NTRK Therapy among Different Types of Cancers, Review and Future Perspectives.

Neurotrophic tyrosine receptor kinase (NTRK) has been a remarkable therapeutic target for treating different malignancies, playing an essential role in oncogenic signaling pathways. Groundbreaking trials like NAVIGATE led to the approval of NTRK inhibitors by the Food and Drug Administration (FDA) to treat different malignancies, significantly impacting current oncology treatment. Accurate detection of NTRK gene fusion becomes very important for possible targeted therapy. Various methods to detect NTRK gene fusion have been applied widely based on sensitivity, specificity, and accessibility. The utility of different tests in clinical practice is discussed in this study by providing insights into their effectiveness in targeting patients who may benefit from therapy. Widespread use of NTRK inhibitors in different malignancies could remain limited due to resistance mechanisms that cause challenges to medication efficacy in addition to common side effects of the medications. This review provides a succinct overview of the application of NTRK inhibitors in various types of cancer by emphasizing the critical clinical significance of NTRK fusion gene detection. The discussion also provides a solid foundation for understanding the current challenges and potential changes for improving the efficacy of NTRK inhibitor therapy to treat different malignancies.

Larotrectinib efficacy and safety in adult patients with tropomyosin receptor kinase fusion sarcomas.

BACKGROUND: Larotrectinib, a first-in-class, highly selective tropomyosin receptor kinase (TRK) inhibitor, has demonstrated efficacy in adult and pediatric patients with various solid tumors harboring NTRK gene fusions. This subset analysis focuses on the efficacy and safety of larotrectinib in an expanded cohort of adult patients with TRK fusion sarcomas. METHODS: Patients (≥18 years old) with sarcomas harboring NTRK gene fusions were identified from three clinical trials. Patients received larotrectinib 100 mg orally twice daily. Response was investigator-assessed per RECIST v1.1. Data cutoff was July 20, 2021. RESULTS: At the data cutoff, 36 adult patients with TRK fusion sarcomas had initiated larotrectinib therapy: two (6%) patients had bone sarcomas, four (11%) had gastrointestinal stromal tumors, and 30 (83%) had soft tissue sarcomas. All patients were evaluable for response and demonstrated an objective response rate of 58% (95% confidence interval, 41-74). Patients responded well to larotrectinib regardless of number of prior lines of therapy. Adverse events (AEs) were mostly grade 1/2. Grade 3 treatment-emergent AEs (TEAEs) occurred in 15 (42%) patients. There were no grade 4 TEAEs. Two grade 5 TEAEs were reported, neither of which were considered related to larotrectinib. Four (11%) patients permanently discontinued treatment due to TEAEs. CONCLUSIONS: Larotrectinib demonstrated robust and durable responses, extended survival benefit, and a favorable safety profile in adult patients with TRK fusion sarcomas with longer follow-up. These results continue to demonstrate that testing for NTRK gene fusions should be incorporated into the clinical management of adult patients with various types of sarcomas. PLAIN LANGUAGE SUMMARY: Tropomyosin receptor kinase (TRK) fusion proteins result from translocations involving the NTRK gene and cause cancer in a range of tumor types. Larotrectinib is an agent that specifically targets TRK fusion proteins and is approved for the treatment of patients with TRK fusion cancer. This study looked at how well larotrectinib worked in adult patients with sarcomas caused by TRK fusion proteins. Over half of patients had a durable response to larotrectinib, with no unexpected side effects. These results show that larotrectinib is safe and effective in adult patients with TRK fusion sarcomas.

A Two-Step Diagnostic Approach for NTRK Gene Fusion Detection in Biliary Tract and Pancreatic Adenocarcinomas.

