The role of small molecule Flt3 receptor protein-tyrosine kinase inhibitors in the treatment of Flt3-positive acute myelogenous leukemias

doi:10.1016/j.phrs.2020.104725

Pharmacological Research

Volume 155, May 2020, 104725

https://doi.org/10.1016/j.phrs.2020.104725 Get rights and content

Abstract

Flt3 is expressed by early myeloid and lymphoid progenitor cells and it regulates the proliferation and differentiation of hematopoietic cells. Flt3 is activated by the Flt3 ligand, the monomeric form of which is a polypeptide of about 200 amino acid residues. Both membrane-associated and soluble Flt3 ligands, which are a product of the same gene, function as noncovalent dimers. FLT3 mutations occur in about one-third of newly diagnosed acute myelogenous leukemia (AML) patients. This disease is a malignancy of hematopoietic progenitor cells with a variable clinical course; the incidence of this disorder is more than twice that of patients with chronic myelogenous leukemias (20,000 vs. 8500 new patients per year, respectively, in the United States). FLT3 internal tandem duplication (ITD) results from the head-to-tail duplication of from one to more than 100 amino acids within the juxtamembrane domain and such duplication occurs in about 20–25 % of patients with acute myelogenous leukemias. FLT3 tyrosine kinase (FLT3 TK) mutations, usually within the activation segment, occur in 5–10 % of these patients. The mainstay for the care of acute myelogenous leukemias include daunorubicin or idarubicin and cytarabine. Older patients who are not candidates for such traditional therapy are usually given 5-azacitidine, decitabine, or clofarabine. The addition of orally effective small molecule Flt3 inhibitors to these therapies may prolong event-free and overall survival, a subject of ongoing clinical studies. Midostaurin is US FDA-approved in combination with standard cytarabine and daunorubicin for first-line induction chemotherapy and in combination with cytarabine for second-line consolidation chemotherapy in the treatment of acute myelogenous leukemias with FLT3-postive mutations. Moreover, gilteritinib is a Flt3 multikinase inhibitor that is also FDA approved for the care of adult patients with relapsed or refractory acute myelogenous leukemias with FLT3 mutations. Quizartinib is a Flt3 multikinase inhibitor that was approved by the Ministry of Health, Labor and Welfare (MHLW) of Japan for the treatment of adult patients with relapsed/refractory Flt3-positive acute myelogenous leukemias. Gilteritinib and quizartinib bind to Flt3 with the inactive DFG-D_out structure and are classified as type II inhibitors. Furthermore, ponatinib is a multikinase inhibitor that is approved as therapy for Philadelphia chromosome-positive acute lymphoblastic and chronic myelogenous leukemias; it is used off label for the treatment of patients with acute myelogenous leukemias. Moreover, sorafenib is FDA-approved for the treatment of hepatocellular, renal cell, and differentiated thyroid cancers and it is used off label as maintenance therapy following allogeneic hematopoietic stem cell transplantation in the treatment of acute myelogenous leukemias. Other drugs that are in clinical trials for the treatment of this disorder include sunitinib, crenolanib, FF10101, and lestaurtinib. Unlike chronic myelogenous leukemias, which result solely from the formation of the BCR-Abl chimeric protein kinase, acute myelogenous leukemias result from multi-factorial causes and are prone to be resistant to both cytotoxic and targeted therapies. Consequently, there is a pressing need for better understanding the etiologies of acute myelogenous leukemias and for the development of more effective therapies.

