Discovery of 9-(6-aminopyridin-3-yl)-1-(3-(trifluoromethyl)phenyl)benzo[h][1,6]naphthyridin-2(1H)-one (Torin2) as a potent, selective and orally available mTOR inhibitor for treatment of cancer

Abstract

The mTOR mediated PI3K/AKT/mTOR signal transduction pathway has been demonstrated to play a key role in a broad spectrum of cancers. Starting from the mTOR selective inhibitor 1 (Torin1), a focused medicinal chemistry effort led to the discovery of an improved mTOR inhibitor 3 (Torin2), which possesses an EC₅₀ of 0.25 nM for inhibiting cellular mTOR activity. Compound 3 exhibited 800-fold selectivity over PI3K (EC₅₀: 200 nM) and over 100-fold binding selectivity relative to 440 other protein kinases. Compound 3 has significantly improved bioavailability (54%), metabolic stability and plasma exposure relative to compound 1.

Introduction

The Mammalian Target of Rapamycin (mTOR) is a highly conserved serine/threonine protein kinase and is a key element in the PI3K/AKT/mTOR signal pathway.¹ Upon activation by extra cellular inputs such as insulin, energy stress, growth factors and nutrients, mTOR regulates a variety of fundamental cellular processes such as proliferation, growth and metabolism.^2,3 mTOR is a member of PIKK kinase family, which also includes PI3K, ATR, ATM, DNA-PK and SMG-1. Structurally their catalytic domains all share high sequence identity to the PI3K kinase but differ significantly in sequence and secondary structure from the protein kinases.⁴ In cells mTOR exists in at least two functionally distinct protein complexes, mTORC1 and mTORC2. The mTORC1 complex is composed of Raptor, LST8, PRAS40 and Deptor and is responsible for regulated protein synthesis through phosphorylation of S6K1 and 4E-BP1. The mTORC2 complex consists of Rictor, LST8, SIN1, Deptor and Protor and regulates cell proliferation and survival through phosphorylation of Akt/PKB.⁵ The PI3K/Akt/mTOR signal transduction pathway is frequently deregulated in human cancers and thereby has attracted considerable attention as an oncology drug discovery target.^6,7,8,9

Successful development of rapalogs (rapamycin and related analogs) as treatments of specific cancers has provided clinical validation of mTOR as an anti-cancer drug discovery target.¹⁰ However, existing rapalogs do not fully inhibit mTORC1 and are unable to acutely inhibit mTORC2.^11,12 In addition, a negative feedback loop exists through S6K/IRS1/PI3K that results in pathway activation upon inhibition of mTORC1 by rapamycin which may also serve to limit the efficacy of the rapalogs.¹³ There is currently great interest in clinically testing the hypothesis that ATP-competitive mTOR inhibitors will exhibit more broad-based and profound anti-tumor activity relative to the rapalogs. In the recent years there has been a significant investment in developing potent and selective mTOR inhibitors which has resulted in compounds such as 2-(4-amino-1-isopropyl-1H-pyrazolo[3,4-d]pyrimidin-3-yl)-1H-indol-5-ol(PP242),¹⁴ (5-(2-((2R,6S)-2,6-dimethylmorpholino)-4-morpholinopyrido[2,3-d]pyrimidin-7-yl)-2-methoxyphenyl)methanol(KU63794),¹⁵ (5-(2,4-bis((S)-3-methylmorpholino)pyrido[2,3-d]pyrimidin-7-yl)-2-methoxyphenyl)methanol (AZD8055),¹⁶ methyl 4-(1-(1-(methoxycarbonyl)piperidin-4-yl)-4-morpholino-1H-pyrazolo[3,4-d]pyrimidin-6-yl)phenylcarbamate (WYE-354),¹⁷ (1s,4s)-4-(4-amino-5-(7-methoxy-1H-indol-2-yl)imidazo[1,5-f][1,2,4]triazin-7-yl)cyclohexanecarboxylic acid (OSI-027),¹⁸ 1-(4-(8-oxa-3-azabicyclo[3.2.1]octan-3-yl)-1-(1,4-dioxaspiro[4.5]decan-8-yl)-1H-pyrazolo[3,4-d]pyrimidin-6-yl)-3-methylurea (WYE-125132),¹⁹ (E)-4-((2-(4,6-dimorpholino-1,3,5-triazin-2-yl)hydrazono)methyl)-2,6-dimethoxyphenol (KU-BMCL-200908069-1),²⁰ 1-(4-(4-(8-oxa-3-aza-bicyclo[3.2.1]octan-3-yl)-1-(2,2,2-trifluoroethyl)-1H-pyrazolo[3,4-d]pyrimidin-6-yl)phenyl)-3-(4-(4-methylpiperazin-1-yl)phenyl)urea (Wyeth-BMCL-200910096-27),²¹ and compound 1. ²²

