The Bioisosteric Concept Applied to Cannabinoid Ligands

Bioisosterism is widely used in medicinal chemistry as an approach aimed at either rationally modifying a hit compound into a more potent and/or selective molecule or a lead compound into a more drug-like one. Two different cannabinoid receptors have been cloned from mammalian tissues, the CB1 receptor, mostly expressed in brain, and the CB2 receptor, mostly expressed in the immune system, both regulating a variety of physiological functions. Synthetic cannabinoids have been developed that act as highly selective agonists or antagonists/inverse agonists at one or other of these receptor types with the ultimate goal of modulating the endocannabinoid system. This review takes into account the use of the bioisosteric substitution in the field of cannabinoid ligands as a tool for improving both their pharmacodynamic and pharmacokinetic properties.