Pharmaceutical ProjectSHP4001

University of HuddersfieldIdentifying drugs that target beta- and alpha- secretase:

Implications for the treatment of Alzheimer's

disease

Student: Nathan Cartwright

Student Number: U1254124

Project Supervisor: Dr Patrick McHugh

This Presentation was used as part of the pharmaceutical project, in which I was tasked with providing an oral presentation to a group of lecturers and peers which would have no knowledge of the area. This presentation is a toned down summary of some of the points which were covered in the project module.

Introduction: Goals of the project Use the Ingenuity Pathway Analysis(IPA) program to

discover known drugs which have the potential to therapeutically treat Alzheimer’s disease.

With the use of the IPA program discover and explore the pathways in which these drugs can effect the alpha- and beta- secretases.

Use the Ingenuity Knowledge Database to find out how and why the IPA program had highlighted these drugs as drugs which have an effect on Alzheimer’s disease.

Assess the potential of each drug in the therapeutic treatment of Alzheimer’s disease by researching the ways in which it interacts with the secretases by using current literature.

Background of Alzheimer’s Disease. Initially recognised by Dr Alois Alzheimer upon examining the

brain of a female patient who passed away due to pre-senile dementia.

Unusual tissue and abnormal clumps were found in the brain where tangled fibres were bundled together. The clumps are now recognised as Neurofibrillary tangles, and the tissues are recognised as amyloid plaques.

Amyloid plaques are believed to block cell-to-cell signalling at synapses and are also linked to inflammation of the brain due to causing an immune response.

Accumulation of these plaques is believed to cause the formation of neurofibrillary tangles, which consist of tau protein.

The main constituent of amyloid plaques is the 4kDa amyloid β peptide (Aβ) which is believed to be the main cause of Alzheimer’s disease.

Aβ is formed when beta-secretase processes APP(amyloid precursor protein) hence the emphasis on drugs which can effect beta-secretase or alpha-secretase as part of the goal of the project.

By having a drug which could inhibit beta-secretase or promote processing of APP by alpha-secretase, there will be less processing of APP into Aβ leading the a reduction in the levels of it being produced leading to a neuroprotective effect being generated as there will be slower accumulation of amyloid plaques.

Figure 1 Proteolytic process of APP by α-, β- and γ-secretases

Method IPA is a piece of software which can visually demonstrate

pharmacological and physiological pathways of drugs and other compound.

The information which the pathways generate relationships from is gathered from currently relevant literature which can be found in the Ingenuity Knowledge Database.

IPA has various tools which were used in the project such as the grow tool, which allows for relationships between molecules to be explored downstream or upstream of selected molecules.

The use of IPA allows the user to identify drug molecules which do not have a direct relationship to the pathway but can effect a process upstream which causes an effect to the pathway.

IPA has a large number of limitations such as: a lack of information available in the Ingenuity Knowledge Database leading to a lack of evidence to support a mechanism or interaction within a pathway and a lack of ability to specify or exclude certain molecules in a search.

This example of the application of IPA represents the results of using IPA and how the pathways are laid out by the program.

The molecules which are highlighted in pink are the molecules which the overlay tool has specified have a link to or a role in Alzheimer’s disease.

Results

Eighteen drugs were identified by the IPA program which had enough literature available to suggest they had mechanisms which act upon Alzheimer's disease.

Eight drugs which targeted or effected the BACE1 (beta-secretase) pathway were discovered by the program.

Five drugs which targeted or effected the ADAM10 (alpha-secretase) pathway were discovered by the program.

Five drugs which target or effect both the ADAM10 and BACE1 pathways were discovered by the program.

Only seven of the eighteen drugs which were identified were selected for further discussion within the dissertation, the reasons why only seven were chosen are because, the chosen seven had a much more significant amount of literature available or they had greater implication for treating Alzheimer's disease as opposed to the ones which were not selected.

In the following slides we will discuss three drugs, one targeting ADAM10, BACE1 and one which targets both.

Discussion for MK-8931 (BACE1)

MK-8931 is a novel anti-Alzheimer’s drug which is currently in phase 2/3 clinical trials.

MK-8931 is an inhibitor for BACE1 however it cannot be used to treat pre-existing Alzheimer’s disease as it cannot remove the already produced Aβ plaques but has the potential to be used as a preventative measure for those who have a high risk of Alzheimer’s disease such as those with a familial history of it.

