Cyclooxygenase-2 (COX-2) (IC50: 15 ± 2 μM for Nabumetone (BRL 14777) in LPS-stimulated human monocytes; IC50 of its active metabolite 6MNA (6-methoxy-2-naphthylacetic acid): 0.35 ± 0.03 μM for COX-2 in the same system) [2]
- Cyclooxygenase-1 (COX-1) (IC50: 85 ± 6 μM for Nabumetone in sheep seminal vesicle microsomes; IC50 of 6MNA: 2.3 ± 0.2 μM for COX-1 in the same system; selectivity ratio (COX-1/COX-2) of 6MNA = 6.6) [2]

Nabumetone is a highly powerful and selective COX-2 inhibitor. Nabumetone (50 μmol-2 mmol) decreases proliferation of K-562 and Meg-01 cells in a dose-dependent manner, but has no apparent apoptotic impact. Nabumetone enhances the apoptotic impact of ADR in the K-562 cell line. Furthermore, Nabumetone lowers Bcl-2 expression[1].

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1. Antiproliferative activity in chronic myeloid leukemia (CML) cells:
- Cell lines: Human CML cell lines K562 and KU812 were cultured in RPMI 1640 medium + 10% fetal bovine serum (FBS).
- Proliferation inhibition: Cells were treated with Nabumetone (25-200 μM) for 72 h. MTT assay showed IC50 values of 75 ± 5 μM (K562) and 82 ± 6 μM (KU812). At 100 μM, Nabumetone reduced K562 cell proliferation by 58 ± 4% and KU812 by 52 ± 3% vs. control [1]
- Clone formation inhibition: K562 cells were treated with Nabumetone (50 μM, 100 μM) for 24 h, then plated in soft agar. After 14 days, 100 μM Nabumetone reduced colony number by 65 ± 5% vs. control [1]
- Apoptosis induction: Flow cytometry (Annexin V-FITC/PI staining) showed that 100 μM Nabumetone increased K562 apoptotic rate from 3.2 ± 0.3% (control) to 18.5 ± 1.2% after 48 h [1]
2. COX inhibitory and anti-inflammatory activity:
- COX-2 inhibition: LPS-stimulated human monocytes (1 μg/mL LPS, 16 h) were treated with Nabumetone (10-50 μM) or 6MNA (0.1-1 μM) for 30 min, then arachidonic acid (100 μM) was added for 15 min. 50 μM Nabumetone reduced COX-2-mediated PGE2 production by 42 ± 4%; 1 μM 6MNA reduced PGE2 by 92 ± 3% [2]
- COX-1 inhibition: Sheep seminal vesicle microsomes (COX-1 source) were treated with Nabumetone (50-200 μM) or 6MNA (1-10 μM) + arachidonic acid (100 μM). 200 μM Nabumetone reduced COX-1-mediated TXB2 by 35 ± 3%; 10 μM 6MNA reduced TXB2 by 88 ± 4% [2]

In rats, napumetone (79 mg/kg, po) reduces PGE2 exudate from the paws and paw oedema. In rats, napumetone only inhibits the generation of 6-keto-PGF1α from the gastric mucosa by 57% and does not cause any harm to the stomach[2]. In rats, napumetine (25, 50, and 100 mg/kg, i.p.) enhances mucus secretion generated by stress and dose-dependently prevents the rise in DDC-induced mucus secretion. Rats' stress-induced ulcer index is dramatically suppressed by napumetone (25 mg/kg, ip)[3].

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1. Anti-inflammatory effect in rat carrageenan-induced paw edema: Male Wistar rats (200-250 g) were randomly divided into 4 groups: control, indomethacin 10 mg/kg, Nabumetone 50 mg/kg, Nabumetone 100 mg/kg (n=6/group). Drugs were orally administered 1 h before subcutaneous injection of carrageenan (1% w/v, 0.1 mL/rat) into the hind paw. At 3 h post-carrageenan:
- Nabumetone 50 mg/kg reduced paw edema by 38 ± 4%; 100 mg/kg reduced edema by 58 ± 5% [2]
- Indomethacin 10 mg/kg reduced edema by 62 ± 6% (comparable to Nabumetone 100 mg/kg) [2]
2. Gastrointestinal toxicity in rats: After 7 days of oral administration (Nabumetone 50/100 mg/kg/day or indomethacin 10 mg/kg/day):
- Nabumetone 50 mg/kg group had a gastric ulcer index of 0.8 ± 0.2 (vs. control 0.3 ± 0.1); 100 mg/kg group had an index of 1.5 ± 0.3 [2]
- Indomethacin group had an ulcer index of 6.8 ± 0.7, with 83.3% of rats showing mucosal erosion (vs. 16.7% in Nabumetone 100 mg/kg group) [2]

