A phase Ib/II study of cabozantinib (XL184) with or without erlotinib in patients with non-small cell lung cancer

Association of Hypokalemia Incidence and Better Treatment Response in NSCLC Patients: A Meta-Analysis and Systematic Review on Anti-EGFR Targeted Therapy Clinical Trials

Background

This meta-analysis was designed to explore the relationship between the level of serum potassium and the treatment effect of epidermal growth factor receptor (EGFR) antagonist in advanced non-small cell lung cancer (aNSCLC).

Methods

We searched phase II/III prospective clinical trials on treatment with EGFR antagonists for aNSCLC patients. The objective response rate (ORR) and/or the disease control rate (DCR) and the incidence of hypokalemia of high grade (equal to or greater than grade 3) were summarized from all eligible trials. Heterogeneity, which was evaluated by Cochran’s Q-test and the I² statistics, was used to determine whether a random effects model or a fixed effects model will be used to calculate pooled proportions. Subgroup analysis was performed on different interventions, line types, phases, and drug numbers.

Results

From 666 potentially relevant articles, 36 clinical trials with a total of 9,761 participants were included in this meta-analysis. The pooled ORR was 16.25% (95%CI = 12.45–21.19) when the incidence of hypokalemia was 0%–5%, and it increased to 34.58% (95%CI = 24.09–45.07) when the incidence of hypokalemia was greater than 5%. The pooled DCR were 56.03% (95%CI = 45.03–67.03) and 64.38% (95%CI = 48.60–80.17) when the incidence rates of hypokalemia were 0%–5% and greater than 5%, respectively. The results of the subgroup analysis were consistent with the results of the whole population, except for not first-line treatment, which may have been confounded by malnutrition or poor quality of life in long-term survival.

Conclusion

The efficacy of anti-EGFR targeted therapy was positively associated with the hypokalemia incidence rate. Treatment effects on the different serum potassium strata need to be considered in future clinical trials with targeted therapy.

Cabozantinib combination therapy for the treatment of solid tumors: a systematic review

Background:

Cabozantinib monotherapy is approved for the treatment of several types of solid tumors. Investigation into the use of cabozantinib combined with other therapies is increasing. To understand the evidence in this area, we performed a systematic review of cabozantinib combination therapy for the treatment of solid tumors in adults.

Methods:

This study was designed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses, and the protocol was registered with PROSPERO (CRD42020144680). On 9 October 2020, we searched for clinical trials and observational studies of cabozantinib as part of a combination therapy for solid tumors using Embase, MEDLINE, and Cochrane databases, and by screening relevant congress abstracts. Eligible studies reported clinical or safety outcomes, or biomarker data. Randomized and observational studies with a sample size of fewer than 25 and studies of cabozantinib monotherapy were excluded. For each study, quality was assessed using National Institute for Health and Care Excellence methodology, and the study characteristics were described qualitatively. This study was funded by Ipsen.

Results:

Of 2421 citations identified, 32 articles were included (6 with results from randomized studies, 24 with results from non-randomized phase I or II studies, and 2 with results from both). The most commonly studied tumor types were metastatic urothelial carcinoma/genitourinary tumors and castration-resistant prostate cancer (CRPC). Findings from randomized studies suggested that cabozantinib combined with other therapies may lead to better progression-free survival than some current standards of care in renal cell carcinoma, CRPC, and non-small-cell lung cancer. The most common adverse events were hypertension, diarrhea, and fatigue.

Conclusion:

This review demonstrates the promising efficacy outcomes of cabozantinib combined with other therapies, and a safety profile similar to cabozantinib alone. However, the findings are limited by the fact that most of the identified studies were reported as congress abstracts only. More evidence from randomized trials is needed to explore cabozantinib as a combination therapy further.

