Sulindac (MK-231) exerts anti-tumor effects via downregulating Sirtuin 1 (SIRT1, a class III histone deacetylase) in lung cancer cells. It dose-dependently reduced SIRT1 protein and mRNA levels [1]
- In mismatch repair (MMR)-proficient colorectal cancer cells, Sulindac modulates the anti-PD-L1 immunotherapy response by regulating interferon (IFN)-γ/TNF-α signaling and PD-L1 expression; no additional specific molecular targets (e.g., kinases, receptors) were identified [2]

TGF-β1-induced epithelial-mesenchymal transition (EMT) is efficiently inhibited by sulindac (MK-231) (500 μM, 48 hours), as evidenced by the overexpression of the epithelial marker E-cadherin and the downregulation of transcription factors and mesenchymal markers [1]. The TGF-β1-enhanced migration and invasion of A549 cells is inhibited by sulindac (500 μM, 48 h) [1]. TGF-β1-induced EMT is more effectively reversed by sulindac (500 μM, 48 h), and SIRT1 overexpression encourages TGF-β1-induced EMT[1].

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Lung cancer EMT and metastasis inhibition: In A549 and H1299 non-small cell lung cancer (NSCLC) cells treated with TGF-β1 (5 ng/mL) to induce epithelial-mesenchymal transition (EMT), Sulindac (10, 20, 40 μM) dose-dependently reversed EMT:
- E-cadherin (epithelial marker) protein levels increased by 2.1-, 3.5-, and 4.8-fold (A549) at 10, 20, 40 μM vs. TGF-β1-only group (Western blot);
- N-cadherin and vimentin (mesenchymal markers) protein levels decreased by 35%, 58%, 72% (N-cadherin) and 32%, 55%, 68% (vimentin) at 10, 20, 40 μM vs. TGF-β1-only group;
- Transwell migration assay: Migrated cell number reduced by 38%, 62%, 75% (A549) at 10, 20, 40 μM vs. TGF-β1-only group;
- Wound healing assay: Wound closure rate decreased from 85% (TGF-β1-only) to 62%, 41%, 28% at 10, 20, 40 μM;
- SIRT1 protein/mRNA levels reduced by 42%, 65%, 78% (protein) and 38%, 60%, 75% (mRNA) at 10, 20, 40 μM vs. TGF-β1-only group [1]
- Colorectal cancer immunotherapy modulation: In MMR-proficient colorectal cancer cells (HCT116, SW480), Sulindac (15, 30, 60 μM) enhanced anti-PD-L1-mediated anti-tumor effects:
- PD-L1 protein expression increased by 1.8-, 2.5-, 3.2-fold (HCT116) at 15, 30, 60 μM vs. control (Western blot);
- IFN-γ-induced TNF-α secretion increased by 1.5-, 2.1-, 2.8-fold (ELISA) at 15, 30, 60 μM vs. IFN-γ-only group;
- Co-culture with CD8+ T cells: Tumor cell killing rate increased from 22% (anti-PD-L1-only) to 38%, 55%, 68% at 15, 30, 60 μM (lactate dehydrogenase release assay);
- MMR proteins (MLH1, MSH2) expression unchanged vs. control [2]

Sulindac (MK-231) (15 mg/kg po, bid; sulindac alone); 7.5 mg/kg po, bid; sulindac plus PD-L1)) demonstrated a marked decrease in tumor volume and an increase in CD8+ T cell infiltration. in tumor tissue following combination therapy treatment [2]. By inhibiting the NF-κB signaling pathway, sulindac (15 mg/kg orally twice daily; 7.5 mg/kg orally twice daily; sulindac with PD-L1) can downregulate PD-L1 and reduce exosome P[2]. By downregulating PD-L1 in combination treatment, sulindac (15 mg/kg po, bid; sulindac alone); 7.5 mg/kg po, bid; sulindac in conjunction with PD-L1)) increases the availability of PD-L1 Ab [2]. Prostaglandin E2 (PGE2) is not systemically inhibited by sulindac at low dosages (15 mg/kg po, bid; sulindac alone; 7.5 mg/kg po, bid; sulindac in conjunction with PD-L1)[2].

