ANT-ligands molecules and biological applications
The invention relates to molecules having ANT-ligands properties It more particularly relates to molecules useful for inducing apoptosis or similar cell death mechanisms and their use as therapeutical agents
Since ten yeai s ago the mitochondrion has been progressively recognized as an integrator-coordinator of apoptosis and a major checkpoint leading upon activation iπeversibl/ tc a regulated cell death pi ocess namely mitochondnal apoptosis This process is favoured by a sustained Ca2* accumulation in the mitochondrial matrix and manifests as signs of pro-apoptotic mitochondrial alteration namely permeability transition dissipation of the electi ochemical potential malπ> swelling cristae remodelling relocalization of Bax to mitochondria and the release of pro-apoptotic factors such as cytochioine c and AIF from mitochondria Depending on the physiopathological models mitochondrial membrane permeabilization i MMP) would affect the outer mitochondrial membiane or both membranes i e the outer and the inner membrane MMP is under the control of Bax and Bcl-2 family members which are respectively pro- and anti-apoptotic Thus apoptosis can be inhibited by overexpression of oncogenes (e g Bcl-2) or viral proteins (e g Vmia fi om Herpes virus) MMP is usually accompanied by a bioenergetic catastrophe a loss of transmembrane potential (Λψm ' an arrest of respiration a decrease in ATP level and an increase in reactive oxygen species I ROS I levels In this context two constitutive mitochondi ial proteins the adenine nucleotide translocator (ANT, inner membrane (IM)) and the voltage-dependent anion channel (VDAC outer membrane (OM)) cooperate with the Bax and Bcl-2 proteins family Bax is a pro-apoptotic cytosolic protein, which interacts with ligands, such as Bid and PUMA activates and translocates to the mitochondrion to induce cell death Furthermore, the ANT-Bax ccoperation has been reported in several physiopathological models These proteins belcng to the mitochondrial permeability transition pore (PTPCi a multiprotein complex localized at the contact sites of the OM and IM membranes The precise composition of this pore is still unknown but several independent hypotheses converge to the possibility that ANT WM) and VDAC (OM) interact to form a double channel In normal conditions this double channel opens transiently and mediates the channelling of ATP from the matrix (site of synthesis) to the cytosol (final destination) Upon stimulation by a /vide range of endogenous as well as exogenous stimuli PTPC opens as a high conductance channel to allow the free passage of water and metabolites of MM<1 5 kDa, indjcing a matrix swelling and the subsequent rupture of the OM thus facilitating the release of mitochondrial proteins into the cytosol This model has been challenged by a publication in 2004 based on the generation Df conditional double-knock out mice for ANT1 and ANT2 in
the liver two isoforms of ANT suggesting that AMT could be dispensable for apoptosis (D Nevertheless a novel ANT isoform (ANT4) has been identified recently (2,3) and, as ANT represents the most abundant member of a large family of highly homologous members, i e the mitochondrial carriers, in the absence of ANT, another carrier might replace the functional role of ANT for the induction of MMP tc compensate the absence of ANT1 and 2 (4,5)
Interestingly, Jang et a/ (6) demonstrated that ANT2 suppiession by vector-based siRNA inhibits tumour growth in in wi o human breast cancer nodels This reveals the therapeutic potential of an ANT targeting approach in oncolog/ An attempt to target pharmacologically ANT has been previously undertaken, using the peptidic approach (7,8), and preliminary results revealed several technological difficulties resulting from the fact that peptides cannot penetrate into the cell and need to be coupled with targeting sequences (e g Tat Ant>
The inventors have ΠOΛ' prepared ANT-targeted small molecules particularly for therapeutic applications Medicinal chemistry approach coupled with in silico studies yield to several small organic compounds which proved to be specific for ANT and fulfil draggability criteria (good cell penetration and bicdisponibility)
Such molecules may have other cellular targets
The invention thus relates to molecules particularly able to induce apoptosis or similar cell death mechanisms
It also relates to those cf the molecules vvhich are new compounds
According to another object the invention relates to pharmaceutical compositions comprising said new molecules as active pi maples of drugs
According to still another object, the invention relates to the use of said above mclecules able to induce apoptosis for making drugs inducing apoptosis
This is another aim of this invention to provide a method for inducing cell death by targeting the ADP/ATP translocalor ANT in cellula
The molecules used as ligands according to the invention have a substituted nitrogeneous heterocycle designated by A, wheiein