Compound 1 is a highly potent and selective mTOR inhibitor that exhibits the ability to inhibit mTOR in vivo. However the low yielding synthetic route, poor water solubility, short half-life (T1/2), and low oral bioavailability limits the use of 1 as a pharmacological tool in vivo. In order to address some of these deficiencies we initiated a medicinal chemistry campaign that resulted in the identification of a highly potent and selective mTOR inhibitor 3 (Torin2), which is easier to produce on scale and exhibits improved pharmacokinetic properties which should enable it use in vivo experiments.

Results and discussion

Compound 1 exhibits very rapid metabolism upon incubation with mouse and human hepatocytes (T_1/2 of 4 min) which suggests that the compound may be subject to rapid first-pass metabolism in the liver. Consistent with this finding, the observed half-life following intravenous delivery of 1 to mice was 30 minutes. Oral administration of 1 revealed that the compound possessed very limited oral bioavailability. We reasoned that if we could reduce the molecular weight of 1, we might remove sites of metabolism and also obtain a more water soluble compound. Replacement of the propionyl-piperazine moiety of 1 with a fluorine yielded compound 2 which maintained potent cellular mTOR (EC₅₀: 25 nM) inhibitory activity and selectivity versus PI3K (EC₅₀: >1250 nM). The isolated mouse microsome stability of compound was significantly improved compared to 1 (T_1/2 of 17.7 min) (Table 1). This result encouraged us to prepare a focused series of analogs with replacements to the quinoline moiety which ultimately resulted in the identification of 3 (Figure 1).

Table 1.

Pharmacological characterization of compound 1 and 2.^a

Entry	mTORC1 IC50(nM)	mTOR EC50(nM)	PI3K EC50(nM)	Mouse microsome stability T1/2(min)
1	0.29	2	1800	4
2	37.1	25	>1250	17.7

^aDeterminations are the mean of two of independent measurements with standard error of <20%,

Figure 1. Representative structure of library.

The targeted library was generated using a four-step synthetic sequence which commenced from 4-chloro-6-bromo-quinoline compound 4. A nucleophilic substitution with appropriate anilines provided general intermediates 5, which was subsequently subjected to NaBH₄ reduction to afford the alcohol compounds 6. Benzylic alcohol oxidation with MnO₂ followed by Horner-Wadsworth-Emmons olefination furnished the tricyclic core scaffold 7. Finally variation of the Ar₂ position was achieved using palladium mediated coupling reactions to afford the target compounds 8.

Reagents and conditions: 1. Appropriate aniline, 1,4-dioxane, 90°C, 4-12 h; 2. NaBH₄, EtOH, rt, 2-4 h; 3. a) MnO₂, CH₂Cl₂, rt, 2-6 h, b) triethyl phosphonoacetate, K₂CO₃, EtOH, 100 °C, 12h; 4. Ar₂B(OH)₂, PdCl₂(Ph₃P)₂, Na₂CO₃, 1,4-dioxane, 80 °C, 4-12 h.

By variation the substitutions of the Ar₁ and Ar₂ groups, a focused library was generated (Figure 1) and the biological characterizations are summarized in table 2.

Table 2.

Enzymatic and cellular activities of compounds 3,9-31^a

Entry	R1 (para)	R2 (meta)	R3 (ortho)	Ar2	mTORC1 IC50(nM)	mTOR EC50(nM)	PI3K EC50(nM)
9	F	CF3	H		4.6	10	>1250
10	F	CF3	H		69.3	50	1000
11	F	CF3	H		2.9	1	250
12	F	CF3	H		16.4	1	500
13	F	CF3	H		76.0	25	500
14	F	CF3	H		15.2	1	750
15	F	CH3	H		35.5	10	1000
16	F	CH3	H		7.0	10	>1250
17	F	CH3	H		59.5	50	1000
18	F	CH3	H		77.8	20	1000
19	F	CH3	H		303	20	>1250
20	F	CH3	H		43.0	10	>1250
21	F	CH3	H		2.2	2	250
22	F	Cl	H		26.7	10	500
23	F	Cl	H		79.2	50	1000
24	F	Cl	H		1.4	1	750
25	F	Cl	H		2.5	1	750
26	F	Cl	H		24.4	2	250
27	F	F	H		18.9	5	750
28	F	F	H		84.4	100	1000
29	F	H	CF3		4.8	25	>1250
30	F	H	CF3		107.5	250	1250
31	F	H	CF3		19.2	35	1250
3	H	CF3	H		2.1	0.25	200

