Effect of repeated doses of netazepide, a gastrin receptor antagonist, omeprazole and placebo on 24 h gastric acidity and gastrin in healthy subjects

Aim To administer repeated oral doses of netazepide to healthy subjects for the first time, to assess safety, tolerability, pharmacokinetics and effect on 24 h gastric pH and plasma gastrin. Method We did two randomized, double‐blind, parallel group studies. The first compared netazepide 25 and 100 mg 12 hourly, omeprazole 20 mg once daily and placebo for 7 days. On day 7 only, we measured pH and assayed plasma gastrin. The second study compared netazepide 5, 10 and 25 mg and placebo once daily for 14 days. We measured pH on days 1, 7 and 14 and assayed plasma gastrin on days 1 and 14. We compared treatments by time gastric pH ≥ 4 during 0–4, 4–9, 9–13 and 13–24 h after the morning dose, and by plasma gastrin. P < 0.05 was significant. Results Netazepide was well tolerated. On day 7 of the first study, netazepide increased pH significantly only during 9–13 h after the 100 mg dose, whereas omeprazole raised pH significantly during all periods. Both netazepide and omeprazole increased plasma gastrin significantly. Netazepide had linear pharmacokinetics. In the second study, netazepide caused dose‐dependent, sustained increases in pH on day 1, but as in the first study, netazepide had little effect on pH on days 7 and 14. Again, netazepide increased plasma gastrin significantly. Conclusion Although repeated doses of netazepide led to tolerance to its effect on pH , the accompanying increase in plasma gastrin is consistent with continued inhibition of acid secretion, via gastrin receptor antagonism and gene up‐regulation.