Design And Development Of Experimental Therapeutics ((Systemic & Neurodegenerative Disorders and Alzheimer's Disease)

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1. Alzheimers Disease: Three series of agents are being developed to treat AD. Selective inhibitors of amyloid-beta peptide (Abeta) production (Posiphen) and inhibitors of the enzymes acetylcholinesterase (AChE) (Phenserine - also has anti-apoptotic actions) and butrylcholinesterase (BChE) (Bisnorcymserine). 1.1. Molecular events associated with AD: A reduction in levels of the potentially toxic Abeta peptide has emerged as a key therapeutic goal in AD. Targets to achieve this goal are factors that affect the expression and processing of the Abeta precursor protein (APP). Our studies generated novel compounds to lower APP and Abeta levels in neuronal cultures and the brain of animal models without toxicity. This activity is independent of cholinergic action, but is post-transcriptional: lowering APP protein levels without affecting mRNA levels via translational regulation. This is mediated, in part, via the 5-untranslated region (UTR) of APP mRNA. We are characterizing mechanisms involved and focusing on these in the design and synthesis of new agents that lower APP levels as a way of lower Abeta (collaborators: Drs. Lahiri, Sambamurti). Posiphen (aka., Buntanetap) is in clinical trials (CTs) and a new backup compound has been generated. Posiphen was well tolerated in phase 1/2 CTs, showing target engagement and effectively lowering APP, Abeta, tau and other key AD CSF markers (collaborator: Dr. Maccecchini). Parallel studies (collaborator: Drs. Lahiri, Sambamurti, Rogers, Maccecchini) show that Posiphen has a broader action to reduce a wide number of misfolded proteins, including alpha-synuclein. Posiphen and metabolites are being assessed in cellular and animal models of Parkinson's disease (PD), Down's syndrome and other neurological disorders. 1.2. Cholinesterase inhibitors: Compounds were developed to optimally augment the cholinergic system in the elderly and raise levels of the neurotransmitter, acetylcholine (ACh). Chemistry, X-ray crystallography, biochemistry and pharmacology studies resulted in the design and synthesis of novel compounds to differentially inhibit either AChE or BChE in the brain or periphery for potential treatment of a variety of disorders (AD, TBI, myasthenia gravis, and as chemical warfare prophylactics (collaborators: Drs. Becker, Hoffer, Marini, Lahiri, Kamal, Reale, Sambamurti). Specific and highly selective BChE inhibitors have been developed to define this enzyme's role in brain during health, aging and disease. 1.2A. AChE: Long-acting, centrally active, selective AChE inhibitors were developed to define its role in health and disease and move compounds into CTs. Extensive chemistry on the template of eserine was undertaken. Novel phenylcarbamates were developed that are highly selective for AChE vs. BChE, have favorable toxicologic profiles, robustly enhance cognition in animal models and are neurotrophic/protective and anti-inflammatory. Phenserine was translated into CTs in AD (collaborators: Drs. Becker, Nordberg, Friedhoff, Winblad, Sambamurti, Lahiri, Bruinsma). A new AD CT is starting with a new extended controlled-release oral formulation (Collaborators, Drs. Schneider, Ballard, Becker, Flanagan, Kapogiannis) to reduce neuronal cell death, and involves exosome technology paired with classical markers of disease course. Recent studies show Phenserine is highly effective in protecting against brain injury (stroke and TBI) providing potent anti-apoptotic/anti-inflammatory actions across cellular and in vivo models, and new analogs have been synthesized and are under evaluation. 1.1B. BChE: In healthy brain, 80% of cholinesterase activity is in the form of AChE and 20% is BChE. AChE activity is concentrated chiefly in neurons, and BChE primarily with glial cells. Kinetic evidence indicates a role for BChE, in hydrolysing excess ACh. In advanced AD, AChE activity declines to 15% normal levels in affected brain regions, whereas BChE activity rises 2-fold. The normal BChE/AChE ratio becomes mismatched in AD causing excess metabolism of already depleted ACh. The first reversible, centrally-active BChE inhibitors were synthesized and appear favorable in AD preclinical models. Bisnorcymserine was advanced into phase 1 CTs where its safety, pharmacokinetics and -dynamics were assessed (collaborators: Drs. Kapogiannis, Maccecchini, Lahiri, Kamal) 1.3. With the compounds above, the relationship between the cholinergic system and inflammation is being characterized in health and disease (collaborators: Drs. Reale, Kamal). Our recent studies suggest that the cholinergic anti-inflammatory pathway is compromised in AD, but can potentially be effectively "reset" by phenserine and alike agents. 2. Stroke, AD, PD, brain trauma, Down's syndrome: Drugs currently used provide temporary relief of symptoms, but do not prevent the occurrence of cell death. Our target for drug design is the transcription factor, p53 and down-stream effectors. p53 up-regulation is a common feature of many neurodegenerative disorders and a gatekeeper to the biochemical cascade that leads to apoptosis. We developed novel tetrahydrobenzothiazole/oxazole analogs to inhibit p53 activity. Agents are in current assessment for neuroprotective/regenerative actions in cellular and animal models (collaborators: Drs. Pick, Hoffer, Wang, Luo) to define whether neurons can be rescued from apoptotic cell death. Our p53 inactivators demonstrate potent activity in models of stroke, AD, PD, and TBI as pharmacologic probes of cell death mechanisms. In parallel, we demonstrated the efficacy of phenserine at clinically relevant doses in animal models of TBI and stroke yo mitigate programmed neuronal cell death. Its antiapoptotic/anti-inflammatory actions reduce neuronal cell death and mitigate behavioral impairments across animal models at well tolerated doses. 3. Clinical translation and assessment of experimental drugs in neuropsychiatric conditions: Despite promising advances in understanding possible mechanisms of disease in recent years, clinical investigators still struggle with methods and practices too open to effects from measurement errors, biases, carelessness at research sites distant from the sponsor, and with commercial pressures to as quickly as possible enter human trials - a priority acknowledged to allow frequently insufficient preclinical investigations and suspected as one cause for failures in human CTs. Hence, drug discovery/development is at great risk of failing due to lack of efficacy or compromises to safety. Less than 11% of all new agents entering clinical development reach the marketplace. For neurological drugs, attrition is higher: less than 7% are successful. To understand/optimize clinical development the numerous factors that impair the process and generate type 2 errors are being critically reviewed/assessed (Collaborator: Dr. Becker). Rational approaches to optimize the clinical drug development process of neuropsychiatric drugs are being developed to aid reduce the currently too high attrition rate in neurological drug development; particularly in AD. We are evaluating best procedures to advance drugs into the CT stage, and are evaluating biomarkers available from exosomes - obtained from plasma samples that are enriched for neuronal and/or astrocytic cells (Collaborators: Drs. Kapogiannis, Goetzl, Schneider, Ballard, Becker, Tovar-Y-Romo) - to potentially follow drug-target engagement in brain and alterations in disease course. 4. Biomarkers of disease progression, drug engagement and response are being evaluated in blood-borne derived exosomes (with Drs. Kapogiannis, Schneider, Ballard, Goetzl, Tovar-Y-Romo) in animal models and CTs.