Soluble Guanylate Cyclase Modulators and Inhibitors for Neurological Disorders

Guanylate cyclase (GC) is divided into two categories: membrane bound particulate guanylate cyclase (pGC) and cytoplasmic soluble guanylate cyclase (sGC). sGC (NO-GC, Nitric oxide activated guanylate cyclase) is a receptor for signaling molecule nitric oxide. NO activates sGC to convert guanosine triphosphate (GTP) to cyclic guanosine monophosphate (cGMP). cGMP activates cGMP dependent protein kinases (PKG) which phosphorylates transcription factor cyclic AMP response element binding protein (CREB) in the nucleus. Phospho-CREB (pCREB) has a role in synaptic plasticity and cognition enhancement. Aim of our study was to develop neuroprotective sGC modulators (GCMs) acting through NO/sGC/cGMP/CREB signaling pathway. Development of neuroprotective disease modifying agents is the holy grail of neurodegenerative disorders like Alzheimer’s disease (AD) and Parkinson’s disease (PD). Currently, there is no cure for AD and PD. Available treatment options only provide symptomatic relief. Promising agents failed in the late stage of clinical trials. NO-GC (Nitric oxide activated guanylate cyclase) related therapeutics target a wide range of physiologic dysfunctions. However, no one has developed GCMs for CNS applications. Drugs targeted at NO/sGC/cGMP/CREB pathway can target synaptic dysfunction and rescue learning and memory. The preliminary goal of this work was to design a variety of novel A-350619 (Abbott, A-35) and YC-1 analogs targeted as sGC stimulators, with the ability to elicit increased levels of pCREB in SH-SY5Y human neuroblastoma cell culture. Using A-35 and YC-1 as lead compounds, molecules were designed based upon classical bioisosteric replacement, ease of synthesis, desirable physiochemical properties, and chemical diversity. In general, molecules were designed to have beneficial CNS drugability properties (i.e. ClogP ~ 2.5-5.0; TPSA = 25-75; MW < 400). cGMP measurement in the bovine lung sGC containing buffer spotlighted NO-GC activation by novel GCMs. A candidate GCM with sGC and pCREB activity was modified into a photo affinity probe (PAP), containing alkyl and aryl azide. Upon UV- irradiation, GCM-PAP covalently binds to sGC. In parallel, neuroprotective in vitro assay was performed in SH-SY5Y cells. GCMs from both series were able to reverse toxicity induced by oxidative neurotoxin 6-hydroxy dopamine (6-OHDA). Finally, brain and plasma bioavailability was confirmed for a candidate GCM, VL-1-102, with sGC and pCREB activity. Scopolamine treated mice are a good model for learning in step through passive avoidance (STPA) task. Scopolamine treated mice can learn the task, but cannot consolidate memory. VL-1-102 was able to reverse memory deficit in scopolamine treated mice. To summarize, novel GCMs were synthesized, and an active lead from the 1st generation of compounds, VL-1-102, was studied in in vitro and in vivo assays. Brain penetrating and metabolically more stable, second generation of YC-1 series, 2, 4-difluoro benzyl derivatives, was synthesized, and bovine lung sGC activation was determined. 2,4-difluoro benzyl derivative, RG-2-65, is an active lead candidate for the future studies. Chapter 2 and 3 focus on migraine animal model and a potential migraine therapy, respectively. Migraine is a disabling headache disorder, and the number one reason for the absenteeism from work. Chronic migraine treatment does not work in the 50 % of patients. There is a need to find a treatment for chronic migraine. Reliable mice models drive successful drug discovery. Therefore, chronic migraine mice model was developed using a novel sGC stimulator, VL-1-102. VL-1-102 was able to induce acute and chronic hyperalgesia in mice. VL-1-102 effect was reversed by proven migraine treatment, topiramate and sumatriptan. After confirming the role of sGC in migraine pathophysiology, we explored sGC inhibitors as a potential migraine treatment. sGC inhibitor, RG-2-12, was able to reverse VL-1-102 and NTG induced acute and chronic migraine symptoms in mice. Our data suggest that sGC inhibitors can be considered as novel migraine treatment.