PARP-7 ( IC50 = 3 nM ); PARP-7 ( Kd = 1 nM )

RBN-2397 (0.0001-100 μM; 24 hours) inhibits cell proliferation with an IC50 value of 20 nM in NCI-H1373 lung cancer cells[2].
RBN-2397 (0.4 nM-1 μM; 24 hours) restores the type I IFN response in NCI-H1373 human lung cancer cells through a dose-dependent increase in STAT1 phosphorylation[2].
RBN-2397 (0.0001-1 μM; 24 hours) inhibits cell MARylation, with an EC50 value of 1 nM in a cell biochemial assay[2].

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RBN-2397 inhibited PARP7 activity, decreasing α-tubulin MARylation, leading to its stabilization, and reducing cancer cell proliferation and migration. The addition of paclitaxel further enhanced these effects, highlighting a synergistic interaction between the two drugs. Mutating the site of PARP7-mediated MARylation on α-tubulin similarly resulted in microtubule stabilization and decreased cell migration in the presence of paclitaxel. Conclusions: This study demonstrates that targeting PARP7 with RBN-2397, particularly in combination with paclitaxel, offers an effective strategy for inhibiting aggressive ovarian cancer cell phenotypes. Our findings underscore the potential of combining PARP7 inhibitors with established chemotherapeutics to enhance treatment efficacy in ovarian cancer.[3]

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Polyadenosine diphosphate-ribose polymerase 7 (PARP7) acts as a suppressor of the type I interferon (IFN) signaling pathway via suppressing TANK-binding protein 1 (TBK1). Research study indicates that inhibition of PARP7 could potentially regulate tumor immunity. However, the effect of PARP7 inhibition on innate antiviral immunity in macrophages as well as the underlying mechanism have not been demonstrated else well. We report herein that PARP7 inhibitor clinical candidate RBN-2397 could augment type I interferon (IFN-I) production in macrophages by elevating retinoic acid-inducible gene I (RIG-I) and stimulator of interferon genes (STING) signaling pathways. Treatment with RBN-2397 leads to increased pattern recognition ligands-induced interferon-β production in primary bone marrow-derived macrophages (BMDM) and RAW264.7 cells. Additionally, RBN-2397 suppresses viral replication efficiency in macrophages infected by vesicular stomatitis virus (VSV) and amplifies the expression of interferon-stimulated chemokine genes (ISGs). Mechanistically, RBN-2397 promotes TBK1 phosphorylation, consequently leading to the amplified activation of RIG-I and STING signaling pathways. Furthermore, RBN-2397 enhances the phosphorylation of signal transducer and activator of transcription 1 (STAT1) and STAT2 induced by IFN-α/β and the expression of chemokine genes in macrophages in response to IFN stimulation. In vivo experiments demonstrated that RBN-2397 enhances innate antiviral immunity in mice infected with VSV, resulting in increased serum IFN-β levels, reduced viral loads, and alleviated pulmonary inflammatory responses of the VSV-infected mice. In conclusion, our findings highlight the potential of RBN-2397 as a promising antiviral therapeutic agent for enhancing the IFN-relative antiviral immune defense in host. [4]

RBN-2397 (oral administration; 3-100 mg/kg; once daily; 24-32 days) creates tumor-specific adaptive immune memory in CT26 syngeneic model in BALB/c mice bearing CT26 tumors, along with long-lasting full responses[2]. RBN-2397 (oral administration; 3-100 mg/kg; once daily; 32 days) inhibits tumor growth in a dose-dependent manner and causes complete regressions at 100 mg/kg at dose levels of ≥30 mg/kg[2]. RBN-2397 has a half-life (t1/2) of 325 minutes in vivo[2].

Cell Proliferation Assay[2]
Cell Line: NCI-H1373 lung cancer cells
Concentration: 0.0001 μM; 0.001 μM; 0.001 μM; 0.1 μM; 1 μM; 10 μM; 100 μM
Incubation Time: 24 hours
Result: Blocked cell proliferation.

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Western Blot Analysis[2]
Cell Line: NCI-H1373 lung cancer cells
Concentration: 0.4 nM-1 μM
Incubation Time: 24 hours
Result: Increased p-STAT1 protein expression.