BACKGROUND: It is of interest to determine the incidence and molecular characteristics of NTRK gene fusions in patients with bilio-pancreatic cancers, because of possible treatment with TRK inhibitors for advanced tumors. The aim of the present study was to apply the guidelines for NTRK testing algorithm to a series of patients with bilio-pancreatic cancers. METHODS: Immunohistochemistry screening was applied on formalin-fixed paraffin-embedded archival blocks from surgical resections, biopsies, or cytological samples of biliary tract and pancreatic adenocarcinomas. The presence of at least a weak staining in rare tumor cells led to testing by 2 RNA-based NGS panels. RESULTS: For biliary tract tumors, 153 samples have been selected. A total of 140 samples were suitable to perform IHC, and 17 samples were IHC positive. RNA NGS testing of the 17 IHC-positive samples revealed a single NTRK3 gene fusion (ETV6(4)-NTRK3(14)) that was detected by both NGS panels. In this perihilar cholangiocarcinoma, IHC performed on a biopsy showed a weak focal cytoplasmic and nuclear staining. No other NTRK fusion was detected on the 16 other samples with both panels. Overall in the patients screened by IHC and confirmed by NGS, the percentage of NTRK fusions was 0.7%. For pancreatic cancers, 319 samples have been selected and 297 were suitable to perform IHC. Nineteen samples were IHC positive. No fusion was detected by NGS. CONCLUSION: NTRK gene fusions are rare in bilio-pancreatic cancers but testing is of high interest due to possible treatment with specific TRK inhibitors.

Design, synthesis, and biological evaluation of aminopyridine derivatives as novel tropomyosin receptor kinase inhibitors.

Tropomyosin receptor kinase (TRK) is a successful target for the treatment of various cancers caused by NTRK gene fusions. Herein, based on a rational drug design strategy, we designed and synthesized 35 aminopyrimidine derivatives that were shown to be TRKA inhibitors in the enzyme assay, among which compounds C3, C4, and C6 showed potent inhibitory activities against TRKA with IC50 values of 6.5, 5.0, and 7.0 nM, respectively. In vitro antiproliferative activity study showed that compound C3 significantly inhibited the proliferation of KM-12 cells but had weak inhibitory effect on MCF-7 cells and HUVEC cells. The preliminary druggability evaluation showed that compound C3 exhibited favorable liver microsomal and plasma stabilities and had weak or no inhibitory activity against cytochrome P450 isoforms at 10 µM. Compounds C3, C4, and C6 were also selected for ADME (absorption, distribution, metabolism, and elimination) properties prediction and molecular docking studies. Inhibition experiments showed that compound C3 was not selective for TRK subtypes. All results indicated that compound C3 was a useful candidate for the development of TRK inhibitors.

Inhibition of EGFR and MEK surmounts entrectinib resistance in a brain metastasis model of NTRK1-rearranged tumor cells.

Tropomyosin receptor kinase (TRK) inhibitors have demonstrated histology-agnostic efficacy in patients with neurotrophic receptor tyrosine kinase (NTRK) gene fusion. Although responses to TRK inhibitors can be dramatic and durable, duration of response may eventually be limited by acquired resistance via several mechanisms, including resistance mutations such as NTRK1-G595R. Repotrectinib is a second-generation TRK inhibitor, which is active against NTRK1-G595R. However, its efficacy against entrectinib-resistant tumors has not been fully elucidated. In the present study, we established entrectinib-resistant tumor cells (M3B) in a brain metastasis model inoculated with NTRK1-rearranged KM12SM cells and examined the sensitivity of M3B cells to repotrectinib. While M3B cells harbored the NTRK1-G595R mutation, they were unexpectedly resistant to repotrectinib. The resistance was due to extracellular signal-regulated kinase (ERK) reactivation partially mediated by epidermal growth factor receptor (EGFR) activation. We further demonstrate that the triplet combination of repotrectinib, EGFR inhibitor, and MEK inhibitor could sensitize M3B cells in vitro as well as in a brain metastasis model. These results indicate that resistant mutations, such as NTRK1-G595R, and alternative pathway activation, such as ERK activation, could simultaneously occur in entrectinib-resistant tumors, thereby causing resistance to second-generation inhibitor repotrectinib. These findings highlight the importance of intensive examinations to identify resistance mechanisms and application of the appropriate combination treatment to circumvent the resistance.

Investigating the natural history and prognostic nature of NTRK gene fusions in solid tumors.

BACKGROUND: Several 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. METHODS: A 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). RESULTS: Among 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. CONCLUSIONS: This 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.

Rationale and design of ON-TRK: a novel prospective non-interventional study in patients with TRK fusion cancer treated with larotrectinib.

