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Updated: Jun 17, 2026
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Diagonal Method to Measure Synergy Among Any Number of Drugs
Published on: June 21, 2018
Emax model and interaction index for assessing drug interaction in combination studies
J Jack Lee1, Heather Y Lin, Diane D Liu
1Department of Biostatistics, The University of Texas MD Anderson Cancer Center, Unit 1411, 1515 Holcombe Boulevard, Houston, Texas 77030-1402, USA.
Frontiers in Bioscience (Elite Edition)
|December 29, 2009
Summary
This study on trimetrexate (TMQ) and AG2034 (AG) combination therapy found synergy at low drug ratios, especially in high folic acid (FA) media. Drug potency and synergy varied with FA concentration and drug ratios.
Area of Science:
- Pharmacology
- Drug Interactions
- Mathematical Modeling
Background:
- Combination drug therapy is crucial for optimizing treatment efficacy.
- Understanding drug interactions, such as synergy and additivity, is essential for dose optimization.
- Folic acid (FA) concentration can significantly influence the pharmacodynamics of antifolate drugs.
Purpose of the Study:
- To analyze the drug interaction between trimetrexate (TMQ) and AG2034 (AG) using the Emax model within a Lowe additivity framework.
- To investigate the impact of varying folic acid (FA) concentrations on the potency and synergy of the TMQ-AG combination.
- To determine the specific drug ratios that elicit synergistic, additive, or antagonistic effects.
Main Methods:
- Utilized the Emax model to analyze combination data from trimetrexate (TMQ) and AG2034 (AG).
- Data were collected from experiments conducted in media with low and high concentrations of folic acid (FA).
- Evaluated drug interactions across a range of TMQ:AG ratios to identify patterns of synergy and additivity.
Main Results:
- The Emax model adequately described the dose-response data for the TMQ-AG combination.
- Trimetrexate (TMQ) demonstrated higher potency than AG2034 (AG) in both low and high FA conditions.
- Synergy was observed at low TMQ:AG ratios, particularly in high FA media, while higher ratios led to additive effects.
- Drug potency was greater in low FA medium, but synergistic effects were stronger in high FA medium.
Conclusions:
- The interplay between drug ratio, FA concentration, and dose level dictates the nature of drug interaction (synergy vs. additivity).
- Optimizing the TMQ:AG ratio and FA concentration is critical for maximizing therapeutic synergy.
- The findings provide valuable insights for the rational design of combination therapies involving antifolates.
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