Uptake of alternative biologic treatments for rheumatoid arthritis (RA) such as Roche/Chugai’s Actemra/RoActemra (tocilizumab) will erode the market share of the tumour necrosis factor (TNF) alpha inhibitors over the next decade, says a new study.

Actemra/RoActemra will emerge as the likely preferred biologic agent for TNF-refractory patients with RA, and will garner blockbuster sales of approximately $1.5 billion in 2019 in France, Germany, Italy, Spain, UK, the US and Japan, according to the report, from Decision Resources (DR).

Sales of RoActemra/Actemra soared 198% during the first half of 2010 to reach 155 million Swiss francs, having rocketed 236% in the first quarter, Roche reported in late July. The product received US approval for use in the treatment of RA in January, and in June its approved indication in the European Union (EU) was expanded to include use in reducing the rate of progression of joint damage and improve physical function in RA patients, when given in combination with methotrexate.

Rheumatologists currently switch patients to an alternative biologic if they have responded inadequately to two TNF-alpha inhibitors, but the increasing trend will be to make the switch after one agent from this drug class is used, the DR report suggests. It also forecasts that, while TNF-alpha inhibitors such as Amgen/Pfizer/Takeda’s Enbrel (etanercept) and Abbott/Eisai's Humira (adalimumab) will continue to dominate RA treatment, the market share of TNF-alpha inhibitors will decrease from 75% in 2009 to 58% by 2019.

Second-quarter sales of Humira, which is approved for Crohn’s disease and psoriasis as well as RA, rose 21.5% to $1.59 billion, Abbott reported last month, and analysts at EvaluatePharma recently forecast that it will be the world’s top-selling drug by 2016, with sales rising 9% annually to reach $10.1 billion in that year. Meanwhile Amgen, which sells Enbrel in North America, announced that its sales of Enbrel had dropped 2% to $877 million during the second quarter.

The continued dominance of the TNF-alpha inhibitors and insight from experts interviewed for the DR study “clearly indicate that rheumatologists are relatively satisfied with the efficacy of the TNF-alpha inhibitors and place great importance on positive long-term safety and physician familiarity,” says Kyle Crowell, an analyst at the company. “New agents entering the RA market will be judged according to these standards and must show compelling advantages to be considered in the same line of therapy as the TNF-alpha inhibitors,”_ he adds.

The study’s findings also suggest that two agents currently in development for RA have the potential to disrupt the current treatment scheme. Pfizer’s oral Janus kinase-3 (Jak3) kinase inhibitor, tasocitinib (CP-690550), and AstraZeneca’s (formerly Rigel’s) spleen tyrosine kinase (Syk) inhibitor, fostamatinib disodium (R-788), are likely to find use ahead of the TNF-alpha inhibitors in the treatment algorithm and therefore divert a minority of patients away from TNF-alpha inhibitor therapy. Tasocitinib will have a stronger impact than fostamatinib disodium on the biologics market, owing to its earlier entry and robust clinical trial program, which includes a comparator trial with Humira, DR forecasts._

However, fostamatinib is the furthest-developed of the oral Syk inhibitors, and when in February AstraZeneca signed a deal with Rigel to obtain the rights to the drug - which could be worth almost $1.25 billion - analysts commented on its “blockbuster potential.”