- A is a substituted pyrazinone of formula I
R and R , in the above radicals being identical or different and iepresenting H or a C1 C12 alkyl or cycloalkyl radical, and Ar is a phenyl or Het , Het representing an heterocyclic i adical Λ'lth one or several hetero atoms selected between N S and O, said phenyl or heterocycle being optionally substituted by one or several atoms, groups or radicals selected from halogen atoms such as Cl Br, I halogenated groups such as - CCI3 or - CF3 -OH -OR -COOH or - COOR groups, phenyl linear or tranched C 1 -C12 alkyl radical, -NH-COR or
- CN, said atoms, groups or radicals occupying the same or different positions on the phenyl or heterocyclic radical a linear or branched C1-C12 alkyl radical, a linear or branched C2-C12 alkylene radical dical,
- R2 ιs
- (CH;)
n - Ar Ar being such as above defined and being optionally substituted such as above defined a linear or blanched C1-C12 alkyl or C2-C12 alkylene radical with one or several double bonds
a linear oi branched C1-C12 alkyl radical
R3 forms a phenyl or an heterocyclic condensed group with the two adjacent carbons of the pyrazolone residue said condensed group being optionally substituted such as abo/e defined foi Ar and Het and-Or condensed to a cyclohexyl or oxanyl group in turn optionally substituted such as above defined foi Ar
n is O or an integer from 1 to 5 or
- A is a substituted pyrazine ot formula Il
wherein
- Rj is a -CO-NH-Ar radical optionally substituted such as above defined
- R5 forms a phenyl or heterocyclic group condensed to the two adjacent carbon groups of the pyrazine residue said phenyl or heteiocyclic group being optionally substituted such as above defined and
Ar being such as above defined with respect Io formula I or - A is a substituted pyridine group of formula ill
wherein,
Ar and R2 are as above defined with respect to formula I.
In a first family, preferred ligands have formula I wherein R3 forms a phenyl or a thienyl group with the pyrazinoπe residue said phenyl or thienyl group being optionally substituted such as above defined.
Advantageously
R1 is selected from the group comprising - (CH2 1Ir1-CO-OH a branched C 1 - C6 alkyl group; -<CH:)n- C3-C6 cycloalkyl group; - (CH:)n-NH:, - (CHz)n-NH-CO-R1 - (CH:)n Het , with Het representing a pyridyl radical
In more preferred derivatives of said first family, R1 and R3 are as above defined and R2 is a - (CHi)n - phenyl group, advantageously substituted by one or several C1-C3 alkyl groups or an halogen, particularly Cl.
Preferred derivatives have the following formulae
Compound 1 Compound 2
Compound 9 Compound 10
Compound 12
Compound 11
Compound 13 Compound 14
Compound 15 Compound 16
In a second family, preferred ligands haye formula Il wherein Ar and R4 are a phenyl group, advantageously substituted such as above defined with respect to formula I In more preferred derivatives R5 forms a phenyl group with the two adjacent carbon atoms of the pyrazme residue or a thienyl group optionally condensed to a cyclohex/l or a oxanyl group, optionally substituted such as above defined with respect to Ar in formula I
Preferred derivatives have the following formulae:
In a third embodiment of the invention preferred ligands have formula III, wheiein both Ar are phenyl groups optionally substituted such as above defined, and R2 is as abcve defined with respect to formula I piefeiably a - (CH
2)
n - COOH group
Preferred derivatives have the following formulae
The inv ention also relates to the above defined derivatives as new products, the following compounds 1 , 2, 17, 18 19 20 and 21 being excluded
More particularly, taking advantage of the published crystal structure of bovine ANT1 with its specific inhibitor carboxyatractyloside (9) (Fig 1A), the inventors have identified by molecular docking a library of putative ANT-ligands in silico Considering the high homology between bovine ANT1 and human ANT isoforms in term of tertiary structure, a three- dimensionnal analysis permitted ( 1) to localize the carboxyatractyloside a well-known inhibitor of ADP/ATP translocation, in the human ANT2 binding pocket (Fig 1 B) and (2) to identify chemical structures able to intei act similarly with ammo acid residues of the ANT binding pocket
The library is constituted of a total of 1 171 small commercial molecules among which 956 have been tested Each compound has been evaluated on the following in vitro screening assays HT-29 and B <PC3 tumour cells lines viability and ADP/ATP translocator activity of ANT on isolated mitochondria. These screening techniques lead to selection of
molecules being efficient ANT inhibitors with important cellular effects (cell death or growth delay)
