Benzimidazoles: From Antiproliferative to Multitargeted Anticancer Agents

Benzimidazole derivatives are known to act against a range of biological targets and thus gained clinical applications in a wide spectrum of diseases. Few examples of multitargeted benzimidazole derivatives that were reported during the last decade will be described in this chapter. Multitargeting agents for serving the polypharmacology approach to combat shortcomings of the main one-drug-one target main dogma will be briefly explored. In that context, the multitargeting benzimidazole derivatives gain a special attention. This includes discovery (hit-to-lead), structure-activity relationship (SAR), and binding mode of at least one lead (or hit) in each group. Special attention will be given to two structures dovitinib and AT9283 that are reported to exhibit potent in vitro and in vivo activities against a group of kinases and non-kinase target (as shown recently for dovitinib)

p185(BCR/ABL) has a lower sensitivity than p210(BCR/ABL) to the allosteric inhibitor GNF-2 in Philadelphia chromosome-positive acute lymphatic leukemia

Background: The t(9;22) translocation leads to the formation of the chimeric breakpoint cluster region/c-abl oncogene 1 (BCR/ABL) fusion gene on der22, the Philadelphia chromosome. The p185(BCR/ABL) or the p210(BCR/ABL) fusion proteins are encoded as a result of the translocation, depending on whether a "minor" or "major" breakpoint occurs, respectively. Both p185(BCR/ABL) and p210(BCR/ABL) exhibit constitutively activated ABL kinase activity. Through fusion to BCR the ABL kinase in p185(BCR/ABL) and p210(BCR/ABL) "escapes" the auto-inhibition mechanisms of c-ABL, such as allosteric inhibition. A novel class of compounds including GNF-2 restores allosteric inhibition of the kinase activity and the transformation potential of BCR/ABL. Here we investigated whether there are differences between p185(BCR/ABL) and p210(BCR/ABL) regarding their sensitivity towards allosteric inhibition by GNF-2 in models of Philadelphia chromosome-positive acute lymphatic leukemia. Design and methods: We investigated the anti-proliferative activity of GNF-2 in different Philadelphia chromosome-positive acute lymphatic leukemia models, such as cell lines, patient-derived long-term cultures and factor-dependent lymphatic Ba/F3 cells expressing either p185(BCR/ABL) or p210(BCR/ABL) and their resistance mutants. Results: The inhibitory effects of GNF-2 differed constantly between p185(BCR/ABL) and p210(BCR/ABL) expressing cells. In all three Philadelphia chromosome-positive acute lymphatic leukemia models, p210(BCR/ABL)-transformed cells were more sensitive to GNF-2 than were p185BCR/ABL-positive cells. Similar results were obtained for p185(BCR/ABL) and the p210(BCR/ABL) harboring resistance mutations. Conclusions: Our data provide the first evidence of a differential response of p185(BCR/ABL)- and p210(BCR/ABL)- transformed cells to allosteric inhibition by GNF-2, which is of importance for the treatment of patients with Philadelphia chromosome-positive acute lymphatic leukemia

Targeting the oligomerization of BCR/ABL by membrane permeable competitive peptides inhibits the proliferation of Philadelphia Chromosome positive leukemic cells

The BCR/ABL fusion protein is the hallmark of Philadelphia Chromosome positive (Ph+) leukemia. The constitutive activation of the ABL-kinase in BCR/ABL cells induces the leukemic phenotype. Targeted inhibition of BCR/ABL by small molecule inhibitors reverses the transformation potential of BCR/ABL. Recently, we definitively proved that targeting the tetramerization of BCR/ABL mediated by the N-terminal coiled-coil domain (CC) using competitive peptides, representing the helix-2 of the CC, represents a valid therapeutic approach for treating Ph+ leukemia. To further develop competitive peptides for targeting BCR/ABL, we created a membrane permeable helix-2 peptide (MPH-2) by fusing the helix-2 peptide with a peptide transduction tag. In this study, we report that the MPH-2: (i) interacted with BCR/ABL in vivo; (ii) efficiently inhibited the autophosphorylation of BCR/ABL; (iii) suppressed the growth and viability of Ph+ leukemic cells; and (iv) was efficiently transduced into mononuclear cells (MNC) in an in vivo mouse model. This study provides the first evidence that an efficient peptide transduction system facilitates the employment of competitive peptides to target the oligomerization interface of BCR/ABL in vivo

Allosteric inhibition enhances the efficacy of ABL kinase inhibitors to target unmutated BCR-ABL and BCR-ABL-T315I

