The Checkpoint Kinase 1 Inhibitor Prexasertib Induces Regression of Preclinical Models of Human Neuroblastoma

Abstract

Checkpoint kinase 1 (CHK1) is a key regulator of the DNA damage response and a mediator of replication stress through modulation of replication fork licensing and activation of S and G-M cell-cycle checkpoints. We evaluated prexasertib (LY2606368), a small-molecule CHK1 inhibitor currently in clinical testing, in multiple preclinical models of pediatric cancer. Following an initial assessment of prexasertib activity, this study focused on the preclinical models of neuroblastoma. We evaluated the antiproliferative activity of prexasertib in a panel of cancer cell lines; neuroblastoma cell lines were among the most sensitive. Subsequent Western blot and immunofluorescence analyses measured DNA damage and DNA repair protein activation. Prexasertib was investigated in several cell line-derived xenograft mouse models of neuroblastoma. Within 24 hours, single-agent prexasertib promoted γH2AX-positive double-strand DNA breaks and phosphorylation of DNA damage sensors ATM and DNA-PKcs, leading to neuroblastoma cell death. Knockdown of CHK1 and/or CHK2 by siRNA verified that the double-strand DNA breaks and cell death elicited by prexasertib were due to specific CHK1 inhibition. Neuroblastoma xenografts rapidly regressed following prexasertib administration, independent of starting tumor volume. Decreased Ki67 and increased immunostaining of endothelial and pericyte markers were observed in xenografts after only 6 days of exposure to prexasertib, potentially indicating a swift reduction in tumor volume and/or a direct effect on tumor vasculature. Overall, these data demonstrate that prexasertib is a specific inhibitor of CHK1 in neuroblastoma and leads to DNA damage and cell death in preclinical models of this devastating pediatric malignancy. .

Novel CHK1 inhibitor MU380 exhibits significant single-agent activity in TP53-mutated chronic lymphocytic leukemia cells

“…for combination with chemotherapy. Nevertheless, some of them showed interesting pre-clinical single-agent activity against diverse cancer types, including breast and ovarian cancer, 14 smallcell lung cancer, 15 colorectal cancer, 16 neuroblastoma, 17 melanoma, 18 MYC driven lymphoma, 19 and leukemia. 20,21 Currently, several CHK1 inhibitors are undergoing evalution in clinical trials focusing on solid tumors and hematologic malignancies.…”

Olaratumab Exerts Antitumor Activity in Preclinical Models of Pediatric Bone and Soft Tissue Tumors through Inhibition of Platelet-Derived Growth Factor Receptor α

“…Protein expression and phosphorylation status was assessed by SDS-PAGE and immunoblotting as described previously (27). Briefly, whole-cell lysates (30-50 mg of protein/sample) were separated on gradient Tris-Glycine protein gels (Novex, Thermo Fisher Scientific) and transferred to nitrocellulose via TransBlot Turbo (Bio-Rad, cat #170-4159).…”

Dose‐finding study of the checkpoint kinase 1 inhibitor, prexasertib, in Japanese patients with advanced solid tumors

“…Prexasertib (LY2606368) is an inhibitor of CHK1 and, to a lesser extent, CHK2 that can disrupt DNA replication, induce DNA damage, and prevent DNA repair, eventually leading to cell death via interruption of DNA replication . Preclinical studies in solid tumor models have shown that prexasertib as a single agent, or in combination with other agents, has both in vitro and in vivo antitumor activity . Prexasertib, in combination with cetuximab and irradiation, has also been shown to have antitumor effects in head and neck squamous cell carcinoma (SCC) in vitro and in vivo …”

“…1 Preclinical studies in solid tumor models have shown that prexasertib as a single agent, or in combination with other agents, has both in vitro and in vivo antitumor activity. 1,9,10 Prexasertib, in combination with cetuximab and irradiation, has also been shown to have antitumor effects in head and neck squamous cell carcinoma (SCC) in vitro and in vivo. 11 A phase 1 nonrandomized, open-label, dose-escalation study of prexasertib monotherapy, conducted in the US in 45 patients with advanced solid tumors, resulted in a recommended prexasertib dose of 105 mg/m 2 administered once every 14 days for further evaluation.…”