JAK Inhibitors Could Increase Cancer Risks by as Much as 40%: Study

Older patients and those with high disease activity may face greater risks than others taking the common arthritis and autoimmune disease treatments.

New research suggests that side effects of rheumatoid arthritis drugs like Xeljanz and Rinvoq may increase cancer risk by up to 40%.

The findings were published by a team of German researchers in the Annals of Rheumatic Diseases on June 25, reporting that they have found additional evidence that the drugs carry a higher risk of cancer when compared to other biologic treatments.

The drugs in question belong to a class of medications known as Janus Kinase (JAK) inhibitors, which include blockbuster treatments like Xeljanz, Rinvoq and others. JAK inhibitors block the JAK enzymes in the body and are used to treat a wide variety of conditions ranging from autoimmune diseases like Crohn’s disease, rheumatoid arthritis and alopecia, as well as COVID-19 and other inflammatory ailments. They are also commonly used to treat dermatological conditions, such as eczema and atopic dermatitis.

However, evidence has emerged over the last several years, linking the class of medications to concerns about potential cancer, beginning with preliminary data in early 2021 from a Xeljanz post-marketing study.

In the new study, researchers from the German Rheumatology Research Center looked at data on antirheumatic drug use from January 2017 to June 2024.

The team, led by Dr. Martin Shaefer, examined what type of treatment patients used and incidence rates of cancer. According to the findings, JAK inhibitor use was linked with a 40% increased risk of cancer when compared to biologics. 

The researchers noted that the risks appeared higher for certain subgroups of patients, including those who were 60 or older when they started treatment, patients previously treated with biologics who switched to JAK inhibitors, and patients with high disease activity.

“In this German observational cohort study, an overall small increase in malignancy risk for JAKi vs bDMARD treatment was observed, with more pronounced risks in some subgroups of patients. The observed risk should be carefully counterbalanced to the known malignancy risk associated with insufficient disease control.”

-Dr. Martin Shaefer, Comparative risk of incident malignancies in rheumatoid arthritis patients treated with Janus kinase inhibitors or bDMARDs

Similar findings in recent years have resulted in a number of Xeljanz lawsuits being filed by former users diagnosed with cancer, pulmonary embolism and other injuries, alleging that drug makers failed to adequately research the side effects of JAK inhibitors and warn about potential risks compared to older TNF inhibitors.

Although each of the complaints raises similar questions of fact and law, there are not currently any consolidated pretrial proceedings in the federal court system, and each of the lawsuits is moving forward as individual claims.