Among them compound 1 induces dissipation of the mitochondrial trans-membrane potential and apoptosis hallmarks that are abolished by caspase inhibitors i Fig 3) and pro- apoptotic factors (Bax/Bak) deletion Interestingly compound 1 is not cytotoxic for all cellular types Indeed the Wι-38 cells express the ANT3 isofoi m as HT-29 and BxPC3 while the ANT2 isoform is almcst no detectable (Fig 4A In correlation with ANT expression levels, compound 1 to icity on normal lung fibroblasts is minor compared to tumor cells (HT-29 B>PC3) (Fig 4B) On lymphocytes i PBMC, not shown) the compound presents no sign of toxicity for doses below 400 μM
The importance of ANT isoforins in cytotoxic effects of the selected ANT-ligands has been evaluated using S cerevisiae strains deficient for ANT isoforms ( Fig 5) Clonogenic assays on these strains are used to ensure that cy totoxic effects of the ANT-ligands are really due to the expression of ANTs in the cells The inventors found that the strain deficient for ANT isoforms I ΛANTI 2 & 3 HS more resistant to the compound 1 than the wild-type iWT) control strain indicating that the mechanism of cell death induced by this ligand is ANT-dependent (Fig 5)
For the first time it is possible to demonstrate that an ANT-hgand induces cell death bv targeting the ADP/ATP translocator ANT in cellula Structure/activity relationship studies lead to the optimization of the compound in terms of killing efficiency and selectivity fci one of the ANT isoforms (Fig 6) The chemical structures of optimized compound 1 derivatives are given in Fig 7
The indention also relates to a method for inducing cell death by targeting the ADP/ATP translocator ANT in cellula comprising adding an effective amount of at least one of the aboye defined derivatives
The above defined molecules are advantageously used as active principle of drugs The invention thus also relates to phai maceutical compositions comprising a therapeutically effective amount of at least one of the above defined molecules in association with a pharmaceutically acceptable carrier Said compositions are adrninistrable by the appropriate way, comprising oral parenteral (subcutaneous, intravenous!, injectable and topical including intratumoral ways of administration
The / are advantageously formulated as liquid solutions with appropriate carriers and/or diluents and/or solvents
The pharmaceutical compositions of the invention may further comprise a therapeutic agent selected in the group comprising chemotherapeutics, apoptosis modulators antimicrobial antiviral antifungal or anti-inflainmatcry agents
The above defined pharmaceutical compositions are useful for cancer thei ap/ The invention also relates to the use of a ligand such as above defined for making a proapoptotic drug for treating cancer
Therapeutically effective amount of the compounds will advantageously be O 1 mg<kg to 100 mg'kg body weight with a daily to weekly administration
The invention also relates to a method for the synthesis of the above defined ligands The derivatives of foi mula I are thus preferably obtained b/ reacting a derivative of formula IV
wherein Rc is R1 such as above defined or
- radical and R3 is as above defined
with a derivative of formula V
R2 - R' (V)
wherein R2 is as above defined and R" is a reactive group such as an halogen Preferably R ' is Cl or Br
Said reaction is advantageously carried out in the presence of tπethylamine in an organic solvent Appiopπate solvents comprise DMF idimethylformamide) and DCM (dichloromethane).
When Rc comprises a -OH terminal group the reaction is followed by a chromatography on a Dowex type column Io recover the desired derivative
When Rc comprises a -NH
2 terminal group the resulting derivative is treated with TFA and DCM Said derivative, by reaction with RC=O) R" may be used to obtain derivatives of formula I with R1 = -(CH
2)
n - NH -C(=O)-R R and R ' being such as above defined
According to the invention, the derivatives of formula IV are obtained by reacting a derivative of formula Vl
wherein S=C=N- and - C(=0)-0R are on carbon adjacent positions on Ar and R is such as above defined with an amino derivative of formula VII
with R1 being such as above defined
Said reaction is advantageously carried out in an alcoholic solvent and H^O. Preferably the alcoholic solvent is isopropanol
The compounds of the second and third families are obtained according to usual synthesis routes, advantageously using commercially available molecules as starting materials
Other characteristics and advantages are given in the following examples which refer to figures 1 to 8, wherein
- Figure 1: Illustrates in silico molecular docking to find new ANT-ligands
(A) Structure of the carboxyatractyloside ι CAT)-bovιne ANT1 complex (adapted from (26))
(B) Prediction by computer analysis of the carboxyatractyloside (CAT) localization in the human ANT2 binding
- Figure 2: The ANT-ligand is pro-apoptotic on HT-29 and BxPC3 tumor cell lines
(A) Chemical structure of compound 1
(B) Multiparametric analysis (chromatin condensation, mitochondrial transmembrane potential
loss plasma membrane peπneabilization, phosphatidylseπne exposure) of cellular effects of the ANT-ligand on BxPC3 cell line after 48h treatment.
