Pharmacokinetics-Pharmacodynamics of Enmetazobactam Combined with Cefepime in a Neutropenic Murine Thigh Infection Model.

Third-generation cephalosporin (3GC)-resistant Enterobacteriaceae are classified as critical priority pathogens, with extended-spectrum ß-lactamases (ESBLs) as principal resistance determinants. Enmetazobactam (formerly AAI101) is a novel ESBL inhibitor developed in combination with cefepime for empirical treatment of serious Gram-negative infections in settings where ESBLs are prevalent. Cefepime-enmetazobactam has been investigated in a phase 3 trial in patients with complicated urinary tract infections or acute pyelonephritis. This study examined pharmacokinetic-pharmacodynamic (PK-PD) relationships of enmetazobactam, in combination with cefepime, for ESBL-producing isolates of Klebsiella pneumoniae in 26-h murine neutropenic thigh infection models. Enmetazobactam dose fractionation identified the time above a free threshold concentration (fT > CT ) as the PK-PD index predictive of efficacy. Nine ESBL-producing isolates of K. pneumoniae, resistant to cefepime and piperacillin-tazobactam, were included in enmetazobactam dose-ranging studies. The isolates encoded CTX-M-type, SHV-12, DHA-1, and OXA-48 ß-lactamases and covered a cefepime-enmetazobactam MIC range from 0.06 to 2 µg/ml. Enmetazobactam restored the efficacy of cefepime against all isolates tested. Sigmoid curve fitting across the combined set of isolates identified enmetazobactam PK-PD targets for stasis and for a 1-log10 bioburden reduction of 8% and 44% fT > 2 µg/ml, respectively, with a concomitant cefepime PK-PD target of 40 to 60% fT > cefepime-enmetazobactam MIC. These findings support clinical dose selection and breakpoint setting for cefepime-enmetazobactam.

pRAD50: a novel and clinically applicable pharmacodynamic biomarker of both ATM and ATR inhibition identified using mass spectrometry and immunohistochemistry.

BACKGROUND: AZD0156 and AZD6738 are potent and selective inhibitors of ataxia-telangiectasia-kinase (ATM) and ataxia-telangiectasia-mutated and Rad3-related (ATR), respectively, important sensors/signallers of DNA damage. METHODS: We used multiplexed targeted-mass-spectrometry to select pRAD50(Ser635) as a pharmacodynamic biomarker for AZD0156-mediated ATM inhibition from a panel of 45 peptides, then developed and tested a clinically applicable immunohistochemistry assay for pRAD50(Ser635) detection in FFPE tissue. RESULTS: We found moderate pRAD50 baseline levels across cancer indications. pRAD50 was detectable in 100% gastric cancers (n = 23), 99% colorectal cancers (n = 102), 95% triple-negative-breast cancers (TNBC) (n = 40) and 87.5% glioblastoma-multiformes (n = 16). We demonstrated AZD0156 target inhibition in TNBC patient-derived xenograft models; where AZD0156 monotherapy or post olaparib treatment, resulted in a 34-72% reduction in pRAD50. Similar inhibition of pRAD50 (68%) was observed following ATM inhibitor treatment post irinotecan in a colorectal cancer xenograft model. ATR inhibition, using AZD6738, increased pRAD50 in the ATM-proficient models whilst in ATM-deficient models the opposite was observed, suggesting pRAD50 pharmacodynamics post ATR inhibition may be ATM-dependent and could be useful to determine ATM functionality in patients treated with ATR inhibitors. CONCLUSION: Together these data support clinical utilisation of pRAD50 as a biomarker of AZD0156 and AZD6738 pharmacology to elucidate clinical pharmacokinetic/pharmacodynamic relationships, thereby informing recommended Phase 2 dose/schedule.

Global metabolite profiling of human colorectal cancer xenografts in mice using HPLC-MS/MS.

