Late onset variants in Fabry disease: Results in high risk population screenings in Argentina

Background

Screening for Fabry disease (FD) in high risk populations yields a significant number of individuals with novel, ultra rare genetic variants in the GLA gene, largely without classic manifestations of FD. These variants often have significant residual α-galactosidase A activity. The establishment of the pathogenic character of previously unknown or rare variants is challenging but necessary to guide therapeutic decisions.

Objectives

To present 2 cases of non-classical presentations of FD with renal involvement as well as to discuss the importance of high risk population screenings for FD.

Results

Our patients with non-classical variants were diagnosed through FD screenings in dialysis units. However, organ damage was not limited to kidneys, since LVH, vertebrobasilar dolichoectasia and cornea verticillata were also present. Lyso-Gb3 concentrations in plasma were in the pathologic range, compatible with late onset FD. Structural studies and in silico analysis of p.(Cys174Gly) and p.(Arg363His), employing different tools, suggest that enzyme destabilization and possibly aggregation could play a role in organ damage.

Conclusions

Screening programs for FD in high risk populations are important as FD is a treatable multisystemic disease which is frequently overlooked in patients who present without classical manifestations.

Differential effects of duration of sleep fragmentation on spatial learning and synaptic plasticity in pubertal mice

STUDY OBJECTIVE

To examine the differential effects of acute and chronic sleep fragmentation (SF) on spatial learning and memory, and hippocampal long-term potentiation (LTP) in pubertal mice.

METHODS

Two studies were performed during which adolescent C57/Bl6 mice were subjected to acute-SF 24h a day × 3 days or chronic-SF for 12h a day × 2 weeks using a programmable rotating lever that provides tactile stimulus with controls housed in similar cages. Spatial learning and memory was examined using the Morris water maze, and long-term potentiation (LTP) was evaluated after stimulation of Schaffer collaterals in CA1 hippocampus post SF. Actigraphy was used during the period of SF to monitor rest-activity patterns. Electroencephalographic (EEG) recordings were acquired for analysis of vigilance state patterns and delta-power. Serum corticosterone was measured to assess stress levels.

RESULTS

Acute-SF via tactile stimulation negatively impacted spatial learning, as well as LTP maintenance, compared to controls with no tactile stimulation. While actigraphy showed significantly increased motor activity during SF in both groups, EEG data indicated that overall sleep efficiency did not differ between baseline and SF days, but significant increases in number of wakeful bouts and decreases in average NREM and REM bout lengths were seen during lights-on. Acute sleep fragmentation did not impact corticosterone levels.

CONCLUSIONS

The current results indicate that, during development in pubertal mice, acute-SF for 24h a day × 3 days negatively impacted spatial learning and synaptic plasticity. Further studies are needed to determine if any inherent long-term homeostatic mechanisms in the adolescent brain afford greater resistance to the deleterious effects of chronic-SF.

Umbilical blood flow patterns directly after birth before delayed cord clamping

BACKGROUND

Delayed umbilical cord clamping (DCC) affects the cardiopulmonary transition and blood volume in neonates immediately after birth. However, little is known of blood flow in the umbilical vessels immediately after birth during DCC. The objective is to describe the duration and patterns of blood flow through the umbilical vessels during DCC.

METHODS

Arterial and venous umbilical blood flow was measured during DCC using Doppler ultrasound in uncomplicated term vaginal deliveries. Immediately after birth, the probe was placed in the middle of the umbilical cord, pattern and duration of flow in vein and arteries were evaluated until cord clamping.

RESULTS

Thirty infants were studied. Venous flow: In 10% no flow was present, in 57% flow stopped at 4:34 (3:03-7:31) (median (IQR) min:sec) after birth, before the cord was clamped. In 33%, flow continued until cord clamping at 5:13 (2:56-9:15) min:sec. Initially, venous flow was intermittent, increasing markedly during large breaths or stopping and reversing during crying, but then became continuous. Arterial flow: In 17% no flow was present, in 40% flow stopped at 4:22 (2:29-7:17) min:sec, while cord pulsations were still palpable. In 43% flow continued until the cord was clamped at 5:16 (3:32-10:10) min:sec. Arterial flow was pulsatile, unidirectional towards placenta or bidirectional to/from placenta. In 40% flow became continuous towards placenta later on.

