Crenolanib besylate (CP-868,596-26 or AR-868,596-26, 4-piperidinamine, 1-[2-[5-[(3-Methyl-3-oxetanyl) methoxy]-1H-benzimidazol-1-yl]- 8-quinolinyl]-, monobenzenesulfonate) is an investigational inhibitor being developed by AROG Pharmaceuticals, LLC. As of 2014,[needs update] the compound was being evaluated for safety and efficacy in clinical trials for various types of cancer, includingacute myeloid leukemia (AML),[1][2]gastrointestinal stromal tumor (GIST),[3] andglioma.[4]
Crenolanib is an orally bioavailable benzimidazole that selectively and potently inhibits signaling ofwild-type and mutant isoforms of class III receptor tyrosine kinases (RTK)FLT3 (FMS-like Tyrosine Kinase 3),PDGFR α (Platelet-Derived Growth Factor Receptor), and PDGFR β. Unlike most RTK inhibitors, crenolanib is a type I mutant-specific inhibitor that preferentially binds tophosphorylated active kinases with the ‘DFG in’ conformationmotif.[5]
Mutations ofFLT3 comprise one of the most frequently identified types of genetic alterations in acute myeloid leukemia.[7][8] Approximately one-third ofAML patients present with a mutation in this gene.[9] The majority of these mutations result in constitutive activation of downstream signaling pathways and aberrant cell growth.[7] Mutations in FLT3 have also been reported inacute lymphoblastic leukemia (ALL)[10] andmyelodysplastic syndrome (MDS).[11]
Crenolanib inhibits both wild typeFLT3 and its constitutively active mutations. In vitro studies have shown that crenolanib has lowKd for theFLT3 enzyme with constitutively activating internal tandem duplication (ITD) mutations andtyrosine kinase domain (TKD) mutations, D835H and D835Y, as compared to wild type. Crenolanib tightly binds toFLT3-ITD,FLT3-D835H andFLT3-D835Y withKd of 0.74 nM, 0.4 nM, and 0.18 nM, respectively.[14] Crenolanib inhibits the phosphorylation of theFLT3-ITD receptor in transfected TF-1 cells and theFLT3-D835Y TKD mutation in transfected Ba/F3 cells at nanomolarIC50 concentrations of 1.3 nM and 8.8 nM, respectively.[15]Immunoblot experiments performed in theMolm14FLT3-ITD positive cell line show that crenolanib inhibits downstream signaling ofFLT3 at a concentration of 10 nM.[15]MTT assay measurements of crenolanibcytotoxicity evaluated in theFLT3-ITD expressing cell linesMolm14 andMV411, showed that crenolanib is toxic atIC50 concentrations of 7 nM and 8 nM, respectively.[15]
Crenolanib has been shown to inhibitPDGFRα with anIC50 of 0.4 ng/mL in porcine aortic epithelial cell lines. InChinese hamster ovary (CHO) cells expressingPDGFRα, crenolanib inhibited the phosphorylation of wild typePDGFRα at anIC50 of 10 nM.[16] Additionally, crenolanib completely blockedPDGFRα phosphorylation and downstreamAKT signaling at a concentration between 0.1 and 1 uM in Ink4a/Arf-/- mouseastrocytes transfected to stably co-express both humanPDGFRα andPDGF AA.[17] Thelung cancer cell line H1703, which is reported to have amplification of bothPDGFRA (4q12) and PDGFC (4q32) genes on chromosome 4, and also overexpressPDGFRα, was sensitive to crenolanib with anIC50 of ~80 nM.[18] InCHO cells expressing an activating exon 18 (D842V)PDGFRα mutation, crenolanib was effective at anIC50 of 6nM and IC90 of 25nM. In addition, crenolanib also inhibited phosphorylation of the double mutantsPDGFRα (V561D + D842V and T674I + D842V).[16]
Crenolanib has been shown to inhibitPDGFRβ with anIC50 of 0.8 ng/mL in porcine aortic epithelial cell lines. Crenolanib inhibits the ability of recombinantPDGFRβ to phosphorylate a synthetic tyrosine substrate (poly-glutamic acid-tyrosine), with anIC50 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 forPDGFRβ with anIC50 of 10 nM when measured by BrdU assay and 1.25 uM byMTT assay.
