AstraZeneca and Daiichi Sankyo have reported a potentially important first-line expansion opportunity for Enhertu after the Phase 3 DESTINY-Lung04 study showed the antibody-drug conjugate significantly delayed disease progression in patients with unresectable or metastatic non-squamous non-small cell lung cancer carrying HER2 mutations. Median progression-free survival reached 14.3 months with Enhertu compared with 8.3 months for pembrolizumab plus pemetrexed and platinum chemotherapy, translating into a 37% reduction in the risk of progression or death. The hazard ratio was 0.63, with a P value below 0.0001.
The response data were also favorable. AstraZeneca reported an objective response rate of 70% for Enhertu against 44.5% for the immunotherapy-chemotherapy regimen, while median duration of response reached 13.4 months compared with 9.7 months. Those numbers support the case for moving HER2-directed therapy earlier in the treatment pathway rather than waiting until patients progress after conventional first-line treatment.
However, DESTINY-Lung04 is not yet a complete survival story. The interim overall survival analysis was immature, with only 46.9% of the planned events recorded. Median overall survival at the data cutoff was 29.3 months in the Enhertu arm and 33.1 months in the comparator arm, producing a hazard ratio of 1.15 with a wide confidence interval crossing one. AstraZeneca cautioned that subsequent treatment patterns were imbalanced and could confound the early survival picture, while formal overall survival testing remains ahead.
Why could first-line HER2-mutant lung cancer become an important new market for Enhertu?
HER2 mutations occur in an estimated 2% to 4% of non-squamous non-small cell lung cancers. That makes the population much smaller than the overall lung cancer market, but still commercially meaningful because lung cancer remains one of the world’s most commonly diagnosed cancers and leading causes of cancer mortality. Approximately 2.6 million lung cancer cases were diagnosed globally in 2024, according to figures cited by AstraZeneca, with non-small cell lung cancer representing about 85% of cases.
For patients with HER2-mutant disease, the major strategic question is when targeted treatment should enter the sequence. Enhertu already has an established role in previously treated HER2-mutant metastatic non-small cell lung cancer. DESTINY-Lung04 attempts to move that treatment to the first line, where the addressable patient pool is larger because patients have not yet been filtered by progression, declining performance status or other treatment eligibility constraints.
Earlier-line treatment can also generate greater commercial value through longer treatment duration. That matters for Enhertu because it has already become one of the most economically significant antibody-drug conjugates in global oncology. Combined Enhertu sales reported by Daiichi Sankyo and AstraZeneca reached approximately $2.96 billion during the first half of 2026, compared with roughly $2.29 billion a year earlier. AstraZeneca alone recorded about $1.72 billion in first-half Enhertu revenue, demonstrating why additional tumor types and earlier treatment lines have become central to the asset’s growth trajectory.
How meaningful is the 14.3-month progression-free survival result?
A 5.9-month improvement in median progression-free survival is clinically substantial in advanced lung cancer, particularly when accompanied by a markedly higher response rate. The study directly compared Enhertu with a widely used first-line approach built around Merck & Co.’s Keytruda, pemetrexed and platinum chemotherapy, meaning AstraZeneca did not merely outperform an outdated control regimen. The trial instead asks whether a molecularly targeted antibody-drug conjugate should displace immunotherapy-based treatment at the beginning of care for a biomarker-defined subgroup.
That distinction is important for precision oncology. Historically, immunotherapy plus chemotherapy has remained the default first-line treatment for many patients without one of the better-established actionable driver mutations. DESTINY-Lung04 strengthens the argument that HER2 mutations should be treated as an actionable driver at diagnosis rather than as information primarily used after first-line failure.
The response rate reinforces that argument. Seven in ten patients receiving Enhertu achieved an objective response, compared with fewer than half receiving pembrolizumab plus chemotherapy. If these outcomes translate into regulatory approval and guideline adoption, routine molecular testing for HER2 mutations at diagnosis becomes even more commercially and clinically important.
Why does the immature overall survival result require caution?
Progression-free survival can support regulatory decisions in oncology, but overall survival remains one of the clearest measures of whether a treatment ultimately extends life. At the interim cutoff, DESTINY-Lung04 had not demonstrated an overall survival advantage, and the numerical medians actually favored the comparator arm. The hazard ratio of 1.15 was imprecise, and the study was not mature enough for formal statistical testing.
