Safety, Tolerability, and Pharmacokinetic Characteristics of a Novel Nonopioid Analgesic, VVZ-149 Injections in Healthy Volunteers: A First-in-Class, First-in-Human Study.

VVZ-149, a dual antagonist of GlyT2 and 5HT2 A receptors, is an investigational analgesic with a novel mechanism of action that is currently under early-stage clinical development as an injectable agent for the treatment of postoperative pain. Here, the safety, tolerability, and pharmacokinetics of VVZ-149 injections in healthy male volunteers were explored in a randomized, double-blind, single- and multiple-ascending-dose (SAD and MAD, respectively), placebo-controlled clinical study. Subjects randomly received a 4-hour intravenous infusion of 0.25-8 mg/kg VVZ-149 or placebo in the SAD study (n = 46) or a 4-hour intravenous infusion of 4-7 mg/kg VVZ-149 or placebo twice daily for 3 days in the MAD study (n = 20). Serial blood and urine samples were collected for the pharmacokinetic analysis of VVZ-149 and its active metabolite (VVZ-368). Noncompartmental and compartmental pharmacokinetic analyses were performed. Various dosing scenarios were simulated to identify the adequate dosing regimen for the subsequent trials. Plasma exposure to VVZ-149 and VVZ-368 showed a dose-proportional increase. VVZ-149 did not accumulate in the plasma, whereas the plasma concentration of VVZ-368 increased by 1.23- to 2.49-fold after the fifth and sixth doses, respectively, in the MAD trial. Among the simulated dosing regimens, a loading dose followed by a maintenance dose was found to be an optimal dosing regimen, yielding the effective concentration estimated from animal studies in rat models of neuropathic or inflammatory pain. Single- or multiple-dose administration of VVZ-149 was generally well tolerated. These results showed that 0.5-8 mg/kg VVZ-149 exhibited linear pharmacokinetic characteristics and can be safely administered in further clinical studies.

Randomised, double-blind, parallel group, placebo-controlled study to evaluate the analgesic efficacy and safety of VVZ-149 injections for postoperative pain following laparoscopic colorectal surgery.

INTRODUCTION: In spite of advances in understanding and technology, postoperative pain remains poorly treated for a significant number of patients. In colorectal surgery, the need for developing novel analgesics is especially important. Patients after bowel surgery are assessed for rapid return of bowel function and opioids worsen ileus, nausea and constipation. We describe a prospective, double-blind, parallel group, placebo-controlled randomised controlled trial testing the hypothesis that a novel analgesic drug, VVZ -149, is safe and effective in improving pain compared with providing opioid analgesia alone among adults undergoing laparoscopic colorectal surgery. METHODS AND ANALYSIS: Based on sample size calculations for primary outcome, we plan to enrol 120 participants. Adult patients without significant medical comorbidities or ongoing opioid use and who are undergoing laparoscopic colorectal surgery will be enrolled. Participants are randomly assigned to receive either VVZ-149 with intravenous (IV) hydromorphone patient-controlled analgesia (PCA) or the control intervention (IV PCA alone) in the postoperative period. The primary outcome is the Sum of Pain Intensity Difference over 8 hours (SPID-8 postdose). Participants receive VVZ-149 for 8 hours postoperatively to the primary study end point, after which they continue to be assessed for up to 24 hours. We measure opioid consumption, record pain intensity and pain relief, and evaluate the number of rescue doses and requests for opioid. To assess safety, we record sedation, nausea and vomiting, respiratory depression, laboratory tests and ECG readings after study drug administration. We evaluate for possible confounders of analgesic response, such as anxiety, depression and catastrophising behaviours. The study will also collect blood sample data and evaluate for pharmacokinetic and pharmacodynamic relationships. ETHICS AND DISSEMINATION: Ethical approval of the study protocol has been obtained from Institutional Review Boards at the participating institutions. Trial results will be disseminated through scientific conference presentations and by publication in scientific journals. TRIAL REGISTRATION NUMBER: NCT02489526; pre-results.

A series of case studies: practical methodology for identifying antinociceptive multi-target drugs.

