Dive Brief:

• An experimental obesity shot Pfizer got through a buyout of Metsera helped enrollees in a mid-stage trial lose significantly more weight than a placebo, spurring up to an 11% reduction over 28 weeks using a regimen that switched from a weekly to monthly dose after 12 weeks.
• When including only participants who completed the trial, the shot helped people lose up to 12 percentage points more of their body weight than those who received a placebo. Though cross-trial comparisons can be misleading, the results “look slightly inferior” to what was seen in testing of Eli Lilly’s blockbuster Zepbound at a similar timepoint, wrote Leerink Partners analyst David Risinger.
• Pfizer executives noted on a conference call that, going forward, they intend to test a far higher dose than they did in Phase 2 testing. Phase 3 trials starting later this year will involve a dose that’s double the highest one used in the Phase 2. The data released Tuesday “increase significantly our confidence” in that study, Chris Boshoff, Pfizer’s chief scientific officer, said on a call with analysts. But company shares fell as much as 5% before rebounding slightly.

Dive Insight:

Pfizer needs this drug, known as PF’3944, to work. The company spent $10 billion to buy its original developer Metsera after a contentious bidding war with Novo Nordisk. And that came after multiple failed attempts to develop obesity drugs in-house. Two were scrapped because of safety concerns.

Despite being years behind established as well as emerging weight loss medicines from Lilly and Novo, Pfizer is adamant that PF’3944 can play an important role in the future. The company believes that a therapy requiring only monthly maintenance dosing after an initial build-up will prove more convenient for patients, help them stay on treatment for longer and keep their weight down.

Like many Phase 2 studies, the 268-patient trial tested several dose levels and strategies to ramp up dosing over time to reduce side effects. It also compared how much weight loss, compared to a placebo, those approaches were able to produce.

On Tuesday, Pfizer reported data from three groups of that trial. One cohort received a two smaller, increasing doses before getting a 3.2 milligram monthly dose. Another group got three different doses before reaching a 4.8 milligram monthly dose. The rest received a placebo.

Counting only those enrollees who completed the trial on-treatment, the first group lost 10 percentage points more than a placebo after 28 weeks, while the second group lost 12 percentage points more. When including all participants — including those who stopped treatment early — the difference was 8 and 11 percentage points, Pfizer said.

The drug had achieved as high as a 14 percent “placebo-adjusted” difference in an earlier trial.

Pfizer described side effects as “predominantly mild or moderate.” One severe case of nausea and vomiting, respectively — the type of issues that cause people to stop taking obesity drugs — were reported. Because of that tolerability profile, Pfizer executives believe they can test a 9.6 milligram dose in Phase 3.

Ten people given PF’3944 discontinued because of adverse events, or nearly 10% of the people who got dose regimens planned to be included in late-stage testing. That discontinuation rate is higher than the 6% Lilly observed the Phase 3 trials testing Zepbound’s highest dose, Risinger wrote.

Boshoff, however, noted that there wasn’t a sudden jump in discontinuations or reported side effects when recruits moved from smaller doses to a higher, maintenance dose.