Graphical abstract

Section snippets

Flt3 and Flt3L

Protein kinases are catalysts that play a pivotal role in nearly every facet of cell biology and biochemistry [1,2]. These enzymes generate signaling modules that regulate cell cycle progression, proliferation, programmed cell death (apoptosis), cytoskeletal function, motility, differentiation, development, transcription, and translation. Owing to the numerous actions of protein kinases, it is essential that they are carefully regulated because abnormal activity can lead to cancer as well as

Primary, secondary, and tertiary structures of the Flt3 catalytic domain

The catalytic domain of Kit consists of 334 amino acid residues. The average protein kinase domain contains about 275 residues and the larger size of Flt3 is due to the inclusion of a kinase insert domain (KID) of 70 residues [19]. Based upon the amino acid sequences of about five dozen protein-tyrosine and protein-serine/threonine kinases, Hanks and Hunter partitioned protein kinases into 12 domains (I-VIA, VIB-XI) [20]. Domain I of Flt3 contains a glycine-rich loop (GRL) with a GxGxΦG

Inhibitor classification

Dar and Shokat divided protein kinase antagonists into three groups, which they labeled as types I, II, and III [56]. They classified type I inhibitors as those that bind within and around the adenine pocket of a catalytically active enzyme. Moreover, they classified type II inhibitors as those that bind to an inactive DFG-D_out protein kinase and they classified type III inhibitors as agents that bind to an allosteric site that does not overlap with the adenine-binding pocket. Subsequently,

Drug binding pockets

Liao [55] and van Linden et al. [62] divided the region between the small and large lobes of protein kinases into the front cleft (front pocket), the gate area, and the back cleft. A general overview illustrating these sites and various sub-pockets is provided in Fig. 5 and Table 3. The gate area and back cleft make up the back pocket or HPII (hydrophobic pocket II). The front cleft contains the final three residues of the β1-strand, the entire glycine-rich loop, the initial four residues of

Drug-enzyme interactions

Gilteritinib is a pyrazinecarboxamide derivative (Fig. 6A) and a Flt3 multikinase inhibitor that is US FDA approved for the treatment of adult patients with relapsed or refractory AML with a FLT3 mutation as detected by the FDA-approved LeukoStrat CDx mutation assay [67]. Besides Flt3, the drug inhibits the ALK, LTK, ROS1, and RET receptor protein-tyrosine kinases with IC₅₀ values in the low nanomolar range [68]. The X-ray crystal structure of gilteritinib bound to Flt3 demonstrates that a

Lipinski’s rule of five (Ro5)

Medicinal chemists and pharmacologists have searched for beneficial drug-like chemical properties that result in medicines with oral therapeutic effectiveness. Lipinski’s “rule of five” is an experimental and computational methodology to estimate membrane permeability, solubility, and effectiveness in the drug-development setting [95]. It is a rule of thumb that evaluates drug-likeness and determines whether a compound with particular pharmacological activities has physical and chemical

Epilogue

Although the mode of binding or pose of each medicinal with its protein kinase target is unique, it is useful to generalize drug-enzyme interactions and employ them in the drug development and discovery process. We divided protein kinase inhibitors into seven possible types (I–VI and I½) based upon the nature of their drug-enzyme complexes [52]. The complexity of inhibitor taxonomy increases because some medications can bind to different conformations of their protein kinase targets. For

Declaration of Competing Interest

The author is unaware of any affiliations, memberships, or financial holdings that might be perceived as affecting the objectivity of this review.

Acknowledgments

The colored figures in this paper were checked to ensure that their perception was accurately conveyed to colorblind readers [111]. The author thanks Laura M. Roskoski for providing editorial and bibliographic assistance. I also thank Josie Rudnicki and Jasper Martinsek help in preparing the figures and Pasha Brezina and W.S. Sheppard for their help in structural analyses.