^athe IC₅₀ determinations are the mean of two of independent measurement with standard error of <20%,

Substitution of the acyl piperazine ring with fluoro at the R₁ position (compound 2) resulted in a 10-fold loss of potency in cellular mTOR assays. Replacement of the quinoline side chain at the Ar₂ position with pyrazole (9) and methyl pyrazole (10) resulted in 5-25-fold reduction in activity. Replacement of the quinoline of 2 with aminopyridine (11), aminopyrimidine (12) and 7-azo-indole (14) groups resulted in compounds with potent mTOR inhibitory activity. However compounds 11 and related analogs demonstrated higher PI3K inhibitory activity. Indazole replacement (13) resulted in 10-fold loss of potency relative to 14 indicating that a beta nitrogen was required for the activity potentially suggesting a hydrogen-bond accepting moiety is required at this position. A similar activity trend was observed when CF₃ was substituted with CH₃ (15-21) at the R₂ position. 7-azo-indole analog (21) possessed the most potent mTOR inhibitory activity but also exhibited significant activity against PI3K. Replacement of CF₃ with smaller groups such as Cl (22-26) and F (27,28) resulted in compounds with similar potency against mTOR and PI3K. 7-aza-indole analog (24) and aminopyrimidine analog (25) exhibited the best potency as inhibitors of mTOR while still possessing more than 500 fold selectivity relative to PI3K. Introduction of the CF₃ group at R₃ position (29-31) resulted in a 20-100 fold loss of activity against mTOR suggesting either steric impediments to substitution at this position or unfavorable effects on the conformation of the compound. Removal of F from the R₁ position while maintaining the aminopyridine side chain (3) resulted in the best balance of highly potent inhibition of mTOR(EC₅₀ 0.25 nM) while maintaining 800-fold selectivity relative to PI3K (EC₅₀ 200 nM).

We attempted to rationalize the observed structure-activity relationship (SAR) by docking compound 3 into a homology model of mTOR built using a PI3Kγ crystal structure (PDB code 3DBS) (Figure 2A). Similar to 1,²² compound 3 is predicted to engage in a ‘hinge’ hydrogen bond with V2240 using the quinoline nitrogen as well as engage a second hydrogen bond between Y2225 and pyridine nitrogen inside inner hydrophobic pocket. In addition, two hydrogen bonds are predicted to exist between the aniline amino group of 3 with D2195 and D2357 in the inner hydrophobic pocket and this may provide an explanation for the approximate 10-fold potency increase in mTOR inhibition compared to 1. The same binding mode was observed in PI3Kγ modeling study with compound 3. V882 served as a hinge binding point and in the inner hydrophobic pocket Y867, D841 and D964 provided three more hydrogen bonds with aminopyridine side chain analogous to Y2225, D2195 and D2357 of mTOR. This may provide a rationale for why compound 3 begins to inhibit PI3K. (Figure 2B)

Figure 2.

Model of 3 (green sticks) docked into a homology model of mTOR (grey ribbons) (A) and PI3Kγ (PDB 3DBS) (grey ribbons) (B). Potential hydrogen bonds are shown with hatched red lines.

