GGF2 is a recombinant human neuregulin-1β in development for chronic
heart failure. Phase 1 clinical trials of
GGF2 were put on hold when transient elevations in serum
aminotransferases and total
bilirubin were observed in 2 of 43 subjects who received single doses of
GGF2 at 1.5 or 0.378 mg/kg. However,
aminotransferase elevations were modest and not typical of liver injury sufficient to result in elevated serum
bilirubin. Cynomolgus monkeys administered a single 15 mg/kg dose of
GGF2 had similar transient elevations in serum
aminotransferases and
bilirubin as well as transient elevations in serum
bile acids. However, no hepatocellular
necrosis was observed in liver biopsies obtained during peak elevations. When sandwich-cultured human hepatocytes were treated with
GGF2 for up to 72 h at concentrations approximately 0.8-fold average plasma Cmax for the 0.378 mg/kg dose, no cytotoxicity was observed. Gene expression profiling identified approximately 50% reductions in mRNAs coding for
bilirubin transporters and
bile acid conjugating
enzymes, as well as changes in expression of additional genes mimicking the interleukin-6-mediated
acute phase response. Similar gene expression changes were observed in GGF2-treated HepG2 cells and primary monkey hepatocytes. Additional studies conducted in sandwich-cultured human hepatocytes revealed a transient and
GGF2 concentration-dependent decrease in hepatocyte
bile acid content and biliary clearance of
taurocholate without affecting biliary
taurocholate efflux. Taken together, these data suggest that
GGF2 does not cause significant hepatocellular death, but transiently modifies hepatic handling of
bilirubin and
bile acids, effects that may account for the elevations in serum
bilirubin observed in the clinical trial subjects.