Ruth Ruddle

A useful approach to identify novel small-molecule inhibitors of Wnt-dependent transcription.

The Wnt signaling pathway is frequently deregulated in cancer due to mutations in genes encoding APC, beta-catenin, and axin. To identify small-molecule inhibitors of Wnt signaling as potential therapeutics, a diverse chemical library was screened using a transcription factor reporter cell line in which the activity of the pathway was induced at the level of Disheveled protein. A series of deconvolution studies was used to focus on three compound series that selectively killed cancer cell lines with constitutive Wnt signaling. Activities of the compounds included the ability to induce degradation of beta-catenin that had been stabilized by a glycogen synthase kinase-3 (GSK-3) inhibitor. This screen illustrates a practical approach to identify small-molecule inhibitors of Wnt signaling that can seed the development of agents suitable to treat patients with Wnt-dependent tumors.

Dual blockade of the PI3K/AKT/mTOR (AZD8055) and RAS/MEK/ERK (AZD6244) pathways synergistically inhibits rhabdomyosarcoma cell growth in vitro and in vivo.

Purpose: To provide rationale for using phosphoinositide 3-kinase (PI3K) and/or mitogen-activated protein kinase (MAPK) pathway inhibitors to treat rhabdomyosarcomas, a major cause of pediatric and adolescent cancer deaths. Experimental Design: The prevalence of PI3K/MAPK pathway activation in rhabdomyosarcoma clinical samples was assessed using immunohistochemistry. Compensatory signaling and cross-talk between PI3K/MAPK pathways was determined in rhabdomyosarcoma cell lines following p110α short hairpin RNA–mediated depletion. Pharmacologic inhibition of reprogrammed signaling in stable p110α knockdown lines was used to determine the target-inhibition profile inducing maximal growth inhibition. The in vitro and in vivo efficacy of inhibitors of TORC1/2 (AZD8055), MEK (AZD6244), and P13K/mTOR (NVP-BEZ235) was evaluated alone and in pairwise combinations. Results: PI3K pathway activation was seen in 82.5% rhabdomyosarcomas with coactivated MAPK in 36% and 46% of alveolar and embryonal subtypes, respectively. p110α knockdown in cell lines over the short and long term was associated with compensatory expression of other p110 isoforms, activation of the MAPK pathway, and cross-talk to reactivate the PI3K pathway. Combinations of PI3K pathway and MAP–ERK kinase (MEK) inhibitors synergistically inhibited cell growth in vitro. Treatment of RD cells with AZD8055 plus AZD6244 blocked reciprocal pathway activation, as evidenced by reduced AKT/ERK/S6 phosphorylation. In vivo, the synergistic effect on growth and changes in pharmacodynamic biomarkers was recapitulated using the AZD8055/AZD6244 combination but not NVP-BEZ235/AZD6244. Pharmacokinetic analysis provided evidence of drug–drug interaction with both combinations. Conclusions: Dual PI3K/MAPK pathway activation and compensatory signaling in both rhabdomyosarcoma subtypes predict a lack of clinical efficacy for single agents targeting either pathway, supporting a therapeutic strategy combining a TORC1/2 with a MEK inhibitor. Clin Cancer Res; 19(21); 5940–51. ©2013 AACR.

Identification of 4-(4-Aminopiperidin-1-Yl)-7H-Pyrrolo[2,3-D]Pyrimidines as Selective Inhibitors of Protein Kinase B Through Fragment Elaboration.

Fragment-based screening identified 7-azaindole as a protein kinase B inhibitor scaffold. Fragment elaboration using iterative crystallography of inhibitor-PKA-PKB chimera complexes efficiently guided improvements in the potency and selectivity of the compounds, resulting in the identification of nanomolar 6-(piperidin-1-yl)purine, 4-(piperidin-1-yl)-7-azaindole, and 4-(piperidin-1-yl)pyrrolo[2,3- d]pyrimidine inhibitors of PKBbeta with antiproliferative activity and showing pathway inhibition in cells. A divergence in the binding mode was seen between 4-aminomethylpiperidine and 4-aminopiperidine containing molecules. Selectivity for PKB vs PKA was observed with 4-aminopiperidine derivatives, and the most PKB-selective inhibitor (30-fold) showed significantly different bound conformations between PKA and PKA-PKB chimera.

