TOP I; topoisomerase I

Exatecan has an IC50 of 0.975 μg/mL, making it a strong inhibitor of topoisomerase I. The proliferation of several cancer cell lines, including those from the breast, colon, stomach, and lung regions, is markedly inhibited by exatecan mesylate (DX-8951f) [1]. The cytotoxic action of exatecan mesylate (DX-8951f) against PC-6 and PC-6/SN2-5 cells is demonstrated by average GI50 values of 0.186 and 0.395 ng/mL, respectively. In PC-6 and PC-6/SN2-5 cells, exatecan mesylate (34 nM) stabilizes DNA-TopoI complexes [3].

In a mouse model with tumor cells but no toxic mortality, exatecan mesylate (DX-8951f, 3.325-50 mg/kg, intravenous injection) showed anti-tumor efficacy [1]. In the MIA-PaCa-2 early model and the BxPC-3 early model, exatecan Mesylate (15, 25 mg/kg, iv) significantly suppresses the growth of MIA-PaCa and BxPC-3 primary tumors. In the BxPC-3 advanced cancer model, exatecan mesylate (15, 25 mg/kg, intravenous injection) totally eradicates lung metastasis and dramatically reduces BxPC-3 lymphatic metastasis [2].

Cell Lysis and Western Blotting: [3]
Cells (5 × 10⁶) were lysed using SDS buffer (10 mM HEPES, 2 mM orthovanadate, 10 mM NaF, 10 mM pyrophosphate, 1 mM PMSF, 10 µg/mL leupeptin, 10% 2-mercaptoethanol, 10% glycerol, 8% SDS, 42 mM Tris-HCl, 0.002% bromophenol blue, pH 7.4). Proteins from the whole-cell lysates were separated by 7.5% polyacrylamide gel electrophoresis and transferred onto a nitrocellulose membrane. The membrane was probed with an anti-Topo I human antibody, followed by incubation with horseradish peroxidase-conjugated protein A. Topo I-specific bands were visualized using ECL reagents.

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Nuclear Extract Preparation: [3]
For nuclear extracts, cells (5 × 10⁷) were washed with ice-cold buffer (2 mM K₂HPO₄, 5 mM MgCl₂, 150 mM NaCl, 1 mM EGTA, 0.1 mM dithiothreitol), resuspended in buffer containing 0.35% Triton-X100 and PMSF, and incubated on ice for 10 min. The lysates were centrifuged, and the resulting pellet was further incubated with buffer containing 0.35 M NaCl for 1 hour at 4°C. After centrifugation (18,000 × g, 10 min), the protein concentration of the supernatant (nuclear extract) was determined using Bradford’s method with a protein assay kit. Equal amounts of nuclear protein were then subjected to Western blot analysis with anti-Topo I antibody.

Growth Inhibition Assay (MTT Method): [1]
Cell growth inhibition was assessed in 96-well flat-bottom microplates using the MTT assay. Cells (500–20,000/well) were seeded in 150 μL of medium and pre-incubated for 24 hours (4 hours for P388, CCRF-CEM, and K562 cells). Test compounds, including Exatecan Mesylate (in 150 μL medium/well), or medium alone (control) were then added, followed by a 3-day incubation. After treatment, 20 μL of MTT solution (5 mg/mL in PBS) was added to each well, and plates were incubated for 4 hours. The plates were centrifuged at 800 × g for 5 minutes, the supernatant was removed, and the formazan crystals were dissolved in 150 μL of DMSO. Absorbance was measured at 540 nm using a Microplate Reader (Model 3550).

