Pfizer's Arena buyout looks canny, as etrasimod aces phase 3 trials

Pfizer placed a $6.7 billion bet on the outcome of two phase 3 trials of Arena Pharmaceuticals' etrasimod in ulcerative colitis (UC) when it acquired the company earlier this year, and the gamble seems to have paid off.

Yesterday, the company reported the results of the two trials of the S1P receptor modulator in patients with moderately-to-severely active UC at the Digestive Disease Week congress, with the data suggesting it could mount a strong challenge against rival Zeposia (ozanimod) from Bristol-Myers Squibb.

Treatment with etrasimod in the ELEVATE UC 12 was associated with a 25% clinical remission rate after 12 weeks, compared to 15% for a matched placebo group, in the first look at data first teased by the company in March.

Meanwhile, in the longer-term ELEVATE UC 52 study, remission was seen in 27% of etrasimod patients and 7% of the placebo group at the 12-week timepoint, and was 32% and 7% respectively after a year.

The remission data was accompanied by significant improvements in endoscopic measures of disease activity, symptomatic remission, and mucosal healing, said Pfizer.

The drugmaker said that the results suggest etrasimod could offer a "best-in-class" profile for UC, particularly as the ELEVATE UC 52 study used a treat-through trial design that "closely mimics real-world clinical practice."

The company is now planning to file for approval later this year, and while it will play catch-up with BMS and Zeposia – which got a green light in UC last year and is also approved for multiple sclerosis – analysts have suggested it could become a $3 billion-plus product.

If approved, etrasimod will also have to compete with other oral UC drugs like Pfizer's JAK inhibitor Xeljanz (tofacitinib), although the entire JAK class is under a cloud because of safety concerns, specifically an increased risk of blood clots.

"Etrasimod could offer a differentiated clinical profile for people living with moderately-to-severely active ulcerative colitis considering the clear benefit it has shown over 52 weeks in a treat-through trial design, its mechanism of action, and its unique pharmacologic properties," said Michael Corbo, Pfizer's chief development officer for inflammation and immunology.

Following after are etrasimod studies in Crohn's disease, eosinophilic oesophagitis, alopecia areata and atopic dermatitis, which if positive could dramatically increase the drug's potential.

BMS also has high expectations for Zeposia, saying it think sales could reach $5 billion if its indications can be extended to conclude Crohn's and other inflammatory diseases, although it still has a long way to go as 2021 sales were just over $130 million.