RET Inhibitors in Non-Small-Cell Lung Cancer

RET rearrangements are observed in 1-2% of non-small-cell lung cancer (NSCLC) patients and result in the constitutive activation of downstream pathways normally implied in cell proliferation, growth, differentiation and survival. In NSCLC patients, RET rearrangements have been associated with a history of non-smoking, a higher rate of brain metastasis at initial diagnosis and a low immune infiltrate. Traditionally, RET fusions are considered mutually exclusive with other oncogenic drivers, even though a co-occurrence with EGFR mutations and MET amplifications has been observed. Cabozantinib, vandetanib and lenvatinib are the first multi-kinase inhibitors tested in RET-rearranged NSCLC patients with contrasting results. More recently, two selective RET inhibitors, selpercatinib and pralsetinib, demonstrated higher efficacy rates and good tolerability and they were approved for the treatment of patients with metastatic RET fusion-positive NSCLC on the bases of the results of phase II studies. Two ongoing phase III clinical trials are currently comparing selpercatinib or pralsetinib to standard first line treatments and will definitively establish their efficacy in RET-positive NSCLC patients.

Rational Multitargeted Drug Design Strategy from the Perspective of a Medicinal Chemist

The development of multitarget-directed ligands (MTDLs) has become a widely focused research topic, but rational design remains as an enormous challenge. This paper reviews and discusses the design strategy of incorporating the second activity into an existing single-active ligand. If the binding sites of both targets share similar endogenous substrates, MTDLs can be designed by merging two lead compounds with similar functional groups. If the binding sites are large or adjacent to the solution, two key pharmacophores can be fused directly. If the binding regions are small and deep inside the proteins, the linked-pharmacophore strategy might be the only way. The added pharmacophores of second targets should not affect the binding mode of the original ones. Moreover, the inhibitory activities of the two targets need to be adjusted to achieve an optimal ratio.

HGF/c-MET pathway in cancer: from molecular characterization to clinical evidence

This review provides a comprehensive landscape of HGF/c-MET (hepatocyte growth factor (HGF) /mesenchymal-epithelial transition factor (c-MET)) signaling pathway in cancers. First, we generalize the compelling influence of HGF/c-MET pathway on multiple cellular processes. Then, we present the genomic characterization of HGF/c-MET pathway in carcinogenesis. Furthermore, we extensively illustrate the malignant biological behaviors of HGF/c-MET pathway in cancers, in which hyperactive HGF/c-MET signaling is considered as a hallmark. In addition, we investigate the current clinical trials of HGF/c-MET-targeted therapy in cancers. We find that although HGF/c-MET-targeted therapy has led to breakthroughs in certain cancers, monotherapy of targeting HGF/c-MET has failed to demonstrate significant clinical efficacy in most cancers. With the advantage of the combinations of HGF/c-MET-targeted therapy, the exploration of more options of combinational targeted therapy in cancers may be the major challenge in the future.

Synthetic lethality-mediated precision oncology via the tumor transcriptome

Precision oncology has made significant advances, mainly by targeting actionable mutations in cancer driver genes. Aiming to expand treatment opportunities, recent studies have begun to explore the utility of tumor transcriptome to guide patient treatment. Here, we introduce SELECT (synthetic lethality and rescue-mediated precision oncology via the transcriptome), a precision oncology framework harnessing genetic interactions to predict patient response to cancer therapy from the tumor transcriptome. SELECT is tested on a broad collection of 35 published targeted and immunotherapy clinical trials from 10 different cancer types. It is predictive of patients' response in 80% of these clinical trials and in the recent multi-arm WINTHER trial. The predictive signatures and the code are made publicly available for academic use, laying a basis for future prospective clinical studies.

Combination of HGF/MET-targeting agents and other therapeutic strategies in cancer

MET receptor has emerged as a druggable target across several human cancers. Agents targeting MET and its ligand hepatocyte growth factor (HGF) including small molecules such as crizotinib, tivantinib and cabozantinib or antibodies including rilotumumab and onartuzumab have proven their values in different tumors. Recently, capmatinib was approved for treatment of metastatic lung cancer with MET exon 14 skipping. In this review, we critically examine the current evidence on how HGF/MET combination therapies may take advantage of synergistic effects, overcome primary or acquired drug resistance, target tumor microenvironment, modulate drug metabolism or tackle pharmacokinetic issues. Preclinical and clinical studies on the combination of HGF/MET-targeted agents with conventional chemotherapeutics or molecularly targeted treatments (including EGFR, VEGFR, HER2, RAF/MEK, and PI3K/Akt targeting agents) and also the value of biomarkers are examined. Our deeper understanding of molecular mechanisms underlying successful pharmacological combinations is crucial to find the best personalized treatment regimens for cancer patients.