Pharmacodynamics and Pharmacokinetics

In order to determine which compounds might be optimal for use in murine tumor studies, we selected a set of compounds based on the mTOR activity, selectivity over PI3K, synthetic feasibility and structural diversity. First the compounds were evaluated for their stability when incubated in the presence of isolated mouse liver microsomes. A subset of compounds were then advanced into pharmacodynamic (PD) studies monitoring the phosphorylation status of S6K T389 and Akt T308 in the lung and liver by western blot six hours after oral administration. The pharmacodynamic response was approximately scored with 1 being assigned a “+++” score (“++++” indicates over 95%, “+++” indicates 80-95%, “++” indicates 60-80 % and “+” indicates 40-60 % inhibition of pS6K and pAkt compared to vehicle). The results are summarized in table 3. Compounds 3, 9, 14, 16 and 17 exhibited similar or better pharmacodynamic effects relative to 1 while compounds 2, 15, 23 and 24 were less effective than 1. Compounds 19, 21, 25, 26, 27 and 28 did not exhibit inhibition of the S6K or Akt phosphorylation after 6 hours. The liver microsome stability results varied significantly amongst the compounds. Compounds 2, 3, 19, 25, 26 and 27 all exhibited more than a 10 min half-life but this did not predict which compounds would exhibit a robust pharmacodynamic effect. Several compounds such as 19, 25, 26 and 27 exhibited poor pharmacodynamics despite having superior microsome stability relative to 1 while other very short-lived compounds such as 9, 14, 16 and 17 exhibited more sustained pharmacodynamics. The basis for this discrepancy is currently unknown but may result from a sustained mTOR inhibition due to a slow off-rate from the kinase for some compounds. The oral PD studies employed a different formulation (10%NMP, 40% PEG in water) relative to the oral PK studies (0.5% w/v Na CMC with 0.1% w/v Tween-80) so the degree of drug exposure in the PD studies can not be directly extrapolated from the PK studies.

Table 3.

Pharmacodynamics and liver microsome stability of selected compounds.

Entry	Structure	PD	T1/2(min)	PI3K/mTOR (Selectivity fold)
2		++	11.7	50
3		++++	11.7	800
9		+++	4.2	125
14		++++	1.5	750
15		++	3.3	100
16		++++	3.2	83
17		++++	2.7	20
19		None	14.4	62.5
21		None	1.8	125
23		++	3.7	20
24		++	2.1	750
25		None	20.6	750
26		None	14.5	500
27		None	22.9	150
28		None	4.5	10

Compounds that exhibited the best pharmacodynamic properties were subject to pharmacokinetic evaluation in mice following intravenous and oral administration (Table 4). As has been predicted by the mouse liver microsome stability study, all compounds exhibited a half-life of less than 2 hours when dosed to male Swiss albino mice. Compound 3 exhibited the best bioavailability (51%) and overall exposure despite possessing a short half-life and was selected for further evaluation. Compared to compound 1, the bioavailability of 3 was improved by approximately 10-fold.²² Most of the compounds exhibited rapid absorption following oral administration to mice. All the compounds studied had low to moderate clearance and exhibited volumes of distribution close to the total body water. The possible reasons for the low bioavailability for the majority of the compounds could be poor absorption which may be due to the limited water solubility of the compounds.

Table 4.

PK properties of selected compounds.^a

Entry	Cmax (ng/mL) I.V./P.O.	Tmax (h) PO	AUC (h*ng/mL) I.V./P.O.	T1/2 (h) I.V.	CL (mL/min/Kg) I.V.	Vss (L/Kg) I.V.	F (%) P.O.
3	1540/3968	0.25	850/4311	0.72	19.6	1.0	51
9	426/430	0.5	391/755	0.63	42.6	2.42	19.2
14	1639/98	1.0	803/352	1.09	20.8	1.30	4.2
16	1035/853	0.5	1110/2410	1.46	15.0	1.16	21.6
17	-/1039	0.5	728/2068	0.99/1.31	22.9	1.08	28

^aC57BL/6 male mouse was dosed at 1 mg/kg for the intravenous (IV), 10 mg/kg for the oral (PO).

Kinase Selectivity profiling

To characterize the kinase selectivity of 3 we profiled its ability to bind to a panel of 440 kinases using the Ambit KinomeScan™ technology²³ (Table 5). Compound 3 exhibited excellent overall selectivity (S(5) score(1 μM) = 0.02)²⁴ and has strong binding to mTOR(4.6), CSNK1E(2.7), several PI3Ks(0-3.5), CSF1R(2.4) and MKNK2(0.9). Compound 3 was subject to further profiling against a panel of lipid kinases using the Invitrogen SelectScreen® technology which exhibited potent biochemical inhibition of PI3Ks and DNA-PK in addition to mTOR (Table 6). From our cellular PI3K assays we know there is approximately at 40-fold discrepancy between the biochemical PI3K IC₅₀ and the cellular EC₅₀. It remains to be determined whether DNA-PK is inhibited by 3 in cellular assays. It is interesting to note that the enzymatic selectivity ratio for inhibition of mTor versus PI3K for both 3 (enzyme ratio = 2) and Torin1 (enzyme ratio =60)²² substantially underestimates the observed ratio for cellular inhibition of these targets: 3 (cell ratio = 800) and Torin1 (cell ratio = 900).

