Prostaglandin I2 is an unstable prostanoid which, through the 'I prostanoid' (IP) receptor, inhibits platelet aggregation and promotes vasodilatation in pulmonary vascular beds. AFP 07 is a 7,7-difluoroprostacyclin derivative that acts as a selective and highly potent agonist for the IP receptor (Ki = 0.561 nM). AFP 07 shows weaker affinity for EP receptors, with Ki values > 100 nM for EP1-3 and > 10 nM for EP4. 16(R)-AFP 07 is an epimer of AFP 07. Its biological properties, particularly through the IP and EP receptors, remain to be evaluated.