The spectacular Ice Bucket Challenge, which swelled the coffers of the ALS Association by more than $100 million during the month of August, also fixed a spotlight on the debilitating neurodegenerative disease amyotrophic lateral sclerosis (ALS), commonly known as Lou Gehrig's disease. The fundraiser went viral when 29-year-old Pete Frates, diagnosed with ALS in 2012, and his family shared information about the effort on social media.

The Ice Bucket attention cheered scientists and drug developers active in ALS, but challenges that have bedeviled the indication remain.

"When we think about how to treat the disease, we have multiple targets," observed Lucie Bruijn, the association's chief scientist. "That already is one challenge. How do you then prioritize those targets in terms of medicines for human disease vs. the model system?"

To date, only a single drug, Rilutek (riluzole, Sanofi SA), is designed to treat ALS, by blocking glutamatergic neurotransmission in the central nervous system and preventing apoptosis of the motor neuron. However, the beneficial effects of the drug are modest, typically prolonging life of an individual with ALS by only a few months.

Otherwise, ALS has been a graveyard for potential therapies. Recent years have seen big disappointments from promising candidates, including lead compound olesoxime from Trophos AS; dexpramipexole, an asset developed by Biogen Idec Inc. in partnership with Knopp Biosciences LLC; and tirasemtiv (formerly CK-2017357), a fast skeletal muscle troponin activator from Cytokinetics Inc. (See BioWorld Today, Dec. 14, 2011, Jan. 4, 2013, and April 28, 2014.)

A phase I study of ISIS-333611 from Isis Pharmaceuticals Inc. in patients with familial ALS also failed to show significant differences compared to placebo, and the company did not move forward with development, according to Cortellis Clinical Trials Intelligence (CTI).

All told, more than 200 trials have been conducted in ALS, according to Cortellis CTI, with 100 of them completed. Only 15 moved into phase III, and many of those studies focused on the use of existing drugs, such as sodium valproate or minocycline, or even vitamins to treat ALS.

Although tirasemtiv is soldiering on, Biogen's dexpramipexole blow-up "put a huge dent" in the ALS space, said Rich Casey, president and CEO of Neuraltus Pharmaceuticals Inc., a Palo Alto, Calif.-based biotech that is studying its single asset, NP001, in ALS. Neuraltus had the bad timing to market itself to pharma prospects just as the phase III data from dexpramipexole hit the fan.

"One of the two big issues I face in trying to raise money for the company is that it's ALS, where nothing's even come close to working," Casey told BioWorld Insight.

The other challenge is trying to advance a single asset in a world that largely disdains the binary nature of biotech investments. But those obstacles haven't stopped Neuraltus from moving NP001 forward. The company is pursuing the hypothesis that neuroinflammation is at least partly responsible for progression of the disease. That line of research proposes that individuals with ALS have increased levels of inflammatory macrophages, resulting in the release of factors in the central nervous system that lead to motor neuron damage. NP001 acts by returning the activated macrophages back to their normal states.

"It's a hugely different approach," Casey said. "We're not trying to go and fix the problem at the motor neuron. We're trying to tamp down an unregulated immune response."

In a single-dose phase I study in ALS patients, NP001 caused a dose-dependent regulation of blood macrophage activation. In a randomized, double-blind, placebo-controlled phase IIa study that enrolled 136 patients, the drug demonstrated a clinically relevant slowing of ALS progression, producing a strong signal in a subset of patients treated at the highest dose over a six-month period, with good safety and tolerability.

"We thought we could just slow down the disease," Casey said. "We didn't think we could stop if for a while, but that's actually what happened in 25 to 33 percent of the patients."

With the FDA's blessing, the company plans to design its next study to examine the percentage of patients whose revised ALS functional rating scale (ALSFRS-R) scores remain constant or increase over dosing rather than studying ALSFRS-R slope decline as the primary endpoint, according to Casey. If the company can replicate phase IIa results in a phase IIb or III study, the agency has said it will consider the data confirmatory and weigh approval, he said.

"We're not going to cure the disease," Casey admitted. "But our drug indirectly affects the disease by tamping down on this immune activation and giving the cells a chance to rest. That's our view of what's happening."

IMPACT ON GENETIC FORMS MAY COME 'RELATIVELY SOON'

Merit Cudkowicz, chief of neurology and director of the MDA ALS Clinic at Massachusetts General Hospital in Boston, said other lessons have been learned from earlier drug development failures in the space.

"There's a ton of work going on right now, based on the sheer number of scientists and companies in the ALS space," she said. Understanding of the genetics underpinning the familial type of ALS – estimated to cause approximately 10 percent of cases – has progressed rapidly, as researchers discovered that some of those genes cross over with dementia.

That research spilled over into therapeutic development, with the most common genetic approaches seeking to silence superoxide dismutase (SOD) or C9orf72, either using antisense oligonucleotides or viral vectors with RNAi.

