Proof-of-Mechanism Study of the Phosphodiesterase 10 Inhibitor RG7203 in Patients With Schizophrenia and Negative Symptoms.

Background: Reduced activation of dopamine D receptor signaling may be implicated in reward functioning as a potential driver of negative symptoms in schizophrenia. Phosphodiesterase 10A (PDE10A), an enzyme that is highly expressed in the striatum, modulates both dopamine D- and D-dependent signaling.

Methods: We assessed whether augmentation of D signaling by the PDE10 inhibitor RG7203 enhances imaging and behavioral markers of reward functions in patients with schizophrenia and negative symptoms.

Phase 1 randomized study on the safety, tolerability, and pharmacodynamic cognitive and electrophysiological effects of a dopamine D receptor positive allosteric modulator in patients with schizophrenia.

ASP4345, a novel dopamine D receptor positive allosteric modulator, is being evaluated for the treatment of cognitive impairment associated with schizophrenia (CIAS). This phase 1 multiple ascending-dose study (NCT02720263) assessed the safety, tolerability, and pharmacodynamics of ASP4345 in patients with schizophrenia/schizoaffective disorder. Pharmacodynamic assessments were Cogstate cognitive tests and electrophysiological biomarkers, including gamma-band power and phase synchronization in response to 40-Hz auditory steady-state stimulation, as well as mismatch negativity (MMN) and P3a event-related potentials.

Pharmacokinetics of ASP4345 from Single Ascending-Dose and Multiple Ascending-Dose Phase I Studies.

Background: Cognitive impairment is a core feature of schizophrenia. While first- and second-generation antipsychotic drugs treat psychotic exacerbations, no treatment is approved for the cognitive dysfunction. We have identified ASP4345, a positive allosteric modulator of the dopamine type 1 (D) receptor that selectively binds to, and enhances the activity of, D receptors.

A Proof-of-Concept Study Evaluating the Phosphodiesterase 10A Inhibitor PF-02545920 in the Adjunctive Treatment of Suboptimally Controlled Symptoms of Schizophrenia.

Background: Effective treatments for managing suboptimal clinical responses to current therapy for schizophrenia remain a critical unmet need. Phosphodiesterase 10A (PDE10A) inhibition represents a mechanistically novel approach to the treatment of schizophrenia, with preclinical studies suggesting improvements in partially responsive symptoms could be achieved via adjunctive use of the PDE10A inhibitor PF-02545920. Therefore, the adjunctive safety, tolerability, pharmacokinetics, and efficacy of multiple repeat doses of PF-02545920 were investigated in a phase 1b study and subsequent phase 2 study.

Implementing a Memory Clinic Model to Facilitate Recruitment into Early Phase Clinical Trials for Mild Cognitive Impairment and Alzheimer's Disease.

Background: The recruitment challenges for MCI and AD subjects into clinical trials are well known, and this is particularly true for early phase studies. Currently, only 10-20% of all patients who are referred for research from the community are trial eligible (Grill and Karlawish, 2011). Due to the limited and specific study objectives in early phase study designs, these rates drop to approximately one patient every two months.