Befiradol (NLX-112)

NLX-112, a highly selective 5-HT1A receptor biased agonist, does not exhibit misuse potential in male rats or macaques

NLX-112 (a.k.a. F13640 or befiradol) exhibits nanomolar affinity, exceptional selectivity and biased agonism at serotonin 5-HT1A receptors. NLX-112 displays robust analgesic activity in a number of rodent models of pain, and is currently developed as a treatment for l-DOPA-induced dyskinesia (LID) in Parkinson's disease (PD) patients. Noteworthy, PD patients can suffer from comorbid chronic pain, thus necessitating the use of analgesic drugs, such as opioids, which have potential for misuse. Additionally, dopamine agonists used to treat PD can produce cocaine-like effects in preclinical assays of misuse potential. The present study investigated whether NLX-112 possesses misuse potential of its own using two behavioural assays routinely used for this purpose: intracranial self-stimulation (ICSS) in rats, and cocaine discrimination in macaque monkeys. In rats, low doses of NLX-112 (0.03 and 0.1 mg/kg p.o.) did not alter ICSS frequency-rate curves, while higher doses (0.3 and 1.0 mg/kg) shifted the curve to the right and flattened it, i.e., reduced ICSS. As expected, cocaine (10 mg/kg i.p.) shifted the curve to the left, i.e., facilitated ICSS, but NLX-112 (0.03 and 0.1 mg/kg p.o.) did not further enhance cocaine-induced facilitation of ICSS. In monkeys trained to discriminate cocaine (0.4 mg/kg i.m.) from saline, NLX-112 (0.01-0.1 mg/kg p.o.) did not substitute for cocaine. Taken together, these results suggest that NLX-112, at doses displaying anti-dyskinetic activity in rat, marmoset and macaque models of LID, is free from misuse potential. From a translational perspective, this is a desirable property for a compound destined to be used in PD patients, who can suffer from comorbid chronic pain necessitating the use of potentially misused analgesic drugs.

The selective 5-HT1A receptor agonist NLX-112 displays anxiolytic-like activity in mice

Anxiety is amongst the commonest neuropsychiatric disorders, and there is a large body of evidence to suggest that abnormalities in serotonergic function are involved in its pathogenesis. Several studies have implicated 5-HT_1A receptor activation in mitigating anxiety disorders, so this study investigated the acute effects of a highly selective, potent and efficacious 5-HT_1A receptor full agonist, NLX-112 (a.k.a. befiradol, F13640), in middle-aged C57bl/6 J male mice. Video tracking was used to measure several parameters including time spent in the open and closed arms of an elevated plus maze (EPM), distance travelled and thigmotaxis in an open field test (OFT). At 0.1 to 1.0 mg/kg s.c., NLX-112 markedly decreased thigmotaxis and increased exploratory behaviour in the OFT and EPM assays. Hence, at 0.3 mg/kg, NLX-112 augmented locomotor activity in the centre of an open field arena by 164% and increased the time spent in the open arms of the EPM by 119% of control. These results indicate that anxiety-like behaviours in mice are significantly diminished with low doses of NLX-112. NLX-112 may therefore possess anxiolytic properties which complement its known activity in models of movement disorders.

NLX-112, a highly selective 5-HT1A receptor agonist, mediates analgesia and antidepressant-like activity in rats via spinal cord and prefrontal cortex 5-HT1A receptors, respectively

NLX-112 (a.k.a. F13640 or befiradol) possesses marked activity in a variety of animal models of pain and of neuropsychiatric disorders; it exhibits nanomolar affinity, exceptional selectivity and high agonist efficacy at 5-hydroxytryptamine1A (5-HT_1A) receptors. Although NLX-112 has been shown to activate 5-HT_1A postsynaptic heteroreceptors in the prefrontal cortex (PFC), a brain region involved in the control of depressive states, the influence of NLX-112 on spinal cord 5-HT_1A receptors (implicated in the control of pain) has not been described. Here we report on the ability, in rats, of NLX-112 to elicit analgesia in the intraplantar formalin model of nociceptive pain following intrathecal (i.t.) administration, and its ability to produce antidepressant-like activity in the forced swim test (FST) following in situ PFC microinjection. NLX-112, injected i.t. (L5-L6 region) induced analgesic effects in the formalin model of tonic nociceptive pain. At 20 ?g, it almost abolished the effect of formalin on both the paw licking and paw elevation measures, and in both the early (0-5 min after formalin administration, reflecting acute pain) and the late (22.5-27.5 min, reflecting inflammatory pain) phases. The effects of NLX-112 (20 ?g i.t.) were reversed by co-administration of 20 ?g i.t. of the 5-HT_1A receptor antagonist, WAY100635. Furthermore, the analgesic effects of systemically administered NLX-112 (0.63 mg/kg i.p.) were reversed by i.t. administration of WAY100635 (20 ?g), most notably on paw licking. Finally, microinjection of NLX-112, bilaterally in the PFC, dose-dependently (MED 4 ?g) and markedly reduced immobility in the FST (circa 90% reduction at 32 ?g). In conclusion, the present data demonstrate that activation of spinal cord-located 5-HT_1A receptors is sufficient for NLX-112 to mediate its analgesic effects in a rat model of tonic nociceptive pain. The data also highlight the involvement of PFC 5-HT_1A receptors in the antidepressant-like activity of NLX-112 in the FST. Overall, the study suggests that highly selective and high efficacy 5-HT_1A receptors agonists, such as NLX-112, could be useful to treat painful conditions associated with depressive states, through activation of different sub-populations of 5-HT_1A receptors.