"There's a general sense that we might be able to make an impact on the genetic forms of the disease relatively soon," Cudkowicz told BioWorld Insight.

For example, fueled by a $45 million series A, Third Rock Ventures-backed Voyager Therapeutics Inc. is using an adeno-associated virus (AAV) approach in central nervous system disorders, including ALS. The Cambridge, Mass.-based firm has a preclinical program investigating the form of the disease that results from the SOD1 genetic mutation. Although that form represents only 2 percent to 3 percent of ALS patients, the literature suggests that SOD1 may be an important pathological feature of idiopathic ALS, with applicable learnings to the broader field. (See BioWorld Today, Feb. 12, 2014.)

Neuralgene, of Bogota, Colombia, also is developing an AAV-based gene therapy designed not only to target gene delivery to the brain and spinal cord but also to genetically engineer stem cells. The company is conducting animal studies of lead compound PRCN-829, which was developed from concepts learned from stem cell treatments while amplifying and lengthening the effect. PRCN-829 is designed to deliver multiple genes, including Factor H, to neural stem cells.

Anelixis Therapeutics LLC, of Cambridge, Mass., has a research partnership with Neurimmune Holding AG, of Zurich, Switzerland, to advance potential ALS treatments. Anelixis, a translational medicine and drug development company formed last year by the ALS Therapy Development Institute, is using the virtual biotech business model to advance potential ALS treatments licensed from the Institute and similar organizations. The company has a preclinical program examining the role of the CD40 ligand in ALS and a second program in SOD1.

Just last week, Treeway BV, of Rotterdam, the Netherlands, inked an agreement with the Leiden Academic Center for Drug Research to collaborate in optimizing clinical trial designs and data analysis for ALS, with the goal of developing a population disease progression model that may be used for a phase III study with Treeway's lead candidate, TW001, a reformulation of an undisclosed neuroprotective drug designed to halt progression of the disease. Follow-on compounds will address the underlying causes of the disease. Treeway's founders, serial entrepreneurs Bernard Muller and Robbert Jan Stuit, both are living with ALS.

And Coyote Pharmaceuticals Inc., of Menlo Park, Calif., is targeting ALS and Alzheimer's disease with lead therapeutic CNS-102, which has shown potent neuroprotective effects in animal models. Coyote's drug delivery system, based on geranylgeranylacetone, or GGA, is designed to activate the gene expression of heat-shock proteins and restore the natural physiological balance within cells, enabling them to regain homeostasis and potentially stopping or reversing symptoms of degenerative disease. The company held a pre-investigational new drug application meeting with the FDA but has not yet moved CNS-102 into humans, according to Cortellis CTI.

Other companies are exploring the use of cell therapy in ALS. Earlier this year, Neuralstem Inc. raised $19.65 million to advance lead compound NSI-566 into a phase II study, now under way. A phase III could begin in 2015, and the company also plans to make the cell therapy available in Colorado after the state became the first to enact right to try legislation, designed to give seriously ill patients access to non-approved therapies. (See BioWorld Today, Jan. 6, 2014, and May 23, 2014.)

In June, Brainstorm Cell Therapeutics Inc., of Petach Tikvah, Israel, launched a randomized, double-blind, placebo-controlled phase II trial in the U.S. to evaluate the safety and efficacy of transplanting its autologous mesenchymal stem cells, which secrete neurotrophic factors, also known as MSC-NTF or Nurown, in ALS patients. That study followed a dose-escalating phase IIa trial in Israel. The Nurown approach uses a patient's own bone marrow-derived stem cells, eliminating the risk of rejection or treatment with immunosuppressive agents.

Kadimastem Ltd., of Ness Ziona, Israel, also is exploring cell therapy for ALS. The firm recently reported positive preclinical data showing increased life expectancy in mice treated with the company's cells as well as a significant improvement in motor function, compared to untreated mice.

IN ALS, 'NEURONS DON'T DIE ALONE'

The revelation that ALS is an extraordinarily heterogeneous disease may require a drug development approach more similar to the evolution that's occurred in cancer therapeutics.

"The genetic trials are the beginning of that effort, by looking just at C9 or just at SOD1 in patients," said Cudkowicz, a member of Coyote's scientific advisory board. "We're now starting to get a handle on that in sporadic patients. What we've learned from past trials is that we can't do studies with 900 patients when we don't know the underlying biology."

In up to 90 percent of patients with ALS, the root cause is still unknown. But prospects have never been brighter for understanding the science driving the disease, according to Cudkowicz. Although industry collaboration in ALS remains dismally small, academic collaborations and data sharing have blossomed.

