Inserting Genes into CAR T Cells

Chimeric Antigen Receptor T cell (CAR T) therapy genetically alters a patient’s T cells to recognize cancer cells and subsequently kill them. This engineered recognition relies on hybrid T cell receptors with antibody components to detect antigens, or biological tags, found on the surface of cancer cells (see Figure 1).

Researchers typically incorporate hybrid receptor genes into a CAR T cell via viral gene insertion. Despite its regard as a staple in cell therapy, retroviral gene transfer comes with several drawbacks. Viral vector manufacturing is expensive and time-consuming. The method lacks precision and could potentially allow an unwanted gene entry. Perhaps most limiting, it cannot be personalized to detect uncommon antigens. For this reason, all approved CAR T therapies in circulation target blood cancers that share a common antigen (usually CD19 or BCMA) rather than solid tumors, which greatly vary in antigen presentation. Standardizing a new means to insert genes would improve the accessibility, efficiency and usage of CAR T therapy.

Innovating with CRISPR Gene Editing 

In their Phase I clinical trial, the researchers at PACT Pharma and the University of California, Los Angeles explore the possibility of a different type of CAR T therapy—one that creates a hybrid receptor with CRISPR gene editing. With CRISPR, the team selectively removed native T cell receptor genes and replaced them with new, cancer-fighting alternatives.

The researchers began by searching and isolating a novel T cell receptor from the patient’s own immune system. First, they screened the patients by sequencing DNA from healthy blood samples and tumor biopsies; this step identified mutations which the tumor cells share but cannot be found in normal tissue. Algorithms then predicted which antigens would be present on the tumor.

Next, the team copied the antigens and mixed them with different versions of HLA, a type of molecule needed to present antigens to T cells. This process revealed specific T cells which could react to this particular combination of antigen-HLA. Researchers copied up to three of the highly personalized receptor genes to be integrated into the T cells using CRISPR/Cas9.

Figure 2 illustrates the subsequent process. The CRISPR/Cas9 interface knocked out two T cell receptor genes, TRCα and TRCβ (see Figure 3), and replaced them with three new receptor genes in a single step—decidedly more efficient than sourcing and cultivating retroviruses for gene transfer, as is currently standard in CAR T therapy.

The researchers multiplied the T cells to great numbers. Finally, the patients underwent lymphodepletion chemotherapy before receiving up to three doses of their personalized CRISPR/CAR T cell infusion.

The post Teaming Up Two Biotech Winners to Fight Cancer: CRISPR and CAR T appeared first on Medika Life.

CAR T Therapy and Toxic Side Effects

Chimeric Antigen Receptor T cell (CAR T) therapy entails extracting, modifying and increasing one’s own immune cells to counter cancer. While white blood cells cannot effectively attack cancer cells on their own, with genetic modification these T cells obtain a new receptor which can target antigen CD19, a biological tag found on the surface of cancerous and noncancerous B cells. The modified T cells, primed with new chimeric receptors and expanded to large numbers, can then bind and kill cancer cells once infused into the body (see Figure 1). Figure 2 describes the design of the CAR T cell in more detail.

The beauty of CAR T therapy lies in its ability to treat difficult blood cancers such as lymphoma, leukemia and multiple myeloma. These B cell cancers become resistant or unresponsive to previous lines of treatment—typically chemotherapy, targeted drug therapy, or radiation therapy. When these options are exhausted, CAR T cells attack the cancer anew and can even linger in the body to provide longer-term protection.

#1 Major Side Effect: Cytokine Release Syndrome (CRS) 

This health innovation can come with a price. Almost all CAR T patients experience a side effect known as cytokine release syndrome (CRS) or cytokine storm syndrome (CSS). As a result of CAR T cells continually stimulating the immune system, white blood cells may release inflammatory chemicals called cytokines. The cytokines can activate other white blood cells and perpetuate a cycle of inflammation.

The widespread inflammation manifests a gamut of symptoms ranging from mild to life-threatening. Mild to moderate symptoms include fluctuating fever, fatigue and muscle/joint pain. More severe cases experience low blood pressure and oxygen levels which can result in organ failure and death.

Cytokine release syndrome can usually be reversed within five to 17 days with treatments such as antihistamines, oxygen therapy or immunosuppressive medicines  as needed.

#2 Major Side Effect: Neurotoxicity 

CAR T therapy can also cause neurotoxic effects alongside cytokine release syndrome. Referred to as immune effector cell-associated neurotoxicity syndrome (ICANS), this potentially life-threatening complication impacts cognitive function—likely due to cytokines disrupting the blood-brain barrier.

