Despite the development of treatments with novel mechanisms of action (MOAs), the axial spondyloarthritis (axSpA) market is anticipated to experience only mild growth in coming years. This is mainly due to the looming threat of biosimilars in both the US and EU.

AxSpA is a disease group encompassing both ankylosing spondylitis (AS) and non-radiographic axial spondyloarthritis (nr-axSpA). These conditions are chronic autoinflammatory disorders of the sacroiliac joints and spine, an area also known as the axial skeleton. The disease is typically diagnosed in young adulthood to middle age (16–45 years) and has a seven- to nine-year delay of diagnosis.

A stagnant market

The axSpA market has historically been reliant on anti-tumour necrosis factor (TNF) therapies that have been available for over a decade. While the pipeline for drugs in late-stage development was lacking, recent developments have led to research on novel treatment mechanisms. This will be vital in treating the under-diagnosed nr-axSpA population.  

While most anti-TNF therapies have been approved for both AS and nr-axSpA in the 5EU, the US saw its first ever nr-axSpA approval in March 2019. More drug developers are also beginning to realise the importance of getting these disease-retarding treatments to nr-axSpA patients.

Current treatment options

Among currently marketed anti-interleukin (IL) 17 therapies for AS, Novartis’ Cosentyx (secukinumab) and Eli Lilly’s newly approved Taltz (ixekizumab) are both being tested in nr-axSpA patients. As for drugs in late-stage development for axSpA, UCB’s bimekizumab and Kyowa Hakko Kirin’s brodalumab are both being tested in AS and nr-axSpA patients simultaneously. The latter of these products is expected to launch in Japan only.

Such progression highlights a greater awareness of a historically under-diagnosed and under-treated patient demographic.

There are some treatments in late-stage development for AS patients only, specifically Pfizer’s Xeljanz (tofacitinib) and AbbVie’s Rinvoq (upadacitinib). Although these Janus kinase inhibitors have been proven to be effective in treating AS, safety concerns regarding the formation of blood clots from their use in rheumatoid arthritis patients has led to boxed warnings for both treatments, which may limit their uptake upon approval for AS.

The obstacle of biosimilars

Despite recently approved treatments and therapies in late-stage development with MOAs, the future growth of the axSpA market is expected to be mild due to the influx of biosimilars in both the US and the EU.

AbbVie’s Humira (adalimumab) was the leading axSpA drug in 2018. However, it is expected to earn significantly less by 2028 due to approval of adalimumab biosimilars in the EU in late 2018, and the expected approval of adalimumab biosimilars in the US in 2023. Many other originator anti-TNF drugs are expected to see biosimilar competition over the next decade, significantly cutting into sales of the originator products.

Key opinion leaders (KOLs) interviewed by GlobalData generally agreed that anti-TNF therapies were likely to remain the most prescribed treatments for axSpA patients. These KOLs cited regional treatment guideline recommendations that anti-TNFs be prescribed first. Treatment is only recommended to move on to anti-IL-17s in the event of failure (although these treatments are contra-indicated in patients with inflammatory bowel disease, a common comorbidity of axSpA).

Based on the 2019 update to the US treatment guidelines, JAK inhibitors are recommended as third-line treatments. These follow anti-TNFs and anti-IL-17s. KOLs also intimated that biosimilars will present a challenge as they are expected to be significantly cheaper than JAK inhibitors, despite the latter being small molecule therapies.

Overall, the mild growth of the axSpA market in the 7MM over the next decade can be attributed to new drugs with novel MOAs reaching the market, as well as label expansions into the nr-axSpA demographic. It will also be significantly hampered by the high cost of new drugs, and rheumatologist familiarity with readily available anti-TNF therapies.