A tyrosine kinase inhibitor (TKI) is a pharmaceutical drug that inhibits tyrosine kinases. Tyrosine kinases are enzymes responsible for the activation of many proteins by signal transduction cascades. The proteins are activated by adding a phosphate group to the protein (phosphorylation), a step that TKIs inhibit. TKIs are typically used as anticancer drugs. For example, they have substantially improved outcomes in chronic myelogenous leukemia. They have also been used to treat other diseases, such as idiopathic pulmonary fibrosis.
They are also called tyrphostins, the short name for "tyrosine phosphorylation inhibitor", originally coined in a 1988 publication, [1] which was the first description of compounds inhibiting the catalytic activity of the epidermal growth factor receptor (EGFR).
The 1988 study was the first demonstration of a systematic search and discovery of small-molecular-weight inhibitors of tyrosine phosphorylation, which do not inhibit protein kinases that phosphorylate serine or threonine residues and can discriminate between the kinase domains of the EGFR and that of the insulin receptor. It was further shown that in spite of the conservation of the tyrosine-kinase domains one can design and synthesize tyrphostins that discriminate between even closely related protein tyrosine kinases such as EGFR and its close relative HER2. [2] [3]
Numerous TKIs aiming at various tyrosine kinases have been generated by the originators of these compounds and proven to be effective anti-tumor agents and anti-leukemic agents. [4] [5] Based on this work imatinib was developed against chronic myelogenous leukemia (CML) [6] and later gefitinib and erlotinib aiming at the EGF receptor. Dasatinib is a Src tyrosine kinase inhibitor that is effective both as a senolytic and as therapy for CML. [7]
Sunitinib, an inhibitor of the receptors for FGF, PDGF and VEGF is also based on early studies on TKIs aiming at VEGF receptors. [8]
Adavosertib is a Wee1 kinase inhibitor that is undergoing numerous clinical trials in the treatment of refractory solid tumors. [9] However, toxicities such as myelosuppression, diarrhea, and supraventricular tachyarrhythmia have arisen while attempting to determine the toxicity and effectiveness of the drug. [10]
Lapatinib, FDA-approved for treatment in conjunction with chemotherapy or hormone therapy, is also currently undergoing clinical trials in the treatment of HER2-overexpressing breast cancers as it is suggested intermittent high-dose therapy might have better efficacy with manageable toxicity than the standard continuous dosing. A Phase I clinical trial found responses and dramatic responses to this line of treatment, with the most common toxicity being diarrhea. [11]
Imatinib, sunitinib, sorafenib, and pazopanib have been studied in the treatment of aggressive fibromatosis (desmoid tumor). [12] [13]
TKIs operate by four different mechanisms: they can compete with adenosine triphosphate (ATP), the phosphorylating entity, the substrate or both or can act in an allosteric fashion, namely bind to a site outside the active site, affecting its activity by a conformational change. [14] Recently TKIs have been shown to deprive tyrosine kinases of access to the Cdc37-Hsp90 molecular chaperone system on which they depend for their cellular stability, leading to their ubiquitylation and degradation. [15] Signal transduction therapy can also be used for non-cancer proliferative diseases and for inflammatory conditions. [16] An example is nintedanib for the treatment of idiopathic pulmonary fibrosis. [17]
A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to the tyrosine residues of specific proteins inside a cell. It functions as an "on" or "off" switch in many cellular functions.
Gefitinib, sold under the brand name Iressa, is a medication used for certain breast, lung and other cancers. Gefitinib is an EGFR inhibitor, like erlotinib, which interrupts signaling through the epidermal growth factor receptor (EGFR) in target cells. Therefore, it is only effective in cancers with mutated and overactive EGFR, but resistances to gefitinib can arise through other mutations. It is marketed by AstraZeneca and Teva.
The epidermal growth factor receptor is a transmembrane protein that is a receptor for members of the epidermal growth factor family of extracellular protein ligands.
Quinazoline is an organic compound with the formula C8H6N2. It is an aromatic heterocycle with a bicyclic structure consisting of two fused six-membered aromatic rings, a benzene ring and a pyrimidine ring. It is a light yellow crystalline solid that is soluble in water. Also known as 1,3-diazanaphthalene, quinazoline received its name from being an aza derivative of quinoline. Though the parent quinazoline molecule is rarely mentioned by itself in technical literature, substituted derivatives have been synthesized for medicinal purposes such as antimalarial and anticancer agents. Quinazoline is a planar molecule. It is isomeric with the other diazanaphthalenes of the benzodiazine subgroup: cinnoline, quinoxaline, and phthalazine. Over 200 biologically active quinazoline and quinoline alkaloids are identified.
Erlotinib, sold under the brand name Tarceva among others, is a medication used to treat non-small cell lung cancer (NSCLC) and pancreatic cancer. Specifically it is used for NSCLC with mutations in the epidermal growth factor receptor (EGFR) — either an exon 19 deletion (del19) or exon 21 (L858R) substitution mutation — which has spread to other parts of the body. It is taken by mouth.
