Indi Molecular said this week that it has raised $300,000 from a new investor, Asset Management Ventures, bringing the total amount raised in its seed round to $1.8 million.
The company plans with this funding to continue development of its protein catalyzed capture reagents, a synthetic affinity agent technology that it hopes to position as an alternative to traditional antibodies.
Indi Molecular also noted a series of recent papers detailing PCCs' use for the detection of anthrax, diagnosis of HIV, and targeting of challenging protein epitopes – offering insights into its plans for applying and marketing the reagents going forward.
The PCC reagents use click chemistry combined with pairs of random peptide libraries – one containing acetylene functionalities and the other containing azide groups – to create affinity reagents to given proteins. Target proteins are screened against these libraries to find peptides that bind them, and when these peptides bind, the protein epitope acts as a catalytic point for the acetylene- and azide-containing peptides, which then link together via click chemistry, forming multi-peptide, protein-binding constructs that can then be pulled down and identified. According to Indi Molecular, PCCs have several potential advantages over monoclonal antibodies including better specificity and the ability to target regions of proteins inaccessible to monoclonals.
A spinoff of proteomics firm Integrated Diagnostics, the company launched as a separate entity in September with $1.5 million in seed funding from InterWest Partners and co-founders including Albert Luderer, CEO of both Indi and Indi Molecular; James Heath, a California Institute of Technology researcher and inventor of the PCC technology; Lee Hood; and Michael Phelps, a University of California, Los Angeles, professor and inventor of PET imaging.
Indi originally planned to spin off Indi Molecular in 2012. These plans, however, were delayed by a year due to difficulties in lining up the needed financing. These financing difficulties also led to a shift in strategy, the company moving its focus from using the reagents for PET imaging and therapeutics to demonstrating their usefulness as biological research tools and in in vitro diagnostics.
One significant area of activity for the company has been developing the PCC technology for applications requiring highly stable reagents. PCCs can be stored as powders without refrigeration, making them potentially attractive for purposes such as field testing for biological agents.
In Indi Molecular's recent anthrax study, which was published in the October edition of ACS Nano, company researchers along with scientists from the US Army Research Laboratory developed PCCs capable of detecting the pathogen in the low-picomolar range. They also demonstrated that the reagents functioned after being stored for several days at 65° C.
This research was funded by a pair of US Department of Defense grants under which the company is working to develop PCCs against a series of targets of military interest, CalTech's Heath told ProteoMonitor.
"Antibodies," he said, "don't typically pass what you might think of as military specifications for ruggedness," which has led to an interest in PCCs as a potentially more robust alternative. In addition to collaborating with the Army on the anthrax research, Indi Molecular is also working to transfer portions of the PCC development technology to Army researchers so that they can develop reagents independently, Heath said, noting that help with technology development was one of the key benefits of the collaboration for the firm.
Military applications are "not central to [the company's] business model," he said. "The advantage [for Indi Molecular] is that this technology is still going through stages of invention, and having more hands working on it is beneficial to us."
Indi Molecular has also made inroads into HIV and malaria testing, where the PCC reagents' stability at high temperatures could prove an advantage for field testing. The company presented some of its HIV work in a PLOS One paper published in October. In that study, the researchers demonstrated that a cocktail of three PCCs was able to detect anti-HIV-1 antibodies in the sera of HIV-1 positive patients with better signal-to-noise than conventional tests relying on recombinant protein antigens. Use of a cocktail of PCCs, as opposed to a single reagent, helps to account for the diversity of anti-HIV-1 antibodies in the infected population, leading to improved sensitivity.
The HIV work was done under a $500,000 grant from the Bill & Melinda Gates Foundation. The PCC cocktail has been transferred to another team for validation, Heath said, adding that Indi Molecular has now turned its focus under the Gates grant to developing PCCs for detecting malaria.
Specifically, the company is working on developing reagents for use in the foundation's malaria eradication efforts – work that Heath said presents a particular set of challenges.
"Eradication isn't quite the same as just detecting malaria," he said. "Because when you're diagnosing active disease you have a reasonably high level of a number of different markers."
In the case of eradication, on the other hand, "you're trying to look at baseline levels," he said. "And some of these proteins you need to detect at very trace concentrations and in a way that is robust and will work in the field."
In addition, Heath noted, some of these protein targets exist in different forms in different parts of the world, meaning that an affinity reagent would ideally target protein regions conserved across different geographies. "Antibodies have a hard time doing that," he said.
Indi Molecular's Gates funding is due to end in 2014, but, Heath said, the company hopes to extend its relationship with the foundation for several more years to continue the malaria PCC work.
"We already have a panel of capture agents against many of the malaria targets, so now we need to start validating them," he said.
Key to the malaria work and one of the crucial attributes of the PCC technology in general, Heath said, is the ability of the reagents to target specific regions of a protein. While monoclonal antibodies can also be developed to target specific protein epitopes, the company believes its PCCs can do so with greater specificity and may also be able to target protein regions that the bulkier monoclonals are unable to access.
Heath and his CalTech colleagues demonstrated what he called a "first-generation" version of such epitope targeting in a study published in the November edition of Angewandte Chemie in which they developed a PCC targeting the serine 474 epitope of the protein Akt2, a phosphorylation site on an established cancer target.
The ability to target specific protein regions has obvious uses for protein research and diagnostic work, but the results of the Angewandte Chemie also suggest that PCCs could be promising therapeutic agents, as well.
In the study, the researchers were able to activate and inhibit Akt2 by binding the serine epitope with a PCC, suggesting that the reagents could potentially function as kinase inhibitors of sorts. However, while kinase inhibitors typically act by binding the protein's ATP binding pocket, the PCC works allosterically – controlling the kinase via binding at a site other than its active site.
This, Heath said, has potentially interesting therapeutic implications.
"There are 600 or so kinases out there, and they all have ATP binding pockets," he said. "So that's not exactly the most selective way to inhibit a protein. So if you can inhibit that same protein through an alternative mechanism, you have a pretty valuable and unique strategy for a therapeutic."
That said, drug development remains on the backburner, Heath said, noting that while the company has had success apply its reagents to this purpose, as a start-up "we don't have a lifetime on our own to develop a drug."
"We're quite serious about it being a valuable therapeutic strategy, but as soon as you tell an investor, they don't want to grow old waiting for you to develop a drug," he said. "But it does provide some potential partnering opportunities."