Parameter research has been the dominant practice in the complex world of modern drug discovery. Scientists and researchers measure a range of different factors including localization, protein levels, protein activity, and gene expression, and their preclinical findings are extrapolated into in vivo function for clinical application of the treatment in humans. But there are serious time and space limitations to the measurements as a result of the testing/diagnostic methods used. Measurements are carried out mainly in synthetic cell models based on two-dimensional growth of immortalized cell lines—very distant from the organ/tissue/whole organism that will receive the treatment.
There is thus a need in drug discovery and development to find effective ways to lessen the gap between synthetic test conditions and the real live response in humans. The solution lies in the application of phenotypic assays in which the total response of all life mechanisms is accounted for and captured in accurate findings.
Outcomes have all too often been less favorable from tests that have sought to extrapolate the effects in 2-D cell culture to the impact a compound has when applied in vivo to human patients. Clinical studies have frequently been unsuccessful, with limited efficacy or toxicological side effects. The screening of anti-cancer drugs performed in oxygen-rich 2-D cell culture is a prime example in which the chemical hits from very high specific metabolism in 2-D are widely different from screening on hypoxic 3-D cell cultures. Oxygen-starved conditions in the 3-D testing method much more closely match the situation in solid human tumors in vivo. Consequently, metabolism-based screening with phenotype readout of outputs makes screening closer to real-life conditions more possible.
The calScreener calorimetry-based assay (Figure 1) (SymCel Sverige AB, Spånga, Sweden) directly measures the release of energy. It is not measured via a proxy measurement and gives a direct and reliable measurement of cell activity with no labels or additions. The benefit of this technique is that it is not parameter testing—it is the only label-free and nondestructive technology for studying the net effect of every cellular parameter at once, and in the right context, irrespective of morphology and sample condition. When compared to most other technologies that utilize parameter-based (genotype) testing, calScreener is an accurate phenotype (functional) assay. Most assays are endpoint tests in which samples are gathered at a single or a limited number of time points. This is in contrast to the continuous kinetic measurement of the calScreener.
Figure 1 – calScreener.The assay’s Direct Metabolic Readout (DMR) provides researchers with access to an unbiased assay in which the effects of treatment are studied in a correct biological context that results in greater predictive value for cost-effective and rapid drug development. This bridges the gap between screening on isolated components to 2-D cell cultures to 3-D tissue to the in vivo impact in humans, increasing the predictive power of scientific hypothesis in drug development. calScreener enables the direct and continuous measurement of effects in conditions that are difficult or previously impossible to monitor, such as bacterial infections in complex matrices or 3-D cell cultures. The next step beyond 3-D-based drug discovery would be to apply the same testing approach to actual patient tissue samples to evaluate the best possible treatment based on a real patient’s response.
Magnus Jansson, Ph.D., is chief scientific officer, SymCel Sverige AB, Domnarvsgatan 4, SE-163 53 Spånga, Sweden; tel.: +46 8 5000 49 26; e-mail: [email protected]; www.symcel.se