OSLO, Sept 29 (Reuters) - Denmark's Genmab has agreed to acquire Merus NV, a Nasdaq-listed Dutch biotech firm developing a head-and-neck cancer drug, for $8 billion in cash, the two companies said in a statement on Monday.

US-listed Merus shares jumped 20% in overnight trading, while Genmab dropped 2.9%.

The planned transaction was unanimously approved by the boards of directors of both companies, the companies said.

Merus is currently running two Phase 3 trials on the petosemtamab drug for head-and-neck cancer, with interim readouts of one or both trials anticipated in 2026, they said.

The deal would add petosemtamab to Genmab's late-stage pipeline of drug candidates, aligning with the Danish group's expertise in antibody therapy development and commercialisation in oncology, the companies said.

"Following the closing of the transaction, Genmab will have four proprietary programs expected to drive multiple new drug launches by 2027," the companies said in the statement.