MK-8931 was found to give a 50% reduction in Aβ production when administered at 12mg and when administered at 40mg, a 75% reduction in Aβ production was perceived. These numbers were found in a recent study by investigating dose-response profiles (Forman et al, 2013).

Discussion for Lovastatin (ADAM10 and BACE1)

Lovastatin is a statin, it is belived to increase the activity of ADAM10 but interfere with BACE1 by reducing the number of lipid rafts.

Lovastatin reduces the amount of cholesterol available, cholesterol is found in lipid rafts in which BACE1 is active.

With a reduction in the amount of lipid rafts, BACE1 activity will reduce meaning the production of Aβ will be severely limited (Kojro et al, 2001).

This then promotes the activity of ADAM10 as there is less competition to cleave APP, leading to the neuroprotective APPsα being formed in greater quantities.

Discussion for Acitretin Acitretin is a retinoid, when Acitretin was tested on Alzheimer’s disease

a two- to three- fold increase in the difference between ADAM10 and BACE1 activity was observed.

This led to a reduction in the production of Aβ as BACE1 activity was severely hindered by Acitretin, reducing the speed of neurodegeneration in Alzheimer’s disease patients (Tippman et al, 2009).

Unlike a large amount of the drugs which were identified by the IPA program, Acitretin has the potential to pass across the blood brain barrier which means it has the ability to interact with its desired targets.

While Acitretin is a prospective drug in the therapeutic treatment of Alzheimer’s disease it has a varying degree of side effects which are synonymous with hypervitaminosis A, but they are scarcely permanent and are not severe enough to interrupt continued treatment.

Summary

Of all the drugs which the IPA program identified, there were few which could potentially be ruled out as drugs which will not be able to have a positive effect in the treatment of Alzheimer’s disease.

The lack of evidence which was found for nearly all of the drugs does hinder the progress in which research is being undergone to test their suitably in the treatment of Alzheimer’s disease.

Further research needs to be done in order to draw conclusions and parallels to the proposed mechanisms in which various literature articles have suggested.

The best hope for the treatment of Alzheimer’s disease is indeed more research and may lie within a combination therapy of some of the drugs which were suggested by the IPA program.

Sources

Figure 1 - Rossner S., Sastre M., Bourne K. and Lichtenthaler S. F. (2006), Transcriptional and translational regulation of BACE1 expression–implications for Alzheimer’s disease. Prog. Neurobiol. 79, 95–111.

Lichtenthaler, S. F. (2011) Alpha-secretase in Alzheimer's disease: molecular identity, regulation and therapeutic potential. J. Neurochem. 116, 10–21. doi:10.1111/j.1471-4159.2010.07081.x

Moonhee, L., McGeer, E., McGeer, P. L., (2014), activated human microglia stimulate neuroblastoma cells to upregulate production of beta amyloid protein and tau: implications for Alzheimer's disease pathogenesis. Neurobiology of Aging, 36(1), 42-52.

Foreman, M., Kleijn, H., Dockendorf, M., Palcaza, J., Tseng, J., Canales, C., Egan, M., Kennedy, M., Laterza, O., Ma, L., Tanen, M., Apter, J., Backonja, M., Ereshefky, L., Gevorkyan, H., Jhee, S., Rynders, R., Zari, A., Bryan, E., Wagner, J., Troyer, M., Stone, J. 2013. The novel BACE inhibitor MK-8931 dramatically lowers CSF beta-amyloid in patients with mild-to-moderate Alzheimer’s disease. Alzheimer’s and dementia. 9(4). P139. Doi: 10.1016/j.jalz.2013.04.083

Kojro, E., Gimpl, G., Lammich, S., März, W., & Fahrenholz, F. (2001). Low cholesterol stimulates the nonamyloidogenic pathway by its effect on the α-secretase ADAM 10. Proceedings of the National Academy of Sciences of the United States of America, 98(10), 5815–5820. doi:10.1073/pnas.081612998

Tippman, F., Hundt, J., Schneider, A., Endres, K., Fahrenholz, F. 2009. Up-regulation of the α-secretase ADAM10 by retinoic acid receptors and acitretin. FASEB J. 23(6) – 1643-54. Doi: 10.1096/fj.08-121392.