5-HT_2A Receptor; 5-HT_2C Receptor
Sertindole is a second-generation antipsychotic drug that directly binds to and antagonizes several G-protein-coupled receptors (GPCRs). Its known directly-bound antagonistic targets include 5-HT2A, 5-HT2C, 5-HT6, and D2 receptors. This study particularly focuses on the role of the 5-HT6 receptor in mediating its anticancer effects [2].

Sertindole (0-100 μM; 48 h) reduces the growth of breast cancer cells[2].
Sertindole (0.8-27.6 μM; 48 h) inhibits the proliferation of numerous cancers in vitro[2].
Sertindole (5 μΜ and 10 μΜ; 24 h) inhibits breast cancer cell migration[2].

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Antiproliferative Activity: Sertindole exhibits broad antiproliferative activity against a panel of 29 cancer cell lines representing seven cancer types. It shows potent effects against breast cancer cell lines, with IC50 values as low as 800 nM. Triple-negative breast cancer (TNBC) cell lines (ER-PR-) are more sensitive (average IC50 = 4.1 μM for MDA-MB-453, MDA-MB-231, SUM159) than ER+PR+ cell lines (average IC50 = 9.3 μM for MCF-7, T47D, ZR-75-1). In SUM159 TNBC cells, the IC50 is 9.2 μM after 48h treatment. It also demonstrates toxicity towards non-tumorigenic MCF-10A breast epithelial cells with an IC50 of 27.6 μM [2].
Colony Formation Inhibition: In a colony formation assay with SUM159 cells, treatment with 1 μM sertindole for 15 days reduces colony counts to 77.5% of control, while 2 μM reduces counts to 4.9% [2].
Anti-Migratory and Anti-Invasive Effects: Sertindole disrupts F-actin stress fibers in SUM159 cells after 6h treatment, even at 5 μM. In a wound healing assay, 20 μM sertindole significantly delays cell migration by 52.1% over 72h. In an invasion assay, 5 μM sertindole blocks approximately 50% of cell invasion through membranes, and 10 μM almost completely abolishes invasion after 24h [2].
Mechanism of Cell Death - Autophagy-Associated Apoptosis: In SUM159 cells, sertindole (10 μM) induces autophagy, as evidenced by increased LC3-I to LC3-II conversion, decreased p62 levels (indicating autophagic flux), increased GFP-LC3 puncta dots (~5.0-fold increase), and increased lysosome density. Autophagy occurs as early as 2 hours post-treatment. Subsequently, apoptosis is triggered, shown by increased cleaved caspase-3 levels (from 3 hours onward) and a dose-dependent increase in Annexin-V positive cells (from 36 hours). Inhibition of autophagy with 3-methylade (3-MA) or bafilomycin A1 (baf) significantly reduces sertindole-induced apoptosis and increases cell viability, indicating that apoptosis is autophagy-associated [2].
Role of 5-HT6 Receptor: The 5-HT6 receptor is expressed in SUM159 cells. Overexpression of 5-HT6 in SUM159 cells blocks sertindole-induced LC3-II conversion and caspase-3 cleavage. Conversely, co-treatment with the specific 5-HT6 antagonist SB258585 (100 mM) potentiates sertindole's effects, enhancing LC3-II conversion and caspase-3 cleavage at lower sertindole concentrations (2.5, 5, 10 μM). This suggests that sertindole's anticancer effects are partly mediated through inhibition of the 5-HT6 receptor [2].
Cell Cycle Analysis: Sertindole (10 μM) treatment of SUM159 cells for up to 84 hours results in only a minor (15.1%) loss of G1 phase cells, suggesting mitotic catastrophe is not a primary mechanism of cell death [2].

Sertindole (10 mg/kg; once daily; 12 d) exhibits anti-tumor activity in vivo[2].

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Efficacy in Orthotopic Breast Tumor Model: In immune-deficient Balb/c mice orthotopically implanted with MDA-MB-231 human TNBC cells, daily oral administration of sertindole at 10 mg/kg for 12 days significantly attenuates tumor growth, resulting in a 22.7% reduction in average tumor volume compared to vehicle-treated controls [2].

Cell Line: SUM159 and MCF-10A cells
Concentration: 0-100 μM
Incubation Time: 48 hours
Result: Showed IC50s of 9.2 µM and 27.6 µM for SUM159 and MCF-10A cells, respectively.

