Pharmacologic Inhibitor of DNA-PK, M3814, Potentiates Radiotherapy and Regresses Human Tumors in Mouse Models

Abstract

Physical and chemical DNA-damaging agents are used widely in the treatment of cancer. Double-strand break (DSB) lesions in DNA are the most deleterious form of damage and, if left unrepaired, can effectively kill cancer cells. DNA-dependent protein kinase (DNA-PK) is a critical component of nonhomologous end joining (NHEJ), one of the two major pathways for DSB repair. Although DNA-PK has been considered an attractive target for cancer therapy, the development of pharmacologic DNA-PK inhibitors for clinical use has been lagging. Here, we report the discovery and characterization of a potent, selective, and orally bioavailable DNA-PK inhibitor, M3814 (peposertib), and provide in vivo proof of principle for DNA-PK inhibition as a novel approach to combination radiotherapy. M3814 potently inhibits DNA-PK catalytic activity and sensitizes multiple cancer cell lines to ionizing radiation (IR) and DSB-inducing agents. Inhibition of DNA-PK autophosphorylation in cancer cells or xenograft tumors led to an increased number of persistent DSBs. Oral administration of M3814 to two xenograft models of human cancer, using a clinically established 6-week fractionated radiation schedule, strongly potentiated the antitumor activity of IR and led to complete tumor regression at nontoxic doses. Our results strongly support DNA-PK inhibition as a novel approach for the combination radiotherapy of cancer. M3814 is currently under investigation in combination with radiotherapy in clinical trials.

A first-in-man phase 1 study of the DNA-dependent protein kinase inhibitor peposertib (formerly M3814) in patients with advanced solid tumours

“…Here, we report the first-in-human study evaluating a DNA-PK inhibitor in patients with advanced cancer. Single-agent peposertib, a potent and selective inhibitor of the DNA-PK catalytic activity, [6][7][8][9][10] was well-tolerated when given orally QD or BID to patients with advanced solid tumours. The maximum administered dose was 400 mg BID, and this was also declared the RP2D in monotherapy, based on the achieved predicted exposure −efficacy relationship, and evidence of target engagement.…”

“…This RP2D was further supported by the exposure levels observed at 400 mg BID to be in the expected range of target engagement. 8 Six aspirin-naïve patients (see above) were enrolled at the RP2D to confirm the safety and tolerability and to the effects of peposertib in platelet aggregation. The lack of objective responses or clearly identifiable efficacy signals in the patients treated precluded the initiation of the dose-expansion cohort of the study.…”

“…by preventing the repair of radiation-or chemotherapy-induced DNA DSBs via the NHEJ pathway. [6][7][8][9][10] The purpose of this first-in-man, open-label, phase 1 trial (NCT02316197) was to determine the maximum-tolerated dose (MTD) and/or the recommended phase 2 dose (RP2D) of peposertib. To our knowledge, this is the first full report of an oral DNA-PK inhibitor in humans.…”

Discovery and development of novel DNA-PK inhibitors by targeting the unique Ku–DNA interaction

“…Thus, DNA-PK inhibitors are currently being assessed in combination with chemo- and radiotherapy and as single agents in certain DNA repair deficient cancers. Recent development of more specific and potent inhibitors has resulted in FDA approval to initiate Phase I clinical trials as a potential cancer therapeutic ( 45 ). Even with these successes moving forward in the clinic, active site targeted agents have limitations including specificity due to conserved catalytic mechanisms across kinase families, similar structural features of active sites, and the high intracellular ATP concentrations relative to the cellular concentrations of kinase inhibitors.…”

Combining PARP and DNA-PK Inhibitors With Irradiation Inhibits HPV-Negative Head and Neck Cancer Squamous Carcinoma Growth

“…Similarly, inhibition of deoxyribonucleic acid protein kinase catalytic subunit (DNA-Pk CS ), a key player in the DSB non-homologous end joining (NHEJ) repair also radiosensitizes cells ( Azad et al, 2014 ; Ying et al, 2016 ; Brown et al, 2017 ; Lee et al, 2019 ). NHEJ is involved in ~80% of DSB repairs induced by radiation in cancer cells ( Kakarougkas and Jeggo, 2014 ), and DNA-Pk cs inhibitors, such as the oral inhibitor M3814, can potentiate the antitumor activity of IR in HNSCC cell lines in vivo ( Zenke et al, 2020 ).…”