Crenolanib besylate (CP-868,596-26 or AR-868,596-26, 4-piperidinamine, 1- -[5-[(3-Methyl-3-oxetanyl)_methoxy1H-benzimidazol-1-yl.html" ;"title="-[(3-Methyl-3-oxetanyl)_methoxy.html" ;"title="-[5-[(3-Methyl-3-oxetanyl) methoxy">-[5-[(3-Methyl-3-oxetanyl) methoxy1H-benzimidazol-1-yl">-[(3-Methyl-3-oxetanyl)_methoxy.html" ;"title="-[5-[(3-Methyl-3-oxetanyl) methoxy">-[5-[(3-Methyl-3-oxetanyl) methoxy1H-benzimidazol-1-yl 8-quinolinyl]-, monobenzenesulfonate) is an investigational inhibitor being developed by AROG Pharmaceuticals, LLC. The compound is currently being evaluated for safety and efficacy in clinical trials for various types of cancer, including

acute myeloid leukemia Acute myeloid leukemia (AML) is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal cells that build up in the bone marrow and blood and interfere with normal blood cell production. Symptoms may inclu ...

(AML),

gastrointestinal stromal tumor Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. GISTs arise in the smooth muscle pacemaker interstitial cell of Cajal, or similar cells. They are defined as tumors whose behavior ...

(GIST), and

glioma A glioma is a type of tumor that starts in the glial cells of the brain or the spine. Gliomas comprise about 30 percent of all brain tumors and central nervous system tumours, and 80 percent of all malignant brain tumours. Signs and symptoms ...

. Crenolanib is an orally bioavailable benzamidazole that selectively and potently inhibits signaling of

wild-type The wild type (WT) is the phenotype of the typical form of a species as it occurs in nature. Originally, the wild type was conceptualized as a product of the standard "normal" allele at a locus, in contrast to that produced by a non-standard, "m ...

and mutant isoforms of class III receptor tyrosine kinases (RTK)

FLT3 Cluster of differentiation antigen 135 (CD135) also known as fms like tyrosine kinase 3 (FLT-3), receptor-type tyrosine-protein kinase FLT3, or fetal liver kinase-2 (Flk2) is a protein that in humans is encoded by the ''FLT3'' gene. FLT3 is a cyto ...

(FMS-like Tyrosine Kinase 3),

PDGFR Platelet-derived growth factor receptors (PDGF-R) are cell surface tyrosine kinase receptors for members of the platelet-derived growth factor (PDGF) family. PDGF subunits -A and -B are important factors regulating cell proliferation, cellu ...

α (Platelet-Derived Growth Factor Receptor), and PDGFR β. Unlike most RTK inhibitors, crenolanib is a type I mutant-specific inhibitor that preferentially binds to

phosphorylated In chemistry, phosphorylation is the attachment of a phosphate group to a molecule or an ion. This process and its inverse, dephosphorylation, are common in biology and could be driven by natural selection. Text was copied from this source, wh ...

active kinases with the ‘DFG in’ conformation motif.

Background

Type III

Receptor tyrosine kinase 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 kin ...

, including

, PDGFRα and PDGFRβ, have been directly implicated in the

pathogenesis Pathogenesis is the process by which a disease or disorder develops. It can include factors which contribute not only to the onset of the disease or disorder, but also to its progression and maintenance. The word comes from Greek πάθος ''pat ...

epithelial Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercell ...

mesenchymal Mesenchyme () is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. The interactions between mesenchyme and epithelium help to form nearly every ...

, and

hematological malignancies Tumors of the hematopoietic and lymphoid tissues (American English) or tumours of the haematopoietic and lymphoid tissues (British English) are tumors that affect the blood, bone marrow, lymph, and lymphatic system. Because these tissues are al ...

. Mutations of

comprise one of the most frequently identified types of genetic alterations in acute myeloid leukemia. Approximately one-third of AML patients present with a mutation in this gene. The majority of these mutations result in constitutive activation of downstream signaling pathways and aberrant cell growth. Mutations in FLT3 have also been reported in acute lymphoblastic leukemia (ALL) and

myelodysplastic syndrome A myelodysplastic syndrome (MDS) is one of a group of cancers in which immature blood cells in the bone marrow do not mature, and as a result, do not develop into healthy blood cells. Early on, no symptoms typically are seen. Later, symptoms may ...

(MDS). Activating mutations in

PDGFRA PDGFRA, i.e. platelet-derived growth factor receptor A, also termed PDGFRα, i.e. platelet-derived growth factor receptor α, or CD140a i.e. Cluster of Differentiation 140a, is a receptor located on the surface of a wide range of cell types. This re ...

have been detected in 5-12% of

Gastrointestinal stromal tumor Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract. GISTs arise in the smooth muscle pacemaker interstitial cell of Cajal, or similar cells. They are defined as tumors whose behavior ...

. Fusion of

has been found to be responsible for hematological malignances like

hypereosinophilic syndrome Hypereosinophilic syndrome is a disease characterized by a persistently elevated eosinophil count (≥ 1500 eosinophils/mm³) in the blood for at least six months without any recognizable cause, with involvement of either the heart, nervous sys ...

