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Cell-based cancer immunotherapies

Cell-based cancer immunotherapies

Curing patients suffering from metastatic forms of cancer is rare. The introduction of cell-based cancer immunotherapies has dramatically improved the situation. In these immunotherapies, patient-selected or specifically modified cells are used. Their application, even in patients where cancer no longer responds to other forms of treatment, can lead to long-lasting complete cancer remission.

We plan to introduce four forms of cell-based cancer immunotherapies, i.e.,
a) CAR (chimeric antigen receptor) T-lymphocytes,
b) tumor of infiltrating lymphocytes (TILs) specific for tumor antigens,
c) tumor vaccines, and
d) oncolytic viruses.

We'll aim to give these immunotherapies quickly and at minimal cost to all patients in need. Treatment with CAR T-lymphocytes gave excellent results in certain B-cell leukemia or lymphoma subgroups. Additionally, in a case report of treatment-resistant metastatic breast cancer TILs treatment led to the complete and durable disappearance of any sign of tumor. It was also shown that tumor vaccines prolong survival in patients with prostate and lung cancer and oncolytic viruses in patients with glioblastoma.

Lymphocyte activation and the mechanisms of cell-based cancer immunotherapy

The executive functions of immune cells are performed in direct cell contact, as shown in the picture below. T lymphocytes (smaller purple bodies) recognize tumor cells.

Recognition of antigens on the surface of tumor cells or specialized antigen-presenting dendritic cells elicits their activation, which results in the secretion of various cytokines or their executive functions (assistance in the activation and differentiation of other cells for helper T lymphocytes or killing of target cells for cytotoxic T lymphocytes).

Cytotoxic T lymphocytes, by releasing cytotoxic granules, lead to the death of the target cell, e.g., virus-infected or tumor cells. This is a unique form of cell death called apoptosis. An important feature of apoptotic cell death is that it can result in the repair of damaged tissue without inflammatory reactions and associated side effects.

lymphocytes

A whole range of receptors participates in T lymphocytes' antigen recognition and activation. T cell receptor recognizes a specific antigenic peptide associated with molecules of the major histocompatibility complex on antigen-presenting cells or, for example, on the surface of tumor cells. This recognition triggers signal transduction cascades that activate the T lymphocyte.

However, this process can be either inhibited or further stimulated by interactions with inhibitory or activating receptors. The function of T lymphocytes is inhibited, for example, by the interaction of PD-1 and CTLA-4 receptors on the surface of T lymphocytes with their PD-L1 and B7-1 ligands on the surface of antigen-presenting cells. In contrast, the interaction of CD28 with its ligand increases the activation of T lymphocytes.

Lučenje citokina

Tumors inhibit the anti-tumor immune responses by exposing inhibitory receptors on their surface. The possibility of using antibodies to these receptors to prevent their interaction with receptors on the surface of T lymphocytes has been used to activate the anti-tumor immune response and introduce a particular form of immunotherapy called control checkpoint inhibitors. This revolutionized the treatment of multiple forms of solid tumors. James P. Allison and Tasuku Honjo were awarded the Nobel Prize in Physiology or Medicine in 2018 for that discovery.

Antigen prezentirajuća stanica

Further progress in tumor immunotherapy has been achieved by creating the so-called chimeric antigen receptor (CAR). By linking an antigen recognition domain (typically a single-chain variable fragment - ScFv) with a signal-transmitting domain, it is possible to specifically redirect the immune response toward the tumor cells, which ultimately leads to the death of the tumor cell.

Inhibirani odgovor t limfocita na tumor
Domena za prepoznavanje

CAR enables the recognition of tumor cells and the release of cytotoxic granules leading to the death of the tumor cell. A genetically modified virus encoding a chimeric antigen receptor transduces the CAR gene into a T lymphocyte, leading to its integration into the genome and the exposure to CAR at the surface of T lymphocytes. The process of creation and mechanism of action of CAR T-cells is schematically shown in the following figure.

Stvaranja i mehanizam djelovanja CAR t-stanica

CAR T-lymphocytes for patient treatment must be manufactured in accordance with strict requirements for their effectiveness and quality. The effectiveness is proven by analyzing CAR's exposure on the surface of transduced T lymphocytes and by examining the specific killing of target cells. A series of tests such as sterility, receptor copies number, apyrogenicity, osmolarity, and the absence of other viruses and mycoplasmas demonstrate quality.

The process of preparing CAR T-cell preparations begins with a process called leukapheresis. In this procedure, nucleated cells are extracted from the peripheral blood using a machine while all other blood components are returned to the patient (plasma, erythrocytes, platelets, etc.). T lymphocytes are isolated from extracted cells and reprogrammed by exposure to genetically modified viruses with CAR. These T lymphocytes are then expended under appropriate conditions to obtain a sufficient number for application to the patient.

Proizvodnja CAR t-staničnog pripravka

CD19 is expressed on the surface of normal B cells and the surface of several types of B cell leukemia and lymphoma. CD19 CAR T-cells kill these cells very efficiently, and in up to 90% of patients, lead to a clinical response or complete disappearance of any signs of the disease. Unfortunately, with time in a significant number of patients, there is a recurrence of the disease due to the appearance of malignant cell variants that no longer expose the target CD19 antigen on the surface or its level is significantly reduced. The loss or reduction of CD19 expression prevents the recognition and killing of such cells.

t-limfocit tumorska stanica

To reduce the relapse of the disease, CAR that simultaneously recognizes two or more targets on the same tumor cell was produced. An example of such dual CAR CD19/CD20 is shown in the following figure.

t-limfocit tumorska stanica

We plan to introduce these advanced forms of CAR T-cell therapies to dramatically improve cancer patients' outcomes.

The possible benefits of locally produced CAR T-cell therapies are numerous and include the following:
Significant cost reduction,
Possible higher effectiveness of treatment since the cellular preparations will not undergo freezing and thawing cycles,
Significantly faster treatment access than with the commercial preparations,
The availability of new, improved forms of CAR T-lymphocytes,
Creation of own forms of CAR T-cell therapies,
Introduction of treatment of CAR T-lymphocytes in new indications such as other forms of leukemia, solid tumors, and autoimmune diseases.