Calcitonin gene-related peptide (CGRP) receptor antagonists in the treatment of migraine

Bimodal functions of calcitonin gene-related peptide in the brain

AIMS

Calcitonin gene-related peptide (CGRP) is a pluripotent neuropeptide crucial for maintaining vascular homeostasis, yet its full therapeutic potential remains incompletely exploited. Within the brain, CGRP demonstrates a distinct bimodal effect, contributing to neuroprotection in ischemic conditions while inducing neuronal sensitization and inflammation in non-ischemic settings. Despite extensive research on CGRP, the absence of a definitive determinant for this observed dichotomy has limited its potential for therapeutic applications in the brain. This review examines the effects of CGRP in both physiological and pathological conditions, aiming to identify a unifying factor that could enhance its therapeutic applicability.

MATERIALS AND METHODS

This comprehensive literature review analyzes the molecular pathways associated with CGRP and the specific cellular responses observed in these contexts. Additionally, the review investigates the psychological implications of CGRP in relation to cerebral perfusion levels, aiming to elucidate its underlying factors.

KEY FINDINGS

Reviewing the literature reveals that, elevated levels of CGRP in non-ischemic conditions exert detrimental effects on brain function, while they confer protective effects in the context of ischemia. These encompass anti-oxidative, anti-inflammatory, anti-apoptotic, and angiogenic properties, along with behavioral normalization. Current findings indicate promising therapeutic avenues for CGRP beyond the acute phases of cerebral injury, extending to neurodegenerative and psychological disorders associated with cerebral hypoperfusion, as well as chronic recovery following acute cerebral injuries.

SIGNIFICANCE

Improved understanding of CGRP's bimodal properties, alongside advancements in CGRP delivery methodologies and brain ischemia detection technologies, paves the way for realizing its untapped potential and broad therapeutic benefits in diverse pathological conditions.

Intranasal administration of recombinant human BDNF as a potential therapy for some primary headaches

BACKGROUND

In addition to its critical role in neurogenesis, brain-derived neurotrophic factor (BDNF) modulates pain and depressive behaviors.

METHODS

In a translational perspective, we tested the anti-migraine activity of highly purified and characterized recombinant human BDNF (rhBDNF) in an animal model of cephalic pain based on the chronic and intermittent NTG administration (five total injections over nine days), used to mimic recurrence of attacks over a given period. To achieve this, we assessed the effects of two doses of rhBDNF (40 and 80 µg/kg) administered intranasally to adult male Sprague-Dawley rats, on trigeminal hyperalgesia (by orofacial formalin test), gene expression (by rt-PCR) of neuropeptides and inflammatory cytokines in specific areas of the brain related to migraine pain. Serum levels of CGRP, PACAP, and VIP (by ELISA) were also evaluated. The effects of rhBDNF were compared with those of sumatriptan (5 mg/kg i.p), administered 1 h before the last NTG administration.

RESULTS

Both doses of rhBDNF significantly reduced NTG-induced nocifensive behavior in Phase II of the orofacial formalin test. The anti-hyperalgesic effect of intranasal high-dose rhBDNF administration in the NTG-treated animals was associated with a significant modulation of mRNA levels of neuropeptides (CGRP, PACAP, VIP) and cytokines (IL-1beta, IL-10) in the trigeminal ganglion, medulla-pons, and hypothalamic area. Of note, the effects of rhBNDF treatment were comparable to those induced by the administration of sumatriptan. rhBDNF administration at both doses significantly reduced serum levels of PACAP, while the higher dose also significantly reduced serum levels of VIP.

CONCLUSIONS

The findings suggest that intranasal rhBDNF has the potential to be a safe, non-invasive and effective therapeutic approach for the treatment of primary headache, particularly migraine.