Background: Chronic myelogenous leukemia (CML) and Philadelphia chromosome-positive (Ph+) acute lymphatic leukemia (Ph + ALL) are caused by the t(9;22), which fuses BCR to ABL resulting in deregulated ABL-tyrosine kinase activity. The constitutively activated BCR/ABL-kinase "escapes" the auto-inhibition mechanisms of c-ABL, such as allosteric inhibition. The ABL-kinase inhibitors (AKIs) Imatinib, Nilotinib or Dasatinib, which target the ATP-binding site, are effective in Ph + leukemia. Another molecular therapy approach targeting BCR/ABL restores allosteric inhibition. Given the fact that all AKIs fail to inhibit BCR/ABL harboring the 'gatekeeper' mutation T315I, we investigated the effects of AKIs in combination with the allosteric inhibitor GNF2 in Ph + leukemia. Methods: The efficacy of this approach on the leukemogenic potential of BCR/ABL was studied in Ba/F3 cells, primary murine bone marrow cells, and untransformed Rat-1 fibroblasts expressing BCR/ABL or BCR/ABL-T315I as well as in patient-derived long-term cultures (PDLTC) from Ph + ALL-patients. Results: Here, we show that GNF-2 increased the effects of AKIs on unmutated BCR/ABL. Interestingly, the combination of Dasatinib and GNF-2 overcame resistance of BCR/ABL-T315I in all models used in a synergistic manner. Conclusions: Our observations establish a new approach for the molecular targeting of BCR/ABL and its resistant mutants using a combination of AKIs and allosteric inhibitors

Oleylamine-carbonyl-valinol inhibits auto-phosphorylation activity of native and T315I mutated Bcr-Abl, and exhibits selectivity towards oncogenic Bcr-Abl in SupB15 ALL cell lines

Chronic myeloid leukemia (CML) is characterized by the presence of p210Bcr-Abl which exhibits an abnormal kinase activity. Selective Abl kinase inhibitors have been successfully established for the treatment of CML. Despite high rates of clinical response, CML patients can develop resistance against these kinase inhibitors mainly due to point mutations within the Abl protein kinase domain. Previously, we have identified oleic acid as the active component in the mushroom Daedalea gibbosa that inhibited the kinase activity of Bcr-Abl. Here, we report that the oleyl amine derivatives, S-1-(1-Hydroxymethyl-2-methyl-propyl)- 3-octadec-9-enyl-urea [oleylaminocarbonyl-L-Nvalinol, oroleylaminocarbonyl-S-2-isopropyl-N-ethanolamine, oleylamine-carbonyl-L-valinol] (cpd 6) and R-1-(1-Hydroxymethyl- 2-methyl-propyl)-3-octadec-9-enyl-urea [oleylamineocarbonyl- D-N-valinol, oleylaminocarbonyl-R-2-isopropyl- N-ethanolamine, or oleylamine-carbonyl-D-valinol] (cpd 7), inhibited the activity of the native and T315I mutated Bcr-Abl. Furthermore, cpd 6 and 7 exhibited higher activity towards the oncogenic Bcr-Abl in comparison to native c-Abl in SupB15 Ph-positive ALL cell line.This work was supported, in part, by DFG-RU 728/3-2 to MR, YN and JM

Overcoming Bcr-Abl T315I mutation by combination of GNF-2 and ATP competitors in an Abl-independent mechanism

ABSTRACT: BACKGROUND: Philadelphia positive leukemias are characterized by the presence of Bcr-Abl fusion protein which exhibits an abnormal kinase activity. Selective Abl kinase inhibitors have been successfully established for the treatment of Ph (+) leukemias. Despite high rates of clinical response, Ph (+) patients can develop resistance against these kinase inhibitors mainly due to point mutations within the Abl protein. Of special interest is the 'gatekeeper' T315I mutation, which confers complete resistance to Abl kinase inhibitors. Recently, GNF-2, Abl allosteric kinase inhibitor, was demonstrated to possess cellular activity against Bcr-Abl transformed cells. Similarly to Abl kinase inhibitors (AKIs), GNF-2 failed to inhibit activity of mutated Bcr-Abl carrying the T315I mutation. METHODS: Ba/F3 cells harboring native or T315I mutated Bcr-Abl constructs were treated with GNF-2 and AKIs. We monitored the effect of GNF-2 with AKIs on the proliferation and clonigenicity of the different Ba/F3 cells. In addition, we monitored the auto-phosphorylation activity of Bcr-Abl and JAK2 in cells treated with GNF-2 and AKIs. RESULTS: In this study, we report a cooperation between AKIs and GNF-2 in inhibiting proliferation and clonigenicity of Ba/F3 cells carrying T315I mutated Bcr-Abl. Interestingly, cooperation was most evident between Dasatinib and GNF-2. Furthermore, we showed that GNF-2 was moderately active in inhibiting the activity of JAK2 kinase, and presence of AKIs augmented GNF-2 activity. CONCLUSIONS: Our data illustrated the ability of allosteric inhibitors such as GNF-2 to cooperate with AKIs to overcome T315I mutation by Bcr-Abl-independent mechanisms, providing a possibility of enhancing AKIs efficacy and overcoming resistance in Ph+ leukemia cells

