Pfizer's Xeljanz fails RA safety study, making a tough rivalry with AbbVie's Rinvoq even tougher

Pfizer building
Pfizer is building its pipeline of JAK inhibitors in immunology but is facing competition from rivals like AbbVie. (Tracy Staton)

Pfizer has had a tough couple of years marketing its rheumatoid arthritis drug Xeljanz, as regulatory agencies have slapped warnings on the JAK inhibitor about potential cardiovascular side effects and cancer risk.

A new study promises to make the marketing challenge even greater.

The study, which was a post-marketing trial required by the FDA, compared Xeljanz to a TNF inhibitor in more than 4,300 patients over age 50 who had RA and at least one cardiovascular risk factor. There were 98 cases of cardiovascular events among the Xeljanz patients, versus just 37 in the TNF inhibitor group. And 122 patients taking Xeljanz developed cancers, compared with 42 on TNF inhibitors.

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Xeljanz thus missed the trial's primary endpoints, which were to show non-inferiority to TNF inhibitors in both cardiovascular and cancer risk. Two doses were tested, and both missed the mark, Pfizer said.

The result wasn’t entirely surprising, given the pileup of warnings on JAK inhibitors in recent years. In 2019, the FDA warned of an increased risk of blood clots and possibly death for patients taking 10 mg of Xeljanz twice daily. Pfizer had already flagged the safety issue and switched patients in a postmarketing study to the 5 mg dose, but the FDA was concerned enough to slap the dreaded “black box” warning on the drug.

The European Medicines Agency followed a few months later with a warning suggesting Xeljanz at any dose should be used with caution in patients who face a high risk of blood clots.

RELATED: Pfizer's Xeljanz gets EMA blood clots warning following FDA's similar move

And these days, Pfizer isn’t just facing competition from TNF inhibitors like AbbVie’s Humira.  It also has a tough rival in AbbVie’s JAK inhibitor Rinvoq, already approved to treat RA.

AbbVie is also pursuing an ulcerative colitis approval for Rinvoq. In December, the Illinois-based drugmaker released results from a phase 2b/3 study showing Rinvoq helped 26% of patients achieve remission at eight weeks, versus just 5% of patients taking a placebo.

It wasn't good news for Pfizer. Bernstein analyst Ronny Gal hailed Rinvoq’s "clear efficacy signal, better than Xeljanz, and within the ballpark of what has been seen across the UC field."

Pfizer has many second-generation JAK inhibitors in the pipeline, Gal acknowledged in a December report. “However, the field is getting more crowded with the approval of AbbVie's Rinvoq and multiple additional entrants in the next 18 months, and we are uncertain if Pfizer's strategy will play out.”

Gal estimates that Pfizer will report 2020 sales of Xeljanz of $2.4 billion and that the product will peak at just $2.8 billion in 2025 before losing patent protection in 2026.

RELATED: Pfizer may have a lot going on in immunology, but all its drugs could be beaten by rivals: analyst

Among Pfizer’s follow-ups in JAK inhibition is abrocitinib. The company is expecting an FDA decision on the drug in atopic dermatitis in April. That would pit Pfizer against Sanofi and Regeneron’s blockbuster Dupixent, and possibly Rinvoq. AbbVie is also gunning for the atopic dermatitis market and is expecting a verdict from the FDA in the second half of the year.

Pfizer has told analysts it expects abrocitinib to hit $3 billion in annual sales in atopic dermatitis, but with so much competition, Gal is skeptical. He estimates the drug will peak at $2 billion in that indication.

And the safety concerns swirling around the entire JAK class continue to worry analysts. During the annual J.P. Morgan Healthcare Conference in January, Pfizer CEO Albert Bourla was asked how marketers of JAK inhibitors could overcome perceptions of safety issues among dermatologists. Bourla said he’s not worried.

“We will develop the data, because in this country, you need to bring data and this is the beautiful thing about science and discovery,” he said. “But I feel that the benefits that [JAK inhibitors] bring clearly will outweigh any potential risks… because the data are strong.”