Experimental Design and Treatment Protocol [2]
Early-Stage Model (3 Weeks Post-Implantation)
Animal Groups: Mice bearing orthotopically implanted BxPC-3-GFP or MIA-PaCa-2-GFP tumors were randomized into five groups (n = 5/group) at 3 weeks post-implantation.
Group 1: Untreated control.
Groups 2 & 3: Treated with Exatecan Mesylate (25 and 15 mg/kg/dose, respectively).
Groups 4 & 5: Treated with gemcitabine (300 and 150 mg/kg/dose, respectively).
Late-Stage Model (6 Weeks Post-Implantation)
Animal Groups: Mice with BxPC-3-GFP tumors were randomized into three groups (n = 20/group) at 6 weeks post-implantation.
Group 1: Untreated control.
Group 2: Treated with Exatecan Mesylate (25 mg/kg/dose).
Group 3: Treated with gemcitabine (300 mg/kg/dose).
Dosing Schedule
Drugs were administered once weekly for 3 weeks, followed by a 2-week break, and then resumed for another 3 weeks.
Monitoring and Analysis
Weekly measurements: Primary tumor size (calculated as a × b² × 0.5, where a = larger diameter, b = smaller diameter) and body weight.
Termination: Mice were sacrificed at study completion, with final tumor weights and GFP imaging (primary tumors and metastases) recorded.

[1]. A new water-soluble camptothecin derivative, DX-8951f, exhibits potent antitumor activity against human tumors in vitro and in vivo. Jpn J Cancer Res. 1995 Aug;86(8):776-82.

[2]. Efficacy of camptothecin analog DX-8951f (Exatecan Mesylate) on human pancreatic cancer in an orthotopic metastatic model. Cancer Res. 2003 Jan 1;63(1):80-5.

[3]. DX-8951f, a water-soluble camptothecin analog, exhibits potent antitumor activity against a human lung cancer cell line and its SN-38-resistant variant. Int J Cancer. 1997 Aug 7;72(4):680-6.

Exatecan is a pyranoindolizinoquinoline.
Exatecan has been used in trials studying the treatment of Sarcoma, Leukemia, Lymphoma, Lung Cancer, and Liver Cancer, among others.

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CPT-11, a semisynthetic derivative of camptothecin, exhibited strong antitumor activity against lymphoma, lung cancer, colorectal cancer, gastric cancer, ovarian cancer, and cervical cancer. CPT-11 is a pro-drug that is converted to an active metabolite, SN-38, in vivo by enzymes such as carboxylesterase. We synthesized a water-soluble and non-pro-drug analog of camptothecin, DX-8951f. It showed both high in vitro potency against a series of 32 malignant cell lines and significant topoisomerase I inhibition. The anti-proliferative activity of DX-8951f, as indicated by the mean GI50 value, was about 6 and 28 times greater than that of SN-38 or SK&F 10486-A (Topotecan), respectively. These three derivatives of camptothecin showed similar patterns of differential response among 32 cell lines, that is, their spectra of in vitro cytotoxicity were almost the same. The antitumor activity of three doses of DX-8951f administered i.v. at 4-day intervals against human gastric adenocarcinoma SC-6 xenografts was greater than that of CPT-11 or SK&F 10486-A. Moreover, it overcame P-glycoprotein-mediated multi-drug resistance. These data suggest that DX-8951f has a high antitumor activity and is a potential therapeutic agent.[1]

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We determined the antitumor and antimetastatic efficacy of the camptothecin analogue DX-8951f in an orthotopic metastatic mouse model of pancreatic cancer. DX-8951f showed efficacy against two human pancreatic tumor cell lines in this model. These cell lines were transduced with the green fluorescent protein, enabling high-resolution visualization of tumor and metastatic growth in vivo. The DX-8951f studies included both an early and advanced cancer model. In the early model, using the human pancreatic cancer lines MIA-PaCa-2 and BxPC-3, treatment began when the orthotopic primary tumor was approximately 7 mm in diameter. DX-8951f was significantly effective against both MIA-PaCa-2 and BxPC-3. In contrast, 2', 2'-difluorodeoxycytidine (gemcitabine), the standard treatment for pancreatic cancer, did not have significant efficacy against MIA-PaCa-2. Although gemcitabine showed significant activity against BxPC-3 primary tumor growth, it was not effective on metastasis. In the model of advanced disease, using BxPC-3, treatment started when the orthotopic primary tumor was 13 mm in diameter. DX-8951f was significantly effective in a dose-response manner on the BxPC-3 primary tumor. DX-8951f also demonstrated antimetastatic activity in the late-stage model, significantly reducing the incidence of lymph node metastasis while eliminating lung metastasis. In contrast, gemcitabine was only moderately effective against the primary tumor and ineffective against metastasis at both sites in the late-stage model. Therefore, DX-8951f was highly effective against primary and metastatic growth in this very difficult-to-treat disease and showed significantly higher efficacy than gemcitabine, the standard treatment of pancreatic cancer. DX-8951f, therefore, has important clinical promise and has more positive features than the currently used camptothecin analogue CPT-11, which requires metabolic activation and is toxic.[2]