CONCLUSIONS

During delayed umbilical cord clamping, venous and arterial umbilical flow occurs for longer than previously described. Net placental transfusion is probably the result of several factors of which breathing could play a major role. Umbilical flow is unrelated to cessation of pulsations.

Pulmonary arterial hypertension: basis of sex differences in incidence and treatment response

Pulmonary arterial hypertension (PAH) is a complex disease characterized by elevated pulmonary arterial pressure, pulmonary vascular remodelling and occlusive pulmonary vascular lesions, leading to right heart failure. Evidence from recent epidemiological studies suggests the influence of gender on the development of PAH with an approximate female to male ratio of 4:1, depending on the underlying disease pathology. Overall, the therapeutic strategy for PAH remains suboptimal with poor survival rates observed in both genders. Endogenous sex hormones, in particular 17β oestradiol and its metabolites, have been implicated in the development of the disease; however, the influence of sex hormones on the underlying pathobiology remains controversial. Further understanding of the influence of sex hormones on the normal and diseased pulmonary circulation will be critical to our understanding the pathology of PAH and future therapeutic strategies. In this review, we will discuss the influence of sex hormones on the development of PAH and address recent controversies.

First Report of Pseudoperonospora cubensis Causing Downy Mildew on Momordica balsamina and M. charantia in North Carolina

Momordica balsamina (balsam apple) and M. charantia L. (bitter melon/bitter gourd/balsam pear) commonly grow in the wild in Africa and Asia; bitter melon is also cultivated for food and medicinal purposes in Asia (1). In the United States, these cucurbits grow as weeds or ornamentals. Both species are found in southern states and bitter melon is also found in Pennsylvania and Connecticut (3). Cucurbit downy mildew (CDM), caused by the oomycete Pseudoperonospora cubensis, was observed on bitter melon and balsam apple between August and October of 2013 in six North Carolina sentinel plots belonging to the CDM ipmPIPE program (2). Plots were located at research stations in Johnston, Sampson, Lenoir, Henderson, Rowan, and Haywood counties, and contained six different commercial cucurbit species including cucumbers, melons, and squashes in addition to the Momordica spp. Leaves with symptoms typical of CDM were collected from the Momordica spp. and symptoms varied from irregular chlorotic lesions to circular lesions with chlorotic halos on the adaxial leaf surface. Sporulation on the abaxial side of the leaves was observed and a compound microscope revealed sporangiophores (180 to 200 μm height) bearing lemon-shaped, dark sporangia (20 to 35 × 10 to 20 μm diameter) with papilla on one end. Genomic DNA was extracted from lesions and regions of the NADH dehydrogynase subunit 1 (Nad1), NADH dehydrogynase subunit 5 (Nad5), and internal transcribed spacer (ITS) ribosomal RNA genes were amplified and sequenced (4). BLAST analysis revealed 100% identity to P. cubensis Nad1 (HQ636552.1, HQ636551.1), Nad5 (HQ636556.1), and ITS (HQ636491.1) sequences in GenBank. Sequences from a downy mildew isolate from each Momordica spp. were deposited in GenBank as accession nos. KJ496339 through 44. To further confirm host susceptibility, vein junctions on the abaxial leaf surface of five detached leaves of lab-grown balsam apple and bitter melon were either inoculated with a sporangia suspension (10 μl, 10⁴ sporangia/ml) of a P. cubensis isolate from Cucumis sativus ('Vlaspik' cucumber), or with water as a control. Inoculated leaves were placed in humidity chambers to promote infection and incubated using a 12-h light (21°C) and dark (18°C) cycle. Seven days post inoculation, CDM symptoms and sporulation were observed on inoculated balsam apple and bitter melon leaves. P. cubensis has been reported as a pathogen of both hosts in Iowa (5). To our knowledge, this is the first report of P. cubensis infecting these Momordica spp. in NC in the field. Identifying these Momordica spp. as hosts for P. cubensis is important since these cucurbits may serve as a source of CDM inoculum and potentially an overwintering mechanism for P. cubensis. Further research is needed to establish the role of non-commercial cucurbits in the yearly CDM epidemic, which will aid the efforts of the CDM ipmPIPE to predict disease outbreaks. References: (1) L. K. Bharathi and K. J. John. Momordica Genus in Asia-An Overview. Springer, New Delhi, India, 2013. (2) P. S. Ojiambo et al. Plant Health Prog. doi:10.1094/PHP-2011-0411-01-RV, 2011. (3) PLANTS Database. Natural Resources Conservation Service, USDA. Retrieved from http://plants.usda.gov/ , 7 February 2014. (4) L. M. Quesada-Ocampo et al. Plant Dis. 96:1459, 2012. (5) USDA. Index of Plant Disease in the United States. Agricultural Handbook 165, 1960.

