Improving patient selection through tumor genomic recharacterization to overcome resistance to targeted therapy: commentary on the final analysis of the INSIGHT trial

During the last two decades, several epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have been developed, revamping the therapeutic scenario of advanced non-small cell lung cancer (NSCLC) harboring activating EGFR mutations (1,2). The onset of mechanisms of resistance is an inevitable event under TKIs, making cutting-edge strategies based on tumor genomic recharacterization at progression needed to improve patient outcomes (3). The development of MET amplification is the most common off-target mechanism of acquired resistance to EGFR TKIs, occurring in 5–22% of cases treated with first and second-generation agents, in 19% of cases who received second-line osimertinib and in 15% of cases that received the third-generation EGFR TKI as first-line treatment (3). The amplification of MET leads to EGFR-independent phosphorylation of ERBB3 and downstream activation of the PI3K/AKT pathway, thus bypassing TKIs-induced EGFR inhibition (4). Preclinical studies have demonstrated the efficacy of combining EGFR TKIs and MET inhibitors in EGFR-mutant NSCLC with MET amplification (5). This evidence paved the way for the design of clinical trials aiming to explore the efficacy of combining EGFR and MET TKIs for patients with EGFR-mutant, MET-amplified NSCLC. The INSIGHT study is an open-label, phase Ib/II, multicentre, randomized trial conducted in Asia. The phase Ib part consisted of a single-arm dose escalation and dose confirmation study to establish the recommended phase II dose for tepotinib, a type Ib MET inhibitor, in combination with gefitinib, a first-generation EGFR TKI. Based on the results of the phase Ib part, the combination of tepotinib 500 mg and gefitinib 250 mg once daily was chosen for the phase II study (6).

The phase II part of the INSIGHT study investigated the efficacy of tepotinib plus gefitinib versus chemotherapy in patients with EGFR-mutant MET-altered NSCLC (7). Key inclusion criteria were designed to enroll patients older than 18 years of age with advanced or metastatic NSCLC harboring an activating EGFR mutation, who developed acquired resistance to prior first- or second-generation EGFR TKI (gefitinib, erlotinib, icotinib, or afatinib), negative for acquired EGFR T790M mutation, and with a MET amplification or MET overexpression detected at the time of progression. MET amplification was centrally evaluated by fluorescence in situ hybridization (FISH) on tumor tissue and was defined by a mean gene copy number (GCN) ≥5, or MET to centromere of chromosome 7 (CEP7) ratio of ≥2:1. MET overexpression was determined centrally by immunohistochemistry (IHC), defined as IHC 2+ (moderate) or 3+ (high). A tissue biopsy at the time of progression to EGFR TKI was therefore mandatory for inclusion in the trial. Patients were randomized to receive tepotinib 500 mg plus gefitinib 250 mg once daily, or chemotherapy (pemetrexed 500 mg/m², plus cisplatin 75 mg/m² or carboplatin (AUC 5–6), intravenously every 21 days) for up to six 21-day cycles followed by pemetrexed maintenance. In both arms, the treatment was continued until disease progression, intolerance, or consent withdrawal. The primary endpoint was progression-free survival (PFS) by investigator assessment. Secondary endpoints were PFS assessed by an independent review committee (IRC), overall survival (OS), objective response rate (ORR), best overall response (BOR), disease control rate (DCR), duration of response (DOR), and safety. Subgroup analyses in patients with MET amplification or high MET overexpression were preplanned.