Common symptoms include confusion, tremors, and hallucinations. Symptoms can escalate, albeit more rarely, to delirium, seizure or coma. Supportive care can resolve these neurotoxic side effects within 21 days of CAR T therapy.

Why and How to Make the “Switch”

Although the negative effects of CAR T therapy can be reversed, the risk of fatality raises questions on possible ways to control the treatment. If CAR T cells could pause or mobilize when prompted, this could prevent complications from worsening; once side effects have stabilized, cancer-fighting activity could restart again.

CAR T “Switch” Design 

Akin to a switchblade, researchers have developed a method to manipulate CAR T cells on and off to produce more precise results by using an antibody switch.

Traditional CAR T therapy alters T cells to detect the cancer cell directly. Rather than the cancer cell, switchable CAR T cells (sCAR T) target the antibody switch. As seen in Figure 3, the switch acts as a bridge, binding to the switchable CAR T cell on one side and the cancer cell on the other to trigger a cytotoxic response.

Figure 4 highlights the deviations from typical CAR T design. Researchers create the molecular switch by grafting a region called a peptide neoepitope (PNE) onto an anti-CD19 antibody clone; the protein neoepitope does not naturally occur in humans, making it a clear target for the therapy. Unlike traditional CAR T cells, sCAR T cells do not target CD19 but the peptide neoepitope on the switch. The desired response is therefore controlled in vivo by the presence and dosage of the switch.

Results 

Calibr, the nonprofit translational research institute of Scripps Research, recently reported preliminary results from their sCAR T clinical trial. The Phase I study tested the safety and optimal dosage of their sCAR T treatment on nine patients with B cell malignancies. The participants underwent a median of five prior treatments for their condition.

Of the nine participants, seven responded to the therapy (78%) and six experienced a complete response (67%), meaning all detectable signs of cancer disappeared. A single infusion of CAR T cells and a single injection of molecular switches elicited most responses in participants, while further switch injections hinted at deepening responses over time. The lower dosing seemed to achieve promising early results, with some doses reaching higher amounts of CAR T cell in the peripheral blood over the first 90 days than other approved CAR T therapies.

Importantly, the switchable therapy successfully minimized adverse side effects. Cytokine release syndrome and neurotoxicity associated with CAR T therapy typically resolves within five to 17 days when treated traditionally. However, by holding or reducing the switch dosage after observing early signs of side effects, the CAR T cells could essentially halt their activity; as a result, the patients experienced side effects for a shorter duration of time (between two to three days).

The Future of sCAR T 

The future of CAR T therapy continues to brighten. The early study result from Scripps Research suggests that switchable CAR T cells are not only safe to use for patients with B cell cancers, but comparatively safer and more effective than some CAR T therapies currently on the market. This also bolsters confidence in the universal molecular switch design. Using this basis, CAR T therapy could likely target any therapeutic antigen by altering the molecular switch. Further down the line, perhaps mRNA and sCAR T technology could combine to create the most ideal form of CAR T therapy—one that forgoes the lab entirely to create a potent and controllable “living drug” inside the body.

The post Researchers Control Cancer Treatment With New Innovation: CAR T Switch(Blade) appeared first on Medika Life.

CAR T therapy, a “living drug,” traditionally involves isolation and purification of T cells outside the body. The cells are then modified with a synthetic receptor and then re-infused into the body for treatment of cancers. Researchers have now successfully demonstrated that T cells can be modified in vivo by mRNA technology, bypassing the need for extraction, chemotherapy and re-infusion. Although this method proves effective in treating mice with scarred hearts, considering fibrosis contributes to over 800,000 deaths worldwide, the study contains great potential for human treatment.

A Damaged Heart 

The heart, flexible yet strong, circulates blood through the body by pumping blood through its chambers. Aging and injury tamper with this function, creating scarred and thickened tissue called fibrosis. Although fibrosis occurs normally when healing, a highly fibrotic heart loses its elasticity; the stiffened tissues and interrupted electrical signaling prevent proper contractions of the heart (see Figure 1). Cardiac fibrosis is highly associated with heart disease and heart failure.

Cardiac fibrosis has no “cure-all” treatment. Early detection improves prognosis, but options dwindle as damage progresses irreversibly. People with advanced cardiac fibrosis may take drugs which antagonize overstimulation of the heart or might even require heart valve replacement.

How CAR T Cells Work

In their study, Rurik et al. explore a new method to directly counter cardiac fibrosis. This method builds upon the basics of CAR T: the use of T cells with a synthetically engineered receptor to target and kill specific cells.