The epidemiology of malpractice claims in primary care: a systematic review

OBJECTIVES

The aim of this systematic review was to examine the epidemiology of malpractice claims in primary care.

DESIGN

A computerised systematic literature search was conducted. Studies were included if they reported original data (≥10 cases) pertinent to malpractice claims, were based in primary care and were published in the English language. Data were synthesised using a narrative approach.

SETTING

Primary care.

PARTICIPANTS

Malpractice claimants.

PRIMARY OUTCOME

Malpractice claim (defined as a written demand for compensation for medical injury). We recorded: medical misadventure cited in claims, missed/delayed diagnoses cited in claims, outcome of claims, prevalence of claims and compensation awarded to claimants.

RESULTS

Of the 7152 articles retrieved by electronic search, a total of 34 studies met the inclusion criteria and were included in the narrative analysis. Twenty-eight studies presented data from medical indemnity malpractice claims databases and six studies presented survey data. Fifteen studies were based in the USA, nine in the UK, seven in Australia, one in Canada and two in France. The commonest medical misadventure resulting in claims was failure to or delay in diagnosis, which represented 26-63% of all claims across included studies. Common missed or delayed diagnoses included cancer and myocardial infarction in adults and meningitis in children. Medication error represented the second commonest domain representing 5.6-20% of all claims across included studies. The prevalence of malpractice claims in primary care varied across countries. In the USA and Australia when compared with other clinical disciplines, general practice ranked in the top five specialties accounting for the most claims, representing 7.6-20% of all claims. However, the majority of claims were successfully defended.

CONCLUSIONS

This review of malpractice claims in primary care highlights diagnosis and medication error as areas to be prioritised in developing educational strategies and risk management systems.

Transanal irrigation in the management of neurogenic bowel dysfunction

Many patients with a spinal cord injury (SCI) or spina bifida suffer from neurogenic bowel dysfunction which causes significant physical and psychological morbidity. For the last four years at the National Rehabilitation Hospital, transanal irrigation (TAI) has been offered to patients who were dissatisfied with a conservative bowel management programme. This is an observational study of eleven patients who were offered TAI. Three questionnaires, scoring bowel symptoms at baseline and follow-up (3-28 months) were completed by patients. Nine patients had a SCl and two had spina bifida, mean age was 44 years. A reduction in mean scores for all three questionnaires occurred post TAI (39.5-42.1%) indicating fewer bowel symptoms. Statistically significant reductions in faecal incontinence (p < 0.05), abdominal pain (p < 0.05) and lifestyle alterations secondary to bowel management (p < 0.05) occurred. No serious adverse events occurred during the study. TAI is an effective treatment option for the management of neurogenic bowel dysfunction.