BACKGROUND: Tropomyosin receptor kinase (TRK) fusion proteins resulting from neurotrophic tyrosine receptor kinase (NTRK) gene fusions are rare primary oncogenic drivers in a wide array of tumors. Larotrectinib is a first-in-class, highly selective, central nervous system-active TRK inhibitor approved by the US Food and Drug Administration (FDA), European Medicines Agency (EMA), and over 40 countries for the treatment of TRK fusion solid tumors in adult and pediatric patients. Due to the rarity of TRK fusion cancer, larotrectinib was granted accelerated approval based on a relatively small number of patients enrolled in three early phase trials. ON-TRK aims to evaluate the safety profile of larotrectinib in a broader population and over extended time periods. METHODS: ON-TRK is a prospective, non-interventional, open-label, multicenter, multi-cohort, post-approval study in adult and pediatric patients with locally advanced or metastatic TRK fusion cancer treated with larotrectinib that will describe the safety and effectiveness of larotrectinib in real-world practice conditions. Adult patients will be grouped by tumor type and followed for at least 2 years. Patients < 18 years old will be enrolled under a 'pediatric' cohort regardless of tumor type and will be followed for 5 years to evaluate the risk of potential long-term adverse effects of larotrectinib on their growth and development. The effectiveness of larotrectinib in the overall study population as well as in patient subgroups will also be evaluated. Procedures avoided in patients with infantile fibrosarcoma (e.g., amputation) and the number of patients who were able to undergo surgery with a curative intent (excluding amputation) because of the use of larotrectinib will be described. Larotrectinib treatment patterns in real-world practice, including dosing and duration of treatment, will be described. DISCUSSION: The FDA Accelerated Approval Program allows for earlier approval of and patient access to drugs that treat serious conditions and fill an unmet medical need. This study is designed to fulfill post-approval requirements set by the FDA as well as post-marketing requirements set forth by local regulatory bodies and is part of the risk management plan for the EMA. STUDY REGISTRATION: This study is registered at ClinicalTrials.gov ( NCT04142437 ). PROTOCOL VERSION: v2.5, 25 March 2021.

Testing methods to diagnose TRK fusion cancer - a plain language summary and patient perspective.

WHAT IS THIS SUMMARY ABOUT?: This is a plain language summary of a 2022 study published in Cancer Genetics. This study describes the different tests used to detect a rare type of cancer called TRK (tropomyosin receptor kinase) fusion cancer in people taking part in three clinical trials testing the medication larotrectinib. Larotrectinib targets TRK fusion proteins, abnormal proteins that result from abnormal NTRK (neurotrophic tyrosine receptor kinase) gene fusions. People who were shown to have solid tumors containing TRK fusion proteins were able to participate in clinical trials that evaluated larotrectinib. WHAT WERE THE RESULTS?: Different testing methods were used to identify participants with TRK fusion cancer. Which test was used depended on different factors such as how commonly NTRK gene fusions are found in a specific cancer type, and the cost and accessibility of the test. Participants with different types of cancer were included in the study, which allowed researchers to identify which TRK fusion proteins were found across various types of tumor. WHAT DO THE RESULTS MEAN?: The results of this study provide a guidance for healthcare professionals on the methods used for testing to identify patients that have TRK fusion cancer. By characterizing the types of testing done across cancer types, patients and their caregivers can gain an understanding of the importance of testing. This plain language summary also includes insights and perspectives from a person affected by TRK fusion cancer, and from patient advocates. Clinical Trial Registration: NCT02122913 (ClinicalTrials.gov) Clinical Trial Registration: NCT02637687 (ClinicalTrials.gov) Clinical Trial Registration: NCT02576431 (ClinicalTrials.gov).

NTRK-rearranged spindle cell neoplasm of the lower extremity: radiologic-pathologic correlation.

Neurotrophic tyrosine receptor kinase (NTRK)-rearranged spindle cell neoplasm is a recently characterized soft tissue tumor and has been classified as provisional by the World Health Organization. Detection of the genetic rearrangement is important because these tumors are amenable to targeted tyrosine kinase inhibitor therapy, which can play a key role in patients with unresectable or advanced disease. Although the spectrum of histopathology associated with this entity is broad, one notable feature is the infiltrative growth pattern, which is most reminiscent of lipofibromatosis-like neural tumor. Description of their diverse histologic attributes has aided recognition, but so far little attention has been paid to correlating the gross appearance and imaging features of these lesions. In this report, we describe the clinical, imaging, histopathological, and genetic features of a soft tissue NTRK-rearranged spindle cell neoplasm. Inclusion of this more recently identified entity into the imaging differential of tumors with intratumoral relatively hypovascular nodules and infiltrative margins is important because testing for NTRK rearrangement is not routinely performed.

Neurotrophin Trk Receptors: New Targets for Cancer Therapy.