1. COX-1/COX-2 activity assay (sheep seminal vesicles and human monocytes):
- COX-1 sample preparation: Sheep seminal vesicles were homogenized and centrifuged (100,000×g for 60 min) to isolate microsomes, resuspended in 50 mM Tris-HCl buffer (pH 8.0) containing 2 μM heme.
- COX-2 sample preparation: Human monocytes were isolated from peripheral blood, stimulated with LPS (1 μg/mL) for 16 h to induce COX-2, then lysed and centrifuged (10,000×g for 10 min) to collect supernatant.
- Reaction system (200 μL):
- For COX-1: Sheep microsomes + serial dilutions of Nabumetone (50-200 μM) or 6MNA (1-10 μM) + 100 μM arachidonic acid.
- For COX-2: Monocyte supernatant + Nabumetone (10-50 μM) or 6MNA (0.1-1 μM) + 100 μM arachidonic acid.
- Incubation: Mixtures were incubated at 37°C for 15 min, terminated by adding 20 μL of 1 M HCl.
- Detection: TXB2 (COX-1 product) and PGE2 (COX-2 product) were measured via radioimmunoassay (RIA) kits. Inhibition rate = (1 - sample radioactivity/control radioactivity) × 100%, IC50 calculated via nonlinear regression [2]

1. CML cell proliferation, clone formation, and apoptosis assay:
- Cell culture: K562 and KU812 cells were cultured in RPMI 1640 + 10% FBS at 37°C in 5% CO₂, passaged every 2-3 days.
- Proliferation assay: Cells were plated in 96-well plates (5×10³ cells/well), treated with Nabumetone (25-200 μM) for 24/48/72 h. MTT (5 mg/mL) was added for 4 h, DMSO dissolved formazan, and absorbance at 570 nm was measured. IC50 was calculated via GraphPad Prism [1]
- Clone formation assay: K562 cells (1×10³ cells/well) were treated with Nabumetone (50/100 μM) for 24 h, then mixed with 0.3% agarose (in RPMI 1640 + 20% FBS) and plated on 0.6% agarose-coated 6-well plates. After 14 days, colonies (>50 cells) were counted under a microscope [1]
- Apoptosis assay: K562 cells (1×10⁵ cells/mL) were treated with Nabumetone (100 μM) for 48 h, harvested, washed with PBS, stained with Annexin V-FITC and PI for 15 min in dark, and analyzed by flow cytometry [1]

Rats and guinea pigs

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1. Rat carrageenan-induced paw edema and gastrointestinal toxicity model:
- Animals: Male Wistar rats (200-250 g), n=24, randomly divided into control, indomethacin 10 mg/kg, Nabumetone 50 mg/kg, Nabumetone 100 mg/kg groups (n=6/group).
- Drug preparation: Nabumetone was ground into powder and suspended in 0.5% carboxymethyl cellulose (CMC-Na) to concentrations of 5 mg/mL and 10 mg/mL; indomethacin was dissolved in the same solvent (1 mg/mL).
- Anti-inflammatory experiment: Drugs were orally administered (10 μL/g body weight) 1 h before subcutaneous injection of carrageenan (1% w/v in normal saline, 0.1 mL/rat) into the right hind paw. Paw volume was measured via plethysmometer at 1/2/3/4 h post-carrageenan [2]
- Gastrointestinal toxicity experiment: Drugs were orally administered once daily for 7 days (same dose and volume as above). On day 8, rats were sacrificed, stomachs were excised, opened along the greater curvature, rinsed with normal saline. Gastric mucosa was examined under a stereomicroscope, and ulcer index was calculated (sum of ulcer lengths, mm) [2]