CAR T is approved to treat people with certain lymphomas, leukemias, and multiple myeloma. Figure 2 illustrates this process. In these cases, the desired T cells are extracted from the patient’s body. Synthetic mRNA is inserted into the cell with a retrovirus, a virus commonly used in gene therapy to permanently change other cells’ genomes. The altered and expanded cells are then infused back into the body after preparatory chemotherapy. These T cells target either CD19 or BCMA, two antigens found on malignant B cells.

The benefit of inserting genetic information with a retrovirus lies in its permanence. The CAR T cells can expand and persist in the body for a long time after infusion, continually fighting the cancerous cells they encounter. However, this is of no benefit to researchers hoping to fight cardiac fibrosis. If T cells continuously target fibrotic cells, they would impair normal healing processes and potentially induce autoimmunity. Rurik et al. employ an elegant solution which shortens the CAR T cells’ active duty, thereby circumventing the extraction process altogether.

 New CAR T Cell Design 

The team adapted mRNA delivery technology seen in current COVID-19 vaccines and applied it to basic Chimeric Antigen Receptor design. The mRNA does not integrate into the T cell genome, allowing for temporary transcription of the mRNA and transient expression of the new receptor.

CD5 Lipid Nanoparticles (LNP) 

The authors adopted a strategy to introduce the chimeric receptor to T cells in the body rather than extracting and purifying them outside the body. To accomplish this aim, they first synthesized mRNA that encodes a receptor against fibroblast activation protein (FAP), a protein expressed on activated fibroblasts responsible for fibrosis. They purified the mRNA and packaged the engineered mRNA into standard lipid nanoparticles (LNP).

The team then decorated the lipid nanoparticle surface with CD5 targeting antibodies to direct lipid uptake. The integration of CD5 antibodies allowed the lipid nanoparticles to target antigen CD5 naturally expressed by T cells once injected into the body; the CAR T cells are made after a single shot.

Chimeric Antigen Receptor 

The chimeric antigen receptor contains a single chain variable fragment (scFv) derived from fibroblast activation protein monoclonal antibodies; this recognition domain enables the CAR T cell to target cells which express fibroblast activation protein. The CAR design also includes CD28 and CD3z signaling domains in the cytoplasm. All three components are mouse-specific. Not illustrated in Figure 3 is an added small peptide which prevents immune suppression.

Genetic Integration In Vivo

The team found that lipid nanoparticles could successfully deliver the mRNA package to T cells, as seen in Figure 4. The killer T cell absorbs the lipid nanoparticle by endocytosis. The lipid particle then degrades and the synthetic mRNA releases into the cell. Finally, the cellular machinery reads the genetic instruction and briefly produces the receptor against fibroblast activation protein. This is possible with both animal and human T cell cultures.

Transitory CAR Expression 

Unlike traditional CAR T cells that carry a chimeric receptor encoded by DNA inserted into the genome, these CD5+ T cells carry mRNA only transiently. The mRNA is not integrated into the cell’s genome and remains stuck in the T cell cytoplasm before degrading. This is ideal; fibroblast activation protein receptors must be expressed briefly as longer expression may harm other tissues.

 Results 

The research team assessed the efficacy of the CAR T cells in different conditions. When they treated the cells in tissue culture, more than 80% of T cells expressed the chimeric antigen receptor and could effectively kill target cells with fibroblast activation protein.

The team then tested this model on mice with cardiac fibrosis. The mice received medication to injure the heart and induce scarring. After one week, the team administered the lipid-mRNA injection. Consistent CAR expression was noted 48 hours after injection, and disappeared after one week.

The results were impressive. The function of the heart’s largest chamber improved, in some cases returning to uninjured levels. Similarly, the amount of blood filling the heart normalized to safe volumes. The therapy notably reduced the thickness of the heart. Finally, although the mass of the largest chamber did not normalize, it trended towards improvement.

One caveat in lipid-CAR T cell delivery is that some cells, perivascular fibroblasts, do not express fibroblast activation protein. In consequence, these cells were not impacted by CAR T cells and some fibrosis persisted. No overly toxic side effects were noted.

Trogocytosis

A key observation of effective CAR T therapy is the ability of the modified T cells to take small bites of the target cell—a phenomenon known as trogocytosis. Deriving “trogo” from the Greek word “to bite,” trogocytosis entails one cell nibbling another and, in the process, transferring the surface molecules from one to the other. The researchers found evidence of CAR T cells “nibbling” the activated fibroblasts and retaining the stolen antigens (illustrated in Figure 5), suggesting that the T cells successfully adopted the chimeric antigen receptors in vivo.

