Pfizer executives discuss anti-obesity drug Metsera

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Pfizer made one thing clear this week: He's officially back in the obesity race.

The drugmaker is focused on bringing to market treatments derived from its $10 billion acquisition of obesity biotech Metsera. On Tuesday, it released promising phase two trial data on an injection, called PF′3944, that is in the most advanced stage of development.

The experimental drug produced robust weight loss when taken once a month in a mid-stage trial, offering early evidence that the shot can be given less frequently than existing drugs without sacrificing effectiveness. That could be a boon for Pfizer after it faced several setbacks trying to gain a share of a market dominated by weekly shots from Eli Lilly and Novo Nordisk, along with Novo's new daily pill.

Obese or overweight patients lost up to 12.3% of their weight compared to placebo at week 28 in the ongoing phase two study. The company said no plateau was observed after patients moved to monthly dosing, suggesting continued weight loss is expected as the study continues through week 64.

But investors are still looking for full data from that trial, which will be presented at a medical conference in June. Pfizer also plans to launch 10 phase three studies on the shot, with the goal of achieving the first of several potential approvals in 2028.

I spoke with Pfizer CEO Albert Bourla and other top executives about this week's data and the company's broader anti-obesity strategy. This is what they had to say.

Bourla told CNBC that data shows the monthly product has a “very competitive profile in tolerability and efficacy.”

Pfizer plans to use a higher dose of the drug in phase three trials, and Bourla said it will produce efficacy and tolerability data that are “perhaps best in class, so better than anything else,” even though it is taken less frequently. The company's model predicts that the highest dose could result in a 16% weight loss by week 28.

In the phase two trial, patients started with weekly injections of the drug for 12 weeks before switching to a monthly dose.

Pfizer also plans to study people who take GLP-1 weekly and give them the option to switch to the company's monthly shot, said Dr. Jim List, Pfizer's director of internal medicine.

List said that's one of the selling points of the company's shot: It can serve as a more convenient maintenance treatment for patients to switch to.

“If you say, listen, I can give you one of these medications. This one you will take once a week for the rest of your life. But this one you will take once a week and you can also change it to once a month. Which one do you want?” Ready said. “It will always be the one with the most options.

He added that “the week doesn't work for everyone,” as some patients need to travel and can't keep their injections refrigerated.

Bourla said people who have been receiving weekly injections are also more likely to switch to another injection instead of an oral option.

“The oral route will be for people, but they didn't start with the needle,” he said. “As a result, I think monthly or longer-term products will probably become a standard, and we will be the first and hopefully the best.”

A key part of Pfizer's strategy for the PF′3944 shot is to combine it with another drug that targets an intestinal hormone called amylin, List said.

“We hope to achieve even greater weight loss with that combination than with this GLP-1 alone,” he said.

Amylin is a hormone cosecreted with insulin in the pancreas to suppress appetite and reduce food intake. Amylin treatments have a similar effect to GLP-1s like Zepbound and Lilly's Mounjaro, but some analysts and researchers say it could be easier for patients to tolerate and help them preserve lean muscle mass.

Pfizer said Tuesday that early data showed that the two drugs together caused an additive weight loss of 5% compared to placebo on day 8. Amylin alone also showed an 8.4% weight loss on day 36.

Both medications are ultra-long-acting, meaning they are designed to remain active in the body longer than existing treatments such as Wegovy de Novo and can be taken once a month.

Pfizer plans to share more data on the drug amylin at a medical conference in June. List said the company is advancing the product to phase two testing in the first half of this year.

On Tuesday, Pfizer also teased a possible GLP-1 shot that is dosed quarterly (once every three months) rather than monthly or weekly.

List said the shot will be “ultra-ultra-long acting,” so Pfizer will find a way for the drug to have a “slower degradation in the human body so it can certainly last longer” than PF′3944.

Chief Scientific Officer Chris Boshoff told CNBC that the vast majority of patients will prefer one injection and “obviously being monthly is going to be preferable to weekly, and probably quarterly maybe better than monthly.”

But List said it's still early days for that drug.

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