VIENNA — From a dozen or so studies and sessions devoted to the role of chimeric antigen receptor (CAR) T cells in rheumatic diseases at the annual European Congress of Rheumatology, the message was uniformly positive, supporting growing evidence that drugs in this class are heading toward a paradigm shift in refractory rheumatic diseases.
Of the reports, an update from a 15-patient case series with at least 1 year of follow-up provides “the first long-term evidence of safety and efficacy in multiple rheumatic diseases,” according to Georg Schett, MD, PhD, director of rheumatology and immunology, University of Erlangen-Nürnberg, Erlangen, Germany.
Ted Bosworth/Medscape Medical News
Dr. Georg Schett
The report of high rates of activity and low relative risk of serious adverse events from the same series was published earlier this year in The New England Journal of Medicine when the median follow-up was 15 months. Almost all of the patients have now completed at least 1 year of follow-up and about a third have completed more than 2 years.
SLE Is Frequently Targeted in CAR T-Cell Studies
The three rheumatic diseases represented in this series of patients, all of whom had failed multiple previous immune suppressive treatments, were systemic lupus erythematosus (SLE), idiopathic inflammatory myositis (IIM), and systemic sclerosis (SSc). After the autologous T cells were harvested, they were expanded and transfected with the CD19 CAR. The proprietary investigational product, called MB-CART19.1 (Miltenyi Biotec), was administered in a single dose of one million cells per kg bodyweight.
The response rates have been, and continue to be, impressive. For the eight patients with SLE, all achieved the definition of remission in SLE criteria after one dose of treatment. Complete resolution of all major symptom types was achieved after 6 months of follow-up. So far, no patient has relapsed.
For the three patients with IIM, all reached the American College of Rheumatology–EULAR criteria for a major response. All creatine kinase levels had normalized by 3 months. In this group, there was one relapse, which occurred after 18 months of follow-up.
All four patients with SSc achieved a major response on the European Scleroderma Trials and Research (EUSTAR) group activity index. The median reduction from baseline in the EUSTAR score was 4.2 points, and this has been maintained in follow-up to date.
Remissions Have Persisted Off All Therapies
These remissions were achieved and maintained after a single dose of CAR T-cell therapy despite discontinuation of all immunosuppressive therapies. With the exception of the single relapse, all remissions have persisted through follow-up to date.
These responses were achieved with manageable side effects, according to Dr. Schett. The most serious adverse event was a grade 4 neutropenia that developed 4 months after receiving CAR T cells. It resolved with granulocyte colony-stimulating factor treatment. Cytokine release syndrome (CRS) has occurred in 10 patients, but it was grade 1 in eight patients and grade 2 in the others. There has been no neurotoxicity.
Almost all patients have experienced an infection during follow-up, but there has been no discernible pattern in relationship to the timing or types of infections. The most common have involved the upper respiratory tract and have been of mild severity, with cases disseminated similarly over early vs late follow-up. There was one case of pneumonia involving antibiotic treatment and a hospital stay, but it resolved.
Dr. Schett acknowledged that safety is a bigger concern in autoimmune diseases, which are often serious but rarely fatal, than in the hematologic malignancies for which CAR T cells were initially tested, but the low rates of serious adverse events in his and other early studies have supported the premise that the risks are not the same.
Asked specifically if CAR T cells can be considered a game changer in autoimmune rheumatic diseases, Dr. Schett was cautious. One reason is the CAR T cells are a complex therapy relative to biologic disease-modifying antirheumatic drugs. He thinks, therefore, that much more data are needed to confirm safety and efficacy. In addition, they are expensive, so it is not yet clear how they will be integrated with other options.
Yet, he thinks the evidence so far suggests a profound effect on the fundamental drivers of autoimmune disease. Their specific mechanism of benefit is still being evaluated, but he considers the clinical responses consistent with a “reset” hypothesis.
After a response, “we are seeing drug-free remissions in some patients as long as they have been followed,” Dr. Schett said. Based on the fact that disease control is being observed off all other therapies, “this only makes sense to me if there is some sort of immunologic reset.”