Understanding Alzheimer’s disease

The “Design of small molecule therapeutics for the treatment of Alzheimer’s Disease based on the discovery of Innovative drug Targets” (ADIT) is one of three large collaborative research projects in Alzheimer’s disease funded by the European Union's Framework Programme 6. NGP spoke with Georg Terstappen, ADIT coordinator and Vice President of Discovery Research at Siena Biotech, to find out more about the project’s progress.

With a focus on diseases of the central nervous system, Siena Biotech was set up in 2002 with the aim of discovering new drugs for therapeutic intervention. Georg Terstappen, VP of Discovery Research at Siena Biotech, is responsible for the company’s research units Bioinformatics, Protein Sciences, Screening Sciences, Cancer Biology and Neurobiology. The second research division, Therapeutic Research, is headed by Graeme Robertson and made up of four units: two Medicinal Chemistry units, Drug Profiling and Drug Design.

At five years, the Italian company, headed by its CEO Giovanni Gaviraghi, is relatively young. Its most advanced project at present is in the phase of late preclinical development. “This is a project in collaboration with Wyeth Pharmaceuticals in the US, where we identified selective agonists for a subtype of nicotinic acetylcholine receptors. The research has come along very nicely, which was greatly facilitated by the excellent collaboration between both companies,” says Terstappen.

International collaboration

When Siena Biotech was started, the idea was to focus on neurodegenerative and neuroproliferative disorders, in particular Alzheimer’s disease, Huntington’s disease and Glioblastoma. Terstappen recalls: “At the time, we wanted to understand more of the pathophysiology of the diseases in order to be able to select the best targets for therapeutic intervention. Coming back to Alzheimer’s disease, it was clear to us that to achieve this, we would need to collaborate with other institutions. That is when we decided to apply for a grant from the European Commission for an integrated project engaging different partners with different expertise in order to reach a common goal.”

The idea for ADIT was born, and Terstappen and his team developed a strategy to define what the project should look like. “We identified potential partners, we contacted them, and luckily at the end of the day all the partners that we wanted to have on board accepted to participate to this project. We submitted the project proposal in November 2003. It was basically approved in May of the following year and its official starting date was 1 June, 2005.”

Eight different partners form the truly international ADIT partnership. There is the Center for Biological Sequence Analysis (CBS) in Lyngby, Denmark; the EMBL in Heidelberg, Germany; the VU Medisch Centrum in Amsterdam, the Netherlands; the Department of Pharmacology of the University of Florence, Italy; the Turku PET Center in Finland; and the University of Bath, UK.

There is also Alta, a company specialised in developing and managing scientific research projects. “They help us with the administration of the project, which is significant. There’s quite a tough reporting system as a part of the project, and every year you have to prepare the new implementation plan for the following period. The commission is working on making leaner documentation available, but at present it’s still quite a bureaucratic burden,” states Terstappen.

The funding ADIT receives from the EU amounts to almost €7.5 million for five years. For Siena Biotech, this means that 50 percent of the project cost has to come out of its own pockets. “But since we are completely committed to fighting Alzheimer’s disease as a company, and since we started activities in this area before the project was even approved, that’s not a problem for us,” assures Terstappen.

Main objectives

The goal of the ADIT project is twofold. Firstly, it aims to improve the understanding of the pathophysiology of Alzheimer’s disease. Secondly, it will use this understanding to identify targets whose modulation should result in efficacious medicines – something which is easier said than done. “The aim of the project as communicated to the commission was, and still is, to identify one to two drug candidates for development in the five-year-frame of the project. It’s an ambitious goal, but we are completely committed to reaching it.”

ADIT has now concluded its second year. The progress that has been made, Terstappen says, is really significant. “The project focuses on the amyloid-beta (Aβ) hypothesis of Alzheimer’s disease, namely that Aβ in one form or another is causally related to the disease. We have used comprehensive transcriptomics, phosphoproteomics and differential proteomics approaches to find out what happens early on in neurons if you expose them to Aβ. Including all the data that we have generated, we developed patho-pathways of the disease by employing bioinformatics in-house and with the support of the EMBL in Heidelberg and the CBS in Denmark. By the end of this year, we will have finalised the creation of these disease mechanism pathways, which help us to understand the pathophysiology better and to select potential targets for therapeutic intervention,” reports Terstappen.

To date, ADIT has identified 92 differentially expressed proteins as potential targets through the differential proteomics approach. From the transcriptomic approach, 94 differentially expressed genes could be identified. The phosphoproteomics approach yielded 123 differentially expressed proteins.

Challenges

“One of the biggest challenges if you work in diseases with significant unmet medical needs is to deal with the fact that the pathophysiology of the disease usually is very poorly understood,” says Terstappen, adding: “Quite some exploratory, more basic research is necessary to unravel disease mechanisms, which is important to select targets that have a good chance of success when being modulated to lead to efficacious medications later on. This is a real challenge because you have to be pragmatic in drug discovery. There’s budgets and timelines to stick to. On the other hand, there is so much that you could potentially do in order to validate the targets further that might work for ten years. Getting the balance right is a challenge, and we have defined a series of rigorous target validation criteria before we progress them towards lead discovery. Very important is access to postmortem AD brain tissue and relevant disease animal models which we have ensured by integrating partners specialised in these areas.”