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Properties of FDA-approved small molecule protein kinase inhibitors: A 2024 update
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Owing to the dysregulation of protein kinase activity in many diseases including cancer, this enzyme family has become one of the most important drug targets in the 21st century. There are 80 FDA-approved therapeutic agents that target about two dozen different protein kinases and seven of these drugs were approved in 2023. Of the approved drugs, thirteen target protein-serine/threonine protein kinases, four are directed against dual specificity protein kinases (MEK1/2), twenty block nonreceptor protein-tyrosine kinases, and 43 inhibit receptor protein-tyrosine kinases. The data indicate that 69 of these drugs are prescribed for the treatment of neoplasms. Six drugs (abrocitinib, baricitinib, deucravacitinib, ritlecitinib, tofacitinib, upadacitinib) are used for the treatment of inflammatory diseases (atopic dermatitis, rheumatoid arthritis, psoriasis, alopecia areata, and ulcerative colitis). Of the 80 approved drugs, nearly two dozen are used in the treatment of multiple diseases. The following seven drugs received FDA approval in 2023: capivasertib (HER2-positive breast cancer), fruquintinib (metastatic colorectal cancer), momelotinib (myelofibrosis), pirtobrutinib (mantle cell lymphoma, chronic lymphocytic leukemia, small lymphocytic lymphoma), quizartinib (Flt3-mutant acute myelogenous leukemia), repotrectinib (ROS1-positive lung cancer), and ritlecitinib (alopecia areata). All of the FDA-approved drugs are orally effective with the exception of netarsudil, temsirolimus, and trilaciclib. This review summarizes the physicochemical properties of all 80 FDA-approved small molecule protein kinase inhibitors including the molecular weight, number of hydrogen bond donors/acceptors, polar surface area, potency, solubility, lipophilic efficiency, and ligand efficiency.
Cost in the United States of FDA-approved small molecule protein kinase inhibitors used in the treatment of neoplastic and non-neoplastic diseases
2024, Pharmacological Research
Because genetic alterations including mutations, overexpression, translocations, and dysregulation of protein kinases are involved in the pathogenesis of many illnesses, this enzyme family is the target of many drug discovery programs worldwide. The FDA has approved 80 small molecule protein kinase inhibitors with 77 drugs orally bioavailable. The data indicate that 69 of these medicinals are approved for the management of neoplasms including solid tumors such as breast and lung cancer as well as non-solid tumors such as leukemia. Moreover, the remaining 11 drugs target non-neoplastic diseases including psoriasis, rheumatoid arthritis, and ulcerative colitis. The cost of drugs was obtained from www.pharmacychecker.com using the FDA label to determine the dosage and number of tablets required per day. This methodology excludes any private or governmental insurance coverage, which would cover the entire cost or more likely a fraction of the stated price. The average monthly cost for the treatment of neoplastic diseases was $17,900 with a price of $44,000 for futibatinib (used to treat cholangiocarcinomas with FGFR2 fusions) and minimum of $5100 for binimetinib (melanoma). The average monthly cost for the treatment of non-neoplastic diseases was $6800 with a maximum of $17,000 for belumosudil (graft vs. host disease) and a minimum of $200 for netarsudil eye drops (glaucoma). There is a negative correlation of the cost of the drugs and the incidence of the targeted disease. Many of these agents are or were designated as orphan drugs meaning that there are fewer than 200,000 potential patients in the United States.
PLM-101 is a novel and potent FLT3/RET inhibitor with less adverse effects in the treatment of acute myeloid leukemia
2023, Biomedicine and Pharmacotherapy
