Genmab Just Wrote an $8 Billion Check for One Cancer Drug

Why Genmab Wants to Be More Than a Platform Company

Genmab isn't exactly a stranger to bispecific antibodies. The company built its reputation on DuoBody, a proprietary platform for engineering these dual-targeting drugs. Its biggest commercial win so far is epcoritamab (sold as Epkinly), approved for certain blood cancers. The company also runs a deep pipeline of DuoBody-derived candidates across oncology, many developed through partnerships with heavyweights like AbbVie and BioNTech.

But there's a catch. Genmab has historically leaned on a licensing model, letting bigger pharma companies commercialize its innovations in exchange for royalties and milestones. It's a profitable strategy, but it means someone else controls the endgame. Think of it like writing hit songs for other artists: you get paid, but you never become the star.

This deal signals that Genmab wants to own the stage. Petosemtamab gives the company a late-stage cancer asset with blockbuster potential that it can develop and sell on its own terms. Genmab expects the deal to become EBITDA accretive (translation: profitable on a cash-flow basis) by the end of 2029.

Show Me the Money

Let's talk about how Genmab is paying for this. The $8 billion price tag is being funded through a combination of cash on hand and approximately $5.5 billion in new debt. That's a significant amount of leverage for a company that has historically run a fairly lean balance sheet.

The deal is structured as a tender offer, which means Genmab is going directly to Merus shareholders and asking them to sell their shares at $97 apiece. To close, at least 80% of Merus shares need to be tendered (though Genmab can lower that threshold to 75% if other conditions are met). After that, any remaining holdouts will be swept up through back-end transactions or Dutch court proceedings.

Importantly, there's no financing condition on the offer. That's Genmab's way of saying, "We have the money. This is happening."

The Elephant in the Waiting Room

The obvious risk? Petosemtamab's phase 3 data hasn't read out yet. Genmab is essentially paying $8 billion based on phase 2 results in 43 patients. Phase 2 trials are promising but small; plenty of drugs have looked spectacular in mid-stage testing only to stumble when put to the definitive test.

Bank of America reportedly valued the deal at around 3x expected peak sales, which is reasonable by biotech M&A standards. But "reasonable" assumes petosemtamab actually delivers in phase 3. If it doesn't, Genmab will have spent $8 billion on the biotech equivalent of a lottery ticket.

A Crowded Dance Floor

Genmab isn't making this move in a vacuum. The bispecific antibody space has become one of the most competitive corners of oncology, with more than 200 bispecific antibodies in clinical development. J&J, Roche, Amgen, Pfizer: everyone wants a piece of this market.

Most of the approved bispecifics so far target blood cancers, but the real land grab is in solid tumors. That's exactly where petosemtamab plays. Companies are racing to prove that bispecific antibodies can crack the solid tumor code, and whoever gets there first with convincing data will have a massive commercial advantage.

Merus also brings its Biclonics platform, a proprietary technology for building bispecific antibodies that competes directly with Genmab's own DuoBody system. The company already has one approved product, zenocutuzumab (Bizengri), which got the green light in December 2024 for rare NRG1 fusion-positive lung and pancreatic cancers. It's a small market, but it validates the platform's engineering capabilities.

The Bottom Line

This deal is Genmab planting its flag. After years of building technology and licensing it to others, the company is spending $8 billion to become its own best customer. It's acquiring a late-stage cancer drug with genuinely exciting data, a validated antibody platform, and a pipeline that slots neatly into its existing oncology ambitions.

The question isn't whether the strategy makes sense. It does. The question is whether petosemtamab's phase 3 results will justify the price tag. If the data holds up, this could look like a bargain in three years. If it doesn't, it'll be one of the most expensive "almost" stories in biotech history.

Either way, Genmab just made the boldest move of its 26-year existence. No pressure.

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