The in vitro pharmacology of BL-1249

Holly Siggins, Liz Payne, Tim Young, Steve England. Pfizer, Sandwich, United Kingdom.

BL-1249 [(5,6,7,8-Tetrahydro-naphthalen-1-yl)-[2-(1H-tetrazol-5-yl)-phenyl]-amine] is reported to be a potassium channel opener, with potential capability to open K2P2.1 (TREK-1) channels. The use of such an agent may be beneficial within a number of therapeutic areas including pain and neuroprotection.

In this study, we have investigated the in vitro pharmacology of BL-1249 using both electrophysiology and traditional organ bath pharmacology assays. In cultured HEK-293 K2P2.1 (TREK-1) cells, BL-1249 caused a concentration dependent hyperpolarisation (EC50 1.63 (0.3-8.9) μM) and evoked outward potassium current. In DRG cells obtained from adult male Sprague Dawley rats (200g) BL-1249 produced complete attenuation of current induced action potential generation and caused hyperpolarisation of the resting membrane potential. In vitro organ bath experiments BL-1249 produced a concentration dependent relaxation of 30mM KCl contractions within male Sprague Dawley rat bladder strips (IC50 0.75 (0.55-1) μM), male Dunkin Hartley guinea pig ileum myenteric plexus (400g) (IC50 1.29 (1.13-1.46) μM) and male CD-1 mouse bladder strips (30g) (IC50 0.94 (0.86-1.02) μM) yet had no effect in precontracted rat aorta, prostatic and epididymal rat vas deferens and mouse vas deferens up to the highest concentration tested (10μM). BL-1249 also produced a concentration dependent inhibition of electrical field stimulation of rat bladder strips (IC50 0.73 (0.49-1.11) μM), prostatic rat vas deferens (IC50 1.42 (1.29-1.55) μM) and guinea pig ileum myenteric plexus (IC50 1.04 (0.81-1.33) μM) yet has no effect within epididymal rat vas deferens up to the highest concentration tested (10μM). Quantitative PCR of five twin pore potassium channels revealed relatively high expression of K2P2.1 (TREK-1) within rat bladder and prostatic rat vas deferens versus rat aorta and epididymal rat vas deferens.

In conclusion, the mechanism of action of BL-1249 shows differing effects. Within certain tissues BL-1249 exhibits its effects through direct hyperpolarisation of the smooth muscle. A clear neuronal effect can also be seen with BL-1249 on electrically stimulated prostatic rat vas deferens. We would tentatively suggest that the functional data, along with the quantitative PCR showing high expression levels of K2P2.1 (TREK-1), imply that BL-1249 is exhibiting its effects through the K2P channel, K2P2.1 (TREK-1). Therefore K2P2.1 (TREK-1) is a possible candidate target for BL-1249.