Hi Satishkumar,

These terms are often used incorrectly so it's important to understand the difference.

IC50 is the drug concentration causing 50% inhibition of the desired activity. Strictly speaking, IC50 only applies for inhibition of a specified individual target, e.g. inhibition of an isolated enzyme, or reduction in fluorescence for a luciferase reporter assay for an individual protein of interest, etc.

For whole-cell assays, GI50 or ED50 should be used.

GI50 is the concentration for 50% of maximal inhibition of cell proliferation, and should be used for cytostatic (as opposed to cytotoxic) agents.

ED50 (or EC50) is the Dose (or Concentration) causing 50% of maximum effect for any measured biological effect of interest. This could include cytotoxicity (although in this case it is better to use LD50 in my opinion).

LD50 is the concentration causing 50% cell death (LD = lethal dose), although some people may have the opinion that LD50 should be reserved for in vivo studies only.

Hope all that is clear! Many of the terms are effectively used interchangeably during informal discussions which is OK, but it's important to use the correct one when writing up for publications etc.

All the best,

Mark

IC 50 is the maximal concentration of drug to cause 50% inhibition of biological activity of cancer cells

GI 50 is the concentration of drug to cause 50% reduction in proliferation of cancer cells i.e. growth

ED50 refers to the dose of the drug which causes 50%response in a biological system or which treats effectively 50% population

Hope this would help you

Hi Dr. Satishkumar D. Tala

All though the terms conveys the same meaning, but these terms conveys their own meaning in case of kind of research and statistics you do and present; say for example if you are drug is potentially inhibiting an inflammatory marker then you have to calculate IC50 concentration of the inhibition and express the effective concentration (EC50) in term of marketing.

All the best

Hi Satishkumar,

These terms are often used incorrectly so it's important to understand the difference.

IC50 is the drug concentration causing 50% inhibition of the desired activity. Strictly speaking, IC50 only applies for inhibition of a specified individual target, e.g. inhibition of an isolated enzyme, or reduction in fluorescence for a luciferase reporter assay for an individual protein of interest, etc.

For whole-cell assays, GI50 or ED50 should be used.

GI50 is the concentration for 50% of maximal inhibition of cell proliferation, and should be used for cytostatic (as opposed to cytotoxic) agents.

ED50 (or EC50) is the Dose (or Concentration) causing 50% of maximum effect for any measured biological effect of interest. This could include cytotoxicity (although in this case it is better to use LD50 in my opinion).

LD50 is the concentration causing 50% cell death (LD = lethal dose), although some people may have the opinion that LD50 should be reserved for in vivo studies only.

Hope all that is clear! Many of the terms are effectively used interchangeably during informal discussions which is OK, but it's important to use the correct one when writing up for publications etc.

All the best,

Mark

I am agree with Mark.

Hi Satishkumar,

Thanks to Mark for a good description. I just want to add that some tend to also bring the affinity (KD) of the drug into the same kind of discussion. The IC50/ED50/GI50 are often (not always) related to the affinity, but they are clearly different things. A high affinity binding drug often has good potency with low IC50/EC50/GI50 value, but you cannot take that for granted.

Just so that you are not tempted to compare an affinity valude with an IC50 for example. Unfortunately many do.

Best regards,

Karl

+1 on appreciating Mark's answer. FYI, I do hear IC50 used by research oncologists for driving mutation-targeted inhibitor drugs and never the other measures. Probably because for driving mutations, IC50 would be sufficient to stop the cancer from acting cancerous (i.e., resulting in either apoptosis or merely no proliferation, either of which would be very beneficial).

Best hopes,

Craig

well mr. satish I am totally agree with Shakila Mahalakshmi answers and I would like to add to it that IC and GI deals with concentration of drug in body fluid mainly blood and ED stands for the dose in mg/kg that is to be administered.

thank you.

