CAR-T cell therapy, originally developed for the treatment of hematologic cancers, has proven to be a revolutionary approach in oncology. Its impressive success in fighting cancer cells has sparked interest in its application to other immune-mediated diseases, including rheumatic diseases.
Basics of CAR-T cell therapy
CAR T-cell therapy (Chimeric Antigen Receptor T-cell Therapy) is based on the genetic modification of the patient's T-cells in order to target them against specific antigens. This is achieved by introducing a chimeric antigen receptor (CAR), which enables a targeted immune response against cells with the corresponding antigen.
- Production of CAR-T cells:
- Extraction and modification: T cells are extracted from the patient's blood and genetically modified outside the body to give them special receptors (CARs). This process involves filtering out the T cells, introducing the CAR gene using a virus and then multiplying the modified cells.
- Expansion and infusion: The modified T cells are expanded in vitro to obtain a sufficient quantity of CAR T cells, which are then reinfused into the patient.
- Mechanism of CAR-T cells:
- Targeted destruction: The CAR-T cells recognize and bind specific antigens on the target cells, which leads to the activation and destruction of these cells. This mechanism is based on the specific binding of the CAR to the target antigen, which triggers a strong cytotoxic reaction that leads to the lysis of the target cells.
Potential of CAR-T cell therapy in rheumatology
Rheumatic diseases are characterized by a dysregulation of the immune system that leads to chronic inflammation and tissue damage. CAR-T cell therapy offers several potential advantages:
- Targeted immunomodulation: Through specific modification, CAR-T cells can be programmed to recognize and eliminate autoreactive B or T cells that play a role in rheumatic diseases. This enables precise treatment that directly targets the pathogenic cells and largely spares healthy tissue.
- Long-lasting effects: In contrast to conventional therapies that need to be administered regularly, CAR-T cells could enable long-term control of the disease by eliminating persistent autoreactive cells. This could lead to a lasting remission and reduce the need for continuous medication.
- Personalized therapy: CAR T-cell therapy can be individually tailored to the patient, enabling precise and effective treatment. By adapting the CAR constructs to the patient's specific antigens, a high level of specificity and efficacy can be achieved.
Use for specific rheumatic diseases
Rheumatoid arthritis (RA):
- Mechanism and target structures: Rheumatoid arthritis is characterized by chronic inflammation of the joints, which leads to joint destruction. The modification of T cells to target B cells expressing the antigen CD19, which plays a role in RA, is a promising approach. Preclinical models show a reduction in disease symptoms and activity through the specific elimination of these B cells.
- Research results: There is preclinical data on a novel CAR-Treg therapy developed specifically for the treatment of RA. This therapy targets citrullinated proteins found in the joints and blood of RA patients. Preclinical study results show that these CAR-Treg cells can recognize pro-inflammatory proteins in the synovial fluid and serum of RA patients and potentially reduce inflammation at its source. A phase 1 trial to further evaluate this therapy is scheduled to begin in early 2024.
Systemic Lupus Erythematosus (SLE):
- Mechanism and targets: SLE is a systemic autoimmune disease characterized by the production of autoantibodies against cell nuclei and other intracellular antigens. CAR-T cells that target specific autoantigen-presenting B cells could reduce the production of these autoantibodies.
- Research results:
- A Phase I study investigated the safety and preliminary efficacy of CD19/BCMA CAR-T cells in patients with refractory SLE. The results showed that the treatment achieved deep B-cell depletion, leading to a significant reduction in disease activity. All treated patients developed transient, manageable side effects such as fever, and there were no serious neurological side effects.
- Another study in 15 patients, including 8 with severe SLE, showed that a single infusion of CD19 CAR-T cells can lead to complete remission of disease symptoms. These patients experienced sustained improvement, and some were even able to avoid all SLE-specific medications. The researchers see the potential for long-lasting, drug-free remission, although further studies are needed to confirm these results.
These promising results make CAR-T cell therapies a potentially groundbreaking treatment for patients with systemic lupus erythematosus who do not respond to conventional therapies.
Systemic sclerosis (SSc):
- Mechanism and targets: Systemic sclerosis is characterized by excessive formation of connective tissue and fibrosis, which leads to hardening of the skin and internal organs. CAR-T cells could help eliminate the aberrant immune cells that contribute to fibrosis.
- Research results:
- A phase 1 and 2 study by Cabaletta Bio is investigating the efficacy and safety of CABA-201, a CAR-T cell therapy targeting CD19. This trial is being conducted in patients with severe systemic sclerosis who continue to have severe skin or organ involvement despite immunosuppressive drugs. Initial results show that the treatment was well tolerated and has the potential to slow or halt disease progression. The therapy led to a reduction of disease-causing B cells in the body, which led to a stabilization of disease activity.
- In addition, data from three patients with diffuse systemic sclerosis who received CD19 CAR-T cell treatment were published. These patients showed improvement in skin symptoms, hand function and lung function after six months without the need for additional immunosuppressants. The treatment was well tolerated and B-cell depletion persisted for several months before returning with no new disease activity.
These results suggest that CAR-T cell therapies may represent a promising new treatment option for patients with systemic sclerosis, particularly those who do not respond to conventional therapies. However, further studies are needed to confirm the long-term efficacy and safety of these therapies.
Current risks and challenges
Despite the promising approaches, there are also challenges and risks associated with the use of CAR-T cell therapy in rheumatology:
- Security concerns:
- Cytokine release syndrome (CRS): Overactivation of the immune system can lead to severe side effects, including fever, hypotension and organ failure. CRS is a common and potentially life-threatening complication of CAR-T cell therapy that requires careful monitoring and management.
- Neurotoxicity: Some patients may develop neurological side effects such as confusion, seizures and encephalopathy. The mechanisms underlying these side effects are not yet fully understood and further research is needed to develop strategies to prevent and treat these complications.
- Autoimmune reactions: Non-specific attacks on healthy tissue must be avoided in order to prevent unwanted autoimmune reactions. This requires careful selection of target antigens and the development of safety mechanisms, such as "suicide genes", which can deactivate the CAR-T cells if necessary.
- Complexity and cost: The production and administration of CAR-T cells is technically demanding and expensive, which limits their widespread use. The cost of manufacturing, storing and administering the therapy is high, which can limit access for many patients. In addition, the therapy requires specialized facilities and personnel, which further limits availability.
- Long-term effects: Long-term data on safety and efficacy are still lacking. It is unclear how long the therapeutic effects will last and whether late side effects may occur. Monitoring of patients over a longer period of time is necessary to identify and assess potential long-term risks. This also includes the investigation of possible secondary malignancies or undesirable immunological effects.
Future prospects
The further development of CAR-T cell therapy in rheumatology is being driven by several approaches:
- Improved CAR designs: New designs could increase the specificity and safety of CAR-T cells, for example by using dual target structures or responding to inhibitory signals. These improvements could increase efficacy and reduce the risk of unwanted side effects. Examples include "switch" CARs, which are only activated in the presence of certain molecules, and "universal" CARs, which can be controlled by exogenous ligands.
- Combination therapies: Combining CAR-T cells with other immunomodulatory therapies could have synergistic effects and increase efficacy. This could also help to reduce the required dose of CAR-T cells and thus reduce costs and the risk of side effects.
- Regulatory and ethical aspects: Close monitoring and adaptation of regulatory guidelines are necessary to ensure the safety and accessibility of these therapies. This includes the development of ethical guidelines for the use and research of CAR-T cell therapies in rheumatology.