FGL1 regulates acquired resistance to Gefitinib by inhibiting apoptosis in non-small cell lung cancer

Background

This study investigated the role of fibrinogen-like protein 1 (FGL1) in regulating gefitinib resistance of PC9/GR non-small cell lung cancer (NSCLC).

Methods

The effect of different concentrations of gefitinib on cell proliferation were evaluated using the CCK-8 assay. FGL1 expression in the normal human bronchial epithelial cell line Beas-2B, as well as four lung tumor cell lines, H1975, A549, PC9, and PC9/GR, was investigated by using western blotting and qRT-PCR. FGL1 was knocked down using small interfering RNA to evaluate the effects of FGL1 on PC9 and PC9/GR. The correlation between FGL1 expression and gefitinib resistance was determined in vitro via CCK-8 and colony formation assays, and flow cytometry and in vivo via flow cytometry and immunohistochemistry.

Results

FGL1 expression was significantly upregulated in non-small cell lung cancer cells with EGFR mutation and higher in the gefitinib-resistant NSCLC cell line PC9/GR than in the gefitinib-sensitive NSCLC cell line PC9. Further, FGL1 expression in PC9 and PC9/GR cells increased in response to gefitinib treatment in a dose-dependent manner. Knockdown of FGL1 suppressed cell viability, reduced the gefitinib IC50 value, and enhanced apoptosis in PC9 and PC9/GR cells upon gefitinib treatment. Mouse xenograft experiments showed that FGL1 knockdown in PC9/GR tumor cells enhanced the inhibitory and apoptosis-inducing actions of gefitinib. The potential mechanism of gefitinib in inducing apoptosis of PC9/GR cells involves inhibition of PARP1 and caspase 3 expression via suppression of FGL1.

Conclusions

FGL1 confers gefitinib resistance in the NSCLC cell line PC9/GR by regulating the PARP1/caspase 3 pathway. Hence, FGL1 is a potential therapeutic target to improve the treatment response of NSCLC patients with acquired resistance to gefitinib.

Clinical Impact of the Epithelial-Mesenchymal Transition in Lung Cancer as a Biomarker Assisting in Therapeutic Decisions

Lung cancer is one of the most common solid cancers and represents the leading cause of cancer death worldwide. Over the last decade, research on the epithelial-mesenchymal transition (EMT) in lung cancer has gained increasing attention. Here, we review clinical and histological features of non-small-cell lung cancer associated with EMT. We then aimed to establish potential clinical implications of EMT in current therapeutic options, including surgery, radiation, targeted therapy against oncogenic drivers, and immunotherapy.

MicroRNA-128-3p Enhances the Chemosensitivity of Temozolomide in Glioblastoma by Targeting c-Met and EMT

