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Synergistic Effect of a HER2 Targeted Thorium-227 Conjugate in Combination with Olaparib in a BRCA2 Deficient Xenograft Model.

ABSTRACT: Targeted thorium-227 conjugates (TTCs) represent a novel class of therapeutic radiopharmaceuticals for the treatment of cancer. TTCs consist of the alpha particle emitter thorium-227 complexed to a 3,2-hydroxypyridinone chelator conjugated to a tumor-targeting monoclonal antibody. The high energy and short range of the alpha particles induce potent and selective anti-tumor activity driven by the induction of DNA damage in the target cell. Methods: The efficacy of human epidermal growth factor receptor 2 (HER2)-TTC was tested in combination in vitro and in vivo with the poly ADP ribose polymerase (PARP) inhibitor (PARPi), olaparib, in the human colorectal adenocarcinoma isogenic cell line pair DLD-1 and the knockout variant DLD-1 BRCA2 -/- Results: The in vitro combination effects were determined to be synergistic in DLD-1 BRCA2 -/- and additive in DLD-1 parental cell lines. Similarly, the in vivo efficacy of the combination was determined to be synergistic only in the DLD-1 BRCA2 -/- xenograft model, with statistically significant tumor growth inhibition at a single TTC dose of 120 kBq/kg body weight (bw) and 50 mg/kg bw olaparib (daily, i.p. for 4 weeks), demonstrating comparable tumor growth inhibition to a single TTC dose of 600 kBq/kg bw. Conclusions: This study supports the further investigation of DNA damage response inhibitors in combination with TTCs as a new strategy for the effective treatment of mutation-associated cancers.

SUBMITTER: Wickstroem K

PROVIDER: S-EPMC6958469 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Synergistic Effect of a HER2 Targeted Thorium-227 Conjugate in Combination with Olaparib in a BRCA2 Deficient Xenograft Model.

Wickstroem Katrine K Karlsson Jenny J Ellingsen Christine C Cruciani Véronique V Kristian Alexander A Hagemann Urs B UB Bjerke Roger M RM Ryan Olav B OB Linden Lars L Mumberg Dominik D Brands Michael M Cuthbertson Alan A

Pharmaceuticals (Basel, Switzerland) 20191015 4

Targeted thorium-227 conjugates (TTCs) represent a novel class of therapeutic radiopharmaceuticals for the treatment of cancer. TTCs consist of the alpha particle emitter thorium-227 complexed to a 3,2-hydroxypyridinone chelator conjugated to a tumor-targeting monoclonal antibody. The high energy and short range of the alpha particles induce potent and selective anti-tumor activity driven by the induction of DNA damage in the target cell. Methods: The efficacy of human epidermal growth factor re ...[more]

PMID: 31618864

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Project description:Targeted 227Th conjugates (TTCs) represent a new class of therapeutic radiopharmaceuticals for targeted α-therapy. They comprise the α-emitter 227Th complexed to a 3,2-hydroxypyridinone chelator conjugated to a tumor-targeting monoclonal antibody. The high energy and short range of the α-particles induce antitumor activity, driven by the induction of complex DNA double-strand breaks. We hypothesized that blocking the DNA damage response (DDR) pathway should further sensitize cancer cells by inhibiting DNA repair, thereby increasing the response to TTCs. Methods: This article reports the evaluation of the mesothelin (MSLN)-TTC conjugate (BAY 2287411) in combination with several DDR inhibitors, each of them blocking different DDR pathway enzymes. MSLN is a validated cancer target known to be overexpressed in mesothelioma, ovarian, lung, breast, and pancreatic cancer, with low expression in normal tissue. In vitro cytotoxicity experiments were performed on cancer cell lines by combining the MSLN-TTC with inhibitors of ataxia telangiectasia mutated, ataxia telangiectasia and Rad3-related (ATR), DNA-dependent protein kinase, and poly[adenosine diphosphate ribose] polymerase (PARP) 1/2. Further, we evaluated the antitumor efficacy of the MSLN-TTC in combination with DDR inhibitors in human ovarian cancer xenograft models. Results: Synergistic activity was observed in vitro for all tested inhibitors (inhibitors are denoted herein by the suffix "i") when combined with MSLN-TTC. ATRi and PARPi appeared to induce the strongest increase in potency. Further, in vivo antitumor efficacy of the MSLN-TTC in combination with ATRi or PARPi was investigated in the OVCAR-3 and OVCAR-8 xenograft models in nude mice, demonstrating synergistic antitumor activity for the ATRi combination at doses demonstrated to be nonefficacious when administered as monotherapy. Conclusion: The presented data support the mechanism-based rationale for combining the MSLN-TTC with DDR inhibitors as new treatment strategies in MSLN-positive ovarian cancer.

Project description:Ovarian cancer is the most lethal type of gynecological cancer. Due to its high heterogeneity and complicated pathological mechanisms, the 5-year survival rate of patients with ovarian cancer is <40%. Tumor cytoreductive surgery and systemic chemotherapy of platinum combined with paclitaxel are currently considered the gold standard for the treatment of ovarian cancer, and chemotherapy resistance has become a key constraint in improving the cure rate of ovarian cancer. Therefore, it is important to identify novel treatment methods and strategies for ovarian cancer. Targeted drugs can not only be used in combination with chemotherapy, but also act as maintenance therapy to promote patient survival time. PARP inhibitor is a novel type of ovarian cancer treatment targeted drug, which can induce an anticancer effect by inhibiting DNA damage and repair of ovarian cancer cells. The present study investigated the different effects of olaparib, cisplatin and paclitaxel in several dosages by single use and combinations on the proliferation of different human ovarian cancer cell lines, in order to verify the synergistic effects of the combinations of the three anticancer agents in pairs. The proliferation inhibitory rate of the cell lines was determined using a Cell Counting Kit-8 assay, while the combination index (CI) value of the combination of three agents in pairs was analyzed using Compusyn software. The proliferation was observed using a crystal violet assay, and the apoptosis ratio was measured via flow cytometry. The results of the present study revealed that the combination of cisplatin with olaparib group had a higher inhibition effect than each single group and had a higher dose-reduction index of >1 than the other two combinations at all concentrations in A2780 and OVCAR-3 cell lines. The difference in proliferation inhibition and induced apoptosis rate of A2780 cell lines was significant in the combination of cisplatin with olaparib group and the control group (P<0.01) at 0.25x IC50. For the OVCAR-3 cell line, the difference was also significant between two groups (P<0.05). The CI values in the A2780 cell line revealed significant differences between the low-dose group (0.0625x, 0.125x and 0.25x IC50) and the high-dose group (0.5x, 1.0x and 2.0x IC50) for the group that received the combination of cisplatin with olaparib (P<0.05). The present study highlighted that the group receiving a combination of cisplatin with olaparib exhibited the most significant synergistic effects among the three combinations, particularly at low doses.

Dataset Information

Synergistic Effect of a HER2 Targeted Thorium-227 Conjugate in Combination with Olaparib in a BRCA2 Deficient Xenograft Model.

Publications

Synergistic Effect of a HER2 Targeted Thorium-227 Conjugate in Combination with Olaparib in a BRCA2 Deficient Xenograft Model.

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