Sales of drugs to treat ulcerative colitis in seven major markets are set to double over the next decade, reaching $3.7 billion by 2021, according new research.

This fast growth will be primarily driven by two premium-priced tumour necrosis factor-alpha (TNF-alpha) inhibitors - Abbott/Eisai's Humira (adalimumab) and Janssen/Merck/Mitsubishi Tanabe's Simponi (golimumab) - plus two novel therapies - Takeda's cell adhesion molecule (CAM) inhibitor vedolizumab and Pfizer's oral Janus-activated kinase inhibitor tofacitinib - says the report, from Decision Resources.

The market will also be boosted over this period by the expanding number of diagnosed prevalent cases of ulcerative colitis in the seven markets - France, Germany, Italy, Japan, Spain, UK and US, it adds.

Increased physician acceptance of TNF-alpha inhibitors for the treatment of moderate to severe disease, plus patient preference for convenient subcutaneous administration will fuel the uptake of the newer TNF-alpha inhibitors, Humira and Simponi, through the period to 2021, forecasts Decision Resources.

Owing to its perceived greater efficacy than Humira's in separate Phase III trials, plus favourable gastroenterologist opinion, Simponi will challenge the standing of Janssen/Merck/Mitsubishi Tanabe's intravenous Remicade (infliximab) as the most frequently-prescribed agent in the TNF-alpha inhibitor class. However, Remicade will remain the leader in terms of patient share among the TNF-alpha inhibitors, maintaining a relatively constant patient share across the seven markets, based on its well-established efficacy, although sales of Simponi will overtake those of Remicade in 2017, based largely on the former's premium price and assumed high dosing in ulcerative colitis, driving the market's growth as the new sales leader, says the report.

The launches of two premium-priced novel agents, vedolizumab and tofacinib, in 2014 and starting in 2016 respectively, will contribute to increasing sales over the period to 2021, gaining most initial use in the TNF-refractory population.

"These agents will likely extend the treatment algorithm by offering, for the first time, additional lines of therapy for patients with inadequate response to the TNF-alpha inhibitors," comments Decision Resources analyst Kathrina Quinn.

"Although the TNF-refractory market is relatively limited in size, the high unmet need for treatments that cater for this population and potentially delay or prevent colectomy will drive major-market sales of approximately $740 million in 2021, constituting about 20% total market share," she forecasts.

The report anticipates that, towards the end of the study period, vedolizumab and tofacitinib will begin to overtake use of Humira, as gastroenterologists move to another drug class after trying up to two TNF-alpha inhibitors. Even though vedolizumab's launch is expected to be first, uptake for tofacitinib will likely overtake that of vedolizumab, based on the strengths of its oral delivery and post-marketing safety data for other immune indications, it adds.