The Novel Phosphodiesterase 9A Inhibitor BI 409306 Increases Cyclic Guanosine Monophosphate Levels in the Brain, Promotes Synaptic Plasticity, and Enhances Memory Function in Rodents

N-methyl-d-aspartate (NMDA) receptor–dependent long-term potentiation (LTP) is an established cellular model underlying learning and memory, and involves intracellular signaling mediated by the second messenger cyclic guanosine monophosphate (cGMP). As phosphodiesterase (PDE)9A selectively hydrolyses cGMP in areas of the brain related to cognition, PDE9A inhibitors may improve cognitive function by enhancing NMDA receptor-dependent LTP. This study aimed to pharmacologically characterize BI 409306, a novel PDE9A inhibitor, using in vitro assays and in vivo determination of cGMP levels in the brain. Further, the effects of BI 409306 on synaptic plasticity evaluated by LTP in ex vivo hippocampal slices and on cognitive performance in rodents were also investigated. In vitro assays demonstrated that BI 409306 is a potent and selective inhibitor of human and rat PDE9A with mean concentrations at half-maximal inhibition (IC50) of 65 and 168 nM. BI 409306 increased cGMP levels in rat prefrontal cortex and cerebrospinal fluid and attenuated a reduction in mouse striatum cGMP induced by the NMDA-receptor antagonist MK-801. In ex vivo rat brain slices, BI 409306 enhanced LTP induced by both weak and strong tetanic stimulation. Treatment of mice with BI 409306 reversed MK-801-induced working memory deficits in a T-maze spontaneous-alternation task and improved long-term memory in an object recognition task. These findings suggest that BI 409306 is a potent and selective inhibitor of PDE9A. BI 409306 shows target engagement by increasing cGMP levels in brain, facilitates synaptic plasticity as demonstrated by enhancement of hippocampal LTP, and improves episodic and working memory function in rodents. SIGNIFICANCE STATEMENT This preclinical study demonstrates that BI 409306 is a potent and selective PDE9A inhibitor in rodents. Treatment with BI 409306 increased brain cGMP levels, promoted long-term potentiation, and improved episodic and working memory performance in rodents. These findings support a role for PDE9A in synaptic plasticity and cognition. The potential benefits of BI 409306 are currently being investigated in clinical trials.

[1]  B. Dubois,et al.  Evaluation of the efficacy, safety and tolerability of orally administered BI 409306, a novel phosphodiesterase type 9 inhibitor, in two randomised controlled phase II studies in patients with prodromal and mild Alzheimer’s disease , 2019, Alzheimer's Research & Therapy.

[2]  W. Gan,et al.  The Phosphodiesterase 9 Inhibitor PF‐04449613 Promotes Dendritic Spine Formation and Performance Improvement after Motor Learning , 2018, Developmental neurobiology.

[3]  M. Sand,et al.  The safety, tolerability and pharmacokinetics of BI 409306, a novel and potent PDE9 inhibitor: Overview of three Phase I randomised trials in healthy volunteers , 2018, European Neuropsychopharmacology.

[4]  E. Fedele,et al.  cAMP, cGMP and Amyloid β: Three Ideal Partners for Memory Formation , 2018, Trends in Neurosciences.

[5]  A. Blokland,et al.  Phosphodiesterase inhibition and modulation of corticostriatal and hippocampal circuits: Clinical overview and translational considerations , 2018, Neuroscience & Biobehavioral Reviews.

[6]  M. Sand,et al.  A Phase IC Study Evaluating the Safety, Tolerability, Pharmacokinetics, and Cognitive Outcomes of BI 409306 in Patients with Mild-to-Moderate Schizophrenia , 2017, Neurology and Therapy.

[7]  R. Keefe,et al.  Evaluation of the Efficacy, Safety, and Tolerability of BI 409306, a Novel Phosphodiesterase 9 Inhibitor, in Cognitive Impairment in Schizophrenia: A Randomized, Double-Blind, Placebo-Controlled, Phase II Trial , 2017, Schizophrenia bulletin.

[8]  M. Sand,et al.  A phase I, randomized, proof‐of‐clinical‐mechanism study assessing the pharmacokinetics and pharmacodynamics of the oral PDE9A inhibitor BI 409306 in healthy male volunteers , 2017, Human psychopharmacology.

[9]  Huyuan Yang,et al.  What Is Already Known about This Subject What This Study Adds , 2022 .