Liam et al. presented the final analysis of the INSIGHT phase II with an extended follow-up (data cut-off September 3^rd 2021) compared to the previous 18-month analysis (6). A total of 31 (56%) patients received tepotinib plus gefitinib and 24 (44%) patients received chemotherapy (7). Due to difficulties in recruiting patients meeting the eligibility criteria, the study was prematurely closed with fewer patients than planned, and all analyses were considered exploratory. At a median follow-up of 57.5 months, considering the overall population, the primary endpoint was not met, with no differences in median PFS by investigator assessment between the two treatment arms [4.9 months for tepotinib plus gefitinib arm versus 4.4 months for the chemotherapy arm; stratified hazard ratio (HR) 0.67; 90% CI: 0.35–1.28]. The median OS was also similar between the two groups (17.3 months for the tepotinib plus gefitinib arm versus 19.5 months for the chemotherapy arm; stratified HR, 0.67; 90% CI: 0.34–1.32). The ORR was 45.2% in the tepotinib plus gefitinib arm versus 33.3% in the chemotherapy arm [stratified odds ratio (OR) 1.99; 90% CI: 0.56–6.87].

Focusing on the analyses conducted on patients with MET amplification (N=19/55, 34.5%), results suggested a promising activity of TKIs in combination with tepotinib and gefitinib. The median PFS by investigator assessment was significantly longer in the tepotinib plus gefitinib arm compared to that observed in the chemotherapy arm (16.6 versus 4.2 months, unstratified HR 0.13, 90% CI: 0.04–0.43); similar results were observed when considering the PFS by IRC. A significant clinical benefit was also obtained in terms of OS with the TKIs combination, with a median OS of 37.3 months in patients treated with tepotinib plus gefitinib versus 13.1 months in those treated with chemotherapy (unstratified HR 0.10; 90% CI: 0.02–0.36). In addition, higher ORR (66.7% versus 42.9%; OR 2.67, 90% CI: 0.37–19.6), DCR (91.7% versus 71.4%) and longer median DOR (19.9 versus 2.8 months) were reported in patients treated with tepotinib plus gefitinib compared to chemotherapy. Noteworthy, the duration of tepotinib plus gefitinib was more than 1 year in six patients (50.0%) and longer than 4 years in three patients. Interestingly, a correlation between longer duration of treatment with tepotinib plus gefitinib and higher MET GCN was observed. Tumors of the only two patients who were still receiving the treatment combination at data cut-off (after 56.5 and 51.1 months of treatment, respectively) were the only ones with more than 10 GCN of MET (13.9 and 13.3) at the time of progression to EGFR TKIs, suggesting a continuous biomarker nature of MET amplifications as previously observed in the literature (3). In the GEOMETRY, a multiple-cohort, phase 2 study evaluating the activity of capmatinib in patients with NSCLC harboring MET exon 14 skipping mutations or MET amplification, the ORR was higher in patients with MET GCN ≥10 (29% in previously treated patients and 40% in previously untreated patients) compared to patients with MET GCN <10 (8). These findings suggest that the number of MET GCN may inform on whether the MET amplification should be considered the actionable driver and, consequently, on the likelihood of deriving benefit from MET TKIs (9-11). A subgroup analysis of the PROFILE 1001 trial including 38 patients with MET-amplified NSCLC treated with crizotinib showed a clinically meaningful antitumor activity, with an ORR of 38% in patients with a high level of MET amplification (defined as MET-to-CEP7 ratio ≥4.0) compared to those with lower MET amplification levels (9). When studying MET amplifications, a debate on the best method of detection of the amplification and the definition of a cut-off often arises. Different assays are used to detect MET copy number changes, including FISH, quantitative reverse transcription polymerase chain reaction, and next-generation sequencing (NGS), each with its limitations, interobserver variability, and not well-established cut-off definition (12,13). In the case of MET copy number gain/amplification, the presence of polysomy should be discriminated from the focal gene event, because the second one is more likely to lead to oncogene addiction and, thus, be sensitive to MET TKIs (10,14,15). In fact, only MET GCN ≥5 with MET/CEP7 ratio greater than or equal to 2 by FISH significantly have been reported to impair the response to first-line EGFR TKI and to correlate with a shorter time to treatment failure (10). Currently, data regarding the concordance between FISH and NGS assays are still weak as they mainly come from small retrospective studies, and tissue FISH seems to be the detection method for MET amplification (16-18). In fact, some NGS-based assays do not assess CEP7, and therefore may detect an increase in copy number resulting from polysomy rather than from the focal MET gene amplification (3). A recent work presented at the 2023 American Association for Cancer Research annual meeting compared NGS, FISH and immunohistochemical staining (IHC) techniques for MET amplification detection (17). Authors used FISH as reference testing, distinguishing also MET polysomy from MET focal amplification, and included clinical outcomes under MET TKIs. Their results showed that MET focal amplification by NGS might be accurate in recognizing patients who can benefit from MET inhibitors. Another study established a method to distinguish MET polysomy from MET focal amplification by NGS, using FISH as a reference test, highlighting again its clinical relevance as only MET focal amplified tumors benefit from MET TKIs (19). Further investigation in wider cohorts is needed to provide a more accurate definition and standardization of MET amplification as a driver across techniques.

