Preclinical pharmacokinetics and metabolism of a novel prototype DNA-PK inhibitor NU7026

Abstract

In this study we investigated the in vitro time dependence of radiosensitisation, pharmacokinetics and metabolism of NU7026, a novel inhibitor of the DNA repair enzyme DNA-dependent protein kinase (DNA-PK). At a dose of 10 mM, which is nontoxic to cells per se, a minimum NU7026 exposure of 4 h in combination with 3 Gy radiation is required for a significant radiosensitisation effect in CH1 human ovarian cancer cells. Following intravenous administration to mice at 5 mg kg À1 , NU7026 underwent rapid plasma clearance (0.108 l h À1 ) and this was largely attributed to extensive metabolism. Bioavailability following interperitoneal (i.p.) and p.o. administration at 20 mg kg À1 was 20 and 15%, respectively. Investigation of NU7026 metabolism profiles in plasma and urine indicated that the compound undergoes multiple hydroxylations. A glucuronide conjugate of a bis-hydroxylated metabolite represented the major excretion product in urine. Identification of the major oxidation site as C-2 of the morpholine ring was confirmed by the fact that the plasma clearance of NU7107 (an analogue of NU7026 methylated at C-2 and C-6 of the morpholine ring) was four-fold slower than that of NU7026. The pharmacokinetic simulations performed predict that NU7026 will have to be administered four times per day at 100 mg kg À1 i.p. in order to obtain the drug exposure required for radiosensitisation.

In Vivo Analysis of Protein Kinase B (PKB)/Akt Regulation in DNA-PKcs-null Mice Reveals a Role for PKB/Akt in DNA Damage Response and Tumorigenesis

“…It is plausible that PKB hyperactivity in the thymus in the absence of DNA-PK could be mediated by mTORC2, and tissue-specific disruption of the PKB/FoxO pathway could render DNA-PK-deficient thymic lymphomas susceptible to rapamycin treatment. A number of small molecule inhibitors of DNA-PK have been developed, and the inhibition of DNA-PK sensitizes cells to DNA-damaging agents (77,78). However, the use of DNA-PK inhibitors needs to be evaluated cautiously in the treatment of thymic lymphomas as loss of DNA-PK activity could lead to increased PKB signaling.…”

Role of Gadd45a in Wip1-dependent regulation of intestinal tumorigenesis

“…Mice were injected i.p. with the Rapamycin 37 (Sigma-Aldrich, St. Louis, MO, USA, #R0395) 7.5 mg per kg of body weight in 5% DMSO or AKT inhibitor 38 (NSC 154020, Calbiochem, Millipore) 20 mg per kg of body weight in 5% DMSO or ATM inhibitor (KU55933, Calbiochem, Millipore) 15 mg per kg of body weight in 5% DMSO or DNA-PK inhibitor 39 (NU7026, Sigma-Aldrich) 15 mg per kg of body weight in 5% DMSO or p38MAPK inhibitor 12 (SB202190, SigmaAldrich) 10 mg per kg of body weight in 5% DMSO, or GSK-3 inhibitors IX 6 (Calbiochem, Millipore) 15 mg per kg of body weight in 5% DMSO. After 6, 10, or 12 h, mice were euthanized and organs were collected for subsequent analysis.…”

Chemical inhibition of DNA repair kinases as a promising tool in oncology

“…Nutley et al determined that NU7026 potentiated the effects of IR, although predominantly after prolonged exposure i.e. 6 or 24 h. Hence, the most intensive effects of NU7026 will be hardly achievable in vivo because the level of NU7026 was undetectable 4 h after application 56 . NU7441, another inhibitor from chromenone library, is the most potent and selective inhibitor of DNA-PK so far, with IC 50 : 14 nM, it is 100-fold more selective inhibitor of DNA-PK in comparison to other PI3-K kinases 52,60 .…”

“…Unlike wortmannin or LY294002, NU7026 had no effect on PI3-K (ref. 56 ). Cells treated with etoposide and NU7026 showed G 2 /M cell cycle arrest 59 .…”

“…NU7026, an inhibitor from chromenone library, is a cell permeable, ATP-competitive inhibitor of DNA-PK and ATM, but predominantly affects DNA-PK with IC 50 : 0,23 μM, IC 50 for ATM is more than 100 μM (ref. 56,57 ). Tichy et al observed the complete growth inhibition of leukemic cells after combination of 10 μM NU7026 and the dose of 1 Gy.…”