This study compared the pharmacodynamic/pharmacokinetic profile of the new renin inhibitor VTP-27999 in salt-depleted healthy volunteers, administered once daily (75, 150, 300, and 600 mg) for 10 days, versus placebo and 300 mg aliskiren. VTP-27999 was well tolerated with no significant safety issues. It was rapidly absorbed, attaining maximum plasma concentrations at 1 to 4 hours after dosing, with a terminal half-life of 24 to 30 hours. Plasma renin activity remained suppressed during the 24-hour dosing interval at all doses. VTP-27999 administration resulted in a dose-dependent induction of renin, increasing the concentration of plasma renin maximally 350-fold. This induction was greater than with aliskiren, indicating greater intrarenal renin inhibition. VTP-27999 decreased plasma angiotensin II and aldosterone. At 24 hours and later time points after dosing on day 10 in the 600-mg group, angiotensin II and aldosterone levels were increased, and plasma renin activity was also increased at 48 and 72 hours, compared with baseline. VTP-27999 decreased urinary aldosterone excretion versus placebo on day 1. On day 10, urinary aldosterone excretion was higher in the 300- and 600-mg VTP-27999 dose groups compared with baseline. VTP-27999 decreased blood pressure to the same degree as aliskiren. In conclusion, excessive intrarenal renin inhibition, obtained at VTP-27999 doses of 300 mg and higher, is accompanied by plasma renin rises, that after stopping drug intake, exceed the capacity of extrarenal VTP-27999 to block fully the enzymatic reaction. This results in significant rises of angiotensin II and aldosterone. Therefore, renin inhibition has an upper limit.
Keywords: aldosterone; angiotensins; blood pressure; humans; pharmacokinetics; renin.