Genmab stock doubles in three months after a trio of cancer trial wins

Genmab just pulled off a three-month run most biotechs only dream about. The Danish drugmaker's roughly $35 billion valuation is backed by a share price that has nearly doubled since summer, capped by a 48% jump last week — including a 29% pop in a single session after its experimental head and neck cancer drug petosemtamab delivered strong Phase 3 results.

That Oct. 28 readout was the headline act. Petosemtamab combined with Merck's Keytruda reduced the risk of death by 50% compared with Keytruda alone in patients with recurrent or metastatic head and neck cancer, according to Genmab. Response rates improved significantly too, and no new safety signals turned up. CEO Jan van de Winkel told CNBC the combination could set "a completely new standard" of care, though he wouldn't say whether the survival data will hold as it matures.

October wasn't a one-hit month. Days earlier, Genmab said its medicine Rina-S reduced the risk of disease progression or death by 71% versus chemotherapy in a Phase 3 ovarian cancer trial, and cut the risk of death by 57%. Barclays analysts said that beat investor expectations and could offer an alternative for patients who can't take AbbVie's rival treatment Elahere, while cautioning that cross-trial comparisons have limits. A third late-stage win came from Epkinly, co-developed with AbbVie, which reduced the risk of progression or death by 51% alongside standard chemotherapy in previously untreated diffuse large B-cell lymphoma.

The wins matter because Genmab is rewriting how it makes money. For nearly three decades it collected royalties on drugs it helped develop — Johnson & Johnson's Darzalex and Novartis' Kesimpta among them. Van de Winkel said Darzalex is expected to generate $16.5 billion to $16.9 billion in sales this year, with Genmab taking royalties of up to 20%. Now it's using that firepower to keep a much bigger slice of its own treatments, fully owning petosemtamab (acquired through an $8 billion purchase of Merus in 2025) and Rina-S ($1.8 billion for ProfoundBio in 2024), and splitting Epkinly's economics evenly with AbbVie. "From now on I'm going to increasingly hold on to ownership of these new medicines," van de Winkel said.

Analysts are already sizing the prize. Jefferies estimates petosemtamab could hit $3.5 billion in peak annual global sales in its initial recurrent or metastatic market, with an expansion into locally advanced disease adding another $3.5 billion — an opportunity the firm thinks investors haven't fully priced in. Van de Winkel declined to give numbers but said he expects a "multi-billion dollar drug." Genmab now runs 15 Phase 3 trials across its three lead compounds and wants majority-owned medicines to reach about 500,000 patients by the 2030s, up from fewer than 30,000 today.