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Cytotoxicity (MTT Assay): Cells (3,000-5,000/well) were seeded in 96-well plates. After 24h, they were treated with various concentrations of sertindole for 36 or 48h. MTT solution (0.5 mg/mL) was added, incubated for 4h, then DMSO was added. Absorbance was read at 490 nm to calculate IC50 values [2].
Colony Formation Assay: SUM159 cells (300-500/well) were seeded in 6-well plates. After 24h, they were treated with sertindole (0, 1, 2 μM) for 15 days, with medium replaced every three days. Colonies were fixed with methanol and stained with Giemsa for counting [2].
Wound Healing Assay: SUM159 cells were grown to confluence in 6-well plates. A scratch was made with a micropipette tip. Cells were washed and cultured in serum-free medium with or without 20 μM sertindole for 72h. Wound widths were measured at 0h and 72h to calculate migration [2].
Invasion Assay: SUM159 cells (10⁵-10⁶) in serum-free medium with or without sertindole (5, 10 μM) were seeded in the upper chamber of a Transwell insert. The lower chamber contained 10% FBS medium. After 24h, non-invasive cells were removed, and invasive cells on the lower membrane surface were fixed, stained, and counted [2].
Immunofluorescence: SUM159 cells on coverslips were treated with sertindole (0, 5, 10, 20 μM) for 6h. Cells were fixed, permeabilized, and stained with FITC-phalloidin (for F-actin) and DAPI (for nuclei). Images were acquired by fluorescence microscopy [2].
Western Blotting: Cells treated with sertindole were lysed, and proteins were separated by SDS-PAGE. Membranes were probed with antibodies against LC3, p62, cleaved caspase-3, and β-actin (loading control). Protein levels were quantified by densitometry [2].
Autophagy (GFP-LC3 Puncta): Cells expressing GFP-LC3 were treated with 10 μM sertindole for 2h. The number of GFP-LC3 puncta per cell was counted under a fluorescence microscope [2].
Lysosome Staining: SUM159 cells treated with 10 μM sertindole for 2h were stained with LysoTracker dye to visualize lysosomes by fluorescence microscopy [2].
Apoptosis (Flow Cytometry): SUM159 cells treated with sertindole (alone or with inhibitors) for 36h were stained with Annexin V-FITC and PI. Stained cells were analyzed by flow cytometry to quantify apoptotic cells [2].
Cell Cycle Analysis (Flow Cytometry): SUM159 cells treated with 10 μM sertindole for 48, 60, or 84h were fixed with ethanol, stained with PI/RNase, and analyzed by flow cytometry to determine cell cycle distribution [2].

Immune-deficient Balb/c mice implanted MDA-MB-231 human TNBC cells
10 mg/kg
Oral gavage; 10 mg/kg; once daily; 12 days

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Orthotopic Breast Tumor Model:** Female Balb/c immune-deficient mice (6-8 weeks old) were implanted orthotopically into the right mammary fat pad with 10⁷ MDA-MB-231 cells mixed with Matrigel. When tumors reached ~200 mm³, mice were randomized into groups (n=8 for sertindole group, n=7 for control group). Sertindole was administered daily by oral gavage at 10 mg/kg (dissolved in vehicle). The control group received vehicle alone. Tumor volumes (calculated as V = (Length × Width²)/2) and body weights were measured twice weekly for 12 days. At the end of the study, brain weights were also measured [2].

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Orthotopic Breast Tumor Model: Female Balb/c immune-deficient mice (6-8 weeks old) were implanted orthotopically into the right mammary fat pad with 10⁷ MDA-MB-231 cells mixed with Matrigel. When tumors reached ~200 mm³, mice were randomized into groups (n=8 for sertindole group, n=7 for control group). Sertindole was administered daily by oral gavage at 10 mg/kg (dissolved in vehicle). The control group received vehicle alone. Tumor volumes (calculated as V = (Length × Width²)/2) and body weights were measured twice weekly for 12 days. At the end of the study, brain weights were also measured [2].

Absorption, Distribution and Excretion
Effective orally. Metabolism/Metabolites Hepatic metabolism. Serindole is metabolized by cytochrome P450 isoenzymes CYP 2D6 and CYP 3A4. Known human metabolites of serindole include 5-chloro-1-(4-fluorophenyl)-3-(piperidin-4-yl)-1H-indole and 1-[2-[4-[5-chloro-1-(4-fluorophenyl)indole-3-yl]piperidin-1-yl]ethyl]-4-hydroxyimidazolidine-2-one. Biological Half-Life 3 days

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Sertindole is noted for its ability to penetrate the blood-brain barrier (BBB) with a brain/plasma ratio greater than 1.2, reaching a higher concentration in the brain than in plasma. This property makes it a candidate for treating breast-to-brain metastases [2].

In Vivo Tolerability: In the xenograft mouse study, daily oral administration of 10 mg/kg sertindole for 12 days did not cause any apparent reduction in body weight or brain weight compared to control mice, indicating tolerability at this efficacious dose [2].
Clinical Safety Context: The literature mentions that compared to first-generation antipsychotics (FGAs), sertindole (as a second-generation antipsychotic, SGA) is associated with lower mortality rates, less severe and fewer extrapyramidal symptoms (EPS), and does not appear to significantly increase mortality in elderly patients. The EPS-triggering dose threshold in humans may approach 800 mg, which is 33 times the maximal antipsychotic therapeutic dose [2].