Acute myeloid leukemia (AML) is a prevalent form of leukemia in adults. As its survival rate is low, there is an urgent need for new therapeutic options. In AML, FMS-like tyrosine kinase 3 (FLT3) mutations are common and have negative outcomes. However, current FLT3-targeting agents, Midostaurin and Gilteritinib, face two significant issues, specifically the emergence of acquired resistance and drug-related adverse events leading to treatment failure. Rearranged during transfection (RET), meanwhile, is a proto-oncogene linked to various types of cancer, but its role in AML has been limited. A previous study showed that activation of RET kinase enhances FLT3 protein stability, leading to the promotion of AML cell proliferation. However, no drugs are currently available that target both FLT3 and RET. This study introduces PLM-101, a new therapeutic option derived from the traditional Chinese medicine indigo naturalis with potent in vitro and in vivo anti-leukemic activities. PLM-101 potently inhibits FLT3 kinase and induces its autophagic degradation via RET inhibition, providing a superior mechanism to that of FLT3 single-targeting agents. Single- and repeated-dose toxicity tests conducted in the present study showed no significant drug-related adverse effects. This study is the first to present a new FLT3/RET dual-targeting inhibitor, PLM-101, that shows potent anti-leukemic activity and fewer adverse effects. PLM-101, therefore, should be considered for use as a potential therapeutic agent for AML.
Deucravacitinib is an allosteric TYK2 protein kinase inhibitor FDA-approved for the treatment of psoriasis
2023, Pharmacological Research
Psoriasis is a heterogeneous, inflammatory, autoimmune skin disease that affects up to 2% of the world’s population. There are many treatment modalities including topical medicines, ultraviolet light therapy, monoclonal antibodies, and several oral medications. Cytokines play a central role in the pathogenesis of this disorder including TNF-α, (tumor necrosis factor-α) IL-17A (interleukin-17A), IL-17F, IL-22, and IL-23. Cytokine signaling involves transduction mediated by the JAK-STAT pathway. There are four JAKS (JAK1/2/3 and TYK2) and six STATS (signal transducer and activators of transcription). Janus kinases contain an inactive JH2 domain that is aminoterminal to the active JH1 domain. Under basal conditions, the JH2 domain inhibits the activity of the JH1 domain. Deucravacitinib is an orally effective N-trideuteromethyl-pyridazine derivative that targets and stabilizes the TYK2 JH2 domain and thereby blocks TYK2 JH1 activity. Seven other JAK inhibitors, which target the JAK family JH1 domain, are prescribed for the treatment of neoplastic and other inflammatory diseases. The use of deuterium in the trimethylamide decreases the rate of demethylation and slows the production of a metabolite that is active against a variety of targets in addition to TYK2. A second unique aspect in the development of deucravacitinib is the targeting of a pseudokinase domain. Deucravacitinib is rather specific for TYK2 and its toxic effects are much less than those of the other FDA-approved JAK inhibitors. The successful development of deucravacitinib may stimulate the development of additional pseudokinase ligands for the JAK family and for other kinase families as well.
MARK3 kinase: Regulation and physiologic roles
2023, Cellular Signalling
Citation Excerpt :
Thus, N-Phenylpyrimidin-2-amine is technically a part of the human exposome. Several clinical drug structures, such as osimertinib [87] and gilteritinib [88], include the N-phenylpyrimidin-2-amine fragment. Meanwhile, the N-phenylpyrimidin-2-amine fragment has been widely used as a building block in the design of anticancer agents that contain a pyrimidine nitrogen capable of binding to the ATP-binding pocket [89,90].
Microtubule affinity-regulating kinase 3 (MARK3), a member of the MARK family, regulates several essential pathways, including the cell cycle, ciliated cell differentiation, and osteoclast differentiation. It is important to understand the control of their activities as MARK3 contains an N-terminal serine/threonine kinase domain, ubiquitin-associated domain, and C-terminal kinase-associated domain, which perform multiple regulatory functions. These functions include post-translational modification (e.g., phosphorylation) and interaction with scaffolding and other proteins. Differences in the amino acid sequence and domain position result in different three-dimensional protein structures and affect the function of MARK3, which distinguish it from the other MARK family members. Recent data indicate a potential role of MARK3 in several pathological conditions, including congenital blepharophimosis syndrome, osteoporosis, and tumorigenesis. The present review focuses on the physiological and pathological role of MARK3, its regulation, and recent developments in the small molecule inhibitors of the MARK3 signalling cascade.