[10]  G. Collingridge,et al.  Long-term potentiation and the role of N-methyl-d-aspartate receptors , 2015, Brain Research.

[11]  C. Mathis,et al.  PDE9A inhibition rescues amyloid beta-induced deficits in synaptic plasticity and cognition , 2014, Neurobiology of Aging.

[12]  R. Morris.  NMDA receptors and memory encoding , 2013, Neuropharmacology.

[13]  Anne W. Schmidt,et al.  Phosphodiesterase 9A Regulates Central cGMP and Modulates Responses to Cholinergic and Monoaminergic Perturbation In Vivo , 2012, Journal of Pharmacology and Experimental Therapeutics.

[14]  H. Rosenbrock,et al.  Inhibition of acetylcholinesterase and phosphodiesterase-9A has differential effects on hippocampal early and late LTP , 2012, Neuropharmacology.

[15]  H. Lane,et al.  Glutamate signaling in the pathophysiology and therapy of schizophrenia , 2012, Pharmacology Biochemistry and Behavior.

[16]  Lynn A. Hyde,et al.  The selective phosphodiesterase 9 (PDE9) inhibitor PF-04447943 (6-[(3S,4S)-4-methyl-1-(pyrimidin-2-ylmethyl)pyrrolidin-3-yl]-1-(tetrahydro-2H-pyran-4-yl)-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidin-4-one) enhances synaptic plasticity and cognitive function in rodents , 2011, Neuropharmacology.

[17]  J. Lange,et al.  SLV330, a cannabinoid CB1 receptor antagonist, ameliorates deficits in the T-maze, object recognition and Social Recognition Tasks in rodents , 2010, Neurobiology of Learning and Memory.

[18]  U. Eysel,et al.  More than a Retrograde Messenger: Nitric Oxide Needs Two cGMP Pathways to Induce Hippocampal Long-Term Potentiation , 2009, The Journal of Neuroscience.

[19]  K. Reymann,et al.  The Na+/H+ exchanger modulates long-term potentiation in rat hippocampal slices , 2009, Naunyn-Schmiedeberg's Archives of Pharmacology.

[20]  Alcino J. Silva,et al.  The molecular and cellular biology of enhanced cognition , 2009, Nature Reviews Neuroscience.

[21]  E. Fedele,et al.  In vivo effects of phosphodiesterase inhibition on basal cyclic guanosine monophosphate levels in the prefrontal cortex, hippocampus and cerebellum of freely moving rats , 2008, Journal of neuroscience research.

[22]  K. Reymann,et al.  The novel selective PDE9 inhibitor BAY 73-6691 improves learning and memory in rodents , 2008, Neuropharmacology.

[23]  A. Blokland,et al.  Selective phosphodiesterase inhibitors: a promising target for cognition enhancement , 2008, Psychopharmacology.

[24]  R. D. Williams,et al.  Preclinical Characterization of Selective Phosphodiesterase 10A Inhibitors: A New Therapeutic Approach to the Treatment of Schizophrenia , 2008, Journal of Pharmacology and Experimental Therapeutics.

[25]  E. Fedele,et al.  Effects of phosphodiesterase inhibition on cortical spreading depression and associated changes in extracellular cyclic GMP. , 2004, Biochemical pharmacology.

[26]  P. Rosenberg,et al.  Expression of cGMP-Specific Phosphodiesterase 9A mRNA in the Rat Brain , 2001, The Journal of Neuroscience.

[27]  E. Kandel,et al.  Nitric Oxide Signaling Contributes to Late-Phase LTP and CREB Phosphorylation in the Hippocampus , 1999, The Journal of Neuroscience.

[28]  James F. Smith,et al.  Isolation and Characterization of PDE9A, a Novel Human cGMP-specific Phosphodiesterase* , 1998, The Journal of Biological Chemistry.

[29]  J. Dodart,et al.  Scopolamine‐induced deficits in a two‐trial object recognition task in mice , 1997, Neuroreport.

[30]  E. Kandel,et al.  Activity-dependent long-term enhancement of transmitter release by presynaptic 3′,5′-cyclic GMP in cultured hippocampal neurons , 1995, Nature.

[31]  H. Rosenbrock,et al.  Role of PDE9 in Cognition. , 2017, Advances in neurobiology.

[32]  G. Paxinos,et al.  The Rat Brain in Stereotaxic Coordinates , 1983 .