Stanley Appel, chairman of neurology at Houston Methodist Hospital and director of the Houston Methodist Neurological Institute and the hospital's MDA/ALS Clinic, agreed that the landscape of ALS research has changed dramatically over 20 years, from the identification of the SOD mutation in the 1990s leading to studies of the role of misfolded proteins to the "exponential increase" in identifying genetic mutations – some 30 genes now directly implicated – that cause ALS.

But, it turns out that genetic mutations alone "are not quite the answer," suggested Appel, whose work also supports the role of neuroinflammation in the disease. For example, putting the SOD mutation into a transgenic mouse causes the mouse to develop a motor neuron disease that resembles ALS, but targeting the motor neuron by putting the mutation only into that cell fails to prompt disease development.

"That tells us that the neurons don't die alone," Appel explained. "The neurons express something that is picked up by other cells surrounding glia. When the mutation is in all these cells you get the disease, but if you get [the mutation] in any single cell, you don't get the disease to the same extent."

That discovery prompted Appel to look at ALS as the result of both intra-neuronal damage caused by mutations as well as neuroinflammation as "the silent executioner" of the motor neuron.

"It's taken 20 years of exciting genetic work, which is still ongoing, together with the pathway of elucidating neuroinflammation, to get to this point where we can think about it as a two-stage phenomenon," Appel told BioWorld Insight.

Preclinical studies emerging from work by Appel and colleagues have shown these neuroinflammatory responses can be modified using bone marrow stem cell transplantation, resulting in the doubling of lifespans in affected mice. Efforts to study the approach in early clinical studies are under way – in part, with ALS Association funding from the Ice Bucket Challenge.

"If you know the mutation and you can, early on, shut off the gene that's making the abnormal protein, then you will prevent the disease from propagating," Appel said. But ALS is a "dying back" phenomenon, and "the problem is that we're not sure if we're too late to stop the progression of the neuroinflammation in man," he added. "We want therapies that can shut down the cause, and we want therapies that will stop the spread and amplification and will repair the motor neurons."

'WE NEED TO PARTNER AT MANY LEVELS'

In August, an international team led by scientists from the Florida campuses of the Scripps Research Institute (TSRI) and the Mayo Clinic published findings in Neuron from another first-time therapeutic strategy targeting the C9orf72 mutation, which also causes a type of frontotemporal dementia. Matthew Disney, professor of chemistry at TSRI and professor of neuroscience at the Mayo Clinic, and colleagues showed that their approach, using a small-molecule drug candidate, could inhibit toxic protein translation by as much as 50 percent.

"We're trying to improve the compounds in a medicinal chemistry program to see if we can get them to patients, and how quickly we can do that," Disney said. "Our challenge is to get them into the brain – to see how blood-brain penetrant the molecules are – but also to get our hands on preclinical animal models to show how well the compounds work there. We are 100 percent invested in getting these compounds to patients by the quickest route and whatever means necessary," whether through a start-up or partnering, he added.

Disney's efforts have so far not received Ice Bucket funding, although he recognizes the need for scientific review before disbursing grants. Still, there's frustration.

"We haven't received any additional money since we published the paper," he said. "In some sense, these compounds are ready to move forward. We have a lot of strategies, and if we had the resources we could really push them forward. It's just getting the resources. They've been slow to come."

Earlier this month, the ALS Association disclosed an initial commitment of $21.7 million from the Ice Bucket Challenge, matched by $12.5 million from private sources. The funding will advance four major cooperative programs – ALS Accelerated Therapeutics, or ALS-ACT, the New York Genome Center, the Neuro Collaborative and Project Mine – and provide grants for a number of smaller research efforts.

The association faces a challenge – though it's a nice one to have – in allocating Ice Bucket funds where they can do the most good and having funds for follow-on studies. Although Bruijn called the ALS mouse model "very robust" and valuable in understanding the features of human disease, "the reality is that a mouse is not a human," she pointed out. "Although there are controversial views on this, I don't think there have been many ALS therapy approaches that have been used in the mouse that have had a significant effect in humans. The most significant effects have been around two to three weeks of life extension in the mouse model, and what that means when you try to take it into the clinic might not be so meaningful."

Too, $100 million doesn't go that far in drug development, experts agreed. Foundations, matching gifts and, ultimately, venture firms and pharmas will need to get into ALS in a bigger way to move promising compounds through the so-called "valley of death" and beyond.

"The drug development process is a complicated and lengthy one, and is quite a rigorous one," Bruijn told BioWorld Insight. "It has to identify whether the target makes sense. Is it druggable? Is it going to move forward? We have to push the envelope and help with better translation between the animal model and humans, maybe alongside induced pluripotent stem cell models. We also need to look at biomarkers that are present in humans that might relate to a study that's set up in vitro."

Those hurdles notwithstanding, Bruijn is optimistic about the trajectory in ALS research.

"I'm very excited that there's much more attention all around," she said. "There are many ways to do this, but the most important is to drive ideas in the lab all the way to the clinic, and for that I think we need to partner at many levels."