Odyssey Thera scientists have published research demonstrating how the firm's flagship protein-fragment complementation cell-based assay can be used with high-content imaging to profile drug activity, including structure-function relationships, selectivity, and off-target effects.
The research, which appears in the May 7 online edition of Nature Chemical Biology, helps to validate Odyssey's strategy of pathway-based drug activity profiling in living cells, and may serve to supplement the company's internal drug-discovery program with revenues from assay licensing and service deals.
Through Odyssey's PCA technology, cells are engineered to express two proteins fused to complementary fragments of a reporter protein, typically GFP or some variation thereof. The reporter protein produces a signal only if the cellular proteins interact, thereby bringing the reporter fragments close enough to one another to fold together into an active molecule.
As described in the paper, which will also be published in the June print issue of NCB, Odyssey scientists constructed 49 different PCAs for known protein complexes to act as reporters for activation or inhibition of several well-characterized cellular pathways, such as the insulin, growth-factor dependent, AKT kinase, erythropoietin, TGF-ß, and TNK signaling pathways. The researchers used a variant of yellow fluorescent protein as the reporter molecule, and the PCAs were engineered in HEK 293 cells.
"We feel that drug candidate profiling for selectivity and safety is a key application of this technology, [and] in fact, we are actively applying this strategy to our own and our partners' drug candidates."
The cells were plated in 96-well plates, treated with 107 different drugs representing six therapeutic areas (cancer, inflammation, cardiovascular disease, diabetes, neurological disorders, and infectious disease); counterstained with cell compartment-specific dyes; fixed; and imaged using high-throughput automated microscopy.
Although the specific instrument is not described in the paper, in August CBA News reported that Odyssey had purchased two Opera confocal readers from Evotec Technologies, which it expected to use for the bulk of its PCA-based work (see CBA News, 8/29/2005). Odyssey also said at the time that it uses a variety of other plate readers, microscopes, and flow cytometers in its work. In addition, according to the NCB paper, the researchers used a Discovery-1 automated microscope from Molecular Devices to conduct follow-up assays.
Using the automated imaging platform and appropriate image-analysis algorithms, the researchers quantified drug effects such as increases, decreases, or changes in sub-cellular localization of fluorescence signals at particular times of treatment. This allowed them to then create a matrix out of the resultant 127 assay-time point combinations and 13,589 overall data points, which could be used to cluster drugs with similar activities and glean information about specific drugs' activities.
The assay data revealed that chemically related drugs had similar activity profiles, and those activity profiles for those drugs also matched previously published reports. More importantly, according to Odyssey, the data revealed that four drugs harbored previously unreported anti-proliferative activity: the antihyperlipidemic fenofibrate; the anthelminthic niclosamide; cinnarizine, which is used to treat vertigo; and the antidepressant sertraline (Zoloft).
"We observed numerous unexpected or 'hidden' drug effects, some of which could be exploited for therapeutic benefit," John Westwick, president and CSO of Odyssey Thera, said in a statement. "Of course, hidden activities are also responsible for the high rate of drug failure during development. We feel that drug candidate profiling for selectivity and safety is a key application of this technology, [and] in fact, we are actively applying this strategy to our own and our partners' drug candidates."
Odyssey hopes that the proof-of-principle paper will spur interest from the drug-discovery community and future revenues from either licensing the PCA technology or partnering with pharmaceutical and biotech companies for PCA-related collaborative projects.
Odyssey's internal drug-discovery program consists primarily of conducting work similar to that described in the NCB paper: screening known drugs to identify possible new indications, primarily for the treatment of cancer. But drug discovery is an expensive proposition for a small biotech, and a steady revenue stream from a proprietary technology is necessary to support such endeavors.
Similar companies have tried and failed to simultaneously be an assay vendor or service provider and conduct internal drug discovery. Recent examples include Danish biotech BioImage, which last year scrapped its internal discovery program and last month sold its Redistribution assay technology to Fisher Biosciences (see CBA News, 4/28/2006); and Xsira Pharmaceuticals, formerly Norak Biosciences, which last year sold off its Transfluor technology to Molecular Devices so it could focus entirely on drug discovery (see CBA News, 3/15/2005).
It is unclear whether or how long Odyssey will continue to nurture both businesses; Odyssey officials could not be reached for comment. But, after a spate of collaboration agreements with pharma companies in 2005 and 2004, and an August 2005 agreement to provide PCA cell lines to the National Institutes of Health's Chemical Genomics Center (CBA News, 8/29/2005), the company has yet to disclose new partnerships or assay licensing agreements.
Odyssey also has not disclosed the progress of its internal drug discovery program, stating on its website only that it has generated a pipeline of targeted drugs for "a variety of human conditions including inflammation, diabetes, obesity, osteoporosis, and neurological disorders."
Ben Butkus ([email protected])