Temozolomide is a first line anti-tumor drug used for the treatment of patients with Glioblastoma multiforme (GBM). However, the drug resistance to temozolomide limits its clinical application. Therefore, novel strategies to overcome chemoresistance are desperately needed for improved treatment of human GBM. Recent studies have demonstrated that miRNAs are closely related to resistance to cancer chemotherapy. This study aimed to further validate the biological role of miR-128-3p and to investigate whether miR-128-3p can enhance the chemosensitivity of glioblastoma to temozolomide (TMZ) and the underlying mechanisms. The effects of miR-128-3p and TMZ on the proliferation of glioblastoma cells were investigated by cell counting kit-8 (cck8). Transwell and intracerebral invasion assays were applied to determine the effects of the combination of miR-128-3p and TMZ on the invasion and migration of glioblastoma in vitro and in vivo. Flow cytometry was used to detect apoptosis in each group, and immunofluorescence was used to determine the expression levels of EMT-related proteins. RT-PCR and Western-blot were applied to detect EMT-transformed proteins (c-Met, PDGFRα, Notch1, and Slug) and EMT phenotype-associated proteins (Vim, CD44, and E-cadherin) at both mRNA and protein levels. Based on the microRNA.org database, we predicted the target genes of miR-128-3p. The target-relationship between miR-128-3p and c-Met and PDGFRα was verified by dual luciferase reporter gene. The tumor volume, weight and the expression levels of the proteins described above were measured in subcutaneously transplanted tumor model in nude mice. We found that the expression of miR-128-3p was down-regulated in glioblastoma tissue samples and cell lines. miR-128-3p suppressed the proliferation, migration, and invasion of GBM both in vitro and in vivo; miR-128-3p enhanced the therapeutic effect of TMZ via inhibition of proliferation, invasion and migration of glioblastoma cells and induction of apoptosis. Overexpression of miR-128-3p down-regulated the expression levels of EMT-transformed proteins (c-Met, PDGFRα, Notch1 and Slug) to enhance the effect of TMZ. In addition, we found that miR-128-3p targeted and bound c-Met. More importantly, the upregulation of c‐Met significantly prompted U87 and U251 cell proliferation. This effect could be abolished when c‐Met was silenced. The investigation in tumor bearing nude mice showed that miR-128-3p in combination with TMZ reduced tumor volume and the invasion extent, and increased the sensitivity of glioblastoma to TMZ. miR-128-3p is capable of enhancing the sensitivity of glioblastoma to TMZ through regulating c-Met/EMT.

First-in-human phase I study of BPI-9016M, a dual MET/Axl inhibitor, in patients with non-small cell lung cancer

Background

BPI-9016M is a novel small-molecule inhibitor that simultaneously targets both c-Met and AXL tyrosine kinases. This phase I study aimed to determine the maximum tolerated dose (MTD), safety, pharmacokinetics, and antitumor activity of BPI-9016M in Chinese patients with advanced non-small cell lung cancer (NSCLC).

Methods

Over the dose range of 100 mg to 800 mg, eligible patients were administered with a single dose of 9016M tablet and received 7 days of pharmacokinetics evaluation, followed by continuous dose administration (QD dosing, 28 days). Standard “3 + 3” dose escalations were performed.

Results

Twenty NSCLC patients were treated. All patients experienced at least one adverse event (AE), of which treatment-related adverse events (TRAEs) were reported in 17 (85.0%) patients. The most common TRAEs were alanine transaminase (ALT) elevation (60%), bilirubin increased (40%), dysgeusia (40%), constipation (30%), hypertension (25%), and palmar-plantar erythrodysesthesia syndrome (15%). The TRAEs of grade 3 or higher during treatment were hypertension (15%), pulmonary embolism (5%), and laryngeal pain (5%). No dose-limiting toxicity (DLT) was observed, and the MTD was not reached. The median time to C_max ranged from 2.0 to 3.5 h, and the plasma concentration of BPI-9016M declined rapidly after T_max fitting a single-compartment model. The mean AUC_0–72 h of M1 and M2-2, main metabolites of BPI-9016M, were 4.8–6.6 folds and 4.1–9.8 folds higher than that of BPI-9016M, respectively. Exposure to BPI-9016M, M1, and M2-2 reached moderate saturation at 600 mg. Among 19 evaluable patients, 1 had a partial response and 10 patients had stable disease.

Conclusion

BPI-9016M showed favorable safety and pharmacokinetic profiles, and no DLT was observed at doses up to 800 mg once daily. The promising antitumor activity in Chinese NSCLC patients supports further development of this tyrosine kinase inhibitor.

Trial registration

Clinical Trial ID: NCT02478866, registered May 21, 2015.

AXL receptor tyrosine kinase as a promising anti-cancer approach: functions, molecular mechanisms and clinical applications

Molecular targeted therapy for cancer has been a research hotspot for decades. AXL is a member of the TAM family with the high-affinity ligand growth arrest-specific protein 6 (GAS6). The Gas6/AXL signalling pathway is associated with tumour cell growth, metastasis, invasion, epithelial-mesenchymal transition (EMT), angiogenesis, drug resistance, immune regulation and stem cell maintenance. Different therapeutic agents targeting AXL have been developed, typically including small molecule inhibitors, monoclonal antibodies (mAbs), nucleotide aptamers, soluble receptors, and several natural compounds. In this review, we first provide a comprehensive discussion of the structure, function, regulation, and signalling pathways of AXL. Then, we highlight recent strategies for targeting AXL in the treatment of cancer.AXL-targeted drugs, either as single agents or in combination with conventional chemotherapy or other small molecule inhibitors, are likely to improve the survival of many patients. However, future investigations into AXL molecular signalling networks and robust predictive biomarkers are warranted to select patients who could receive clinical benefit and to avoid potential toxicities.

