SUMMARY: The American Cancer Society estimates that for 2025, about 226,650 new cases of lung cancer will be diagnosed and 124,730 patients will die of the disease. Lung cancer is the leading cause of cancer-related mortality in the United States. Non-Small Cell Lung Cancer (NSCLC) accounts for approximately 85% of all lung cancers and Adenocarcinoma is now the most frequent histologic subtype of lung cancer.
The HER or erbB family of receptors consist of HER1, HER2, HER3 and HER4. HER2 is a Tyrosine Kinase Receptor expressed on the surface of several tumor types including Breast, Gastric, Lung and Colorectal cancers. It is a growth-promoting protein, and HER2 overexpression/HER2 gene amplification is often associated with aggressive disease and poor prognosis in certain tumor types.
HER2 mutations unlike HER2 overexpression and gene amplification are oncogenic drivers and are detected in 2 to 4% of NSCLCs. They are more often detected in younger, female and never-smokers, and almost exclusively in Adenocarcinomas. Next-generation sequencing is used to identify HER2 mutations. Majority of HER2 mutations (80-90%) occur in exon 20, as either a duplication or an insertion of 12 nucleotides, resulting in the addition of four amino acids (YVMA) at codon 775 in the kinase domain. This distinct molecular entity is characterized by specific pathological and clinical behavior. These acquired HER2 gene mutations have been independently associated with cancer cell growth, aggressive form of disease and poor prognosis, and with an increased incidence of brain metastases.
The FDA in 2022 granted accelerated approval to ENHERTU® (Trastuzumab deruxtecan), for adult patients with unresectable or metastatic NSCLC whose tumors have HER2 (ERBB2) mutations. This is the first drug approved for HER2-mutant NSCLC. Trastuzumab deruxtecan however can be associated with toxicities including Interstitial Lung Disease (ILD). Similarly, pan-HER TKIs such as Poziotinib and Pyrotinib have shown limited efficacy and are frequently associated with EGFR-related adverse events, underscoring the urgent need for more targeted, better-tolerated therapies.
Zongertinib is a novel, oral, irreversible Tyrosine Kinase Inhibitor designed to selectively target HER2 while sparing EGFR, thus minimizing common toxicities such as rash and diarrhea.
Beamion LUNG-1 is an ongoing Phase 1a/1b trial evaluating Zongertinib in previously treated patients with HER2-altered advanced or metastatic solid tumors (Phase 1a) and those with HER2-mutant advanced or metastatic NSCLC across multiple clinically relevant patient cohorts (Phase 1b). In the Phase 1a dose-escalation trial, Zongertinib showed encouraging preliminary activity at the recommended expansion doses of 120 mg and 240 mg once daily, with a low incidence of Grade 3 or higher adverse events.
The Phase 1b portion of the study evaluated Zongertinib in three key populations:
- Cohort 1: Patients with tumors harboring HER2 mutations in the TKD (Tyrosine Kinase Domain), the most common category of HER2 mutations encountered in the clinic.
- Cohort 5: Patients whose tumors had HER2 mutations within the TKD and had previously received HER2-directed ADCs, including Trastuzumab deruxtecan.
- Cohort 3: Patients whose tumor had HER2 mutations outside the TKD.
Patients were initially treated at 120 mg or 240 mg daily and following interim analysis, 120 mg was selected as the optimal dose based on a favorable efficacy and safety balance. The median age in Cohort 1 was 62 yrs. The Primary end point was an Objective Response Rate (ORR) assessed by Blinded Independent Central Review (Cohorts 1 and 5) or by Investigator Review (Cohort 3). Secondary end points included the Duration of Response and Progression-Free Survival (PFS).
Efficacy Outcomes
The median follow-up was 11.3 months at the data-cutoff date. Zongertinib demonstrated robust and durable activity, particularly in Cohort 1:
- Cohort 1 (N=75 at 120 mg daily dose):
- Objective response rate (ORR): 71% (P<0.001)
- Median Duration of Response (DoR): 14.1 months
- Median progression-free survival (PFS): 12.4 months
Importantly, responses were consistent across subgroups, including patients with brain metastases (ORR: 64%) and common TKD insertion subtypes such as A775_G776insYVMA (ORR: 81%).
- Cohort 5 (N=31):
- ORR: 48%, including patients previously treated with Trastuzumab deruxtecan (ORR: 42%)
- Cohort 3 (N=20):
- ORR: 30%
- Activity observed across several non-TKD mutations (e.g., S310X, V659E)
These findings suggest that Zongertinib may offer a viable treatment option even in patients who have progressed on ADCs or harbor atypical HER2 alterations.
Safety and Tolerability
Zongertinib was well tolerated across all cohorts:
- Grade ≥3 drug-related adverse events occurred in:
- 17% of patients in Cohort 1
- 3% in Cohort 5
- 25% in Cohort 3
- No cases of drug-related interstitial lung disease were observed
- Most common adverse event was diarrhea (any grade: 56%; grade ≥3: 1%), followed by rash (all grade ≤2)
The safety profile compares favorably with existing HER2-targeted agents, including Trastuzumab deruxtecan, which has reported interstitial lung disease rates of up to 26% in earlier trials.
Clinical Context and Future Directions
Compared with other HER2-targeted agents including Trastuzumab deruxtecan and investigational pan-HER TKIs, Zongertinib stands out for its high response rates, durability, and manageable toxicity. While cross-study comparisons have inherent limitations, these results support Zongertinib as a promising, HER2-selective oral agent for patients with HER2-mutant NSCLC. The ongoing Phase 3 Beamion LUNG-2 trial (NCT06151574) will further assess Zongertinib in the first-line setting, providing critical data on its role relative to current standard-of-care therapies.
Conclusion
Zongertinib has emerged as a strong candidate in the evolving landscape of HER2-mutant NSCLC. With high response rates, durable outcomes, and a favorable safety profile, it may soon offer oncologists a powerful new tool for treating this difficult-to-manage patient population.
Zongertinib in Previously Treated HER2-Mutant Non–Small-Cell Lung Cancer. Heymach JV, Ruiter G, Ahn M-J, et al. for the Beamion LUNG-1 Investigators. Published April 28, 2025. DOI: 10.1056/NEJMoa2503704
