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The DNA-PK complex is activated by double-strand DNA breaks and regulates the non-homologous end-joining repair pathway; thus, targeting DNA-PK by inhibiting the DNA-PK catalytic subunit (DNA-PKcs) is potentially a useful therapeutic approach for oncology. A previously reported series of neutral DNA-PKcs inhibitors were modified to incorporate a basic group, with the rationale that increasing the volume of distribution while maintaining good metabolic stability should increase the half-life. However, adding a basic group introduced hERG activity, and basic compounds with modest hERG activity (IC

Supplementary Information

U87/Centrin2-EGFP/H2B-mCherry/puro cells were seeded on dishes with cover slip bottoms, treated with AZ32 (3 uM), and irradiated (5 Gy). Time-lapse videos were recorded intermittently (every 7 min) over 16 hrs. Treatment results in 11% aberrant mitoses (see Fig. 3F).

Supplementary Data from The DNA-PK Inhibitor AZD7648 Sensitizes Patient-Derived Ovarian Cancer Xenografts to Pegylated Liposomal Doxorubicin and Olaparib Preventing Abdominal Metastases

Ovarian cancer is the deadliest gynecologic cancer, with a 5-year survival rate of 30%, when the disease has spread throughout the peritoneal cavity.We investigated the efficacy to delay disease progression by the DNA-dependent protein kinase (DNA-PK) inhibitor AZD7648, administered in combination with two of the therapeutic options for patient management: either pegylated liposomal doxorubicin (PLD) or the PARP inhibitor olaparib. Patient-derived ovarian cancer xenografts (OC-PDX) were transplanted subcutaneously to evaluate the effect of treatment on tumor growth, or orthotopically in the peritoneal cavity to evaluate the effect on metastatic spread. AZD7648 was administered orally in combination with PLD (dosed intravenously) or with olaparib (orally). To prove the inhibition of DNA-PK in the tumors, we measured pDNA-PKcs, pRPA32, and γH2AX, biomarkers of DNA-PK activity.AZD7648 enhanced the therapeutic efficacy of PLD in all the OC-PDXs tested, regardless of their BRCA status or sensitivity to cisplatin or PLD. The treatment caused disease stabilization, which persisted despite therapy discontinuation for tumors growing subcutaneously, and significantly impaired the abdominal metastatic dissemination, prolonging the lifespan of mice implanted orthotopically.AZD7648 potentiated the efficacy of olaparib in BRCA-deficient OC-PDXs but did not sensitize BRCA-proficient OC-PDXs to olaparib, despite an equivalent inhibition of DNA-PK, suggesting the need of a preexisting olaparib activity to benefit from the addition of AZD7648.This work suggests that AZD7648, an inhibitor of DNA-PK, dosed in combination with PLD or olaparib is an exciting therapeutic option that could benefit patients with ovarian cancer and should be explored in clinical trials.

U87/shp53/Centrin2-EGFP/H2B-mCherry/shp53 cells were seeded on dishes with cover slip bottoms and irradiated (5 Gy). Time-lapse videos were recorded intermittently (every 7 min) over 16 hrs. Treatment results in 12% aberrant mitoses (see Fig. 3F).

U87/Centrin2-EGFP/H2B-mCherry/puro cells were seeded on dishes with cover slip bottoms and irradiated (5 Gy). Time-lapse videos were recorded intermittently (every 7 min) over 16 hrs. Treatment results in 2.7% aberrant mitoses (see Fig. 3F).

