Pfizer is continuing to pinball between oral obesity assets. Months after making twice-daily danuglipron its top prospect, the Big Pharma has dropped the program after more than half of people taking the drug candidate dropped out of a midphase clinical trial.
Danuglipron was cemented as Pfizer’s lead obesity asset in June after the company dropped its once-daily GLP-1 receptor agonist, lotiglipron, in response to a liver safety concern. Focusing on danuglipron left Pfizer with a treatment that is given more frequently than rival molecules from Eli Lilly, Novo Nordisk and Structure Therapeutics but kept it toward the front of the race for the oral market.
On Friday, Pfizer revealed phase 2b data that brought the curtain down on twice-daily danuglipron. The trial hit its primary endpoint, with participants experiencing placebo-adjusted weight reductions ranging from 8% to 13% at 32 weeks, but the treatment proved intolerable for many people.
Pfizer reported discontinuation rates in excess of 50% across all the studied danuglipron doses. Around 40% of subjects dropped out of the placebo cohort. Pfizer’s release lacks a detailed look at why patients left the study but the tolerability data on danuglipron offers a potential explanation. Up to 73% of people reported nausea. Rates of vomiting and diarrhea hit 47% and 25%, respectively.
Gastrointestinal side effects are a problem for other GLP-1 receptor agonists but the rates in Pfizer’s trial far exceed those reported in studies of the approved injectable medicines, Wegovy and Zepbound, that are sold by Novo Nordisk and Eli Lilly, respectively.
Pfizer dropped plans to take the twice-daily formulation of danuglipron into phase 3 in light of the data. A pharmacokinetic study of a once-daily formulation of danuglipron is continuing and will inform the next steps.
In theory, Pfizer could pivot to the once-daily formulation without breaking stride. Talking to investors on a quarterly results conference call in October, Mikael Dolsten, chief scientific officer at Pfizer, said “it's within our reach, if we decide to start the pivotal study next year, to do it with a once-a-day molecule.” At that time, Dolsten said a data drop that could inform the decision was scheduled for early next year.
If the once-daily formulation has the same tolerability problems, Pfizer will lose ground on its rivals but retain a space in the oral GLP-1 race. Earlier this year, the Big Pharma began a phase 1 trial of another GLP-1 asset, PF-06954522, that grew out of its work with Sosei Heptares. Discussing the asset, Dolsten told investors that Pfizer is “building a platform” around GLP-1 and has “a pretty strong effort here.”