Future Implications

CAR T therapy revolutionized cancer treatment with its efficacy and innovation. Combining mRNA technology to this therapy creates a temporary version of this “living drug” that does not sacrifice on quality. The therapy is well tailored to heal mice with damaged and scarred hearts, and widens the possibilities to treat other non-cancerous human ailments. If translated to clinical settings, transient CAR T therapy may be less expensive and more readily available than its traditional counterpart

The post CAR T-mRNA Therapy For Cardiac Fibrosis: A New Way Forward appeared first on Medika Life.

What is Lupus?

Lupus (systemic lupus erythematosus) is an autoimmune disease that affects women approximately ten more than men, and is characterized by the overproduction of antibodies that attack the body’s own tissues. Lupus symptoms—ranging from mild to life-threatening—often come and go, making the condition hard to diagnose. Characteristic signs such as fatigue, muscle pains, joint pains and fever also coincide with symptoms of other diseases.

Current Lupus Treatments  

Although lupus has no cure, modern day symptomatic treatments ensure a normal life expectancy for 80-90% of people with lupus. One of our successes at Human Genome Sciences, a company I founded and served as Chair and CEO, was the use of genomics to discover and bring to market the first drug to treat lupus: Benlysta. Although the medicine proved to be effective, for some with lupus even the strongest drugs offer no relief.

CAR T Therapy for Lupus 

In their study, Mackensen et al. test the effectiveness of CAR T therapy for treatment-resistant forms of lupus. The theory derives itself from CAR T cells’ ability to kill cells. In lupus, B cells produce antibodies that attack the body and trigger inflammation (Figure 2). Using CAR T therapy, the researchers aimed to purge the B cell lineage, allowing the body to restore B cells de novo.

To do this, the researchers first collected patients’ white blood cells. The patients then underwent lymphodepletion, the use of chemotherapy drugs (i.e. fludarabine and cyclophosphamide) to preferentially kill B cells. As seen in Figure 3, this drug regimen leaves room for the later infusion of engineered T cells, but can be very dangerous if the immune system is too thoroughly depleted.

The team altered the patient T cells with new genetic information. The new, chimeric T cell products contained a new receptor—a single-chain variable (scFv) fragment poised to detect CD19-expressing cells—a 4-1BB costimulatory domain and a CD3 intracellular domain. Figure 4 illustrates these cellular components. The antibody-derived receptor and additional costimulatory structure do not naturally occur on T cells, lending the chimeric nature the therapy is coined after (Chimeric Antigen Receptor T cells).

Results 

Five patients with severe, treatment-resistant lupus (four women and one man) participated in the study. Lupus impacted several of their organs, including the kidney, heart, lungs, and joints. In addition, these patients did not respond to steroids, antimalarial drugs and other immunosuppressive medicines.

Each of the patients received a transfusion of modified T cells after chemoablation treatment. The chemoablation successfully depleted patient B cells while T cell numbers remained within normal range. Moreover, the team could no longer detect malignant autoantibodies (ie. anti-double stranded DNA antibodies). The participants’ responses to vaccines also remained largely unchanged, suggesting that the CAR T therapy correctly targeted detreminal B cells without damaging the entirety of the immune system.

Three months later, prior symptoms including kidney inflammation, arthritis, fatigue, and heart fibrosis disappeared, and all other immunosuppressive drugs could be discontinued. The symptoms did not return even when B cells began to reconstitute months later. Remission was defined by DORIS, a standardized criteria used to measure lupus symptom severity.

Future Possibilities for CAR T 

This study demonstrates how CAR T can send treatment-refractory lupus to remission. This is a first hopeful step. The search is now on for ways to improve CAR T induced remission for prior B cell ablation using a cocktail of cytotoxic drugs. The study also opens the door to the possibility of applying CAR T to other difficult to treat autoimmune diseases.

The post CAR T Therapy: From Cancer To Autoimmune Disease, The Lupus Example appeared first on Medika Life.

This third installment highlights recent advances in treating multiple myeloma. The first in the series lays the foundation for understanding how CAR T works, while the second outlines its uses for B cell cancers.

Multiple myeloma is a relatively uncommon yet serious disease estimated to impact more than 30,000 US citizens this year. Although several treatment options exist, the illness is considered incurable as most treatments do not resolve the condition permanently—including the most recent advancements with CAR T cells. Here, we describe an approach using a different variant of CAR T cells for multiple myeloma that holds promise for those with treatment-resistant forms of the disease.

What is Multiple Myeloma?

