Designing drugs for neuroprotection Dr Gayle H Doherty School of Psychology and Neuroscience, University of St Andrews

Cost: $100-300 million 5-7 yrs 2yrs The Drug Discovery Process Target identification Target validation Lead identification Candidate optimization Pre-clinical Testing Animal trials Toxicity and pharmaco-kinetics Clinical Testing Phase I Phase II Phase III Approval Phase IV 5-7 yrs 2yrs Cost: $100-300 million

Drug repurposing – new jobs for old drugs High New chemicals: >10yrs to develop >$100 million 2% success Risk Repurposing: 2 yrs to develop $2-10 million 25% success Low Low High Return

Risk factors for Alzheimer’s disease Leptin Age Leptin levels decrease with age Family history No established link to leptin Head trauma Leptin benefits healing after head trauma, therefore… Low education No link to leptin levels Mid-life hypertension ? Depression Leptin levels reduced, especially women Smoking Leptin levels reduced Inactivity Leptin levels reduced Mid-life obesity Leptin levels reduced/ leptin insensitivity Diabetes Leptin levels reduced/ leptin insensitivity

Leptin Anti-obesity hormone Control food intake BUT Also has a lot of other functions in the brain Keeps neurons alive Helps them to signal to one another

Can leptin protect neurons? Doherty et al., Neurobiol. Aging, 2013

Can leptin prevent AD pathology? Tangles = build up of p-tau Other markers – increased expression of endophilin 1

Leptin prevents upregulation of p-tau and endophilin 1 in vitro 1 = control 2 = Ab1-42 3 = 100nM leptin 4 = Ab1-42 + 100nM leptin Doherty et al., Neurobiol. Aging, 2013

Zucker Fa/fa and fa/fa rats Not genetically manipulated Spontaneous null mutaion of ob receptor Obesity by 4 weeks of age Memory deficits by 6 months of age Biochemistry of brain unknown

What about animals that don’t respond to leptin? Doherty et al., Neurobiol. Aging, 2013

Can leptin protect neurons? Yes Very few tau tangles Lots of tau tangles

Why would leptin be a good drug? It counteracts AD pathology at multiple levels Already licensed to fight obesity in humans Well tolerated – it is a naturally occurring hormone

Why wouldn’t leptin be a good drug? Very big molecule Hard to administer Cost

What now?

Leptin (116–130) prevents copper and Aβ-induced cell death in human SH-SY5Y cells. Leptin (116–130) prevents copper and Aβ-induced cell death in human SH-SY5Y cells. (A) Pooled data revealing that leptin and leptin (116–130) prevent LDH release induced by administration of 5 μM CuCl2. (B) Similar pooled data was obtained for cultures treated with 10 μM Aβ1–42. (C) Pooled data showing that in 5 μM CuCl2 treated cultures enhanced numbers of cells are detected with a crystal violet assay when cultures are cotreated with either leptin or leptin (116–130) with a similar trend observed when cultures were induced to die with 10 μM Aβ1–42 (D). Yasaman Malekizadeh et al. Cereb. Cortex 2016;cercor.bhw272 © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

Leptin (116–130) enhances episodic-like memory. Leptin (116–130) enhances episodic-like memory. (A) Object–place–context task used to assess episodic-like memory. There are 2 sample phases in which mice are exposed to different copies of 2 different objects (star and hexagon) and allowed to explore for 3 min. In the test phase they see 2 new copies of 1 of the objects. The arrow points to the object that has not been previously seen in that place within that context. (B) Mean ± SEM discrimination index for the 3 groups. *P < 0.05. (C) Total exploration time in the test phase is not different between groups. (D) Exploration of the novel and familiar objects in the test phase. Yasaman Malekizadeh et al. Cereb. Cortex 2016;cercor.bhw272 © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

Conclusions Leptin(116–130) mirrored the cognitive enhancing effects of leptin as it enhanced performance in episodic-like memory tests. Leptin(116–130) prevented hippocampal synaptic disruption (not shown) Leptin(116–130) neuronal cell death in models of amyloid toxicity. These findings establish further the importance of the leptin system as a therapeutic target in AD.

With Thanks With Thanks University of Dundee University of St Andrews Dayne Becanno-Kelly Jenni Harvey With Thanks University of St Andrews Vanya Metodieva Lisa Strother Alison Holiday Laidlaw Undergraduate Internship Programme University of St Andrews