Properties of FDA-approved small molecule protein kinase inhibitors: A 2023 update
2023, Pharmacological Research
Citation Excerpt :
The protein kinase spine and shell residues perform an important role in determining the structure and activity of these enzymes; one cannot overemphasize their importance in supporting the activity of this enzyme superfamily as well as their participation in their interactions with small molecule protein kinase antagonists. For an examination of the properties of the spine and shell residues and their interactions with low molecular weight inhibitors of important members of the protein kinase superfamily, see the following articles: Refs. [33–35] for the ALK pleotrophin and midkine receptor protein-tyrosine kinase, Refs. [16,36–38] for the EGFR family of protein-tyrosine kinases, Ref. [39] for the PDGFRα/β protein-tyrosine kinases, Ref. [40] for the fibroblast growth factor receptor family of protein-tyrosine kinases, Ref. [41] for the Kit stem cell receptor protein-tyrosine kinase, Ref. [42] for the RET glial-cell derived receptor protein-tyrosine kinase, Ref. [43] for the VEGFR1/2/3 protein-tyrosine kinases, Ref. [44] for the ROS1 orphan receptor protein-tyrosine kinase, Ref. [45] for the Flt3 receptor protein-tyrosine kinase, Refs. [21,46] for the BCR-Abl nonreceptor protein tyrosine kinases, Ref. [47,48] for the Janus nonreceptor protein-tyrosine kinase, Refs. [16,49] for the Bruton nonreceptor protein-tyrosine kinase, Refs. [50,51] for the Src nonreceptor protein-tyrosine kinase, Refs. [52,53] for the MEK1/2 dual specificity protein kinases, Refs. [20,54] for the cyclin-dependent protein-serine/threonine kinase family, Refs. [55,56] for the ERK1/2 protein-serine/threonine kinases, Refs. [57,58] for the RAF protein-serine/threonine kinases, and Ref. [9] for PI 3-kinase, a member of the atypical protein kinase group. The catalytic spines of protein kinases consist of two residues from the small lobe and six residues from the large lobe.
Owing to the dysregulation of protein kinase activity in many diseases including cancer, this enzyme family has become one of the most important drug targets in the 21st century. There are 72 FDA-approved therapeutic agents that target about two dozen different protein kinases and three of these drugs were approved in 2022. Of the approved drugs, twelve target protein-serine/threonine protein kinases, four are directed against dual specificity protein kinases (MEK1/2), sixteen block nonreceptor protein-tyrosine kinases, and 40 target receptor protein-tyrosine kinases. The data indicate that 62 of these drugs are prescribed for the treatment of neoplasms (57 against solid tumors including breast, lung, and colon, ten against nonsolid tumors such as leukemia, and four against both solid and nonsolid tumors: acalabrutinib, ibrutinib, imatinib, and midostaurin). Four drugs (abrocitinib, baricitinib, tofacitinib, upadacitinib) are used for the treatment of inflammatory diseases (atopic dermatitis, psoriatic arthritis, rheumatoid arthritis, Crohn disease, and ulcerative colitis). Of the 72 approved drugs, eighteen are used in the treatment of multiple diseases. The following three drugs received FDA approval in 2022 for the treatment of these specified diseases: abrocitinib (atopic dermatitis), futibatinib (cholangiocarcinomas), pacritinib (myelofibrosis). All of the FDA-approved drugs are orally effective with the exception of netarsudil, temsirolimus, and trilaciclib. This review summarizes the physicochemical properties of all 72 FDA-approved small molecule protein kinase inhibitors including lipophilic efficiency and ligand efficiency.

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Invited ReviewThe role of small molecule Flt3 receptor protein-tyrosine kinase inhibitors in the treatment of Flt3-positive acute myelogenous leukemias

Abstract

Graphical abstract

Section snippets

Flt3 and Flt3L

Primary, secondary, and tertiary structures of the Flt3 catalytic domain

Inhibitor classification

Drug binding pockets

Drug-enzyme interactions

Lipinski’s rule of five (Ro5)

Epilogue

Declaration of Competing Interest

Acknowledgments

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Invited Review
The role of small molecule Flt3 receptor protein-tyrosine kinase inhibitors in the treatment of Flt3-positive acute myelogenous leukemias