PF-04447943 (Edelinontrine) is a potent and selective phosphodiesterase 9A inhibitor with an IC50 of 12 nM, which is 78-fold more selective than that used for other PDE family members (IC50>1000 nM).PF-04447943 exhibits anti-inflammatory activity, attenuates inflammatory responses by inhibiting oxidative stress, inflammation, and modulating T-cell polarization, and may be useful for research on sickle cell anemia.

PF-04447943 inhibits ANP (0.3 μM) stimulated cGMP (IC50: 375±36.9 nM (n=16)), in HEK whole cells expressing rhesus PDE9A2. PF-04447943 is found to be highly selective over other PDE enzymes (PDE1, Ki=8600±2121 nM, n = 5; PDE2A3, Ki>99,000 nM; PDE3A, Ki>50,000 nM; PDE4A, Ki>29,000 nM; PDE5A, Ki=14,980±5025 nM, n=5; PDE6C, Ki=5324±2612 nM, n=4; PDE7A2, Ki>75,000 nM; PDE8A, Ki>50,000 nM; PDE10, Ki>51,250±20,056 nM, n=4; PDE11, Ki>80,000 nM) and no other significant activity at ~60 other receptors/enzymes. Using recombinant human, rhesus, and rat PDE9A2 in a cell-free assay PF-04447943 is shown to have a Ki of 2.8±0.26, 4.5±0.13, and 18.1±1.9 nM (n=4, 11 and 9 respectively).[2]

PF-04447943 concentrations dose-dependently increase in blood, brain, and cerebrospinal fluid (CSF), thirty minutes following oral administration in rats (1-30 mg/kg). In mice, PF-04447943 (3, 10, 30 mg/kg p.o.) dose-dependently enhances plasma and brain concentrations of PF-04447943 while the brain-to-plasma ratio ranged from 0.26 to 0.7 although this is not entirely dosed-dependent. Based on i.v. and p.o. dosing, pharmacokinetic studies with PF-04447943 in the rat indicate a Tmax of 0.3 h, T1/2 of 4.9 h, Cl of 21.7 mL/min/kg, and oral bioavailability of 47%. The brain: plasma exposure ratios 30 min after dosing range from 0.13 at the 1 mg/kg dose to 0.33 at the 30 mg/kg dose. CSF levels are approximately 50% of brain levels. CSF cGMP levels increase in a dose-dependent manner from a basal level of 3 pmol/mL to 13.3 pmol/mL (3.5-fold) at the 30 mg/kg dose. CSF cGMP levels also increased in a dose-dependent manner from a basal level of 3 pmol/mL in vehicle-treated animals to 13.3 pmol/mL (3.5-fold) at the 30 mg/kg dose. CSF cGMP levels are elevated at all doses tested with a maximal effect of 3.5 fold increase above controls at 30 mg/kg.[2]