Biogen Idec Inc. and Evotec AG are taking opposite strategies to finding new therapies for amyotrophic lateral sclerosis, a disease with an unknown mechanism. Whereas Biogen Idec is forming partnerships with multiple academic labs to solve the biology of the disease, Evotec is partnering with the Harvard Stem Cell Institute at Harvard University to employ phenotypic screens that circumvent the need to understand the mechanism from the outset.

Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease in which progressive loss of motor neurons leads to muscle weakness, atrophy and respiratory failure. Despite recent advances in understanding the genetics of the disease,1 the biological trigger of the nerve cell loss remains unclear and therapeutic targets remain elusive.

About 10% of patients with ALS show familial inheritance, whereas the remaining 90% of cases are sporadic and have no clear genetic linkage. Both forms of the disease are phenotypically similar, suggesting that pathways identified by genetic mutations might also be disrupted in sporadic ALS.

Going phenotypic

In September, Evotec partnered with the Harvard Stem Cell Institute (HSCI) to combine the academic lab's expertise in creating induced pluripotent stem (iPS) cells from patients with ALS and the biotech's proprietary screening assays for the disease.

The deal is with Lee Rubin and Kevin Eggan, both faculty members at HSCI who have developed a technique for creating motor neurons from human fibroblasts. The duo also has generated cell lines from patients with ALS representing a variety of genetic backgrounds.

Evotec CSO Cord Dohrmann would not elaborate on the details of the endpoints of the company's ALS assays but told SciBX that the goal of the screens is to identify compounds with therapeutic potential that also can be used to explore the mechanisms underlying the degeneration of motor neurons.

The assays were developed via Evotec's in-house research on motor neurons derived from mouse embryonic stem cells.

Evotec also will use its expertise in scale-up to translate the iPS cell differentiation process to industry and enable screening of tens of thousands to hundreds of thousands of molecules. Until now, the HSCI researchers did not have a way to increase the supply of their cell lines in quantities sufficient for drug discovery.

"Scaling up the iPS cell-based motor neurons for large-scale screens is a labor-intensive and compound-intensive process," said Dohrmann.

In addition, Evotec has high-content screening capabilities, which involve multiple simultaneous readouts from a single assay, and a Cellular Target Profiling platform obtained in the 2011 acquisition of Kinaxo Biotechnologies GmbH.

The platform integrates information from the diverse sets of assay readouts, incorporates quantitative analysis of data points such as protein binding and Kd values and then yields a few specific targets that can be investigated.

Evotec hopes the functional readouts from screens of thousands of molecules against cell lines from multiple genetic backgrounds will distill down to a manageable number of targets that can be pursued both for their therapeutic potential and to gain insights into the mechanisms underlying ALS.

According to Dohrmann, the strength of Evotec's phenotypic screening strategy is the ability to follow multiple readouts at the same time. The collaboration with HSCI will allow the company to get readouts from multiple genetic libraries, which could improve the odds of detecting new targets.

"Finding associated genes is key to understanding the mechanism, and we are interested in novel mechanisms that have not yet been identified," Dohrmann told SciBX.

Backing basic science

Instead of reverse engineering the biology of ALS, Biogen Idec is working from the ground up and is investing in basic science to identify pathways, mechanisms and molecules involved in axonal degeneration of motor neurons.

In January, Biogen Idec discontinued development of dexpramipexole to treat ALS after the compound missed the primary endpoint of improving function and survival in the Phase III EMPOWER trial. The compound was licensed from Knopp Biosciences LLC after showing a dose-dependent reduction in disease progression in Phase II trials.

Dexpramipexole also showed neuroprotective effects in a murine model of ALS based on a mutant form of superoxide dismutase 1 (SOD1), a gene associated with about 20% of familial cases. However, the precise mechanism of action of dexpramipexole was never fully elucidated.

Now, Biogen Idec is working with a consortium of six academic laboratories to dissect the pathways involved in motor neuron degeneration in organisms from fruit flies to humans.

The labs at Columbia University, Harvard Medical School, Harvard University, The Rockefeller University and the Yale School of Medicine are exploring molecular pathways of disease progression for motor neurons and are examining the role of specific genes and proteins in the degenerative process.

