Targeting heterogeneity in atypical epidermal growth factor receptor-mutated non-small cell lung cancer: insights from CHRYSALIS-2

Introduction

Emergence of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) has fundamentally reshaped the landscape of non-small cell lung cancer (NSCLC) treatment. Patients harboring classical EGFR mutations, particularly exon 19 deletions and L858R substitutions, benefit substantially from EGFR-targeted therapies, which have been associated with markedly longer survival and better quality of life than was conventional chemotherapy. Current international guidelines, including those from the National Comprehensive Cancer Network and the European Society for Medical Oncology, recommend the use of third-generation EGFR-TKI-based strategies as the preferred first-line treatment for advanced EGFR-mutated NSCLC. The phase III FLAURA trial established osimertinib as a standard first-line therapy, demonstrating significantly longer progression-free survival (PFS) and overall survival (OS) than did first-generation EGFR-TKIs (gefitinib or erlotinib), with a median OS of 38.6 vs. 31.8 months and a hazard ratio (HR) of 0.80 (1,2). More recently, studies have explored treatment intensification strategies. Indeed, the FLAURA2 trial showed that the combination of osimertinib and platinum-based chemotherapy promoted better OS than did osimertinib monotherapy (median OS 47.5 vs. 37.6 months; HR 0.77), suggesting that upfront combination therapy may further delay resistance in selected patients (3,4). Similarly, the MARIPOSA trial, a global phase III study that introduced a novel antibody-based therapeutic strategy in the frontline setting, found that the combination of the EGFR/mesenchymal-epithelial transition factor (MET) bispecific antibody amivantamab and the third-generation EGFR-TKI lazertinib demonstrated superior PFS than did osimertinib monotherapy (median PFS 23.7 vs. 16.6 months; HR 0.70), establishing a new combination paradigm for EGFR-mutated NSCLC (5). Importantly, updated analyses have also suggested a survival advantage with this strategy. Another study including a longer follow-up revealed that the amivantamab-lazertinib combination demonstrated significantly better OS than did osimertinib, further supporting the clinical potential of dual EGFR/MET blockade in delaying resistance and improving long-term outcomes in EGFR-mutated disease (6). Together, these landmark trials highlight the rapidly evolving landscape of EGFR-mutated NSCLC treatment and underscore the ongoing efforts to further extend survival through reasonable combination approaches and resistance-directed therapies.

However, the remarkable therapeutic success of combination and targeted therapies has not been uniformly extended to patients with atypical EGFR mutations, which collectively account for approximately 10–15% of all EGFR-mutated NSCLC patients (7,8). Atypical EGFR mutations, including variants such as G719X, L861Q, and S768I, exhibit considerable structural and functional heterogeneity, which makes their sensitivity to currently available EGFR-TKIs variable and often unpredictable (9). Although second- and third-generation EGFR-TKIs (e.g., afatinib and osimertinib, respectively) have demonstrated activity in selected uncommon EGFR mutations, treatment responses remain inconsistent, and the optimal therapeutic strategy for this population remains uncertain (10,11). Recent prospective studies have further highlighted both the potential and limitations of EGFR-TKI monotherapy in this setting; for example, osimertinib demonstrated clinically meaningful activity in patients with uncommon EGFR mutations in the UNICORN phase II trial, while emerging phase II data also suggest that lazertinib demonstrates clinical activity in selected variants, underscoring persistent mutation-specific heterogeneity in treatment response (12,13).

Against this background, the CHRYSALIS-2 trial evaluating the combination of amivantamab, a bispecific EGFR/MET antibody, and lazertinib, a third-generation EGFR-TKI, represents an important step toward expanding targeted options for patients with atypical EGFR-mutated NSCLC (14). In this editorial, we discuss the clinical significance of the CHRYSALIS-2 trial and its implications for the evolving treatment paradigm of atypical EGFR-mutated NSCLC.

Overview of the CHRYSALIS-2 study

CHRYSALIS-2 is a multicenter, open-label phase I/Ib study designed to evaluate the effects of lazertinib alone or in combination with amivantamab in patients with advanced EGFR-mutated NSCLC who exhibited disease progression while on prior systemic therapies (14). This particular study specifically focused on patients with advanced NSCLC harboring atypical EGFR mutations, excluding those with tumors showing classical EGFR mutations and exon 20 insertions. This design allowed investigators to explore the clinical activity of the combination therapy in a molecular subgroup of patients who have been historically underrepresented in clinical trials.

