Not long ago there was only one JAK inhibitor, Pfizer’s Xeljanz, in development for the treatment of psoriatic arthritis (PsA). Two pieces of recent news have stoked renewed interest in JAK inhibitors’ potential in PsA. First, Xeljanz’s Phase III results were presented and well-received at the ACR conference in November 2016.1 Second, two months later, Xeljanz received an endorsement from the Committee for Medicinal Products for Human Use (CHMP) for the treatment of rheumatoid arthritis (RA), a move that also bodes well for the JAK inhibitors’ European market in PsA.2 Since then, Eli Lilly and Gilead have decided to jump on the bandwagon with their own JAK inhibitors, baricitinib and filgotinib, respectively, and conduct clinical trials in PsA. Therefore, by the end of 2017, there will be one JAK inhibitor under regulatory review, one in the midst of Phase III studies, and one in a Phase II study for PsA.

Currently, the only innovative oral therapy approved for PsA is Celgene’s Otezla, of which the annual sales in PsA and psoriasis combined in 2016 reached $1 billion, 116% up from one year before. Primary research conducted by DRG indicates that the new oral therapy is taking patient share away from biologics, including Humira, Enbrel, and Stelara. This trend is expected to continue at least in the short-term. However, thought leaders interviewed by DRG report their low satisfaction with the efficacy in patients taking Otezla. As a result, Xeljanz’s efficacy data exceeded the expectation for an oral therapy. Thereby, we can reasonably anticipate a fast pace of growth for JAK inhibitors in the PsA market, because they are clearly differentiated from the other new PsA therapies with their unique mechanism of action, oral formulation, strong efficacy, and real-world experience in RA—where Xeljanz received marketing approval by the FDA in 2012.

But, instead of asking how many JAK inhibitors we need for treating PsA, industry is more concerned with how big the oral inhibitor market in PsA is and whether it can sustain three or four JAK inhibitors—AbbVie has not yet announced the development plan for its JAK inhibitor, ABT-494, in PsA. The best market scenario for JAK inhibitors relies on stealing market share from both biologics and Otezla. We have conducted primary research to understand how likely rheumatologists are willing to prescribe Xeljanz compared with Otezla or biologics.3 Key factors that influence prescribing decisions were included in a conjoint analysis. This analysis is powerful to assess the competitiveness of an emerging therapy and to gauge the impact of an individual factor, such as a malignancy warning by the FDA, on physicians’ likelihood to prescribe, and share of preference. Based on the findings in the recently published Unmet Need report, JAK inhibitors are positioned in the fastest growing sector of the PsA market, but its limited size means that commercial success will be rewarded to those who seize the opportunity early.3

People may argue for other methods to size the market, but we must all agree that the JAK market is not as big as the TNF market that affords six different brands.



  1. Highlights of Psoriatic Arthritis Studies at the 2016 American College of Rheumatology Annual Meeting
  2. Summary of opinion (initial authorization) Accessed March 1, 2017
  3. Yang H.Psoriatic Arthritis | Unmet Need | Detailed, Expanded Analysis


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