Results: There were no relevant mutual pharmacokinetic interactions between OBE022 and MgSO4. OBE022 had no effect on atosiban. However, atosiban slightly reduced exposure to OBE002, the pharmacologically active metabolite of the pro-drug OBE022 (Cmax -28%, AUC 21%). OBE022 co-administered with betamethasone slightly increased betamethasone exposure (Cmax +18%, AUC +27%) and that of OBE002 (Cmax +30%, AUC +15%). These changes were not considered clinically relevant. OBE022 co-administered with nifedipine slightly increased OBE002 exposure (Cmax +29%, AUC +24%) and markedly increased nifedipine exposure (Cmax +133%, AUC +137%). All drugs, alone or in combination, were well tolerated. Headache and dizziness were the most frequent adverse events reported with dizziness occurring more often with OBE022/nifedipine (seven subjects) than with nifedipine alone (two subjects) or OBE022 alone (one subject).