Sructural rearrangements of NTRK genes: characteristics, methods of detection and targeted therapy for cancer

Background. The first-generation trk inhibitors, larotrectinib and entrectinib, were approved by the u.s. Food and drug administration (Fda) for the treatment of advanced solid tumors harboring NTRK gene fusions in November 2018 and in august 2019, respectively. The purpose of the study was to present upto-date data on the structure and functions of ntrk genes, the frequency of occurrence of rearrangements with their participation, the consequences of their occurrence at the cellular level, methods of detecting such rearrangements, as well as targeted drugs used in the presence of chimeric NTRK genes. Material and methods. A systemic literature search was conducted in pubmed ncbi, Web of science, scopus databases. Results. The products of NTRK genes are receptors for neurotrophins, and their high expression is normally observed only in a narrow range of tissue types. Intrachromosomal or interchromosomal rearrangements lead to a significant increase in the level of expression of the chimeric gene regulated by the strong promoter of the partner gene. The high transcriptional activity of such a gene, along with the constant activation of the kinase activity of the protein product, leads to the activation of metabolic pathways responsible for cell escape from apoptosis and disruption of the regulation of the cell cycle. The occurrence of chimeric NTRK genes varies between different types of tumors, with the highest (up to 90 %) in rare cancers (secretory carcinoma of the breast, secretory carcinoma of the salivary glands, congenital mesoblastic nephroma, children’s fibrosarcoma). Larotrectinib and entrectinib are highly effective targeted drugs in suppressing the growth of a tumor carrying NTRK rearrangements, regardless of the type of tumor. In this regard, the introduction of new high-precision methods for the detection of chimeric NTRK genes, as well as the study of the mechanisms of the development of resistance with the assumption of ways to overcome it, seems relevant. Conclusion. Rearrangements of NTRK genes are quite common in various types of oncology and are an effective target for modern targeted drugs.

BIOM-16. NTRK (NEUROTROPHIC TYROSINE RECEPTOR KINASE) FUSIONS IN GLIOMA PATIENTS: A PROMISING MOLECULAR TARGET?

BACKGROUND NTRK gene fusions are rare in gliomas (less than 2%). The use of TRK inhibitors in NTRK-fused solid tumors has generated significant clinical interest. It is likely that the unmet need for effective therapies in glioma will lead to routine testing for NTRK fusions. METHODS We performed a retrospective review of 22 patients with malignant gliomas accrued between 2007 and 2021. We collected tumor samples from those patients and NTRK fusions were tested using either immunohistochemistry or FISH or NGS. We then evaluated their association with clinical characteristics, histology and other markers (IDH1/2 mutation, MGMT methylation, BRAF mutation, EGFR expression, ATRX expression, TERT mutation). RESULTS Median age at diagnosis was 50 years. NTRK1 translocation was detected in 3 out of 22 patient tumors, while NTRK1 duplication was present in 1 patient (probably related to a translocation, but not proven). All NTRK1 translocations were not found in glioblastomas and their median survival was 15.8 months. On the other hand, median survival of gliomas without NTRK translocations was 11 months. In one NTRK1-translocated patient a TRK inhibitor (entrectinib) was used (for a few days), but we cannot evaluate its efficacy as the patient deteriorated and died. As far as the other biomarkers are concerned, 2 out of 3 NTRK1-translocated gliomas were MGMT methylated. CONCLUSION NTRK fusions are rare in gliomas, as confirmed in our small sample analysis. Although adult NTRK-fused gliomas are considered to predominantly involve high-grade histology, in our study all patients had initially lower grade gliomas. NTRK alterations can be detected by different laboratory assays, but each of these approaches has specific advantages and limitations and more data are needed in order to identify the best method. For glioblastomas, NTRK fusions and TRK inhibitors are potentially a new targeted therapeutic strategy but more data are needed.

Suboptimal clinician awareness of appropriate NTRK fusion testing and TRK inhibitor use in solid tumors.

229 Background: Since late 2018, 2 TRK inhibitors—larotrectinib and entrectinib—have been approved by the EMA and FDA for treating patients with advanced solid tumors harboring an NTRK fusion and progressive disease or no therapeutic alternatives. It is recommended that testing for NTRK fusions occur as early as possible after a diagnosis of advanced disease in patients with solid tumors to inform potential use of TRK inhibitors. Methods: Between April 2018 and April 2021, we conducted multiple live and online educational activities for oncology healthcare professionals (HCPs) on NTRK fusion testing and/or TRK inhibitor treatment for varied solid tumors. Each activity included polling questions designed to assess HCP knowledge and practice patterns. In this analysis, we assessed HCP responses to these questions to evaluate awareness of expert recommendations on NTRK fusion testing and the selection of TRK inhibitor therapy for appropriate patients. Results: In 6 live and online activities with data from April 2018 to April 2021, 29% of HCPs (n = 844) indicated that they ordered molecular profiling to test for NTRK fusions in all solid tumors in their current practice. Of note, low rates of testing were reported in TRK inhibitor/ NTRK testing-focused activities throughout this time period, with no significant increase over time. In assessing different patient cases across 8 activities where experts recommended TRK inhibitor therapy as optimal, many HCPs did not select a TRK inhibitor, with considerable variance by tumor type (Table). *For all cases, experts selected larotrectinib and/or entrectinib as optimal treatment. †HCP respondents. GBM, glioblastoma; GI, gastrointestinal; MSI-H, microsatellite instability-high; PD, progressive disease; PTC, papillary thyroid cancer.Conclusions: The rate of broad testing for NTRK fusions across patients with solid tumors remains low, and many HCPs lack awareness of when to consider a TRK inhibitor. Educational activities designed to address these deficiencies would be of clear benefit to HCPs treating patients with advanced solid tumors. A detailed analysis of HCP trends will be presented.[Table: see text]

