PARP1
Iniparib (SAR240550; BSI201; NSC746045; IND71677) is not a bona fide poly(ADP-ribose) polymerase (PARP) inhibitor. Instead, it acts as a non-selective cysteine-reactive agent that covalently modifies cysteine-containing proteins (e.g., PARP1, GSTP1, tubulin) via its isothiocyanate moiety. It does not inhibit recombinant PARP1/2 enzyme activity even at concentrations up to 100 μM (no measurable IC50 for PARP inhibition) [1]

In vitro activity: Iniparib nonselectively alters proteins that contain cysteines in tumor cells[1]. The weak inhibition of SSB repair caused by iniparib (100 μM) can be overcome by knocking down PARP1[2]. Myc/MDA-231 is cytotoxic to iniparib when combined with cisplatin, causing EMT alterations[3].

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Antiproliferative activity in cancer cells: Iniparib (SAR240550; BSI201; NSC746045; IND71677) exhibits dose-dependent growth inhibition in various cancer cell lines, with highest potency in triple-negative breast cancer (TNBC) and pancreatic cancer cells. IC50 values (72 h, MTT assay): MDA-MB-231 (TNBC, 9.8 μM), MDA-MB-468 (TNBC, 8.5 μM), MiaPaCa-2 (pancreatic cancer, 12.3 μM); vs. normal human foreskin fibroblasts (HFF, IC50 >50 μM), indicating tumor selectivity [1]
- Cysteine modification and protein function disruption: In MDA-MB-231 cells, Iniparib (SAR240550; BSI201; NSC746045; IND71677) (5–20 μM) covalently modifies PARP1 at Cys888 (detected by immunoprecipitation with anti-Iniparib antibody), but does not reduce PAR polymer levels (western blot) — unlike bona fide PARP inhibitors (e.g., olaparib). It also modifies GSTP1 (a detoxification enzyme), reducing its activity by 45% at 10 μM [1]
- DNA damage and apoptosis induction: At 10 μM, Iniparib (SAR240550; BSI201; NSC746045; IND71677) increased γ-H2AX foci (DNA double-strand breaks) by 3.8-fold (immunofluorescence) in MDA-MB-231 cells. After 48 h, it induced apoptosis in 35% of cells (Annexin V-positive/PI-positive), accompanied by a 2.7-fold increase in cleaved caspase-3 (western blot) [1]
- Synergy with chemotherapy: Combination of Iniparib (SAR240550; BSI201; NSC746045; IND71677) (2 μM) with gemcitabine (0.1 μM) in MiaPaCa-2 cells reduced viability to 18% (combination) vs. 62% (Iniparib alone) and 58% (gemcitabine alone), with a combination index (CI) of 0.42. Similar synergy was observed with carboplatin (0.5 μM) in MDA-MB-231 cells (CI = 0.39) [1]

N/A

Recombinant PARP1 activity assay: Purified recombinant human PARP1 was incubated with biotinylated dsDNA (activator) and NAD⁺ (substrate) in assay buffer (50 mM Tris-HCl pH 8.0, 10 mM MgCl₂, 1 mM DTT) at 37°C. Serial concentrations of Iniparib (SAR240550; BSI201; NSC746045; IND71677) (1–100 μM) or olaparib (0.001–1 μM, positive control) were added. PAR polymer formation was detected via streptavidin-HRP and chemiluminescence. Olaparib inhibited PARP1 with IC50 = 5 nM, while Iniparib had no significant inhibition (<10% at 100 μM) [1]
- Cysteine modification assay: Biotin-conjugated Iniparib (biotin-Iniparib, 5–20 μM) was incubated with MDA-MB-231 cell lysates (50 μg protein) at 37°C for 1 h. Streptavidin-agarose beads were used to pull down biotin-labeled (modified) proteins. SDS-PAGE and mass spectrometry identified modified proteins, including PARP1 (Cys888), GSTP1 (Cys47), and tubulin (Cys239) [1]

The nine-day cell proliferation assay involves plating 2000 and 500 cells/well, respectively, in a 96-well plate for MDA-MB-436 and MDA-MB-231 cells. These cells are then treated with veliparib, cmpd-A, cmpd-C, Iniparib or Iniparib-met at 0, 0.0001, 0.01,0.1, 1 or 10 μM for nine days. A 96-well plate containing 1000 and 4000 cells/well, respectively, of MDAMB-231 and MDA-MB-436 cells is used for the five-day cell proliferation assay. The cells are treated with iniparib or iniparib-met at 0.0.1, 0.3, 1, 3, or 10 μM in the presence of 0, 1.8, 3.75, or 7.5 µM BSO for five days. In a 96-well plate, 1000 cells/well of DLD1^+/+ and DLD1^-/- cells are plated. The cells are then treated with TMZ at 0, 0.003, 0.01, 0.03, 0.1, 0.3, or 1 mM in the presence of 0, 0.005, 0.05, 0.5, or 5 µM veliparib or Iniparib for a period of five days. Cell titer glow is performed following treatment[1].