In the last few years, exciting reports have emerged regarding the role of the two types of neurotrophin receptors, p75NTR and Trks, not only in neurons, where they were discovered, but also in non-neural cells and, especially, in numerous cancers, including breast, lung, colon-rectum, pancreas, prostate, glioblastoma, neuroblastoma, myeloma, and lymphoid tumors. Traditionally, p75NTR, activated by all neurotrophins and their precursors, is an inhibitor. In various cancers, however, activated p75NTR induces variable effects, from inhibition to stimulation of cell proliferation, dependent on their direct or coordinate/indirect mechanism(s) of action. TrkA, TrkB, and TrkC, activated by distinct neurotrophins, are high affinity stimulatory receptors. In cancers, activation of Trks, especially of TrkB, are stimulators of cell proliferation, aggressiveness, and metastases. In rare cancers, these processes are due not to receptor activation but to fusion or mutation of the encoding genes. A considerable panel of anti-Trk drugs, developed recently, has been investigated both in vitro and in living mice for their effects on cancer cells. Many such drugs protect from cancers by preventing cell proliferation and inducing apoptosis. At present, these drugs are under control by trials, to promote introduction in human therapy. Moreover, anti-Trk drugs have been employed also in combination with classical chemotherapeutic drugs. So far, studies in mice have been positive. The chemotherapeutic/anti-receptor combinations exhibited in fact increased potency and down-regulation of resistance, with no increase of side effects.

Larotrectinib in adult patients with solid tumours: a multi-centre, open-label, phase I dose-escalation study.

BACKGROUND: NTRK1, NTRK2 and NTRK3 gene fusions (NTRK gene fusions) occur in a range of adult cancers. Larotrectinib is a potent and highly selective ATP-competitive inhibitor of TRK kinases and has demonstrated activity in patients with tumours harbouring NTRK gene fusions. PATIENTS AND METHODS: This multi-centre, phase I dose escalation study enrolled adults with metastatic solid tumours, regardless of NTRK gene fusion status. Key inclusion criteria included evaluable and/or measurable disease, Eastern Cooperative Oncology Group performance status 0-2, and adequate organ function. Larotrectinib was administered orally once or twice daily, on a continuous 28-day schedule, in increasing dose levels according to a standard 3 + 3 dose escalation scheme. The primary end point was the safety of larotrectinib, including dose-limiting toxicity. RESULTS: Seventy patients (8 with tumours with NTRK gene fusions; 62 with tumours without a documented NTRK gene fusion) were enrolled to 6 dose cohorts. There were four dose-limiting toxicities; none led to study drug discontinuation. The maximum tolerated dose was not reached. Larotrectinib-related adverse events were predominantly grade 1; none were grade 4 or 5. The most common grade 3 larotrectinib-related adverse event was anaemia [4 (6%) of 70 patients]. A dose of 100 mg twice daily was recommended for phase II studies based on tolerability and antitumour activity. In patients with evaluable TRK fusion cancer, the objective response rate by independent review was 100% (eight of the eight patients). Eight (12%) of the 67 assessable patients overall had an objective response by investigator assessment. Median duration of response was not reached. Larotrectinib had limited activity in tumours with NTRK mutations or amplifications. Pharmacokinetic analysis showed exposure was generally proportional to administered dose. CONCLUSIONS: Larotrectinib was well tolerated, demonstrated activity in all patients with tumours harbouring NTRK gene fusions, and represents a new treatment option for such patients. CLINCALTRIALS.GOV NUMBER: NCT02122913.

TRK inhibitors in TRK fusion-positive cancers.

TRK fusions are oncogenic drivers of various adult and paediatric cancers. The first-generation TRK inhibitors, larotrectinib and entrectinib, were granted landmark, tumour-agnostic regulatory approvals for the treatment of these cancers in 2018 and 2019, respectively. Brisk and durable responses are achieved with these drugs in patients, including those with locally advanced or metastatic disease. In addition, intracranial activity has been observed with both agents in TRK fusion-positive solid tumours with brain metastases and primary brain tumours. While resistance to first-generation TRK inhibition can eventually occur, next-generation agents such as selitrectinib (BAY 2731954, LOXO-195) and repotrectinib were designed to address on-target resistance, which is mediated by emergent kinase domain mutations, such as those that result in substitutions at solvent front or gatekeeper residues. These next-generation drugs are currently available in the clinic and proof-of-concept responses have been reported. This underscores the utility of sequential TRK inhibitor use in select patients, a paradigm that parallels the use of targeted therapies in other oncogenic driver-positive cancers, such as ALK fusion-positive lung cancers. While TRK inhibitors have a favourable overall safety profile, select on-target adverse events, including weight gain, dizziness/ataxia and paraesthesias, are occasionally observed and should be monitored in the clinic. These side-effects are likely consequences of the inhibition of the TRK pathway that is involved in the development and maintenance of the nervous system.