Patients received amivantamab intravenously at a dose of 1,050 or 1,400 mg depending on their body weight combined with oral lazertinib administered at 240 mg daily. The primary endpoint of the study was the objective response rate (ORR), whereas the secondary endpoints included PFS, duration of response, and safety. These findings should also be interpreted in the context of prior prospective studies of EGFR-TKI monotherapy in uncommon EGFR-mutated NSCLC, including the UNICORN phase II trial (12), which demonstrated clinically meaningful activity but also highlighted substantial variability across mutation subtypes. Similarly, emerging phase II data have shown that lazertinib also demonstrates clinical activity in selected uncommon EGFR mutations, although treatment outcomes remain heterogeneous depending on mutation subtype, further underscoring the persistent variability of EGFR-TKI monotherapy in this population (13).

The combination therapy demonstrated clinically significant antitumor activity, achieving an ORR of approximately 52%, a median PFS of 11.1 months, and a median response duration of 14.1 months in the overall cohort, indicating robust clinical benefit. Notably, treatment-naïve patients who received the regimen exhibited higher response rates than those who had previously received treatment, with an ORR of 57% in treatment-naïve patients compared with 48% in previously treated patients, suggesting that earlier introduction of dual EGFR/MET blockade may further enhance therapeutic benefit in this molecular subgroup. Moreover, responses were observed across multiple atypical EGFR mutation subtypes, highlighting that the amivantamab-lazertinib combination has the potential to overcome the biological heterogeneity of atypical EGFR variants.

The safety profile of this combination was consistent with that reported previously on amivantamab-based regimens. The most frequent treatment-related adverse events included infusion-related reactions (56%), rash (67%), and paronychia (67%). Most of these events were grade 1–2 and were manageable with supportive care, although serious treatment-emergent adverse events (TEAEs) were observed in 22 patients (21%). Accordingly, 7 patients (7%) required treatment discontinuation due to TEAEs, whereas one treatment-related death was reported. These findings support the feasibility of the combination regimen in this patient population.

Biological rationale and structural heterogeneity of atypical EGFR mutations

The biological rationale for combining amivantamab with lazertinib in the treatment of patients with atypical EGFR-mutated NSCLC, a subgroup characterized by marked structural and pharmacologic heterogeneity, is particularly compelling. Structure-based analyses have demonstrated that atypical EGFR variants do not behave as a uniform biological entity but instead comprise multiple functional classes with distinct sensitivities to EGFR inhibition (7). In particular, Robichaux et al. showed that uncommon EGFR mutations can be grouped according to their structural and functional features, and that this classification correlates with differential sensitivity to currently available EGFR-TKIs. Unlike classical EGFR mutations, such as exon 19 deletions and L858R substitutions, atypical mutations affect diverse structural regions of the kinase domain and induce conformational changes that influence adenosine triphosphate (ATP) binding, inhibitor accessibility, and downstream signaling. For example, G719X mutations alter the phosphate-binding loop, whereas L861Q affects the activation loop, creating distinct structural changes that may modify drug sensitivity. These structural differences help explain the heterogeneous responses of atypical EGFR mutations to currently available EGFR-TKIs. Although G719X, L861Q, and S768I mutations may respond to second-generation inhibitors (e.g., afatinib), prior clinical studies have shown that the magnitude and durability of benefit vary across mutation subtypes and may be influenced by the presence of compound mutations (10). Similarly, third-generation inhibitors (e.g., osimertinib) have demonstrated clinical activity in selected uncommon mutations, including prospective evidence of efficacy in this setting; however, treatment outcomes remain heterogeneous across mutation subtypes, indicating that not all atypical variants derive comparable benefit from EGFR-TKI monotherapy (11,12). This clinical heterogeneity provides a strong rationale for exploring treatment strategies beyond EGFR-TKI monotherapy, including antibody-TKI combinations such as amivantamab plus lazertinib.

In this context, dual EGFR/MET targeting can serve as a complementary therapeutic strategy. Amivantamab, a fully human bispecific antibody targeting both EGFR and MET, binds to extracellular receptor domains and inhibits ligand-dependent signaling while promoting receptor internalization and degradation and inducing antibody-dependent cellular cytotoxicity (15). These multimodal effects support its potential relevance in atypical EGFR-mutated NSCLC, where structural diversity may limit the uniform efficacy of kinase-domain inhibition alone. Lazertinib complements this mechanism by potently inhibiting mutant EGFR signaling and favorably penetrating the central nervous system (16). Recent preclinical work has further strengthened this rationale by showing that the combination of lazertinib and amivantamab exerts enhanced antitumor activity across models of uncommon EGFR-mutated NSCLC, supporting the concept that combined extracellular receptor targeting and intracellular kinase inhibition may provide broader pathway suppression than EGFR-TKI monotherapy alone (17). Together, extracellular receptor targeting and intracellular kinase inhibition may induce a broader and more robust suppression of oncogenic signaling than would EGFR-TKI monotherapy, particularly in tumors with structurally diverse or compound atypical EGFR alterations.

