Modulation of the TRPV1 channel: current clinical trials and recent patents with focus on neurological conditions.

The transient receptor potential vanilloid-1 cat ion channel (TRPV1) is a nonspecific cation channel that can be activated by multiple endogenous stimuli and is expressed predominantly in sensory neurons, where it serves as a key nodal point in pain transmission pathways. In mammals, TRPV1 displays a wide tissue and cellular expression including both the peripheral and central nervous system, and in the latter it is now recognized to have a broader distribution and function. The pharmacological modulation of TRPV1 represents a strategy for the treatment of a variety of disease states, particularly those requiring chronic pain management. The validation of the TRPV1 channel as a therapeutic target for the control of pain and inflammatory conditions in a variety of diseases and injury states, has prompted the development of several TRPV1 agonists and antagonists that have entered clinical trials. Studies comparing the analgesic effects of TRPV1 antagonists with and without significant CNS penetration demonstrated that a dual (both peripheral and central) action is required to produce broad-spectrum analgesia. TRPV1 can be considered as a target for next generation analgesics. However, although a number of compounds are in clinical trials, the therapeutic utility of TRPV1 agonist and antagonists is yet to be validated unequivocally. This review summarizes current clinical trials and recent patents with small molecule TRPV1 agonists and antagonists with a focus on neurological conditions.