Abstract B163: Identification and preclinical characterisation of VER-250840, a potent, selective Chk1 inhibitor with in vivo oral single-agent antitumor activity

On sustaining damage to their DNA, cells employ a sophisticated mechanism of detection and repair, termed the DNA damage response (DDR). As a critical component of the DDR and G2/M checkpoint, Chk1 kinase represents an attractive target for cancer therapy. We have utilized a structure-based drug design approach to identify and develop VER-250840, a novel, orally active inhibitor of the checkpoint kinase, Chk1. VER-250840 exhibited sub-nM potency against Chk1 kinase with exquisite selectivity over an extensive and diverse panel of kinases. In vitro, VER-250840 inhibited Chk1 autophosphorylation with an IC50 of 1.0 nM and increased the number of S-phase tumor cells staining positive for pan-nuclear γH2AX with an EC50 of 7 - 27 nM. Accumulated genomic DNA damage by Chk1 inhibition led to irreversible cell cycle arrest, inhibition of tumor cell proliferation, increased replication stress, and cell death in both 2D culture and multicellular tumor spheroids. In an in vivo A2058 tumor xenograft PD study, VER-250840 demonstrated rapid and sustained inhibition of Chk1 auto-phosphorylation within 30 minutes of oral administration. Doses of 10 mg/kg and higher PO resulted in greater than 90% inhibition of tumor pChk1 (S296) over 24 hours. In SKOV3 in vivo models, VER-250840 inhibited Chk1 auto-phosphorylation, modulated other biomarkers of replication stress and DNA damage, and exhibited moderate antitumor activity with minimal toxicity when administered orally on a 21-day once-daily schedule. Work is ongoing to further optimize in vivo efficacy. In conclusion, VER-250840 demonstrates potent and selective activity as a monotherapy both in vitro and in vivo. From these findings, further evaluation and optimization of this novel kinase inhibitor is justly merited.

Citation Format: Joanne Wayne, Stephen Stokes, Nicolas Foloppe, Helen Browne, Teresa Brooks, Karen Benwell, Lisa Baker, Zoe Daniels, Andrea Fiumana, Christopher Graham, Alba Macias, Daniel Maddox, Sean McKenna, Christopher Northfield, Stuart Ray, Heather Simmonite, Emma Stefaniak, Paul Webb, Mike Wood, Andrew Massey. Identification and preclinical characterisation of VER-250840, a potent, selective Chk1 inhibitor with in vivo oral single-agent antitumor activity [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B163.

Application of Off-Rate Screening in the Identification of Novel Pan-Isoform Inhibitors of Pyruvate Dehydrogenase Kinase

Libraries of nonpurified resorcinol amide derivatives were screened by surface plasmon resonance (SPR) to determine the binding dissociation constant (off-rate, k_d) for compounds binding to the pyruvate dehydrogenase kinase (PDHK) enzyme. Parallel off-rate measurements against HSP90 and application of structure-based drug design enabled rapid hit to lead progression in a program to identify pan-isoform ATP-competitive inhibitors of PDHK. Lead optimization identified selective sub-100-nM inhibitors of the enzyme which significantly reduced phosphorylation of the E1α subunit in the PC3 cancer cell line in vitro.

Heavy metals biosorption from aqueous solution by simple eucaryotic organisms

Biosorption of cadmium and chromium (III) ions by means of selected yeast species has been estimated. Kinetics and equilibrium measurements have shown the reliable efficiency of both metals removal for Candida tropicalis. The influence of pH and ionic strength on biosorption process has been examined as well. For both metals the adsorption isotherms have been presented. The equilibrium of chromium (III) sorption has appeared compatible to Langmiur model and the maximum sorption capacity has been determined.

Macrophages during infection with Trichinella spiralis in mice

Behaviour of macrophages in experimental mice trichinellosis was investigated using the immunoenzymatic technique with monoclonal antibodies CD11b/CD18 within the framework of avidin-biotin-DAB. The maximum and earliest mobilization of macrophages 7 day post infection (dpi) was observed in the lamina propria of the intestinal mucosa. The highest level of macrophages in the muscles tissue was noted on day 21 of infection, however as early as in 28 dpi, their maximum level was observed inside the larval capsules. They line, especially between 35-42 dpi internal capsule surface.