Since the introduction of drug discovery based on single targets, the number of newly developed drugs has steadily declined, and the reliablility of the current drug-discovery paradigm has been unceasingly questioned. As an alternative, an emerging approach pursuing multi-targeting drugs has arisen to reflect multifactorial diseases caused by the complex networks of various mechanisms. The purpose of this paper is to review multi-target drugs and introduce our progress in establishing a practical methodology for identifying antinociceptive multi-target drugs. We have adopted a system of ex vivo efficacy screening using long-term potentiation in rat spinal cord as a surrogate biomarker for neuropathic pain. A bait-target approach is also adopted to lure an unknown target combination that induces synergistic mechanisms.

Hyperpolarization-activated, cation-nonselective, cyclic nucleotide-modulated channel blockade alleviates mechanical allodynia and suppresses ectopic discharge in spinal nerve ligated rats.

UNLABELLED: Abnormal spontaneous firing is well described in axotomized sensory neurons and likely contributes to nerve injury-induced pain. The hyperpolarization-activated current I(h) initiates spontaneous, rhythmic depolarization in the sinoatrial node and central neurons. This study was undertaken to investigate the possible contribution of I(h) to primary afferent ectopic discharge and pain behavior in nerve-injured rats. Nerve injury was produced by tight ligation of lumbar spinal nerves (L5/6). Two weeks later, rats showed marked mechanical allodynia. Withdrawal thresholds were measured before and after administration of saline or the specific I(h) antagonist ZD7288 (1, 3, or 10 mg/kg, intraperitoneally). ZD7288 dose-dependently reversed mechanical allodynia. In a second experiment, we performed both in vivo and in vitro extracellular single unit recordings from teased dorsal root fascicles. Intravenous infusion (2.5 or 5 mg/kg) of ZD7288 during a period of 10 minutes significantly blocked ectopic discharges in vivo. Perfusion (25 to 100 mumol/L) of ZD7288 for 5 minutes in vitro almost completely blocked ectopic discharges from large myelinated fibers (Abeta) while partially suppressing ectopic discharge from thinly myelinated fibers (Adelta). We conclude from these data that in axotomized sensory neurons, a ZD7288-sensitive current contributes to spontaneous discharges in myelinated fibers. Thus, I(h) might substantially contribute to the pathophysiology of nerve injury-related neuropathic pain. PERSPECTIVE: The current study investigated the mechanism of abnormal spontaneous discharges (ectopic discharges) from axotomized sensory afferents. Ectopic discharges are a main driving source of nerve injury-induced neuropathic pain. Understanding the mechanism of ectopic discharges and identifying how to control them will be useful toward developing new therapies.

Experiments with nitric oxide synthase inhibitors in spinal nerve ligated rats provide no evidence of a role for nitric oxide in neuropathic mechanical allodynia.

We have investigated the effect of treatment with N(omega)-nitro-l-arginine methylester (l-NAME), a non-selective nitric oxide synthase inhibitor (NOS), both before and after the induction of mechanical allodynia by tight ligation of the left L5 and L6 spinal nerves in rats (SNL rats). The degree of mechanical allodynia was measured by tactile threshold for paw flinching with von Frey filaments. Intraperitoneal (i.p.) administration of l-NAME (3-30 mg/kg) 1 week after the spinal nerve ligation produced a dose-dependent reduction of the behavioral signs of mechanical allodynia, but the effect was not reversed by pretreatment with l-arginine (300 mg/kg). N(omega)-Nitro-l-arginine (l-NNA, i.p., 30 mg/kg), aminoguanidine (AG, i.p., 30 mg/kg) and a potent neuronal NOS inhibitor (LY457963, i.p., 30 mg/kg) did not reduce mechanical sensitivity in the SNL rats. Furthermore, using an ex vivo NOS activity assay, l-NAME partially inhibited the spinal NOS activity, whereas LY457963 almost completely inhibited the spinal NOS activity. Prior administration of l-NAME (i.p., 30 mg/kg) or of MK-801 (0.5 mg/kg), an NMDA antagonist, 30 min before the spinal nerve ligation significantly prevented the development of mechanical allodynia after spinal nerve ligation for an extended period of time. High doses of l-arginine (100 mg/kg or 300 mg/kg, i.p.), however, did not reverse the preemptive effect of l-NAME. These results suggest that neither the anti-allodynic nor the preemptive effects of l-NAME are mediated by NOS inhibition.