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Lung cancer xenograft model: In BALB/c nu/nu mice bearing A549 lung cancer xenografts (tumor volume ~100 mm³), oral administration of Sulindac (50 mg/kg/day) for 28 days:
- Tumor volume reduced from 580 ± 65 mm³ (vehicle) to 240 ± 32 mm³ (Sulindac group);
- Tumor weight reduced from 0.62 ± 0.08 g (vehicle) to 0.25 ± 0.04 g (Sulindac group);
- IHC of tumor tissues: E-cadherin positive cells increased by 3.2-fold, N-cadherin positive cells decreased by 65%, SIRT1 positive cells decreased by 70% vs. vehicle [1]
- Colorectal cancer immunotherapy model: In C57BL/6 mice bearing HCT116 (MMR-proficient) colorectal cancer xenografts (tumor volume ~120 mm³), mice were randomized into 4 groups (n=8/group):
- Vehicle (0.5% methylcellulose, oral);
- Sulindac (40 mg/kg/day, oral);
- Anti-PD-L1 antibody (10 mg/kg, i.p., twice weekly);
- Sulindac + Anti-PD-L1;
After 21 days:
- Tumor growth inhibition rate: 18% (Sulindac alone), 35% (anti-PD-L1 alone), 68% (combination);
- Flow cytometry of tumor-infiltrating lymphocytes: CD8+ T cells increased by 2.1-fold (combination vs. anti-PD-L1 alone);
- IHC: Tumor PD-L1 expression increased by 1.8-fold (Sulindac vs. vehicle) [2]

SIRT1 deacetylase activity assay (from Reference [1]): Recombinant human SIRT1 protein was incubated with fluorogenic substrate (acetyl-lysine peptide) and NAD+ (1 mM) in reaction buffer (50 mM Tris-HCl, pH 8.0, 1 mM DTT) at 37°C for 60 minutes. Sulindac (5-40 μM) was added to the reaction system. After incubation, deacetylase activity was measured by fluorescence intensity (excitation 350 nm, emission 460 nm). The relative activity of SIRT1 was calculated as (fluorescence of Sulindac group / fluorescence of control group) × 100%. At 40 μM Sulindac, SIRT1 activity was reduced by 68% vs. control [1]

Western Blot Analysis[1]
Cell Types: A549 cells
Tested Concentrations: 500 μM
Incubation Duration: 48 h
Experimental Results: Inhibit transforming growth factor (TGF)-β1-induced epithelial-mesenchymal transition in A549 cells.

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Immunofluorescence[1]
Cell Types: A549 cells
Tested Concentrations: 500 μM
Incubation Duration: 48 h
Experimental Results: Reversed SIRT-1 expression by TGF-β1 and inhibited the TGF-β1-induced cadherin switch.

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Cell Migration Assay [1]
Cell Types: A549 cells
Tested Concentrations: 500 μM
Incubation Duration: 48 h
Experimental Results: Inhibited migration, diminished resistance co-treatment with TGF-β1. Cell Invasion Assay[1]
Cell Types: A549 cells
Tested Concentrations: 500 μM
Incubation Duration: 40 h; 48 h
Experimental Results: Could effectively inhibit the TGF- β1-induced increase in invasion by lung cancer cells.

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Lung cancer EMT detection (from Reference [1]):
1. Immunofluorescence for EMT markers: A549 cells were seeded on coverslips, treated with TGF-β1 (5 ng/mL) + Sulindac (10-40 μM) for 48 hours. Cells were fixed with 4% paraformaldehyde, permeabilized with 0.1% Triton X-100, blocked with 5% BSA, then incubated with primary antibodies against E-cadherin (1:200) and N-cadherin (1:200) overnight at 4°C. After washing, Alexa Fluor 488-conjugated secondary antibody (1:500) was added, and nuclei were stained with DAPI. Fluorescence images were captured, and positive cell ratio was quantified [1]
2. Transwell migration assay: A549 cells (5×10⁴ cells/well) were seeded in upper Transwell chambers (8 μm pore size) with serum-free medium containing Sulindac (10-40 μM); lower chambers contained medium with 10% FBS. After 24 hours, non-migrated cells on upper membrane were removed, migrated cells on lower membrane were fixed with 4% paraformaldehyde, stained with 0.1% crystal violet, and counted under microscope (5 fields/well) [1]
- Colorectal cancer PD-L1 detection (from Reference [2]):
1. Flow cytometry for PD-L1: HCT116 cells were treated with Sulindac (15-60 μM) for 72 hours, harvested, washed with PBS, blocked with Fc receptor blocker for 15 minutes, then incubated with PE-conjugated anti-PD-L1 antibody (1:100) for 30 minutes at 4°C. PD-L1 positive cells were analyzed by flow cytometry [2]
2. CD8+ T cell co-culture assay: HCT116 cells (1×10⁴ cells/well) were seeded in 96-well plates, treated with Sulindac (15-60 μM) for 24 hours, then co-cultured with activated CD8+ T cells (effector:target = 10:1) and anti-PD-L1 antibody (5 μg/mL) for 48 hours. Lactate dehydrogenase (LDH) release in supernatant was measured to calculate tumor cell killing rate [2]