Reversed-phase gradient LC-MS was used to perform untargeted metabonomic analysis on extracts of human colorectal cancer (CRC) cell lines (COLO 205, HT-29, HCT 116 and SW620) subcutaneously implanted into age-matched athymic nude male mice to study small molecule metabolic profiles and examine possible correlations with human cancer biopsies. Following high mass accuracy data analysis using MS and MS/MS, metabolites were identified by searching against major metabolite databases including METLIN, MASSBANK, The Human Metabolome Database, PubChem, Biospider, LipidMaps and KEGG. HT-29 and COLO 205 tumor xenografts showed a distribution of metabolites that differed from SW620 and HCT 116 xenografts (predominantly on the basis of relative differences in the amounts of amino acids and lipids detected). This finding is consistent with NMR-based analysis of human colorectal tissue, where the metabolite profiles of HT-29 tumors exhibit the greatest similarity to human rectal cancer tissue with respect to changes in the relative amounts of lipids and choline-containing compounds. As the metabolic signatures of cancer cells result from oncogene-directed metabolic reprogramming, the HT-29 xenografts in mice may prove to be a useful model to further study the tumor microenvironment and cancer biology.

ATR Inhibitor AZD6738 (Ceralasertib) Exerts Antitumor Activity as a Monotherapy and in Combination with Chemotherapy and the PARP Inhibitor Olaparib.

AZD6738 (ceralasertib) is a potent and selective orally bioavailable inhibitor of ataxia telangiectasia and Rad3-related (ATR) kinase. ATR is activated in response to stalled DNA replication forks to promote G2-M cell-cycle checkpoints and fork restart. Here, we found AZD6738 modulated CHK1 phosphorylation and induced ATM-dependent signaling (pRAD50) and the DNA damage marker γH2AX. AZD6738 inhibited break-induced replication and homologous recombination repair. In vitro sensitivity to AZD6738 was elevated in, but not exclusive to, cells with defects in the ATM pathway or that harbor putative drivers of replication stress such as CCNE1 amplification. This translated to in vivo antitumor activity, with tumor control requiring continuous dosing and free plasma exposures, which correlated with induction of pCHK1, pRAD50, and γH2AX. AZD6738 showed combinatorial efficacy with agents associated with replication fork stalling and collapse such as carboplatin and irinotecan and the PARP inhibitor olaparib. These combinations required optimization of dose and schedules in vivo and showed superior antitumor activity at lower doses compared with that required for monotherapy. Tumor regressions required at least 2 days of daily dosing of AZD6738 concurrent with carboplatin, while twice daily dosing was required following irinotecan. In a BRCA2-mutant patient-derived triple-negative breast cancer (TNBC) xenograft model, complete tumor regression was achieved with 3 to5 days of daily AZD6738 per week concurrent with olaparib. Increasing olaparib dosage or AZD6738 dosing to twice daily allowed complete tumor regression even in a BRCA wild-type TNBC xenograft model. These preclinical data provide rationale for clinical evaluation of AZD6738 as a monotherapy or combinatorial agent. SIGNIFICANCE: This detailed preclinical investigation, including pharmacokinetics/pharmacodynamics and dose-schedule optimizations, of AZD6738/ceralasertib alone and in combination with chemotherapy or PARP inhibitors can inform ongoing clinical efforts to treat cancer with ATR inhibitors.

Ce(IV) complexes with donor-functionalized alkoxide ligands: improved precursors for chemical vapor deposition of CeO2.

Thin films of ceria (CeO(2)) have many applications, and their synthesis by liquid-injection MOCVD (metal-organic chemical vapor deposition) or ALD (atomic layer deposition) requires volatile precursor compounds. Here we report the synthesis of a series of homoleptic and heteroleptic Ce(IV) complexes with donor-functionalized alkoxide ligands mmp (1-methoxy-2-methylpropan-2-olate), dmap (1-(dimethylamino)propan-2-olate), and dmop (2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)propan-2-olate) and their potential as precursors for MOCVD and ALD of CeO(2). New complexes were synthesized by alcohol exchange reactions with [Ce(OBu(t))(4)]. [Ce(mmp)(4)] and [Ce(dmap)(4)] were both found to be excellent precursors for liquid-injection MOCVD of CeO(2), depositing high purity thin films with very low carbon contamination, and both have a large temperature window for diffusion controlled growth (350-600 °C for [Ce(mmp)(4)]; 300-600 °C for [Ce(dmap)(4)]). [Ce(mmp)(4)] is also an excellent precursor for liquid-injection ALD of CeO(2) using H(2)O as oxygen source and demonstrates self-limiting growth from 150 to 350 °C. [Ce(dmap)(4)] has lower thermal stability than [Ce(mmp)(4)] and does not show self-limiting growth in ALD. Heteroleptic complexes show a tendency to undergo ligand redistribution reactions to form mixtures in solution and are unsuitable as precursors for liquid-injection CVD.