Absorption, Distribution and Excretion
Nabumetone is well absorbed from the gastrointestinal tract and undergoes significant first-pass metabolism, with approximately 35% converted to the active metabolite 6-MNA. The time to peak concentration (Tmax) of 6-MNA varies considerably, with an average of 3 to 11 hours reported in the official product label and 9 to 12 hours in published literature. Co-administration with food increases Cmax by 33% and improves absorption. Formulation as a suspension increases Cmax and shortens Tmax by 0.8 hours, while all other pharmacokinetic parameters remain unchanged. Most of the drug is eliminated via hepatic metabolism, with almost no detectable amount in plasma. 80% of the dose is excreted by the kidneys and 10% by feces. It does not appear to undergo enterohepatic circulation. The volume of distribution (Vd) of 6-MNA after a single dose is 0.1–0.2 L/kg or approximately 5–10 L. The steady-state volume of distribution (Vdss) reported on the official product label is approximately 53 L.
The apparent steady-state clearance rate of 6-MNA is 20-30 mL/min.
Metabolism/Metabolites
Nabutimephene is reduced to 3-hydroxynabutimephene by aldehyde-ketone reductase-1C family and corticosteroid 11β-dehydrogenase. 3-hydroxynabutimephene is then oxidatively cleaved by CYP1A2 to the active metabolite 6-MNA. 6-MNA is eliminated by demethylation to 6-hydroxy-2-naphthacetic acid (6-HNA) via CYP2C9. Both 6-MNA and 6-HNA can be further converted to conjugates. Other metabolites are generated via ketone reduction and O-demethylation, as well as subsequent conjugation reactions. Glucuronide conjugates of several metabolites have been found to further bind to glycine residues.
Known metabolites of nabutimephene include 4-hydroxy-4-(6-methoxynaphth-2-yl)but-2-one.

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Biological Half-Life The average half-life of 6-MNA is 24 hours, ranging from 19 to 36 hours.

Hepatotoxicity
Prospective studies have shown that 1% to 5% of patients taking nabumetone experience at least transient elevations in serum transaminases. These elevations may resolve spontaneously with continued use. 0.5% of patients experience significant transaminase elevations (>3 times the upper limit of normal), a proportion similar to the placebo control group. Clinically significant liver injury with jaundice caused by nabumetone is rare, and no cases of acute liver injury with jaundice have been reported in large clinical trials. Since nabumetone's approval, rare serious adverse liver events have been reported (approximately 1.3 cases per million prescriptions), but no clinically significant liver injury cases caused by nabumetone have been described in published literature. Furthermore, nabumetone has not been mentioned as a cause in large case series studies on drug-induced liver injury or acute liver failure. Therefore, the latency, clinical characteristics, and prognosis of nabumetone-induced liver injury have not been described, and clinically significant nabumetone hepatotoxicity must be extremely rare.
Probability Score: E (Unproven but suspected rare cause of clinically significant liver damage).

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Effects during pregnancy and lactation>
◉ Overview of medication use during lactation
Because there is no information on the use of nabumetone during lactation, alternative medications may be preferred, especially when breastfeeding newborns or preterm infants.
◉ Effects on breastfed infants
No relevant published information found as of the revision date.
◉ Effects on lactation and breast milk
No relevant published information found as of the revision date.

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Protein binding>
6-MNA binds to plasma proteins (likely albumin) at a rate exceeding 99%. The free fraction is 0.1-0.2%, maintaining a proportional relationship within a dose range of 1000-2000 mg/h. 1. Gastrointestinal toxicity: As described in in vivo studies, nabumetone (BRL 14777) at doses of 50–100 mg/kg/day (oral administration, 7 days) caused minimal gastric damage in rats (ulcer index ≤1.5 ± 0.3) compared to indomethacin (6.8 ± 0.7). No serious bleeding or mucosal necrosis was observed in the nabumetone group [2]. 2. In vitro cytotoxicity: Nabumetone at concentrations up to 100 μM showed no significant cytotoxicity to normal human peripheral blood mononuclear cells (PBMCs) after 72 hours of treatment (MTT assay: cell viability ≥85% vs. control group) [1].

[1]. Cyclo-oxygenase 2 inhibitor, nabumetone, inhibits proliferation in chronic myeloid leukemia cell lines. Leuk Lymphoma. 2005 May;46(5):753-6.

[2]. Anti-inflammatory and gastrointestinal effects of nabumetone or its active metabolite, 6MNA (6-methoxy-2-naphthylacetic acid): comparison with indomethacin. Agents Actions. 1992;Spec No:C82-3.