NLX-112, a novel 5-HT1A receptor agonist for the treatment of L-DOPA-induced dyskinesia: Behavioral and neurochemical profile in rat

L-DOPA is the gold-standard treatment for Parkinson's disease (PD), but induces troublesome dyskinesia after prolonged treatment. This is associated with the 'false neurotransmitter' conversion of L-DOPA to dopamine by serotonin neurons projecting from the raphe to the dorsal striatum. Reducing their activity by targeting pre-synaptic 5-HT1A receptors should thus be an attractive therapeutic strategy, but previous 5-HT1A agonists have yielded disappointing results. Here, we describe the activity of a novel, highly selective and potent 5-HT1A agonist, NLX-112 (also known as befiradol or F13640) in rat models relevant to PD and its associated affective disorders. NLX-112 (0.16 mg/kg, i.p.) potently and completely reversed haloperidol-induced catalepsy in intact rats and abolished L-DOPA-induced Abnormal Involuntary Movements (AIMs) in hemiparkinsonian rats, an effect that was reversed by the selective 5-HT1A antagonist, WAY100635. In microdialysis experiments, NLX-112 profoundly decreased striatal 5-HT extracellular levels, indicative of inhibition of serotonergic function. NLX-112 also blunted the L-DOPA-induced surge in dopamine levels on the lesioned side of the brain, an action that likely underlies its anti-dyskinetic effects. NLX-112 (0.16 mg/kg, i.p.) robustly induced rotations in hemiparkinsonian rats, suggesting that it has a motor facilitatory effect. Rotations were abolished by WAY100635 and were ipsilateral to the lesioned side, suggesting a predominant stimulation of the dopamine system on the non-lesioned side of the brain. NLX-112 also efficaciously reduced immobility time in the forced swim test (75% reduction at 0.16 mg/kg, i.p.) and eliminated stress-induced ultrasonic vocalization at 0.08 mg/kg, i.p., effects consistent with potential antidepressant- and anxiolytic-like properties. In other tests, NLX-112 (0.01-0.16 mg/kg, i.p.) did not impair the ability of L-DOPA to rescue forepaw akinesia in the cylinder test but decreased rotarod performance, probably due to induction of flat body posture and forepaw treading which are typical of 5-HT1A agonists upon acute administration. However, upon repeated administration of NLX-112 (0.63 mg/kg, i.p., twice a day), flat body posture and forepaw treading subsided within 4 days of treatment. Taken together, these observations suggest that NLX-112 could exhibit a novel therapeutic profile, combining robust anti-dyskinetic properties without impairing the therapeutic properties of L-DOPA, and with additional beneficial effects on non-motor (affective) symptoms.

NLX-112, a highly selective 5-HT1A receptor agonist: Effects on body temperature and plasma corticosterone levels in rats

NLX-112 (a.k.a. F13640 or befiradol), exhibits nanomolar affinity, exceptional selectivity and high agonist efficacy at 5-hydroxytryptamine 5-HT_1A receptors. It possesses marked activity in a variety of animal models of depression, pain and L-DOPA-induced dyskinesia. However, its influence on translational biomarkers of central 5-HT_1A receptor activation has not been previously described. Here, we report on the activity, in rats, of NLX-112 to increase plasma corticosterone levels and produce hypothermia, two responses which are also elicited by 5-HT_1A receptor agonists in humans. NLX-112 elicited dose-dependent hypothermia (minimal effective dose, MED: 0.31mg/kg p.o.) and also increased plasma corticosterone both by oral and intraperitoneal routes (MED: 0.63mg/kg in both cases). The increase in corticosterone induced by NLX-112 (0.63mg/kg p.o.) was abolished by co-administration of the selective 5-HT_1A receptor antagonist, WAY100635. Additionally, NLX-112 also dose-dependently induced flat body posture, forepaw treading and lower lip retraction (MEDs 0.31-0.63mg/kg p.o.). The doses of NLX-112 which induce hypothermia or corticosterone release were similar to those inducing serotonergic behaviors but greater than those reported previously in models of therapeutic-like activity (range 0.04 to 0.16mg/kg). Overall, the present study provides information for clinical dose estimations of NLX-112 and suggests that therapeutic effects may occur at doses below those at which biomarker responses are observed.