Multiple myeloma (MM) or myeloma is a cancer of the plasma B cells found in the bone marrow. Although these white blood cells typically produce antibodies, for people with multiple myeloma, the plasma cells multiply faster than the body can handle, produce abnormal antibodies, and set the body out of balance. The illness can spread to other organs through the bloodstream, and masses of plasma cells may form in the bone marrow or soft tissues, as well.

The illness usually occurs to people 60 years and older, and is unlikely to develop in individuals under 40 years of age. The symptoms can be widely varying—some even report having no symptoms at all—but most with this disease experience bone pain and fatigue. Other common complications include anemia, kidney problems, or thickened blood.

Without treatment, the prognosis is poor. However, with the advent of chemotherapy and more advanced medicines, survival is usually four to five years. If diagnosed early, the five-year survival rate exceeds 77%.

Patients with active myeloma first receive a combination of drugs to target the abnormal cells. Another alternative is chemotherapy. For example, I contributed to the creation of Velcade, a chemotherapy medicine which slows or stops the growth of myeloma cells. Stem cell transplants, steroids and even CAR T therapy—a newer medical technology which alters patient cells in the lab and infuses them back into the body to fight the cancer—may be tried as other potential options. Unfortunately, once a therapy fails, the body typically becomes resistant to its reintroduction and thus loses efficacy.

The Current Reality of CAR T Therapy 

CAR T therapy has recently been approved to treat multiple myeloma, but it is only considered after four or more refractory lines of treatment—in other words, when other four or more options fail to achieve lasting remission. The two existing CAR T therapies on the market target B cell maturation antigen (BCMA), an antigen expressed on the surface of malignant plasma cells; in this piece, the antigen will be referred to as Target 1.

A Chimeric Antigen Receptor T cell derives its name from the synthetic combination of T cell and antibody properties. Patient T cells are taken from the body and modified to detect Target 1 through an antibody-based fusion receptor (scFv). The lysing process relies on signaling from the T cell. As seen in Figure 1, when the CAR T antigen receptor binds with Target 1 on the cancer cell, the CAR T cell releases chemicals to trigger the cancer cell’s death.

Clinical trials have confirmed these CAR T therapies as safe to use and capable of producing results. A study of Ide-cel found 73% of participants had a decrease in their cancer. Even more successfully, a study of Cilta-cel saw a 98% response rate, with 78% of patients showing no signs of cancer in their bone marrow. The outstanding issue with both treatments, however, is that relapse does eventually occur—around 8.8 months later for Ide-cel, and 22 months later with Cilta-cel.

With relapse and treatment resistance a prevailing concern for multiple myeloma treatments—not just CAR T—researchers are seeking new ways to sustain longer remission and increase survivability when other alternatives are exhausted.  One possible method is to enhance current CAR T protocols with a new therapeutic target.

Methods 

In their study, Mailankody et al. consider the safety of an alternative antigen target. The target is known as G protein-coupled receptor, class C, group 5, member D (GPRC5D), but shall be referred to as Target 2 for simplicity. Despite its unknown function in tissues, it poses as a promising CAR T antigen target due to its presence in several myeloma cell lines and in bone marrow plasma cells.

The team chose a second generation CAR T design for their product. Second generation CAR T cells contain a single costimulatory domain (shown in blue in Figure 2) inside the T cell to extend the life of the cell once in the body. The chimeric antigen receptor in this study is tailored to find cancer cells that express Target 2 (denoted in green in Figure 2).

As depicted in Figure 3, the researchers first collected patient T cells through leukapheresis. They modified the T cells, expanded them to large numbers, and then infused the CAR T cells back into the body after completing preparatory chemotherapy. The patients received an escalating dose of the trial CAR T infusion, totalling to four doses.

Results 

A total of 17 participants received CAR T therapy, all who have previously tried five different kinds of multiple myeloma treatment. The majority of participants developed cancer resistance to their last line of treatment; this includes a group of individuals who previously received Target 1 CAR T therapy.

On the whole, this study successfully confirms Target 2 CAR T therapy as safe and effective, particularly for individuals who have already received Target 1 CAR T cell therapy or have run through several other therapeutic options. Around 78% of patients had a partial response or better, and 59% had a very good partial response or better. The therapy was effective even ten months after infusion for some individuals.

Common CAR T therapy side effects include cytokine release syndrome and immune effector cell-associated neurotoxicity (ICANS). While both conditions can be reversed with prompt treatment, the severity of both side effects can range from mild to life-threatening. Most participants experienced milder cytokine release, with the exception of one patient who experienced life-threatening side effects. All with side effects were treated.