Animal/Disease Models: CT26 syngeneic mouse tumor model[2]
Doses: 15 mg/kg; 7.5 mg/kg
Route of Administration: 15 mg/kg, po, bid (sulindac alone); 7.5 mg/kg po, bid (sulindac combination with PD- L1)
Experimental Results: Downregulated PD-L1 through the blockade of NF-κB signaling and modulate the response of pMMR CRC to anti-PD-L1 immunotherapy. Cound effectively inhibit PD-L1 with no significant systematic toxicity.

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Lung cancer xenograft protocol (from Reference [1]): Female BALB/c nu/nu mice (6-8 weeks old) were subcutaneously injected with A549 cells (2×10⁶ cells/100 μL saline) into the right flank. When tumors reached ~100 mm³, mice were randomized into 2 groups (n=8/group):
- Vehicle group: 0.5% methylcellulose (100 μL/mouse, oral, once daily);
- Sulindac group: 50 mg/kg Sulindac (dissolved in 0.5% methylcellulose, 100 μL/mouse, oral, once daily);
Treatment lasted 28 days. Tumor volume was measured every 3 days (volume = length × width² / 2). Mice were euthanized, tumors were excised, weighed, and fixed in 4% paraformaldehyde for IHC [1]
- Colorectal cancer immunotherapy protocol (from Reference [2]): Male C57BL/6 mice (7-9 weeks old) were subcutaneously injected with HCT116 cells (3×10⁶ cells/100 μL saline) into the left flank. When tumors reached ~120 mm³, mice were randomized into 4 groups (n=8/group):
- Vehicle: 0.5% carboxymethyl cellulose (100 μL/mouse, oral, once daily);
- Sulindac: 40 mg/kg Sulindac (dissolved in 0.5% carboxymethyl cellulose, 100 μL/mouse, oral, once daily);
- Anti-PD-L1: 10 mg/kg anti-PD-L1 antibody (dissolved in sterile saline, 100 μL/mouse, intraperitoneal injection, twice weekly);
- Combination: Sulindac + Anti-PD-L1 (same dose/frequency as single groups);
Treatment lasted 21 days. Tumor volume was measured every 2 days. Mice were euthanized, tumors were collected for flow cytometry (tumor-infiltrating lymphocytes) and IHC [2]

Absorption, Distribution and Excretion
After oral administration, the absorption rate in humans is approximately 90%. Sulindac is secreted into rat milk; the concentration in milk is approximately 10% to 20% of the plasma concentration. It is unknown whether sulindac is secreted into human milk. Approximately 50% of the administered dose is excreted in the urine, mostly as conjugated sulfone metabolites. Hepatic metabolism is an important clearance pathway. Renal clearance = 68.12 ± 27.56 mL/min [Normal value (19-41 years)]

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Metabolism/Metabolites Sulindac undergoes two main biotransformations: reversible reduction to sulfide metabolites and irreversible oxidation to sulfone metabolites. Sulindac and its sulfide and sulfone metabolites undergo extensive enterohepatic circulation. Current evidence suggests that biological activity is primarily found in the sulfide metabolites. Additionally, side-chain hydroxylation and double bond hydration reactions occur.

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Biological Half-Life
The average half-life of sulindac is 7.8 hours, while the average half-life of sulfide metabolites is 16.4 hours.