Abstract A143: ARRY-380, a selective HER2 inhibitor: From drug design to clinical evaluation

In recent years, there has been discussion on the relative benefits of drugs that are kinase selective and those targeting multiple kinases, both in terms of clinical activity and safety. While the value of selectivity may be target dependent, there is now evidence that HER2 can be effectively targeted with a selective small molecule. Designing a selective HER2 inhibitor is challenging, as the ATP-binding pockets of EGFR and HER2 differ by only 2 amino acids and only 1 of these is involved with inhibitor binding (Cys775 vs. Ser783). While obtaining this selectivity was difficult, the goal of developing a drug that would inhibit HER2 without EGFR-related side effects was deemed advantageous, especially since it appears that inhibition of EGFR does not improve the efficacy of HER2-targeted therapy in patients (pts) with HER2+ metastatic breast cancer (MBC) (Arteaga, et al. Clin Cancer Res. 2008; 14(19):6277–83).

ARRY-380 is an orally active, potent, small-molecule tyrosine kinase inhibitor of HER2. The compound is a reversible, ATP-competitive inhibitor with nanomolar potency in enzymatic and cellular assays. In cell-based assays, ARRY-380 is ∼500-fold selective for HER2 versus EGFR and is equipotent against truncated p95-HER2. ARRY-380 is currently undergoing evaluation in a first-inhuman Phase 1 dose-escalation and expansion study designed to identify the maximum tolerated dose (MTD) and to assess the safety, pharmacokinetics (PK) and preliminary efficacy in pts with advanced solid tumors that express the HER2 target.

In the dose-escalation phase, pts with HER2+ MBC or other documented HER2+ cancers were treated with ARRY-380 as a single oral dose on Cycle (C)1 Day (D)1 followed by twice daily (BID) dosing, beginning on C1 D3, in 28-day dosing cycles. Safety was assessed by adverse events (AEs), clinical laboratory test results, physical examinations, vital signs and ECGs. Tumor response was assessed every 2 cycles.

As of August 31, 2011, 50 pts (43 with MBC) have received ARRY-380. In the completed dose-escalation phase, 33 pts were enrolled and treated at doses ranging from 25 mg to 800 mg BID; of these, 26 had HER2+ MBC and all were previously treated with trastuzumab and 81% with lapatinib. The MTD was determined to be 600 mg BID. Of 19 evaluable pts with HER2+ MBC receiving doses ≥ 200 mg BID, 6 (32%) had a partial response (PR) or stable disease (SD) ≥ 6 months; 10 pts had regression of tumor lesions, of these, 1 pt (5%) had a PR and 9 pts (47%) had SD. Treatment-related AEs included Grade 2 events of increased ALT/AST (5), constipation (1), fatigue (3), hyperbilirubinemia (1) and nausea (1) and Grade 3 AEs of increased ALT/AST (3), night sweats (1) and rash (1). No Grade 4 treatment-related AEs have been reported, nor has any treatment-related AE led to study drug discontinuation. An expansion cohort to confirm safety and further examine activity of ARRY-380 at the MTD in pts with HER2+ MBC is ongoing; enrollment is complete (N = 17) and data analysis is continuing. In conclusion, in the small number of pts treated to date, ARRY-380 is associated with few EGFR-related side effects. In heavily pre-treated MBC pts, ARRY-380 is exhibiting preliminary signs of efficacy with an acceptable safety profile. Thus, continued clinical development of ARRY-380 is warranted to further evaluate if a selective, small-molecule HER2 inhibitor may be an alternative treatment option to a multi-kinase inhibitor in pts with HER2+ cancers.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A143.