Reporting Quality and Risk of Bias Analysis of Published RCTs Assessing Anti-CGRP Monoclonal Antibodies in Migraine Prophylaxis: A Systematic Review

Objective: Phase II/III randomized clinical trials (RCTs) are vulnerable to many types of bias beyond randomization. Insights into the reporting quality of RCTs involving migraine patients treated with monoclonal antibodies targeting the calcitonin gene-related peptide system (anti-CGRP MAbs) are currently lacking. Our aim was to analyze the reporting quality of phase II/III RCTs involving migraine patients treated with anti-CGRP MAbs. Methods: A systematic search was performed on the PubMed and EMBASE databases, according to PRISMA guidelines, for relevant RCTs in either episodic or chronic migraine prevention. Additionally, an adapted version of the 2010 CONSORT statement checklist was utilized. The ROBvis online tool was used to document the risk of bias. Results: From the initially identified 179 articles, we finally found 31 RCTs that were eligible for evaluation. The average CONSORT compliance was 88.7% (69.7-100%), while 93.5% (N = 29) of the articles had a compliance greater than 75%. Twenty-eight CONSORT items were reported in more than 75% of the articles. The average compliance of the analyzed RCTs was 93.9% for Galcanezumab, 91.3% for Fremanezumab, followed by 85.4% for Erenumab and Eptinezumab studies. Implementation of the ROB2 tool showed some concerning "missing information" arising from the inadequate reporting. Specifically, 50% of the studies (N = 16) were categorized as having inadequate information regarding the randomization process. Conclusions: Adequate reporting quality was disclosed in the evaluated RCTs with anti-CGRP MAbs in migraine prevention. However, some methodological issues need to be highlighted to be addressed in future studies assessing the efficacy of new molecules targeting CGRP or other candidate pathways implicated in migraine pathophysiology.

Neuropeptide stimulation of physiological and immunological responses in precision-cut lung slices

Organotypic lung slices, sometimes known as precision-cut lung slices (PCLS), provide an environment in which numerous cell types and interactions can be maintained outside the body (ex vivo). PCLS were maintained ex vivo for up to a week and demonstrated health via the presence of neurons, maintenance of tissue morphology, synthesis of mucopolysaccharides, and minimal cell death. Multiple phenotypes of neuronal fibers were present in lung slices with varied size, caliber, and neurotransmitter immunoreactivity. Of the neuropeptides present in fibers, calcitonin gene-related peptide (CGRP) was the most prevalent. Exposing PCLS to recombinant CGRP resulted in the proliferation and dispersion of CD19+ B cells in slices taken selectively from females. The number of granules containing immunoreactive (ir) surfactant protein C (SPC), which are representative of alveolar type 2 cells, increased in slices from females within 24 h of exposure to CGRP. Additionally, ir-SPC granule size increased in slices from males and females across 48 h of exposure to CGRP. Exposure of PCLS to exogenous CGRP did not alter the number of solitary pulmonary neuroendocrine cells (PNEC) but did result in neuroendocrine bodies that had significantly more cells. Neuronal fiber numbers were unchanged based on ir-peripherin; however, ir-CGRP became non-detectable in fibers while unchanged in PNECs. The effects of exogenous CGRP provide insight into innate immune and neuroendocrine responses in the lungs that may be partially regulated by neural fibers. The sex-dependent nature of these changes may point to the basis for sex-selective outcomes among respiratory diseases.

Pharmaceutical aspects of novel CGRP inhibitors used in the prophylaxis and treatment of migraine

Migraine is one of the most prevalent neurological disorders known to have an immense adverse socio-economic impact. Neurogenic inflammation is thought to mediate migraine, and CGRP is known to be released during acute attacks of migraine that causes vasodilation in extracerebral arteries. Hence, CGRP is believed to play a key role in triggering migraine. Although there are several classes of medications used in the prevention and treatment of migraine pain, targeted therapies are fewer. Therefore, CGRP receptor inhibitors which bind to CGRP receptors in the cranial vasculature have been developed as drugs for migraine therapy. In this review article, we describe the basic pathophysiologic mechanism that causes migraine headaches and the pharmacotherapeutic aspects of CGRP inhibitors available for clinical use. For the purpose of this review, a search was performed on the pharmacological, pharmacokinetic, pharmaceutical, and therapeutic aspects of the FDA-approved CGRP inhibitors viz. erenumab, ubrogepant, rimegepant, atogepant, eptinezumab, fremanezumab, and galcanezumab in UpToDate database and PubMed beginning year 2000. Based on the data collected, a risk-benefit comparison of different classes of novel CGRP inhibitors available for clinical use is provided. This comparative review may help the healthcare providers in choosing the best pharmacotherapeutic agent for their patients based on patient-specific information.