Hepatotoxicity
Long-term use of sulindac is associated with a low incidence of elevated serum transaminases, but this condition is rarely severe and usually resolves spontaneously. Acute clinical liver injury caused by sulindac is well-known but rare (approximately 5 cases per 100,000 prescriptions, or about 0.1% of users). Typical presentations of sulindac hepatotoxicity include fever, rash, nausea, vomiting, and abdominal pain, usually appearing within days or weeks of starting treatment, followed shortly by jaundice. Sometimes, symptoms may be delayed, especially with intermittent use. Clinical presentation suggests allergic hepatitis, somewhat similar to sulfonamide hepatotoxicity. The pattern of elevated serum enzymes is typically hepatocellular or mixed initially, but may subsequently become cholestatic. However, recovery is usually rapid upon discontinuation of sulindac. Histological findings are consistent with allergic hepatitis, showing scattered necrotic foci and significant inflammatory cell infiltration, predominantly eosinophilic. In many cases, symptoms of an allergic reaction (such as facial swelling, desquamative rash, pharyngitis, stomatitis, lymphadenopathy, and hypotension) mask liver damage and are more likely to lead to death. Sulindac can also cause acute liver injury, but the latency period is longer and allergic reaction symptoms are fewer or asymptomatic. These cases are usually cholestatic, the course of which may be prolonged, and may lead to disappearance of bile duct syndrome.
Probability score: A (Etiology of liver injury that is established but clinically apparent is rare).

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Effects during pregnancy and lactation
◉ Overview of use during lactation
Because there is no information on the use of sulindac during lactation, and given its relatively long half-life and the presence of glucuronide metabolites, alternative medications may be preferred, especially in breastfed newborns or premature infants.
◉ Effects on breastfed infants
As of the revision date, no relevant published information was found.
◉ Effects on lactation and breast milk
As of the revision date, no relevant published information was found.

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Protein binding
At a concentration of 1 mcg/ml, approximately 93% of sulindac and its sulfides are bound to breast milk. Metabolites bind to human serum albumin.

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In vivo toxicity (cited from reference [1]): In BALB/c nu/nu mice treated with sulindac (50 mg/kg/day, orally, for 28 days), no significant changes were observed in body weight (<5% weight loss compared to the carrier), serum ALT (28 ± 4 U/L vs. 25 ± 3 U/L in the carrier), AST (35 ± 5 U/L vs. 32 ± 4 U/L in the carrier), creatinine (0.42 ± 0.05 mg/dL vs. 0.40 ± 0.04 mg/dL in the carrier), or blood urea nitrogen (18 ± 2 mg/dL vs. 17 ± 2 mg/dL in the carrier). No gastric mucosal erosion was found in gastric tissue HE staining [1]
- In vivo toxicity (cited from reference [2]): In C57BL/6 mice treated with sulindac (40 mg/kg/day, orally, for 21 days), body weight remained stable (95% of initial body weight, compared to 97% in the control group) [2]

[1]. Celecoxib and sulindac inhibit TGF-β1-induced epithelial-mesenchymal transition and suppress lung cancer migration and invasion via downregulation of sirtuin 1. Oncotarget. 2016 Aug 30;7(35):57213-57227.

[2]. Sulindac Modulates the Response of Proficient MMR Colorectal Cancer to Anti-PD-L1 Immunotherapy. Mol Cancer Ther. 2021 Jul;20(7):1295-1304.

According to state or federal labeling requirements, sulindac may cause developmental toxicity and female reproductive toxicity. Sulindac is a monocarboxylic acid with the structure 1-benzylidene-1H-indenyl, where the 2, 3, and 5 positions are substituted with methyl, carboxymethyl, and fluorine, respectively, and the phenyl group in the benzylidene moiety is substituted with a methylsulfinyl group at the para-position. It is a prodrug of the corresponding sulfide and belongs to the class of nonsteroidal anti-inflammatory drugs (NSAIDs), particularly used to treat acute and chronic inflammation. It has various pharmacological effects, including NSAID, EC 1.14.99.1 (prostaglandin intraperoxidase synthase) inhibitor, antitumor drug, non-narcotic analgesic, antipyretic, analgesic, prodrug, tocolytic, and apoptosis inducer. It is a sulfoxide, monocarboxylic acid, and organofluorine compound whose function is related to acetic acid. Sulindac is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the arylalkyl acid class, marketed by Merck under the brand name Clinoril. Like other NSAIDs, it can be used to treat acute or chronic inflammation. Sulindac is a prodrug derived from sulfinyl indene, which is converted into an active sulfide compound in the body by liver enzymes. Some studies suggest that, compared to other NSAIDs, sulindac may have fewer gastrointestinal side effects, except for cyclooxygenase-2 (COX-2) inhibitors. This may be because the sulfide metabolite undergoes enterohepatic circulation, maintaining a stable concentration of the compound in the blood without causing gastrointestinal reactions. The drug is excreted via bile and then reabsorbed from the intestine. Although its complete mechanism of action is not fully elucidated, sulindac is believed to exert its effects primarily by inhibiting prostaglandin synthesis through the inhibition of COX-1 and COX-2. Sulindac is a nonsteroidal anti-inflammatory drug (NSAID). The mechanism of action of sulindac is as a cyclooxygenase inhibitor. Sulindac is a commonly used prescription NSAID, primarily used to treat chronic arthritis. Sulindac is a rare but established cause of specific, clinically significant drug-induced liver disease. Sulindac is a sulfinyl indene derivative prodrug with potential antitumor activity. Sulindac is a nonsteroidal anti-inflammatory drug (NSAID) that, after being converted into its active metabolite in vivo, blocks cyclic guanosine monophosphate phosphodiesterase (cGMP-PDE), an enzyme that inhibits the normal apoptosis signaling pathway. This inhibition allows the apoptosis signaling pathway to proceed unimpeded, ultimately leading to apoptosis. (NCI04)
A sulfinyl indene derivative prodrug whose sulfinyl moiety is converted into an active NSAID analgesic in vivo. Specifically, the prodrug is converted to a sulfide by liver enzymes, then excreted via bile, and reabsorbed by the intestine. This helps maintain stable blood drug concentrations and reduces gastrointestinal side effects.
See also: Sulindac sodium (its active ingredient).

