Decoding CAR Therapies
and Clinical Trials
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Patients and clinicians are suddenly hearing a lot about CAR T and NK cell therapies for autoimmune disease, including myositis. CAR therapies are a type of cell therapy in which a patient’s immune cells are genetically modified and then infused back into the patient to target immune cells involved in disease. These approaches are still experimental, but they are already reshaping how we think about “resetting” the immune system instead of suppressing it with immunosuppressor drugs.
Our goal with this post is to translate what is happening in the clinical trials into language our community can use to make decisions about treatments.
Why Myositis is on the CAR MAP now
Why Myositis is on the CAR MAP now
For decades, treatment for myositis has meant cycles of steroids and immunosuppressants that calm inflammation but often fail to deliver a durable remission. The newer CAR (chimeric antigen receptor)- based approaches focus on a central driver of many autoimmune diseases: B cells, the immune cells that produce autoantibodies and help sustain chronic inflammation.
The basic idea is: if we can safely remove the “bad” B cells and allow the immune system to rebuild, some people may achieve long remissions with little or no ongoing immunosuppression. This is the logic behind the current wave of CAR T and NK trials in myositis and idiopathic inflammatory myopathy.
You’ll see different products and sponsors in the US trials——but the core goal is similar: deep, targeted B‑cell depletion with the hope of a durable reset.
Many of you have heard Rituximab, which also depletes B-cells, CAR therapies are many times more powerful in depleting those all types of B cells with the marker
CAR therapy in a nutshell
Most of these trials use some version of “CAR” cell therapy:
Researchers start with immune cells (usually T cells, sometimes NK cell, other type of immune cell known also as Natural Killer cell ).
They add a new “antenna or GPS” to the surface of those cells, called a chimeric antigen receptor (CAR).
That CAR is designed to recognize a specific target on B cells—most often CD19. Why CD-19? Because it is the most reliable and broadly expressed biomarker for B-cells.
After a short course of chemotherapy to make room in the immune system, the modified cells are infused back (or in the case of donor products, infused for the first time).
Once inside the body, these engineered cells hunt down B cells that carry the target, ideally including the ones that are driving autoimmunity. However at this time , all B cells, not just the autoimmune ones, are targeted with CAR therapy.
In myositis and other autoimmune conditions, almost all the leading CAR therapies are being tested in early phase trials (1&2) focused on safety, dose, and early signals of efficacy.
Table I: Autologous vs. Allogeneic Therapies
Autologous vs allogeneic: “your cells” vs “donor cells”
One of the most important distinctions—and one that directly affects logistics, timelines, and risks—is whether the therapy is autologous (your own cells) or allogeneic (donor cells).
Autologous CAR therapies: built from your own cells
With autologous products, the starting material is your own T cells:
Your T cells are collected via a procedure similar to donating blood.
In a lab, they are engineered to express the CAR, expanded, and then frozen.
After a short course of chemotherapy (typically fludarabine + cyclophosphamide over three days), they are infused back into you as a one‑time treatment.
In the myositis space, the main autologous CAR‑T programs are shown in Table I, separating them in autologous allogenic and CAR T and CAR NK trials. Main companies in this area are Cabaletta and Bristo Myers Squibb (BMS) who started in 2024, and Novartis which is launching a phase 2 trial in myositis.
These trials are often designed around a single infusion and long‑term follow‑up, reflecting the possibility that autologous CAR‑T cells may persist in the body for years.
Allogeneic therapies: off‑the‑shelf donor products
With allogeneic products, the starting cells come from a healthy donor (or cord blood), not the patient, and they are kept ready for usage (off-the-shelf). See the Clinical Trials table for companies in the space, BMS has also an allogeneic CAR T Clinical trial, along with Allogene Therapeutics as well as NKARTA (CAR NK).
These are manufactured in batches and stored frozen, so they can be shipped when a patient is ready. That makes them:
Faster to access – no need to wait weeks for your own cells to be engineered.
Standardized – each dose is more consistent, which can help with trial design and dosing.
The trade‑offs are different:
The patient’s immune system may recognize donor cells as foreign and attack them, which can shorten how long they persist.
For donor Tcell products, the manufacturing has to be carefully engineered to avoid graft- versus-host-like reactions; this is less of a concern for NK cells, which are naturally less prone to causing that problem.‑cell products, the manufacturing has to be carefully engineered to avoid graft‑versus‑host‑like reactions; this is less of a concern for NK cells, which are naturally less prone to causing that problem.
Table II illustrates the different PROS/CONS of using the different types of cell manufacturing for CAR Therapies.
CAR‑T vs CAR‑NK: two different “styles” of immune reset
Even within allogeneic therapies, not everything is CAR‑T. Some programs use NK cells instead, and that matters for safety and how the therapy is delivered.
CAR‑T cells: long‑lived specialists
CAR‑T cells are:
T cells that have been genetically engineered to express a CAR.
Highly capable of expansion: they can multiply quickly in the body after infusion.
Potentially long‑lived, sometimes persisting for years.
For autoimmune disease, the theory is that a single, well‑controlled CAR‑T infusion could:
Deeply deplete B cells.
Allow the immune system to rebuild with less autoimmunity.
Deliver a long remission with little or no ongoing immunosuppression.
The downside is that CAR‑T is associated with:
Cytokine release syndrome (CRS) – a systemic inflammatory reaction that ranges from mild fevers to severe illness.
Neurologic side effects (ICANS) – confusion, tremor, word‑finding problems, rarely more serious symptoms.
Local Immune Effector Cell-Associated Toxicity Syndrome (LICATS): mild inflammation in previously affected areas, usually resolving without long-term effects.
That’s why most CAR‑T trials include several days of inpatient monitoring after infusion and access to drugs like tocilizumab and steroids to control these events.
CAR‑NK and NK‑cell therapies: rapid‑response teams
NK‑cell products, including CAR‑NK and “plain” NK cell infusions, behave somewhat differently:
NK cells are part of the innate immune system—a rapid‑response arm that reacts quickly but typically doesn’t persist as long.
Early data from other diseases suggest lower rates of high‑grade CRS and ICANS, which opens the door to outpatient or shorter hospital stays in some protocols.
Because they may persist for a shorter time, NK products are sometimes given as repeated infusions rather than a one‑and‑done dose.
For patients, the main practical differences you’ll notice are:
Often less intense monitoring (though still careful) and potentially fewer days in the hospital.
Possibility of multiple cycles rather than a single infusion.
The fact that these are allogeneic from the start—nobody is collecting your own cells.
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