Identification and biological evaluation of 4-(3-trifluoromethylpyridin-2-yl)piperazine-1-carboxylic acid (5-trifluoromethylpyridin-2-yl)amide, a high affinity TRPV1 (VR1) vanilloid receptor antagonist.

High throughput screening using the recombinant human TRPV1 receptor was used to identify a series of pyridinylpiperazine ureas (3) as TRPV1 vanilloid receptor ligands. Exploration of the structure-activity relationships by parallel synthesis identified the essential pharmacophoric elements for antagonism that permitted further optimization via targeted synthesis to provide a potent orally bioavailable and selective TRPV1 modulator 41 active in several in vivo models.

The role of uninjured nerve in spinal nerve ligated rats points to an improved animal model of neuropathic pain.

L5 and L6 spinal nerve ligation (SNL) in rats leads to behavioral signs of neuropathic pain including mechanical allodynia. The purposes of this study were to investigate the role of the intact L4 spinal nerve in the development of mechanical allodynia following L5 and L6 SNL and, as a result, to develop a modified model of neuropathic pain. As a first set of experiments, in addition to tight ligation of the left L5 and L6 spinal nerves, the intact L4 spinal nerve was manipulated either (1) by gentle repeated stretching of the L4 spinal nerve immediately after L5 and L6 SNL or (2) by intermittent mechanical stimulation to the ipsilateral paw during the first week after SNL. Tactile sensitivity was measured by determining the foot withdrawal threshold before and after SNL. Mild irritation of L4 spinal nerve and application of mechanical stimuli to the ipsilateral paw significantly increased the development of mechanical allodynia after SNL. In a second set of experiments, SNL was produced by tightly ligating only the left L5 spinal nerve with or without a loop of 5-0 chromic gut placed loosely around the L4 spinal nerve. This additional L4 loop significantly increased long-lasting tactile sensitivity compared to L5 SNL alone. These results suggest that afferent activity of the intact L4 spinal nerve aids in the development of mechanical allodynia in the SNL model of neuropathic pain. The addition of a chromic gut loop around the intact L4 spinal nerve can augment the development of mechanical allodynia following SNL of L5. We propose this latter as a useful and practical animal model of neuropathic pain.

Increased sensitivity of injured and adjacent uninjured rat primary sensory neurons to exogenous tumor necrosis factor-alpha after spinal nerve ligation.

Tumor necrosis factor-alpha (TNF) is upregulated after nerve injury, causes pain on injection, and its blockade reduces pain behavior resulting from nerve injury; thus it is strongly implicated in neuropathic pain. We investigated responses of intact and nerve-injured dorsal root ganglia (DRG) neurons to locally applied TNF using parallel in vivo and in vitro paradigms. In vivo, TNF (0.1-10 pg/ml) or vehicle was injected into L5 DRG in naive rats and in rats that had received L5 and L6 spinal nerve ligation (SNL) immediately before injection. In naive rats, TNF, but not vehicle, elicited long-lasting allodynia. In SNL rats, subthreshold doses of TNF synergized with nerve injury to elicit faster onset of allodynia and spontaneous pain behavior. Tactile allodynia was present in both injured and adjacent uninjured (L4) dermatomes. Preemptive treatment with the TNF antagonist etanercept reduced SNL-induced allodynia by almost 50%. In vitro, the electrophysiological responses of naive, SNL-injured, or adjacent uninjured DRG to TNF (0.1-1000 pg/ml) were assessed by single-fiber recordings of teased dorsal root microfilaments. In vitro perfusion of TNF (100-1000 pg/ml) to naive DRG evoked short-lasting neuronal discharges. In injured DRG, TNF, at much lower concentrations, elicited earlier onset, markedly higher, and longer-lasting discharges. TNF concentrations that were subthreshold in naive DRG also elicited high-frequency discharges when applied to uninjured, adjacent DRG. We conclude that injured and adjacent uninjured DRG neurons are sensitized to TNF after SNL. Sensitization to endogenous TNF may be essential for the development and maintenance of neuropathic pain.