Xeljanz Cancer Warnings Leave More Questions Than Answers

Following new information disclosed last month about the potential link between side effects of Xeljanz and cancer, users and the medical community are still awaiting details about the specific types of cancer which may be caused by the widely used rheumatoid arthritis drug, and what signs or symptoms for which they should monitor.

Xeljanz (tofacitinib) is part of a new generation of drugs approved for treatment of rheumatoid arthritis, psoriatic arthritis and ulcerative colitis, known as Janus kinase inhibitor (jakinib). When it was first introduced by Pfizer in 2012, it joined a lucrative market which already included long-standing treatment options like Humira, Enbrel and other similar medications known as tumor necrosis factor (TNF) inhibitors.

Amid aggressive marketing over the past eight years, Pfizer grew Xeljanz into a blockbuster medication, generating annual sales in excess of $2 billion worldwide, with more than 200,000 prescriptions. However, data from a recently completed study has raised serious concerns about health risks that were not previously disclosed on the drug’s warning label or prescribing information.

FDA Xeljanz Warning

In February, the FDA issued safety communication about the potential Xeljanz cancer risks, indicating that data from a recently completed post-marketing study found users may be more likely to be diagnosed with cancer, but the agency did not identify any specific malignancies.

As part of the initial approval provided in 2012, Pfizer was required to complete this new research, which compared the Xeljanz 5mg and 10mg doses among individuals with rheumatoid arthritis, who had at least one cardiovascular risk. Those users were then compared to individuals who received the older TNF inhibitor drugs.

While full results have not yet been made available to researchers or the medical community, the FDA indicates that preliminary results showed an increased risk of cancer among users of Xeljanz and Xeljanz XR, when compared to individuals who used Humira or Enbrel.

Limited additional data has been provided by Pfizer, which indicated that out of 4,362 subjects involved in the study, at least 122 cancers (other than non-melanoma skin cancer) have been reported among users of Xeljanz, compared to 42 with TNF inhibitors.

Although the drug maker disclosed that lung cancer on Xeljanz was the most frequently reported malignancy, no information has been provided about other types of cancer identified, or potential signs and symptoms former users should be monitoring for. In addition, it remains unclear how the Xeljanz cancer cases were distributed in time and across different doses of the medication, as well as how long users were monitored.

The study was launched in January 2012, and given the long latency period for many cancers, many users now face concerns that they require on-going medical monitoring to detect and diagnose cases in the future.

Same Study Shows Cardiac and Blood Clot Risks

Earlier results from this same study were released in 2019, after researchers identified an increased risk of pulmonary embolism with the Xeljanz 10mg twice daily dose. This led the FDA to require Pfizer to add a “black box” warning about the risk of these serious blood clots that may develop in the lungs, which is the strongest label the agency can require a medication to carry.

In the middle of the study, Xeljanz users receiving the 10mg version were switched to the lower 5mg twice daily dose, and doctors were warned to limit the higher dose to the shortest duration possible.

The new findings reported last month also identified potential heart risks with Xeljanz, indicating users were more likely to suffer major adverse cardiovascular events (MACE) compared to users of Humira and Enbrel. Of the study participants, Pfizer indicates there were at least 98 reports of heart attack, stroke or other cardiovascular problems on Xeljanz, compared to 37 among users of the TNF inhibitors.

While awaiting access to the full data, rheumatologists and other experts have raised serious concerns about how the medication should be prescribed and question whether the FDA will be required to further restrict user of the medication, or even potentially recommend a Xeljanz recall. However, health experts caution that users should not stop taking the medication without first consulting with their own healthcare provider.

Former users are now contacting lawyers who are investigating Xeljanz lawsuits and class action claims, to seek additional information which has not been disclosed and compensation for treatments they may now require.