Új célzott terápiás lehetőség az onkológiában: tropomiozin receptor-tirozin-kináz gátlók

Összefoglaló. A molekuláris diagnosztikai módszerek folyamatos fejlődésének köszönhetően egyre több onkogén genetikai eltérést azonosítanak. A neurotrofikus tropomiozin receptor-tirozin-kináz (NTRK-) génfúziók fontos precíziós onkológiai célpontok, melyek mindhárom NTRK-génben előfordulhatnak, onkogén-hajtóerőként viselkednek. A génfúziók különböző molekuláris diagnosztikai módszerekkel azonosíthatók, melyek közül a legpontosabb, legköltségesebb és legidőigényesebb meghatározást az újgenerációs szekvenálási technika jelenti. A tropomiozin receptor-tirozin-kináz (TRK-) fúziós fehérjék szelektív gátlása személyre szabott onkológiai kezelési lehetőséget jelent a tumor típusától, lokalizációjától és a beteg életkorától függetlenül. Az első generációs TRK-gátlók gyors, hatékony és tartós daganatellenes hatást biztosítanak kimutatott NTRK-fúzió-pozitív daganatok esetén, alacsony mellékhatásprofil mellett. Az első generációs TRK-gátlók mellett jelentkező ’on target’ rezisztenciát a második generációs TRK-gátlók oldják fel. Szekvenciális tirozin-kináz-inhibitor-kezeléssel tartós betegségmentes túlélés érhető el. Orv Hetil. 2021; 162(34): 1362–1369. Summary. Due to the continuous development of molecular diagnostic methods, more and more oncogenic genetic abnormalities are being identified. Neurotrophic tropomyosin receptor tyrosine kinase (NTRK) gene fusions are important precision oncology targets that can occur in all three NTRK genes and act as oncogenic drivers. Gene fusions can be identified by a variety of molecular diagnostic technologies, of which next-generation sequencing is the most accurate, costly and time-consuming determination. Selective inhibition of tropomyosin receptor tyrosine kinase (TRK) fusion proteins represents a personalized oncology treatment option regardless of tumour type, localization and patient age. First-generation TRK inhibitors provide rapid, efffective and long-lasting antitumor activity in NTRK fusion-positive tumors with a low side-effect profile. On target resistance to first-generation TRK inhibitors is resolved by second-generation TRK inhibitors. Durable disease-free survival can be achieved with sequential tyrosine kinase inhibitor therapies. Orv Hetil. 2021; 162(34): 1362–1369.

TRK Inhibitors: Tissue-Agnostic Anti-Cancer Drugs

Recently, two tropomycin receptor kinase (Trk) inhibitors, larotrectinib and entrectinib, have been approved for Trk fusion-positive cancer patients. Clinical trials for larotrectinib and entrectinib were performed with patients selected based on the presence of Trk fusion, regardless of cancer type. This unique approach, called tissue-agnostic development, expedited the process of Trk inhibitor development. In the present review, the development processes of larotrectinib and entrectinib have been described, along with discussion on other Trk inhibitors currently in clinical trials. The on-target effects of Trk inhibitors in Trk signaling exhibit adverse effects on the central nervous system, such as withdrawal pain, weight gain, and dizziness. A next generation sequencing-based method has been approved for companion diagnostics of larotrectinib, which can detect various types of Trk fusions in tumor samples. With the adoption of the tissue-agnostic approach, the development of Trk inhibitors has been accelerated.

Investigating the Natural History and Prognostic Nature of NTRK Gene Fusions in Solid Tumors

BackgroundSeveral TRK inhibitors have demonstrated clinical efficacy in patients with solid tumors harboring NTRK gene fusions. However, the natural history and prognostic implications of NTRK fusions in solid tumors remain unknown.MethodsA cohort of 77 MD Anderson Cancer Center patients (MDACC) with NTRK gene fusions was identified and retrospectively compared to a second cohort from the Cancer Genome Atlas (TCGA) database. Due to paucity of events in early stage cancers and lack of TCGA data in rare tumors, 25 randomly selected MDACC patients were matched to 122 TCGA patients without NTRK gene fusion. Next we assessed the associations between NTRK gene fusion and overall (OS) and progression-free survivals (PFS).ResultsAmong the 77 MDACC patients with NTRK gene fusions, 18 NTRK fusion partners were identified. There were insufficient OS events for analysis in the matched cohort. PFS was not significantly different (p=0.49) between the NTRK-fusion positive MDACC patients (median PFS 786 weeks, 95% CI 317-NE) and the NTRK-fusion negative TCGA patients (median PFS NE). The adjusted hazard ratio comparing TCGA patients to MDACC patients was HR=0.72 (95% CI: 0.23-2.33), which trended towards a reduced rate of progression or death experienced by TCGA patients.ConclusionsThis study did not identify statistically significant associations between NTRK fusion and PFS. Nonsignificant trends estimated increases in the risk of progression or death events for patients with NTRK fusions when compared to matched controls. Our findings help illuminate the influence of NTRK fusions on the natural history of a variety of solid tumors.