Pfizer's Arena goal? Get out of the way and don't 'break the new toy'

Pfizer wasn’t about to meddle with the good work being done at Arena Pharmaceuticals, a biotech that attracted the Big Pharma into a $6.7 billion deal in December 2021.

“The worst thing we could do is come in and break the new toy,” Pfizer’s Michael Corbo, chief development officer for inflammation and immunology, told Fierce Biotech in an interview.

Five months after the deal, Arena’s team has delivered: Etrasimod, the immuno-inflammatory disease therapy that attracted the buyout, has been linked to a 27% remission rate in patients with ulcerative colitis (UC) in a phase 3 clinical trial.

Pfizer has already shouted from the rooftops that etrasimod met the clinical remission goal of the ELEVATE UC 52 study, but today the company is revealing the hard numbers behind that success. The clinical remission rate achieved with treatment compared to 7.4% for placebo for patients at Week 12. At Week 52, 32% of patients treated with etrasimod achieved clinical remission compared to 6.7% in the placebo group.

In the ELEVATE UC 12 study, the therapy achieved remission rates of 24% compared to 15% of those patients on placebo.

Corbo, who is integration lead for the acquisition, said when Pfizer was conducting its due diligence on Arena while considering the acquisition, a lot of the data that have come out on etrasimod in the past three or so months were not available. Pfizer teams got a peak at blinded data and some phase 2 results. Without that late-stage proof, Pfizer’s acquisition team had to rely on their gut instinct and the Arena team members they hoped would soon become their colleagues. Arena’s etrasimod UC team is led by Sheldon Sloan, M.D.

“One of the most important things is we got to actually know the team at Arena, and what we learned is we really trusted that they knew what they were doing,” Corbo said. “They were a talented group of people not only in drug design, but their ability to design and conduct GI studies.”

Ultimately, the decision to move forward with the deal was a “calculated risk,” according to Corbo—one that has now paid off and become favorable.  

Corbo said the Arena deal reflects where Pfizer is going with its entire approach to external science. The integration between the two companies is progressing well, with both sides already paired up as colleagues. Things moved a lot faster than expected after the Federal Trade Commission gave its nod to the transaction swiftly, Corbo said.

“The objective is really to support Sheldon and his team in progressing that filing in the way that they had planned to do it in their system,” Corbo said. “Our job is to actually help them in making it all come together, advising them where they need advice, but really making sure things go and ensuring that there's business continuity.”

Pfizer and the Arena team are aiming to file etrasimod to regulators by the end of the year, a target that has never wavered through the integration and remains “hideously predictable,” according to Corbo.

Going against JAK

ELEVATE UC 52 had a treat-through design, meaning patients are randomized to receive the treatment or placebo for the entirety of the study period. In a so-called induction, or re-randomization of responder trial design, patients who respond are re-randomized. The treat-through design means that the patient population remains relatively consistent, making for easy interpretation of study results. This can also help when response to treatment is expected to be delayed.

But, more importantly, Corbo says this design helps Pfizer get a sense of how durable etrasimod is for now, as long-term data are still to come for the therapy. This design reflects a push from the FDA to have UC trial patients treated for at least a year to determine efficacy, according to Corbo. And it provides a portrait of a more real-world patient experience, too, because some patients may simply take longer to have a response.

So what do these latest data mean in the grand scheme of UC? Pfizer doesn’t yet have head-to-head data against the biggest players in the disease, a market dominated by a who’s who of Big Pharma including AbbVie’s Humira and Rinvoq, Johnson & Johnson’s Stelara and Remicade and Takeda’s Entyvio.

Corbo said remission rates in the 20% and 30% range are "on par with” the biggest biologics in the field. It’s still unclear what label etrasimod will ultimately collect from the FDA if approved, so precisely what corner of the market it will go after is to be determined.

But there could be a hole to fill, as JAK inhibitors move to “more experienced” patients based on safety concerns that sprung up last year and led the FDA to tighten prescribing to later lines of therapy.

“JAK inhibitors are fantastic drugs; they're highly, highly efficacious,” Corbo said. “We see that etrasimod would probably be competing with patients that have a little bit less experience in their drug journey.”

Etrasimod is also being tested in a pivotal program for Crohn’s disease, and a phase 3 study for atopic dermatitis will kick off later this year. Readouts for phase 2 programs in eosinophilic esophagitis and alopecia areata are expected at the end of 2022 or early 2023.