MLT-943 is a specific, orally bioactive MALT1 protease inhibitor. MLT-943 can inhibit the secretion of IL-2 in PBMC or whole blood. The IC50 of inhibition in PBMC is 0.07~0.09 μM, and the IC50 of inhibition in whole blood is 0.6~0.8 μM). MLT-943 exhibits anti-inflammatory effect and may be utilized to study FcgR-mediated inflammation.

Physicochemical Properties

Molecular Formula	C16H14CLF3N6O2
Molecular Weight	414.7696
Exact Mass	414.081
CAS #	1832576-04-1
PubChem CID	118540057
Appearance	White to off-white solid powder
LogP	1.8
Hydrogen Bond Donor Count	2
Hydrogen Bond Acceptor Count	8
Rotatable Bond Count	4
Heavy Atom Count	28
Complexity	557
Defined Atom Stereocenter Count	1
SMILES	ClC1C([H])=C2N=C([H])C(=C([C@]([H])(C([H])([H])[H])OC([H])([H])[H])N2N=1)N([H])C(N([H])C1C([H])=C([H])N=C(C(F)(F)F)C=1[H])=O
InChi Key	ZMPUACZRXUZAJD-QMMMGPOBSA-N
InChi Code	InChI=1S/C16H14ClF3N6O2/c1-8(28-2)14-10(7-22-13-6-12(17)25-26(13)14)24-15(27)23-9-3-4-21-11(5-9)16(18,19)20/h3-8H,1-2H3,(H2,21,23,24,27)/t8-/m0/s1
Chemical Name	1-[2-chloro-7-[(1S)-1-methoxyethyl]pyrazolo[1,5-a]pyrimidin-6-yl]-3-[2-(trifluoromethyl)pyridin-4-yl]urea
HS Tariff Code	2934.99.9001
Storage	Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month
Shipping Condition	Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Biological Activity

ln Vitro	In vitro, MLT-943 exhibits strong potency and selectivity. With comparable cross-species IC50s (0.07-0.09 μM in PBMC and 0.6-0.8 μM in whole blood), MLT-943 suppresses stimulated IL-2 secretion in both PBMC and whole blood [1].
ln Vivo	In a rat model of collagen-induced arthritis, prophylactic administration of MLT-943 (oral gavage; 10 mg/kg; QD) inhibits the generation of anti-collagen antibodies, completely prevents paw swelling, and enhances joint stability in the rat model. Scores based on histology were normalized[1]. MLT-943 (oral gavage; 5 mg/kg; QD; 10 days) reaches a maximum after 7 days of treatment and efficiently decreases MALT1 protease activity as well as the frequency of Foxp3+CD25+ Treg cells in circulating CD4+ T cells. After stopping MLT-943 treatment on day 10, Treg frequencies took four days to progressively recover to their initial levels. Treg frequency remained unaffected by suboptimal dosages of MLT-943 (0.1 and 0.5 mg/kg QD; po)[1]. In 4- and 13-week rat toxicity trials, MLT-943 (oral gavage; 0, 5, 20, or 80 mg/kg/day; 4–13 weeks) led to decreased Treg and total T cell counts at all treatment levels. Rats have a clinical onset of about 9 weeks, despite the fact that 4-Longer therapy promotes significant immune-mediated disease in several organs[1]. In vivo, MLT-943 (oral administration; 3 mg/kg; single dosage) shows positive PK characteristics. Rats and mice have Cmax values of 0.7 nM and 0.5 nM, respectively. Rats and mice have F%s of 86% and 50%, respectively[1]. Note: MC:Tween 80:Water (0.5:0.5:99) solution (from the literature, for reference only) is the solvent for oral administration, and NMP:PEG200 (30/70) solution is the solvent for intravenous administration[1].
Animal Protocol	Animal/Disease Models: Naïve rats[1] Doses: 5 mg/kg Route of Administration: Oral gavage; 5 mg/kg, 10 days or 0.1 mg/kg MLT-943 Experimental Results: Induced a severe immune-mediated pathology after a prolonged treatment
References	[1]. Pharmacological Inhibition of MALT1 Protease Leads to a Progressive IPEX-Like Pathology. Front Immunol. [2]. Optimization of the In Vivo Potency of Pyrazolopyrimidine MALT1 Protease Inhibitors by Reducing Metabolism and Increasing Potency in Whole Blood. J Med Chem. 2020 Dec 10;63(23):14594-14608.

Solubility Data

Solubility (In Vitro)

DMSO: 250 mg/mL (602.74 mM)

Solubility (In Vivo)

Solubility in Formulation 1: ≥ 2.08 mg/mL (5.01 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 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. Solubility in Formulation 2: ≥ 2.08 mg/mL (5.01 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.  (Please use freshly prepared in vivo formulations for optimal results.)

Preparing Stock Solutions		1 mg	5 mg	10 mg
	1 mM	2.4110 mL	12.0549 mL	24.1097 mL
	5 mM	0.4822 mL	2.4110 mL	4.8219 mL
	10 mM	0.2411 mL	1.2055 mL	2.4110 mL

*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.