In order not get confused, one should focus on what the experiment is designed for. If the experiment is designed to study a specific effect of a drug (or some other intervention); and a specific effect means a specific target (example: a kinase) or a specific assay platform endpoint (example: apoptosis), then you can express the results in a meaningful way only if you use the correct terminology. For in vitro work, there is no ED50. There is an EC50, which is the concentration at which the drug achieves the desired effect in 50% of the cells targeted. EC50 for apoptosis means that at that concentration 50% of the cells show the desired effect, which is in that case "apoptosis". When you are measuring something like cell death, obviously it would not make much sense to talk about inhibition or IC50 values. If you are killing cells, you cannot say that you are inhibiting them. If you are measuring colony formation or let's say proliferation (example : thymidine incorporation), you could certainly talk about IC50 values to give the concentrations at which 50% of colony formation or proliferation are inhibited. The IC50 values can also be used to describe the effects of a drug on a molecular target. In that case, IC50 and EC50 can both be used. The ED50 dose levels are for in vivo work usually to describe a dose at which 50% of the animals show the desired effect. But if you define the desired effect upfront, it can be used for various purposes. For example, if a desired effect is to keep an animal alive for 6 months, then the ED50 would be the dose at which 50% of the animals are alive at 6 months. If the desired effect is to keep the animal alive for 1 month, then the same drug would have a very different ED50 value because it would obviously be much easier to achieve that goal.

Take home message:

1. Define what you are measuring

2. Ask what makes more sense : are you measuring inhibition of something or not. If not use the effective concentration

3. Make sure the definition amkes sense and your use is transparent

FWIW, I would think that a patient with cancer would be disappointed if it were only possible to achieve a 50% reduction in the cancerous behavior-causing biochemical reaction (e.g., mutant or amplified or overactive kinase activity) rather than 50% apoptosis or 100% cessation of growth. Would it require close to single-digit IC50 values to translate into a strong benefit for patients and tolerable doses?

What is the method of the calculation of LD50, GI50, ED50

The best clarification and differentiation was made by Prof Fatih Uckun. It truly worth to read it again.

As it has been explained, I can add that IC50 is used in vitro experiments for inhibition while ED50 for invivo experiments for doses LD50 for invivo experiemnts corresponds to IC50

Thanks a lot for all friends and Profs. who give me the complete answer with support be in contact

How we can differentiate EC50 to ED50? Any suggestion.

is any difference between cell viability or % viability, % control growth and IC50 and GI 50. can we considered GI50 as IC50 ? 

Awanish Mishra, 

As I understand it, think of the EC50 and ED50 in terms of what Fatih Uckun mentioned above where you need to consider what is being tested. Dose-response curves that are used to determine the EC50 are testing how much effect is elicited by a range of doses, while dose-response curves that are used to determine ED50 are testing how much of the population obtains the desired effect from a range of doses. 

Essentially:

EC50 = dosage that elicits 50% of the max effect

ED50 = dosage that elicits the desired effect in 50% of the population

Thanks Ian Irvine,

As I think EC50 is Effective concentration for 50% population and this should be in vitro

while ED50 is effective dose for 50% population and this must be within in Vivo set up.

How you see my perspective.

I could full  agree with this opinion colleague Dr. Hossein Babaei The best clarification and differentiation was made by Prof. Fatih Uckun. It really worth to read it again.

Dear Satishkumar

briefly

LD50= The lethal concentration of a especial drug (Nanoparticles-Nanobubbles or any other particles) restrict maximum 50 percentages cell (cancer cell) proliferation.

GI50= (growth inhibitory dose 50%)is the probably same meaning but considering the more greater population of cells.

To summarize Satishkumar , the three parameters are totally and completely different. Then I suggest to plan your assay and then you will see by yourself or you may ask in another question which is right parameter for your experiment.

Perhaps you are reading a paper and, if this is the case, you may describe to us the experiment and ask why authors use IC50, ED50 or GI50.

Thanks Professor Fateh Uckun for the elaborate explanation. I have come across articles mentioning ED50 for cell lines data. Which written document can anyone suggest has the correct definitions of these terms in the cytotoxicity context??

Thank you and best regards.

Tabassum Khan

Generally, ED50 is used for animal or human studies and EC50 for cell culture experiment.

How we consider these values are:

IC50 is determined in an in vitro assay where we look at the inhibition of an enzyme target by a drug

GI50: is determined in culture by the amount of drug to inhibit 50% growth of cells

EC50: is a wider term used to describe what 'effect' you are looking for, if effect is growth of cell then EC50 will be GI50, if effect is DNA replication, that EC50 will be the concentration of drug (usually given as uM) required to reduce DNA replication by 50%

ED50: determined in vivo, just like EC50, ED50 depends on what effect you are looking for, it can be the growth of parasite inside the animal. so a dose (usually given as mg/kg) that causes 50% decrease in the parasitemia will be ED50

LD50: is the lethal dose, the dose which will kill 50% of your animal population when given in vivo. This is also in mg/kg, concentrations will be ng/ml or uM