Discovery of Novel UDP-N-Acetylglucosamine Acyltransferase (LpxA) Inhibitors with Activity against Pseudomonas aeruginosa.

This study describes a novel series of UDP-N-acetylglucosamine acyltransferase (LpxA) inhibitors that was identified through affinity-mediated selection from a DNA-encoded compound library. The original hit was a selective inhibitor of Pseudomonas aeruginosa LpxA with no activity against Escherichia coli LpxA. The biochemical potency of the series was optimized through an X-ray crystallography-supported medicinal chemistry program, resulting in compounds with nanomolar activity against P. aeruginosa LpxA (best half-maximal inhibitory concentration (IC50) <5 nM) and cellular activity against P. aeruginosa (best minimal inhibitory concentration (MIC) of 4 µg/mL). Lack of activity against E. coli was maintained (IC50 > 20 µM and MIC > 128 µg/mL). The mode of action of analogues was confirmed through genetic analyses. As expected, compounds were active against multidrug-resistant isolates. Further optimization of pharmacokinetics is needed before efficacy studies in mouse infection models can be attempted. To our knowledge, this is the first reported LpxA inhibitor series with selective activity against P. aeruginosa.

Preclinical evaluation of M30 and M65 ELISAs as biomarkers of drug induced tumor cell death and antitumor activity.

M30 and M65 are ELISAs that detect different circulating forms of cytokeratin 18. Using the aurora kinase inhibitor AZD1152 and the SW620 human colon cancer xenograft, experiments were conducted to qualify preclinically both assays as serologic biomarkers of cell death. Using two different apoptotic markers, the kinetics of cell death induced by AZD1152 was first characterized in vitro in three different cell lines and shown to peak 5 to 7 days after drug addition. Treatment of non-tumor-bearing rats with AZD1152 (25 mg/kg) produced no alterations in circulating baseline values of M30 and M65 antigens. In treated, tumor-bearing animals, M30 detected a 2- to 3-fold (P < 0.05) increase in plasma antigen levels by day 5 compared with controls. This correlated to a 3-fold increase in the number of apoptotic cells detected on day 5 in SW620 xenografts using immunohistochemistry. By contrast, M65 did not detect a drug-induced increase in circulating antigen levels at day 5. However, M65 plasma levels correlated to changes in tumor growth in control animals (r(2) = 0.93; P < 0.01) and also followed the magnitude of the temporal effect of AZD1152 on tumor growth. An intermediate but active dose of AZD1152 (12.5 mg/kg) produced a less significant increase in M30 plasma levels at day 5. It was also confirmed that the plasma profiles of M30 and M65 mirrored closely those measured in whole tumor lysates. We conclude that M30 is a pharmacodynamic biomarker of AZD1152-induced apoptosis in the SW620 xenograft model, whereas M65 is a biomarker of therapeutic response.

Differential Activity of ATR and WEE1 Inhibitors in a Highly Sensitive Subpopulation of DLBCL Linked to Replication Stress.

