Browse by Audience
Metabotropic glutamate receptor 5 (mGlu5) has been shown to modulate nociception in animals, but no mGlu5 antagonists have been developed commercially as analgesics. The mGlu5 antagonist fenobam [N-(3-chlorophenyl)-N'-(4,5-dihydro-1-methyl-4-oxo-1H-imidazole-2-yl)urea] was originally evaluated for development as a non-benzodiazepine anxiolytic. Fenobam is analgesic in numerous mouse pain models, acting exclusively via mGlu5 blockade. Furthermore, fenobam showed no signs of analgesic tolerance with up to two weeks of daily dosing in mice. Analgesic effects of fenobam in humans have not been reported. The purpose of this investigation was to evaluate fenobam pharmacokinetics and analgesic effects in humans. We first evaluated single-dose oral fenobam disposition in a parallel-group dose-escalation study in healthy volunteers. A second investigation tested the analgesic effects of fenobam in an established experimental human pain model of cutaneous sensitization utilizing capsaicin cream and heat, in a double-blind placebo-controlled study. The primary outcome measure was the area of hyperalgesia and allodynia around the area applied with heat/capsaicin. Secondary outcome measures included nociception, measured as pain rating on a visual analog scale, heat-pain detection threshold, and effects on cognition and mood. Fenobam plasma exposures showed considerable inter-individual variability, and were not linear with dose. Fenobam reduced sensitization vs placebo at a single time-point (peak plasma concentration); we found no other difference between fenobam and placebo. Our results suggest highly variable fenobam disposition, and minimal analgesic effects at the dose tested. We suggest that future studies testing analgesic effects of mGlu5 blockade are warranted, but such studies should employ molecules with improved pharmacokinetic profiles.
Learn More >To evaluate the anti-inflammatory and analgesic effect of sepiapterin reductase (SPR) inhibition in a mouse model of inflammatory joint disease and to evaluate sepiapterin as a non-invasive, translational biomarker of SPR inhibition/target engagement in mice and healthy human volunteers.
Learn More >Vixotrigine is a voltage- and use-dependent Nav1.7 channel blocker under investigation for the treatment of peripheral neuropathic pain conditions, including trigeminal neuralgia. Vixotrigine is metabolized primarily via uridine diphosphate-glucuronosyltransferases (UGTs). Carbamazepine, a UGT and cytochrome P450 3A4 inducer, is a first-line treatment for trigeminal neuralgia. We conducted a double-blind, randomized, placebo-controlled, parallel-group, single-center phase 1 study to investigate the impact of coadministering vixotrigine and carbamazepine on their respective pharmacokinetics (PK) in healthy volunteers, the safety and tolerability of combined treatment, and PK recovery of vixotrigine following carbamazepine discontinuation. Randomly assigned treatments were carbamazepine (100 mg twice a day, days 1-3 and 200 mg twice a day, days 4-21) or placebo on days 1 to 21. All volunteers received vixotrigine 150 mg 3 times a day on days 16 to 28. At prespecified times, whole-blood samples were collected for PK assessment. Statistical analyses were performed on the log-transformed PK parameters area under the concentration-time curve within a dosing interval (AUC ) and maximum observed concentration (C ) for vixotrigine, carbamazepine, and metabolites. Vixotrigine AUC and C were reduced by 31.6% and 26.3%, respectively, when coadministered with carbamazepine compared with placebo. Seven days after carbamazepine discontinuation, vixotrigine AUC and C remained 24.5% and 21.4% lower compared with placebo. Carbamazepine AUC and C were <10% lower when coadministered with vixotrigine compared on days 15 and 21. Vixotrigine/carbamazepine coadministration was well tolerated. These results suggest that vixotrigine does not have an effect on carbamazepine PK, and although carbamazepine has an effect on the exposure of vixotrigine, the effect is not considered clinically relevant.
Learn More >The potential use of cannabis and cannabinoid products for the treatment of low-back pain is an important area for investigation. As one of the leading reasons to visit a primary care provider, low-back pain results in a significant burden of disease in both the United States' economic and health care systems. Given the current opioid epidemic, it is important to seek novel analgesics and understand their efficacy for myriad pain conditions, including low-back pain. A systematic review was performed using multiple online databases to assess the association of cannabis use and low-back pain in the literature. A total of 124 articles were produced via our search methods, 73 abstracts in total were screened, 16 articles underwent full-text review, and 6 articles were included in qualitative synthesis. This systematic literature review reveals a lack of primary research investigating cannabis as a potential treatment of low-back pain and highlights the need for further investigation with well-designed clinical trials. There remain substantial political and legal barriers to performing such research. Although there is a considerable body of work on the usage of cannabinoid products for many medical conditions, including the treatment of chronic pain, more directed clinical research into their utility as an analgesic for low-back pain and related symptoms needs to be addressed.
