Table 1.

“Drugability” attributes of peptide therapeutics compared with small molecules.

Virtues	Drawbacks
high activity, specificity and selectivity	low metabolic stability
few side-effects	short circulating half-life
no/less toxic degradation products	rapid body clearance if <5,000 Da [9]
no drug–drug interactions	low (oral) bioavailability, mainly parenteral administration needed
more in vivo predictability	poor membrane permeability
large interaction sides	sometimes reduced water solubility
biological and chemical variety	risk of immunogenic effects
able to target protein–protein interactions	expensive synthesis