Chk1 inhibition and Wee1 inhibition combine synergistically to impede cellular proliferation

Inhibition of the checkpoint kinase Chk1, both as a monotherapy and in combination with DNA damaging cytotoxics, is a promising therapeutic approach for the treatment of a wide array of human cancers. However, much remains to be elucidated in regard to the patient populations that will respond best to a Chk1 inhibitor and the optimal therapeutics to combine with a Chk1 inhibitor. In an effort to discover sensitizing mutations and novel combination strategies for Chk1 inhibition, an siRNA screen was performed in combination with the selective Chk1 inhibitor AR458323. This screen employed a custom made library of siRNAs targeting 195 genes, most of which are involved in cell-cycle control or DNA damage repair. One of the most prominent and consistent hits across runs of the screen performed in three different cancer cell lines was Wee1 kinase. MK-1775 is a small molecule inhibitor of Wee1 that is currently in early stage clinical trials. In confirmation of the results obtained from the siRNA screen, AR458323 and MK-1775 synergistically inhibited proliferation in multiple cancer cell types. This antiproliferative effect correlated with a synergistic induction of apoptosis. In cellular mechanistic studies, the combination of the two molecules resulted in dramatic decreases in inhibitory phosphorylation of cyclin-dependent kinases, an increase in DNA damage, alterations in cell-cycle profile, and collapse of DNA synthesis. In conclusion, the clinical combination of a Chk1 inhibitor and a Wee1 inhibitor holds promise as an effective treatment strategy for cancer.

Single-agent inhibition of Chk1 is antiproliferative in human cancer cell lines in vitro and inhibits tumor xenograft growth in vivo

Chk1 is a serine/threonine kinase that plays several important roles in the cellular response to genotoxic stress. Since many current standard-of-care therapies for human cancer directly damage DNA or inhibit DNA synthesis, there is interest in using small molecule inhibitors of Chk1 to potentiate their clinical activity. Additionally, Chk1 is known to be critically involved in cell cycle progression of unperturbed cells. Therefore, it is plausible that treatment with a Chkl inhibitor alone could also be an efficacious cancer therapy. Here we report that Chk1-A, a potent and highly selective small molecule inhibitor of Chk1, is antiproliferative as a single agent in a variety of human cancer cell lines in vitro. The inhibition of proliferation is associated with collapse of DNA replication and apoptosis. Rapid decreases in inhibitory phosphorylation of CDKs and a concomitant increase in CDK kinase activity and chromatin loading of Cdc45 suggest that the antiproliferative and proapoptotic activity of Chk1-A is at least in part due to deregulation of DNA synthesis. We extend these in vitro studies by demonstrating that Chk1-A inhibits the growth of tumor xenografts in vivo in a treatment regimen that is well tolerated. Together, these results suggest that single-agent inhibition of Chk1 may be an effective treatment strategy for selected human malignancies.

Abstract 2939: Chk1 inhibition and Wee1 inhibition combine synergistically to inhibit cellular proliferation

Inhibition of the checkpoint kinase Chk1, both as a monotherapy and in combination with DNA damaging cytotoxics, is a promising therapeutic strategy for human cancer. However, much remains to be learned in regard to the patient populations that will respond best to a Chk1 inhibitor and the optimal therapeutics to combine with a Chk1 inhibitor. In an effort to discover sensitizing mutations and novel combination strategies for Chk1 inhibition, we performed a synthetic lethality siRNA screen with the selective Chk1 inhibitor Chk1-A. This screen employed a custom made library of siRNAs against 197 genes (3 siRNAs per gene), most of which are involved in cell-cycle control or DNA damage repair. One of the most prominent and consistent hits across runs of the screen performed in PC3, LNCaP, and A549 cell lines was Wee1 kinase. MK-1775 is a small molecule inhibitor of Wee1 that is currently in early stage clinical trials. In confirmation of the results obtained from the siRNA screen, we found that Chk1-A and MK-1775 synergistically inhibited proliferation in multiple cell types. The combination of the two molecules resulted in up to a 5-fold enhancement of anti-proliferative activity compared to what would be expected from pure additivity. This anti-proliferative synergy correlated with a synergistic induction of apoptosis. We explored the mechanism of the impressive synergy by examining the cellular and biochemical effects of the Chk1-A and MK-1775 combination. We found that co-treatment with the two inhibitors resulted in dramatic decreases in inhibitory phosphorylation of cyclin-dependent kinases 1 and 2, increases in DNA damage, and the collapse of DNA replication. In conclusion, the combination of a Chk1 inhibitor and a Wee1 inhibitor may be an effective treatment strategy for cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2939. doi:10.1158/1538-7445.AM2011-2939