Crenolanib has been shown to haveIC50 and Kd values of 67 nM and 78 nM, respectively, for wild typec-KIT in in vitro assays[citation needed]. Similar assays show that crenolanib inhibitsc-KIT activating mutations D816H and D816V withIC50 concentrations of 5.4 and 2.5 nM, respectively.[14][citation needed] Humanbone marrowprogenitor cell growth assays showed that crenolanib has modest effects onGM-CSF andBFUE driven colony formation at theIC50 concentration of 20 nM.[15]
Phase I single-agent[19] and Phase Ib combination[20] studies have investigated the clinical pharmacology of crenolanib in patients with cancer. Pharmacokinetic and safety studies of Crenolanib administered alone or in combination withdocetaxel with or withoutaxitinib have been completed. Results suggest that Crenolanib is well tolerated as a single agent, and can also be safely combined withdocetaxel andaxitinib due to their non-overlapping toxicity profiles.
Clinical trial numberNCT01229644 for "A Phase II Study of Crenolanib (CP-868,596), a Selective and Potent Inhibitor of PDGFR, for the Treatment of Adult Gliomas" atClinicalTrials.gov
Clinical trial numberNCT01243346 for "Phase II Study of Crenolanib (CP-868,596), for the Treatment of Patients With Advanced Gastrointestinal Stromal Tumors With the D842-related Mutations and Deletions in the PDGFRA Gene" atClinicalTrials.gov
Clinical trial numberNCT01393912 for "PDGFR Inhibitor Crenolanib in Children/Young Adults With Diffuse Intrinsic Pontine Glioma or Recurrent High-Grade Glioma" atClinicalTrials.gov
Clinical trial numberNCT01522469 for "Phase II Study of Crenolanib in Subjects With Relapsed/Refractory AML With FLT3 Activating Mutations" atClinicalTrials.gov
Clinical trial numberNCT01657682 for "A Phase II Study of Crenolanib in Relapsed/Refractory Acute Myeloid Leukemia Patients With FLT3 Activating Mutations" atClinicalTrials.gov
^Cancer Genome Atlas Research Network; Ley, T. J.; Miller, C.; Ding, L.; Raphael, B. J.; Mungall, A. J.; Robertson, A.; Hoadley, K.; Triche Jr, T. J.; Laird, P. W.; Baty, J. D.; Fulton, L. L.; Fulton, R.; Heath, S. E.; Kalicki-Veizer, J.; Kandoth, C.; Klco, J. M.; Koboldt, D. C.; Kanchi, K. L.; Kulkarni, S.; Lamprecht, T. L.; Larson, D. E.; Lin, L.; Lu, C.; McLellan, M. D.; McMichael, J. F.; Payton, J.; Schmidt, H.; Spencer, D. H.; et al. (2013)."Genomic and Epigenomic Landscapes of Adult De Novo Acute Myeloid Leukemia".New England Journal of Medicine.368 (22):2059–2074.doi:10.1056/NEJMoa1301689.ISSN0028-4793.PMC3767041.PMID23634996.
^Yokota, S; Kiyoi, H; Nakao, M; Iwai, T; Misawa, S; Okuda, T; Sonoda, Y; Abe, T; Kahsima, K; Matsuo, Y; Naoe, T (2014-01-24). "Internal tandem duplication of the FLT3 gene is preferentially seen in acute myeloid leukemia and myelodysplastic syndrome among various hematological malignancies. A study on a large series of patients and cell lines".Leukemia.11 (10):1605–9.doi:10.1038/sj.leu.2400812.PMID9324277.S2CID12003642.
^abMuralidhara, C.; Ramachandran, A.; Jain, V. K. (2012). "Abstract 3683: Crenolanib, a novel Type I, mutant-specific inhibitor of Class III receptor tyrosine kinases, preferentially binds to phosphorylated kinases".Cancer Research.72 (8 Supplement): 3683.doi:10.1158/1538-7445.AM2012-3683.
^abcdGalanis, A.; Rajkhowa, T.; Muralidhara, C.; Ramachandran, A.; Levis, M. (2012). "Abstract 3660: Crenolanib: A next generation FLT3 inhibitor".Cancer Research.72 (8 Supplement): 3660.doi:10.1158/1538-7445.am2012-3660.