DNA damage checkpoint kinases ATR and WEE1 are among key regulators of DNA damage response pathways protecting cells from replication stress, a hallmark of cancer that has potential to be exploited for therapeutic use. ATR and WEE1 inhibitors are in early clinical trials and success will require greater understanding of both their mechanism of action and biomarkers for patient selection. Here, we report selective antitumor activity of ATR and WEE1 inhibitors in a subset of non-germinal center B-cell (GCB) diffuse large B-cell lymphoma (DLBCL) cell lines, characterized by high MYC protein expression and CDKN2A/B deletion. Activity correlated with the induction of replication stress, indicated by increased origin firing and retardation of replication fork progression. However, ATR and WEE1 inhibitors caused different amounts of DNA damage and cell death in distinct phases of the cell cycle, underlying the increased potency observed with WEE1 inhibition. ATR inhibition caused DNA damage to manifest as 53BP1 nuclear bodies in daughter G1 cells leading to G1 arrest, whereas WEE1 inhibition caused DNA damage and arrest in S phase, leading to earlier onset apoptosis. In vivo xenograft DLBCL models confirmed differences in single-agent antitumor activity, but also showed potential for effective ATR inhibitor combinations. Importantly, insights into the different inhibitor mechanisms may guide differentiated clinical development strategies aimed at exploiting specific vulnerabilities of tumor cells while maximizing therapeutic index. Our data therefore highlight clinical development opportunities for both ATR and WEE1 inhibitors in non-GCB DLBCL subtypes that represent an area of unmet clinical need. SIGNIFICANCE: ATR and WEE1 inhibitors demonstrate effective antitumor activity in preclinical models of DLBCL associated with replication stress, but new mechanistic insights and biomarkers of response support a differentiated clinical development strategy.

Synthesis and SAR of 1-acetanilide-4-aminopyrazole-substituted quinazolines: selective inhibitors of Aurora B kinase with potent anti-tumor activity.

A new class of 1-acetanilide-4-aminopyrazole-substituted quinazoline Aurora kinase inhibitors has been discovered possessing highly potent cellular activity. Continuous infusion into athymic mice bearing SW620 tumors of the soluble phosphate derivative 2 led to dose-proportional exposure of the des-phosphate compound 8 with a high-unbound fraction. The combination of potent cell activity and high free-drug exposure led to pharmacodynamic changes in the tumor at low doses, indicative of Aurora B-kinase inhibition and a reduction in tumor volume.

AZD1152, a selective inhibitor of Aurora B kinase, inhibits human tumor xenograft growth by inducing apoptosis.

PURPOSE: In the current study, we examined the in vivo effects of AZD1152, a novel and specific inhibitor of Aurora kinase activity (with selectivity for Aurora B). EXPERIMENTAL DESIGN: The pharmacodynamic effects and efficacy of AZD1152 were determined in a panel of human tumor xenograft models. AZD1152 was dosed via several parenteral (s.c. osmotic mini-pump, i.p., and i.v.) routes. RESULTS: AZD1152 potently inhibited the growth of human colon, lung, and hematologic tumor xenografts (mean tumor growth inhibition range, 55% to > or =100%; P < 0.05) in immunodeficient mice. Detailed pharmacodynamic analysis in colorectal SW620 tumor-bearing athymic rats treated i.v. with AZD1152 revealed a temporal sequence of phenotypic events in tumors: transient suppression of histone H3 phosphorylation followed by accumulation of 4N DNA in cells (2.4-fold higher compared with controls) and then an increased proportion of polyploid cells (>4N DNA, 2.3-fold higher compared with controls). Histologic analysis showed aberrant cell division that was concurrent with an increase in apoptosis in AZD1152-treated tumors. Bone marrow analyses revealed transient myelosuppression with the drug that was fully reversible following cessation of AZD1152 treatment. CONCLUSIONS: These data suggest that selective targeting of Aurora B kinase may be a promising therapeutic approach for the treatment of a range of malignancies. In addition to the suppression of histone H3 phosphorylation, determination of tumor cell polyploidy and apoptosis may be useful biomarkers for this class of therapeutic agent. AZD1152 is currently in phase I trials.

Discovery and Characterization of AZD6738, a Potent Inhibitor of Ataxia Telangiectasia Mutated and Rad3 Related (ATR) Kinase with Application as an Anticancer Agent.