Update of Gepants in the Treatment of Chronic Migraine

PURPOSE OF REVIEW

Despite the unmet therapeutic needs of patients with chronic migraine (CM) and/or medication overuse, available treatment options are limited. Recently, four calcitonin gene-related peptide receptor antagonists, known as gepants, have been approved for the treatment of migraine. This review focuses on the preventive treatment of CM with gepants and highlights recent findings.

RECENT FINDINGS

Two randomized controlled trials (RCTs) have shown promising results for rimegepant and atogepant as preventive treatments for CM. In an RCT targeting patients with CM, atogepant demonstrated a significant reduction in the mean monthly migraine days, irrespective of acute medication overuse. Moreover, the patients reported no significant safety concerns and exhibited good tolerance to treatment. These findings highlight the potential of gepants as a new and effective therapeutic option for patients with CM and/or medication overuse. Gepant use will help improve the management and quality of life of individuals with this debilitating condition.

Migraine as a Disease Associated with Dysbiosis and Possible Therapy with Fecal Microbiota Transplantation

Migraine is a painful neurological condition characterized by severe pain on one or both sides of the head. It may be linked to changes in the gut microbiota, which are influenced by antibiotic use and other factors. Dysbiosis, which develops and persists as a result of earlier antibiotic therapy, changes the composition of the intestinal flora, and can lead to the development of various diseases such as metabolic disorders, obesity, hematological malignancies, neurological or behavioral disorders, and migraine. Metabolites produced by the gut microbiome have been shown to influence the gut-brain axis. The use of probiotics as a dietary supplement may reduce the number and severity of migraine episodes. Dietary strategies can affect the course of migraines and are a valuable tool for improving migraine management. With fecal microbiota transplantation, gut microbial restoration is more effective and more durable. Changes after fecal microbiota transplantation were studied in detail, and many data help us to interpret the successful interventions. The microbiological alteration of the gut microflora can lead to normalization of the inflammatory mediators, the serotonin pathway, and influence the frequency and intensity of migraine pain.

Inhibiting neuronal AC1 for treating anxiety and headache in the animal model of migraine

Migraines are a common medical condition. From a basic science point of view, the central mechanism for migraine and headache is largely unknown. In the present study, we demonstrate that cortical excitatory transmission is significantly enhanced in the anterior cingulate cortex (ACC)-a brain region which is critical for pain perception. Biochemical studies found that the phosphorylation levels of both the NMDA receptor GluN2B and AMPA receptor GluA1 were enhanced in ACC of migraine rats. Both the presynaptic release of glutamate and postsynaptic responses of AMPA receptors and NMDA receptors were enhanced. Synaptic long-term potentiation (LTP) was occluded. Furthermore, behavioral anxiety and nociceptive responses were increased, which were reversed by application of AC1 inhibitor NB001 within ACC. Our results provide strong evidence that cortical LTPs contribute to migraine-related pain and anxiety. Drugs that inhibit cortical excitation such as NB001 may serve as potential medicines for treating migraine in the future.

Sensory Neuron-TRPV4 Modulates Temporomandibular Disorder Pain Via CGRP in Mice

Temporomandibular disorder (TMD) pain that involves inflammation and injury in the temporomandibular joint (TMJ) and/or masticatory muscle is the most common form of orofacial pain. We recently found that transient receptor potential vanilloid-4 (TRPV4) in trigeminal ganglion (TG) neurons is upregulated after TMJ inflammation, and TRPV4 coexpresses with calcitonin gene-related peptide (CGRP) in TMJ-innervating TG neurons. Here, we extended these findings to determine the specific contribution of TRPV4 in TG neurons to TMD pain, and examine whether sensory neuron-TRPV4 modulates TMD pain via CGRP. In mouse models of TMJ inflammation or masseter muscle injury, sensory neuron-Trpv4 conditional knockout (cKO) mice displayed reduced pain. Coexpression of TRPV4 and CGRP in TMJ- or masseter muscle-innervating TG neurons was increased after TMJ inflammation and masseter muscle injury, respectively. Activation of TRPV4-expressing TG neurons triggered secretion of CGRP, which was associated with increased levels of CGRP in peri-TMJ tissues, masseter muscle, spinal trigeminal nucleus, and plasma in both models. Local injection of CGRP into the TMJ or masseter muscle evoked acute pain in naïve mice, while blockade of CGRP receptor attenuated pain in mouse models of TMD. These results suggest that TRPV4 in TG neurons contributes to TMD pain by potentiating CGRP secretion. PERSPECTIVE: This study demonstrates that activation of TRPV4 in TG sensory neurons drives pain by potentiating the release of pain mediator CGRP in mouse models of TMJ inflammation and masseter muscle injury. Targeting TRPV4 and CGRP may be of clinical potential in alleviating TMD pain.

