Genmab shares jump 13% on colorectal cancer drug trial results

Genmab shares rose as much as 13% after it reported petosemtamab plus chemotherapy produced a 75% response rate among evaluable first-line patients with advanced colorectal cancer and 67% in second-line patients in a mid-stage, open-label, single-arm study. The data covered 79 patients, with median follow-up of 5.9 and 7.1 months, respectively; Genmab reported no treatment-related deaths, and drug-related side effects led to discontinuation in 5% and 3% of patients receiving FOLFOX and FOLFIRI, respectively. Genmab said the results support its ongoing Phase 3 trials and separately announced a Phase 1/2 collaboration with Incyte to study petosemtamab with INCB161734 and chemotherapy in KRAS G12D-mutated disease.

Analysis

The key valuation question is whether the response signal translates into durable clinical benefit beyond chemotherapy—not whether the headline response rate is high. Because the study is open-label and single-arm, it cannot isolate petosemtamab’s contribution; short follow-up and inclusion of unconfirmed responses make duration of response, progression-free survival, and the Phase 3 control-arm comparison the pivotal evidence. The infusion-reaction burden is also a potential treatment-delivery and tolerability constraint, even if discontinuations were limited in this dataset.

Near term, the sharp repricing in GMAB raises the risk of giveback if investors extrapolate early response data into approval odds. Over the next 1–3 months, focus on trial design, enrollment pace, and whether regulators or investigators view the signal as sufficient to support the ongoing Phase 3 program. Over 6–18 months, positive controlled data could support a meaningful competitive position; failure to improve durable outcomes over standard chemotherapy would undermine the thesis. The KRAS G12D combination adds an earlier-stage option, not near-term earnings visibility: INCY’s co-funding and drug supply create exposure, but the clinical and commercial payoff remains contingent on combination safety and efficacy. The main consensus risk is treating one promising response readout as proof of broad benefit across colorectal cancer subgroups.

Key Decisions for Investors

• Do not chase GMAB solely on the initial spike; treat the move as a catalyst-driven repricing and wait for follow-up on confirmed responses, duration of response, and PFS before adding exposure.
• For GMAB, use the Phase 3 comparator and durability data as thesis tests: materially weaker-than-control PFS or failure to sustain responses would falsify the efficacy case; favorable controlled results would support reassessment of the current risk premium.
• Treat INCY’s KRAS G12D collaboration as optionality rather than a near-term fundamental catalyst. Monitor Phase 1/2 safety, dose selection, and evidence that the combination adds benefit over chemotherapy before assigning material value.
• Avoid a forced GMAB/INCY pair trade: the programs have different maturity and exposure, and the supplied information does not establish relative valuation or the collaboration’s financial materiality.