On Monday, AbbVie (AbbVie (ABBV)) agreed to buy Apogee Therapeutics (Apogee Therapeutics (APGE)) in an all-cash deal worth roughly $10.9 billion. It's the company's largest acquisition since it bought Botox-maker Allergan for $63 billion back in 2020. In recent years, AbbVie has also snapped up cancer-drug specialist ImmunoGen for $10.1 billion and Cerevel Therapeutics (neurological diseases) for about $8.7 billion. So this is a company that's not shy about writing big checks.

The prize here is zumilokibart, an experimental drug for inflammatory and respiratory conditions. William Blair analysts, led by Matt Phipps, weighed in on Monday with a mixed but ultimately bullish take. "While we do consider the nearly $11 billion price tag for an asset that will not be accretive until 2032 to be fairly expensive, the lead asset zumilokibart clearly fits within a therapeutic area where AbbVie has had commercial success for over a decade and offers the potential to further expand the company’s I&I pipeline into respiratory indications," they wrote.

In other words: yes, it's pricey, but it's a smart fit. AbbVie has been a powerhouse in immunology and inflammation (I&I) for years, with drugs like Humira and Rinvoq. Zumilokibart could extend that dominance into respiratory diseases like asthma and eczema.

The timing also matters. By buying Apogee now, AbbVie can accelerate Phase 3 development of zumilokibart and reduce future royalty payments to Blackstone Life Sciences, which had previously helped fund the drug's development. That, Phipps argues, justifies the near-term dilution to earnings.

AbbVie highlighted some impressive early data. In a trial for atopic dermatitis (eczema), zumilokibart achieved an EASI100 rate—meaning complete clearance of skin lesions—of 16.5% versus 3.4% for placebo. That nearly matches Rinvoq's 14.8% EASI100 rate at week 16. For context, Rinvoq is a blockbuster that brought in over $4 billion in sales last year. If zumilokibart can come close to that, the $11 billion price tag starts to look like a bargain.

The potential doesn't stop there. AbbVie sees opportunities for fixed-dose combinations, including with the TSLP antibody APG33, which could treat a broader range of inflammatory conditions. That's the kind of pipeline expansion that keeps a franchise growing through the 2030s.

William Blair reiterated an Outperform rating on AbbVie, signaling confidence in the long-term outlook despite the hefty upfront cost. Investors seemed to agree: AbbVie shares were up 2.12% at $234.88 on Tuesday.

In January, Apogee also shared interim data from a Phase 1b trial of zumilokibart in mild-to-moderate asthma. The drug showed robust and durable suppression of FeNO, a biomarker of Type 2 inflammation that correlates strongly with asthma exacerbations—and it did so after just a single dose. That kind of convenience could be a game-changer for patients.

So yes, $10.9 billion is a lot of money for a drug that won't start paying off for years. But if zumilokibart lives up to its early promise, AbbVie's immunology franchise could have another blockbuster on its hands—and the long-term upside might just make the near-term pain worth it.