Aim Dysfunction of nitric oxide (NO) – soluble guanylate cyclase (sGC) – cyclic guanosine monophosphate (cGMP) signalling is implicated in the pathophysiology of cognitive impairment and dementia. Zagociguat is a central nervous system-(CNS-) penetrant sGC stimulator designed to amplify NO-cGMP signalling in the CNS. This article reports on a phase 1b study evaluating the safety and pharmacodynamic effects of zagociguat. Methods In this randomized crossover study, 24 healthy participants ≥65 years of age were planned to receive 15 mg zagociguat or placebo once daily for two 15-day periods separated by a 27-day washout. Adverse events, vital signs, electrocardiograms, and laboratory tests to assess safety. Pharmacokinetics of zagociguat were evaluated in blood and CSF. Pharmacodynamic assessments included evaluation of cerebral blood flow, CNS tests, pharmaco-electroencephalography, passive leg movement, and biomarkers in blood, cerebrospinal fluid, and brain. Results Twenty-four participants were enrolled and 12 participants completed both treatment periods, while 12 participants completed only one treatment period. Zagociguat was well tolerated and penetrated the blood-brain barrier. Zagociguat induced modest decreases in blood pressure. No consistent effects of zagociguat on other pharmacodynamic parameters were detected. Conclusion Zagociguat was well tolerated and induced modest systemic blood pressure reductions consistent with other sGC stimulators. No clear pharmacodynamic effects of zagociguat were detected, perhaps due to optimal CNS function in healthy participants. Studies in participants with proven reduced cerebral blood flow or CNS function may be an avenue for further evaluation of the compound.

Cholinesterase inhibitors have been shown to improve cognitive functioning in patients with Alzheimer’s Disease (AD), but are associated with side effects and only 20-40% of the patients clinically improve. In this study, we aimed to investigate the acute pharmacodynamic (PD) effects of a single dose of galantamine on CNS functioning in mild to moderate AD patients and its potential to predict long-term treatment response. This study consisted of a challenge phase, in which a single dose of 16 mg galantamine was administered to 50 mild to moderate AD patients in a double-blind, placebo-controlled cross-over fashion. Acute PD effects were monitored with use of a CNS test battery. In the subsequent treatment phase of the study, patients were treated with open-label galantamine according to regular care. After 6 months of galantamine treatment, patients were categorized as either responder or as non-responder based on their MMSE, NPI and DAD scores. An analysis of covariance was performed to study the difference in acute PD effects between responders and non-responders. Acute decreases of absolute frontal alpha (-20.4; 95%CI=-31.6,-7.47; p=.0046), beta (-15.7; 95% CI=-28.3,-0.93; p=.0390) and theta (-25.9; 95%CI=-38.4,-10.9; p=.0024) EEG parameters and of relative frontal theta power (-3.27%; 95%CI=-5.96,-0.58; p=.0187) on EEG after a single dose administration of galantamine significantly distinguished long-term treatment responders (n=11) from non-responders (n=32) after 6 months. This study demonstrates that patients who demonstrate a reduction in EEG power in the alpha and theta frequency after a single administration of galantamine 16 mg will most likely respond to treatment.