Combined MYC and P53 defects emerge at medulloblastoma relapse and define rapidly progressive, therapeutically targetable disease

Summary We undertook a comprehensive clinical and biological investigation of serial medulloblastoma biopsies obtained at diagnosis and relapse. Combined MYC family amplifications and P53 pathway defects commonly emerged at relapse, and all patients in this group died of rapidly progressive disease postrelapse. To study this interaction, we investigated a transgenic model of MYCN-driven medulloblastoma and found spontaneous development of Trp53 inactivating mutations. Abrogation of p53 function in this model produced aggressive tumors that mimicked characteristics of relapsed human tumors with combined P53-MYC dysfunction. Restoration of p53 activity and genetic and therapeutic suppression of MYCN all reduced tumor growth and prolonged survival. Our findings identify P53-MYC interactions at medulloblastoma relapse as biomarkers of clinically aggressive disease that may be targeted therapeutically.

Discovery of 4-Amino-1-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)piperidine-4-carboxamides As Selective, Orally Active Inhibitors of Protein Kinase B (Akt)

Protein kinase B (PKB or Akt) is an important component of intracellular signaling pathways regulating growth and survival. Signaling through PKB is frequently deregulated in cancer, and inhibitors of PKB therefore have potential as antitumor agents. The optimization of lipophilic substitution within a series of 4-benzyl-1-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)piperidin-4-amines provided ATP-competitive, nanomolar inhibitors with up to 150-fold selectivity for inhibition of PKB over the closely related kinase PKA. Although active in cellular assays, compounds containing 4-amino-4-benzylpiperidines underwent metabolism in vivo, leading to rapid clearance and low oral bioavailability. Variation of the linker group between the piperidine and the lipophilic substituent identified 4-amino-1-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)piperidine-4-carboxamides as potent and orally bioavailable inhibitors of PKB. Representative compounds modulated biomarkers of signaling through PKB in vivo and strongly inhibited the growth of human tumor xenografts in nude mice at well-tolerated doses.

An in vitro and in vivo study of the combination of the heat shock protein inhibitor 17-allylamino-17-demethoxygeldanamycin and carboplatin in human ovarian cancer models

PurposeTo study the interactions of the heat shock protein 90 (HSP90) inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) and carboplatin in vitro and in vivo.Experimental designThe combination of 17-AAG and carboplatin on the growth inhibition of A2780, SKOV-3, IGROV-1 and HX62 human ovarian cancer cells was studied in vitro by MTT assays. The effect of the sequence of administration of both drugs was further investigated in A2780 cells by sulforhodamine B assays. The ability of 17-AAG to deplete HSP90 client proteins either alone or in combination with carboplatin was evaluated by western blotting. Tumor concentrations of 17-AAG and carboplatin alone or in combination in vivo were determined by validated liquid chromatography with ultraviolet detection and atomic absorption spectroscopy methods. The growth inhibitory effects of 17-AAG, carboplatin and the combination were studied in the A2780 xenograft model.ResultsThe combination index (CI) at fu0.5 for 17-AAG plus carboplatin was 0.97 (±0.12 SD) when A2780 cells were exposed to carboplatin followed by 17-AAG indicating additivity. The addition of carboplatin did not alter the ability of 17-AAG to cause C-RAF, CDK4 and p-AKT depletion or HSP70 induction. Tumor 17-AAG and carboplatin concentrations were not significantly different in the single agent and combination arms. Tumor weights relative to controls on day 6 (T/C) were 67% for the carboplatin, 64% for the 17-AAG and 22% for the combination.ConclusionIn the specified sequences of drug exposure, 17-AAG and carboplatin have additive growth inhibitory effects in vitro and beneficial effects were seen with the combination in vivo. These findings form the basis for the possible evaluation of 17-AAG and carboplatin in a clinical trial.

Preclinical Pharmacology, Antitumor Activity, and Development of Pharmacodynamic Markers for the Novel, Potent AKT Inhibitor CCT128930

