Cara possesses best-in-class peripherally-selective molecules that interact with kappa opioid receptors present on peripheral, pain-sensing nerves. These compounds exhibit potent analgesic and anti-inflammatory properties in animals. Unlike currently marketed opioids, these new compounds do not produce inhibition of intestinal transit (ileus), do not induce life-threatening respiratory depression, nor do they elicit signs of addiction or euphoria in animal models.

The degree of kappa receptor selectivity displayed by CR665 (also seen with analogs such as CR666) ranks as best-in-class compared to all other previously developed compounds for this therapeutic target. Moreover, CR665 displayed no significant affinity for any other non-opioid known receptors.