Automated Dose Response Curve Fitting Outpaces Manual Operation

Summary

AstraZeneca (Alderley Park, UK) has developed a customized data processing application in Origin that can analyze up to 2,000 datasets per hour, an improvement of 50 to 100-fold over the number that scientists could analyze using previous methods.

The development of this application has given company scientists the freedom to spend more time on other aspects of drug research, as well as enabling AstraZeneca to perform high-throughput studies in which thousands of test compounds can be evaluated in the same experiment.

Large Volume of Data

In the development of new prescription medicines, AstraZeneca researchers perform concentration response studies to determine the biological response elicited by varying doses of certain compounds. Much of the data obtained from these studies exhibits a sigmoidal, or slanted "S" shape when plotted (log concentration on the x axis, measured response on the y axis). Several equations can be used to fit such sigmoidal data. Typically the logistic equation is used.

In the past, the task of performing each curve fit for these studies was tedious and time-consuming, mainly because there is so much data involved. These drawbacks led AstraZeneca to consider developing a customized application to automate each step of the curve fitting process.

It was determined that the customized application needed to have the ability to handle large datasets, perform nonlinear curve fitting, as well as create publication-quality plots.

After researching the available options and ruling out the possibility of creating something from scratch, AstraZeneca (Alderley Park, UK) decided to build upon Origin, a highly programmable graphing and data analysis software package.

Push-button Process

To implement the application in Origin, AstraZeneca utilized Origin's built-in programming capability, as well as the ability to interface custom DLLs with Origin's nonlinear curve fitter.

The application is designed to first import the desired data file including plate numbers, compound identifiers, and response values for each compound. The application then allows the researcher to change settings, such as how the data will be analyzed, viewed, or stored.

For fitting using the logistic equation, the application includes built-in parameter initialization code that vastly improves the speed with which each fit will converge. The code determines the approximate locations of the top of the curve, the bottom of the curve and the IC50. To perform the analyses, the application is designed so that all the researcher needs to do is press a button. Once a dataset is analyzed it is plotted (Fig. 1) for review. The researcher can then remove outliers, assign comments to individual compounds or graphs, or sort compounds in a particular order, e.g. by potency. When finished, the results can be saved as a single file or uploaded to a database. In all, the application typically handles curve fitting at a rate of 2,000 datasets per hour, enabling very high throughput studies.

Doing More with Origin

Although AstraZeneca's biggest benefits have come from using Origin to automate dose response data processing, the company has created other custom Origin applications as well. Some of these automate data handling for substrate dependence studies, ligand binding studies, and enzyme inhibition experiments. These applications are typically used to analyze fewer datasets but can compare curve fitting with up to eight different models and allow more detailed analysis.

About AstraZeneca

AstraZeneca, headquartered in London, is a major international healthcare business engaged in research, development, manufacturing, and marketing of prescription pharmaceuticals and the supply of healthcare services. It is one of the top five pharmaceutical companies in the world with healthcare sales in 2004 of $21.4 billion and leading positions in cardiovascular, gastrointestinal, oncology, central nervous system, and respiratory products. Products include: Losec (omerprazole), the biggest-selling pharmaceutical of all time; Nolvadex (tamoxifen citrate), the world's most prescribed breast cancer therapy; and Seloken (metroprolol), the world's leading cardioselective beta-blocker. AstraZeneca has more than 64,000 employees, manufacturing sites in 20 countries, and 11 major research centers in 7 countries.

On the web: http://www.astrazeneca.com/