The cells observed inside capsules of larvae in the course of experimental trichinellosis in mice

In the course of trichinellosis in mice the numerous cells inside larval capsules were observed. Beginning on 14 day post infection (dpi) they were seen in about 7% of infected muscles fibers but at 21 dpi the percentage of capsules with the cells amounted to 77. In the next stage of infection the number of capsules containing cells continued to increase and reach almost 100% at 60 dpi. The identification of the cells was carried out by the indirect immunoenzymatic method using anti-CD4+, anti-CD8+ and anti-macrophage (Mac-1 antigen) monoclonal antibodies. In course of observation the level of CD4+ cells decreased from 11.3 to 0.7, of CD8+ from 17.7 to 3.0 and of macrophages from 71.0 to 23.1%. The most numerous CD4+ cells were seen at 14 dpi while the CD8+ and macrophages at 21 dpi. Beginning on 28 dpi negatively reacting cells inside larval capsules were also observed. The number of these cells increased from 23.8 to 73.2% at 60 dpi and their identification requires further investigations. The role and the function of all these cells are discussed.

[The influence of ricin on the course of experimental infections of mice with Trichinella spiralis]

Mice received 5 ng of ricin 24 hours after infection (experiment I) or 1 ng of ricin twice, 24 hours and 17 days of infection (experiment II). Animals were killed in 7, 14, 21, 28, 35, 42 and 60 days after infection. In the jejunum and masseter muscle sections, CD4+ and CD8+ lymphocytes, mast cells and eosinophils were studied. Heavy suppression of CD8+ lymphocytes, strong eosinophils and less pronounced mast cells stimulation was observed in the jejunum of mice received ricin (experiment I). Worm expulsion in intestine was faster than in the control (opposite results in experiment II). The composition of cells infiltration in the muscle was in both experiments similar to the control, however, fewer CD4+ lymphocytes were observed in larva capsule and there were fewer muscle larvae. Therefore CD8+ cells are believed to take part in restricting only the muscle stage of trichinellosis.

[One center's experience with fibrinolytic treatment in children]

Fifteen children treated with fibrinolytic agents are presented. The most frequent indication was thromboembolic disease (TED). Eleven patients received streptokinase, 5-urokinase and 3-tissue plasminogen activator. Concomitant heparin was administered to 9 patients with TED. Total resolution was achieved in 9 children, partial improvement in 5; 1 child died during treatment without any improvement. Bleeding complications were observed in 6 patients, 1 of them died due to haemorrhagic stroke. According to the literature and our own experience, we recommend fibrinolytic agents as the treatment of choice for severe TED also in children.

[The influence of phytohemagglutinin P on CD4+ and CD8+ cells in the course of experimental trichinellosis in mice]

Experiments were carried out with mice of CFW inbred strain infected with 200 Trichinella spiralis larvae and divided into two groups: experimental and control. The experimental mice were injected with phytohaemagglutinin P (PHA-P), 24 h before infection. The all animals were killed between 7-133 days post infection and the pieces of spleens, mesenteric lymph nodes, jejunum and masseter muscles were sectioned in a cryostat and examined with monoclonal antibodies (anti-Thy 1, 2, anti-CD4+ and anti-CD8+) by immunoenzymatic method. In the animals treated with PHA-P, more numerous CD4+ cells were observed in comparison with the control. The CD8+ cells were stimulated only in the muscles. The most important problem were the CD4+ and CD8+ cells inside the larvae capsules. The role of the CD4+ and CD8+ cells in the immunopathological changes in the course of trichinellosis was discussed.

An unusual pedigree with microcornea-cataract syndrome

A pedigree with 14 patients affected with microcornea-cataract (MC) syndrome is described. MC syndrome is very rare and this pedigree is probably the sixth to be reported. Transmission is most likely autosomal dominant, but the unusual feature of the present family is the fact that the proportion of affected members is so high that one is tempted to suspect preferential transmission of the chromosome carrying the MC gene.