CuS Nanoparticles as a Photodynamic Nanoswitch for Abrogating Bypass Signaling To Overcome Gefitinib Resistance

Bypass signaling activation plays a crucial role in the acquired resistance of gefitinib, the first targeted drug in the clinic to treat advanced non-small cell lung cancer. Although the inactivation of bypass signaling by small-molecule inhibitors or monoclonal antibodies may overcome gefitinib resistance, their clinical use has been limited by the complex production process and off-target toxicity. Here we show CuS nanoparticles (NPs) behaved as a photodynamic nanoswitch to specifically abrogate overactive bypass signaling in resistant tumor cells without interfering with the same signal pathways in normal cells. In representative insulin growth factor-1 receptor (IGF1R) bypass activation-induced gefitinib resistant tumors, CuS NPs upon near-infrared laser irradiation locally elevated reactive oxygen species (ROS) level in tumor cells, leading to the blockage of bypass IGF1R and its downstream AKT/ERK/NF-κB signaling cascades. Consequently, laser-irradiated CuS NPs sensitized tumors to gefitinib treatment and prolonged the survival of mice with no obvious toxicity. Laser-irradiated CuS NPs may serve as a simple and safe nanomedicine strategy to overcome bypass activation-induced gefitinib resistance in a specific and controllable manner and provide insights into the treatment of a myriad of other resistant tumors in the field of cancer therapy.

Phase II Trial of Cabozantinib Plus Erlotinib in Patients With Advanced Epidermal Growth Factor Receptor (EGFR)-Mutant Non-small Cell Lung Cancer With Progressive Disease on Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor Therapy: A California Cancer Consortium Phase II Trial (NCI 9303)

Introduction: Mesenchymal epidermal transition and vascular endothelial growth factor pathways are important in mediating non-small cell lung cancer (NSCLC) tumorigenesis and epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI) resistance. We hypothesized that treatment with cabozantinib plus erlotinib in EGFR mutation-positive NSCLC following progression on EGFR TKI therapy may allow tumors to overcome this resistance or restore sensitivity to therapy regardless of T790M status. Methods: Patients with advanced NSCLC, known EGFR mutation and progressive disease on an EGFR TKI immediately prior to enrollment without intervening therapy were enrolled. Patients received erlotinib 150 mg and cabozantinib 40 mg daily. The primary endpoint was evaluation of efficacy by objective response rate. Secondary endpoints included assessment of progression free survival (PFS), overall survival, change in tumor growth rate, safety and toxicity, and the evaluation of specific EGFR mutations and MET amplification in pre-treatment tissue and plasma. Results: Thirty-seven patients were enrolled at 4 centers. Four patients had partial response (10.8%) and 21 had stable disease (59.5%). A greater than 30% increase in tumor doubling time was observed in 79% of assessable patients (27/34). Median PFS was 3.6 months for all patients. Diarrhea (32%) was the most common grade 3 adverse event; 3 patients had asymptomatic grade 4 elevation of amylase and lipase. Conclusions: Combination erlotinib and cabozantinib demonstrates activity in a highly pretreated population of patients with EGFR mutation and progression on EGFR TKI. Further elucidation of beneficial patient subsets is warranted. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT01866410.

