mRNA CAR T Cell Therapy Receives FDA’s Rare Pediatric Designation to Treat Juvenile Dermatomyositis

In September 2024, the U.S. Food & Drug Administration (FDA) granted its rare pediatric disease designation to Descartes-08 for the treatment of juvenile dermatomyositis. At the time this information became available, the investigational new drug filing for phase 2 was on track for the end of 2024.¹

The FDA grants the rare pediatric disease designation for serious and life-threatening diseases that principally affect children aged 18 years or younger and fewer than 200,000 people in the U.S. Juvenile dermatomyositis is a rare pediatric autoimmune disorder marked by skin rash and severe muscle inflammation affecting multiple organ systems, including the joints, heart, lungs, kidneys, eyes and gastrointestinal systems. The symptoms can range from mild to life-threatening and include fatigue, joint pain, muscle weakness and fever. The condition affects approximately two to four children per million, or about 4,000 children in the U.S.^1,2

Treatment

The drugs used to manage myositis are not FDA approved for the treatment of myositis and are being used off label. However, they are all approved for conditions similar to myositis. The use of these drugs for myositis is based on small clinical trials, expert experience and individual reports in the literature of effectiveness for myositis.2 These treatments include systemic glucocorticoids, methotrexate and other immunosuppressive agents, and intravenous immunoglobulin (IVIG).

Descartes-08, an mRNA cell therapy, is an autologous mRNA-engineered chimeric antigen receptor T cell therapy (mRNA CAR T cell) targeting B cell maturation antigen (BCMA). The agent is designed to be administered without preconditioning chemotherapy and does not use integrating vectors, unlike other FDA approved CAR T cell therapies.³

CAR T-Cell Therapies

Current FDA-approved CAR T cell therapies are individually customized for each patient, with a treatment cost of more than $450,000 per dose. Not including juvenile dermatomyositis, seven CAR T cell therapies are FDA approved for lymphoma, some leukemias and multiple myeloma in both adults and children.

The therapy is made by collecting the patient’s own T cells, which are then engineered in a lab by adding a gene for a chimeric antigen receptor that helps the T cell attach to a specific cancer cell antigen. Millions of these revamped T cells are then manufactured and infused back into the patient.

There are many side effects from this treatment, including cytokine release syndrome, which can lead to very high fever, severe hypotension and sometimes fatalities. The benefits of these therapies need to be carefully weighed along with the risks.

Descartes-08 is also in phase 2 clinical development for the treatment of adults with generalized myasthenia gravis and adults with systematic lupus erythematosus. A clinical trial is planned for additional autoimmune diseases.

Michele B. Kaufman, PharmD, BCGP, is a freelance medical writer based in New York City and a pharmacist at New York Presbyterian Lower Manhattan Hospital.

References

1. Cartesian Therapeutics receives FDA rare pediatric disease designation for descartes-08 for the treatment of juvenile dermatomyositis [news release]. Cartesian Therapeutics Inc. 2024 Sep 9.
2. Types of myositis: Juvenile myositis. The Myositis Association. 2024.
3. CAR-T cells: Engineering patients’ immune cells to treat their cancers. National Cancer Institute. 2022 Mar 10.