. The amplification of

chromosome 4 Chromosome 4 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 4 spans more than 186 million base pairs (the building material of DNA) and represents between 6 and 6.5 percent of the t ...

q12, the site of the

gene, has been identified in 13-29% of adult

gliomas A glioma is a type of tumor that starts in the glial cells of the brain or the spine. Gliomas comprise about 30 percent of all brain tumors and central nervous system tumours, and 80 percent of all malignant brain tumours. Signs and symptoms ...

and in 29% to 36% of diffuse intrinsic pontine gliomas (

DIPG Diffuse midline glioma (DMG), previously called Diffuse Intrinsic Pontine Glioma (DIPG) is a fatal tumour that arises in the brainstem; most commonly in the pons or thalamus. DMG is believed to be caused by genetic mutations that cause epigenetic ...

), a subset of high-grade gliomas (HGG) in pediatric patients. Activation of

PDGFRB Platelet-derived growth factor receptor beta is a protein that in humans is encoded by the ''PDGFRB'' gene. Mutations in PDGFRB are mainly associated with the clonal eosinophilia class of malignancies. Gene The ''PDGFRB'' gene is located on h ...

, a third member of the type III RTK family, has been implicated in the development of

chronic myelomonocytic leukemia Chronic myelomonocytic leukemia (CMML) is a type of leukemia, which are cancers of the blood-forming cells of the bone marrow. In adults, blood cells are formed in the bone marrow, by a process that is known as haematopoiesis. In CMML, there are i ...

due to the fusion of

with the TEL gene. Furthermore,

PDGFB Platelet-derived growth factor subunit B is a protein that in humans is encoded by the ''PDGFB'' gene. Function The protein encoded by this gene is a member of the platelet-derived growth factor family. The four members of this family are mito ...

translocation to the COL1A1 gene locus has been identified to be responsible for

dermatofibrosarcoma protuberans Dermatofibrosarcoma protuberans (DFSP) is a rare locally aggressive malignant cutaneous soft-tissue sarcoma. DFSP develops in the connective tissue cells in the middle layer of the skin (dermis). Estimates of the overall occurrence of DFSP in the ...

(DFSP). In cancer cells,

promotes tumor development and migration via proto-oncogenic downstream mediators like

AKT Protein kinase B (PKB), also known as Akt, is the collective name of a set of three serine/threonine-specific protein kinases that play key roles in multiple cellular processes such as glucose metabolism, apoptosis, cell proliferation, tran ...

and MEK. In stromal

fibroblasts A fibroblast is a type of biological cell that synthesizes the extracellular matrix and collagen, produces the structural framework ( stroma) for animal tissues, and plays a critical role in wound healing. Fibroblasts are the most common cells ...

, PDGFRα activation leads to local tissue invasion, production and secretion of

VEGF Vascular endothelial growth factor (VEGF, ), originally known as vascular permeability factor (VPF), is a signal protein produced by many cells that stimulates the formation of blood vessels. To be specific, VEGF is a sub-family of growth factors ...

, and elevated intratumoral interstitial pressure. In stromal

pericytes Pericytes (previously known as Rouget cells) are multi-functional mural cells of the microcirculation that wrap around the endothelial cells that line the capillaries throughout the body. Pericytes are embedded in the basement membrane of blood c ...

, PDGFRβ activation mediates vascular stability. Thus, either FLT3 or PDGF/

pathway is the primary driver of

oncogenesis Carcinogenesis, also called oncogenesis or tumorigenesis, is the formation of a cancer, whereby normal cells are transformed into cancer cells. The process is characterized by changes at the cellular, genetic, and epigenetic levels and abno ...

in the above malignancies and can be targeted by crenolanib therapy.

Mechanism

FLT3 Cluster of differentiation antigen 135 (CD135) also known as fms like tyrosine kinase 3 (FLT-3), receptor-type tyrosine-protein kinase FLT3, or fetal liver kinase-2 (Flk2) is a protein that in humans is encoded by the ''FLT3'' gene. FLT3 is a cyto ...
: wild-type and mutant

Crenolanib inhibits both wild type

and its constitutively active mutations. In vitro studies have shown that crenolanib has low ''K''_d for the

enzyme with constitutively activating internal tandem duplication (ITD) mutations and

tyrosine kinase 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. Tyrosine kinases belong to a larger cla ...

domain (TKD) mutations, D835H and D835Y, as compared to wild type. Crenolanib tightly binds to

-ITD,

-D835H and

-D835Y with ''K''_d of 0.74 nM, 0.4 nM, and 0.18 nM, respectively. Crenolanib inhibits the phosphorylation of the

-ITD receptor in transfected TF-1 cells and the

-D835Y TKD mutation in transfected Ba/F3 cells at nanomolar

IC50 The half maximal inhibitory concentration (IC50) is a measure of the potency of a substance in inhibiting a specific biological or biochemical function. IC50 is a quantitative measure that indicates how much of a particular inhibitory substance ...

concentrations of 1.3 nM and 8.8 nM, respectively. Immunoblot experiments performed in the Molm14

-ITD positive cell line show that crenolanib inhibits downstream signaling of

at a concentration of 10 nM.

