Inhibition of lysophosphatidic acid-induced neurite retraction and cell rounding by SR 57746A

SR 57746A/xaliproden, a non-peptide neurotrophic compound: prospects and constraints for the treatment of nervous system diseases

Neurodegenerative disorders such as Alzheimer's disease or amyotrophic lateral sclerosis as well as peripheral neuropathies are difficult to treat due to a limited range of effective drugs. Neurotrophic growth factors promote neuronal survival and differentiation and could hence be interesting tools to treat these diseases. Their therapeutic use is limited due their short half-life, their inability to cross the BBB and potential side effects including tumor promotion. SR 57746A is a non-peptide, orally active compound that exhibits neuroprotective effects in various model systems in vitro and in vivo. SR 57746A shows--amongst other activities--agonistic activity on 5-HT(1A) receptors. Several clinical trials examined SR 57746A in patients with Alzheimer's disease, amyotrophic lateral sclerosis or chemotherapy-induced peripheral sensory neuropathy. This article reviews the preclinical and clinical data on SR 57746A and points out potential future applications of this compound. However, due to disapointing results in phase III trials, Sanofi-Aventis recently decided to discontinue the development of this drug.

5-HT1A receptors are involved in the effects of xaliproden on G-protein activation, neurotransmitter release and nociception

BACKGROUND AND PURPOSE

Xaliproden (SR57746A) is a 5-HT(1A) receptor agonist and neurotrophic agent that reduces oxaliplatin-mediated neuropathy in clinical trials. The present study investigated its profile on in vitro transduction, neurochemical responses and acute nociceptive pain tests in rats.

EXPERIMENTAL APPROACH

Xaliproden was tested on models associated with 5-HT(1A) receptor activation including G-protein activation, extracellular dopamine and 5-HT levels measured by microdialysis and formalin-induced pain. Activation of 5-HT(1A) receptors was confirmed by antagonism with WAY100635.

KEY RESULTS

Xaliproden exhibited high affinity for rat (r) and human (h) 5-HT(1A) receptors (pK(i)= 8.84 and 9.00). In [(35)S]GTPgammaS (guanosine 5'-O-(3-[(35)S]thio)triphosphate) assays it activated both hippocampal r5-HT(1A)[pEC(50)/E(MAX) of 7.58/61% (%5-HT)] and recombinant h5-HT(1A) receptors (glioma C6-h5-HT(1A): 7.39/62%; HeLa-h5-HT(1A): 7.24/93%). In functional [(35)S]GTPgammaS autoradiography, xaliproden induced labelling in structures enriched with 5-HT(1A) receptors (hippocampus, lateral septum, prefrontal and entorhinal cortices). Xaliproden inhibited in vivo binding of [(3)H]WAY100635 to 5-HT(1A) receptors in mouse frontal cortex and hippocampus (ID(50): 3.5 and 3.3 mg x kg(-1), p.o. respectively). In rat, it increased extracellular dopamine levels in frontal cortex and reduced hippocampal 5-HT levels (ED(50): 1.2 and 0.7 mg x kg(-1), i.p. respectively). In a rat pain model, xaliproden inhibited paw licking and elevation (ED(50): 1 and 3 mg x kg(-1), i.p. respectively) following formalin injection in the paw. All effects were reversed by pretreatment with WAY100635.

CONCLUSIONS AND IMPLICATIONS

These results indicate that activation of 5-HT(1A) receptors is the principal mechanism of action of xaliproden and provide further support for the utility of 5-HT(1A) receptor activation as an anti-nociceptive strategy.