The tractability of a target is one aspect in ADIT’s target validation catalogue. And there are potential byproducts. “If we find a disease-relevant target but it is not tractable and we can’t develop a screening assay for it, it might still be good as a biomarker. We keep a close eye on this since biomarkers will be very helpful for drug development,” concludes Terstappen.

In lead discovery, there are other challenges associated with Alzheimer’s disease. The molecules that the ADIT project is trying to identify need to have appropriate physicochemical properties, and they need to be able to penetrate into the brain. “You can model this in silico, but only to a certain extend, and you will still have to test quite a significant number of molecules for the ability to enter the brain. At the end of the day, it’s all prediction. The big challenges have to do with the very properties of the chemical molecules.”

Leaving the phase of disease understanding for target discovery purposes, ADIT is now moving on to the phase of lead discovery. Out of all potential targets, two are currently in the latter phase. “One is a protein inhibitor of the Wnt signaling pathway for which we identified interesting small organic molecule inhibitors. We are currently progressing these ‘hits’ towards lead molecules. For our second target, a G protein-coupled receptor (GPCR), which we identified and validated more recently, we have developed assay systems, and screening will start later this year.”

While driving the project forward, the ADIT team also developed methods for effective target validation in cortical neurons and for subcellular fractionation of proteins extracted from these neurons. “This technology development was necessary and has greatly aided overall progress of the project. We are currently submitting manuscripts for publication because we want to make these methods available to others as well,” adds Terstappen.

This is an emerging trend within the industry, which puts an emphasis on collaboration and information sharing. Terstappen believes that it is going to be a key aspect for the pharmaceutical industry in the future. “Joining forces with others is going to be crucial. In the pharmaceutical industry there is a trend of big pharma concentrating on development and marketing of compounds. This opens opportunities for smaller companies focusing on research. In fact, already today a significant portion of big pharma’s portfolio does not come from in-house research. ”

Siena Biotech’s collaboration with Wyeth in the field of neurodegenerative diseases is one of several. The company also works together with Roche. But how does the Italian company remain competitive? Terstappen: “As a small-medium enterprise, it is clearly important for us to concentrate on our core business, which is drug discovery. You have to understand where you have to invest in technologies in-house just as well as you have to understand which technologies to access through collaborations and contract research organisations (CROs). Getting this balance right is part of remaining competitive. Other important aspects are excellence in science and operation, which are crucial for success. Clearly, this is all driven by people and hence recruitment of the best and continuous development of staff is another guarantor of success. ”

Looking ahead

With ADIT, Terstappen is confident that Siena Biotech will find its place at the forefront of science. He is hoping to finalise target discovery activities by the end of this year to be able to focus more resources on lead discovery and supporting activities, such as the configuration of transgenic animals. One such system is in development and for ADIT’s GPCR activities have already been initiated.

“We are convinced that better understanding of pathophysiological mechanisms of diseases will be key for successful drug discovery and our investment as a company in this kind of research is really significant. Most of the compounds that currently fail in phase III clinical studies fail because of a lack of efficacy. This means the companies have invested a lot of money in compounds which are not leading to efficacious treatments because the initial target wasn’t really relevant for the disease.”

Would Terstappen like to see potential drugs failing faster? “If you want to put it like that. But I do not very much like to see the words ‘drugs’ and ‘failing’ in such close vicinity. I would rather say that I want to understand the pathophysiology of the disease better in order to be in a position to develop more efficacious drugs” he concludes.

BIO

A biologist by training, Georg C. Terstappen, Vice President of Discovery Research at Siena Biotech, started working in pharmaceutical research and drug discovery in 1992 at Bayer’s Pharma Research Centre in Germany. After five years at Bayer, Terstappen joined Glaxo Wellcome at its Medicines Research Centre in Italy. After the merger with SmithKline Beecham, he worked for GlaxoSmithKline as Director of Systems Research. In May 2002, he moved on to start Siena Biotech together with the company’s CEO. Since 2004 he is also adjunct Professor at the University of Siena.

1. Differential proteomics approach based on detergent fractionation/2D DIGE/MS:
92 differentially expressed proteins identified

2. Targets from proteomics studies:
123 differentially modulated potential phosphoproteins

• for 9 proteins validation in vitro has been concluded
• for some of these proteins validation experiments ex vivo and in vivo have been conducted and concluded

3. Targets from transcriptomics studies:
94 differentially expressed genes

• for 4 genes validation in vitro has been concluded
• the most interesting gene is a tractable GPCR which is induced by Aβ
• its overexpression is neurotoxic in neurons
• ex vivo/in vivo studies as well as assay development are in progress