Inhibition of ataxia-telangiectasia mutated (ATM) during radiotherapy of glioblastoma multiforme (GBM) may improve tumor control by short-circuiting the response to radiation-induced DNA damage. A major impediment for clinical implementation is that current inhibitors have limited central nervous system (CNS) bioavailability; thus, the goal was to identify ATM inhibitors (ATMi) with improved CNS penetration. Drug screens and refinement of lead compounds identified AZ31 and AZ32. The compounds were then tested in vivo for efficacy and impact on tumor and healthy brain. Both AZ31 and AZ32 blocked the DNA damage response and radiosensitized GBM cells in vitro. AZ32, with enhanced blood–brain barrier (BBB) penetration, was highly efficient in vivo as radiosensitizer in syngeneic and human, orthotopic mouse glioma model compared with AZ31. Furthermore, human glioma cell lines expressing mutant p53 or having checkpoint-defective mutations were particularly sensitive to ATMi radiosensitization. The mechanism for this p53 effect involves a propensity to undergo mitotic catastrophe relative to cells with wild-type p53. In vivo, apoptosis was >6-fold higher in tumor relative to healthy brain after exposure to AZ32 and low-dose radiation. AZ32 is the first ATMi with oral bioavailability shown to radiosensitize glioma and improve survival in orthotopic mouse models. These findings support the development of a clinical-grade, BBB-penetrating ATMi for the treatment of GBM. Importantly, because many GBMs have defective p53 signaling, the use of an ATMi concurrent with standard radiotherapy is expected to be cancer-specific, increase the therapeutic ratio, and maintain full therapeutic effect at lower radiation doses. Mol Cancer Ther; 17(8); 1637–47. ©2018 AACR.

Ovarian cancer is the deadliest gynecologic cancer, with a 5-year survival rate of 30%, when the disease has spread throughout the peritoneal cavity. We investigated the efficacy to delay disease progression by the DNA-dependent protein kinase (DNA-PK) inhibitor AZD7648, administered in combination with two of the therapeutic options for patient management: either pegylated liposomal doxorubicin (PLD) or the PARP inhibitor olaparib. Patient-derived ovarian cancer xenografts (OC-PDX) were transplanted subcutaneously to evaluate the effect of treatment on tumor growth, or orthotopically in the peritoneal cavity to evaluate the effect on metastatic spread. AZD7648 was administered orally in combination with PLD (dosed intravenously) or with olaparib (orally). To prove the inhibition of DNA-PK in the tumors, we measured pDNA-PKcs, pRPA32, and γH2AX, biomarkers of DNA-PK activity. AZD7648 enhanced the therapeutic efficacy of PLD in all the OC-PDXs tested, regardless of their BRCA status or sensitivity to cisplatin or PLD. The treatment caused disease stabilization, which persisted despite therapy discontinuation for tumors growing subcutaneously, and significantly impaired the abdominal metastatic dissemination, prolonging the lifespan of mice implanted orthotopically. AZD7648 potentiated the efficacy of olaparib in BRCA-deficient OC-PDXs but did not sensitize BRCA-proficient OC-PDXs to olaparib, despite an equivalent inhibition of DNA-PK, suggesting the need of a preexisting olaparib activity to benefit from the addition of AZD7648. This work suggests that AZD7648, an inhibitor of DNA-PK, dosed in combination with PLD or olaparib is an exciting therapeutic option that could benefit patients with ovarian cancer and should be explored in clinical trials.

Background AZD0156 is an oral inhibitor of ATM, a serine threonine kinase that plays a key role in DNA damage response (DDR) associated with double-strand breaks. Topoisomerase-I inhibitor irinotecan is used clinically to treat colorectal cancer (CRC), often in combination with 5-fluorouracil (5FU). AZD0156 in combination with irinotecan and 5FU was evaluated in preclinical models of CRC to determine whether low doses of AZD0156 enhance the cytotoxicity of irinotecan in chemotherapy regimens used in the clinic. Methods Anti-proliferative effects of single-agent AZD0156, the active metabolite of irinotecan (SN38), and combination therapy were evaluated in 12 CRC cell lines. Additional assessment with clonogenic assay, cell cycle analysis, and immunoblotting were performed in 4 selected cell lines. Four colorectal cancer patient derived xenograft (PDX) models were treated with AZD0156, irinotecan, or 5FU alone and in combination for assessment of tumor growth inhibition (TGI). Immunofluorescence was performed on tumor tissues. The DDR mutation profile was compared across in vitro and in vivo models. Results Enhanced effects on cellular proliferation and regrowth were observed with the combination of AZD0156 and SN38 in select models. In cell cycle analysis of these models, increased G2/M arrest was observed with combination treatment over either single agent. Immunoblotting results suggest an increase in DDR associated with irinotecan therapy, with a reduced effect noted when combined with AZD0156, which is more pronounced in some models. Increased TGI was observed with the combination of AZD0156 and irinotecan as compared to single-agent therapy in some PDX models. The DDR mutation profile was variable across models. Conclusions AZD0156 and irinotecan provide a rational and active combination in preclinical colorectal cancer models. Variability across in vivo and in vitro results may be related to the variable DDR mutation profiles of the models evaluated. Further understanding of the implications of individual DDR mutation profiles may help better identify patients more likely to benefit from treatment with the combination of AZD0156 and irinotecan in the clinical setting.