The kinase ataxia telangiectasia mutated and rad3 related (ATR) is a key regulator of the DNA-damage response and the apical kinase which orchestrates the cellular processes that repair stalled replication forks (replication stress) and associated DNA double-strand breaks. Inhibition of repair pathways mediated by ATR in a context where alternative pathways are less active is expected to aid clinical response by increasing replication stress. Here we describe the development of the clinical candidate 2 (AZD6738), a potent and selective sulfoximine morpholinopyrimidine ATR inhibitor with excellent preclinical physicochemical and pharmacokinetic (PK) characteristics. Compound 2 was developed improving aqueous solubility and eliminating CYP3A4 time-dependent inhibition starting from the earlier described inhibitor 1 (AZ20). The clinical candidate 2 has favorable human PK suitable for once or twice daily dosing and achieves biologically effective exposure at moderate doses. Compound 2 is currently being tested in multiple phase I/II trials as an anticancer agent.

Orally Bioavailable and Blood-Brain Barrier-Penetrating ATM Inhibitor (AZ32) Radiosensitizes Intracranial Gliomas in Mice.

Inhibition of ataxia-telangiectasia mutated (ATM) during radiotherapy of glioblastoma multiforme (GBM) may improve tumor control by short-circuiting the response to radiation-induced DNA damage. A major impediment for clinical implementation is that current inhibitors have limited central nervous system (CNS) bioavailability; thus, the goal was to identify ATM inhibitors (ATMi) with improved CNS penetration. Drug screens and refinement of lead compounds identified AZ31 and AZ32. The compounds were then tested in vivo for efficacy and impact on tumor and healthy brain. Both AZ31 and AZ32 blocked the DNA damage response and radiosensitized GBM cells in vitro AZ32, with enhanced blood-brain barrier (BBB) penetration, was highly efficient in vivo as radiosensitizer in syngeneic and human, orthotopic mouse glioma model compared with AZ31. Furthermore, human glioma cell lines expressing mutant p53 or having checkpoint-defective mutations were particularly sensitive to ATMi radiosensitization. The mechanism for this p53 effect involves a propensity to undergo mitotic catastrophe relative to cells with wild-type p53. In vivo, apoptosis was >6-fold higher in tumor relative to healthy brain after exposure to AZ32 and low-dose radiation. AZ32 is the first ATMi with oral bioavailability shown to radiosensitize glioma and improve survival in orthotopic mouse models. These findings support the development of a clinical-grade, BBB-penetrating ATMi for the treatment of GBM. Importantly, because many GBMs have defective p53 signaling, the use of an ATMi concurrent with standard radiotherapy is expected to be cancer-specific, increase the therapeutic ratio, and maintain full therapeutic effect at lower radiation doses. Mol Cancer Ther; 17(8); 1637-47. ©2018 AACR.

Discovery, synthesis, and in vivo activity of a new class of pyrazoloquinazolines as selective inhibitors of aurora B kinase.

The Aurora kinases have been the subject of considerable interest as targets for the development of new anticancer agents. While evidence suggests inhibition of Aurora B kinase gives rise to the more pronounced antiproliferative phenotype, the most clinically advanced agents reported to date typically inhibit both Aurora A and B. We have discovered a series of pyrazoloquinazolines, some of which show greater than 1000-fold selectivity for Aurora B over Aurora A kinase activity, in recombinant enzyme assays. These compounds have been designed for parenteral administration and achieve high levels of solubility by virtue of their ability to be delivered as readily activated phosphate derivatives. The prodrugs are comprehensively converted to the des-phosphate form in vivo, and the active species have advantageous pharmacokinetic properties and safety pharmacology profiles. The compounds display striking in vivo activity, and compound 5 (AZD1152) has been selected for clinical evaluation and is currently in phase 1 clinical trials.

Optimizing Therapeutic Effect of Aurora B Inhibition in Acute Myeloid Leukemia with AZD2811 Nanoparticles.

