Discovery of Tropomyosin Receptor Kinase Inhibitors as New Generation Anticancer Agents: A Review

BACKGROUND

The tropomyosin receptor kinases (TRKs) are crucial for many cellular functions, such as growth, motility, differentiation, and metabolism. Abnormal TRK signalling contributes to a variety of human disorders, most evidently cancer. Comprehensive genomic studies have found numerous changes in the genes that code for TRKs like MET, HER2/ErbB2, and EGFR, among many others. Precision medicine resistance, relapse occurring because of the protein point mutations, and the existence of multiple molecular feedback loops are significant therapeutic hurdles to the long-term effectiveness of TRK inhibitors as general therapeutic agents for the treatment of cancer.

OBJECTIVE

This review is carried out to highlight the role of tropomyosin receptor kinase in cancer and the function of TRK inhibitors in the intervention of cancer.

METHODS

Literature research has been accomplished using Google Scholar and databases like ScienceDirect, WOS, PubMed, SciFinder, and Scopus.

RESULTS

In this review, we provide an overview of the main molecular and functional properties of TRKs and their inhibitors. It also discusses how these advancements have affected the development and use of novel treatments for malignancies and other conditions caused by activated TRKs. Several therapeutic strategies, including the discovery and development of small-molecule TRK inhibitors belonging to various chemical classes and their activity, as well as selectivity towards the receptors, have been discussed in detail.

CONCLUSION

This review will help the researchers gain a fundamental understanding of TRKs, how this protein family works, and the ways to create chemical moieties, such as TRK inhibitors, which can serve as tailored therapies for cancer.

Diagnosis and Management of Tropomyosin Receptor Kinase Fusion-Positive Thyroid Carcinomas: A Review

Importance

Thyroid epithelial malignant neoplasms include differentiated thyroid carcinomas (papillary, follicular, and oncocytic), follicular-derived high-grade thyroid carcinomas, and anaplastic and medullary thyroid carcinomas, with additional rarer subtypes. The discovery of neurotrophic tyrosine receptor kinase (NTRK) gene fusions has fostered developments in precision oncology, with the approval of tropomyosin receptor kinase inhibitors (larotrectinib and entrectinib) for patients with solid tumors, including advanced thyroid carcinomas, harboring NTRK gene fusions.

Observations

The relative rarity and diagnostic complexity of NTRK gene fusion events in thyroid carcinoma present several challenges for clinicians, including variable access to robust methodologies for comprehensive NTRK fusion testing and poorly defined algorithms of when to test for such molecular alterations. To address these issues in thyroid carcinoma, 3 consensus meetings of expert oncologists and pathologists were convened to discuss diagnostic challenges and propose a rational diagnostic algorithm. Per the proposed diagnostic algorithm, NTRK gene fusion testing should be considered as part of the initial workup for patients with unresectable, advanced, or high-risk disease as well as following the development of radioiodine-refractory or metastatic disease; testing by DNA or RNA next-generation sequencing is recommended. Detecting the presence of NTRK gene fusions is important to identify patients eligible to receive tropomyosin receptor kinase inhibitor therapy.

Conclusions and Relevance

This review provides practical guidance for optimal integration of gene fusion testing, including NTRK gene fusion testing, to inform the clinical management in patients with thyroid carcinoma.

Neurotrophic tropomyosin receptor kinase (NTRK) fusion positive tumors: a historical cohort analysis

BACKGROUND

NTRK gene fusions have been identified in various tumors; some requiring aggressive therapy and sometimes new TRK inhibitors (TRKi). We aimed to describe a national, unselected, retrospective, multicenter cohort.

RESEARCH DESIGN AND METHODS

Patients were identified through the French sarcoma diagnostic laboratory at Institut Curie through samples analyzed by RT-qPCR or whole-transcriptome sequencing.

RESULTS

From 2001 to 2019, 65 NTRK fusion tumors were identified within 2120 analyses (3.1%): 58 by RNA sequencing (including 20 after RT-qPCR analysis) and 7 exclusively by RT-qPCR. Of the 61 patients identified, 37 patients had infantile soft tissue or kidney fibrosarcomas (IFS), 15 other mesenchymal (Other-MT) and nine central nervous system (CNS) tumors. They encompassed 14 different tumor types with variable behaviors. Overall, 53 patients had surgery (3 mutilating), 38 chemotherapy (20 alkylating agents/anthracycline), 11 radiotherapy, two 'observation strategy' and 13 received TRKi. After a median follow-up of 61.0 months [range, 2.5-226.0], 10 patients died. Five-year overall survival is, respectively, 91.9% [95%CI, 83.5-100.0], 61.1% [95%CI, 34.2-100.0] and 64.8% [95%CI, 39.3-100.0] for IFS, Other-MT, and CNS groups.

CONCLUSIONS

NTRK-fusion positive tumors are rare but detection is improved through RNA sequencing. TRKi could be considered at diagnosis for CNS NTRK-fusion positive tumors, some IFS, and Other-MT.

TRIAL REGISTRATION

Not adapted.

