Danish biotechnology company Genmab has doubled in value over three months after a series of positive cancer-drug trial results. The gains have added momentum to its strategy of owning more of the medicines it develops and commercializes.

The company’s shares rose 48% last week, including a 29% increase in one session, after results for experimental treatment petosemtamab. It was Genmab’s third successful Phase 3 trial announcement in October, following positive results for ovarian cancer treatment Rina-S and lymphoma drug Epkinly.

The strongest market reaction followed an Oct. 28 announcement that petosemtamab, given with Merck’s Keytruda, cut the risk of death by 50% compared with Keytruda alone in a trial involving patients with recurrent or metastatic head and neck cancer. Genmab also reported improved response rates and no new safety signals. CEO Jan van de Winkel said the combination could potentially set a new standard of care, while noting that the full data have not yet been published.

In the ovarian cancer trial, Rina-S reduced the risk of disease progression or death by 71% and the risk of death by 57% compared with chemotherapy. Barclays analysts said the results surpassed expectations, while cautioning that comparisons between separate trials have limitations. They suggested the drug could be an option for some patients who cannot receive AbbVie’s Elahere or whose cancer has progressed after treatment with it.

Epkinly, which Genmab developed with AbbVie, reduced the risk of disease progression or death by 51% when combined with standard chemotherapy in previously untreated diffuse large B-cell lymphoma.

Genmab’s history has largely been built on royalties from medicines developed with other companies, including Johnson & Johnson’s Darzalex and Novartis’ Kesimpta. Van de Winkel said Darzalex is expected to generate $16.5 billion to $16.9 billion in sales this year, with Genmab receiving royalties of up to 20%.

The company is now using that income to expand its portfolio of medicines it owns outright or shares more directly in. Genmab acquired petosemtamab through its $8 billion purchase of Merus in 2025 and obtained Rina-S in a $1.8 billion acquisition of ProfoundBio in 2024. It owns both drugs fully, while sharing Epkinly’s commercial economics equally with AbbVie.

The Merus acquisition involved substantial financial risk: Genmab borrowed $5.5 billion to help fund the deal, relying on royalty income as a backstop if petosemtamab failed. Van de Winkel said the company intends to retain ownership of a growing share of its future medicines.

Analysts see potential for petosemtamab beyond its initial target market. Jefferies estimated peak annual global sales of $3.5 billion for recurrent or metastatic head and neck cancer, with a possible further $3.5 billion if the treatment expands into locally advanced disease. Van de Winkel did not provide a sales estimate, but described it as a potential multi-billion-dollar drug.

Genmab specializes in antibody-based medicines, including bispecific antibodies that can bind to two targets on cancer cells at once. Petosemtamab targets EGFR and LGR5, aiming to interfere with signals that support cancer-cell growth and encourage the immune system to attack tumors.

The company has 15 Phase 3 trials across its three leading compounds. It is also building on commercial capabilities developed for existing treatments, expanding its sales presence in Europe and seeking to reach more cancer patients through community healthcare in the United States. Van de Winkel said he wants Genmab’s majority-owned medicines to reach about 500,000 patients by the 2030s, compared with fewer than 30,000 today.

Genmab is due to report third-quarter earnings on Nov. 5. Van de Winkel acknowledged that owning more of its medicines also brings greater responsibility for trial costs, regulatory approvals and sales, and that geopolitical changes and drug-pricing pressures could affect the company’s expansion plans. He said he remains focused on building an independent European biotech, despite potential interest from larger drugmakers.

Sources: CNBC Markets.