(C) Effects of compound 1 on ADP/ATP translocator activity of ANT measured on isolated mitochondria from mice liver or HT-29 tumor cell line (IC50 is given in μM based on ANT assays) and on viability of HT-29 and BxPC3 tumor cell lines (LD50 is given in μM based on MTT assays at 48h),
- Figure 3: Compound 1 induced-cell death is caspase-dependent
Compound 1 induces classical hallmarks of apoptosis mitochondrial potential iΛΨm) loss (Diocβ-), phosphatidylserine exposure (Annexιn-V+), plasma membrane permeabilization (Pl+) and chromatin condensation as shown by multiparametric 5 analysis Apoptosis induced by the ANT-ligand is inhibited by pan-caspase inhibitors
(z-VAD-fmk, Q-VD-OPH) but not by the cathepsin B inhibitor (Z-FA-fink)
- Figure 4: Compound 1 induces low toxicity on normal fibroblast Wi-38
(A) Expression pattern of ANT isoforms in HT-29, BxPCo and Wi-38 (normal lung I O fibroblasts) cell lines after RT-PCR reaction on total RNA
(B) Multiparametric analysis (mitochondrial transmembrane potential, plasma membrane permeabilization, phosphatidylserine exposure) of cellular effects of the ANT-ligand on Wi-38 cell line after 48h and 72h treatments.
15 - Figure 5: Target validation of compound 1 using ANT-deficient yeasts
(A) Quantitative estimation of yeasts viability at 48h after 2h incubation with compound 1
(B) Illustration of WT (W303ι and JL1-3 (ΛANT1 , 2 and 2) yeast strains growth on plates at 48h after 2h incubation with compound 1. 0
- Figure 6: Optimization by structure-Activity Relationship studies
The table shows the effects of optimized compounds on HT-29, BxPC3, MiaFaca, Wi- 38 cell viability (LD50 in μM); on ANT activity in mice liver and HT-29 tumor cell line mitochondria (IC50 in μM); on swelling (DS50 in μM) and Λψm parameters < DP50 in 5 μM) in mice liver mitochondria (Mitotrust™ platform), and on viability of wild-type
(W303) and ANT-deficient (JL1 -3) yeasts strains (ED50 in μM,ι.
- Figure 7: Chemical structures of optimized compounds in structural family 1. 0 - Figure 8: Effects of compounds (family 2 & 3| on cell lines and isolated mitochondria
The table shows the effects of compounds on HT-29, BxPC3, MiaPaca, Wι-38 cell viability (LD50 in μM); on ANT activity in mice and HT-29 tumor cell line mitochondria (EC50 in μM); on swelling (DS50 in μM) and ΛΨrn parameters (DP50 in μM) in mice liver mitochondria
ADP/ATP translocase activity assay
The ANT activity assay is an indirect measure of ATP translocation from isolated mitochondria in exchange of ADP followed by NADPH formation in the medium. This assay is using a complex system of ATP detection constituted of enzymes (hexokmase, glucose-6- phosphate-dehydrogenase), a substrate (glucose) and a co-substrate (NADP*; allowing
NADP+ reduction in MADPH The method is adapted from (10ι, with modifications: reactions in microplates, no pre-loading of mitochondria with ATP1 detection of NADP+ reduction by fluorescence (Spectrofluorimeter Infinite M200, Tecan), incorporation of AP5A ιP1 P5- diadenosineo'-pentaphosphate) to inhibit the adenylate kinase-dεpendent ATP synthesis (IC50 dose inducing 50% of carboxyatractyloside inhibition activity)
Viability assay and characterisation of cell death
MTT assay was used to evaluate the viability of a large range of human cell lines in presence of small molecules. Dose-response experiments allow us to determine a lethal-dose 50 iLD60; dose killing 50% of the cellular population) for each compound on a particular cell type after a 43-hour incubation. This viability assay is used as a first screening assay to identif/ cell-permeant molecules able to induce cell death (cytotoxic) or growth delay (cytostatic* among the 956 molecules of the ANT-ligands library. We have chosen to select molecules having an LD£0 below 50 μM on HT-29 (colon adenocarcinoma i or BxPC3 (pancreatic adenocarcinoma) cell lines These molecules corne into the ANT activity screening assays and the efficient ANT-inhibitors (IC50 below 50 μM) are investigated for their mechanisms of cell death induction, Indeed, the characterisation of cell death consists in a multipaiametric analysis of tieated-cells by flow cytometry i FacsCalibur, Becton Dickinson) where can be measured < 1) the loss of mitochondrial trans-membrane potential (ΛΨm; DIOC6 labelling), (2) the plasma membrane permeabilization (Propidium Iodide labeling) and ι3) the phosphatidylserines exposure (Annexin-V-fitc labelling).
Scheme of synthesis of compounds 1 -6 and 8-16
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