Table 5.

Kinome Scan™ profile of 3^a

Kinase	% control	Kinase	% control
mTOR	4.6	CSF1R	2.4
CSNK1E	2.7	MKNK2	0.9
PIK3C2G	3.5	PIK3CA	0.55
PIK3CA(C420R)	0.1	PIK3CA(E542K)	0.25
PIK3CA(E545K)	0.25	PIK3CA(H1047L)	0
PIK3CA(H1047Y))	1.4	PIK3CA(I800L)	0
PIK3CA(M1043I)	1	PIK3CA(Q546K)	0.35
PIK3CG	0.2	PIK4CB	1.7

^aCompound 3 was profiled at a concentration of 1 μM against a diverse panel of 442 kinases by Ambit Biosciences

Table 6.

LanthaScreen™ profile of 3 using the invitrogen lipid kinase panel^a

Kinase	IC50(nM)	Kinase	IC50(nM)
PI4K α	>10000	P110 α/p85α	4.68
PI4K β	18.3	P110δ/P85α	17.5
PI3K-C2 α	28.1	P110γ	5.67
PI3K-C2β	24.5	DNA-PK	0.5
hVPS34	8.58	mTOR	2.81

^aKinase targets were tested with biochemical enzymatic kinase assays using the SelectScreen^® Kinase Profiling Service (Life Technologies Corporation, Madison, WI)

Conclusion

Starting from the selective mTOR inhibitor 1, we used a focused medicinal chemistry approach guided by cellular assays and pharmacokinetic and pharmacodynamic assays to develop 3 which possesses properties that make it more suitable for use in murine tumor studies. Compound 3 possesses a 250 pM EC₅₀ for inhibiting mTOR in cells while maintaining 800-fold cellular selectivity relative to inhibition of PI3K and most other protein kinases. Compound 3 exhibits good bioavailability and exposure and can maintain strong inhibition of mTOR activity in lung and liver to at least six hours after a single dose of 20 mg/kg. Compound 3 is a useful pharmacological tool for further exploring the therapeutic potential of mTOR inhibitors for the treatment of cancer.

Experimental Procedures

Chemistry

All solvents and reagents were used as obtained. ¹H NMR spectra were recorded with a Varian Inova 600 NMR spectrometer and referenced to dimethyl sulfoxide. Chemical shifts are expressed in ppm. In the NMR tabulation, s indicates singlet; d, doublet; t, triplet; q, quartet; m, multiplet; and br, broad peak. Mass spectra were measured with Waters Micromass ZQ using an ESI source coupled to a Waters 2525 HPLC system operating in reverse mode with an Waters Sunfire™ C18 5μm 4.6×50 mm column. Purification of compounds was performed with either a Teledyne ISCO combiflash Rf system or a Waters Micromass ZQ preparative system. The purity of all compounds was ≥95%. The purity was analyzed on an above mentioned Waters LC-MS Symmetry (C18 column, 4.6 × 50 mm, 5μM) using a gradient of 5-95% acetonitrile in water containing 0.05% trifluoacetic acid (TFA) over 8 min (10 min run time) at a flow rate of 2 mL/min.

General procedure for the preparation of compounds

To a solution of compound 4 (ethyl 6-bromo-4-chloroquinoline-3-carboxylate, 1 eq.) in 1,4-dioxane at room temperature in a sealed tube was added aniline (1 eq.). The resultant solution was heated to 90 °C for 4-12 h. After cooled down to room temperature, a solution of NaOH (1 N) was added to neutralize the solution followed by dilution with water and extraction with ethyl acetate. After drying with Na₂SO₄, the solvents were removed and the residue was purified by ISCO (Hexanes: EtOAc) to furnish compound 5.

To a solution of compound 5 (1 eq.) in EtOH at room temperature was added NaBH₄(10 eq.), the resultant solution was stirred at room temperature for 2-4 h before diluted with EtOAc and filtered through celite. The filtrate was concentrated under vacuum and the residue was dissolved in EtOAc and brine. After separation, the organic layer was dried over MgSO₄ and concentrated under vacuum. The residue was purified by ISCO (hexanes: EtOAc) to afford compound 6.