MTT assay The MTT assay is a colorimetric assay for assessing cell metabolic activity. NAD(P)H-dependent cellular oxidoreductase enzymes may, under defined conditions, reflect the number of viable cells present. These enzymes are capable of reducing the t ...

measurements of crenolanib cytotoxicity evaluated in the

-ITD expressing cell lines Molm14 and MV411, showed that crenolanib is toxic at

concentrations of 7 nM and 8 nM, respectively.

PDGFRα: wild-type and mutant

Crenolanib has been shown to inhibit PDGFRα with an

of 0.4 ng/mL in porcine aortic epithelial cell lines. In Chinese hamster ovary (CHO) cells expressing PDGFRα, crenolanib inhibited the phosphorylation of wild type PDGFRα at an

of 10 nM. Additionally, crenolanib completely blocked PDGFRα phosphorylation and downstream

signaling at a concentration between 0.1 and 1 uM in Ink4a/Arf-/- mouse

astrocytes Astrocytes (from Ancient Greek , , "star" + , , "cavity", "cell"), also known collectively as astroglia, are characteristic star-shaped glial cells in the brain and spinal cord. They perform many functions, including biochemical control of endo ...

transfected to stably co-express both human PDGFRα and PDGF AA. The

lung cancer Lung cancer, also known as lung carcinoma (since about 98–99% of all lung cancers are carcinomas), is a malignant lung tumor characterized by uncontrolled cell growth in tissues of the lung. Lung carcinomas derive from transformed, malign ...

cell line H1703, which is reported to have amplification of both

(4q12) and PDGFC (4q32) genes on chromosome 4, and also overexpress PDGFRα, was sensitive to crenolanib with an

of ~80 nM. In CHO cells expressing an activating exon 18 (D842V) PDGFRα mutation, crenolanib was effective at an

of 6nM and IC90 of 25nM. In addition, crenolanib also inhibited phosphorylation of the double mutants PDGFRα (V561D + D842V and T674I + D842V).

PDGFRβ: wild-type

Crenolanib has been shown to inhibit PDGFRβ with an

of 0.8 ng/mL in porcine aortic epithelial cell lines. Crenolanib inhibits the ability of recombinant PDGFRβ to phosphorylate a synthetic tyrosine substrate ( poly-glutamic acid-tyrosine), with an

of 0.4 ng/mL. Evaluation of the antitumor activity of crenolanib in a genetically engineered BSG DIPG mouse model showed that it is highly selective for PDGFRβ with an

of 10 nM when measured by BrdU assay and 1.25 uM by

C-Kit: wild-type and mutant

Crenolanib has been shown to have

and Kd values of 67 nM and 78 nM, respectively, for wild type

c-KIT Proto-oncogene c-KIT is the gene encoding the receptor tyrosine kinase protein known as tyrosine-protein kinase KIT, CD117 (cluster of differentiation 117) or mast/stem cell growth factor receptor (SCFR). Multiple transcript variants encoding dif ...

in in vitro assays. Similar assays show that crenolanib inhibits

activating mutations D816H and D816V with

concentrations of 5.4 and 2.5 nM, respectively. Human bone marrow

progenitor cell A progenitor cell is a biological cell that can differentiate into a specific cell type. Stem cells and progenitor cells have this ability in common. However, stem cells are less specified than progenitor cells. Progenitor cells can only differ ...

growth assays showed that crenolanib has modest effects on

GM-CSF Granulocyte-macrophage colony-stimulating factor (GM-CSF), also known as colony-stimulating factor 2 (CSF2), is a monomeric glycoprotein secreted by macrophages, T cells, mast cells, natural killer cells, endothelial cells and fibroblasts tha ...

and BFUE driven colony formation at the

concentration of 20 nM.

Clinical

Phase I single-agent and Phase Ib combination studies have investigated the clinical pharmacology of crenolanib in patients with cancer. Pharmacokinetic and safety studies of Crenolanib administered alone or in combination with

docetaxel Docetaxel (DTX or DXL), sold under the brand name Taxotere among others, is a chemotherapy medication used to treat a number of types of cancer. This includes breast cancer, head and neck cancer, stomach cancer, prostate cancer and non-small-cell ...

with or without axitinib have been completed. Results suggest that Crenolanib is well tolerated as a single agent, and can also be safely combined with

and axitinib due to their non-overlapping toxicity profiles.

Clinical trials

* * * * *

References

External links

"PDGFR Inhibitor CP-868596 (Code C64639)"
National Cancer Institute Thesaurus.
"PDGFR and Human Cancer"
AROG Pharmaceuticals LLC. {{Growth factor receptor modulators Tyrosine kinase inhibitors Oxetanes Quinolines Piperidines Benzimidazoles