6β-PGI1 is a stable PGI2 analog resistant to hydrolysis in aqueous solutions. 6β-PGI1 has a much longer half-life than PGI2, but a greatly reduced molar potency for receptor mediated function. 6β-PGI1 has a Kact for adenylate cyclase in NCB-20 cells of 4.2 μM compared with 18 nM for PGI2. The potency for vasodilation and inhibition of platelet aggregation is about 1% of PGI2.{509,1926}