Recent advances in the clinical application of CAR-Treg therapy in 8 autoimmune diseases

January 4, 2023 / eMedClub News/-- Regulatory T cells (Tregs) are a subset of T cells that control autoimmune reactivity in the body, accounting for about CD4+ in human peripheral blood 5%-10% of T cells, characterized by CD4, CD25, FOXP3 co-expression
.
In addition to the Tregs mentioned above, there are other Tregs with different phenotypes such as CD8 Tregs and type 1 regulatory T cells (Tr1).

Tregs can be divided into two categories: native regulatory T cells (nTregs) and induced regulatory T cells (iTregs).
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Tregs suppresses immune responses through a variety of mechanisms, including direct interaction with other immune cells to produce immunosuppressive cytokines such as IL-10 (IL-10) and transforming growth factor β (TGF-β).

As powerful suppressor cells, Tregs are able to inhibit any antigen-specific T cells through bystander inhibition, transforming conventional T cells into induced Tregs
through infection tolerance.
As a result, Tregs has been used to modulate immune responses
in transplantation, autoimmune diseases, and gene therapy.

Preclinical studies have shown that TCR-engineered Tregs rely on MHC, and mismatch hybridization of exogenous and endogenous strands limits their application, while CAR technology provides a non-MHC-dependent approach with CAR-Tregs less dependent on IL-2 than TCR-Tregs
.
At present, the expression of CAR is usually done by viral vector systems, such as lentiviruses, γ retroviruses, adeno-associated viruses, etc
.
In addition, virus-free systems such as Sleeping Beauty, piggyBac transposon, and CRISPR gene editing techniques have been applied to construct CAR.

At present, CAR-Tregs has been widely used in the treatment
of autoimmune diseases.
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▲ CAR-Tregs generation method (Source: Nexcella official website).

Graft-versus-host disease (GVHD)

GVHD is a series of "cytokine storm" stimuli launched by the recipient due to T lymphocytes in the allogeneic donor graft after transplantation, which greatly enhances its immune response
to the recipient's antigen.
Therapeutic modification of Tregs has become an important research area for GvHD, and the first clinical trials have shown that Tregs therapy significantly relieves chronic GvHD and slightly relieves
acute GvHD symptoms.
In addition, studies have shown that CD4+CD25+CD127-Tregs can prevent acute and chronic GvHD
.

The researchers then used CAR-Tregs to reprint allogeneic antigen-specific human Tregs with specific CAR for expressing HLA-A2, which maintained high expression of FoxP3, CD25, Helios, and CTLA-4 in vitro and in vivo, and in mouse experiments, HLA-A2 CAR-Tregs completely prevented rejection
of allogeneic target cells and tissues by immunorecombinant humanized mice 。 At the same time, Boardman et al.
developed a second-generation CAR-Treg targeting the same antigen HLA-A2, which showed antigen-specific inhibition without cytotoxicity in vitro, and these CAR-Tregs were able to migrate to HLA-A2-expressing cells in vivo and mitigate mouse alloimmunization-mediated skin damage
.
Following the success of HLA-A2 CAR-Tregs, researchers have set their sights on CAR-Tregs with different targeting domains, such as CD83, CD19, CD4, CD8
.

Sangamo Therapeutics is a fastest-progressing company
in the field of CAR-Tregs in the treatment of GVHD.
Its product candidate, TX200, is the first autologous CAR-Treg therapy capable of expressing HLA-A2 CAR, which, when bound to HLA-A2 antigens, reduces local inflammation and protects the graft from immune-mediated rejection, thereby preventing kidney transplant rejection
.
In March 2022, TX200 completed the first patient dosing
in a Phase 1/2 STEADFAST clinical study.
In addition, there is Quell Therapeutics working on
liver transplant rejection.

Type 1 diabetes mellitus (T1D)

T1D is an autoimmune disease characterized by the destruction of pancreatic β cells leading to insulin deficiency
.
Studies have shown that the immunosuppressive function of Tregs in T1D patients is reduced, which also provides ideas for the treatment of T1D by Tregs
.
Infusion of amplified antigen-specific Tregs has shown promising results in animal models that block and reverse diabetes, however, isolating enough antigen-specific Tregs is challenging because they are rare in circulation
.

Tenspolde et al.
created insulin-specific CAR-Tregs by transducing CD4 T cells with second-generation CAR and FoxP3 genes, which exhibit a similar phenotype to native Tregs, and whose function was demonstrated
in vitro by inhibiting the proliferation of effector T cells.
Although insulin CAR-Tregs did not prevent diabetes in NOD/Ltj mice, these cells
were found in the mouse spleen 17 weeks after the infusion.
In another study, the researchers designed a CAR-Tregs for two immunodominant GAD65β cell epitopes, and 24 hours after infusion, CAR-Tregs homed to islets in a humanized T1D mouse model, and the Tregs population of the pancreas and spleen in the CAR-Tregs treatment group was significantly increased compared to the control group, and the blood sugar of mice was also lower
.

In addition, allogeneic islet transplantation is a promising therapy
for T1D.
However, host-mediated immune rejection is a limiting factor
in the widespread use of islet transplantation.
Pilini et al.
constructed FITC-specific CAR-Tregs (mAbs CAR Treg), which prolongs the survival time of islet allografts in vivo, and these findings further indicate the potential
of CAR-Tregs to treat T1D.