Barasertib (AZD1152), a highly potent and selective aurora kinase B inhibitor, gave promising clinical activity in elderly acute myeloid leukemia (AML) patients. However, clinical utility was limited by the requirement for a 7-day infusion. Here we assessed the potential of a nanoparticle formulation of the selective Aurora kinase B inhibitor AZD2811 (formerly known as AZD1152-hQPA) in preclinical models of AML. When administered to HL-60 tumor xenografts at a single dose between 25 and 98.7 mg/kg, AZD2811 nanoparticle treatment delivered profound inhibition of tumor growth, exceeding the activity of AZD1152. The improved antitumor activity was associated with increased phospho-histone H3 inhibition, polyploidy, and tumor cell apoptosis. Moreover, AZD2811 nanoparticles increased antitumor activity when combined with cytosine arabinoside. By modifying dose of AZD2811 nanoparticle, therapeutic benefit in a range of preclinical models was further optimized. At high-dose, antitumor activity was seen in a range of models including the MOLM-13 disseminated model. At these higher doses, a transient reduction in bone marrow cellularity was observed demonstrating the potential for the formulation to target residual disease in the bone marrow, a key consideration when treating AML. Collectively, these data establish that AZD2811 nanoparticles have activity in preclinical models of AML. Targeting Aurora B kinase with AZD2811 nanoparticles is a novel approach to deliver a cell-cycle inhibitor in AML, and have potential to improve on the clinical activity seen with cell-cycle agents in this disease. Mol Cancer Ther; 16(6); 1031-40. ©2017 AACR.

Discovery of novel and potent thiazoloquinazolines as selective Aurora A and B kinase inhibitors.

The synthesis of a novel series of quinazolines substituted at C4 by five-membered ring aminoheterocycles is reported. Their in vitro structure-activity relationships versus Aurora A and B serine-threonine kinases is discussed. Our results demonstrate that quinazolines with a substituted aminothiazole at C4 possess potent Aurora A and B inhibitory activity and excellent selectivity against a panel of various serine-threonine and tyrosine kinases, as exemplified by compound 46. We found also that the position and nature of the substituent on the thiazole play key roles in cellular potency. Compounds with an acetanilide substituent at C5' have the greatest cellular activity. The importance of the C5' position for substitution has been rationalized by ab initio molecular orbital calculations. Results show that the planar conformation with the sulfur of the thiazole next to the quinazoline N-3 is strongly favored over the other possible planar conformation. Compound 46 is a potent suppressor of the expression of phospho-histone H3 in tumor cells in vitro as well as in vivo, where 46, administered as its phosphate prodrug 54, suppresses the expression of phospho-histone H3 in subcutaneously implanted tumors in nude mice.

The PARP Inhibitor AZD2461 Provides Insights into the Role of PARP3 Inhibition for Both Synthetic Lethality and Tolerability with Chemotherapy in Preclinical Models.

The PARP inhibitor AZD2461 was developed as a next-generation agent following olaparib, the first PARP inhibitor approved for cancer therapy. In BRCA1-deficient mouse models, olaparib resistance predominantly involves overexpression of P-glycoprotein, so AZD2461 was developed as a poor substrate for drug transporters. Here we demonstrate the efficacy of this compound against olaparib-resistant tumors that overexpress P-glycoprotein. In addition, AZD2461 was better tolerated in combination with chemotherapy than olaparib in mice, which suggests that AZD2461 could have significant advantages over olaparib in the clinic. However, this superior toxicity profile did not extend to rats. Investigations of this difference revealed a differential PARP3 inhibitory activity for each compound and a higher level of PARP3 expression in bone marrow cells from mice as compared with rats and humans. Our findings have implications for the use of mouse models to assess bone marrow toxicity for DNA-damaging agents and inhibitors of the DNA damage response. Finally, structural modeling of the PARP3-active site with different PARP inhibitors also highlights the potential to develop compounds with different PARP family member specificity profiles for optimal antitumor activity and tolerability. Cancer Res; 76(20); 6084-94. ©2016 AACR.

Aurora kinase inhibitor nanoparticles target tumors with favorable therapeutic index in vivo.