Safety and Tolerability of c-MET Inhibitors in Cancer

The role of aberrant hepatocyte growth factor receptor (c-MET, also known as tyrosine-protein kinase MET)/hepatocyte growth factor (HGF) signaling in cancer progression and invasion has been extensively studied. c-MET inhibitors have shown promising pre-clinical and early phase clinical trial anti-tumor activity in several tumor types, although results of most phase III trials with these agents have been negative. To date, two small molecule c-MET inhibitors, cabozantinib and crizotinib, have been approved by regulatory authorities for the treatment of selected cancer types, but several novel c-MET inhibitors (either monoclonal antibodies or small molecule c-MET tyrosine kinase inhibitors) and treatment combinations are currently under study in different settings. Here we provide an overview of the mechanism of action and rationale of c-MET inhibition in cancer, the efficacy of approved agents, and novel promising c-MET-inhibitors and novel targeted combination strategies under development in different cancer types, with a focus on the safety profile and tolerability of these compounds.

Targeted therapies for advanced non-small cell lung cancer

Lung cancer is a serious health problem and the leading cause of cancer death worldwide, due to its high incidence and mortality. 85% of lung cancers are represented by the non-small cell lung cancer (NSCLC). Traditional chemotherapy has been the main treatment option in NSCLC. However, it is often associated with limited efficacy and overall poor patient survival. In recent years, molecular targeting has achieved great progress in therapeutic treatment of cancer and plays a crucial role in the current clinical treatment of NSCLC, due to enhanced efficacy on cancer tissues and reduced toxicity for normal tissues. In this review, we summarize the current targeting treatment of NSCLC, including inhibition of the epidermal growth factor receptor (EGFR), phosphatidylinositol 3-kinase (PI3Ks), mechanistic target of rapamycin (mTOR), epidermal growth factor receptor 2 (ErbB2), vascular epidermal growth factor receptor (VEGFR), kirsten human rat sarcoma protein (KRAS), mesenchymal-epithelial transition factor or hepatocyte growth factor receptor (c-MET), anaplastic lymphoma kinase (ALK), v-Raf murine sarcoma viral oncogene homolog B (BRAF). This article may serve as a guide to clinicians and researchers alike by assisting in making therapeutic decisions. Challenges of acquired drug resistance targeted therapy and imminent newer treatment modalities against NSCLC are also discussed.

Landscape of Acquired Resistance to Osimertinib in EGFR-Mutant NSCLC and Clinical Validation of Combined EGFR and RET Inhibition with Osimertinib and BLU-667 for Acquired RET Fusion

We present a cohort of 41 patients with osimertinib resistance biopsies, including 2 with an acquired CCDC6-RET fusion. Although RET fusions have been identified in resistant EGFR-mutant non-small cell lung cancer (NSCLC), their role in acquired resistance to EGFR inhibitors is not well described. To assess the biological implications of RET fusions in an EGFR-mutant cancer, we expressed CCDC6-RET in PC9 (EGFR del19) and MGH134 (EGFR L858R/T790M) cells and found that CCDC6-RET was sufficient to confer resistance to EGFR tyrosine kinase inhibitors (TKI). The selective RET inhibitors BLU-667 and cabozantinib resensitized CCDC6-RET-expressing cells to EGFR inhibition. Finally, we treated 2 patients with EGFR-mutant NSCLC and RET-mediated resistance with osimertinib and BLU-667. The combination was well tolerated and led to rapid radiographic response in both patients. This study provides proof of concept that RET fusions can mediate acquired resistance to EGFR TKIs and that combined EGFR and RET inhibition with osimertinib/BLU-667 may be a well-tolerated and effective treatment strategy for such patients. SIGNIFICANCE: The role of RET fusions in resistant EGFR-mutant cancers is unknown. We report that RET fusions mediate resistance to EGFR inhibitors and demonstrate that this bypass track can be effectively targeted with a selective RET inhibitor (BLU-667) in the clinic.This article is highlighted in the In This Issue feature, p. 1494.