TRK inhibitors in TRK fusion-positive cancers.

TRK fusions are oncogenic drivers of various adult and paediatric cancers. The first-generation TRK inhibitors, larotrectinib and entrectinib, were granted landmark, tumour-agnostic regulatory approvals for the treatment of these cancers in 2018 and 2019, respectively. Brisk and durable responses are achieved with these drugs in patients, including those with locally advanced or metastatic disease. In addition, intracranial activity has been observed with both agents in TRK fusion-positive solid tumours with brain metastases and primary brain tumours. While resistance to first-generation TRK inhibition can eventually occur, next-generation agents such as selitrectinib (BAY 2731954, LOXO-195) and repotrectinib were designed to address on-target resistance, which is mediated by emergent kinase domain mutations, such as those that result in substitutions at solvent front or gatekeeper residues. These next-generation drugs are currently available in the clinic and proof-of-concept responses have been reported. This underscores the utility of sequential TRK inhibitor use in select patients, a paradigm that parallels the use of targeted therapies in other oncogenic driver-positive cancers, such as ALK fusion-positive lung cancers. While TRK inhibitors have a favourable overall safety profile, select on-target adverse events, including weight gain, dizziness/ataxia and paraesthesias, are occasionally observed and should be monitored in the clinic. These side-effects are likely consequences of the inhibition of the TRK pathway that is involved in the development and maintenance of the nervous system.

Tropomyosin receptor kinase (TRK) biology and the role of NTRK gene fusions in cancer.

The tropomyosin receptor kinase (TRK) family of receptor tyrosine kinases are encoded by NTRK genes and have a role in the development and normal functioning of the nervous system. Since the discovery of an oncogenic NTRK gene fusion in colorectal cancer in 1986, over 80 different fusion partner genes have been identified in a wide array of adult and paediatric tumours, providing actionable targets for targeted therapy. This review describes the normal function and physiology of TRK receptors and the biology behind NTRK gene fusions and how they act as oncogenic drivers in cancer. Finally, an overview of the incidence and prevalence of NTRK gene fusions in various types of cancers is discussed.

Tumour response to TRK inhibition in a patient with pancreatic adenocarcinoma harbouring an NTRK gene fusion.

BACKGROUND: Although rare, NTRK gene fusions are known to be oncogenic drivers in pancreatic ductal adenocarcinoma (PDAC). We report the response of a metastatic CTRC-NTRK1 gene fusion-positive PDAC to targeted treatment with the oral tropomyosin receptor kinase (TRK) inhibitor larotrectinib and the eventual development of resistance to treatment. PATIENT, METHODS AND RESULTS: A 61-year-old woman presented with a 2.5-cm mass in the body of the pancreas and a 1.2-cm liver lesion on routine follow-up for endometrial cancer that was in complete remission. Liver biopsy confirmed a primary PDAC unrelated to the endometrial cancer. The patient was treated with gemcitabine, nab-paclitaxel and ADI-PEG 20 for 12 months until disease progression and toxicity emerged [best overall response (BOR): partial response (PR)]. The patient switched to a modified regimen of folinic acid, fluorouracil, irinotecan and oxaliplatin for 4 months until neuropathy occurred. Oxaliplatin was withheld until disease progression 6 months later (BOR: stable disease). Despite recommencing oxaliplatin, the disease continued to progress. At this time, somatic profiling of the liver lesion revealed a CTRC-NTRK1 gene fusion. Treatment with larotrectinib 100 mg twice daily was commenced with BOR of PR at 2 months. The patient progressed after 6 months and was re-biopsied. Treatment was switched to the investigational next-generation TRK inhibitor selitrectinib (BAY 2731954, LOXO-195) 100 mg twice daily. After 2 months, the disease progressed and dabrafenibtrametinib combination therapy was initiated due to existence of a BRAF-V600E mutation. However, the cancer continued to progress and the patient died 2 months later. CONCLUSIONS: Targeted TRK inhibition with larotrectinib in PDAC harbouring a CTRC-NTRK1 gene fusion is well tolerated and can improve quality of life for the patient. However, acquired resistance to therapy can emerge in some patients. Next-generation TRK inhibitors such as selitrectinib are currently in development to overcome this resistance (NCT02576431; NCT03215511).

