Istradefylline

A potent and highly selective A2A receptor antagonist with Ki of 2.2 nM; significantly increases the total counts of turning induced by apomorphine at doses 1 mg/kg, p.o.; also potentiates the rotational behavior induced by L-DOPA at a dose of 3 mg/kg, p.o. (In Vitro) :Istradefylline has 70-fold greater affinity for the A2AR than the A1 receptor with Ki of 2.2 nM versus 150 nM. Istradefylline causes concentration-dependent abolition of bFGF induction of astrogliosis in primary rat striatal astrocytes. Istradefylline binds to A1 receptor, A2A receptor, and A3 receptor in human with Kis of >287 nM, 9.12 nM, and >681 nM, respectively, 50.9 nM and 1.57 nM for A1 receptor and A2A receptor in rat, 105.02 nM and 1.87 nM for A1 receptor and A2A receptor in mouse, respectively. (In Vivo) :Istradefylline (3.3 mg/kg, i.p.) treatment before a single dose of MPTP attenuates the partial dopamine and DOPAC depletions measured in striata 1 week later. Istradefylline reverses CGS21680-induced and reserpine-induced catalepsy with an ED50 of 0.05 mg/kg and 0.26 mg/kg, respectively. Istradefylline is over 10 times as potent in these models compared to other adenosine antagonists and dopamine agonist drugs. Istradefylline combined with L-dopa cuases potent effects on haloperidol-induced and reserpine-induced catalepsy. Istradefylline (10 mg/kg, p.o.) results an increase in locomotor activity to approximately twice that of control and improves motor disability in MPTP-treated common marmosets. Istradefylline (10 mg/kg, p.o.) in combination with SKF80723, quinpirole, or L-DOPA produces a significant additive effect on locomotor activity and improvement of motor disability but not dysKinesia.