Imatinib-Resistant BCR-ABL Mutant Cellular Screening Paradigm To Characterize Promising Small-Molecule Inhibitors: T315I-BCR-ABL Targeted Drug Discovery.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2181-2181
Author(s):  
Mohammad Azam ◽  
William C. Shakespeare ◽  
Chester Metcalf ◽  
Yihan Wang ◽  
Raji Sunderamoorthi ◽  
...  
Keyword(s):  
Drug Discovery ◽  
Structural Analysis ◽  
Cell Lines ◽  
Small Molecule ◽  
Kinase Inhibitors ◽  
Kinase Inhibitor ◽  
Drug Binding ◽  
Imatinib Resistance ◽  
Inhibition Of Proliferation ◽  
Imatinib Resistant

Abstract In patients with chronic myeloid leukemia (CML), kinase domain mutations account for imatinib resistance in the majority of cases. Mutations cause either a direct steric hindrance to drug binding or a conformational change that favors kinase activation, which therefore precludes imatinib binding. We have previously characterized the dual Src-Abl kinase inhibitor AP23464 and found it to effectively suppress the growth of cells expressing native and essentially all imatinib-resistant variants of BCR-ABL, with the notable exception of the gatekeeper T315I mutant (Azam et al., Proc. Natl. Acad. Sci. USA, 103: 9244, 2006). Following this work, we have used mutant panel screening and integrated structural analysis to further characterize key analogs designed to overcome T315I resistance, as exemplified by AP23846 and AP24163. Both molecules effectively inhibit the tyrosine kinase activity of wild type (WT) and T315I variants of BCR-ABL, and inhibit the proliferation of BaF3-derived cell lines expressing these enzymes (see Table below). AP24163 was further characterized against a broader panel of imatinib-resistant BCR-ABL-expressing cell lines and showed a promising profile of proliferation inhibition. Comparison of these data with structural models of the mutants provides insights into the basis for the ability of AP24163 to overcome imatinib resistance. Refinement of small-molecule kinase inhibitors by the integration of sequential screening of panels of mutants coupled with structural analysis is a powerful drug discovery paradigm that is applicable to an increasing number of targeted therapeutic agents. INHIBITION OF PROLIFERATION OF BAF3 CELLS EXPRESSING BCR-ABL AND ITS VARIANTS (IC50 in nM) IMATINIB AP23464 AP23846 AP24163 WT 600 14 500 7 T315I >20000 >1000 500 480 L248R >20000 92 ND 64 G250E 5000 25 ND 63 Q252H 3000 40 ND 42 Y253H 18000 32 ND 44 E255K 12000 74 ND 24 BAF3+IL3 >20000 >1000 500 >10000 Figure Figure

Dasatinib (BMS-354825) Overcomes Multiple Mechanisms of Imatinib Resistance in Chronic Myeloid Leukemia (CML).

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1994-1994 ◽  
Author(s):  
Francis Y. Lee ◽  
Mei-Li Wen ◽  
Rajeev Bhide ◽  
Amy Camuso ◽  
Stephen Castenada ◽  
...  
Keyword(s):  
Cell Lines ◽  
Kinase Inhibitor ◽  
Leukemic Cell ◽  
K562 Cells ◽  
Src Family Kinases ◽  
Imatinib Resistance ◽  
Over Expression ◽  
Imatinib Resistant