There are plausible reasons the early result may not represent the final outcome. Almost half of patients in the comparator group subsequently received HER2-directed treatment, compared with substantially fewer in the Enhertu arm because those patients had already received the drug. AstraZeneca also identified differences in subsequent use of immunotherapy and chemotherapy, making treatment after progression an important potential confounder.
That does not guarantee the survival curve will eventually favor Enhertu. It means the data are incomplete. The appropriate interpretation is therefore that DESTINY-Lung04 delivered a strong and statistically persuasive progression-free survival result while leaving the overall survival question unresolved.
Could interstitial lung disease limit Enhertu’s first-line advantage?
Enhertu’s established risk of interstitial lung disease and pneumonitis remains one of the most consequential safety considerations as AstraZeneca and Daiichi Sankyo push the drug into earlier treatment settings. In DESTINY-Lung04, adjudicated drug-related interstitial lung disease or pneumonitis occurred in 20.8% of patients receiving Enhertu. The cases included five Grade 3 events, one Grade 4 event and four Grade 5 events, representing fatal outcomes in approximately 1.8% of treated patients.
Overall Grade 3 or higher treatment-related adverse-event rates were similar between the groups despite considerably longer Enhertu exposure, at 34.1% for Enhertu and 33.6% for the comparator. That broader safety comparison is reassuring, but it does not eliminate the importance of pulmonary toxicity because severe interstitial lung disease can be rapidly life-threatening and demands active surveillance, early recognition and treatment interruption.
The first-line setting raises the threshold further. Patients are generally less heavily pretreated and may have several therapeutic options available, which means clinicians must weigh a large progression-free survival advantage against a known toxicity that can occasionally be fatal. Real-world experience, physician familiarity and risk-management practices will therefore influence how quickly Enhertu can displace established first-line regimens.
What does another Enhertu expansion mean for AstraZeneca’s oncology strategy?
Enhertu has become a central pillar of AstraZeneca’s ambition to expand oncology revenue through antibody-drug conjugates. The drug already spans multiple HER2-expressing or HER2-mutated cancers, and each earlier-line move expands both the potential patient population and the duration over which eligible patients may receive therapy. AstraZeneca has set a broader target of reaching $80 billion in annual revenue by 2030, making large oncology franchises critical to the company’s growth algorithm.
The partnership with Daiichi Sankyo also provides AstraZeneca with one of the industry’s most commercially validated antibody-drug conjugate platforms at a time when competition in the modality has intensified. Roche, Gilead Sciences, Pfizer and numerous biotechnology companies are advancing competing antibody-drug conjugates, while newer payloads, targets and bispecific formats are widening the competitive landscape.
AstraZeneca shares have remained sensitive to clinical readouts across its increasingly broad oncology pipeline. The company’s New York-listed shares recently closed 2.25% higher at $163.78 in one session, while September 17 trading also showed gains after J.P. Morgan reiterated an Overweight view. Those moves cannot be attributed solely to DESTINY-Lung04 because AstraZeneca released several oncology updates around the World Conference on Lung Cancer and analyst actions were also influencing sentiment.
What happens next for Enhertu in HER2-mutant lung cancer?
Regulatory submissions are the most obvious next step if AstraZeneca and Daiichi Sankyo determine the dataset supports first-line approval. A successful label expansion could shift HER2 mutation testing from an important later-line consideration to an immediate treatment-selection requirement at diagnosis. Guideline committees would then have to determine where Enhertu fits relative to immunotherapy-chemotherapy combinations and how pulmonary risk should influence patient selection.
The mature overall survival analysis will remain particularly important. A confirmed survival advantage would substantially strengthen the case for using Enhertu first, while a persistent absence of overall survival benefit could create more debate over the appropriate sequence despite the strong progression-free survival improvement.
For now, DESTINY-Lung04 represents a commercially significant win with an important asterisk. AstraZeneca has demonstrated that Enhertu can keep first-line HER2-mutant lung cancer under control materially longer than a Keytruda-based regimen. The unresolved questions are whether that advantage ultimately extends life, how clinicians balance the interstitial lung disease risk, and how quickly the result can reshape the treatment pathway.