In addition to the multipronged approach to the biology of ALS, Biogen Idec is partnering with the HudsonAlpha Institute for Biotechnology and Duke University to sequence the genomes of more than 1,700 patients with sporadic ALS.

One of the Harvard labs involved in the consortium was previously headed by Spyros Artavanis-Tsakonas, who joined Biogen Idec as CSO this year and is leading the company's discovery effort in ALS.

According to Artavanis-Tsakonas, although SOD1 represents an important target in ALS, the company wants to cast a broader net and identify additional mechanisms that give rise to sporadic ALS.

At Harvard, Artavanis-Tsakonas collaborated with the labs of consortium members Steven Gygi and J. Wade Harper2 to produce a Drosophila protein interaction map, dubbed an interactome, that contains hundreds of protein complexes involved in signaling pathways.3

Artavanis-Tsakonas plans to use the interactome as a tool to expand the research findings and identify additional potential targets. "If I find a gene that is relevant to the pathway in the ALS phenotype, then I want to use the interactome to find all the proteins it interacts with, as they could be good targets too," he said.

Translational challenges

The lessons of the recent ALS clinical trial by Biogen Idec and the fact that it has been over 17 years since the approval of Sanofi's Rilutek riluzole, the sole drug indicated for ALS, point to the difficulties in making advances in the disease even when promising candidates do emerge from discovery programs.

Both Dohrmann and Artavanis-Tsakonas acknowledge the challenge of moving to the next stage if they are successful in identifying active compounds because there are no accepted animal models of the disease that provide good predictive value for clinical studies.

Dohrmann believes that the best approach for any compound identified via iPS cell studies will be to reproduce its genetic target in mice and to test compounds for improvements in the phenotype associated with that target.

Such a mouse model may not mimic all the features of ALS in humans, but it would provide a mechanism-centric model with measurable readouts and would give an indication of the potency and efficacy of a compound that could help guide clinical trial design.

Most important, according to Dohrmann, is to create a model that enables longitudinal studies involving imaging techniques that would provide a means to evaluate compounds over an extended period
of time.

"We need new ways to evaluate molecules in vivo to make it less cumbersome, to be able to evaluate more than 20 molecules and not just under 10 and to follow the progression of the disease over time," he told SciBX.

Evotec is looking externally for animal models that could support its ALS program.

Artavanis-Tsakonas told SciBX that the path to the clinic for Biogen Idec will depend on the identified target and whether the best therapeutic would be a small molecule, antibody or antisense RNA because the different types of molecules require different experimental strategies.

In September, Biogen Idec signed a neurology-focused deal with Isis Pharmaceuticals Inc. that gives Biogen Idec access to Isis' antisense technology. Although the deal is not centered on ALS, Biogen Idec expects that antisense represents an extra tool in the search for new ALS candidates, Artavanis-Tsakonas told SciBX.

Fishburn, C.S. SciBX 6(38); doi:10.1038/scibx.2013.1050
Published online Oct. 3, 2013


1.   Chen, S. et al. Mol. Neurodegen. 8, 28 (2013)

2.   Fulmer, T. SciBX 5(29); doi:10.1038/scibx.2012.747

3.   Guruharsha, K.G. et al. Cell 147, 690-703 (2011)


Biogen Idec Inc. (NASDAQ:BIIB), Weston, Mass.

Columbia University, New York, N.Y.

Duke University, Durham, N.C.

Evotec AG (Xetra:EVT), Hamburg, Germany

Harvard Medical School, Boston, Mass.

Harvard Stem Cell Institute, Cambridge, Mass.

Harvard University, Cambridge, Mass.

HudsonAlpha Institute for Biotechnology, Huntsville, Ala.

Isis Pharmaceuticals Inc. (NASDAQ:ISIS), Carlsbad, Calif.

Knopp Biosciences LLC, Pittsburgh, Pa.

The Rockefeller University, New York, N.Y.

Sanofi (Euronext:SAN; NYSE:SNY), Paris, France

Yale School of Medicine, New Haven, Conn.