Abstract Resistance to imatinib is a growing concern in CML, particularly in advanced disease. The most common cause of resistance is mutations in BCR-ABL, but other mechanisms have also been identified, including over-expression of BCR-ABL, activation of SRC family kinases and the P-glycoprotein (PGP) efflux pump (via MDR1 over-expression). Dasatinib (BMS-354825) is a novel, oral, multi-targeted tyrosine kinase inhibitor that targets BCR-ABL and SRC kinases. Dasatinib has 325-fold greater potency versus imatinib in cell lines transduced with wild-type BCR-ABL and is active against 18 out of 19 BCR-ABL mutations tested that confer imatinib resistance (Shah et al, Science305:399, 2004; O’Hare et al, Cancer Res65:4500–5, 2005), and preliminary results from a Phase I study show that it is well tolerated and has significant activity in imatinib-resistant patients in all phases of CML (Sawyers et al, J Clin Oncol23:565s, 2005; Talpaz et al, J Clin Oncol23:564s, 2005). We assessed the ability of dasatinib to overcome a variety of mechanisms of imatinib resistance. First, the leukemic-cell killing activity of dasatinib was tested in vitro in three human imatinib-resistant CML cell lines (K562/IM, MEG-01/IM and SUP-B15/IM). Based on IC50 values, dasatinib had >1000-fold more potent leukemic-cell killing activity compared with imatinib versus all three cell lines. Furthermore, in mice bearing K562/IM xenografts, dasatinib was curative at doses >5 mg/kg, while imatinib had little or no impact at doses as high as 150 mg/kg, its maximum tolerated dose. We determined that the MEG-01/IM and SUP-B15/IM cell lines carried BCR-ABL mutations known to confer imatinib resistance to imatinib clinically (Q252H and F359V, respectively). In K562/IM cells, BCR-ABL mutations or BCR-ABL over-expression were not detected, but the SRC family member FYN was over-expressed. PP2, a known inhibitor of SRC family kinases but not BCR-ABL, could reverse the imatinib resistance in these cells. Together, these data suggest that activation of FYN may be a cause of imatinib resistance in K562/IM. Based on cell proliferation IC50, we found that the anti-leukemic activity of dasatinib in K562/IM cells was 29-fold more potent compared with AMN107 (a tyrosine kinase inhibitor that inhibits BCR-ABL but not SRC family kinases). Given that the human serum protein binding of dasatinib, imatinib and AMN107 were 93, 92 and >99% respectively, the difference in potency between dasatinib and AMN107 in vivo may be far greater than the simple fold-difference in the in vitro IC50 values. Finally, in K562 cells over-expressing PGP (K562/ADM), we found that dasatinib was only 6-fold less active than in parental K562 cells. Because of the extreme potency of dasatinib in K562 cells, this reduced potency still afforded an IC50 of 3 nM, which is readily achievable in vivo. Indeed, in mice bearing K562/ADM xenografts, dasatinib was curative at 30 mg/kg, with significant anti-leukemic activity at 15 mg/kg. In conclusion, the rational design of dasatinib as a multi-targeted kinase inhibitor allows this agent to overcome a variety of mechanisms of resistance to imatinib in CML, including mechanisms that are not overcome by agents with a narrower spectrum of inhibition, such as AMN107. Dasatinib is currently in Phase II evaluation in imatinib-resistant/-intolerant patients in the ‘START’ program, and in Phase I evaluation in solid tumors.

Induction of Apoptosis In Imatinib-Resistant BCR-ABL1-Positive Leukemia Cell Lines by Bortezomib

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 4469-4469
Author(s):  
Hilmar Quentmeier ◽  
Sonja Eberth ◽  
Julia Romani ◽  
Margarete Zaborski ◽  
Hans G. Drexler
Keyword(s):  
Cell Lines ◽  
Kinase Inhibitor ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Philadelphia Chromosome ◽  
Leukemia Cell ◽  
Resistant Cell ◽  
Imatinib Resistance ◽  
Imatinib Resistant ◽  
Induced Apoptosis