Diazido mixed-amine platinum(IV) anticancer complexes activatable by visible-light form novel DNA adducts

Platinum diam(m)ine complexes, such as cisplatin, are successful anticancer drugs, but suffer from problems of resistance and side-effects. Photoactivatable PtIV prodrugs offer the potential of targeted drug release and new mechanisms of action. We report the synthesis, X-ray crystallographic and spectroscopic properties of photoactivatable diazido complexes trans,trans,trans-[Pt(N3)2(OH)2(MA)(Py)] (1; MA=methylamine, Py=pyridine) and trans,trans,trans-[Pt(N3)2(OH)2(MA)(Tz)] (2; Tz=thiazole), and interpret their photophysical properties by TD-DFT modelling. The orientation of the azido groups is highly dependent on H bonding and crystal packing, as shown by polymorphs 1 p and 1 q. Complexes 1 and 2 are stable in the dark towards hydrolysis and glutathione reduction, but undergo rapid photoreduction with UVA or blue light with minimal amine photodissociation. They are over an order of magnitude more potent towards HaCaT keratinocytes, A2780 ovarian, and OE19 oesophageal carcinoma cells than cisplatin and show particular potency towards cisplatin-resistant human ovarian cancer cells (A2780cis). Analysis of binding to calf-thymus (CT), plasmids, oligonucleotide DNA and individual nucleotides reveals that photoactivated 1 and 2 form both mono- and bifunctional DNA lesions, with preference for G and C, similar to transplatin, but with significantly larger unwinding angles and a higher percentage of interstrand cross-links, with evidence for DNA strand cross-linking further supported by a comet assay. DNA lesions of 1 and 2 on a 50 bp duplex were not recognised by HMGB1 protein, in contrast to cisplatin-type lesions. The photo-induced platination reactions of DNA by 1 and 2 show similarities with the products of the dark reactions of the PtII compounds trans-[PtCl2(MA)(Py)] (5) and trans-[PtCl2(MA)(Tz)] (6). Following photoactivation, complex 2 reacted most rapidly with CT DNA, followed by 1, whereas the dark reactions of 5 and 6 with DNA were comparatively slow. Complexes 1 and 2 can therefore give rapid potent photocytotoxicity and novel DNA lesions in cancer cells, with no activity in the absence of irradiation

Platinum (IV)-fatty acid conjugates overcome inherently and acquired Cisplatin resistant cancer cell lines: an in-vitro study

BACKGROUND: Platinum-based drugs are used as cancer chemotherapeutics for the last 40 years. However, drug resistance and nephrotoxicity are the major limitations of the use of platinum-based compounds in cancer therapy. Platinum (IV) complexes are believed to act as platinum prodrugs and are able to overcome some of platinum (II) limitations. METHODS: A number of previously sensitized platinum (IV) complexes were evaluated for their anti-cancer activity by monitoring ability to affect proliferation, clonigenicity and apoptosis induction of Cisplatin sensitive and resistant cancer cells. In addition, the uptake of Cisplatin and the platinum (IV) derivatives to Cisplatin sensitive and resistant cancer cells was monitored. RESULTS: The bis-octanoatoplatinum (IV) complex (RJY13), a Cisplatin derivative with octanoate as axial ligand, exhibited strong anti-proliferative effect on the Cisplatin resistant and sensitive ovarian cells, A2780cisR and A2780, respectively. Moreover, RJY13 exhibited good activity in inhibiting clonigenicity of both cells. Anti-proliferative activity of RJY13 was mediated by induction of apoptosis. Interestingly, a bis-lauratopaltinum (IV) complex (RJY6) was highly potent in inhibiting clonigenicity of both Cisplatin sensitive and Cisplatin resistant cells, however, exhibited reduced activity in assays that utilize cells growing in two dimensional (2D) conditions. The uptake of Cisplatin was reduced by 30% in A2780 in which the copper transporter-1 (Ctr1) was silenced. Moreover, uptake of RJY6 was marginally dependent on Ctr1, while uptake of RJY13 was Ctr1-independent. CONCLUSIONS: Our data demonstrated the potential of platinum (IV) prodrugs in overcoming acquired and inherited drug resistance in cancer cell lines. Moreover, our data demonstrated that the uptake of Cisplatin is partially dependent on Ctr1 transporter, while uptake of RJY6 is marginally dependent on Ctr1 and RJY13 is Ctr1-independent. In addition, our data illustrated the therapeutic potential of platinum (IV) prodrugs in cancer therapy