The "Rule of 5" mnemonic

Poor absorption or permeation are more likely when:

• There are more than 5 H-bond donors
• The MWT is over 500
• The MLOGP is over 4.15 (or CLOGP is over 5)
• The sum of N's and O's is over 10

Substrates for transporters and natural products
are exceptions

Chris Lipinski, Pfizer