NTRK fusions in thyroid cancer: Pathology and clinical aspects

Thyroid cancer is the most common endocrine cancer. Neurotrophic tyrosine receptor kinase (NTRK) fusions are oncogenic drivers in multiple solid tumors, including thyroid cancer. NTRK fusion thyroid cancer has unique pathological features such as mixed structure, multiple nodes, lymph node metastasis, and a background of chronic lymphocytic thyroiditis. Currently, RNA-based next-generation sequencing is the gold standard for the detection of NTRK fusions. Tropomyosin receptor kinase inhibitors have shown promising efficacy in patients with NTRK fusion-positive thyroid cancer. Efforts to overcome acquired drug resistance are the focus of research concerning next-generation TRK inhibitors. However, there are no authoritative recommendations or standardized procedures for the diagnosis and treatment of NTRK fusions in thyroid cancer. This review discusses current research progress regarding NTRK fusion-positive thyroid cancer, summarizes the clinicopathological features of the disease, and outlines the current statuses of NTRK fusion detection and targeted therapeutic agents.

Nefarious NTRK oncogenic fusions in pediatric sarcomas: Too many to Trk

Neurotrophic Tyrosine Receptor Kinase (NTRK) genes undergo chromosomal translocations to create novel open reading frames coding for oncogenic fusion proteins; the N-terminal portion, donated by various partner genes, becomes fused to the tyrosine kinase domain of either NTRK1, NTRK2, or NTRK3. NTRK fusion proteins have been identified as driver oncogenes in a wide variety of tumors over the past three decades, including Pediatric Gliomas, Papillary Thyroid Carcinoma, Spitzoid Neoplasms, Glioblastoma, and additional tumors. Importantly, NTRK fusions function as drivers of pediatric sarcomas, accounting for approximately 15% of childhood cancers including Infantile Fibrosarcoma (IFS), a subset of pediatric soft tissue sarcoma (STS). While tyrosine kinase inhibitors (TKIs), such as larotrectinib and entrectinib, have demonstrated profound results against NTRK fusion-positive cancers, acquired resistance to these TKIs has resulted in the formation of gatekeeper, solvent-front, and compound mutations. We present a comprehensive compilation of oncogenic fusions involving NTRKs focusing specifically on pediatric STS, examining their biological signaling pathways and mechanisms of activation. The importance of an obligatory dimerization or multimerization domain, invariably donated by the N-terminal fusion partner, is discussed using characteristic fusions that occur in pediatric sarcomas. In addition, examples are presented of oncogenic fusion proteins in which the N-terminal partners may contribute additional biological activities beyond an oligomerization domain. Lastly, therapeutic approaches to the treatment of pediatric sarcoma will be presented, using first generation and second-generation agents such as selitrectinib and repotrectinib.

TrkAd5: A novel therapeutic agent for treatment of inflammatory pain and asthma

Elevated levels of nerve growth factor have been linked to the onset and persistence of many pain-related disorders and asthma. Described here are the design, expression, refolding, and purification of a monomeric (nonstrand-swapped) form of the binding domain of the nerve growth factor receptor, designated TrkAd5. We have shown that TrkAd5 produced recombinantly binds nerve growth factor with picomolar affinity. TrkAd5 has been characterized using a variety of biophysical and biochemical assays and is shown here to be stable in both plasma and urine. The palliative effects of TrkAd5 are demonstrated in animal models of inflammatory pain and allergic asthma. We conclude that TrkAd5 will prove effective in ameliorating both acute and chronic conditions where nerve growth factor acts as a mediator and suggest a role for its application in vivo as a novel therapeutic.

DECREASE IN BLADDER OVERACTIVITY WITH REN1820 IN RATS WITH CYCLOPHOSPHAMIDE INDUCED CYSTITIS

PURPOSE

Studies suggest that nerve growth factor (NGF) contributes to bladder overactivity stemming from bladder inflammation. Studies were performed to determine the NGF dependence of cyclophosphamide (CYP) induced changes in bladder function using the recombinant NGF sequestering protein REN1820.

MATERIALS AND METHODS

Urodynamic testing and behavioral observations were made in female rats treated with CYP (4 or 48 hours) and REN1820 or vehicle.

RESULTS

Rats examined 4 or 48 hours after CYP treatment plus REN1820 showed significantly fewer nonvoiding contractions with smaller amplitude (p </=0.01). Rats examined 48 hours after CYP treatment plus REN1820 showed decreased voiding frequency (p </=0.01). No changes in filling, threshold or micturition pressure were observed with REN1820 treatment. Rats treated with CYP plus REN1820 showed greater mobility and normal resting postures compared with rats treated with CYP plus vehicle.

CONCLUSIONS

These studies demonstrate that the use of the NGF sequestering protein REN1820 in rats with CYP induced cystitis decreases bladder overactivity. This is characterized by 1) a decrease in the number and amplitude of nonvoiding contractions and 2) decreased voiding frequency. Rats treated with REN1820 showed greater mobility and normal resting postures, which may reflect improved overall health or well-being. REN1820 may prove to be a novel therapeutic in individuals with the chronic inflammatory bladder syndrome interstitial cystitis.