Genmab's Post-Darzalex Bet: One Validated Asset, Two Binary Readouts, and a $3.3B Cliff to Bridge

Genmab's Pivotal Oncology Readouts to Counter Darzalex Patent Cliff

Genmab is facing a significant challenge with the impending U.S. patent expiration of its cornerstone product, Darzalex, by 2029, which could see revenues plummet from $3.3 billion in 2028 to near zero by 2032. To mitigate this "cliff," the company is banking on three wholly-owned or partnered oncology assets. Recent positive Phase 3 data for Epkinly in first-line lymphoma and Phase 2 results for rinatabart sesutecan in ovarian cancer have set the stage, with critical Phase 3 readouts for petosemtamab in head and neck squamous cell carcinoma (LiGeR-HN1 trial) and rinatabart sesutecan (RAINFOL-02 trial) expected by year-end, which are crucial for Genmab's long-term growth.

• Strategic Imperative Amid Patent Cliff: Genmab is confronting an unprecedented financial challenge as U.S. patents for its key revenue driver, Darzalex, expire in 2029, threatening a drastic revenue decline. The company's strategy to overcome this "cliff" relies heavily on the successful development and commercialization of three oncology assets: Epkinly, petosemtamab, and rinatabart sesutecan, with pivotal clinical readouts anticipated to determine its future growth trajectory.
• Epkinly's Strong Phase 3 Performance: The AbbVie-partnered bispecific antibody, Epkinly, recently reported positive Phase 3 findings in first-line lymphoma, demonstrating a 51% improvement in progression-free survival when combined with a standard frontline regimen. Analysts suggest these results could establish Epkinly as a new standard of care, providing an early win for Genmab's pipeline diversification efforts.
• Petosemtamab: A Critical Blockbuster Candidate: Petosemtamab, a bispecific antibody targeting EGFR and LGR5 acquired through the Merus takeover, is considered Genmab's most critical asset, with its Phase 3 LiGeR-HN1 trial in first-line head and neck squamous cell carcinoma (HNSCC) expected to report results by year-end. Previous Phase 2 data showed a 63% overall response rate, significantly surpassing Merck's Keytruda, and a similar outcome in Phase 3 could support accelerated approval and rapid market uptake.
• Rinatabart Sesutecan's Potential in Ovarian Cancer: Genmab is also awaiting Phase 3 data from the RAINFOL-02 trial for its FRα-directed antibody-drug conjugate (ADC), rinatabart sesutecan, in platinum-resistant ovarian cancer. Building on positive Phase 1/2 data that showed a median PFS of 9.5 months (compared to a rival's 5.6 months), a positive outcome in RAINFOL-02, particularly if it demonstrates efficacy across FRα expression levels, could significantly expand its addressable market and establish it as a leading TOPO-1 ADC.

Addressing Unmet Needs in First-Line Head and Neck Squamous Cell Carcinoma

Despite meaningful advances in surgery, radiotherapy, chemotherapy, and immunotherapy, HNSCC remains a disease with persistently poor long-term outcomes and substantial treatment-related morbidity. Resistance to established systemic agents — both intrinsic and acquired — is a defining obstacle across all major therapeutic classes, and the 5-year overall survival for locally advanced disease remains approximately 50%.

• Limited efficacy of EGFR-targeted therapy. Cetuximab is the only EGFR-targeted agent approved for HNSCC, yet clinical response rates are modest despite EGFR overexpression in approximately 90% of tumors. Resistance arises through multiple mechanisms, including compensatory activation of alternative receptor tyrosine kinases, downstream pathway alterations such as PIK3CA mutations and PTEN loss, and epithelial-mesenchymal transition.

• Resistance to immunotherapy. Pembrolizumab and nivolumab are FDA- and EMA-approved PD-1 inhibitors for HNSCC, yet approximately 60% of patients with recurrent or metastatic disease do not respond, and only 20–30% remain free of disease progression in the long term. Resistance mechanisms include impaired antigen presentation, MYC amplification, enrichment of immunosuppressive cells such as tumor-associated macrophages and myeloid-derived suppressor cells, exploitation of alternative immune checkpoints (LAG-3, TIM-3, TIGIT/CD155), and upregulation of PD-L1 alongside downregulation of MHC class I — all of which collectively remodel the tumor microenvironment toward immune evasion.

• Failure of pembrolizumab plus chemoradiotherapy to improve survival in locally advanced disease. In the randomized, double-blind, phase 3 KEYNOTE-412 trial, pembrolizumab plus chemoradiotherapy did not significantly improve event-free survival compared with chemoradiotherapy alone in a molecularly unselected, locally advanced HNSCC population (hazard ratio 0.83 [95% CI 0.68–1.03]; log-rank p=0.043, significance threshold p≤0.024), underscoring the need for better patient stratification strategies.