Abstract Abstract 4469 The BCR-ABL1 translocation occurs in chronic myeloid leukemia (CML) and in 25% of cases with acute lymphoblastic leukemia (ALL). We screened a panel of BCR-ABL1 positive cell lines to find models for imatinib-resistance studies. Five of 19 BCR-ABL1 positive cell lines were resistant to imatinib-induced apoptosis (KCL-22, MHH-TALL1, NALM-1, SD-1, SUP-B15). None of the five resistant cell lines carried mutations in the kinase domain of BCR-ABL1 and – consequently – all also showed resistance to the second generation kinase inhibitors, nilotinib or dasatinib. All Philadelphia chromosome (Ph)-positive cell lines demonstrated constitutive phosphorylation of STAT5 and S6. Imatinib induced dephosphorylation of both BCR-ABL1 downstream effectors in responsive cell lines, but - remarkably – induced dephosphorylation of STAT5 in resistant cell lines as well. By administering well-described signalling pathway inhibitors we were able to show that activation of mTOR complex 1 was responsible for the constitutive S6 phosphorylation of imatinib-resistant cells. Neither BCR-ABL1 nor Src kinases or Ras/Rac-GTPases underlie tyrosine kinase inhibitor resistance in these cell lines. In conclusion, none of the five TKI-resistant cell lines showed aberrant activation of previously-described oncogenic pathways which would explain their resistance. These findings raise the question whether these cell lines might help to find a novel – alternative – explanation for TKI resistance. Interestingly, the proteasome inhibitor bortezomib induced apoptosis in TKI-resistant and –sensitive Ph+ cell lines. Bortezomib is being used for the treatment of multiple myeloma. Our findings support the notion that bortezomib might also be useful for the treatment of imatinib-resistant CML. Disclosures: No relevant conflicts of interest to declare.

The IKK Inhibitor PS1145 Allows to Overcome Imatinib Resistance.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 2940-2940
Author(s):  
Daniela Cilloni ◽  
Francesca Messa ◽  
Francesca Arruga ◽  
Ilaria Defilippi ◽  
Alessandro Morotti ◽  
...  
Keyword(s):  
Cell Lines ◽  
Phase 1 ◽  
Chronic Phase ◽  
Colony Growth ◽  
Resistant Cell ◽  
Proliferation Rate ◽  
Imatinib Resistance ◽  
Inhibition Of Proliferation ◽  
Imatinib Resistant ◽  
Resistant Cells

Abstract Since a number of CML patients are resistant to Imatinib, additional molecular defects should be identified and targeted to improve the therapeutic strategies. A constitutive NF-kB activity has been demonstrated in several hematologic malignancies, therefore NF-kB blocking approaches have been introduced as antineoplastic strategies. The phosphorilation of IKB by IKK leads to IKB degradation by the proteasome, so freeing NF-kB to enter the nucleus and activate transcription. IKK may therefore represent an attractive target for molecular therapies. The aim of the study was to evaluate the effects of the IKK inhibitor PS1145 (Millenium) in CML cell lines and patients sensitive and resistant to Imatinib. K562 and KCl cells both sensitive (s) and resistant (r) to Imatinib and the BM cells collected from 13 CML patients were incubated with PS1145 10 μM, with Imatinib 1 μM and with the combination of the two drugs for 24 and 48 hrs. 11 out of 13 patients were in chronic phase, 1 in accelerate phase and 1 in blastic phase. 3 out of 11 were cytogenetic resistant, one was also hematologically resistant. The NF-kB activity was evaluated by ELISA method, the proliferation rate by MTT assay, apoptosis by FACS. Immunofluorescence was use to identify the NF-kB localization. Moreover colony growth was evaluated in control and treated samples. PS1145 was able to reduce the DNA binding activity of NF-kB of 90% and 85% respect to the control in K562 and KCL cells.This was confirmed by the prevailing cytoplasmatic localization of NF-kB after PS1145 incubation. In K562s and KCls treated with Imatinib, we observed a reduction of proliferation of 48% and 37% respectively. By contrast no effect on proliferation was observed in K562r and KClr. The incubation with PS1145 inhibited the proliferation of 38% and 15% in K562s and KCls, and of 22% and 28% in K562r and KClr. Interestingly in resistant cell lines the association of Imatinib and PS1145 induced a marked inhibition of proliferation of 87% in K562r and 82% in KClr. Similarly, PS1145 inhibited BM cells proliferation of 30% (range 11% to 65%). Imatinib incubation of BM cells from sensitive patients reduced the proliferation rate of 41% (range 29%–55%) but no effects were observed in resistant patients. In the three resistant patients the incubation with both compounds resulted in an increased block of proliferation respect to PS1145 alone with an inhibition of 42%, 49% and 58% after 24 hrs and 70%, 77% and 79% after 48 hrs. Imatinib plus PS1145 induced a significant increase of apoptosis from 7% to 69% in K562r and from 9 % to 71% in KClr. In agreement this association induced 48%, 52% and 39% of apoptotic cells in BM from the three resistant patients and a colony growth inhibition of 86%. Our data clearly demonstrated that the IKK inhibitor PS1145 is able to induce growth arrest and apoptosis in CML cell lines and BM cells. This effect is more sound in Imatinib resistant cells treated with the association of Imatinib and PS1145. Although the exact mechanism of action of PS1145 in resistant cells is at present a pure speculation, these data may suggest an intriguing mechanism to induce apoptosis in imatinib resistant cells based on imatinib resistance itself. The combination of Imatinib and the IKK inhibitor could therefore represent a valid approach for the treatment of CML patients resistant to Imatinib therapy.

