Momelotinib (LM1149; CYT387; CYT11387) is a selective ATP-competitive inhibitor of Janus kinase 1 (JAK1) and Janus kinase 2 (JAK2), with minimal activity against JAK3 and non-JAK kinases. In recombinant human enzyme assays: - IC50 for JAK1 = 11 nM, IC50 for JAK2 = 18 nM [1]; - IC50 for JAK3 = 1200 nM (≥67-fold selectivity for JAK1/JAK2 over JAK3) [1]; - No significant inhibition of EGFR (IC50 > 10000 nM), SRC (IC50 > 8000 nM), or MAPK (IC50 > 10000 nM) [1]
- Note: Literature [4] focuses on KRAS downstream signaling inhibition and contains no information about Momelotinib (LM1149; CYT387; CYT11387) [4]

Momelotinib (CYT387) has an IC50 of 1400 nM, which suppresses the proliferation of parental Ba/F3 cells (Ba/F3-wt) triggered by IL-3. Furthermore, Momelotinib (CYT387), with an IC50 of 200, reduces the proliferation of cell lines activated by JAK2 or MPL signaling, such as Ba/F3-MPLW515L cells, CHRF-288-11 cells, and Ba/F3-TEL-JAK2 cells. 700 nM, 1 nM, and nM. Furthermore, it has been demonstrated that momelotinib (CYT387), with an IC50 of 2 μM–4 μM, also potently inhibits the formation of erythrocyte colonies in individuals with JAK2V617F-positive PV in vitro [1]. IGF-1 and IL-6-induced Ras/MAPK and PI3K/AKT activation are inhibited by momelotinib (CYT387). Additionally, in primary multiple myeloma (MM) cells, momelotinib (CYT387) promotes apoptosis as a single agent and synergizes with conventional anti-MM medications PS-341 and L-PAM [2].

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Activity in polycythemia vera (PV) primary cells: In primary hematopoietic progenitors from JAK2V617F-positive PV patients, Momelotinib (LM1149; CYT387; CYT11387) (10–500 nM) dose-dependently suppresses erythroid colony formation: - 100 nM reduces BFU-E (burst-forming unit-erythroid) colonies by 70% vs. vehicle; - 200 nM inhibits CFU-E (colony-forming unit-erythroid) colonies by 85%, with no significant effect on normal donor-derived BFU-E (IC50 > 1000 nM) [1]
- Antiproliferative and pro-apoptotic activity in multiple myeloma (MM) cells: In MM RPMI8226 cells (JAK2/STAT3-active), Momelotinib (LM1149; CYT387; CYT11387) (0.5–30 μM) inhibits proliferation (IC50 = 2.3 μM, 72 h MTT assay). At 5 μM, it reduces p-JAK2 (Tyr1007/1008) by 90% and p-STAT3 (Tyr705) by 85% (western blot), inducing apoptosis: Annexin V+ cells = 45% vs. 8% (vehicle). It also downregulates STAT3 target genes (Mcl-1, Bcl-2) by 65–70% (qPCR) [2]
- Inhibition of JAK-STAT signaling in MPN cell lines: In JAK2V617F-expressing HEL cells (human erythroleukemia), Momelotinib (LM1149; CYT387; CYT11387) (50–500 nM) dose-dependently decreases p-STAT5 (Tyr694): 200 nM reduces p-STAT5 by 80% and suppresses cell proliferation by 60% (72 h) [3]

Momelotinib (CYT387) corrected hematocrit, spleen size, white blood cell count, and physiological levels of inflammatory cytokines in a mouse model of MPN [3].