Efforts to apply nanotechnology in cancer have focused almost exclusively on the delivery of cytotoxic drugs to improve therapeutic index. There has been little consideration of molecularly targeted agents, in particular kinase inhibitors, which can also present considerable therapeutic index limitations. We describe the development of Accurin polymeric nanoparticles that encapsulate the clinical candidate AZD2811, an Aurora B kinase inhibitor, using an ion pairing approach. Accurins increase biodistribution to tumor sites and provide extended release of encapsulated drug payloads. AZD2811 nanoparticles containing pharmaceutically acceptable organic acids as ion pairing agents displayed continuous drug release for more than 1 week in vitro and a corresponding extended pharmacodynamic reduction of tumor phosphorylated histone H3 levels in vivo for up to 96 hours after a single administration. A specific AZD2811 nanoparticle formulation profile showed accumulation and retention in tumors with minimal impact on bone marrow pathology, and resulted in lower toxicity and increased efficacy in multiple tumor models at half the dose intensity of AZD1152, a water-soluble prodrug of AZD2811. These studies demonstrate that AZD2811 can be formulated in nanoparticles using ion pairing agents to give improved efficacy and tolerability in preclinical models with less frequent dosing. Accurins specifically, and nanotechnology in general, can increase the therapeutic index of molecularly targeted agents, including kinase inhibitors targeting cell cycle and oncogenic signal transduction pathways, which have to date proved toxic in humans.

Examining changes in [18 F]FDG and [18 F]FLT uptake in U87-MG glioma xenografts as early response biomarkers to treatment with the dual mTOR1/2 inhibitor AZD8055.

PURPOSE: The mTOR kinase inhibitor AZD8055 inhibits both mTORC1 and mTORC2 leading to disruption of glucose metabolism and proliferation pathways. This study assessed the impact of single and multiple doses of AZD8055 on the uptake of the glucose metabolism marker 2-deoxy-2-[(18) F]fluoro-D-glucose ([(18) F]FDG) and the proliferation marker 3'-deoxy-3'-[(18) F]fluorothymidine ([(18) F]FLT) in U87-MG glioma xenografts. PROCEDURES: Mice bearing U87-MG tumours received either vehicle or AZD8055 (20 mg/kg) once daily p.o. Mice were imaged with either [(18) F]FDG or [(18) F]FLT PET to assess treatment response. Comparisons were made between in vivo imaging and ex vivo histopathology data. RESULTS: Tumour uptake of [(18) F]FDG was reduced by 33 % 1 h after a single dose of AZD8055 and by 49 % following 4 days of dosing. These changes coincided with suppression of the mTOR pathway biomarkers pS6 and pAKT. In contrast, the effect of AZD8055 on [(18) F]FLT uptake was inconsistent. CONCLUSIONS: The very rapid change in [(18) F]FDG uptake following acute AZD8055 treatment suggests that this could be used as an early mechanistic biomarker of metabolic changes resulting from mTOR inhibition. The utility of [(18) F]FLT for measuring the anti-proliferative effect of AZD8055 remains unclear.

Anti-tumour and anti-vascular effects of cediranib (AZD2171) alone and in combination with other anti-tumour therapies.

PURPOSE: Cediranib (AZD2171) is a highly potent inhibitor of all three vascular endothelial growth factor receptors. The aim of this preclinical study was to examine the effect of combining cediranib with mechanistically distinct anti-tumour therapies. METHODS: Cediranib (1.5 or 3 mg/kg/day) was evaluated alone and in combination with either gefitinib, imatinib, ZD6126, saracatinib, selumetinib, bevacizumab, 5-fluorouracil (5-FU), docetaxel, oxaliplatin, gemcitabine, pemetrexed, irinotecan or cisplatin in human tumour xenograft models. Anti-tumour activity was measured by assessing the change in tumour volume following treatment compared with vehicle-treated time-matched controls. RESULTS: In all cases, the combination regimens, at tolerated doses and schedules, inhibited tumour growth to a greater extent than the corresponding monotherapy treatments. Compared with cediranib alone, statistically significant enhancements in anti-tumour activity were observed with all combination regimens. Notably, after 14 days of treatment, the combination of cediranib with ZD6126 induced substantial tumour regression (60 % compared with pre-treatment volume), whilst treatment with each agent alone led only to partial growth inhibition. A combination of cediranib with gefitinib also induced tumour regressions, and cediranib combined with either gemcitabine or irinotecan was found to inhibit tumour growth profoundly (by 99 and 98 %, respectively). CONCLUSIONS: Combining cediranib with selected cytotoxic or targeted agents proved efficacious in a range of human tumour xenograft models.