In vitro activity: Unlike clotrimazole, TRAM-34 selectively inhibits IKCa1 without blocking cytochrome P450 enzyme (CYP3A4). TRAM-34 potently inhibits cloned IKCa1 channel in IKCa1-transfected COS-7 cells as well as native IKCa currents in human T lymphocytes and T84 cells with Kd of 20 nM, 25 nM, and 22 nM, respectively, more potently than clotrimazole with Kd of 70 nM, 100 nM, and 90 nM, respectively. TRAM-34 exhibits 200- to 1,500-fold selectivity over other ion channels such as KV, BKCa, SKCa, Na+, CRAC and Cl- channels. TRAM-34 significantly inhibits anti-CD3 Ab or PKC-activator PMA plus calcium-ionophore ionomycin induced activation of human T lymphocytes with IC50 of 295-910 nM and 85-830 nM, respectively. TRAM-34 (5 μM) does not inhibit cell viability of human T lymphocytes or several cell lines. TRAM-34 significantly inhibits EGF-induced IKCa1 up-regulation, and EGF-stimulated proliferation of A7r5 cells with IC50 of 8 nM. TRAM-34 treatment inhibits proliferation of human endometrial cancer (EC) cells, and blocks EC cell cycle at G0/G1 phase. Inhibition of the IKCa1 channel by TRAM-34 (1-30 μM) leads to dose-dependent suppression of the proliferation but not apoptosis of LNCaP and PC-3 prostate cancer (PCa) cells, involving an increase of p21Cip1 and cell arrest in the G1 cycle

Kinase Assay: The human IKCa1 is cloned and expressed in COS-7 cells. Cells are studied in the whole-cell configuration of the patch-clamp technique. The holding potential is 280 mV. The internal pipette solution contains: 145 mM K+ aspartate, 2 mM MgCl2, 10 mM Hepes, 10 mM K2EGTA, and 8.5 mM CaCl2 (1 μM free Ca2+), pH 7.2, 290-310 mOsm. To reduce currents from the native chloride channels in COS-7 cells, Na+ aspartate Ringer is used as an external solution: 160 mM Na+ aspartatey/4.5 mM KCl/2 mM CaCl2/1 mM MgCl2/5 mM Hepes, pH 7.4/290-310 mOsm. IKCa currents in COS-7 cells are elicited by 200-ms voltage ramps from -120 mV to 40 mV applied every 10 seconds and the reduction of slope conductance at -80 mV by TRAM-34 taken as a measure of channel block.

Cell Assay: Cells (Human T lymphocytes, Jurkat E6-1, MEL, C2F3, CHO, COS-7, L929, NGP, NLF, and RBL-2H3) are exposed to TRAM-34 for 48 hours. After 48 hours, cells are harvested by suction (suspension cells) or by trypsinization (adherent cell lines), centrifuged, resuspended in 0.5 mL PBS containing 1 μg/mL propidium iodide (PI), and red fluorescence measured on a FACScan flow cytometer. The percentage of dead cells is determined by their PI uptake, 104 cells of every sample being analyzed.

Br J Pharmacol. 2001 May;133(1):193-9; Horm Metab Res. 1996 Sep;28(9):469-87; Indian J Exp Biol. 2009 Oct;47(10):804-10.