Last week, the California Institute for Regenerative Medicine awarded $45 million over two years to 72 projects focused on human embryonic stem cell research. One of those grants, a $714,654 award to the Human Biomolecular Research Institute, supports a project that aims to treat heart disease by using drug-like molecules that act as cardiomyocyte differentiation agents.
The project, a collaboration between HBRI, the Burnham Institute, the University of California, San Francisco, and others, is using high-throughput cell-based screening to study the effects of small molecules on cardiomyocyte differentiation.
While human embryonic stem cells have been shown to form cardiomyocytes, leading to the hope that one day these cells could replace damaged heart tissue, “efficient and controlled cardiomyogenesis in ESC cultures has not been achieved due to the unavailability of differentiation agents and an incomplete understanding of the pathways that regulate cardiac development,” the HBRI grant abstract states.
This week, CBA News caught up with John Cashman, director and founder of HBRI and principal investigator on the CIRM grant, to discuss the goals of the project.
It seems like yours was one of the few grants awarded under this initiative that uses stem cells for screening rather than as therapeutics.
Well, we’re going to be developing therapeutics using the high-throughput screening procedure. We already have hits, and now we’re going to do what we call hit-to-lead refinement.
Our specialty is to make drug-like materials, so we hope to improve the potency and selectivity and incorporate drug-like properties into these new materials so that they can be tested in more relevant models that are going to be closer to giving us something that’s more drug-like.
And the molecules that you did identify would lead to stem cell differentiation in vivo?
Right. What’s been done is that in collaboration with the Burnham Institute — Mark Mercola and Jeff Price — is to take some commercial libraries and screen the compounds and identify compounds that are causing cardiomyocyte differentiation and promoting survival and maturation and replication of the differentiated cardiomyocytes.
And really the reason we can do that is we have some sensitive probes that are incorporated into these cells that give nice indication for differentiation, and again, that’s the brainchild of people like Mark Mercola and his collaborators, including people like Bruce Conklin at UCSF and others.
I don’t want to give the impression that we’re alone here. This is a highly integrated and very rich collaboration of a number of experts, and we hope we can really make some nice progress here and rapidly get into the world of drug discovery quickly.
What are some of the challenges in indicating differentiation in these assays and what was unique about the probes you used to do that?
They’re specifically engineered cell lines, so that is really key. Some of that technology was developed in collaboration with people like Juan Carlos Belmonte at the Salk and Bruce Conklin at UCSF and Mark Mercola.
Another really important feature of the work is the automated microscopy expertise that Jeff Price brings to bear on the project. He’s developed some unique imaging microscopy, and you need that to look at cell-based assays in a high-throughput fashion, and some novel algorithms to quantify the differentiation for the reporter molecules.
What does the hit-to-lead process entail?
Drug discovery really is an experiential exercise. In other words, it draws upon all your experiences from the past as a chemist looking at the hits, and every chemist should have some natural inclination, if they’re trained broadly in chemistry and metabolism, toxicology, and drug development like we are, to look at the molecule and recognize certain regions that could stand further development or certain regions that are not drug-like so they should be replaced or replenished.
So you draw upon all your experience to come up with new compounds that are more drug-like and that should lead you to more potent and less toxic and more selective materials.
Does the definition of ‘drug-like’ change at all when the goal is to bring about differentiation rather than inhibition?
A lot of the same principles apply. There are still lots of drugs out there that, whether we know it or not, are doing lots of cellular modulation. So the same sorts of principles apply: You want to have something that’s potent enough, but not necessarily so potent that you paralyze a certain system, for example. And you want to have a compound that is non-toxic and bio-available and gets to the site of action and has selectivity and potency and doesn’t interfere with other vital processes.
So it’s really a smorgasbord of activities to get to that point.
What is your timeline for this project?
As a basic scientist, I have to be really careful here. The state of California has decided that this is something notable and laudable and should go forward, and there are expectations for many people that this will lead to tremendous revolutions in the way we do stem cell-related research in drug discovery and therapeutics. I believe that, but I can’t overpromise. I can’t say in 16 to 25 months we’ll be treating patients. So we have to be a little bit careful.
But having said that, we fully anticipate [moving] forward in the drug-discovery arena, and we’re not opposed to partnering with other entities that have a lot more resources and a lot of expertise. That’s probably the expectation of the people of California — to fund the basic research and get it to the point where it’s partnered with the large pharmaceutical and biotech companies that have the resources and expertise to do the more advanced clinical work to ultimately bring new chemical entities to drug candidate status.
What were the advantages of using a cell-based screen in this project?
First of all, we don’t know what the targets are, so in a way, using an integrated system to tell you what the response is is very powerful, and there are many advantages to that. Do the molecules get into the cell? Well, yes, they do because we know we have a response. Is the response due to one particular perturbation? Probably not; it’s probably multiple sites and multiple contributions. Is it complex? Yes, it’s highly complex, but that’s the strength of the high-throughput cell-based system.
In contrast to some more traditional drug discovery preliminary screens where it’s a receptor or an enzyme or some sort of protein that is quite specific and quite selective, this is giving us an enormous amount of information that may take years and years to deconvolute. And in a way, it’s not that important. It’s important heuristically, but at the end of the day, does the cell differentiate, or does it not? If it does, then you’ve got something. If it doesn’t, then you’ve got to move on.
So it’s very powerful, but it’s also very complex. It’s not easy to do these types of high-throughput cellular screens. But when you have the expertise of Mark and Jeff and their colleagues, it makes it a tractable problem.
So the idea is to use a much more information-rich and highly rewarding system where the payoff is great, but the degree of difficulty to get useful data is high. So if you can crack that nut, you can really make some fantastic progress, and that’s, again, why the collaboration with the Burnham Institute is so critical.
Will the Burnham researchers be playing a role in the hit-to-lead phase of the project?
It’s going to be tightly integrated. There will be an iterative interplay between our institute and the Burnham Institute.
The award is to the institute, and we bit off a large amount of work for the amount of money we requested. This is truly a seed or preliminary type of budget, but there is tremendous value-added information that we’re going to be developing in these compounds that will be immediately looked at in these cell-based assays at the Burnham Institute. And then we’ll immediately have rich information about where to go and what to do next.
So it’s an iterative process. That’s why I can’t tell you that we’ll have a drug in two years.