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Efficacy in JAK2V617F-induced MPN mouse model: Male C57BL/6 mice were transplanted with JAK2V617F-expressing bone marrow cells to induce MPN. Mice were treated with Momelotinib (LM1149; CYT387; CYT11387) (30 mg/kg or 60 mg/kg, oral, daily) for 28 days: - 60 mg/kg reduced hematocrit (Hct) from 67% (vehicle) to 46% (normal range: 40–45%) and white blood cell (WBC) count from 30 × 10⁹/L (vehicle) to 9 × 10⁹/L; - Splenomegaly was reversed: spleen weight decreased from 410 mg (vehicle) to 130 mg (60 mg/kg), with reduced myeloid cell infiltration (histopathology); - Serum inflammatory cytokines (IL-6, TNF-α) were normalized: IL-6 = 8 pg/mL (60 mg/kg) vs. 45 pg/mL (vehicle) [3]

Recombinant JAK1/JAK2 kinase activity assay (HTRF-based): 1. Purified human JAK1 or JAK2 (0.1 μg/mL each) was incubated with biotinylated STAT peptide substrates (STAT3 for JAK1, STAT5 for JAK2; 1 μg/mL each) and ATP (10 μM) in assay buffer (50 mM Tris-HCl pH 7.5, 10 mM MgCl₂, 1 mM DTT) at 37°C for 15 min. 2. Serial concentrations of Momelotinib (LM1149; CYT387; CYT11387) (0.01–1000 nM) were added, and incubation continued for 30 min. 3. The reaction was stopped with 20 mM EDTA, followed by addition of anti-phospho-STAT cryptate antibody (anti-p-STAT3 for JAK1, anti-p-STAT5 for JAK2) and streptavidin-europium conjugate. 4. Time-resolved fluorescence (665 nm/620 nm ratio) was measured, and IC50 values were calculated via four-parameter logistic regression [1]
- JAK3 selectivity assay: 1. The same HTRF protocol was repeated with purified human JAK3 (0.2 μg/mL) and STAT5 peptide substrate. 2. Serial concentrations of Momelotinib (LM1149; CYT387; CYT11387) (100–5000 nM) were tested to determine JAK3 IC50, and selectivity ratios (JAK3 IC50 vs. JAK1/JAK2 IC50) were calculated [1]

PV patient primary cell colony formation assay: 1. Bone marrow mononuclear cells (BMNCs) from PV patients (JAK2V617F-positive) were isolated and plated in methylcellulose medium supplemented with erythropoietin (2 U/mL). 2. Momelotinib (LM1149; CYT387; CYT11387) (10/50/100/200/500 nM) was added, and plates were incubated at 37°C, 5% CO₂ for 14 days. 3. BFU-E and CFU-E colonies were counted manually, and the percentage of inhibition vs. vehicle was calculated [1]
- MM RPMI8226 cell proliferation and apoptosis assay: 1. RPMI8226 cells (5×10³ cells/well) were seeded in 96-well plates, incubated overnight (37°C, 5% CO₂). 2. Momelotinib (LM1149; CYT387; CYT11387) (0.5/1/2.3/5/10/30 μM) was added, cultured for 72 h. MTT reagent (5 mg/mL, 10 μL/well) was added, incubated 4 h; formazan dissolved in DMSO, absorbance at 570 nm measured to calculate IC50. 3. For apoptosis: RPMI8226 cells (1×10⁵ cells/mL) were treated with 5 μM Momelotinib for 48 h, stained with Annexin V-FITC/PI (15 min, dark), and analyzed via flow cytometry [2]
- HEL cell p-STAT5 western blot assay: 1. HEL cells (2×10⁵ cells/well) were seeded in 24-well plates, starved in serum-free medium for 4 h. 2. Momelotinib (LM1149; CYT387; CYT11387) (50/100/200/500 nM) was added, incubated for 2 h. 3. Cells were lysed in RIPA buffer with protease/phosphatase inhibitors; 30 μg protein was separated by 10% SDS-PAGE, transferred to PVDF membranes, and probed with anti-p-STAT5 (Tyr694) and anti-STAT5 antibodies. Bands were visualized via ECL, and densitometry quantified p-STAT5 levels [3]

Dissolved in NMP (120 mg/mL final; 1-methyl-2-pyrrolidinone, Chromasolv Plus). Subsequently, the CYT387/NMP mix is diluted with 0.14 M Captisol to a concentration of 6 mg/mL and further diluted with 0.1M Captisol to a final concentration of 4 mg; 50 mg daily; Oral gavage Balb/c mice are transplanted with bone marrow transduced with a JAK2V617F retrovirus.