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Ovarian cancer cell lines (OVCAR4, OVCAR3) were treated with RBN-2397 and paclitaxel, both separately and in combination. Western blotting and immunoprecipitation confirmed the effects of RBN-2397 on α-tubulin MARylation and stabilization. Cell proliferation and migration were assessed, and α-tubulin stabilization was quantified using immunofluorescent imaging. RNA-sequencing was performed to assess the effects on gene expression changes.[3]

CB17 SCID mice with NCI-H1373 xenografts
3 mg/kg, 10mg/kg, 30 mg/kg, 100 mg/kg
Oral administration; once daily; 24-32 days

[1]. RBN-2397-Inhibiting PARP7, a Key monoPARP Cancer Dependency.

[2]. RBN-2397: A First-in-Class PARP7 Inhibitor Targeting a Newly Discovered Cancer Vulnerability in Stress-Signaling Pathways.

[3]. RBN-2397, a PARP7 Inhibitor, Synergizes with Paclitaxel to Inhibit Proliferation and Migration of Ovarian Cancer Cells. bioRxiv. 2024 Sep 5:2024.08.20.608802.

[4]. PARP7i Clinical Candidate RBN-2397 Exerts Antiviral Activity by Modulating Interferon-β Associated Innate Immune Response in Macrophages. Drug Dev Res. 2024 Nov;85(7):e70013.

Atamparib is an orally administered small-molecule ribosome polymerase (ADP-ribose) 7 inhibitor with potential immunomodulatory and antitumor activities. After oral administration, atamparib selectively binds to PARP7, restoring type I interferon signaling. This may lead to the induction of innate and adaptive immune responses and inhibit tumor growth and proliferation. PARP catalyzes the post-translational ADP-ribosylation of nucleoproteins, which have signal transduction functions and recruit other proteins to repair damaged DNA. Mono(ADP-ribosylation) is a post-translational modification of proteins and is increasingly becoming an important regulator in cancer cell biology. PARP7 (TiPARP) is a mono(ADP-ribose)transferase (MART) that performs MARylation on its substrate α-tubulin in ovarian cancer cells, thereby promoting microtubule instability, cell growth, and migration. In recent years, the development of RBN-2397, a potent inhibitor that selectively acts on PARP7, has provided a new tool for exploring the role of PARP7 catalytic activity in biological processes. This study investigated the role of PARP7 catalytic activity in the biological regulation of ovarian cancer cells through α-tubulin marylation. [3]

C₂₀H₂₃F₆N₇O₃

523.43

523.18

C, 45.89; H, 4.43; F, 21.78; N, 18.73; O, 9.17

2381037-82-5

146047148

White to off-white solid powder

1.53±0.1 g/cm3(Predicted)

1.2

2

14

8

36

848

1

FC(C1C([H])=NC(=NC=1[H])N1C([H])([H])C([H])([H])N(C(C([H])([H])C([H])([H])OC([H])([H])[C@]([H])(C([H])([H])[H])N([H])C2C([H])=NN([H])C(C=2C(F)(F)F)=O)=O)C([H])([H])C1([H])[H])(F)F

UQZCQKXJAXKZQH-LBPRGKRZSA-N

InChI=1S/C20H23F6N7O3/c1-12(30-14-10-29-31-17(35)16(14)20(24,25)26)11-36-7-2-15(34)32-3-5-33(6-4-32)18-27-8-13(9-28-18)19(21,22)23/h8-10,12H,2-7,11H2,1H3,(H2,30,31,35)/t12-/m0/s1

4-[[(2S)-1-[3-oxo-3-[4-[5-(trifluoromethyl)pyrimidin-2-yl]piperazin-1-yl]propoxy]propan-2-yl]amino]-5-(trifluoromethyl)-1H-pyridazin-6-one

RBN2397; RBN 2397; Atamparib; RBN-2397

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO: 100~200 mg/mL (191.0~382.1 mM)
Ethanol: ~13 mg/mL

Solubility in Formulation 1: ≥ 2.5 mg/mL (4.78 mM) (saturation unknown) in 5% DMSO + 95% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (3.97 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (3.97 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 4: ≥ 2.08 mg/mL (3.97 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL corn oil and mix evenly.

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Solubility in Formulation 5: ≥ 0.5 mg/mL (0.96 mM) (saturation unknown) in 1% DMSO 99% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 6: 5%DMSO+ 40%PEG300+ 5%Tween 80+ 50%ddH2O: 5.0mg/ml (9.55mM)

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 (Please use freshly prepared in vivo formulations for optimal results.)