Clinical implications for the evolving treatment paradigm

Apart from demonstrating clinical activity, the CHRYSALIS-2 study highlights a broader shift in the therapeutic management of EGFR-mutated NSCLC. For nearly two decades, targeted therapy involving small-molecule EGFR-TKIs directed against the intracellular kinase domain has been the primary treatment approach for this disease. Although this strategy has achieved remarkable success for classical EGFR mutations (1), its efficacy has been less consistent in tumors harboring atypical variants (7,10,11). Antibody-based approaches introduce a complementary strategy that extends beyond kinase inhibition. By targeting extracellular receptor domains and engaging immune-mediated mechanisms, agents such as amivantamab may provide additional layers of pathway suppression and may help overcome mutation-specific variability in kinase inhibitor sensitivity (15).

Other clinical trials evaluating amivantamab-based combinations have also supported this evolving treatment paradigm. In fact, the MARIPOSA trial demonstrated that amivantamab plus lazertinib induced better PFS than did osimertinib alone in treatment-naïve patients with EGFR-mutated NSCLC (5). More recently, the final OS analysis of MARIPOSA further reinforced the long-term clinical relevance of this strategy, supporting the broader therapeutic significance of dual EGFR/MET blockade in EGFR-mutated NSCLC (6). Similarly, the PAPILLON trial showed that adding amivantamab to platinum-based chemotherapy significantly improved PFS among patients with EGFR exon 20 insertion-mutated NSCLC (18).

Collectively, these studies suggest that antibody-based combination strategies that integrate receptor targeting, kinase inhibition, and immune-mediated mechanisms may represent increasingly important progress toward precision oncology for EGFR-mutated lung cancer.

Limitations and future challenges

Despite the promising results of the CHRYSALIS-2 trial, several limitations should be considered. First, considering that the study was a non-randomized early-phase trial with a relatively limited sample size, cross-trial comparisons with existing EGFR-TKIs should therefore be interpreted cautiously. Prospective randomized studies are warranted to compare the effects of amivantamab-lazertinib to established treatment strategies.

Second, the intrinsic biological heterogeneity of atypical EGFR mutations remains a major challenge. Structure-based analyses have found that uncommon EGFR variants encompass multiple functional classes with distinct conformational properties and variable sensitivity to targeted therapies (7). The presence of compound EGFR mutations, which are relatively common in this population, may further contribute to clinical variability. Recent prospective studies of third-generation EGFR-TKIs in uncommon EGFR-mutated NSCLC further emphasize that clinically meaningful activity does not eliminate substantial variability across mutation subtypes, reinforcing the need for more refined biologic stratification and biomarker-driven treatment selection (12).

Third, predictive biomarkers that identify patients most likely to benefit from antibody-based combination strategies remain limited. Although MET activation has been implicated as a bypass pathway in EGFR-mutated NSCLC, the extent to which MET dependence contributes to treatment response in atypical EGFR mutations remains unclear.

Understanding the mechanisms driving resistance to antibody-TKI combinations is essential for the development of next-generation targeted therapies. As treatment paradigms evolve toward increasingly complex combination strategies, continued translational research will be required to anticipate resistance evolution and guide rational therapeutic design (19).

Conclusions

The CHRYSALIS-2 trial provides compelling evidence that the combination of amivantamab and lazertinib can achieve meaningful clinical responses among patients with atypical EGFR-mutated NSCLC. Beyond its clinical results, the study highlights the potential of strategies targeting both EGFR and MET in addressing the biological complexity associated with uncommon EGFR mutations. As precision oncology continues to evolve, antibody-TKI combination therapies may represent a promising approach to expanding targeted treatment options for patients with uncommon EGFR-mutated lung cancer. The CHRYSALIS-2 trial underscores an important principle in modern cancer therapy, that is, overcoming oncogenic heterogeneity may require therapeutic strategies that extend beyond single-pathway inhibition.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Translational Lung Cancer Research. The article has undergone external peer review.

Peer Review File: Available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-2026-0295/prf

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-2026-0295/coif). H.M. reports receiving honoraria for lectures from Janssen Pharmaceutical K.K. The other author has no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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