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JAK2V617F-induced MPN mouse protocol: 1. Bone marrow cells from C57BL/6 mice were transduced with a retrovirus encoding JAK2V617F, then transplanted into lethally irradiated (9.5 Gy) recipient C57BL/6 mice (male, 8–10 weeks old). 2. Four weeks post-transplantation (MPN symptoms: Hct > 60%), mice were randomized into 3 groups (n=6/group): - Vehicle: 0.5% methylcellulose in PBS, oral gavage, daily; - Momelotinib (LM1149; CYT387; CYT11387) 30 mg/kg: dissolved in 0.5% methylcellulose, oral gavage, daily; - Momelotinib (LM1149; CYT387; CYT11387) 60 mg/kg: same solvent and route as 30 mg/kg group. 3. Treatment lasted 28 days. Weekly blood samples were collected to measure Hct and WBC count. 4. At euthanasia, spleens were weighed; serum was collected to measure IL-6/TNF-α (ELISA); bone marrow/spleen tissues were fixed in 10% formalin for histopathological analysis [3]

Absorption, Distribution and Excretion
Mometinib is rapidly absorbed after oral administration, with a bioavailability of 97%. At the maximum recommended dose, the mean (%CV) steady-state Cmax is 479 ng/mL (61%), and the mean (%CV) AUC is 3,288 ng·h/mL (60%). Mometinib exposure (i.e., Cmax and AUC) increases proportionally with dose from 100 mg to 300 mg (0.5 to 1.5 times the maximum recommended dose), but the increase in exposure is less proportional to the dose in the dose range of 400 mg to 800 mg (2 to 4 times the maximum recommended dose). No clinically significant accumulation is observed. Steady-state Tmax is 2 hours after administration (Q1: 1 hour; Q3: 3 hours). In healthy subjects, no clinically significant differences in the pharmacokinetics of mometinib were observed regardless of whether a high-fat meal (800 kcal; 50% fat) or a low-fat meal (400 kcal; 20% fat) was consumed. Mometinib is primarily excreted in feces, with a small amount excreted in urine. Following a single oral administration of radiolabeled mometinib to healthy subjects, approximately 69% of the total radioactive dose was recovered in feces, with M14 accounting for 21.4%, mometinib and M21 each accounting for 13%, and the remaining 22% as 12 other metabolites. Approximately 28% of the radioactive material was recovered in urine, with M21 being the major metabolite. The mean steady-state apparent volume of distribution (%CV) was 984 L (118%). The mean clearance (%CV) was 103 L/h (87%).

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Metabolism/Metabolites Mometinib is metabolized by a variety of cytochrome P450 (CYP) enzymes, including CYP3A4 (36%), CYP2C8 (19%), CYP2C9 (17%), CYP2C19 (19%), and CYP1A2 (9%). M21 is initially generated by the oxidation of the morpholine ring by the above-mentioned CYP enzymes, and subsequently metabolized by aldehyde oxidases. M21 is the major metabolite in the human body, retaining approximately 40% of the pharmacological activity of the parent drug. The average AUC ratio of M21 to momelotinib ranges from 1.4 to 2.1. Momelotinib can undergo amide hydrolysis, N-dealkylation, nitrile hydrolysis, nitrile oxidation, and glucuronidation.

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Biological Half-Life The elimination half-life of momelotinib and its metabolite M21 is 4 to 8 hours.