Of a total of 34 (61.8%) patients with high MET overexpression (IHC 3+), 19 were included in the tepotinib plus gefitinib arm and 15 in the chemotherapy arm. Tepotinib plus gefitinib significantly improved PFS by investigator assessment versus chemotherapy (median 8.3 versus 4.4 months, respectively; unstratified HR, 0.35; 90% CI: 0.17–0.74), as well as PFS by IRC, and OS (median 29.1 versus 17.9 months, respectively; unstratified HR, 0.44; 90% CI: 0.23–0.84). ORR was 68.4% in the tepotinib plus gefitinib arm versus 33.3% in the chemotherapy arm (OR, 4.3; 90% CI: 1.03–18.3). The DOR was longer in the tepotinib plus gefitinib arm (8.7 months) compared to the chemotherapy arm (2.8 months). As the authors pointed out in the discussion, a total of 17 patients (50.0%) with MET IHC 3+ also had MET amplification, which may have an impact on these results. The MET overexpression rate in unselected patients with NSCLC ranges from 15% to 70% and is associated with poor prognosis. Although MET overexpression can be found in association with MET amplification, exon 14 skipping mutations, and fusion, its presence does not imply a genomic alteration in the MET gene (12). Moreover, the significant intratumoral heterogeneity observed through immunohistochemistry (IHC) makes it hard to consider it as a predictive biomarker for targeted therapy (20). Several trials trying to investigate antibody-drug conjugated specific for MET as monotherapy or in combination with other TKIs to target MET overexpression in different settings, including after progression to EGFR TKIs, have shown promising results in terms of efficacy, while some studies are currently ongoing (3,21). Interestingly, in the INSIGHT trial, responses in patients with IHC 3+ MET overexpression and negative for MET amplification were observed. However, other MET alterations that could lead to MET overexpression and resistance to EGFR TKIs (e.g., MET fusions or MET exon 14 skipping mutations) were not assessed in this study, making not possible to exclude an underlying genomic alteration known to be sensitive to MET inhibition. Additional studies are needed to better understand the biological role of MET overexpression without genomic MET alterations after resistance to EGFR TKIs in EGFR-mutant NSCLC (22).

The combination of tepotinib and gefitinib in the INSIGHT phase II was well tolerated and led to a similar percentage of grade ≥3 treatment-related AEs (TRAEs) compared to the chemotherapy arm (51.6% versus 52.2%, respectively). The most frequently reported TRAEs in patients treated with tepotinib plus gefitinib were diarrhea (58.1%; grade ≥3: 9.7%), increased alanine aminotransferase (32.3%; grade ≥3: 3.2%), and peripheral edema (29.0%; grade ≥3: 6.5%); permanent discontinuation was reported in 3.2% of cases versus 4.3% with chemotherapy. The incidence of peripheral edema with tepotinib plus gefitinib (33.3%) was lower compared to the 51% observed with capmatinib in the GEOMETRY trial and to the 63% reported in the VISION trial with tepotinib (7,8,23). Peripheral edema is the most common adverse event for MET TKIs, and studies demonstrated that older age was associated with an increased risk of edema, independent of tepotinib exposure (24). The median age in the INSIGHT phase II trial was 59 versus 74 years in the VISION trial, in line with the evidence that EGFR mutations are more common in younger patients with NSCLC compared to MET mutations (7,23).