Rheumatoid arthritis (RA)

RA is the most common inflammatory arthritis characterized by polyarticular, symmetrical, invasive joint inflammation of the small joints of the hands and feet, often accompanied by extraarticular organ involvement and positive serum rheumatoid factor, which can lead to joint deformity and loss
of function.
At present, Tregs treatment has shown benefits
for RA.

Wright et al.
used ovalbumin (OVA)-specific Tregs to inhibit OVA-induced arthritis, including TCR-transduced primary Tregs and TCR-FoxP3-transduced CD4 T cell-induced Tregs, both engineered Tregs exhibiting OVA-dependent inhibition by bystander inhibition
of proliferation of antigen-specific T cells 。 In vivo, both TCR-Tregs and TCR-FoxP3-induced Tregs localized to damaged tissue, reducing the number of inflammatory Th17 cells and significantly reducing arthritic bone destruction
.
In addition, Raffin et al.
constructed antigen-specific CAR-Tregs against citrulline vimentine (CV), and found that CV is abundant in the extracellular matrix of inflamed joints in RA patients
.
Currently, Sonoma Biotherapeutics is developing CAR-Tregs therapy
for RA.

Multiple sclerosis (MS)

MS is an autoimmune demyelinating and neurodegenerative disease caused by autoreactive T cells that recognize the myelin epitope
.
Treg secretes more IFN-γ and less IL-10
in MS patients compared to healthy controls.

Fransson et al.
modified CD4 T cells with CAR targeting myelin oligodendrocytes glycoprotein (MOG) and murine FoxP3 genes to induce the production of antigen-specific Tregs
.
MOG CAR-Tregs is localized to various regions of the brain after intranasal delivery, which alleviates disease symptoms in brain tissue of EAE mice and lowers pro-inflammatory cytokine mRNA
.
Currently, companies such as Abata Therapeutics and Tera Immune are developing CAR-Tregs therapies
for the treatment of MS.

Inflammatory bowel disease (IBD)

IBD is a condition characterized by chronic inflammation of the gastrointestinal tract, with ulcerative colitis (UC) and Crohn's disease (CD) being the most common forms of
IBD.
In one study, TNP CAR-Tregs transferred to a mouse model of colitis that reduced symptoms and improved survival by bystanders who suppressed oxazolidone-induced colitis
.
In addition, CAR-Tregs produced against different antigens, carcinoembryonic antigen (CEA), are effective in suppressing the severity
of colitis.

In a recent study, second-generation CAR-transduced Tregs were designed to target CD, which contains a CD28 co-stimulatory domain targeting IL-23R, which inhibits conventional T cell proliferation in vitro, homing to target organs in vivo, and reducing the risk of
intestinal inflammation.

haemophilia

Factor VIII (FVIII) and factor IX deficiency (FIX) cause hemophilia A and hemophilia
B, respectively.
Current clinical treatments for hemophilia include protein replacement therapy and gene therapy, but the former requires frequent administration and the latter is expensive
.

Researchers have begun exploring strategies
for using CAR-Tregs to treat hemophilia.
Yoon et al.
prepared from isolated Tregs to produce FVIII-specific CAR-Tregs, which inhibited the response
of B cells and T cells to FVIII.
Their data also showed that bystander inhibition by regulating the proliferation of FVIII-specific T effector cells was specific
for different FVIII domains.
In addition, multiple preclinical studies have shown that CAR-Tregs can inhibit the production of FVIII antibodies, and antigen-specific CAR-Tregs has proven to be a successful treatment
for regulating coagulation factors related.

vitiligo

Vitiligo is a skin condition
characterized by progressive skin depigmentation.
It has been reported that Tregs is impaired
in vitiligo patients.
The researchers developed a CAR-Tregs targeting ganglioside D3 (GD3), which uses GD3 to target the CAR structure to transduce CD4+FoxP3+Tregs
.
In vivo studies, animals treated with CAR-Tregs showed higher levels of IL-10, cytotoxicity to melanocytes was suppressed, and pigmentation was delayed
.

asthma

Asthma is a chronic respiratory disease that affects approximately 300 million people
worldwide.
Standard treatment for asthma includes anti-inflammatory drugs and bronchospasmolytics
.
However, 10% to 20% of patients are resistant to these symptomatic treatments
.
The study found that Tregs were impaired and reduced in number in people with asthma
.
Therefore, this finding also provides a new way of thinking
about the treatment of asthma.

To guide Tregs to target asthma-related antigens, Skuljec et al.
applied CAR technology
.
They designed a second-generation CAR-Tregs against CEA, a glycoprotein found on the surface of the lung and gastrointestinal gland epithelium, isolated from genetically modified mice and the same
antigen used in the UC study described above.
CEA CAR-Tregs was able to homing to inflamed lungs in asthmatic mice and improved inflammation
to a greater extent than Tregs.

summary

CAR-Tregs is a promising therapy
for the treatment of autoimmune diseases.
However, clinical studies of this therapy are still in the early stages and need to be further optimized to increase the inhibitory function and stability of Tregs, prevent CAR-Tregs depletion, and evaluate its safety
.
In the future, it is believed that CAR-Tregs can occupy a place
in the field of autoimmune diseases.

Recommended reading: Treg therapy: sitting on two hundred billion-level markets, foreign transactions are hot, and domestic companies are poised to take off

Resources:

1.
CAR-T Regulatory (CAR-Treg) Cells: Engineering and Applications