sánchez-Martínez. This therapy could be an improvement over CAR-T, especially in relapsed patients with a reduced number of normal T lymphocytes.
In the paper “Efficient preclinical treatment of cortical T cell acute lymphoblastic leukemia with T lymphocytes secreting anti-CD1a T cell engagers,” published in Journal for ImmunoTherapy of Cancer, researchers Anaïs Jiménez-Reinoso, Néstor Tirado and other members of the team have shown that STAb-T cells work very efficiently both in vitro and in vivo animal models. Different options are currently being considered to bring this therapy to clinical trials.
Immunotherapy strategies and adoptive cell therapies still benefit few patients. “It is necessary to develop strategies addressed to very specific targets for each disease and adapted for each patient,” explains Dr. Alvarez-Vallina. In his opinion, “the future in cancer and leukemia research lies in the creation of personalized therapies that provide options for all those who today find no alternative to conventional therapies. STAb-T therapy is on this path.”
Dr. Alvarez-Vallina concludes, “In the case of CAR-T, many hospitals are like a production center of the therapy. Regarding STAb-T cells, this is a completely new therapy that has arisen at the Hospital Universitario 12 de Octubre and represents an innovation in the field of cell therapies.” It is important to note that STAb-T therapy can be applicable to multiple types of cancer and some of these modalities are in clinical development.
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