GV-58 is a roscovitine analog th at retains the ability to prolong the open state of calcium channels, but unlike roscovitine, is inactive against Cdk activity. GV-58 is a selective agonist of N-type and P/Q type calcium channels, which are critical to the triggering of neurotransmitter release at the neuromuscular junction. GV-58 has been studied as a possible therapeutic agent in a mouse model of Lambert-Eaton myasthenic syndrome (LEMS). The EC50 values for activation of N-, P/Q- and L- type calcium channels are 6.8, 9.9 and >100 μM, respectively.