Learn More >Numerous inflammatory skin disorders display a high prevalence of itch. The Mas-related G protein coupled receptor X2 (MRGPRX2) has been shown to modulate itch by inducing non-IgE-mediated mast cell degranulation and the release of endogenous inducers of pruritus. Various substances collectively known as basic secretagogues, which include inflammatory peptides and certain drugs, can trigger MRGPRX2 and thereby induce pseudo-allergic reactions characterized by histamine and protease release as well as inflammation. Here, we investigated the capacity of an immunomodulatory single-stranded oligonucleotide (ssON) to modulate IgE-independent mast cell degranulation and, more specifically, its ability to inhibit the basic secretagogues compound 48/80 (C48/80)-and LL-37 and . We examined the effect of ssON on MRGPRX2 activation by measuring degranulation in a human mast cell line (LAD2) and calcium influx in MRGPRX2-transfected HEK293 cells. To determine the effect of ssON on itch, we performed behavioral studies in established mouse models and collected skin biopsies for histological analysis. Additionally, with the use of a rosacea mouse model and RT-qPCR, we investigated the effect on ssON on LL-37-induced inflammation. We reveal that both mast cell degranulation and calcium influx in MRGPRX2 transfected HEK293 cells, induced by the antimicrobial peptide LL-37 and the basic secretagogue C48/80, are effectively inhibited by ssON in a dose-dependent manner. Further, ssON demonstrates a capability to inhibit LL-37 and C48/80 activation in two mouse models. We show that intradermal injection of ssON in mice is able to block itch induced via C48/80 in a dose-dependent manner. Histological staining revealed that ssON inhibits acute mast cell degranulation in murine skin treated with C48/80. Lastly, we show that ssON treatment ameliorates LL-37-induced inflammation in a rosacea mouse model. Since there is a need for new therapeutics targeting non-IgE-mediated activation of mast cells, ssON could be used as a prospective drug candidate to resolve itch and inflammation in certain dermatoses.
Learn More >To evaluate the crossover design in migraine preventive treatment trials by assessing dropout rate, and potential period and carryover effect in four placebo-controlled randomized controlled trials (RCTs).
Learn More >Effective and safe analgesics represent an unmet medical need for the treatment of acute and chronic pain. A series of N-cyclopropylmethyl-7α-phenyl-6,14-endoethano-tetrahydronorthebaines were designed, synthesized and assayed, leading to the discovery of a benzylamine derivative (compound 4, SLL-039) as a highly selective and potent κ opioid agonist (κ, Ki=0.47 nM, κ/μ=682, κ/δ=283), which was confirmed by functional assays in vitro and antinociceptive assays in vivo. The in vivo effect could be blocked by pretreatment with the selective κ antagonist nor-BNI. Moreover, this compound did not induce sedation, a common dose limiting effect of κ opioid receptor agonists, at its analgesic dose compared to U50,488H. The dissociation of sedation/antinociception found in SLL-039 was assumed to be correlated with the occupation of its benzamide motif in a unique subsite involving V1182.63, W124EL1 and E209EL2.
Learn More >The development of opioid-induced analgesic tolerance is a clinical challenge in long-term use for managing chronic pain. The mechanisms of morphine tolerance are poorly understood. Mitochondria-derived reactive oxygen species (ROS) is a crucial signal inducing analgesic tolerance and pain. Chronic administration of morphine leads to robust ROS production and accumulation of damaged mitochondria, which are immediately removed by mitophagy. Here, we show that morphine inhibits mitochondria damage-induced accumulation of PTEN-induced putative kinase 1 (PINK1) in neurons. It interrupts the recruitment of Parkin to the impaired mitochondria and inhibits the ubiquitination of mitochondrial proteins catalyzed by Parkin. Consequently, morphine suppresses the recognition of autophagosomes to the damaged mitochondria mediated by LC3 and SQSTM1/p62 (sequestosome-1). Thus, morphine inhibits autophagy flux and leads to the accumulation of SQSTM1/p62. Finally, the impaired mitochondria cannot be delivered to lysosomes for degradation and ultimately induces robust ROS production and morphine tolerance. Our findings suggest that the dysfunction of mitophagy is involved in morphine tolerance. The deficiency of PINK1/Parkin-mediated clearance of damaged mitochondria is crucial for the generation of excessive ROS and important to the development of analgesic tolerance. These findings suggest that the compounds capable of stabilizing PINK1 or restoring mitophagy may be utilized to prevent or reduce opioid tolerance during chronic pain management.
Learn More >Although the tricyclic antidepressant amitriptyline (ATL) is widely used in the clinic, the mechanism underlying its high therapeutic efficacy against neuropathic pain remains unclear. NMDA receptors (NMDARs) represent a target for ATL and are involved in sensitization of neuropathic pain. Here we describe two actions of ATL on NMDARs: 1) enhancement of Ca-dependent desensitization and 2) trapping channel block. Inhibition of NMDARs by ATL was found to be dependent upon external Ca concentration ([Ca]) in a voltage-independent manner, with an IC of 0.72 μM in 4 mM [Ca]. The ATL IC value increased exponentially with decreasing [Ca], with an e-fold change observed per 0.69 mM decrease in [Ca]. Loading neurons with BAPTA abolished Ca-dependent inhibition, suggesting that Ca affects NMDARs from the cytosol. Since there is one known Ca-dependent process in gating of NMDARs, we conclude that ATL most likely promotes Ca-dependent desensitization. We also found ATL to be a trapping open-channel blocker of NMDARs with an IC of 220 µM at 0 mV. An e-fold change in ATL IC was observed to occur with a voltage shift of 50 mV in 0.25 mM [Ca]. Thus, we disclose here a robust dependence of ATL potency on extracellular [Ca], and demonstrate that ATL bound in the NMDAR pore can be trapped by closure of the channel.
Learn More >