Clusterin (also known as TRPM-2, SGP-2, apoJ). Custirsen is an antisense oligonucleotide that specifically binds to clusterin mRNA, leading to RNase H-mediated degradation of the transcript and subsequent reduction in clusterin protein synthesis. Clusterin is a stress-induced, cytoprotective chaperone protein that is upregulated in many cancers following chemotherapy and contributes to treatment resistance. By suppressing clusterin expression, custirsen reduces chemoresistance and promotes apoptosis in cancer cells.

In cell-free systems, custirsen is not directly evaluated for enzyme inhibition. Instead, its activity is assessed by measuring its ability to hybridize with complementary clusterin mRNA sequences. The specificity of antisense hybridization is confirmed by melting temperature (Tm) analysis and nuclease stability assays. Custirsen forms stable duplexes with its target sequence with high specificity. The phosphorothioate backbone provides resistance to nuclease degradation compared to unmodified oligonucleotides.

In cultured cancer cells (e.g., prostate cancer LNCaP, PC-3, DU145), custirsen treatment results in dose-dependent reduction of clusterin mRNA and protein levels. Clusterin knockdown sensitizes cancer cells to chemotherapy-induced apoptosis. In vitro, custirsen enhances the cytotoxicity of docetaxel, cabazitaxel, and other chemotherapeutic agents. The extent of clusterin knockdown (>90% reduction) correlates with increased apoptotic index. Custirsen does not directly inhibit cell proliferation but modulates the cellular response to cytotoxic agents.

Antisense activity is assessed by incubating custirsen with target RNA in cell-free hybridization assays. The oligonucleotide (0.1-10 uM) is mixed with synthetic clusterin RNA or in vitro transcribed mRNA in hybridization buffer, heated to denature secondary structures, and allowed to anneal. Duplex formation is confirmed by native gel electrophoresis, RNase H cleavage assays (adding recombinant RNase H to digest the RNA strand of the hybrid), or by measuring fluorescence if using labeled probes. Melting temperature (Tm) analysis is performed by UV spectrophotometry to determine duplex stability.

Nuclease stability is evaluated by incubating custirsen in fetal bovine serum or cell lysates at 37degC for various time points (0-24 hours). Samples are analyzed by polyacrylamide gel electrophoresis or HPLC to detect intact oligonucleotide versus degradation products. The half-life in serum is calculated. For cellular activity, cancer cell lines are treated with custirsen (0.1-10 uM) for 24-72 hours using cationic lipid transfection or free uptake depending on the formulation. Clusterin mRNA is measured by qRT-PCR, and clusterin protein is measured by Western blot or ELISA. For chemosensitization studies, cells are treated with custirsen (0.1-10 uM) for 24-48 hours, then exposed to chemotherapy agents (e.g., docetaxel 1-100 nM) for an additional 48-72 hours. Apoptosis is measured by Annexin V/PI flow cytometry, caspase-3/7 activity, or sub-G1 analysis by propidium iodide staining.

In vivo efficacy of custirsen has been evaluated in prostate cancer xenograft models. Mice bearing subcutaneous human prostate tumors (LNCaP, PC-3) are treated with custirsen via intraperitoneal or intravenous administration. In combination studies, custirsen is administered prior to chemotherapy (e.g., docetaxel, cabazitaxel) to allow clusterin knockdown. In the SYNERGY Phase 3 trial, patients with mCRPC received custirsen 640 mg intravenously as three loading doses (days -9, -7, -5) followed by weekly 640 mg doses in combination with cabazitaxel 25 mg/m2 every 3 weeks. Similar regimens have been used with docetaxel. In phase 2 studies, custirsen demonstrated dose-dependent decreases in clusterin expression of >90% in prostate tissue and lymph nodes, with an associated significant increase in apoptotic index.

PK studies in humans and animals show that custirsen has a biphasic plasma elimination profile. Following intravenous administration of 640 mg over 120 minutes, peak plasma concentrations are achieved at the end of infusion. The terminal half-life is approximately 2-5 days. Custirsen distributes extensively to tissues, particularly liver, kidney, spleen, and lymph nodes, and to a lesser extent to tumors. Urinary excretion is limited (<5% of dose). The plasma clearance is low (approximately 0.3-0.6 L/h/kg). No major metabolites are observed due to the nuclease-resistant phosphorothioate backbone. The volume of distribution is approximately 200-300 mL/kg. Custirsen accumulates in tissues with repeated dosing.