The major limitation of the INSIGHT trial was the poor recruitment, leading to an early conclusion of the study with a lower number of patients enrolled than planned; therefore, results should be considered exploratory due to the small sample size. One of the factors that may have contributed to low recruitment was the mandatory invasive tissue biopsy for the detection of MET alterations (7). The use of liquid biopsy represents a less invasive method to recharacterize tumor genomic at disease progression. To date, trials such as ORCHARD, SAVANNAH, and TATTON, investigating the MET TKI savolitinib plus osimertinib in patients with EGFR-mutant NSCLC developing acquired resistance due to MET alterations listed tissue re-biopsy among inclusion criteria (12). Recently, the evaluation of MET amplification using liquid biopsy techniques showed a very promising rate of concordance with tissue biopsy as well as a very notable sensitivity rate, although some studies showed that tissue analysis may detect higher rates of MET amplification because of a potential underestimation of gene amplifications when assessed through liquid biopsy (25,26).

In conclusion, the phase II INSIGHT trial failed to meet its primary endpoint of prolonged PFS with tepotinib plus gefitinib versus chemotherapy in patients with EGFR-mutant NSCLC that developed MET amplification or MET overexpression at the time of progression to EGFR TKIs. However, the TKIs combination showed promising activity in the preplanned subgroup analysis of patients that developed MET amplification as a mechanism of acquired resistance to EGFR TKIs. In patients with high MET overexpression (IHC 3+), an improvement in clinical outcomes has also been observed, but might be driven by the 50% of patients with tumors also harboring a MET amplification. These findings confirmed previous results of other trials testing the efficacy of MET plus EGFR TKIs in EGFR-mutant MET-altered NSCLC. What emerges from these studies is the need to better standardize the definition of MET amplification as a driver (both through FISH and NGS/PCR) across techniques and cut-offs, for a tailored selection of patients that can benefit from TKIs combinations. The support of digital pathology to reduce interobserver variability in FISH interpretation and orthogonal assays to confirm the presence of MET amplification might be explored in further studies (12). Moreover, the recharacterization of tumor genomic at the time of disease progression on tumor tissue or through liquid biopsy (in case reobtaining tumor tissue is not feasible), is essential to plan the subsequent treatment strategy tailored to tumor evolution. Co-occurring mutations in some genes, such as TP53, may impact on outcomes of patients with oncogene-addicted NSCLC treated with targeted agents (27). Whether the presence of these co-mutations may impair the efficacy of EGFR and MET TKIs combination in the setting of EGFR-mutant MET-altered NSCLC is still unknown. Comprehensive genomic profiling at the time of disease progression could provide new insights in this field, aiming to improve tailored clinical trial design. The good tolerance of the TKIs combination encourages the use of EGFR inhibitors plus MET inhibitors in selected cases after progression to EGFR TKI monotherapy, with a potentially significant improvement in patient outcomes compared to standard chemotherapy while not increasing the likelihood of developing severe toxicities. The results of several ongoing phase III trials (Table 1) are awaited to provide more robust findings and perspectives regarding the use of TKIs combinations in this setting.

Acknowledgments

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, AME Clinical Trials Review. The article has undergone external peer review.

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Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://actr.amegroups.com/article/view/10.21037/actr-23-29/coif). B.R. is advisory board member of AstraZeneca, Regeneron, Amgen, and had received honoraria from Targeted Oncology. J.V.A. is advisory board member of BMS and AstraZeneca, and provides consulting for Janssen and MSD. The other authors have no conflicts of interest to declare.

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