SynergyFinderSynergyFinder™ helps to ensure that new therapies are combined in the best way possible. Many therapies, particular in oncology, are applied as combination therapies. To identify the right combination of your lead compound with standards of care or new drugs, NTRC has developed SynergyFinder™.

SynergyFinder™ characteristics


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Pre-profiled compounds

Synergy testing requires detailed knowledge of the expected response of single agents, to be able to test the appropriate concentration ranges in a combination experiment. To expedite synergy testing, NTRC has predetermined IC50s, curve shapes and efficacy parameters of many relevant drugs and drug candidates in the OncolinesTM panel. Pre-profiled compound sets include

For a complete list of pre-profiled compounds, please send an e-mail to

Distinguishing synergy from additivity

The goal of a SynergyFinderTM experiment is to identify cases where the joint effect of a compound combination is improved compared to the additive effects of the individual compounds.
At NTRC we have developed two experimental set-ups to measure synergy, the fixed IC50 ratio experiment and the fixed dose combination experiment.

Fixed IC50 ratio experiment

This is the most robust experiment if the single agents show well-behaved dose-response curves. Based on predetermined IC50s of the single agents, mixtures are generated with theoretical equipotency compared to the single agents. Subsequently, dose response curves of these mixtures are measured in duplicate in an OncolinesTM cellular assay. A left-ward curve shift compared to the single agent curves indicates synergy [2].

curve shift

Example of curve shift due to synergistic interaction between a PI3-kinase and a MEK inhibitor.

CI Index

As a secondary analysis, we use the experimental data to generate Chou-Talalay Combination Indices [3] providing an independent, quantitative assessment of synergy. The CI is dependent on the fraction effect considered (e.g. 0.75, 75% growth inhibition). Generally a CI < 1 indicates synergy for a compound pair, a CI < 0.3 indicates strong synergy [4].

Combination index analysis
Combination index analysis (CI) for the combination of a PI3-kinase and MEK inhibitor. Circles represent experimentally determined CI values (Chou-Talalay method).

Fixed dose combination experiment

In some cases it can be advantageous to combine fixed and variable compound doses in a synergy experiment e.g. if single agents show little activity.
In this experiment NTRC combines a fixed concentration of the first compound with seven concentrations of the second compound. The single agent activities have first been assessed in duplicate in an Oncolines™ cellular assay.

Customised studies and large combinatorial screens

The service SynergyFinder™ is highly suitable for small-scale, customised studies as well as large combinatorial screens. Customised studies can be performed for a selection of Oncolines™ cell lines. Usually these studies are based on hypotheses regarding genetic background and targetting of compounds [1, 5]. Large combinatorial screens are generally performed on the full panel on Oncolines™ cell lines, with the purpose to look broadly for opportunities that may go beyond rationalisation. For more information and request for a quotation, please send an e-mail to

[1] Uitdehaag et al (2015) PLoS ONE 10(5): e0125021
[2] Zhao et al. (2004) Clin. Cancer Res. 10, 7994-8004
[3] Chou et al. (2010) Cancer Res. 70, 440-446
[4] Haagensen et al. (2012) Br. J. Cancer 106, 1386-1394
[5] Canté-Barrett al. (2016) Leukemia, advance online publication