BI-409306 (CAS#: 1189767-28-9) targets human PDE9A (IC50 = 65 ± 11 nM), rat PDE9A (IC50 = 168 nM), human PDE1A (IC50 = 1.45 μM), human PDE1C (IC50 = 1.17 μM). No inhibitory activity (IC50 > 10 μM) against human PDE2A, 3A, 4B, 5A, 6AB, 7A, and 10A. [1]
BI-409306 targets phosphodiesterase 9A (PDE9A), an enzyme that hydrolyzes cyclic guanosine monophosphate (cGMP) in the brain. It is a potent and selective inhibitor with an IC₅₀ of 52 nM. It displays weak activity against other PDEs, such as PDE1A (IC₅₀ 1.4 μM), PDE1C (IC₅₀ 1.0 μM), and PDE2A, PDE3A, PDE4B, PDE5A, PDE6AB, PDE7A, and PDE10A (IC₅₀ > 10 μM).

Osoresnontrine is a potent and selective PDE9A inhibitor, with an IC50 of 52 nM, and shows weak activity against other PDEs, such as PDE1A (IC50, 1.4 µM), PDE1C (IC50, 1.0 µM), PDE2A, PDE3A, PDE4B, PDE5A, PDE6AB, PDE7A, and PDE10A (IC50 all > 10 μM), and has no obvious effect on 95 non-PDE targets at 10 μM. Osoresnontrine improves long-term potentiation (LTP) in rat hippocampus slices[1].

---

BI-409306 (CAS#: 1189767-28-9) is a potent and selective inhibitor of PDE9A in vitro, with mean IC50 of 65 nM for human PDE9A and 168 nM for rat PDE9A. It shows weak inhibition of PDE1A (1.45 μM) and PDE1C (1.17 μM), and no inhibition (IC50 >10 μM) of PDE2A, 3A, 4B, 5A, 6AB, 7A, and 10A. It has no significant activity against 95 non-PDE targets at 10 μM. [1]
In vitro, BI-409306 is a potent and selective PDE9A inhibitor with an IC₅₀ of 52 nM. It increases cGMP levels in rat prefrontal cortex and cerebrospinal fluid. It attenuates a reduction in mouse striatum cGMP induced by the NMDA-receptor antagonist MK-801. It promotes long-term potentiation, a cellular correlate of learning and memory.

BI-409306 (CAS#: 1189767-28-9) increases cGMP levels in rat prefrontal cortex and cerebrospinal fluid (CSF) in a dose-dependent manner after intraperitoneal or oral administration. At 7.5 mg/kg i.p., it increased extracellular cGMP by 187.9% at 20 min; at 15 mg/kg i.p., significant increases at 20, 40, and 180 min. Oral administration at 3 and 10 mg/kg significantly increased cGMP in rat CSF (p<0.001). It reverses MK-801-induced reduction in mouse striatal cGMP: 0.5 mg/kg i.p. significantly attenuated the decrease (41% increase vs MK-801 alone, p<0.01). [1]
It enhances hippocampal long-term potentiation (LTP) ex vivo in rat slices: at 1 μM (bath-applied) enhances LTP induced by weak tetanic stimulation (p=0.021); at 0.3 μM enhances LTP induced by strong tetanic stimulation (p=0.048). [1]
It improves working memory in mice: oral BI 409306 (0.007-2.5 mg/kg) reverses MK-801-induced deficit in T-maze spontaneous alternation (p<0.05). It improves episodic memory: i.p. 0.15 mg/kg (30 min before trial 1) significantly increases novel object exploration time 24 h later (p<0.001). [1]
In vivo, BI-409306 is orally bioavailable. It increases brain cGMP levels and promotes synaptic plasticity. It enhances memory function in rodents. It has been evaluated in clinical trials for the treatment of Alzheimer's disease and schizophrenia. Its effects are consistent with PDE9A inhibition and cGMP elevation.

In vitro potency and selectivity were determined using scintillation proximity assays (SPA) for PDE inhibition. Recombinant human and rat PDE isoforms were expressed in SF9 insect cells via baculovirus system. Cell extracts containing PDE were incubated with serial dilutions of BI-409306 (CAS#: 1189767-28-9) in assay buffer (50 mM Tris pH 7.4, 8.3 mM MgCl2, 1.7 mM EGTA, 0.1% BSA, 0.05% Tween-20). For PDE1A/1C, 200 nM calmodulin and 12 mM CaCl2 were added. The reaction was initiated by adding 80 nM ³H-cGMP or ³H-cAMP (1 mCi/L) and incubated 1 h at room temperature. The reaction was stopped with 50 μM inhibitor solution and 17.9 mg/ml yttrium silicate SPA beads. Conversion of substrate was measured by scintillation counting. IC50 values were calculated using GraphPad Prism. Selectivity against non-PDE targets was assessed by receptor binding assays at MDS Pharma Services. [1]
In vitro PDE9A enzyme assays for BI-409306 involve measuring the hydrolysis of cGMP by PDE9A in the presence of varying concentrations of the inhibitor. The enzyme is incubated with cGMP and the compound, and the amount of GMP produced is measured using a luminescence-based or fluorescence-based assay. IC₅₀ values are calculated from dose-response curves.

In vitro cell-based assays for BI-409306 are performed using neuronal cell lines or primary neurons. Cells are cultured in appropriate media and treated with BI-409306 at various concentrations. Intracellular cGMP levels are measured by ELISA or using fluorescent cGMP indicators. The effects on neuronal function, such as synaptic plasticity and neuronal survival, can also be assessed.