AKT is frequently deregulated in cancer, making it an attractive anticancer drug target. CCT128930 is a novel ATP-competitive AKT inhibitor discovered using fragment- and structure-based approaches. It is a potent, advanced lead pyrrolopyrimidine compound exhibiting selectivity for AKT over PKA, achieved by targeting a single amino acid difference. CCT128930 exhibited marked antiproliferative activity and inhibited the phosphorylation of a range of AKT substrates in multiple tumor cell lines in vitro, consistent with AKT inhibition. CCT128930 caused a G1 arrest in PTEN-null U87MG human glioblastoma cells, consistent with AKT pathway blockade. Pharmacokinetic studies established that potentially active concentrations of CCT128930 could be achieved in human tumor xenografts. Furthermore, CCT128930 also blocked the phosphorylation of several downstream AKT biomarkers in U87MG tumor xenografts, indicating AKT inhibition in vivo. Antitumor activity was observed with CCT128930 in U87MG and HER2-positive, PIK3CA-mutant BT474 human breast cancer xenografts, consistent with its pharmacokinetic and pharmacodynamic properties. A quantitative immunofluorescence assay to measure the phosphorylation and total protein expression of the AKT substrate PRAS40 in hair follicles is presented. Significant decreases in pThr246 PRAS40 occurred in CCT128930-treated mouse whisker follicles in vivo and human hair follicles treated ex vivo, with minimal changes in total PRAS40. In conclusion, CCT128930 is a novel, selective, and potent AKT inhibitor that blocks AKT activity in vitro and in vivo and induces marked antitumor responses. We have also developed a novel biomarker assay for the inhibition of AKT in human hair follicles, which is currently being used in clinical trials. Mol Cancer Ther; 10(2); 360–71. ©2010 AACR.

A phase I study of the nitroimidazole hypoxia marker SR4554 using 19F magnetic resonance spectroscopy.

Background:SR4554 is a fluorine-containing 2-nitroimidazole, designed as a hypoxia marker detectable with 19F magnetic resonance spectroscopy (MRS). In an initial phase I study of SR4554, nausea/vomiting was found to be dose-limiting, and 1400 mg m−2 was established as MTD. Preliminary MRS studies demonstrated some evidence of 19F retention in tumour. In this study we investigated higher doses of SR4554 and intratumoral localisation of the 19F MRS signal.Methods:Patients had tumours ⩾3 cm in diameter and ⩽4 cm deep. Measurements were performed using 1H/19F surface coils and localised 19F MRS acquisition. SR4554 was administered at 1400 mg m−2, with subsequent increase to 2600 mg m−2 using prophylactic metoclopramide. Spectra were obtained immediately post infusion (MRS no. 1), at 16 h (MRS no. 2) and 20 h (MRS no. 3), based on the SR4554 half-life of 3.5 h determined from a previous study. 19Fluorine retention index (%) was defined as (MRS no. 2/MRS no. 1)*100.Results:A total of 26 patients enrolled at: 1400 (n=16), 1800 (n=1), 2200 (n=1) and 2600 mg m−2 (n=8). SR4554 was well tolerated and toxicities were all ⩽grade 1; mean plasma elimination half-life was 3.7±0.9 h. SR4554 signal was seen on both unlocalised and localised MRS no. 1 in all patients. Localised 19F signals were detected at MRS no. 2 in 5 out of 9 patients and 4 out of 5 patients at MRS no. 3. The mean retention index in tumour was 13.6 (range 0.6–43.7) compared with 4.1 (range 0.6–7.3) for plasma samples taken at the same times (P=0.001) suggesting 19F retention in tumour and, therefore, the presence of hypoxia.Conclusion:We have demonstrated the feasibility of using 19F MRS with SR4554 as a potential method of detecting hypoxia. Certain patients showed evidence of 19F retention in tumour, supporting further development of this technique for detection of tumour hypoxia.

Abstract CT323: Accelerated phase I trial of two schedules of the combination of the PARP inhibitor olaparib and AKT inhibitor AZD5363 using a novel intrapatient dose escalation design in advanced cancer patients

