Tovinontrine, also known as IMR-687, is a phosphodiesterase 9 (PDE9) inhibitor. IMR-687 increases cGMP and HbF in erythroid K562 and UT-7 cells and increases the percentage of HbF-positive erythroid cells generated in vitro in two-phase liquid cultures using CD34+ progenitor cells from sickle cell blood or bone marrow. . Daily oral administration of IMR-687 increased HbF and reduced erythrocyte sickling, immune cell activation, and microvascular stasis in the Townes transgenic mouse model of SCD.

Physicochemical Properties

Molecular Formula	C21H26N6O2
Molecular Weight	394.470143795013
Exact Mass	394.21
Elemental Analysis	C, 63.94; H, 6.64; N, 21.30; O, 8.11
CAS #	2062661-53-2
PubChem CID	124220601
Appearance	White to off-white solid powder
LogP	0.4
Hydrogen Bond Donor Count	1
Hydrogen Bond Acceptor Count	6
Rotatable Bond Count	4
Heavy Atom Count	29
Complexity	631
Defined Atom Stereocenter Count	2
SMILES	C[C@@H]1CN(C[C@H]1C2=CN3C(=CN=C3C4CCOCC4)C(=O)N2)CC5=NC=CC=N5
InChi Key	GWGNPYYVGANHRJ-GDBMZVCRSA-N
InChi Code	InChI=1S/C21H26N6O2/c1-14-10-26(13-19-22-5-2-6-23-19)11-16(14)17-12-27-18(21(28)25-17)9-24-20(27)15-3-7-29-8-4-15/h2,5-6,9,12,14-16H,3-4,7-8,10-11,13H2,1H3,(H,25,28)/t14-,16-/m1/s1
Chemical Name	6-{(3S,4S)-4-methyl-1-[(pyrimidin-2-yl)methyl]pyrrolidin-3-yl}-3-(oxan-4-yl)imidazo[1,5-a]pyrazin-8(7H)-one
Synonyms	Tovinontrine; IMR-687; IMR 687; IMR687;
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	IMR-687 has an inhibitory efficacy of about 800 times greater than PDE9A, PDE1A3, PDE1B, PDE1C, and PDE5A2, with IC50 values of 88.4 μM, 8.48 μM, 12.2 μM, and 81.9 μM, in that order [1]. Hemoglobin (HbF) is generated in K562 cells for 72 hours in red blood cells by IMR-687 (0.1–10 μM) in a dose-dependent manner [1]. In erythroid K562 cells, IMR-687 (0.03-10 μM) raises cGMP in a dose-dependent manner over a 6-hour period [1].
ln Vivo	IMR-687 (30 mg/kg/day; after 30 days of therapy) demonstrated a more than 3-fold rise in the percentage of HbF+ F cells (vehicle treatment: 8.4%, IMR-687 treatment: 27.3%) and a similar 2-fold reduction in sickle red cells ( Carrier treatment: 56.3% and IMR-687 treatment: 24.4%)[1].
Animal Protocol	Animal/Disease Models: HbSS-Townes mice (10-12 weeks old) on 129/B6 background [1] Doses: 30 mg/kg Route of Administration: Dosage daily gavage for 30 days Experimental Results: Caused fetal hemoglobin (HbF) induction, diminished hemolysis, and increased reticulocytosis.
References	[1]. A novel, highly potent and selective phosphodiesterase-9 inhibitor for the treatment of sickle cell disease. Haematologica. 2020 Mar;105(3):623-631.
Additional Infomation	Tovinontrine is an orally administered, highly selective phosphodiesterase 9 (PDE9) small molecule inhibitor. Tovinontrine is under investigation in clinical trial NCT04474314 (A Study of IMR-687 in Subjects With Sickle Cell Disease).

Solubility Data

Solubility (In Vitro)

DMSO : ~100 mg/mL (~253.50 mM)

Solubility (In Vivo)

Solubility in Formulation 1: ≥ 2.5 mg/mL (6.34 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. Solubility in Formulation 2: ≥ 2.5 mg/mL (6.34 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. Solubility in Formulation 3: ≥ 2.5 mg/mL (6.34 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 25.0 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	2.5350 mL	12.6752 mL	25.3505 mL
	5 mM	0.5070 mL	2.5350 mL	5.0701 mL
	10 mM	0.2535 mL	1.2675 mL	2.5350 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.