Gamma-ray emission concurrent with the nova in the symbiotic binary V407 Cygni

Novae are thermonuclear explosions on a white dwarf surface fueled by mass accreted from a companion star. Current physical models posit that shocked expanding gas from the nova shell can produce x-ray emission, but emission at higher energies has not been widely expected. Here, we report the Fermi Large Area Telescope detection of variable gamma-ray emission (0.1 to 10 billion electron volts) from the recently detected optical nova of the symbiotic star V407 Cygni. We propose that the material of the nova shell interacts with the dense ambient medium of the red giant primary and that particles can be accelerated effectively to produce pi(0) decay gamma-rays from proton-proton interactions. Emission involving inverse Compton scattering of the red giant radiation is also considered and is not ruled out.

Abstract 4484: AR-mTOR-26 - A potent, selective mTORC 1/2 kinase inhibitor for the treatment of malignancy

As a consequence of a variety of genetic lesions, the PI3K/Akt pathway is constitutively activated in a large proportion of human cancers. The mTOR kinase plays an important role in this pathway as the key component of two independent signaling complexes (TORC1 and TORC2) that are involved at two distinct levels in this signaling cascade. Accordingly, inhibition of mTOR kinase will abrogate signaling from both mTOR complexes and serve as an effective means of targeting this pathway. In addition, the activity of the TORC1 complex is often aberrantly activated in a PI3K-independent manner to allow tumor cells to survive and proliferate despite the many negative influences of the tumor microenvironment such as hypoxia and limited nutrient availability. Therefore, an inhibitor of both TORC1 and TORC2 should effectively block signaling from the PI3K pathway as well as abrogate the cancer cells’ ability to survive in the harsh environment of the tumor thereby providing an effective means of treating cancer.

We report here the profile of our small molecule mTOR kinase inhibitor AR-mTOR-26. On enzyme, this compound inhibits mTOR kinase with an IC50 of 1 nM while exhibiting substantial selectivity against PI3Kα as well as a panel of lipid and protein kinases. In cells, AR-mTOR-26 inhibits the TORC1-dependent readouts pS6 (Ser235/6) and p4E-BP1 (Ser37/46) as well as the TORC2 phosphorylation site on Akt, Ser473, with IC50 values of &lt;50 nM. Consistent with its selectivity over PI3Kα, AR-mTOR-26 does not significantly inhibit Thr308 on AKT, a PI3K/PDK1-dependent readout. In addition, we show that AR-mTOR-26 is broadly and potently anti-proliferative across a panel of solid and hematological cancer cell lines, irrespective of their mutational status suggesting the potential for broad therapeutic utility. We then evaluated the in vivo activity of AR-mTOR-26. By oral administration, AR-mTOR-26 exhibits excellent pharmacokinetics in mice with plasma concentrations that are predicted to be efficacious. Doses ranging from 1-10 mg/kg once daily to tumor-bearing mice results in significant anti-tumor activity in several mouse xenograft models, including PC3 prostate [PTEN null] and H460 lung [KRASG12D/PIK3CA]. These effects ranged from tumor growth inhibition to regressions dependent upon the dose and the xenograft model evaluated. In all, these data show that targeting mTOR kinase with AR-mTOR-26 holds promise as a broadly acting therapeutic for oncology.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4484.