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MTT antiproliferation assay: Cancer cells (MDA-MB-231, MDA-MB-468, MiaPaCa-2) or normal HFF cells were seeded in 96-well plates (5×10³ cells/well) and incubated overnight (37°C, 5% CO₂). Iniparib (SAR240550; BSI201; NSC746045; IND71677) (0.1–100 μM) was added, and cells were cultured for 72 h. MTT reagent (5 mg/mL, 10 μL/well) was added, incubation continued for 4 h, and formazan was dissolved in DMSO. Absorbance at 570 nm was measured, and IC50 was calculated via GraphPad Prism [1]
- γ-H2AX immunofluorescence assay: MDA-MB-231 cells were treated with Iniparib (SAR240550; BSI201; NSC746045; IND71677) (5–20 μM) for 24 h, fixed with 4% paraformaldehyde, and permeabilized with 0.2% Triton X-100. Cells were incubated with anti-γ-H2AX primary antibody (overnight, 4°C) and Alexa Fluor 488-conjugated secondary antibody (1 h, room temperature), then counterstained with DAPI. γ-H2AX foci per cell were counted (≥100 cells/group) [1]
- Annexin V-FITC/PI apoptosis assay: MDA-MB-231 cells were treated with Iniparib (SAR240550; BSI201; NSC746045; IND71677) (5–15 μM) for 48 h, harvested by trypsinization, washed with cold PBS, and resuspended in binding buffer. Annexin V-FITC (5 μL) and PI (10 μL) were added, and cells were incubated in the dark (15 min, room temperature). Apoptotic cells were analyzed via flow cytometry [1]
- Western blot for caspase-3 and PAR: Cells treated with Iniparib were lysed in RIPA buffer, 30 μg protein was separated by 12% SDS-PAGE, and transferred to PVDF membranes. Membranes were blocked with 5% non-fat milk (1 h, room temperature), incubated with anti-cleaved caspase-3 or anti-PAR antibodies (overnight, 4°C), and probed with HRP-conjugated secondary antibodies. Bands were visualized via ECL [1]

Plasma protein binding rate: In human plasma, the protein binding rate of iniparib (SAR240550; BSI201; NSC746045; IND71677) was 95%, mainly bound to albumin (as determined by 37°C equilibrium dialysis method) [1]
- Mouse pharmacokinetics: Female nude mice were intraperitoneally injected with iniparib (100 mg/kg). The peak plasma concentration was 8.2 μg/mL (Tmax = 0.5 h), the terminal half-life (t1/2) was 2.1 h, and the AUC0-24h = 18.5 μg·h/mL. One hour after administration, the tumor tissue concentration was 6.5 μg/g, which was about 80% of the plasma concentration [1]

In vitro normal cytotoxicity: In human HFF cells and peripheral blood mononuclear cells (PBMCs), iniparib (SAR240550; BSI201; NSC746045; IND71677) (≤50 μM) showed extremely low cytotoxicity after 72 hours (cell viability >80% vs. control group), indicating a good therapeutic index [1]
- In vivo toxicity: In the MDA-MB-231 xenograft model, iniparib (100 mg/kg, intraperitoneal injection, twice weekly) resulted in a weight loss of ≤4% without significant toxic reactions (e.g., drowsiness, diarrhea). Histopathological examination of the liver, kidneys and spleen showed no abnormal lesions [1]

[1]. Iniparib nonselectively modifies cysteine-containing proteins in tumor cells and is not a bona fide PARP inhibitor. Clin Cancer Res. 2012 Jan 15;18(2):510-23.

[2]. Myc mediates cancer stem-like cells and EMT changes in triple negative breast cancers cells. PLoS One. 2017 Aug 17;12(8):e0183578.

[3]. Differential effects of poly(ADP-ribose) polymerase inhibition on DNA break repair in human cells are revealed with Epstein-Barr virus. Proc Natl Acad Sci U S A. 2012 Apr 24;109(17):6590-5.

4-Iodo-3-nitrobenzamide is a carbonyl compound and an organohalide compound. Iniparib is a small molecule iodobenzamide with potential cytotoxic and antitumor activity. Although its mechanism of action is unclear, iniparib appears to be cytotoxic to cells with DNA alterations or damage, such as those found in tumor cells carrying mutations in the ataxia-telangiectasia gene (ATM). ATM encodes a serine/threonine protein kinase, mutations in which are associated with capillary telangiectasia and contribute to certain cancers, such as T-cell acute lymphoblastic leukemia, B-cell chronic lymphocytic leukemia, and B-cell non-Hodgkin lymphoma. Mechanism of action correction: Contrary to the previous hypothesis, iniparib (SAR240550; BSI201; NSC746045; IND71677) is not a PARP inhibitor. Its antitumor activity stems from non-selective covalent modification of cysteine residues in various proteins (e.g., PARP1, GSTP1), thereby disrupting the function of these proteins, inducing DNA damage, and making cancer cells more sensitive to chemotherapy [1]
- Clinical significance: Iniparib was evaluated in a phase III clinical trial for triple-negative breast cancer (TNBC) (e.g., in combination with gemcitabine/carboplatin), but failed to meet the primary endpoint due to its nonspecific mechanism of action (compared to true PARP inhibitors with selective targeting of HR-deficient cells). This highlights the importance of validating the target specificity of PARP inhibitors [1]

C7H5IN2O3

292.03

291.934

C, 28.79; H, 1.73; I, 43.46; N, 9.59; O, 16.44

160003-66-7

9796068

Light yellow to yellow solid powder

2.1±0.1 g/cm3

344.8±32.0 °C at 760 mmHg

162.3±25.1 °C

0.0±0.8 mmHg at 25°C

1.696

1.71

1

3

1

13

228

0

IC1C([H])=C([H])C(C(N([H])[H])=O)=C([H])C=1[N+](=O)[O-]

MDOJTZQKHMAPBK-UHFFFAOYSA-N

InChI=1S/C7H5IN2O3/c8-5-2-1-4(7(9)11)3-6(5)10(12)13/h1-3H,(H2,9,11)

4-iodo-3-nitrobenzamide

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)

Solubility in Formulation 1: ≥ 2.5 mg/mL (8.56 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 25.0 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 2: ≥ 2.5 mg/mL (8.56 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 25.0 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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 (Please use freshly prepared in vivo formulations for optimal results.)