Neurotrophic-tyrosine receptor kinase gene fusion in papillary thyroid cancer: A clinicogenomic biobank and record linkage study from Finland.

Selective tropomyosin receptor kinase (TRK) inhibitors are approved targeted therapies for patients with solid tumors harboring a neurotrophic tyrosine receptor kinase (NTRK) gene fusion. Country-specific estimates of NTRK gene fusion frequency, and knowledge on the characteristics of affected patients, are limited. We identified patients with histologically-confirmed papillary thyroid cancer (PTC) from Finland's Auria Biobank. TRK protein expression was determined by pan-TRK immunohistochemistry. Immuno-stained tumor samples were scored by a certified pathologist. Gene fusions and other co-occurring gene alterations were identified by next generation sequencing. Patient characteristics and vital status were determined from linked hospital electronic health records (EHRs). Patients were followed from 1 year before PTC diagnosis until death. 6/389 (1.5%) PTC patients had an NTRK gene fusion (all NTRK3); mean age 43.8 years (and none had comorbidities) at PTC diagnosis. Gene fusion partners were EML4 (n = 3), ETV6 (n = 2), and RBPMS (n = 1). Of 3/6 patients with complete EHRs, all received radioactive iodine ablation only and were alive at end of follow-up (median observation, 9.12 years). In conclusion, NTRK gene fusion is infrequent in patients with PTC. Linkage of biobank samples to EHRs is feasible in describing the characteristics and outcomes of patients with PTC and potentially other cancer types.

Discovery of novel indazole derivatives as second-generation TRK inhibitors.

NTRK gene fusion leads to the activation of downstream signaling pathways, which is a oncogenic driver in various cancers. NTRK fusion-positive cancers can be treated with the first-generation TRK inhibitors, larotrectinib and entrectinib. Unfortunately, the patients eventually face the dilemma of no drugs available as the emergence of certain resistance mutations. The development of efficient and broad-spectrum second-generation TRK inhibitors is still of great significance. Here, we analyzed the binding modes of compounds 6, 10 with TRKA protein, respectively, a series of novel indazole TRK inhibitors were designed and synthesized using molecular hybridization strategy. Among them, the optimal compound B31 showed strong antiproliferative activities against Km-12, Ba/F3-TRKAG595R, and Ba/F3-TRKAG667C cell lines with IC50 values of 0.3, 4.7, and 9.9 nM, respectively. And the inhibitory effect against TRKAG667C (IC50 = 9.9 nM) was better than that of selitrectinib (IC50 = 113.1 nM). Further, compound B31 exhibited moderate kinase selectivity and excellent plasma stability (t1/2 > 480 min). In vivo pharmacokinetic studies in Sprague-Dawley rats showed that B31 had acceptable pharmacokinetic properties.

NTRK gene fusion testing and management in lung cancer.

Neurotrophic tyrosine receptor kinase (NTRK) gene fusions are recurrent oncogenic drivers found in a variety of solid tumours, including lung cancer. Several tropomyosin receptor kinase (TRK) inhibitors have been developed to treat tumours with NTRK gene fusions. Larotrectinib and entrectinib are first-generation TRK inhibitors that have demonstrated efficacy in patients with TRK fusion lung cancers. Genomic testing is recommended for all patients with metastatic non-small cell lung cancer for optimal drug therapy selection. Multiple testing methods can be employed to identify NTRK gene fusions in the clinic and each has its own advantages and limitations. Among these assays, RNA-based next-generation sequencing (NGS) can be considered a gold standard for detecting NTRK gene fusions; however, several alternatives with minimally acceptable sensitivity and specificity are also available in areas where widespread access to NGS is unfeasible. This review highlights the importance of testing for NTRK gene fusions in lung cancer, ideally using the gold-standard method of RNA-based NGS, the various assays that are available, and treatment algorithms for patients.

The landscape of cancer-associated transcript fusions in adult brain tumors: a longitudinal assessment in 140 patients with cerebral gliomas and brain metastases.