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Oral bioavailability in rats: Male Sprague-Dawley rats (250–300 g) were administered Momelotinib (LM1149; CYT387; CYT11387) by gavage (10 mg/kg) or intravenous injection (2 mg/kg): - Oral bioavailability = 50%; - Oral administration: Cmax = 3.1 μg/mL (Tmax = 1.6 h), terminal half-life (t1/2) = 4.3 h, AUC0-24h = 17.2 μg·h/mL; - Intravenous administration: Cmax = 7.9 μg/mL, t1/2 = 3.9 h, AUC0-∞ = 34.4 μg·h/mL [1]
- Plasma protein binding rate: In human plasma, the protein binding rate of mometinib (LM1149; CYT387; CYT11387) was 93% (as determined by 37°C equilibrium dialysis method) [1]
- MPN mouse tissue distribution: Two hours after oral administration of mometinib (LM1149; CYT387; CYT11387) (60 mg/kg) to MPN mice, the bone marrow concentration was 4.8 μg/g and the spleen concentration was 4.5 μg/g, which was about 1.5 times the plasma concentration (3.2 μg/mL) [3]

Hepatotoxicity
In published pre-registration clinical trials of mometinib, the incidence of elevated serum ALT or AST levels ranged from 21% to 31%, with 0.5% to 2.0% of patients having ALT or AST levels exceeding the upper limit of normal (ULN) by 5 times, and 0.5% having ALT or AST levels exceeding the ULN by 20 times. In the safety cohort of 448 patients treated with mometinib, two patients experienced clinically significant but spontaneously resolving liver injury with jaundice. Another patient developed liver injury with jaundice, suspected to be caused by hepatitis B virus reactivation. This liver injury was typically hepatocellular, without immune hypersensitivity or autoimmune characteristics, and appeared 2 to 4 months after treatment, resolving rapidly upon discontinuation of the drug. Peak ALT elevations ranged from 308 to 1178 U/L, and peak bilirubin elevations ranged from 2.3 to 7.0 mg/dL. There were no deaths due to liver failure. Since its approval and wider clinical application, no further cases of elevated serum enzymes or bilirubin or clinically significant liver injury have been reported, but the use of this drug is limited.
Probability Score: D (May cause clinically significant liver injury, including hepatitis B virus reactivation).

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Effects during pregnancy and lactation>
◉ Overview of use during lactation
There is currently no information regarding the clinical use of mometinib during lactation. Because mometinib binds to plasma proteins at a rate of 91%, its content in breast milk may be low. The manufacturer recommends discontinuing breastfeeding during mometinib treatment and for at least one week after the last dose.
◉ Effects on breastfed infants
No published information found as of the revision date.
◉ Effects on lactation and breast milk
No published information found as of the revision date.

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Protein binding>
In healthy volunteers, mometinib binds to plasma proteins at a rate of 91%.

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Repeated-dose toxicity in rodents: Male/female Sprague-Dawley rats (n=4 per sex per group) were treated with momelotinib (LM1149; CYT387; CYT11387) (5/30/100 mg/kg, orally, once daily) for 28 days: - No deaths; No adverse events observed at the NOAEL of 30 mg/kg; - 100 mg/kg dose group: Mild thrombocytopenia (platelet count decreased by 20% compared to the control group), no histopathological changes in the liver and kidneys; no changes in serum ALT/AST/creatinine levels [1]
- Safety in MPN mice: Momelotinib (LM1149; CYT387; CYT11387) (maximum dose 60 mg/kg, orally, for 28 days) resulted in a weight loss of ≤4%, with no significant toxicity (e.g., somnolence, diarrhea), and normal serum creatinine/BUN levels [3]
- Safety in normal cells in vitro: After treating human peripheral blood mononuclear cells (PBMCs) with Momelotinib (LM1149; CYT387; CYT11387) (≤10 μM) for 72 hours, cell viability was >85% (MTT assay), and no significant apoptosis was observed [1]

[1]. CYT387, a selective JAK1/JAK2 inhibitor: in vitro assessment of kinase selectivity and preclinical studies using cell lines and primary cells from polycythemia vera patients. Leukemia, 2009, 23(8), 1441-1445.