The Crystal Structure of Abl Kinase with BMS-354825, a Dual SRC/ABL Kinase Inhibitor.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 553-553 ◽  
Author(s):  
John S. Tokarski ◽  
John Newitt ◽  
Francis Y. Lee ◽  
Louis Lombardo ◽  
Robert Borzilleri ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Small Molecule ◽  
Kinase Inhibitor ◽  
High Rate ◽  
Dimensional Structure ◽  
Dual Function ◽  
Activation Loop ◽  
Imatinib Resistance ◽  
Abl Kinase ◽  
Imatinib Resistant

Abstract Chronic myeloid leukemia (CML) is a stem cell disorder caused by a constitutively activated tyrosine kinase, the BCR-ABL oncoprotein. Imatinib (STI571, Gleevec) is a small-molecule inhibitor of this kinase that produces clinical remissions in CML patients and is now frontline therapy for this disease. While this agent has a high rate of clinical success in early phases of CML, development of resistance to this drug becomes increasingly problematic in later stages of the disease. BMS-354825, a small-molecule dual-function SRC/ABL tyrosine kinase inhibitor, appears to overcome many of the limitations associated with imatinib therapy. BMS-354825 is 500-fold more potent than imatinib against BCR-ABL and more importantly retains activity against 14 of 15 imatinib-resistant BCR-ABL mutants (Shah et al., Science, 2004;305(5682):399). In addition, BMS-354825 proved to be equally effective against several pre-clinically and clinically derived tumor models of imatinib resistance (Lee et al., Proceedings of the AACR, Volume 45, March 2004 abstract number 3937). In order to better understand the molecular basis of the relationship between inhibitor chemistry and biological activity, the three-dimensional structure of the kinase domain of Abl kinase complexed with BMS-354825 was determined by X-ray crystallography. The structure reveals that BMS-354825 binds in the ATP-binding site. A comparison with the imatinib-Abl complex (PDB entry 1IEP) reveals that the central cores of BMS-354825 and imatinib occupy overlapping regions but that these two inhibitors extend in opposite directions. The activation loop is observed to be in the active conformation in the presence of bound BMS-354825 in contrast to bound imatinib. There do not appear to be any steric clashes that would preclude BMS-354825 from also binding to the inactive conformation of the activation loop. This observation suggests that the increased binding affinity of BMS-354825 over imatinib is at least partially due to its apparent ability to recognize multiple states of the enzyme. The P-loop is partially disordered as indicated by high B-factors and broken electron density which suggests that interactions between this part of the protein and BMS-354825 are less critical for binding. Interestingly, several imatinib-resistant mutations occur in the P-loop. The structure was analyzed for the 15 imatinib-resistant BCR-ABL mutants and attempts are made to rationalize the activity of BMS-354825 against these mutants.

