It is best to use the average IC50 value (In fact in most of the manuscripts you would find the IC50 as single value without SD). The error associated with each IC50 value do influence the QSAR model built, and that is why various R matrices come handy to validate & justify the predictive ability of the model built. Also notice that the singular IC50 values when transformed to pIC50 values, as the data is linearized &  the SD in the IC50 values minimized in my opinion.  

Dear Toufik,

There are two ways to proceed ahead:

1. Use the average values

2. Use the IC50 values from the same experimental conditions and then convert them into PIC50 in order to construct the model.

Dear Mohsin,

Thank you for your answer,

Regarding the conversion from IC50 to pIC50 the problem is that IC50 values are not fixed they contain deviations. for exemple for one compound IC50 = 10.80 +/- 3.01

so how could we convert this value without its SD? 

Yeah, one can avoid the uncertainty(i.e convert 10.80 into pic50 and leave the +/- 3.01). However, the best way is "not to incorporate the molecules whose activity is uncertain " This is only possible if one has enough number of active compounds otherwise stay with avoiding uncertainties. 

Is there any special software to do this transform?

Dear Tofiq,

Could you please be more specific? About which transformation you are enquiring for?

You could use our scripts for such conversion (DelG-to-Kd and IC50-to-pIC50 converter) at http://shityakovlab.uphero.com/hardware-and-software.html

Hi,

For converting IC50 to pIC50 you can use our lab online tool, Please follow the link

https://www.sanjeevslab.org/tools.html

Happy conversion!!! Thanks,

Code PIC50 to IC50 and IC50 to PIC50 calculator

This is an opensource free software for the required calculation. Its simple to use.

Wolfram Mathematica or MATLAB.

Simply give your IC50 value and get your pIC50 online through

https://www.sanjeevslab.org/tools.html

Selvaraj, C., Tripathi, S. K., Reddy, K. K., & Singh, S. K. (2011). Tool development for Prediction of pIC 50 values from the IC 50 values-A pIC 50 value calculator. Current Trends in Biotechnology & Pharmacy, 5(2).

Happy easy, hassle free conversion!!!!

you can calculate pIC50 using python numpy library following code:

import numpy as np

df['pIC50 '] = np.log(df['IC50'] * 0.001) * (-1)

(you can apply this to a pandas dataframe)

pIC50 becomes interesting when it is equal to or great than 6.0