Future Directions

Mailankody et al. demonstrate that Target 2 CAR T therapy can effectively treat multiple myeloma. If Target 1 CAR T therapy fails, Target 2 appears to be a viable alternative. The results also suggest that using Target 1 and Target 2 CAR T therapies in succession could lead to positive outcomes. A third alternative is to enhance the T cell design further to allow for tandem targeting; an ideal synergy could be attained if T cells were fitted with both Target 1 and Target 2 receptors, hopefully resulting in longer remission periods and increased survival.

The post CAR T Therapy For Drug Resistant Multiple Myeloma appeared first on Medika Life.

CAR T is an effective treatment for some hard to treat cancers. This “living drug” is made by extracting killer T cells from the body, manipulating them to target cancer cells, multiplying the newly engineered cells and infusing them back into the body. Development over the last forty years has evolved the precision, efficiency and safety of this technology. Arguably the best example is the treatment of  B cell cancers.

B cells to B cell cancers

CUSABIO Link Added

Figure 1 illustrates the development of antibody cells. B cell maturation begins with stem cells in the bone marrow and is completed with the antibody producing plasma B cells.

Typically, threats to the body leave trails of foreign antigen which can be followed. B cells detect these antigens and proliferate to eliminate pathogens, but these numbers quickly subside. This is done by design. The body regulates this process to ensure the bloodstream is not flooded with too many antibodies to prevent normal function. However, this system can go awry at any point. B cell precursors, intermediate cells or plasma cells can mutate and grow uncontrollably, causing damage to the body rather than shielding from it. When this happens, the immune system weakens and B cell cancers result.

LYMPHOMA CANADA

B cell lymphomas originate from the lymphatic system organs, vessels and tissues, such as the lymph nodes or the spleen. In contrast, leukemias circulate in the bone marrow and blood instead of the lymph organs. Although multiple myeloma is also a cancer of the bone marrow, it entails the abnormal growth of plasma B cells in particular.

Treating B cell cancers

Chemotherapy and radiation most successfully reduce the size and quantity of B cell tumors. Partial remission is very achievable, but complete remission—the total absence of cancer— is much more difficult to attain. For many, the cancer may temporarily recede for months or years after treatment before recurring. And when the cancer recurs, it can be resistant to treatment.

CAR T cell therapy addresses this problem by transforming patient immune cells into an anti-cancer drug. Cells are taken from the body and modified to detect the tumor cells. CAR T cells are fitted with a fusion protein (scFV, Figure 3) made from antigen-recognizing regions of antibodies. This component is typically engineered to target CD19, a B cell antigen known for its role in B cell signaling. This protein is found in B cells of all stages and is present on the surface of many B cell cancers. CD19 is not found on hematopoietic stem cells—those which have yet to mature and gain purpose; as a result, the therapy is less likely to target non-cancerous immune cells, an ideal quality in a therapeutic target.

FIGURE 3: CD19 is an antigen expressed on cancer cells. CAR T cells are fitted with an antigen recognition domain, a single chain variable fragment (scFV), to target the CD19 on the surface of these cancer cells. Once the antigen domain binds to the cancer cell, the CAR T cell can induce apoptosis to eliminate the tumor cell.

BRITTEN, OLIVER, ET AL. 2019 Link Added

Once the CAR T cell binds to CD19 on the tumor cell, several signals are released from the endodomain that trigger cell death of the tumor cell through apoptosis. The co-stimulatory molecules found in the interior of the CAR T cell allow it to multiply and persist in the body.

Normal T cells from the body lack the precision of this antigen recognizing protein and usually require specific proteins—major histocompatibility complexes—to present the antigen and facilitate similar binding. CAR T cells forgo these steps, producing superior hybrid molecules which combine antibody detection with T cell signal transduction. This synthetic engineering defines the chimeric nature of Chimeric Antigen Receptor T cells.

Why CAR T therapy?

As of publication, CAR T is only considered after standard cancer treatments have run their course. Why, then, do people turn to CAR T therapy if it is only considered after several other lines of treatment?

For those who have B cancers which are unresponsive to alternative anti-cancer treatments, CAR T can deliver lasting remission and extend life expectancy by several years—sometimes without additional treatment.

NOVARTIS

For example, one study revealed that 44% of young patients with acute lymphoblastic leukemia (ALL) live at least five years without relapse after CAR T therapy. This is especially remarkable given how difficult it can be to treat the condition and the less than 10% five-year survival rate. Approved CAR T therapies also exist for patients with diffuse large B cell lymphoma (DLCL), follicular lymphoma, mantle cell lymphoma and multiple myeloma.