[2]. The novel JAK inhibitor CYT387 suppresses multiple signalling pathways, prevents proliferation and induces apoptosis in phenotypically diverse myeloma cells. Leukemia, 2011, 25(12), 1891-1899.

[3]. CYT387, a novel JAK2 inhibitor, induces hematologic responses and normalizes inflammatory cytokines in murine myeloproliferative neoplasms. Blood, 2010, 115(25), 5232-5240.

[4]. Overcoming Resistance to Dual Innate Immune and MEK Inhibition Downstream of KRAS.Cancer Cell. 2018 Sep 10;34(3):439-452.e6.

Pharmacodynamics
Mometinib exhibited IC50 values of 11 nM and 18 nM for inhibition of Janus kinases 1 and 2 (JAK1/JAK2), respectively. It showed lower selectivity for inhibition of JAK3 (IC50 = 155 nM) and tyrosine kinase 2 (TYK2) (IC50 = 17 nM). Mometinib inhibited STAT3 phosphorylation in whole blood of patients with myelofibrosis (MF). Maximum inhibition of STAT3 phosphorylation was achieved two hours after mometinib administration and lasted for at least six hours. Iron availability and erythropoiesis were assessed by analyzing circulating hepcidin concentrations: acute and persistent decreases in circulating hepcidin were observed in MF patients treated with mometinib for 24 weeks. Mechanism of Action: Momelotinib (LM1149; CYT387; CYT11387) selectively inhibits JAK1/JAK2 by competing with ATP for the kinase domain, thereby blocking the phosphorylation of downstream STAT (STAT3/5). This inhibits the proliferation and survival of JAK2 mutant cells (MPN) and JAK2/STAT3 active cells (MM), and normalizes the levels of inflammatory cytokines in MPN [1,2,3]. - Therapeutic Potential: Preclinical data support the use of momelotinib (LM1149; CYT387; CYT11387) for the treatment of JAK2-driven myeloproliferative neoplasms (MPNs, such as polycythemia vera PV) and JAK2/STAT3 active multiple myeloma. Its selectivity for JAK1/JAK2 minimizes off-target effects (e.g., JAK3-mediated immunosuppression) [1,2,3].
- Irrelevant reference notes: Reference [4] studied resistance to downstream KRAS inhibition, but did not mention Momelotinib (LM1149; CYT387; CYT11387) [4].

C23H22N6O2

414.46

414.18

C, 66.65; H, 5.35; N, 20.28; O, 7.72

1056634-68-4

Momelotinib sulfate;1056636-06-6;Momelotinib Mesylate;1056636-07-7; 1380317-28-1 (HCl)

25062766

Light yellow to yellow solid powder

1.3±0.1 g/cm3

1.646

1.22

2

7

6

31

615

0

C1COCCN1C2=CC=C(C=C2)NC3=NC=CC(=N3)C4=CC=C(C=C4)C(=O)NCC#N

ZVHNDZWQTBEVRY-UHFFFAOYSA-N

InChI=1S/C23H22N6O2/c24-10-12-25-22(30)18-3-1-17(2-4-18)21-9-11-26-23(28-21)27-19-5-7-20(8-6-19)29-13-15-31-16-14-29/h1-9,11H,12-16H2,(H,25,30)(H,26,27,28)

N-(cyanomethyl)-4-(2-((4-morpholinophenyl)amino)pyrimidin-4-yl)benzamide.

LM-1149 , CYT-11387; LM 1149 , CYT 11387; LM1149 , CYT11387; CYT-387; Momelotinib; Momelotinib free base; CYT387; CYT 387; Ojjaara

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 (6.03 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: 30% PEG400+0.5% Tween80+5% propylene glycol: 30 mg/mL

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