Key Highlights

  • Genmab (NASDAQ:GMAB) traded at USD 55.77 on October 28, 2026, up 24.85% on the day, up 42.71% over one week, up 60.44% over one month and up 98.33% over three months, in published market data.
  • On October 28, 2026 Genmab said the Phase 3 LiGeR-HN1 trial of petosemtamab with pembrolizumab met both primary endpoints at its first interim analysis, with an overall survival hazard ratio of 0.50.
  • European shares of Genmab (NASDAQ:GMAB) had already jumped 12% on October 26, 2026 after a late-stage trial update, and published accounts differ on whether that was the same readout.
  • The implied price a month ago is about USD 34.76, simple arithmetic on USD 55.77 and the 60.44% gain, and the shares are up 78.86% since the start of 2026.

The Trial Result Behind the Jump

The LiGeR-HN1 study tests petosemtamab plus pembrolizumab against pembrolizumab alone in first-line PD-L1-positive recurrent or metastatic head and neck squamous cell carcinoma. The company said both overall survival and objective response rate improved with statistical significance at the first interim analysis, with no new safety signals. A hazard ratio of 0.50 means a roughly 50% lower risk of death at any point, compared with the control arm. Interim analyses can end a study early when results cross a prespecified boundary. Genmab (NASDAQ:GMAB) said it plans to engage global regulators and present full data at a future medical meeting. The shares closed the session up 24.85% at USD 55.77 in published market data, after intraday coverage had shown a smaller gain near 16%, so the final size of the move should be read from official closing data.

From the Merus Deal to Late-Stage Data

Petosemtamab came from the Merus acquisition, which Genmab agreed in September 2025 at USD 97 a share in cash, about USD 8 billion, a 41% premium. The asset holds two FDA Breakthrough Therapy designations, and the company then targeted at least USD 1 billion of annual sales by 2029. On June 30, 2026 a separate Phase 3 study of epcoritamab with lenalidomide met its progression-free survival endpoint, cutting the risk of progression or death by 60% under US rules, and the shares rose 6.68% in Copenhagen. Jefferies kept a Buy rating with a target of 2,650 Danish kroner. Together the results show a company moving from licensing and royalties toward owning its late-stage cancer medicines, which raises both the reward and the cost of each readout.

Risks and What to Watch

Interim data are not full data, so duration of benefit, subgroup effects and safety detail remain to be seen. Approval is not guaranteed, the competitive field in head and neck cancer is crowded, and the Merus purchase added debt. After a 60.44% month and a 24.85% gain in one session, positive news is largely in the price. Investors can watch the medical meeting presentation, the regulatory submission timetable, any analyst target changes and the company's next quarterly report. A single trial does not remove commercial risk, because uptake depends on pricing, label and physician habits. Nothing here is a forecast of price or approval. This is not advice.

Where Things Stand

The answer is that the monthly surge reflects a string of late-stage results, with the October 28, 2026 LiGeR-HN1 interim analysis, showing a 0.50 survival hazard ratio, the largest single piece. Genmab (NASDAQ:GMAB) paid a high price for petosemtamab and now has data to support it, but full results, approval and competition are still ahead. The next catalysts are the medical meeting presentation and regulatory filings.