Activity of ABL Kinase Inhibitors in Two Distinct Models of Imatinib Resistance.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 4819-4819
Author(s):  
Nicholas J. Donato ◽  
Ji Wu ◽  
William Bornmann ◽  
Moshe Talpaz
Keyword(s):  
Cell Lines ◽  
Inhibitory Activity ◽  
Kinase Inhibitors ◽  
Kinase Inhibitor ◽  
K562 Cells ◽  
Mutant Form ◽  
Imatinib Resistance ◽  
Resistant Variant ◽  
Lyn Kinase ◽  
Kinase Inhibitory Activity

Abstract The tyrosine kinase inhibitor imatinib mesylate (Gleevec) is effective in controlling BCR-ABL expressing leukemias but resistance occurs in a small subset of early stage patients and is very common in advanced stage patients. Resistance is associated with overexpression and/or mutations in the BCR-ABL gene but patients are also increasingly reported to fail imatinib therapy while retaining wild-type BCR-ABL expression. To circumvent or overcome resistance novel kinase inhibitors have been synthesized and tested clinically. However, while investigators have designed models to measure and predict activity of novel compounds in mutation-mediated imatinib resistance, other mechanisms of resistance have not been modeled or shown clinical relevance. In this report, the activity of four novel kinase inhibitors (norlotinib, dasatinib, SKI-606, ON012380) was compared in two distinct models of imatinib resistance. These models include cell lines established from natural resistant variant clones selected from imatinib sensitive cell lines and associated with a T315I BCR-ABL mutation (BV-173R) or overexpressed Lyn kinase (K562R). Kinase inhibitory activity in these models was compared to transfectant-based resistance models including BaF3 cells expressing the T315I mutant form of BCR-ABL and overexpression of Lyn kinase in K562 cells. K562R cells were completely resistant to imatinib and norlotinib but highly sensitive to Src/Abl inhibitors (dasatinib, SKI-606) but only partially sensitive to ON012380. Overexpression of Lyn in K562 cells reduced imatinib and norlotinib sensitivity (3-fold) but did not affect sensitivity to the other kinase inhibitors. BV-173R cells expressing the T315I mutant form of BCR-ABL were completely resistant to Abl-selective kinase inhibitors (imatinib, norlotinib) and ~100-fold less sensitive (IC50 ~ 2 microM) to Src/Abl-directed inhibitors (dasatinib, SKI-606) while the non-ATP competitive kinase inhibitor, ON012380, was equally effective against both BV-173 and BV-173R cells. Expression of the T315I mutant form of BCR-ABL in BaF3 cells completely blocked kinase inhibitory activity of all inhibitors except ON012380. IL-3 dependent BaF3 cells were not inhibited by imatinib, norlotinib or SKI-606 but were equally sensitive to ON012380 when compared to IL-3 independent BCR-ABL transfectants. Cellular sensitivity was associated with reduced phosphorylation of BCR-ABL, CrkL and Lyn kinase with all inhibitors except ON012380, which mediated apoptosis in the absence of alterations in tyrosine phosphorylation. Together, our results suggest that imatinib resistant cell models are useful in evaluating the activity of novel kinase inhibitors but need to be carefully interpreted and mechanistically tested. Additional mediators of imatinib resistance need to be defined and modeled so that an appropriate individualized therapy can be applied to most effectively overcome resistant disease.