To a solution of compound 6 in CH₂Cl₂ (1 eq.) at room temperature was added MnO₂ (5 eq. mass). After 2-6 h, the reaction mixture was filtered through celite. The filtrate was concentrated in a sealed tube and dissolved in dry EtOH after which, K₂CO₃ (3 eq.) and triethyl phosphonoacetate were added. The resultant mixture was heated to 100 °C for 12h before cooling down to room temperature. Upon removal of the solvents under vacuum, the residue was diluted with water following by extraction with EtOAc. Purification of the residue by ISCO (hexanes: EtOAc) provided compound 7.

To a solution of compound 7 in 1,4-dioxane at room temperature was added subsequently PdCl₂(Ph₃P)₂ (0.1 eq.), Na₂CO₃(3 eq., 1 N) and boronic acids or pinacol boronate esters. After degassing, the resultant mixture was heated to 80 °C for 4-12 h before cooling down to room temperature and filtration through celite. Upon removal of the solvents, the residue was subjected to column purification (CH₂Cl₂: MeOH) to furnish the desired compounds 8.

Compound 3 was prepared following above procedures (15% overall yield). LC-MS: (M+H) 433.13. ¹H NMR (600 MHz, DMSO-d₆) δ 9.09 (s, 1H), 8.31 (d, J = 9.6 Hz, 1H), 8.11 (s, 1H), 8.03 (d, J = 9.0 Hz, 1H), 8.00 (d, J = 7.8 Hz, 1H), 7.92 (dd, J = 8.4, 1.8 Hz, 1H), 7.86 (dd, J = 8.4, 7.8 Hz, 1H), 7.78 (d, J = 8.4 Hz, 1H), 7.72 (d, J = 2.4 Hz, 1H), 7.04 (dd, J = 8.4, 2.4 Hz, 1H), 6.91 – 6.93 (m, 2H), 6.38 (d, J = 8.4 Hz, 1H), 6.18 (s, 2H).

Characterization of in vitro biochemical activity with the mTORC1 complex, mTOR and PI3K Cellular Assays, Ambit in vitro KinomeScan™ kinase selectivity profile and In vivo pharmacokinetic studies please see reference 22.

In vivo pharmacodynamic studies

Compound 3 powder was first dissolved at 25 mg/mL in 100% N-methyl-2-pyrrolidone and then diluted 1:4 with sterile 50% PEG400 prior to injection. Six-week old male C57BL/6 mice were fasted overnight prior to drug treatment. The mice were treated with vehicle (for 10 h) or 3 (20 mg/kg for 6h) via oral gavage and then re-fed 1 h prior to sacrifice (CO₂ asphyxiation). Liver and lung were collected and frozen on dry ice. The frozen tissue was thawed on ice and lysed by sonication in tissue lysis buffer (50mM HEPES, pH 7.4, 40 mM NaCl, 2 mM EDTA, 1.5 mM sodium orthovanadate, 50mM sodium fluoride, 10 mM sodium pyrophosphate, 10 mM sodium β-glycerophosphate, 0.1% SDS, 1.0% sodium deoxycholate, and 1.0% Triton, supplemented with protease inhibitor cocktail tablets (Roche)). The concentration of clear lysate was measured using the Bradford assay and samples were subsequently normalized by protein content and analyzed by SDS-PAGE and immunoblotting.

Molecular modeling

Compound 3 was docked into an mTOR homology model built from a published PI3Kγ crystal structure complexed with GDC-0941 (PDB: 3DBS) using AutoDock vina.^22,25

Scheme 1.

Discovery of 3 starting from 1

Scheme 2.

Chemical synthesis of a focused library.

Abbreviations

mTOR

mammalian Target of Rapamycin

Akt

v-akt murine thymoma viral oncogene homolog 1

ATP

adenosine triphosphate

PIKK

PI3K related kinases

DNA-PK

DNA activated protein kinase

ATM

Ataxia Telangiectasia mutated kinase

ATR

Ataxia Telangiectasia and Rad-3-related kinase

SMG-1

Serine/threonine protine kinase -1

4E-BP1

Eukaryotic translation initiation factor 4E-binding protein 1

PK

Pharmacokinetics