Design of PAP-1, a selective small molecule Kv1.3 blocker, for the suppression of effector memory T cells in autoimmune diseases.
The lymphocyte K+ channel Kv1.3 constitutes an attractive pharmacological target for the selective suppression of terminally differentiated effector memory T (TEM) cells in T cell-mediated autoimmune diseases, such as multiple sclerosis and type 1 diabetes. Unfortunately, none of the existing small-molecule Kv1.3 blockers is selective, and many of them, such as correolide, 4-phenyl-4-[3-(methoxyphenyl)-3-oxo-2-azapropyl]cyclohexanone, and our own compound Psora-4 inhibit the cardiac K+ channel Kv1.5. By further exploring the structure-activity relationship around Psora-4 through a combination of traditional medicinal chemistry and whole-cell patch-clamp, we identified a series of new phenoxyalkoxypsoralens that exhibit 2- to 50-fold selectivity for Kv1.3 over Kv1.5, depending on their exact substitution pattern. The most potent and "drug-like" compound of this series, 5-(4-phenoxybutoxy)psoralen (PAP-1), blocks Kv1.3 in a use-dependent manner, with a Hill coefficient of 2 and an EC50 of 2 nM, by preferentially binding to the C-type inactivated state of the channel. PAP-1 is 23-fold selective over Kv1.5, 33- to 125-fold selective over other Kv1-family channels, and 500- to 7500-fold selective over Kv2.1, Kv3.1, Kv3.2, Kv4.2, HERG, calcium-activated K+ channels, Na+,Ca2+, and Cl- channels. PAP-1 does not exhibit cytotoxic or phototoxic effects, is negative in the Ames test, and affects cytochrome P450-dependent enzymes only at micromolar concentrations. PAP-1 potently inhibits the proliferation of human TEM cells and suppresses delayed type hypersensitivity, a TEM cell-mediated reaction, in rats. PAP-1 and several of its derivatives therefore constitute excellent new tools to further explore Kv1.3 as a target for immunosuppression and could potentially be developed into orally available immunomodulators.
Schmitz
Alexander
A
Department of Medical Pharmacology and Toxicology, Genome and Biomedical Sciences Facility, Room 3502, 451 East Health Sciences Drive, University of California, Davis, Davis, CA 95616, USA.
Sankaranarayanan
Ananthakrishnan
A
Azam
Philippe
P
Schmidt-Lassen
Kristina
K
Homerick
Daniel
D
Hänsel
Wolfram
W
Wulff
Heike
H
D000818:Animals; D001327:Autoimmune Diseases / Q000188:drug therapy* / Q000276:immunology; D002460:Cell Line; D065607:Cytochrome P-450 Enzyme Inhibitors; D015195:Drug Design; D005260:Female; D006801:Humans; D006968:Hypersensitivity, Delayed / Q000517:prevention & control*; D007156:Immunologic Memory / Q000187:drug effects*; D007166:Immunosuppressive Agents / Q000138:chemical synthesis / Q000494:pharmacology*; D008213:Lymphocyte Activation / Q000187:drug effects; D000073718:Pancreatitis-Associated Proteins; D026902:Potassium Channel Blockers / Q000138:chemical synthesis / Q000494:pharmacology*; D051381:Rats; D011917:Rats, Inbred Lew; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology
D065607:Cytochrome P-450 Enzyme Inhibitors; D007166:Immunosuppressive Agents; D000073718:Pancreatitis-Associated Proteins; D026902:Potassium Channel Blockers; C000612141:REG3A protein, human