In clinical trials involving 294 patients with various cancers treated with custirsen, the majority of adverse events were mild to moderate. The most common adverse events associated with custirsen include fever (pyrexia), fatigue, nausea, chills, injection site reactions, and headache. In the SYNERGY Phase 3 trial comparing cabazitaxel/custirsen to cabazitaxel/placebo, custirsen added to cabazitaxel did not increase overall toxicity compared to cabazitaxel alone. Grade 3/4 adverse events were similar between groups. No cumulative toxicity, unexpected safety signals, or dose-limiting toxicities were observed. Custirsen is not myelosuppressive, and no renal or hepatic dose-limiting toxicity has been reported.

[1]. A phase I pharmacokinetic and pharmacodynamic study of OGX-011, a 2'-methoxyethyl antisense oligonucleotide to clusterin, in patients with localized prostate cancer. J Natl Cancer Inst. 2005;97(17):1287-1296.

Custirsen is a benzopyran compound with potential antitumor activity. As a selective estrogen receptor modulator (SERM), Custirsen inhibits the proliferation of estrogen-sensitive breast cancer cells. The drug also inhibits the growth of glioblastoma cells and induces apoptosis through an estrogen receptor-independent mechanism. Custirsen is also currently under investigation for the treatment of primary brain tumors. Custirsen is a mixed-backbone antisense oligodeoxynucleotide with potential chemosensitizing activity. After administration, Custirsen blocks the translation of testosterone-suppressed prostaglandin 2 (TRPM-2). This eliminates the anti-apoptotic effect of TRPM-2, making cells more sensitive to chemotherapy and ultimately leading to tumor cell death. TRPM-2 is an anti-apoptotic cluster protein overexpressed in prostate cancer cells and associated with chemosensitivity. [hr] [strong] [Drug Indications] [strong] [br] [Investigated for the treatment of brain cancer and breast cancer.] Mechanism of Action CC-8490 is a selective estrogen receptor modulator (SERM) that inhibits the proliferation of estrogen-sensitive breast cancer cells. This drug also inhibits the growth of glioblastoma cells and induces apoptosis through an estrogen receptor-independent mechanism. Preliminary results regarding its mechanism of action in brain cancer indicate that C-8490 exerts its effects by inhibiting nuclear factor (NF)-κB and its target genes IEX-3, SOD2, IL6, and IL8. Pharmacodynamics CC-8490 is a proprietary benzopyran compound from Celgene, a novel anticancer compound currently being evaluated for its efficacy as a potential therapy for brain cancer. The National Cancer Institute has also reported its potential antitumor activity in breast cancer treatment. CC-8490 is a selective estrogen receptor modulator (SERM) that inhibits the proliferation of estrogen-sensitive breast cancer cells. Furthermore, this drug also inhibits the growth of glioblastoma cells and induces apoptosis through an estrogen receptor-independent mechanism.

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Custirsen was investigated in multiple clinical trials for various cancers, including prostate cancer, non-small cell lung cancer (NSCLC), breast cancer, and ovarian cancer. In 2014, the AFFINITY trial (NCT01578655) and SYNERGY trial (NCT01188187) evaluated custirsen in combination with cabazitaxel or docetaxel in mCRPC. These Phase 3 studies did not meet their primary endpoints for overall survival benefit, leading to discontinuation of development. In the AFFINITY trial, 635 patients with mCRPC who had previously been treated with docetaxel were randomized to custirsen plus cabazitaxel vs cabazitaxel alone; no overall survival benefit was observed. Despite the lack of clinical efficacy, custirsen remains a useful research tool for studying clusterin biology and antisense oligonucleotide therapy. As of 2024, custirsen is not approved for clinical use. It is also known as custirsen sodium in the salt form.

