Potency and stability of C terminal truncated human epidermal growth factor

Introduction - Epidermal growth factor (EGF) is normally present as EGF1-53. A variety of C terminal truncated forms have been used in preliminary trials for treating gastrointestinal injury but their relative potency and stability when used in a clinical setting are unclear. Therefore, we compared the biological activity of recombinant EGF1-53, EGF1-52, EGF1-51, and the C terminal peptides EGF44-53 and EGF49-53. Methods - Purity of forms was confirmed by mass spectrometry. Bioactivity of the different EGF forms was determined using [methyl-3H] thymidine incorporation into primary rat hepatocytes and their ability to reduce indomethacin (20 mg/kg subcutaneously)/restraint induced gastric injury in rats. Stability of EGF peptides was determined by serial sampling from a syringe driver system containing: EGF/4% albumin in saline. Results - Biological activity assays of EGF1-53, EGF1-52, and EGF1-51 gave almost identical thymidine uptake dose-response curves (maximal responses increasing baseline uptake from 4400 (600) cpm (mean (SEM)) to about 22 000 (2000) cpm when EGF was added at 1.6 nM). EGF44-53 and EGF49-53 did not stimulate 3H thymidine uptake. Control rats had 47 (4) mm2 damage/stomach, EGF1-51, EGF1-52, and EGF1-53 at 0.16 and 0.80 nmol/kg/h each reduced gastric injury by about 50% and 80%, respectively (both doses p<0.01 compared with control but no significant difference between the different forms). EGF was stable at room temperature for seven days but biological activity decreased by 35% and 40% at two and three weeks, respectively (both p<0.01). Exposure to light did not affect bioactivity. Conclusion - EGF1-51 and EGF1-52 are as biologically active as full length EGF1-53 but the C terminal penta- and decapeptides are ineffective. Clinical trials of EGF can probably use infusion systems for at least 48 hours at room temperature and with exposure to light, without reducing biological efficacy.