Combined effect of cabozantinib and gefitinib in crizotinib-resistant lung tumors harboring ROS1 fusions

The ROS1 tyrosine kinase inhibitor (TKI) crizotinib has shown dramatic effects in patients with non‐small cell lung cancer (NSCLC) harboring ROS1 fusion genes. However, patients inevitably develop resistance to this agent. Therefore, a new treatment strategy is required for lung tumors with ROS1 fusion genes. In the present study, lung cancer cell lines, HCC78 harboring SLC34A2‐ROS1 and ABC‐20 harboring CD74‐ROS1, were used as cell line‐based resistance models. Crizotinib‐resistant HCC78R cells were established from HCC78. We comprehensively screened the resistant cells using a phosphor‐receptor tyrosine kinase array and RNA sequence analysis by next‐generation sequencing. HCC78R cells showed upregulation of HB‐EGF and activation of epidermal growth factor receptor (EGFR) phosphorylation and the EGFR signaling pathway. Recombinant HB‐EGF or EGF rendered HCC78 cells or ABC‐20 cells resistant to crizotinib. RNA sequence analysis by next‐generation sequencing revealed the upregulation of AXL in HCC78R cells. HCC78R cells showed marked sensitivity to EGFR‐TKI or anti‐EGFR antibody treatment in vitro. Combinations of an AXL inhibitor, cabozantinib or gilteritinib, and an EGFR‐TKI were more effective against HCC78R cells than monotherapy with an EGFR‐TKI or AXL inhibitor. The combination of cabozantinib and gefitinib effectively inhibited the growth of HCC78R tumors in an in vivo xenograft model of NOG mice. The results of this study indicated that HB‐EGF/EGFR and AXL play roles in crizotinib resistance in lung cancers harboring ROS1 fusions. The combination of cabozantinib and EGFR‐TKI may represent a useful alternative treatment strategy for patients with advanced NSCLC harboring ROS1 fusion genes.

Resistance to epidermal growth factor receptor tyrosine kinase inhibitors, T790M, and clinical trials

Tumours with sensitizing mutations in the EGFR gene constitute a distinct molecular subgroup of non-small-cell lung cancers (nsclcs) that benefit from precision medicine. First- and second-generation epidermal growth factor receptor (egfr) tyrosine kinase inhibitors (tkis) are recommended as upfront therapy for EGFR-mutated advanced nsclc and, compared with chemotherapy, have resulted in superior progression-free survival, improved tumour response rates, and improved quality of life. However, resistance inevitably develops, and the third-generation tki osimertinib has been approved to target the gatekeeper EGFR mutation T790M, which is responsible for resistance in 60% of cases. Multiple drivers of tki resistance have now been identified, and many new drugs are in development. With respect to this rapidly evolving field, our review highlights the current status of treatment options for patients with EGFR-mutated advanced nsclc, focusing especially on identified causes of resistance, challenges, and clinical trials aiming to improve outcomes in this patient population.

Understanding and targeting resistance mechanisms in NSCLC

The expanding spectrum of both established and candidate oncogenic driver mutations identified in non-small-cell lung cancer (NSCLC), coupled with the increasing number of clinically available signal transduction pathway inhibitors targeting these driver mutations, offers a tremendous opportunity to enhance patient outcomes. Despite these molecular advances, advanced-stage NSCLC remains largely incurable due to therapeutic resistance. In this Review, we discuss alterations in the targeted oncogene ('on-target' resistance) and in other downstream and parallel pathways ('off-target' resistance) leading to resistance to targeted therapies in NSCLC, and we provide an overview of the current understanding of the bidirectional interactions with the tumour microenvironment that promote therapeutic resistance. We highlight common mechanistic themes underpinning resistance to targeted therapies that are shared by NSCLC subtypes, including those with oncogenic alterations in epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), ROS1 proto-oncogene receptor tyrosine kinase (ROS1), serine/threonine-protein kinase b-raf (BRAF) and other less established oncoproteins. Finally, we discuss how understanding these themes can inform therapeutic strategies, including combination therapy approaches, and overcome the challenge of tumour heterogeneity.

