New, Potent, Selective, and Short-Acting Peptidic V1a Receptor Agonists

[Arg8]vasopressin (AVP) produces vasoconstriction via V1a receptor (V1aR)-mediated vascular smooth muscle cell contraction and is being used to increase blood pressure in septic shock, a form of vasodilatory hypotension. However, AVP also induces V2 receptor (V2R)-mediated antidiuresis, vasodilation, and coagulation factor release, all deleterious in septic shock. The V1aR agonist terlipressin (H-Gly3[Lys8]VP) also lacks selectivity vs the V2R and has sizably longer duration of action than AVP, preventing rapid titration of its vasopressor effect in the clinic. We designed and synthesized new short acting V1aR selective analogues of general structure [Xaa2,Ile3,Yaa4,Zaa8]VP. The most potent and selective compounds in in vitro functional assays (e.g., [Phe2,Ile3,Asn(Me2)4,Orn8]VP (31), [Phe2,Ile3,Asn((CH2)3OH)4,Orn8]VP (34), [Phe2,Ile3,Hgn4,Orn(iPr)8]VP (45), [Phe2,Ile3,Asn(Et)4,Dab8]VP (49), [Thi2,Ile3,Orn(iPr)8]VP (59), [Cha2,Ile3,Asn4,Orn(iPr)8]VP (68)) were tested by intravenous bolus in rats for durat...