DNA-dependent kinase (DNA-PK) is a nuclear serine/threonine protein kinase complex that is a key component of the non-homologous end joining (NHEJ) process. DNA-PK plays an important role in the cellular response to DNA damage through the detection and repair of DNA double strand breaks (DSB). Cancer therapies such as ionising radiation (IR) or topoisomerase II inhibitors (doxorubicin) generate DSB which can be repaired by homologous recombination (HR) or non-homologous end-joining (NHEJ). It can therefore be hypothesised a DNA-PK inhibitor would potentiate the activity of these agents. We have developed a highly potent and selective inhibitor of DNA-PK, AZD7648, which inhibits IR-induced DNA-PK S2056 auto phosphoryalation with an IC50 = 92 nM in A549 non-small cell lung cancer (NSCLC) cells. AZD7648 is a potent radiosensitiser where treatment in combination with IR led to a concentration-dependent reduction of the colony survival capacity of A549 and H1299 NSCLC cells (DEF37 at 100 nM = 1.7 and 2.5, respectively). In A549 cells, AZD7648 (≥1 µM) in combination with 2Gy IR for 48 hours led to a significant accumulation of cells arrested in the G2/M of the cell cycle, a 4-fold increase in micronuclei formation, and 3-fold induction of γH2AX, pATM S1981 and 53BP1 foci formation compared with IR alone. AZD7648 was also found to combine synergistically with doxorubicin in a panel of ovarian and triple negative breast cancer (TNBC) cell lines in cell growth inhibition assays when applying the Loewe additivity model (synergy scores 4 - 35). In vivo the combination of AZD7648 with IR (5x 2Gy) induced tumour regression in H1299 and A549 NSCLC xenografts in a dose-dependent manner (84 and 11% regression respectively), while monotherapy treatment only achieved tumour growth inhibition. In these two models the increased activation by IR of three primary DNA-PK pharmacodynamic markers, pDNAPK (S2056), pRPA32 (S4/8) and γH2AX, was inhibited by AZD7648 treatment (70-90% inhibition 2 h after IR + AZD7648). Similarly, liposomal doxorubicin (2.5 mg/kg weekly) in combination with AZD7648 (37.5 mg/kg bid) induced tumour regressions in the BT474c ER+ breast cancer xenograft model and in a TNBC PDX model (63% and 33% regression respectively), while monotherapy treatments only achieved tumour growth inhibition. These data confirm that DNA-PK inhibition with AZD7648 enhances the efficacy of a range of DSB inducing agents in vitro and in vivo, providing a clear rationale for its clinical investigation. Citation Format: Jacqueline H. Fok, Antonio Ramos-Montoya, Neil James, Mercedes Vazquez-Chantada, Valeria Follia, Ankur Karmokar, Anna Staniszewska, Lenka Oplustil O’Connor, Emma Dean, Simon J. Hollingsworth, Barry R. Davies, Elaine B. Cadogan. AZD7648, a potent and selective inhibitor of DNA-PK, potentiates the activity of ionising radiation and doxorubicin in vitro and causes tumour regression in xenograft models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3512.