C231H312N78O119P20S20

7346.17541599274

7342.999

890056-27-6

76964582

Off-white to light yellow solid powder

-10

47

171

154

468

20600

71

S=P(O)(OC[C@@H]1[C@H]([C@H]([C@H](N2C=NC3C(NC(N)=NC2=3)=O)O1)OCCOC)OP(O)(OC[C@@H]1[C@H]([C@H]([C@H](N2C(N=C(C(C)=C2)N)=O)O1)OCCOC)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C=NC3C(N)=NC=NC2=3)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C=NC3C(NC(N)=NC2=3)=O)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C(N=C(C=C2)N)=O)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C=NC3C(N)=NC=NC2=3)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C=NC3C(NC(N)=NC2=3)=O)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C=NC3C(N)=NC=NC2=3)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C=NC3C(NC(N)=NC2=3)=O)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C(NC(C(C)=C2)=O)=O)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C(N=C(C=C2)N)=O)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C(NC(C(C)=C2)=O)=O)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C(NC(C(C)=C2)=O)=O)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C(N=C(C=C2)N)=O)O1)OP(O)(OC[C@@H]1[C@H](C[C@H](N2C=NC3C(N)=NC=NC2=3)O1)OP(O)(OC[C@@H]1[C@H]([C@H]([C@H](N2C(NC(C(C)=C2)=O)=O)O1)OCCOC)OP(O)(OC[C@@H]1[C@H]([C@H]([C@H](N2C(N=C(C(C)=C2)N)=O)O1)OCCOC)OP(=O)(OC[C@@H]1[C@H]([C@H]([C@H](N2C=NC3C(N)=NC=NC2=3)O1)OCCOC)OP(O)(OC[C@@H]1[C@H]([C@H]([C@H](N2C(NC(C(C)=C2)=O)=O)O1)OCCOC)O)=S)S)=S)=S)=S)=S)=S)=S)=S)=S)=S)=S)=S)=S)=S)=S)=S)=S)O[C@@H]1[C@@H](COP(O)(O[C@@H]2[C@@H](CO)O[C@H]([C@@H]2OCCOC)N2C(N=C(C(C)=C2)N)=O)=S)O[C@H]([C@@H]1OCCOC)N1C=NC2C(N)=NC=NC1=2

RCFZILUHCNXXFY-DEDWCYLFSA-N

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1-[(2R,4S,5R)-5-[[[(2R,3S,5R)-2-[[[(2R,3S,5R)-2-[[[(2R,3S,5R)-2-[[[(2R,3S,5R)-2-[[[(2R,3S,5R)-2-[[[(2R,3S,5R)-2-[[[(2R,3S,5R)-2-[[[(2R,3S,5R)-2-[[[(2R,3S,5R)-2-[[[(2R,3R,4R,5R)-5-(4-amino-5-methyl-2-oxopyrimidin-1-yl)-2-[[[(2R,3R,4R,5R)-2-[[[(2R,3R,4R,5R)-2-[[[(2R,3R,4R,5R)-5-(4-amino-5-methyl-2-oxopyrimidin-1-yl)-2-(hydroxymethyl)-4-(2-methoxyethoxy)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-5-(6-aminopurin-9-yl)-4-(2-methoxyethoxy)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-5-(2-amino-6-oxo-1H-purin-9-yl)-4-(2-methoxyethoxy)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-4-(2-methoxyethoxy)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-5-(6-aminopurin-9-yl)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-5-(2-amino-6-oxo-1H-purin-9-yl)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-5-(4-amino-2-oxopyrimidin-1-yl)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-5-(6-aminopurin-9-yl)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-5-(2-amino-6-oxo-1H-purin-9-yl)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-5-(6-aminopurin-9-yl)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-5-(2-amino-6-oxo-1H-purin-9-yl)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-5-(5-methyl-2,4-dioxopyrimidin-1-yl)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-5-(4-amino-2-oxopyrimidin-1-yl)oxolan-3-yl]oxy-hydroxyphosphinothioyl]oxymethyl]-4-[[(2R,3S,5R)-3-[[(2R,3S,5R)-3-[[(2R,3S,5R)-3-[[(2R,3R,4R,5R)-3-[[(2R,3R,4R,5R)-5-(4-amino-5-methyl-2-oxopyrimidin-1-yl)-3-[[(2R,3R,4R,5R)-5-(6-aminopurin-9-yl)-3-[hydroxy-[[(2R,3R,4R,5R)-3-hydroxy-4-(2-methoxyethoxy)-5-(5-methyl-2,4-dioxopyrimidin-1-yl)oxolan-2-yl]methoxy]phosphinothioyl]oxy-4-(2-methoxyethoxy)oxolan-2-yl]methoxy-hydroxyphosphinothioyl]oxy-4-(2-methoxyethoxy)oxolan-2-yl]methoxy-hydroxyphosphinothioyl]oxy-4-(2-methoxyethoxy)-5-(5-methyl-2,4-dioxopyrimidin-1-yl)oxolan-2-yl]methoxy-hydroxyphosphinothioyl]oxy-5-(6-aminopurin-9-yl)oxolan-2-yl]methoxy-hydroxyphosphinothioyl]oxy-5-(4-amino-2-oxopyrimidin-1-yl)oxolan-2-yl]methoxy-hydroxyphosphinothioyl]oxy-5-(5-methyl-2,4-dioxopyrimidin-1-yl)oxolan-2-yl]methoxy-hydroxyphosphinothioyl]oxyoxolan-2-yl]-5-methylpyrimidine-2,4-dione

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)

H2O : ~50 mg/mL (~6.81 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.)