[1]. Sertindole : a review of its use in schizophrenia. CNS Drugs. 2006;20(3):233-55.

[2]. Antiproliferative activities of the second-generation antipsychotic drug sertindole against breast cancers with a potential application for treatment of breast-to-brain metastases. Sci Rep. 2018 Oct 25;8(1):15753.

[3]. Sertindole in the management of schizophrenia. J Cent Nerv Syst Dis. 2011 May 17;3:75-85.

Serdolect is a phenylindole compound with the structure 1H-indole, where the nitrogen atom is replaced by a p-chlorophenyl group, the 5-position by a chlorine atom, and the 3-position by a piperidine-4-yl group, with the nitrogen atom of the piperidine-4-yl group further replaced by a 2-(2-oxoimidazolidine-1-yl)ethyl group. It is a serotonergic antagonist, an alpha-adrenergic antagonist, an H1 receptor antagonist, and a second-generation antipsychotic. It belongs to the phenylindole class, organofluorine compounds, organochlorine compounds, heteroarylpiperidine compounds, and imidazolidineones. Serdolect is a neuroleptic and one of the newer available antipsychotic drugs. Developed by the Danish pharmaceutical company H. Lundbeck, serdolect is a phenylindole derivative used to treat schizophrenia. It was first marketed in several European countries in 1996 but was withdrawn two years later due to various adverse cardiac reactions. It has now been reapproved and will soon be available in France and Australia. Drug Indications For the treatment of schizophrenia. Mechanism of Action Serindole is an antipsychotic drug with affinity for dopamine D2 receptors, serotonin 5-HT2A and 5-HT2C receptors, and α1-adrenergic receptors. Preclinical studies have shown that serindole preferentially acts on limbic system and cortical dopaminergic neurons, and clinical trials have also confirmed that serindole exerts its therapeutic effect even under low dopamine D2 receptor occupancy.

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Sertindole is a second-generation antipsychotic drug repurposed here for its anticancer potential, particularly against triple-negative breast cancer (TNBC) which frequently metastasizes to the brain. Its ability to cross the blood-brain barrier makes it especially attractive for treating breast-to-brain metastases. This study demonstrates for the first time both in vitro and in vivo antitumor effects of sertindole against TNBC. The mechanism involves the induction of autophagy-associated apoptosis, partly mediated through inhibition of the 5-HT6 receptor. The study also shows that 5-HT6 receptor expression is two-fold higher in pre-invasive human breast tumor tissue compared to normal breast tissue, further supporting the relevance of this target. Given its established clinical safety profile as an antipsychotic, and the demonstrated antitumor efficacy at a dose (10 mg/kg in mice) approaching the maximal therapeutic dose for psychosis, sertindole holds promise as a chemotherapeutic agent for metastatic TNBC [2].

C24H26CLFN4O

440.94

440.177

C, 65.37; H, 5.94; Cl, 8.04; F, 4.31; N, 12.71; O, 3.63

106516-24-9

Sertindole-d4; 1794737-42-0

60149

White to off-white solid powder

1.4±0.1 g/cm3

592.1±50.0 °C at 760 mmHg

95-100ºC

311.9±30.1 °C

0.0±1.7 mmHg at 25°C

1.671

5.26

1

3

5

31

623

0

ClC1C([H])=C([H])C2=C(C=1[H])C(=C([H])N2C1C([H])=C([H])C(=C([H])C=1[H])F)C1([H])C([H])([H])C([H])([H])N(C([H])([H])C([H])([H])N2C(N([H])C([H])([H])C2([H])[H])=O)C([H])([H])C1([H])[H]

GZKLJWGUPQBVJQ-UHFFFAOYSA-N

InChI=1S/C24H26ClFN4O/c25-18-1-6-23-21(15-18)22(16-30(23)20-4-2-19(26)3-5-20)17-7-10-28(11-8-17)13-14-29-12-9-27-24(29)31/h1-6,15-17H,7-14H2,(H,27,31)

1-[2-[4-[5-chloro-1-(4-fluorophenyl)indol-3-yl]piperidin-1-yl]ethyl]imidazolidin-2-one

Sertindolum; Serdolect; SerLect; Serdolect; Serlect; sertindole; Lu 23-174; Sertindole; Sertindol; Lu-23-174; sertindole hydrochloride

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: ~25 mg/mL (~56.7 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (5.67 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 (5.67 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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Solubility in Formulation 3: ≥ 2.5 mg/mL (5.67 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 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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