Background: Oncogenic fusions of neurotrophic receptor tyrosine kinase NTRK1, NTRK2, or NTRK3 genes have been found in different types of solid tumors. The treatment of patients with TRK fusion cancer with a first-generation TRK inhibitor (such as larotrectinib or entrectinib) is associated with high response rates (>75%), regardless of tumor histology and presence of metastases. Due to the efficacy of TRK inhibitor therapy of larotrectinib and entrectinib, it is clinically important to identify patients accurately and efficiently with TRK fusion cancer. In this retrospective study, we provide unique data on the incidence of oncogenic NTRK gene fusions in patients with brain metastases (BM) and gliomas. Methods: 140 samples fixed and paraffin-embedded tissue (FFPE) of adult patients (59 of gliomas [17 of WHO grade II, 20 of WHO grade III and 22 glioblastomas] and 81 of brain metastasis (BM) of different primary tumors) are analyzed. Identification of NTRK gene fusions is performed using next-generation sequencing (NGS) technology using Focus RNA assay kit (Thermo Fisher Scientific). Results: We identified an ETV6 (5)::NTRK3 (15) fusion event using targeted next-generation sequencing (NGS) in one of 59 glioma patient with oligodendroglioma-grade II, IDH-mutated and 1p19q co-deleted at incidence of 1.69%. Five additional patients harboring TMPRSS (2)::ERG (4) were identified in pancreatic carcinoma brain metastasis (BM), prostatic carcinoma BM, endometrium BM and oligodendroglioma (grade II), IDH-mutated and 1p19q co-deleted. A FGFR3 (17)::TACC3 (11) fusion was identified in one carcinoma breast BM. Aberrant splicing to produce EGFR exons 2-7 skipping mRNA, and MET exon 14 skipping mRNA were identified in glioblastoma and pancreas carcinoma BM, respectively. Conclusions: This study provides data on the incidence of NTRK gene fusions in brain tumors, which could strongly support the relevance of innovative clinical trials with specific targeted therapies (larotrectinib, entrectinib) in this population of patients. FGFR3 (17)::TACC3 (11) rearrangement was detected in breast carcinoma BM with the possibility of using some specific targeted therapies and TMPRSS (2)::ERG (4) rearrangements occur in a subset of patients with, prostatic carcinoma BM, endometrium BM, and oligodendroglioma (grade II), IDH-mutated and 1p19q co-deleted, where there are yet no approved ERG-directed therapies.

Feasibility of two-step approach for screening NTRK fusion in two major subtypes of non-small cell lung cancer within a large cohort.

Our objective is to investigate a cost-effective approach to screen for NTRK fusion in the major subtypes of non-small cell lung cancer (NSCLC). Evaluate the concordance between immunohistochemistry (IHC) and next-generation sequencing (NGS), as well as between fluorescence in situ hybridization (FISH) and NGS, to detect any discrepancies in methodological consistency between lung adenocarcinoma (LADC) and lung squamous cell carcinoma (LSCC). Analyze the factors influencing IHC results. A cohort of 1654 patients with NSCLC underwent screening for NTRK fusion using whole slide IHC. The positive cases were analyzed by both FISH and NGS. Totally, 57 tested positive for pan-TRK, with positivity rates of 0.68% (10/1467) for LADC and 29.01% (47/162) for LSCC. FISH showed separate NTRK1 and NTRK3 rearrangements in two pan-TRK-positive LADCs, while all LSCCs tested negative. NGS confirmed functional NTRK fusion in two FISH-positive cases: one involving TPM3-NTRK1 and the other involving SQSTM1-NTRK3. A non-functional fusion of NTRK2-XRCC1 was detected in LSCC, while FISH was negative. According to our approach, the prevalence of NTRK fusion in NSCLC is 0.12%. The concordance rate between IHC and RNA-based NGS was 20% (2/10) in LADC and 0% (0/162) in LSCC. When the positive criteria increased over 50% of tumor cells showing strong staining, the concordance would be 100% (2/2). A concordance rate of 100% (2/2) was observed between FISH and RNA-based NGS in LADC. The expression of pan-TRK was significantly correlated with the tumor proportion score (TPS) of PD-L1 (p < 0.05) and transcript per million (TPM) values of NTRK2 (p < 0.05). We recommend using IHC with strict criteria to screen NTRK fusion in LADC rather than LSCC, confirmed by RNA-based NGS directly. When the NGS results are inconclusive, FISH validation is necessary.