TY - JOUR
T1 - Design of a potent and selective inhibitor of the intermediate- conductance Ca2+-activated K+ channel, IKCa1
T2 - A potential immunosuppressant
AU - Wulff, Heike
AU - Miller, Mark J.
AU - Hänsel, Wolfram
AU - Grissmer, Stephan
AU - Cahalan, Michael D.
AU - Chandy, K. George
PY - 2000/7/5
Y1 - 2000/7/5
N2 - The antimycotic clotrimazole, a potent inhibitor of the intermediate- conductance calcium-activated K+ channel, IKCa1, is in clinical trials for the treatment of sickle cell disease and diarrhea and is effective in ameliorating the symptoms of rheumatoid arthritis. However, inhibition of cytochrome P450 enzymes by clotrimazole limits its therapeutic value. We have used a rational design strategy to develop a clotrimazole analog that selectively inhibits IKCa1 without blocking cytochrome P450 enzymes. A screen of 83 triarylmethanes revealed the pharmacophore for channel block to be different from that required for cytochrome P450 inhibition. The 'lKCa1- pharmacophore' consists of a (2-halogenophenyl)diphenylmethane moiety substituted by an unsubstituted polar π-electron-rich heterocycle (pyrazole or tetrazole) or a -C≡N group, whereas cytochrome P450 inhibition absolutely requires the imidazole ring. A series of pyrazoles, acetonitriles, and tetrazoles were synthesized and found to selectively block IKCa1. TRAM-34 (1- [(2-chlorophenyl)diphenylmethyl]-1H-pyrazole) inhibits the cloned and the native IKCa1 channel in human T lymphocytes with a K(d) of 20-25 nM and is 200- to 1,500-fold selective over other ion channels. Using TRAM-34, we show that blocking IKCa1 in human lymphocytes, in the absence of P450-inhibition, results in suppression of mitogen-stimulated [3H]thymidine incorporation of preactivated lymphocytes with EC50-values of 100 nM-1 μM depending on the donor. Combinations of TRAM-34 and cyclosporin A are more effective in suppressing lymphocyte mitogenesis than either compound alone. Our studies suggest that TRAM-34 and related compounds may hold therapeutic promise as immunosuppressants.
AB - The antimycotic clotrimazole, a potent inhibitor of the intermediate- conductance calcium-activated K+ channel, IKCa1, is in clinical trials for the treatment of sickle cell disease and diarrhea and is effective in ameliorating the symptoms of rheumatoid arthritis. However, inhibition of cytochrome P450 enzymes by clotrimazole limits its therapeutic value. We have used a rational design strategy to develop a clotrimazole analog that selectively inhibits IKCa1 without blocking cytochrome P450 enzymes. A screen of 83 triarylmethanes revealed the pharmacophore for channel block to be different from that required for cytochrome P450 inhibition. The 'lKCa1- pharmacophore' consists of a (2-halogenophenyl)diphenylmethane moiety substituted by an unsubstituted polar π-electron-rich heterocycle (pyrazole or tetrazole) or a -C≡N group, whereas cytochrome P450 inhibition absolutely requires the imidazole ring. A series of pyrazoles, acetonitriles, and tetrazoles were synthesized and found to selectively block IKCa1. TRAM-34 (1- [(2-chlorophenyl)diphenylmethyl]-1H-pyrazole) inhibits the cloned and the native IKCa1 channel in human T lymphocytes with a K(d) of 20-25 nM and is 200- to 1,500-fold selective over other ion channels. Using TRAM-34, we show that blocking IKCa1 in human lymphocytes, in the absence of P450-inhibition, results in suppression of mitogen-stimulated [3H]thymidine incorporation of preactivated lymphocytes with EC50-values of 100 nM-1 μM depending on the donor. Combinations of TRAM-34 and cyclosporin A are more effective in suppressing lymphocyte mitogenesis than either compound alone. Our studies suggest that TRAM-34 and related compounds may hold therapeutic promise as immunosuppressants.
UR - http://www.scopus.com/inward/record.url?scp=0034608869&partnerID=8YFLogxK
U2 - 10.1073/pnas.97.14.8151
DO - 10.1073/pnas.97.14.8151
M3 - Article
C2 - 10884437
AN - SCOPUS:0034608869
SN - 0027-8424
VL - 97
SP - 8151
EP - 8156
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 14
ER -