• Substantial late toxicity burden from chemoradiation. Cisplatin-based chemoradiation, while improving overall survival relative to radiation alone, is associated with significant long-term toxicities: dysphagia (25%), xerostomia (40–80% depending on technique), hypothyroidism (42%), ototoxicity (27%), and osteoradionecrosis (4%). These toxicities compromise quality of life and are reported predominantly in retrospective studies, limiting the evidence base for their prevention and management.

• Heterogeneity of disease and absence of validated predictive biomarkers. HNSCC encompasses a genomically and immunologically heterogeneous group of tumors, with clinically distinct HPV-positive and HPV-negative subgroups. While biomarkers including PD-L1 expression, PD-L2 expression, HPV/p16 status, MYC amplification, and the interferon-gamma gene signature show potential to predict benefit from checkpoint inhibitor therapy, no validated biomarker-driven selection strategy has been established for routine clinical use.

• High recurrence rates and poor post-recurrence outcomes. Even with modern intensity-modulated radiotherapy, 15–50% of patients with HNSCC experience recurrence. Post-recurrence survival is strongly influenced by tumor subsite and HPV status — for example, median survival after locoregional failure was 36.5 months in HPV/p16-positive oropharyngeal carcinoma versus 13.6 months in HPV/p16-negative disease — and effective salvage options remain limited for the majority of patients.

LiGeR-HN1: Petosemtamab's Pivotal Phase 3 Trial Design and Endpoints

Several pivotal trials have evaluated novel systemic regimens across recurrent/metastatic and locally advanced HNSCC settings, spanning immunotherapy combinations, antibody-drug conjugates, and bispecific antibodies. The studies below represent a cross-section of phase 1b through phase 3 designs, with endpoints anchored to investigator-assessed response, survival, and safety.

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Petosemtamab's Competitive Edge in the HNSCC Treatment Landscape

Petosemtamab is a bispecific antibody targeting EGFR and LGR5 with enhanced antibody-dependent cellular cytotoxicity (ADCC), being evaluated in recurrent/metastatic (R/M) HNSCC. Several other bispecific antibodies sharing the broader mechanistic rationale of dual-target EGFR-directed ADCC or EGFR-plus-second-target inhibition are also in clinical development for R/M HNSCC, offering a meaningful competitive context for clinical and strategic teams.

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Genmab's Strategic Oncology Bets to Counter the Darzalex Cliff

The pharmaceutical landscape is unforgiving, and Genmab's impending Darzalex patent expiration by 2029 serves as a stark reminder of the constant need for innovation and pipeline strength. With a projected revenue drop from $3.3 billion to near zero in just a few years, the company's future hinges on the success of its strategic oncology assets. Recent positive Phase 3 data for Epkinly in first-line lymphoma and promising Phase 2 results for rinatabart sesutecan in ovarian cancer offer a glimpse of hope, but the upcoming Phase 3 readouts for petosemtamab in head and neck squamous cell carcinoma and rinatabart sesutecan are truly make-or-break moments.

Epkinly, a CD3xCD20 bispecific antibody, has already demonstrated remarkable efficacy and a manageable safety profile in relapsed/refractory diffuse large B-cell lymphoma (DLBCL), including in heavily pretreated and transplant-ineligible patients. Its subcutaneous administration and potential for outpatient monitoring offer significant patient convenience, positioning it as a strong contender against existing CAR-T therapies and traditional chemotherapy. However, the market for B-cell lymphomas is increasingly crowded with other bispecifics and cellular therapies, demanding clear differentiation and robust real-world performance.

Rinatabart sesutecan, an antibody-drug conjugate targeting folate receptor alpha (FRα), holds promise for ovarian cancer, particularly in the platinum-resistant setting where treatment options are limited. Research indicates that FRα is frequently overexpressed in these tumors, making it an attractive target. Yet, the success of such targeted therapies relies heavily on accurate patient selection, and studies have shown variability in FRα expression across different tumor types and potential for interpretive challenges in diagnostic testing.

Finally, petosemtamab, an EGFR/LGR5 bispecific antibody, represents Genmab's foray into a challenging solid tumor indication, head and neck squamous cell carcinoma. While EGFR is a known oncogenic driver, the complexity of solid tumor biology and the aggressive nature of HNSCC mean that even promising early data must translate into significant clinical benefit in pivotal trials. The outcomes of these trials will not only dictate Genmab's financial trajectory but also significantly impact treatment paradigms for patients facing these difficult-to-treat cancers. The company's ability to navigate these scientific and market challenges will define its post-Darzalex era.