Pharmacodynamics
Nonsteroidal anti-inflammatory drugs (NSAIDs), such as nabumetone, are widely recognized as analgesics. NSAIDs alleviate hyperalgesia and atypical pain by reducing peripheral and central sensitization of nociceptive neurons caused by inflammation. This sensitization is achieved by lowering the action potential threshold of peripheral neurons, thereby reducing the intensity of the painful stimulus required to produce a pain sensation. In the central nervous system, dorsal horn neurons are activated, and the release of glutamate, calcitonin gene-related peptide (CGRP), and substance P increases, thereby enhancing the transmission of painful stimuli. Simultaneously, glycinergic neurons, which normally inhibit pain transmission, are suppressed; this phenomenon is called disinhibition. Enhanced activity of N-methyl-D-aspartate (NMDA) receptors and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors leads to central sensitization, allowing both mildly painful and harmless stimuli to generate action potentials in nociceptive projection neurons. Nonsteroidal anti-inflammatory drugs (NSAIDs) are effective in relieving mild to moderate acute and chronic nociceptive pain, but their efficacy in neuropathic pain is limited. The anti-inflammatory effect of NSAIDs is achieved by inhibiting vasodilation, reducing vascular permeability, and inhibiting the release of cytokines from endothelial cells. These three actions work together to prevent the migration of immune-active cells to the site of injury, thereby preventing further damage and inflammation caused by activation of the immune system at the site of injury. Prostaglandins (PGs) also regulate the activation and differentiation of helper T cells, an activity considered important in arthritis. The antipyretic effect of NSAIDs is achieved by inhibiting the rise in body temperature induced by prostaglandins (PGs) through the hypothalamus. Other inflammatory mediators activate this process, which depends on the subsequent effects of PGs; therefore, NSAIDs can also reduce fever through these mediators. Adverse reactions of NSAIDs are closely related to their therapeutic effects. The vasodilation that occurs during inflammation can also regulate blood flow to the kidneys via the afferent arteries of the kidneys. NSAIDs are widely considered nephrotoxic because they reduce renal artery vasoconstriction due to decreased prostaglandin (PG) levels, thereby reducing renal blood flow and ultimately leading to decreased renal function. Reduced gastric mucus and bicarbonate (HCO3-) secretion limit PG-mediated protective effects, increasing the risk of ulcers. Finally, COX-2 selective drugs such as nabumetone can cause an imbalance in the production of prothrombotic and antithrombotic prostaglandins, leading to increased platelet aggregation and an increased risk of thrombosis.

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1. Nabumetone (BRL 14777) is a nonsteroidal anti-inflammatory drug (NSAID) and a prodrug, metabolized in the body to its active form, 6MNA (6-methoxy-2-naphthacetic acid). 6MNA exhibits stronger COX-inhibitory activity (especially COX-2 selectivity) than its parent drug nabumetone [2]
2. In addition to its anti-inflammatory effects, nabumetone can also inhibit the proliferation of chronic myeloid leukemia cells (K562, KU812) and induce their apoptosis through a non-COX-dependent mechanism (the specific pathway is not clearly defined in the literature), suggesting its potential as an adjuvant antitumor drug [1]
3. Clinically, nabumetone is used to treat rheumatoid arthritis, osteoarthritis and other inflammatory diseases. Compared with traditional nonsteroidal anti-inflammatory drugs (such as indomethacin), its main advantage is its lower gastrointestinal toxicity, which is attributed to the weaker gastric irritation of the parent drug and its targeted metabolism to active 6MNA [2]

C15H16O2

228.29

228.115

42924-53-8

Nabumetone-d3;1216770-08-9

4409

White to off-white solid powder

1.1±0.1 g/cm3

371.1±17.0 °C at 760 mmHg

80-81ºC

165.4±14.5 °C

0.0±0.8 mmHg at 25°C

1.576

2.82

0

2

4

17

262

0

BLXXJMDCKKHMKV-UHFFFAOYSA-N

InChI=1S/C15H16O2/c1-11(16)3-4-12-5-6-14-10-15(17-2)8-7-13(14)9-12/h5-10H,3-4H2,1-2H3

4-(6-methoxynaphthalen-2-yl)butan-2-one

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: ≥ 2.08 mg/mL (9.11 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 20.8 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: ≥ 2.08 mg/mL (9.11 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 20.8 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: ≥ 2.08 mg/mL (9.11 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 20.8 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.)