IC50 is lower than 0

Q&A
1

Some of the IC50 value in drug sensitivity databases is lower than 0. I am confused that how should we explain this data. For instance, IC50 of vinblastine (GDSC2:1004) on CCK81 is -5.550494585nM. (in Drug sensitivity IC50 (Sanger GDSC2))

Does it mean that this compound would enhance the cell proliferation instead of suppress the cell viability?

I would appreciate it if someone could give any reply. Thanks in advance :slight_smile:

2

Hi Yuwei,

My bet is you are looking at ln(IC50). It’s always good practice to plot histograms of your values, this quickly explains such confusions.

Best,
Fio

3

Yeah,I think so.The Expression Public 22Q4 GDSC2 IC50 dataset shows that the maximum is about 6.9,which corresponds to ln(1000).Being an undergraduate student,I just couldn’t understand why it’s not clearly demonstrated,so confusing.