ACCELERATING CANCER IMMUNOTHERAPY RESEARCH

There is a caveat—it is possible to experience relapse after CAR T therapy. One contributing factor is CD19 antigen escape, a type of CAR T resistance. As illustrated in Figure 5, patients with antigen escape develop cancer cells which no longer express CD19 and thus escape recognition by CAR T cells. So while CD19 targeting has proven effective, this phenomena highlights the need to find alternative antigen targets to improve the drug’s efficiency.

One possible solution is dual targeting CAR T cells. By engineering T cells which detect more than one antigen on cancer cells, the therapy has a greater chance of attacking tumor-only cells and overcoming antigen escape. Current contenders include dual targeting of antigens CD19 and CD22, as well as CD19 and CD20.

Summary 

CAR T shines best in solving what other therapies cannot. When other lines of cancer treatments such as chemotherapy or radiation cause relapse, CAR T therapy often provides a more lasting remission. There’s promise for these engineered T cells to become even more effective in the future with the advent of dual-targeting CAR T cells. And while none of the six FDA approved CAR T therapies are currently used as first-line treatment, developments are underway to establish this innovative technology as a primary line of defense. This is a major step forward for treating B cell cancers, and we can anticipate more to come.

The post The Remarkable Research Of CAR T Therapy: B Cell Cancers appeared first on Medika Life.

Using the body’s own immune cells as anticancer agents has long been part of this dream. I was an early pioneer in creating one of the first proven cell therapies using dendritic macrophages to treat prostate cancer. Today, immune cell therapy offers hope to people with cancer and other previously untreatable diseases.

This series will explain a recent and revolutionary cell therapy called CAR T, delving into current successes and future opportunities.

The “T’ of CAR “T” 

CAR T is short for Chimeric Antigen Receptor T cells. Essential to understanding this therapy is an understanding of T cells and cell-mediated immunity.

Adaptive Immunity 

Adaptive immunity allows humans to form a tailored defense to foreign invaders. Adaptive immune cells memorize the telltale signs of enemies and trigger defensive mechanisms if the signs are detected in the future. This branch of immunity concerts two separate arms—humoral immunity driven by antibody-producing B cells, and cell-mediated immunity driven by “helper” T cells and “killer” T cells.

CAR T technology alters the typical functioning of cytotoxic cells. Instead of indirectly aiding antiviral processes as CD4+ helper T cells do, CAR T borrows the cytotoxic power of CD8+ killer T cells to destroy infected or abnormal host cells, thus transforming into a “living drug.” A typical cytotoxic T cell eliminates threats using the following process:

WIKIPEDIA Link Added

The process (as illustrated in Figure 1) begins with the differentiation of an inactive T cell—in essence, any T cell without a specified purpose. As if waiting for the right key, a T cell does not activate unless it encounters an antigen presenting cell (APC) with its corresponding antigen. In order for an interaction between the two cells to occur, several steps must occur.

Firstly, the antigen presenting cell must process the antigen, the enemy components, into smaller peptides. Then, these peptides must be carried to the antigen presenting cell’s surface by major histocompatibility complexes (MHC). Immature CD8+ T cells require MHC Class I molecules to facilitate this translocation. Around this time, a secondary signal such as CD80 or CD86 must also be received by the T cell. In the final step, the antigen presenting cell releases a protein signal called CD40 and cooperates with helper T cells to finalize the differentiation process.

How Killer T Cells Kill 

DANANGUYEN DERIVATIVE: NAGUALDESIGN

Killer T cells destroy infected and abnormal cells by inducing apoptosis, a form of controlled cell death which does not spark inflammation. Pockets of enzyme within the T cell must make contact with the target cell to trigger its death.

When a cytotoxic T cell recognizes its target, it binds to the class I MHC molecule on the surface of the target cell (see Figure 3) to create a bridge. With the bridge completed, the T cell can then release the enzymes. One enzyme drills pores in the target cell’s membrane, thus ruining its integrity. The other travels through these newly made tunnels, tipping an enzyme cascade inside the target cell which accelerates its degradation.

The crumbling target cell mimics the imagery of bricks falling from castle walls. Nearby phagocytes recognize the “crash of bricks”—more accurately, sense a change in membrane—and begin ingesting the target cell. The target cell breaks down to nothing inside the phagocyte without stimulating inflammation or other side effects.

