# IC50 is lower than 0

**URL:** <https://forum.depmap.org/t/ic50-is-lower-than-0/1652>\
**Category:** Q&A\
**Created:** [August 20, 2022, 6:42am UTC](https://forum.depmap.org/t/ic50-is-lower-than-0/1652 "2022-08-20T06:42:01Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Yuwei](https://avatars.discourse-cdn.com/v4/letter/y/5daacb/32.png) [@Yuwei](https://forum.depmap.org/u/Yuwei)\
**Post date:** [August 20, 2022, 6:42am UTC](https://forum.depmap.org/t/ic50-is-lower-than-0/1652/1 "2022-08-20T06:42:01Z")

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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 🙂

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**Author:** ![fschischlik](https://avatars.discourse-cdn.com/v4/letter/f/ecd19e/32.png) [@fschischlik](https://forum.depmap.org/u/fschischlik)\
**Post date:** [October 6, 2022, 2:24pm UTC](https://forum.depmap.org/t/ic50-is-lower-than-0/1652/2 "2022-10-06T14:24:25Z")

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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

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**Author:** ![Erchen](https://avatars.discourse-cdn.com/v4/letter/e/6de8d8/32.png) [@Erchen](https://forum.depmap.org/u/Erchen)\
**Post date:** [May 21, 2023, 10:14pm UTC](https://forum.depmap.org/t/ic50-is-lower-than-0/1652/3 "2023-05-21T22:14:17Z")

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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.