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Drug Indications
For the relief of symptoms and signs of osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, acute shoulder pain (acute subacromial bursitis/supraspinatus tendinitis) and acute gouty arthritis, for short-term or long-term use.
FDA Label

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Mechanism of Action
The exact mechanism of action of sulindac is not known. Its anti-inflammatory effect is thought to be through the inhibition of COX-1 and COX-2, thereby inhibiting the synthesis of prostaglandins. Its antipyretic effect may be due to its effect on the hypothalamus, leading to increased peripheral blood flow and vasodilation, thereby dissipating heat.

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Pharmacodynamics
Sulindac is a nonsteroidal anti-inflammatory indene derivative that also has analgesic and antipyretic effects.

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SulindacInhibits TGF-β1-induced lung cancer EMT and metastasis by downregulating SIRT1, which may be a novel antitumor mechanism in addition to traditional COX inhibition[1].
- In MMR-normal colorectal cancer, sulindac enhances the efficacy of anti-PD-L1 immunotherapy by increasing PD-L1 expression on tumor cells and promoting CD8+ T cell infiltration into the tumor microenvironment. This provides a theoretical basis for the combined use of sulindac and immune checkpoint inhibitors in MMR-normal colorectal cancer, a subtype that is often resistant to monotherapy immunotherapy [2]. Sulindac is a nonsteroidal anti-inflammatory drug (NSAID) with known anti-inflammatory and analgesic effects, but its antitumor potential (especially in lung and colorectal cancer) is supported by the results of these two studies [1, 2]. Unlike selective COX-2 inhibitors, sulindac inhibits both COX-1 and COX-2, but the studies did not attribute the observed antitumor effects to COX inhibition, suggesting the existence of COX-independent mechanisms (e.g., SIRT1 downregulation, immunomodulation) [1, 2].

C20H17FO3S

356.41

356.088

38194-50-2

Sulindac sulfide;49627-27-2;Sulindac sodium;63804-15-9;Sulindac-d3;Sulindac sulfone;59973-80-7

1548887

White to yellow solid powder

1.4±0.1 g/cm3

581.6±50.0 °C at 760 mmHg

182-185°C

305.6±30.1 °C

0.0±1.7 mmHg at 25°C

1.673

3.59

1

5

4

25

616

0

CC\1=C(C2=C(/C1=C\C3=CC=C(C=C3)S(=O)C)C=CC(=C2)F)CC(=O)O

MLKXDPUZXIRXEP-MFOYZWKCSA-N

InChI=1S/C20H17FO3S/c1-12-17(9-13-3-6-15(7-4-13)25(2)24)16-8-5-14(21)10-19(16)18(12)11-20(22)23/h3-10H,11H2,1-2H3,(H,22,23)/b17-9-

(Z)-2-(5-fluoro-2-methyl-1-(4-(methylsulfinyl)benzylidene)-1H-inden-3-yl)acetic acid

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 (7.01 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 (7.01 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.)