Risks of intensive therapy
But while these therapies show promise, the process is very intensive. The lymphodepleting regimen increases the risk for infection and patients are commonly hospitalized for a week or more following infusion for toxicity monitoring. Serious adverse events such as cytokine release syndrome (CRS) can occur days to weeks after CAR T-cell infusion. In the five-patient case series reported in 2022, patients were hospitalized for 10 days following treatment.
The patient with antisynthetase syndrome, as well as three of five patients in the SLE case series study experienced mild CRS following infusion. Patients are also at a high risk for infection, as the engineered T cells target all B cells, not just the autoreactive immune cells.
The inability to differentiate between disease-causing and protective immune cells is an issue for all currently available drugs treating autoimmune disease, Dr. Konig said. But scientists are already working on how to make these potent cellular therapies safer and more precise.
Alternatives to standard CAR T-cell therapies
Engineering T cells with RNA is a new approach to limit the side effects and toxicity of CAR T-cell therapy, said Chris Jewell, PhD, the chief scientific officer at Cartesian Therapeutics, a biotechnology company based in Gaithersburg, Md. The company’s RNA CAR T-cell (rCAR-T) therapy – called DESCARTES-08 – is in phase 2 clinical trials for treatment of myasthenia gravis. Once these rCAR-T cells are infused in patients, as they divide, the RNAnaturally decays, he explained, meaning that after a certain point, the CAR is no longer expressed.
Cartesian Therapeutics
Dr. Chris Jewell
DESCARTES-08 targets B-cell maturation antigen (BCMA), which is primarily expressed on plasma cells, rather than all B cells, Dr. Jewell said.
“Targeting BCMA, we actually have a more selective profile,” he explained. “We are targeting the cells primarily responsible for the pathogenicity; many plasma cells – such as long-lived plasma cells – also take a long time to repopulate.”
This therapy also does not require lymphodepletion prior to infusion and can be done in an outpatient setting. The therapy is given in multiple infusions, once per week.
In the most recent clinical trial, patients with myasthenia gravis received six infusions over 6 weeks and experienced notable decreases in myasthenia gravis severity scale at up to 9 months of follow-up.
Abata Therapeutics
Dr. Leonard Dragone
While standard CAR T-cell therapies under clinical investigational up to now all use effector T cells, regulatory T cells (Tregs) can also be engineered to target autoimmune disease. Abata Therapeutics, based in Boston, is using this approach for therapies for progressive multiple sclerosis and type 1 diabetes. These engineered Tregs express a T-cell receptor (TCR) that recognizes tissue-specific antigens and suppress inflammation at the site of the disease. “Treg-based cell therapies are really harnessing the natural power of regulatory cells to reset immune tolerance and recalibrate the immune system,” said their chief medical officer, Leonard Dragone, MD, PhD.
These therapies are derived from terminally differentiated cells that have limited capacity to produce pro-inflammatory cytokines including interleukin-2 or interferon gamma, Dr. Dragone explained. “CRS is difficult to envision from engineered Treg products and hasn’t been observed in any clinical experience with polyclonal Tregs,” he said.
This approach also does not require lymphodepletion prior to treatment. The company’s Treg cellular therapy for progressive MS is currently in investigational new drug-enabling studies, and they aim to dose their first patients in 2024.