Background: There is an urgent need for better trial designs to assess targeted drug combinations. We proposed a novel intrapatient (intrapt) dose escalation trial design to optimize drug exposures, minimize pharmacokinetic (PK) variability and reduce patient (pt) numbers needed (Yap et al, JCO 2013). In vivo synergy between PARP and PI3K pathway inhibition was seen in BRCA1-related and sporadic cancers (Juvekar et al; Ibrahim et al, Cancer Discov 2012), providing rationale for this study. Methods: Two-stage investigator initiated phase I trial: a) Intrapt dose escalation; b) Recommended phase II combination dose (RP2CD) expansion. Advanced cancer pts received escalating doses of AZD5363 (AZD) BID in 2 parallel arms (4 days on 3 days off [4/7 arm] at 320, 400, 480mg; 2 days on 5 days off [2/7 arm] at 480, 560, 640mg) with Olaparib (Ola) at 300mg BID in 3 weekly cycles. AZD was escalated after each cycle in each pt if drug related toxicities were ≤CTCAE G2. Dose limiting toxicities (DLT) were assessed during the 1st cycle of each dose level (DL). ≥6 evaluable pts were required at each DL. RECIST assessment was done every 3 cycles. Prior PARP or PI3K/AKT inhibitor use was allowed. PK and pharmacodynamics (PD) were assessed in tumor and normal tissue. Targeted +/- whole exome next generation sequencing was assessed in tumor and serial plasma DNA samples in all pts for predictive biomarkers of response. Results: Dose escalation was completed in 7.5 months (m) in 20 pts in 1 center; ≥6 evaluable pts were treated at each of the 3 DLs in both arms. Common (>15%) G1-2 toxicities were nausea, vomiting, fatigue, diarrhea and anemia. A DLT of G3 rash was seen at 480mg BID 4/7 AZD + 300mg BID Ola. Non DLT G3 anemia (n = 2), diarrhea (n = 2), fatigue (n = 1) and vomiting (n = 1) were seen in 4/7 arm; G3 hyperglycemia (n = 1), transaminitis (n = 1) and fatigue (n = 2) in 2/7 arm. No significant PK interactions were seen between Ola and AZD. Intrapt dose escalation of AZD showed dose dependent increases in PK exposures. Platelet-rich plasma PD showed significant decreases in pSer9 GSK3β post-therapy at all DLs (mean ≥55% [p Conclusion: This novel trial design led to rapid completion of dose escalation. RP2CD expansion (n = 40) is ongoing in: a) germline BRCA mut cancers; b) sporadic cancers with relevant somatic mutations. Citation Format: Vasiliki Michalarea, David Lorente, Juanita Lopez, Suzanne Carreira, Hasina Hassam, Mona Parmar, Nitharsan Sathiyayogan, Alison Turner, Emma Hall, Sonia Serrano Fandos, Satyanarayana Seeramreddi, Shaun Decordova, Karen Swales, Ruth Ruddle, Florence Raynaud, Nina Tunariu, Gerhardt Attard, L. Rhoda Molife, Udai Banerji, Ruth Plummer, Johann S. de Bono, Timothy A. Yap. Accelerated phase I trial of two schedules of the combination of the PARP inhibitor olaparib and AKT inhibitor AZD5363 using a novel intrapatient dose escalation design in advanced cancer patients. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT323. doi:10.1158/1538-7445.AM2015-CT323

p53 Loss in MYC-Driven Neuroblastoma Leads to Metabolic Adaptations Supporting Radioresistance

Neuroblastoma is the most common childhood extracranial solid tumor. In high-risk cases, many of which are characterized by amplification of MYCN, outcome remains poor. Mutations in the p53 (TP53) tumor suppressor are rare at diagnosis, but evidence suggests that p53 function is often impaired in relapsed, treatment-resistant disease. To address the role of p53 loss of function in the development and pathogenesis of high-risk neuroblastoma, we generated a MYCN-driven genetically engineered mouse model in which the tamoxifen-inducible p53ER(TAM) fusion protein was expressed from a knock-in allele (Th-MYCN/Trp53(KI)). We observed no significant differences in tumor-free survival between Th-MYCN mice heterozygous for Trp53(KI) (n = 188) and Th-MYCN mice with wild-type p53 (n = 101). Conversely, the survival of Th-MYCN/Trp53(KI/KI) mice lacking functional p53 (n = 60) was greatly reduced. We found that Th-MYCN/Trp53(KI/KI) tumors were resistant to ionizing radiation (IR), as expected. However, restoration of functional p53ER(TAM) reinstated sensitivity to IR in only 50% of Th-MYCN/Trp53(KI/KI) tumors, indicating the acquisition of additional resistance mechanisms. Gene expression and metabolic analyses indicated that the principal acquired mechanism of resistance to IR in the absence of functional p53 was metabolic adaptation in response to chronic oxidative stress. Tumors exhibited increased antioxidant metabolites and upregulation of glutathione S-transferase pathway genes, including Gstp1 and Gstz1, which are associated with poor outcome in human neuroblastoma. Accordingly, glutathione depletion by buthionine sulfoximine together with restoration of p53 activity resensitized tumors to IR. Our findings highlight the complex pathways operating in relapsed neuroblastomas and the need for combination therapies that target the diverse resistance mechanisms at play. Cancer Res; 76(10); 3025-35. ©2016 AACR.