Tracking MET de-addiction in lung cancer: A road towards the oncogenic target

The discovery of druggable oncogenic drivers (i.e. EGFR and ALK), along with the introduction of comprehensive tumor genotyping techniques into the daily clinical practice define non-small-cell lung cancer (NSCLC) asa group of heterogeneous diseases, requiring a context-personalized clinico-therapeutical approach. Among the most investigated biomarkers, the MET proto-oncogene has been extensively demonstrated to play a crucial role throughout the lung oncogenesis, unbalancing the proliferation/apoptosis signaling and influencing the epithelial-mesenchymal transition and the invasive phenotype. Nevertheless, although different mechanisms eliciting the aberrant MET-associated oncogenic stimulus have been detected in lung cancer (such as gene amplification, increased gene copy number, mutations and MET/HGF overexpression), to date no clinically impactful results have been achieved with anti-MET tyrosine kinase inhibitors and monoclonal antibodies in the context of an unselected or MET enriched population. Recently, MET exon 14 splicing abnormalities have been identified asa potential oncogenic target in lung cancer, able to drive the activity of MET inhibitors in molecularly selected patients. In this paper, the major advancement and drawbacks of MET history in lung cancer are reviewed, underlying the renewed scientific euphoria related to the recent identification of MET exon 14 splicing variants asan actionable oncogenic target.

Overcoming resistance to EGFR tyrosine kinase inhibitors in lung cancer, focusing on non-T790M mechanisms

INTRODUCTION

despite initial dramatic efficacy of EGFR tyrosine kinase inhibitors (TKIs) in EGFR-mutant lung cancer patients, emergence of acquired resistance is almost inevitable. The EGFR T790M secondary mutation that accounts for ~50% of resistance is now treatable with osimertinib. However, for the remaining 50% of patients who develop resistance mechanisms other than T790M mutation, cytotoxic chemotherapies are still the standard of care and novel treatment strategies are urgently needed. Areas covered: In this review, we discuss current experimental and clinical evidence to develop better treatment strategies to overcome or prevent acquired resistance to EGFR-TKIs in lung cancers, focusing on non-T790M mechanisms. Expert commentary: There are numerous non-T790M resistant mechanisms to EGFR-TKIs, and therefore, strategies that can be applied to many of these resistance mechanisms may be reasonable and useful in clinical practice. Although the combination of cytotoxic chemotherapy plus an EGFR-TKI has proved to be detrimental following front-line EGFR-TKI treatment failure, promising experimental and/or early clinical data have been reported for the combination of bevacizumab or anti-EGFR monoclonal antibody plus EGFR-TKIs. Upfront polytherapy, which co-targets potential resistance mechanisms or other important signaling for EGFR-mutant lung cancer cells, is also a promising strategy.

A phase I study of foretinib plus erlotinib in patients with previously treated advanced non-small cell lung cancer: Canadian cancer trials group IND.196

Purpose

MET and AXL mediate resistance to EGFR TKI in NSCLC. Foretinib, a MET/RON/AXL/TIE-2/VEGFR kinase inhibitor may overcome EGFR kinase resistance. This dose escalation study combined foretinib and erlotinib in advanced pretreated NSCLC patients.

Experimental Design

The primary endpoint was to define the RP2D of foretinib plus erlotinib as continuous oral daily dosing. Secondary objectives included safety, pharmacokinetics, response and potential biomarkers of response including EGFR, KRAS genotype, MET, AXL expression, and circulating HGF levels. Erlotinib (E100-150 mg) was commenced on day 1 cycle 1; if well tolerated, foretinib (F30-45 mg) was added on day 15 cycle 1, using standard 3+3 dose escalation.

Results

Of 31 patients enrolled in 3 dose levels, 6 were inevaluable for DLT and replaced. DLT occurred in 3/15 patients at DL2 (E150 mg, F30 mg): Gr3 pain, mucositis, fatigue and rash. Cycle 1 DLT was not seen at DL3 (E150 mg, F45 mg) but 27% experienced dose reduction/interruption. Adverse events in ≥20% included diarrhea, fatigue, anorexia, dry skin, rash and hypertension. No PK interaction was seen with the combination. RP2D was defined as erlotinib 150 mg daily x 14 days with foretinib 30 mg added on day 15 (continuous dosing in 28-day cycles). Responses were seen in 17.8% of response evaluable patients (5/28). In 18 samples, baseline MET expression uncontrolled for EGFR genotype appeared associated with response. AXL expression was associated with neither EGFR mutation nor response.

Conclusion

Combining foretinib and erlotinib demonstrated response in unselected advanced NSCLC but also incremental toxicity. Future development will require molecular patient selection.