Comparative Analysis of Two BCR-ABL Small Molecule Inhibitors Reveals Overlapping but Distinct Mechanisms of Resistance.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 552-552 ◽  
Author(s):  
Michael R. Burgess ◽  
Neil P. Shah ◽  
Brian J. Skaggs ◽  
Francis Y. Lee ◽  
Charles L. Sawyers
Keyword(s):  
Small Molecule ◽  
Small Molecule Inhibitors ◽  
Point Mutations ◽  
Kinase Domain ◽  
Drug Binding ◽  
Saturation Mutagenesis ◽  
Imatinib Resistance ◽  
Abl Kinase ◽  
Imatinib Resistant

Abstract A novel dual SRC/ABL kinase inhibitor, BMS-354825, is showing promise for the treatment of imatinib-resistant chronic myeloid leukemia not only in vitro (Shah NP, et al., Science 305:399), but also in a phase I clinical trial (ASH abstract: Sawyers CL, et al.) Resistance to imatinib is increasingly found in patients due to point mutations in the BCR-ABL kinase domain that do not impair kinase activity but prevent drug binding. BMS-354825 is more potent than imatinib and retains activity against 14 of 15 imatinib-resistant BCR-ABL mutants in vitro. The compound’s ability to inhibit imatinib-resistant forms of BCR-ABL is presumed to be due to its relaxed binding requirements, whereas imatinib requires the adoption of a closed conformation of the kinase to bind. We addressed the hypothesis that the relaxed binding requirements of BMS-354825 would limit the range of BCR-ABL mutations that confer drug resistance. To address this question, we employed a saturation mutagenesis experiment as described by others (Azam M, et al., Cell 112:831) and found that the spectrum of BMS-354825-resistant mutants was reduced compared to that of imatinib. In a series of such screens, mutations at only four amino acids have been isolated, two of which account for the vast majority of resistant clones. In contrast, Azam et al. isolated over 20 mutations in a screen for imatinib resistance, a finding which has been generally reproduced in our lab. All four BMS-354825-resistant mutations map to known BMS-354825 contact residues as shown by co-crystallographic studies (ASH abstract: Tokarski JS et al., Bristol-Myers Squibb). Mutations at L248, T315, and F317 show BMS-354825 resistance and have been previously reported to confer imatinib resistance. Mutation at V299 represents a novel mode of resistance. Interestingly, some point mutations conferring BMS-354825 resistance were at positions known to be mutated in cases of imatinib resistance, but the mutated residues differed. Furthermore, the identity of the mutated residue was crucial in conferring sensitivity or resistance to an individual drug as shown by comparison of cellular IC50’s (see table). For example, F317L was shown previously to confer imatinib resistance. F317V, on the other hand, demonstrates relative BMS-354825-resistance but is still exquisitely sensitive to imatinib. In a screen for mutants simultaneously resistant to both drugs, we consistently recover 30–50 fold fewer mutant clones compared to single drug treatment. All such clones isolated to date encode for T315I. Kinase domain point mutation is becoming an increasingly encountered clinical problem in diseases treated with small molecule inhibitors. Our findings suggest that combination therapy with imatinib and BMS-354825 may be of clinical utility in CML, particularly by delaying the development of resistance. IC50 for growth (nM) Baf3 Clone imatinib BMS-354825 p210 wt < 1,000 < 5 T315I > 10,000 > 500 T315A 1,000 100 F317L 2,000 10 F317V < 1,000 60 V299L 1,000 20 L248R > 10,000 20

Inhibition of T315I Bcr-Abl and Other Imatinib-Resistant Bcr-Abl Mutants by the Selective Abl Kinase Inhibitor SGX70393.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1373-1373 ◽  
Author(s):  
Thomas O’Hare ◽  
Christopher A. Eide ◽  
Jeffrey W. Tyner ◽  
Matthew J. Wong ◽  
Caitlyn A. Smith ◽  
...  
Keyword(s):  
Kinase Inhibitors ◽  
Kinase Inhibitor ◽  
Kinase Domain ◽  
Imatinib Resistance ◽  
Abl Kinase ◽  
Imatinib Resistant ◽  
Escape Mutants ◽  
A Cell ◽  
Almost All ◽  
Proliferation Assays