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We previously reported that DX-8951f, a novel water-soluble camptothecin analog, significantly inhibits the growth of various human and murine tumors in vitro and in vivo. The antitumor effects and topoisomerase I inhibitory activity of DX-8951f are stronger than those of other current camptothecin analogs. In this study, we established an SN-38-resistant cell line, PC-6/SN2-5, from the human oat cell carcinoma PC-6 cell line by a stepwise selection system, investigated the mechanism of resistance of this cell line and then compared the antitumor activity of camptothecin analogs against the cell line. PC-6/SN2-5 cells were resistant to SN-38 (32-fold) and SK&F 104864 (topotecan; 14-fold), but barely resistant to CPT-11 (3-fold) and DX-8951f (2-fold). Topoisomerase I protein levels and topoisomerase I activities of parental cells were similar to those of resistant cells. Determination of the cellular drug concentration by either flow cytometric analysis or the high-performance liquid chromatography method confirmed that the cellular accumulation of SN-38 and topotecan was significantly reduced in PC-6/SN2-5 cells, whereas that of DX-8951f was only slightly reduced. Furthermore, DX-8951f stabilized the cleavable complex formations in intact PC-6/SN2-5 cells as well as in parental cells, but SN-38 and topotecan did not in the resistant cells. Our data suggest that PC-6/SN2-5 cells may have acquired resistance to camptothecin analogs by a decrease in intracellular drug accumulation and that DX-8951f may have the potency to overcome such a type of resistance mechanism induced by camptothecin compounds.[3]

C24H22FN3O4

531.55324

435.159

C, 66.20; H, 5.09; F, 4.36; N, 9.65; O, 14.70

171335-80-1

Exatecan mesylate;169869-90-3;Dxd;1599440-33-1;Exatecan mesylate dihydrate;197720-53-9

151115

Gray to brown solid powder

1.5±0.1 g/cm3

818.4±65.0 °C at 760 mmHg

448.7±34.3 °C

0.0±3.1 mmHg at 25°C

1.735

1.81

2

7

1

32

950

2

CC[C@@]1(C2=C(COC1=O)C(=O)N3CC4=C5[C@H](CCC6=C5C(=CC(=C6C)F)N=C4C3=C2)N)O

ZVYVPGLRVWUPMP-FYSMJZIKSA-N

InChI=1S/C24H22FN3O4/c1-3-24(31)14-6-18-21-12(8-28(18)22(29)13(14)9-32-23(24)30)19-16(26)5-4-11-10(2)15(25)7-17(27-21)20(11)19/h6-7,16,31H,3-5,8-9,26H2,1-2H3/t16-,24-/m0/s1

(1S,9S)-1-Amino-9-ethyl-5-fluoro-1,2,3,9,12,15-hexahydro-9-hydroxy-4-methyl-10H,13H-benzo(de)pyrano(3',4'

DX 8951; DX 8951; Exatecan; 171335-80-1; Exatecan [INN]; Dx 8951; UNII-OC71PP0F89; DX-8951f; OC71PP0F89; DX 8951.

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

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

DMSO : ~50 mg/mL (~114.82 mM)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*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.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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