Pfizer Inc. (PFE) delivered a mixed bag of news on Tuesday, reporting mid-stage obesity drug trial results that looked pretty good on paper while posting quarterly earnings that beat Wall Street's expectations. The market's response? A collective shrug and a 5% stock decline in premarket trading.

The Weight Loss Story: Monthly Dosing Shows Promise

Pfizer released topline data from its Phase 2b VESPER-3 study examining PF'3944 (previously called MET-097i), a monthly maintenance obesity treatment for adults with obesity or overweight without type 2 diabetes. This isn't just any drug in their portfolio—Pfizer shelled out a massive $10 billion to acquire it through the Metsera deal, outbidding competitors in the red-hot weight loss market.

The ongoing 64-week study delivered statistically significant weight reduction, with up to 12.3% mean placebo-adjusted weight loss at week 28. Two dosing regimens planned for Phase 3 trials—Arms 1 and 3, representing low and medium monthly maintenance doses—achieved 10% and 12.3% placebo-adjusted weight loss, respectively.

What makes these results particularly interesting is that patients showed robust and continuous weight loss after switching to monthly dosing, with no plateau observed at week 28. Translation: people kept losing weight without hitting a ceiling, which is exactly what you want to see in an obesity drug trial.

The ultra-long-acting, injectable GLP-1 receptor agonist also maintained a well-tolerated safety profile through week 28, consistent with others in the GLP-1 class. Gastrointestinal side effects—the typical culprits with these drugs—were predominantly mild or moderate. No more than one instance of severe nausea or vomiting appeared in any dose group, and there were zero instances of severe diarrhea.

This follows earlier data from September 2025, when the VESPER-1 Phase 2b study showed weight loss of up to 14.1% after 28 weekly doses. Pfizer is clearly betting big here, planning to advance ten Phase 3 trials with PF'3944 in 2026 as part of an expansive clinical development program with more than 20 planned and ongoing studies.

Quarterly Earnings: Beating Expectations While COVID Fades

Beyond the obesity drug headlines, Pfizer reported fourth-quarter 2025 adjusted earnings of 66 cents per share, compared to 63 cents a year ago and beating the consensus estimate of 57 cents. Revenue came in at $17.56 billion, topping expectations of $16.96 billion despite falling 1% year over year—or 3% on an operational basis.

The revenue story is really two stories. COVID-19 products continued their expected decline, but growth in other areas helped offset the drop. Abrysvo, oncology biosimilars, Eliquis, the Prevnar family, the Vyndaqel family, and several other products across categories all posted increases. Strip out Comirnaty and Paxlovid entirely, and revenues actually grew 9% operationally for the quarter.

The COVID products tell a predictable tale of declining demand. Comirnaty sales hit $2.27 billion, down 35% operationally, mainly due to a narrower U.S. vaccination recommendation and delayed approval of the new variant vaccine. Paxlovid took an even bigger hit, plunging 70% operationally to $218 million, driven by lower COVID-19 infections across markets and reduced international government purchases.

The Core Portfolio Holds Steady

Pfizer's established drug portfolio delivered a solid performance. The Vyndaqel family of heart drugs increased 7% operationally to $1.69 billion. Blood thinner Eliquis grew 8% operationally to around $2.02 billion. Prevnar pneumococcal vaccine sales climbed 8% operationally to $1.71 billion.

Not everything went up, though. Cancer drug Ibrance saw sales fall 5% to $1.04 billion. Meanwhile, RSV vaccine Abrysvo reached $481 million in sales, continuing to gain traction in the respiratory vaccine market.

Looking Ahead: Guidance Unchanged

Pfizer reaffirmed its fiscal 2026 adjusted earnings guidance of $2.80 to $3.00 per share, compared to consensus estimates of $2.97. The company also maintained its 2026 sales guidance of $59.5 billion to $62.5 billion versus Wall Street's estimate of $61.06 billion.

That revenue guidance bakes in approximately $5 billion from COVID-19 products and an expected year-over-year negative revenue impact of roughly $1.5 billion from products losing exclusivity. The company also flagged anticipated headwinds from Most-Favored-Nation drug pricing, TrumpRx policies, and the impact of currently imposed tariffs.

Despite beating estimates and showing progress on its obesity drug pipeline, PFE stock was down 5.10% at $25.30 during premarket trading on Tuesday. Apparently, in the increasingly competitive obesity drug market, 13% weight loss isn't quite enough to move the needle for investors looking for the next blockbuster.