For microdialysis: Male Sprague-Dawley rats (200-250 g) were implanted with transcebral microdialysis probes in prefrontal cortex under chloral hydrate anesthesia. After 24 h recovery, probes were infused with artificial CSF at 5 μl/min. BI-409306 (CAS#: 1189767-28-9) (1.5, 7.5, 15 mg/kg) or vehicle (0.9% NaCl, 0.1 M HCl, 0.2 M NaOH, pH 4.5-4.6) was injected i.p. after three basal samples. Dialysate collected every 20 min for 240 min. cGMP measured by ¹²⁵I-radioimmunoassay. [1]
For rat CSF cGMP: Male Wistar rats (250-320 g) received oral BI-409306 (CAS#: 1189767-28-9) (0.3, 1, 3, 10 mg/kg) or vehicle (sodium chloride pH 2.8). After 30 min, CSF collected from cisterna magna, centrifuged, and cGMP measured by LC-MS/MS with [¹⁵N5]cGMP internal standard. [1]
For mouse striatal cGMP: Male CD-1 mice (25-28 g) received i.p. BI-409306 (CAS#: 1189767-28-9) (0.15 or 0.5 mg/kg) ± s.c. MK-801 (0.125 mg/kg). After 30 min, animals euthanized by focused microwave irradiation, striatal tissue collected, homogenized, and cGMP measured by ELISA. [1]
For electrophysiology: Transverse hippocampal slices (400 μm) from male Wistar rats (7-8 weeks) were maintained in interface-type perfusion chamber at 33°C. fEPSPs recorded from CA1 stratum radiatum. BI-409306 (CAS#: 1189767-28-9) (0.1, 0.3, 1 μM) or vehicle (0.01% DMSO) was bath-applied. Weak tetanic stimulation: four paired pulses (200 ms interval). Strong tetanic stimulation: ten 4-pulse bursts (200 ms intervals) repeated once after 10 min. LTP measured as fEPSP slope change. [1]
For T-maze: Male CD-1 mice (4-5 weeks) received oral BI-409306 (CAS#: 1189767-28-9) (0.007-2.5 mg/kg) or vehicle (0.5% Tylose) 60 min before test, and s.c. MK-801 (0.1 mg/kg) 30 min before. Continuous alternation task: one forced-choice then 14 free-choice trials. Percentage of correct alternations recorded. [1]
For object recognition: Male C57BL/6J mice (3-4 months) received i.p. BI-409306 (CAS#: 1189767-28-9) (0.015 or 0.15 mg/kg) or vehicle (saline) 30 min before trial 1. Trial 1: two identical objects for 10 min. Trial 2 (24 h later): one familiar and one novel object for 10 min. Exploration time recorded. [1]
In vivo animal studies for BI-409306 were conducted in rodent models of cognitive impairment, such as the Morris water maze or novel object recognition tests. The compound is administered orally. Cognitive performance is assessed, and cGMP levels in brain tissue are measured by ELISA or LC-MS to confirm target engagement.

After oral administration of BI-409306 (CAS#: 1189767-28-9) at 1.5 mg/kg in rats: mean plasma concentrations (n=3) were 892 nM at 0.5 h, 714 nM at 1 h, 683 nM at 2 h, 50 nM at 4 h. In mice (NMRI, 20-25 g) at same dose: 2097 nM at 0.5 h, 2227 nM at 1 h, 1042 nM at 2 h, 183 nM at 4 h. CSF concentration of BI 409306 was approximately 20% of plasma concentration (from separate study). [1]
BI-409306 is orally bioavailable. It increases brain cGMP levels. Specific pharmacokinetic properties, such as half-life and volume of distribution, are not extensively detailed in the available literature. It is soluble in DMSO (≥75 mg/mL). The compound is stable as a powder at -20°C for up to 3 years.

Comprehensive toxicological data for BI-409306 are not widely available in public literature. As a research compound, it is intended for laboratory use only and is not for human therapeutic use outside approved clinical trials. Standard safety precautions should be followed when handling this compound. The compound is supplied with a purity of ≥98%.

[1]. BI 409306, a novel phosphodiesterase 9A inhibitor, part I: potency, selectivity and in-vitro functional characterization on synaptic plasticity. International Congress on Schizophrenia Research.

Osoresnontrine is being investigated in the clinical trial NCT02281773 (a study designed to investigate the efficacy, safety, and tolerability of four different doses of BI 409306 compared to placebo in patients with schizophrenia receiving stable antipsychotic medication over a 12-week period).

---

BI-409306 (CAS#: 1189767-28-9) is a PDE9A inhibitor developed by Boehringer Ingelheim. It has been evaluated in phase I and phase II clinical trials for cognitive impairment in schizophrenia and Alzheimer's disease. CSF cGMP levels are a translatable biomarker of target engagement. The compound enhances both early and late-phase LTP, suggesting promotion of protein synthesis-dependent long-term memory consolidation. [1]
BI-409306 is a potent, selective, and orally bioavailable PDE9A inhibitor. It is also known as Osoresnontrine and SUB 166499. It increases cGMP levels in the brain and enhances memory function. This product is for research use only.

C16H17N5O2

311.338482618332

311.138

1189767-28-9

1189767-28-9;

135908617

White to off-white solid powder

0.2

1

5

3

23

477

0

O1CCC(CC1)N1C2=C(C(NC(CC3C=CC=CN=3)=N2)=O)C=N1

BZTIJCSHNVZMES-UHFFFAOYSA-N

InChI=1S/C16H17N5O2/c22-16-13-10-18-21(12-4-7-23-8-5-12)15(13)19-14(20-16)9-11-3-1-2-6-17-11/h1-3,6,10,12H,4-5,7-9H2,(H,19,20,22)

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 (8.03 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.

---

Solubility in Formulation 2: ≥ 2.5 mg/mL (8.03 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 saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

---

View More

Solubility in Formulation 3: 2.5 mg/mL (8.03 mM) 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.)