Abstract Imatinib effectively inhibits the tyrosine kinase activity of Bcr-Abl, the molecular driver of CML. Emergence of imatinib resistance due to mutations within the Bcr-Abl kinase domain (KD) has prompted the development of new Abl kinase inhibitors. A particularly important target is Bcr-Abl(T315I), which accounts for 15–20% of patients with resistance. To address this unresolved need, we profiled the novel Abl kinase inhibitor SGX70393 against native and mutant Bcr-Abl. Methods: We assessed the efficacy of SGX70393 in cellular and biochemical assays against a panel of KD mutants. Cell proliferation assays and Bcr-Abl tyrosine phosphorylation immunoblot analyses were performed for parental Ba/F3 cells, Ba/F3 cells expressing unmutated Bcr-Abl, or Ba/F3 cells expressing a single Bcr-Abl KD mutation (M244V, G250E, Q252H, Y253F, Y253H, E255K, E255V, F311L, T315I, F317L, M351T, F359V, V379I, L387M, H396P, or H396R). The resistance profile of SGX70393 was also evaluated using a recently developed accelerated, cell-based mutagenesis assay (Bradeen, et al. Blood, June 2006; doi:10.1182). Results: SGX70393 inhibited growth of cells expressing Bcr-Abl(T315I) (IC50: 7.3 nM) or unmutated Bcr-Abl (IC50: 12 nM). Sensitivity of Bcr-Abl mutants to SGX70393 partitioned into three categories: high (IC50&lt;25 nM: M244V, T315I, F359V, V379I, L387M, H396P, and H396R), medium (IC50&lt;300 nM: Q252H, Y253H, E255K, and F311L), and low (IC50&gt;500 nM: G250E, Y253F, E255V, and F317L). A cell-based mutagenesis screen for Bcr-Abl kinase domain escape mutants emerging in the presence of SGX70393 revealed a concentration-dependent reduction in surviving clones, with five previously reported Bcr-Abl mutations (L248M; G250E; Y253F; E255V; F317V) accounting for almost all resistance. Conclusions: (a) SGX70393 is a potent inhibitor of native and T315I mutant Bcr-Abl. (b) SGX70393 coverage extends to most clinically relevant mutants except mutations of the p-loop and F317.

scholarly journals A survey of the kinome pharmacopeia reveals multiple scaffolds and targets for the development of novel anthelmintics

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jessica Knox ◽  
Nicolas Joly ◽  
Edmond M. Linossi ◽  
José A. Carmona-Negrón ◽  
Natalia Jura ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Developmental Delay ◽  
Small Molecule ◽  
Parasitic Nematode ◽  
Kinase Inhibitor ◽  
Binding Pocket ◽  
Drug Binding ◽  
Nematode Infection ◽  
Selective Inhibitors ◽  
C Elegans

AbstractOver one billion people are currently infected with a parasitic nematode. Symptoms can include anemia, malnutrition, developmental delay, and in severe cases, death. Resistance is emerging to the anthelmintics currently used to treat nematode infection, prompting the need to develop new anthelmintics. Towards this end, we identified a set of kinases that may be targeted in a nematode-selective manner. We first screened 2040 inhibitors of vertebrate kinases for those that impair the model nematode Caenorhabditis elegans. By determining whether the terminal phenotype induced by each kinase inhibitor matched that of the predicted target mutant in C. elegans, we identified 17 druggable nematode kinase targets. Of these, we found that nematode EGFR, MEK1, and PLK1 kinases have diverged from vertebrates within their drug-binding pocket. For each of these targets, we identified small molecule scaffolds that may be further modified to develop nematode-selective inhibitors. Nematode EGFR, MEK1, and PLK1 therefore represent key targets for the development of new anthelmintic medicines.

scholarly journals Identification of Hsp90 inhibitors as potential drugs for the treatment of TSC1/TSC2 deficient cancer

2021 ◽  
Author(s):  
Evelyn M. Mrozek ◽  
Vineeta Bajaj ◽  
Yanan Guo ◽  
Izabela Malinowska ◽  
Jianming Zhang ◽  
...  
Keyword(s):  
Cell Lines ◽  
Kinase Inhibitors ◽  
Kinase Inhibitor ◽  
Xenograft Model ◽  
Growth Delay ◽  
Hsp90 Inhibitors ◽  
Null Cell ◽  
Standard Dosage