Abstract 3855: Investigation of the growth inhibitory activity of the MEK inhibitor ARRY-438162 in combination with everolimus in a variety of KRas and PI3K pathway mutant cancers

The RAS/RAF/MEK/ERK and PI3K signaling pathways are known to play key roles in cell growth, proliferation and survival. Targeted agents against factors in these pathways have been shown to provide therapeutic benefit in the treatment of cancer. However, there exists a considerable degree of cross-talk between these pathways such that when one pathway is inhibited the other is upregulated to sustain growth and survival signaling. Therefore, it would be expected that the concomitant use of targeted agents against both of these pathways would overcome the negative effects of this crosstalk, and enhance the ability of these agents to block cancer cell growth. We sought to understand whether or not the combination of the MEK inhibitor ARRY-438162 and the TORC1 inhibitor Everolimus would combine to enhance cell killing compared to the activity of the single agents. It has been established that in the majority of cancers, constituents of one or both of these pathways are mutated conferring constitutive activation to the pathway. Thus, we investigated whether key common mutations in either of these pathways conferred particular sensitivity or resistance to the combination. The growth inhibitory activities of ARRY-438162 and Everolimus were assessed alone and in combination in 26 different cell lines from a variety of human cancers with documented mutations in the KRAS, PTEN, PI3K and BRAF genes. In this regard, we report the identification of key genotypes that are associated with antagonistic, additive, and synergistic responses to the combination. In particular, treatment of the NCI-H460 NSCLC line [KRASG12D/PIK3CA] was only modestly responsive to either ARRY-162 or Everolimus as single agents (10% and 20% growth inhibition, respectively). However, the combination significantly inhibited the growth of this line, a result that was confirmed as synergistic by Bliss analysis. In order to validate the relevance of our in vitro data, an in vivo study was performed using NCI-H460 xenografts in nude mice. Everolimus alone showed no tumor growth inhibition while ARRY-438162 at doses of 30, 100 and 300 mg/kg, BID produced dose-related modest tumor growth inhibition (up to ∼50%). Combining the agents produced enhanced activity at all dose levels of ARRY-438162 without altering the exposure of either agent. Finally, in addition to growth inhibition, the biochemical effects of the single agent and the combination treatment on S6 protein, Erk, Akt, and various apoptosis regulator proteins were assessed as well as their effects on apoptosis and autophagy. ARRY-438162 having demonstrated significant tumor growth inhibitory activity in numerous pre-clinical models and acceptable preclinical and clinical safety profiles has advanced into Phase 1 clinical development.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3855.

Abstract 3874: Single-agent Chk1 inhibition is anti-proliferative in leukemia cells in vitro and in vivo

Chk1 is a serine/threonine kinase that plays important roles in the cellular response to genotoxic stress. For this reason, there is a great deal of interest in using inhibitors of Chk1 to potentiate the effects of DNA-damaging chemotherapeutics. In addition, multiple studies have demonstrated that Chk1 activity is essential during an unperturbed cell cycle to ensure proper DNA replication and maintain genomic integrity. Therefore, it is plausible that a Chk1 inhibitor could also be efficacious as a single-agent therapeutic for human cancer. Here we show that treatment with Chk1-A, a potent and selective inhibitor of Chk1, alone is anti-proliferative against a wide array of cancer cell lines with varying degrees of potency. We sought to understand the mechanisms by which Chk1 inhibition derives the observed anti-proliferative effect. Employing the human leukemia cell line HEL92.1.7, a line particularly sensitive to Chk1 inhibition in terms of proliferation, we characterized the biochemical and functional effects of Chk1-A treatment. We observed concentration-dependent increases in phosphorylation of H2A. X, Chk1, and Chk2, which are markers of DNA damage and cell-cycle checkpoint activation. These biochemical events correlated with S-phase accumulation and eventual apoptosis. In vivo, we found that HEL92.1.7 tumor xenografts were sensitive to oral administration of Chk1-A at a dose that was well tolerated. Together, these studies suggest that inhibition of Chk1 results in DNA damage that induces apoptosis and that use of a Chk1 inhibitor as a single-agent could be an effective strategy to treat certain types of human cancers.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3874.