An approved cancer medication called teclistamab is showing unexpected promise for patients with severe autoimmune diseases that have resisted all standard treatments. In a new analysis of 18 patients with various autoimmune conditions, 11 achieved major clinical responses and four saw at least some improvement, even after stopping all their previous medications.

What Makes This Drug Different From Current Autoimmune Treatments?

Teclistamab works in a fundamentally different way than the medications doctors typically prescribe for autoimmune diseases. Instead of simply suppressing the immune system broadly, it targets a specific culprit: B cells, which are white blood cells that go haywire in autoimmune conditions. These cells produce antibodies that attack the body's own tissues, and they also interact with other immune components to drive organ damage.

The drug uses a bispecific antibody mechanism, meaning it has two targets at once. It locks onto B-cell maturation antigen (BCMA) and a protein called CD3, delivering what researchers describe as a "double-whammy" to B cells. Importantly, this approach doesn't require the harsh conditioning regimen that other advanced therapies, like CAR T-cell therapy, demand.

"Our findings support further evaluation of teclistamab as a potential treatment for highly selected patients with severe, treatment-refractory connective tissue diseases," stated Dr. Tobias Alexander of Charité, Universitätsmedizin Berlin in Germany.

Dr. Tobias Alexander, Charité, Universitätsmedizin Berlin

Which Autoimmune Diseases Showed the Most Benefit?

The 18 patients in the study had diverse autoimmune conditions. The breakdown included 10 patients with systemic sclerosis (a disease that hardens connective tissue), four with idiopathic inflammatory myositis (muscle inflammation), two with systemic lupus erythematosus (SLE), one with undifferentiated connective tissue disease, and one with immunoglobulin G4-related disease. The median patient age was 49 years, and most had already tried a median of five prior therapies before starting teclistamab.

For the systemic sclerosis patients, three of seven who could be evaluated for overall response saw at least a 50% improvement in symptoms. Among those with heart involvement from their disease, biomarkers of damage declined and heart function indicators improved in the survivors. One patient with SLE maintained a major clinical response for 16 weeks in an earlier trial, and some patients in the current study kept their improvements for 18 months or longer.

What Are the Serious Risks Doctors Need to Monitor?

While the results are encouraging, teclistamab carries significant safety concerns that researchers emphasize cannot be overlooked. All 18 patients experienced severe hypogammaglobulinemia, a condition where the body loses the ability to produce antibodies, leaving patients vulnerable to infections. Five of the 18 patients suffered severe infections as a result.

Two deaths occurred in the systemic sclerosis group within weeks of starting the drug. One patient died from multiorgan complications including heart failure and lung hemorrhage, and another had a presumed cardiac arrest. While researchers could not establish a definite causal link to teclistamab, the deaths underscore the need for extreme caution. Two additional patients developed new-onset colitis, and cytokine release syndrome (an inflammatory reaction) was nearly universal, though episodes remained mild.

How Should Doctors Approach This Treatment?

• Patient Selection: Teclistamab should only be used in highly selected patients with severe, treatment-refractory autoimmune diseases who have exhausted other options, not as a first-line therapy.
• Specialized Centers: Treatment must occur only in experienced centers with established multidisciplinary teams that integrate expertise in autoimmune inflammatory diseases with hematology-driven management of immune complications.
• Close Monitoring: Patients require intensive monitoring for infections related to antibody loss, cardiac complications, and other severe adverse events, with ongoing follow-up extending well beyond the initial treatment period.
• Careful Dosing: The standard step-up protocol for teclistamab may need adjustment based on individual patient factors, as the current study used varying dose numbers and intervals between doses.

Researchers emphasized that "clinically significant adverse events, including infections related to hypogammaglobulinemia and fatal events in patients with advanced cardiac involvement, underscore the need for careful patient selection and close monitoring".

What Comes Next for This Treatment Approach?

The findings represent a significant step forward, but researchers stress that much work remains. They called for prospective controlled trials with standardized assessments, predefined safety boundaries, and systematic long-term follow-up. Key questions still need answers, including defining the ideal patient population, determining optimal dosing regimens, understanding how long responses last after B cells recover, and comparing teclistamab's effectiveness to other advanced therapies like CAR T-cell therapy or hematopoietic stem cell transplantation.

The convergence of two recent trends in immunology has made this moment possible. First, basic science has revealed that B cells do far more damage in autoimmune diseases than simply producing rogue antibodies; they also dysregulate other immune system components. Second, researchers discovered that CAR T-cell therapy, long used successfully in blood cancers, could be adapted for autoimmune diseases. Teclistamab offers a potentially less invasive path to similar B-cell depletion.

For patients with severe autoimmune diseases that have resisted conventional treatment, teclistamab represents a glimmer of hope. However, the balance between benefit and risk remains delicate, and this approach is decidedly not for everyone. As research continues, the medical community will work to identify which patients are most likely to benefit and how to minimize the serious complications that can arise.