Receptor tyrosine-protein kinase erbB-2 is a protein that normally resides in the membranes of cells and is encoded by the ERBB2 gene. ERBB is abbreviated from erythroblastic oncogene B, a gene originally isolated from the avian genome. The human protein is also frequently referred to as HER2 or CD340.
Targeted therapy or molecularly targeted therapy is one of the major modalities of medical treatment (pharmacotherapy) for cancer, others being hormonal therapy and cytotoxic chemotherapy. As a form of molecular medicine, targeted therapy blocks the growth of cancer cells by interfering with specific targeted molecules needed for carcinogenesis and tumor growth, rather than by simply interfering with all rapidly dividing cells. Because most agents for targeted therapy are biopharmaceuticals, the term biologic therapy is sometimes synonymous with targeted therapy when used in the context of cancer therapy. However, the modalities can be combined; antibody-drug conjugates combine biologic and cytotoxic mechanisms into one targeted therapy.
Lapatinib (INN), used in the form of lapatinib ditosylate (USAN) is an orally active drug for breast cancer and other solid tumours. It is a dual tyrosine kinase inhibitor which interrupts the HER2/neu and epidermal growth factor receptor (EGFR) pathways. It is used in combination therapy for HER2-positive breast cancer. It is used for the treatment of patients with advanced or metastatic breast cancer whose tumors overexpress HER2 (ErbB2).
The MAPK/ERK pathway is a chain of proteins in the cell that communicates a signal from a receptor on the surface of the cell to the DNA in the nucleus of the cell.
Receptor tyrosine kinases (RTKs) are the high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones. Of the 90 unique tyrosine kinase genes identified in the human genome, 58 encode receptor tyrosine kinase proteins. Receptor tyrosine kinases have been shown not only to be key regulators of normal cellular processes but also to have a critical role in the development and progression of many types of cancer. Mutations in receptor tyrosine kinases lead to activation of a series of signalling cascades which have numerous effects on protein expression. The receptors are generally activated by dimerization and substrate presentation. Receptor tyrosine kinases are part of the larger family of protein tyrosine kinases, encompassing the receptor tyrosine kinase proteins which contain a transmembrane domain, as well as the non-receptor tyrosine kinases which do not possess transmembrane domains.
Matuzumab is a humanized monoclonal antibody for the treatment of cancer. It binds to the epidermal growth factor receptor (EGFR) with high affinity. The mouse monoclonal antibody (mAb425) from which matuzumab was developed at the Wistar Institute in Philadelphia, Pennsylvania
Zalutumumab is a fully human IgG1 monoclonal antibody (mAb) directed towards the epidermal growth factor receptor (EGFR). It is a product developed by Genmab in Utrecht, the Netherlands. Specifically, zalutumumab is designed for the treatment of squamous cell carcinoma of the head and neck (SCCHN), a type of cancer.
The ErbB family of proteins contains four receptor tyrosine kinases, structurally related to the epidermal growth factor receptor (EGFR), its first discovered member. In humans, the family includes Her1, Her2 (ErbB2), Her3 (ErbB3), and Her4 (ErbB4). The gene symbol, ErbB, is derived from the name of a viral oncogene to which these receptors are homologous: erythroblastic leukemia viral oncogene. Insufficient ErbB signaling in humans is associated with the development of neurodegenerative diseases, such as multiple sclerosis and Alzheimer's disease, while excessive ErbB signaling is associated with the development of a wide variety of types of solid tumor.
Alexander Levitzki is an Israeli biochemist who is a professor of biochemistry at the Alexander Silberman Institute of Life Sciences, the Hebrew University of Jerusalem.
Receptor tyrosine-protein kinase erbB-3, also known as HER3, is a membrane bound protein that in humans is encoded by the ERBB3 gene.
Afatinib, sold under the brand name Gilotrif among others, is a medication which is used to treat non-small cell lung carcinoma (NSCLC). It belongs to the tyrosine kinase inhibitor family of medications. It is taken by mouth.
A431 cells are a model human cell line used in biomedical research.
Neratinib (INN), sold under the brand name Nerlynx, is a tyrosine kinase inhibitor anti-cancer medication used for the treatment of breast cancer.
ALK inhibitors are anti-cancer drugs that act on tumours with variations of anaplastic lymphoma kinase (ALK) such as an EML4-ALK translocation. They fall under the category of tyrosine kinase inhibitors, which work by inhibiting proteins involved in the abnormal growth of tumour cells. All the current approved ALK inhibitors function by binding to the ATP pocket of the abnormal ALK protein, blocking its access to energy and deactivating it. A majority of ALK-rearranged NSCLC harbour the EML4-ALK fusion, although as of 2020, over 92 fusion partners have been discovered in ALK+ NSCLC. For each fusion partner, there can be several fusion variants depending on the position the two genes were fused at, and this may have implications on the response of the tumour and prognosis of the patient.
Osimertinib, sold under the brand name Tagrisso, is a medication used to treat non-small-cell lung carcinomas with specific mutations. It is a third-generation epidermal growth factor receptor tyrosine kinase inhibitor.