Construction of a Chimeric Antigen Receptor 

Killer T cells are clearly useful in clearing irregular host cells. Researchers recognized this and sought to harness this natural design to eliminate cancer cells through CAR T. Chimeric antigen receptors are engineered to detect a specific antigen and trigger the destruction of a target cell. The most basic CAR T design accomplishes this by manipulating antigen binding sites normally intrinsic to antibodies—single chain variable fragments (scFV)—to lend cytotoxic T cells higher antigen specificity. The CAR T cell recognizes specific antigens thanks to this domain.

Next comes the flexible hinge region. This region simultaneously stabilizes the CAR while its length provides grants easier access to specific antigens. The transmembrane domain anchors the antibody and hinge structure.

The intracellular domain describes receptors lying within the T cell. Basic CAR T design employs CD3 here, a T cell receptor needed for T cell differentiation (see Figure 4). Second and third generation CAR models included secondary signal receptors such as CD28 to improve target cell elimination and cell signaling (Figure 5).

More recent research developments in CAR design deviate from this foundational model to finetune precision and function. For example, T cell receptor fusion construct (TRuC) CAR tethers the scFV region to the several intracellular CD3 subunits, thereby reducing secondary signaling hypothesized to be unnecessary.

Universal CAR (uCAR), on the other hand, augments antibody specification by fusing biotin to the transmembrane domain and the endodomain. Other research efforts incorporate cytokines (signaling molecules) and other molecules to improve T cell expansion and persistence, as well as synthetic control switches to minimize the therapy’s toxic side effects. The groundwork model inspires many alternative CAR designs beyond those demonstrated here.

The beauty of this science lies in the melding of two previously separate abilities. CAR T therapy replaces the T cell receptor with an antibody-like structure, all while maintaining the transduction machinery of a T cell. Like this, MHC class I binding becomes irrelevant and a response can be immediately triggered.

The CAR T Therapy Process 

What does the CAR T therapy process look like?

Figure 2 illustrates the progression clearly. For a patient receiving CAR T therapy, the process may begin with a medical professional drawing their blood and separating T cells from that sample using apheresis; this would be an autologous treatment, as the cells used originate from the same patient. T cells can also be isolated from a healthy donor’s blood sample, otherwise known as allogeneic transplantation.

The cells must then be genetically altered to recognize a particular target in a cell processing center. To do this, the cells are “expanded”—a process which stimulates T cell proliferation. The new plethora of T cells must be purified and then genetically modified with a gene that encodes the desired chimeric antigen receptor. CRISPR technology can be used here to accomplish the task.

The cells are now ready for infusion. The cells are frozen and sent back to the treatment center. The patient preps for infusion with a lymphocyte-depleting chemotherapy; the chemotherapy reduces the number of white blood cells in the blood to reduce competition for the CAR T cells, thus helping them multiply. With success, the engineered T cells will recognize the antigen on cancerous cells, bind to it, and mark it for destruction via apoptosis. The infusion takes between 30 to 90 minutes to complete, but the patient will be closely monitored for days, weeks or months to watch for any adverse side effects and to receive additional treatments.

Side effects can occur if the “living drug” multiplies too actively, the most common being cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Also commonly known as “cytokine storm,” CRS occurs when proteins called cytokines flood the immune system and send it into overdrive. Symptoms tend to be mild—fever, nausea, headache, rash, and more—and resolve within a couple of days, but they can also be severe or life threatening. ICANS refers to a neurotoxic condition that appears within one to three weeks after T cell infusion. Early signs, such as tremor and lethargy, can lapse into stupor, seizures or coma if untreated. More on managing side effects to come in later installments in this series.

The long term side effects of CAR T are unknown. As a result, the FDA stipulates that gene editing treatments such as CAR T therapy should be monitored for up to 15 years—five years of annual follow ups, followed by ten years of questionnaires and/or other queries.

What Illnesses Can CAR T Treat?

CAR T therapy is FDA approved to treat B cell-derived lymphomas—cancers caused when B cells (not T cells) grow too rapidly—as well as multiple myeloma, cancer of plasma cells found in the bone marrow. These treatments tailor chimeric antigen receptors to target an antigen called CD19 found only on the tumor cells of lymphoma patients. Another target is BCMA, a B cell maturation antigen specific to multiple myeloma.

CAR T therapies may be federally approved, but they are not used as first or second line cancer treatments; usually CAR T therapy is considered after receiving standard chemotherapy treatment and other alternatives. And as a newer treatment, it may be more expensive than other therapies or may not be fully covered by health insurance.

But this field is ever growing. Several hundred clinical trials are in progress to test the boundaries of this mechanism and enhance its design. The next installations in this series will cover some of the most recent discoveries in the CAR T circuit, such as treatment advances in B cell lymphomas, lupus and heart disease, as well as innovations in CAR T precision.

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