Biphenyl-derivatives of 2-amino-7-phosphono-heptanoic acid, a novel class of potent competitive N-methyl-D-aspartate receptor antagonists--II. Pharmacological characterization in vivo.

A selection of biphenyl-analogues of 2-amino-7-phosphonoheptanoic acid (AP7), N-methyl-D-aspartate (NMDA) receptor antagonists with high affinity in vivo efficacy. The lead compound SDZ EAB 515 was found to inhibit L-phenylalanine uptake by the large neutral amino acid carrier in vitro and in vivo; active transport may thus confer a good bioavailability to this class of compounds. CNS effects were demonstrated by significant changes in 2-deoxyglucose-uptake in various brain regions at doses from 1 to 10 mg/kg i.p. With the most active agent, SDZ 220-581, full protection against maximal electroshock seizures (MES) was obtained at oral doses of 10 mg/kg in rats and in mice. The compound had a fast onset (< or = 1 hr) and a long duration (> or = 24 hr) of action. Motor-debilitating effects (impairment of rotarod performance) occurred at doses about 10 times higher than those required for protection against MES. Neuroprotective activity was demonstrated by the ability of the compounds to reduce the extent of quinolinic acid-induced striatal lesions in rats, in the dose range of 3-15 mg/kg (i.p.) or 10-50 mg/kg (p.o.). In the middle cerebral artery occlusion (MCAO) model of focal cerebral ischemia in rats, the test compounds reduced the infarct size by 40-50% when given i.v. before or by 20-30% when given i.v. 1 hr after MCAO. SDZ 220-581 provided 20-30% protection at > or = 2 x 10 mg/kg p.o. This compound also showed analgesic activity at low oral doses in a model of neuropathic pain, although higher doses were required in model of mechanical inflammatory hyperalgesia. Unexpectedly, SDZ 220-581 at low s.c. doses counteracted the antiparkinsonian effects of L-DOPA in MPTP-treated marmosets. (Sub)chronic administration of SDZ 220-581 did not reduce its ability to protect against quinolinic acid neurotoxicity, and no upregulation of NMDA receptors was detected using a [3H]CGP-39653 binding assay. In conclusion, from a series of biphenyl-AP7-derivatives, SDZ 220-581 is clearly the most active compound in vivo. Its pharmacological profile with a good, long-lasting oral activity might open up novel therapeutic applications for competitive NMDA receptor antagonists.