Pfizer weight-loss drug data raises questions about side effects, shares fall

The Pfizer logo is displayed at the company's headquarters in New York. (AP Photo/Mark Lennihan, File)

Pfizer on Tuesday released trial data on a high-profile obesity drug from its recent US$10 billion Metsera purchase that raises questions about its tolerability for patients, and shares of the U.S. drugmaker fell more than three per cent.

The drug, given as a monthly injection, showed sustained weight loss at 28 weeks, Pfizer said, adding that it is targeting 2028 for its first approval in the fast-growing weight-loss drug market.

The company made the disclosure alongside reporting fourth-quarter earnings, which beat Wall Street estimates.

The latest data sets the stage for a year in which Pfizer said it plans to advance more than 20 clinical trials involving obesity treatments, an area that one day could help offset new competition for older drugs losing patent exclusivity.

“The foundation of our strategy in obesity and adjacent conditions is targeting breakthrough medicines in what could be a US$150 billion market,” CEO Albert Bourla said.

Bourla, in an interview, said the company is not concerned about price competition in the market even as obesity drugmaker Novo Nordisk warned on Tuesday that its profit and sales could drop this year, due in part to lower prices, especially in the U.S.

Prices “are higher than what we were estimating when we decided to move into the Metsera acquisition,” Bourla said. “So, no, we are not worried.”

Pfizer shares were down 3.5 per cent at $25.74.

Side effects lead to discontinuations

In a mid-stage trial, the treatment, known as PF-3944, led to up to 12.3 per cent weight loss in patients without diabetes, with no plateau observed at week 28, the company said, adding that it expects the trend to continue through the 64-week study.

Pfizer Chief Scientific Officer Chris Boshoff said the company is confident the drug “has the potential to deliver efficacy that is competitive with the standard of care.”

Daniel Barasa, portfolio manager at Gabelli Funds, called the drug’s reported weight loss “good, but not category-defining.”

If a monthly high dose can drive higher weight loss with a side effect profile that keeps patients on the medication, “Pfizer’s drug could offer a very compelling convenience trade-off versus weekly tirzepatide and semaglutide,” Barasa said, using the chemical names for Eli Lilly’s LLY.N Zepbound and Novo’s Wegovy.

Of around 108 patients who received the drug in two separate arms of the trial, 10 per cent dropped out due to adverse side effects.

Boshoff called the discontinuation rate similar to what you would expect for the GLP-1 class and noted that it did not increase when patients moved to a four-fold higher dose for the monthly shot.

But Gabelli’s Barasa said the reported dropouts raise the risk “that this climbs meaningfully by week 64, particularly at higher doses, and I don’t think physicians or payers will be enthusiastic if that plays out.”

Pfizer last year won a bidding war with Novo Nordisk for obesity drug developer Metsera, securing a foothold in the booming weight-loss drug market.

The company, which has warned of challenges over the next few years and does not expect to return to revenue growth until 2029, is banking on developing new blockbuster medicines, including obesity drugs acquired through recent deals, to help drive that recovery.

David Wagner, portfolio manager at Aptus Capital Advisors, was taking a cautious approach to Pfizer. “The big question is, will we see sizeable returns from their M&A spend, and will they make all the right development choices over this and next year to support the longer-term return to growth?”

Upbeat quarterly results

For the fourth quarter, the company saw sales rise to $17.56 billion, helped by sustained demand for the blood thinner Eliquis that Pfizer shares with Bristol Myers BMY.N and growth of its newer RSV vaccine Abrysvo. Analysts were expecting $16.95 billion in sales, according to LSEG data.

Abrysvo fourth-quarter sales of $481 million more than doubled Wall Street estimates of $170 million.

On an adjusted basis, the company reported a profit of 66 cents per share, topping analysts’ estimates by 9 cents.

Pfizer reaffirmed its 2026 forecast for revenue of $59.5 to $62.5 billion and adjusted earnings of $2.80 to $3.00 per share and said it reflects the expected hit from drug pricing deals with the Trump administration.

(Reporting by Mrinalika Roy in Bengaluru and Michael Erman in New Jersey, additional reporting by Sneha S K in Bengaluru; Editing by Bill Berkrot)