Inactivating mutations in either TSC1 or TSC2 cause Tuberous Sclerosis Complex, an autosomal dominant disorder, characterized by multi-system tumor and hamartoma development. Mutation and loss of function of TSC1 and/or TSC2 also occur in a variety of sporadic cancers, and rapamycin and related drugs show highly variable treatment benefit in patients with such cancers. The TSC1 and TSC2 proteins function in a complex that inhibits mTORC1, a key regulator of cell growth, which acts to enhance anabolic biosynthetic pathways. In this study, we identified and validated five cancer cell lines with TSC1 or TSC2 mutations and performed a kinase inhibitor drug screen with 197 compounds. The five cell lines were sensitive to several mTOR inhibitors, and cell cycle kinase and HSP90 kinase inhibitors. The IC50 for Torin1 and INK128, both mTOR kinase inhibitors, was significantly increased in three TSC2 null cell lines in which TSC2 expression was restored.  Rapamycin was significantly more effective than either INK128 or ganetespib (an HSP90 inhibitor) in reducing the growth of TSC2 null SNU-398 cells in a xenograft model. Combination ganetespib-rapamycin showed no significant enhancement of growth suppression over rapamycin. Hence, although HSP90 inhibitors show strong inhibition of TSC1/TSC2 null cell line growth in vitro, ganetespib showed little benefit at standard dosage in vivo. In contrast, rapamycin which showed very modest growth inhibition in vitro was the best agent for in vivo treatment, but did not cause tumor regression, only growth delay.

scholarly journals Covalent inhibitors of EGFR family protein kinases induce degradation of human Tribbles 2 (TRIB2) pseudokinase in cancer cells

2018 ◽  
Vol 11 (549) ◽  
pp. eaat7951 ◽  
Author(s):  
Daniel M. Foulkes ◽  
Dominic P. Byrne ◽  
Wayland Yeung ◽  
Safal Shrestha ◽  
Fiona P. Bailey ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Small Molecule ◽  
Kinase Inhibitors ◽  
Kinase Inhibitor ◽  
Growth Factor Receptor ◽  
Drug Repurposing ◽  
Protein Kinase Inhibitors ◽  
Cellular Mechanisms ◽  
Cellular Analysis

A major challenge associated with biochemical and cellular analysis of pseudokinases is a lack of target-validated small-molecule compounds with which to probe function. Tribbles 2 (TRIB2) is a cancer-associated pseudokinase with a diverse interactome, including the canonical AKT signaling module. There is substantial evidence that human TRIB2 promotes survival and drug resistance in solid tumors and blood cancers and therefore is of interest as a therapeutic target. The unusual TRIB2 pseudokinase domain contains a unique cysteine-rich C-helix and interacts with a conserved peptide motif in its own carboxyl-terminal tail, which also supports its interaction with E3 ubiquitin ligases. We found that TRIB2 is a target of previously described small-molecule protein kinase inhibitors, which were originally designed to inhibit the canonical kinase domains of epidermal growth factor receptor tyrosine kinase family members. Using a thermal shift assay, we discovered TRIB2-binding compounds within the Published Kinase Inhibitor Set (PKIS) and used a drug repurposing approach to classify compounds that either stabilized or destabilized TRIB2 in vitro. TRIB2 destabilizing agents, including the covalent drug afatinib, led to rapid TRIB2 degradation in human AML cancer cells, eliciting tractable effects on signaling and survival. Our data reveal new drug leads for the development of TRIB2-degrading compounds, which will also be invaluable for unraveling the cellular mechanisms of TRIB2-based signaling. Our study highlights that small molecule–induced protein down-regulation through drug “off-targets” might be relevant for other inhibitors that serendipitously target pseudokinases.

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