Cligosiban (PF-3274167), a high oral bioavailability and good brain-penetrant non-peptide oxytocin receptor antagonist, shows a high-affinity (Ki=9.5 nM) and an excellent selectivity versus the vasopressin receptors with almost no affinity for the V1b and V1a subtypes. Cligosiban inhibits ejaculatory physiology in rodents[1][2].

References:
[1]. Wayman C, et al. Cligosiban, A Novel Brain-Penetrant, Selective Oxytocin Receptor Antagonist, Inhibits Ejaculatory Physiology in Rodents. J Sex Med. 2018 Dec;15(12):1698-1706.
[2]. Karpenko IA, et al. Selective nonpeptidic fluorescent ligands for oxytocin receptor: design, synthesis, and application to time-resolved FRET binding assay. J Med Chem. 2015 Mar 12;58(5):2547-52.