Novel Migraine Treatments: A Review

Aims: To present a review of the mechanisms of action, available clinical data, and safety profiles of novel migraine therapeutics to inform practice. Methods: PubMed, Medline, and Google Scholar were searched for randomized controlled trials (24 publications), review articles (15 publications), and other pertinent literature (16 publications) discussing the novel migraine therapeutics available between the years 2010 and 2021. All publications were reviewed to assess the mechanism of action, relevant clinical data, and side effect profile for each novel treatment. Therapeutic gain was also recorded in studies that included a placebo arm. Results: A total of 55 studies were included in the final analysis. In the preventive treatment of migraine, novel medications target calcitonin gene-related peptide (CGRP) and fall into either the monoclonal anti-CGRP or gepant class. For the acute treatment of migraine, novel medications fall into either the ditan or gepant class. Several medical devices have been developed for the acute and preventive treatment of migraine. Conclusion: Novel therapeutics are available for both the prevention and acute treatment of migraine headaches. These new medications and neuromodulatory devices appear overall to be safe and effective in the management of migraine headaches.

Advances in CGRP Monoclonal Antibodies as Migraine Therapy: A Narrative Review

Migraine is a potentially disabling disorder, yet it remains underdiagnosed and undertreated. The release of the neuropeptide calcitonin gene-related peptide (CGRP) in the trigemino-cerebrovascular system plays a vital role in the evolution of migraine. It enhances peripheral sensitization by mediating neurogenic inflammation and also influences central sensitization. The majority of the drug classes available for migraine prophylaxis are nonspecific and associated with numerous side effects and drug interactions. Anti-CGRP monoclonal antibodies (mAb) are an innovative therapeutic class that fulfills the need for more efficacious and tolerable preventive therapy. While erenumab is a mAb to the CGRP receptor, eptinezumab, fremanezumab, and galcanezumab bind to the CGRP molecule. They decrease the number of headache days and improve disability. Upper respiratory tract infection, nausea, constipation, pain at the site of injection, and fatigue are the associated side effects. CGRP mAbs are an excellent advancement in translational research and are a promising addition in migraine therapy. This article discusses the recent advances in the development of the CGRP mAbs.

Exploring the pharmacological action mechanism of Ligusticum Chuanxiong-Piper Longum couplet medicines on the treatment of migraine based on network pharmacology

Objective: To study the mechanisms of the Ligusticum chuanxiong Hort.–Piper longum L. herbal pair (LPHP) in the treatment of migraine using network pharmacology.

Methods: The active constituents of LPHP and their targets were searched for and screened using the Chinese Medicine System Pharmacology Database. Genes related to migraine were searched on GeneCards, Online Mendelian Inheritance in Man and other databases. Cytoscape was used to construct and combine active component–target and disease–target networks. The core target was screened by network topology analysis, and the Metascape database was used for gene ontology analysis of key targets and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis to explore the molecular mechanisms in the treatment of migraine.

Results: A total of 28 active constituents of LPHP were obtained through database screening and literature review, and 60 cross-linking targets were obtained. The target sites were analysed using a protein–protein interaction network to obtain six target proteins with a greater degree of relevance. These were identified as the main targets for the treatment of hypertension, and these key targets were found to be associated with 20 signalling pathways, including neuroactive ligand–receptor interaction, the calcium signalling pathway, the cGMP–PKG signalling pathway, pathways in cancer and the cyclic adenosine 3′,5′-cyclic monophosphate (cAMP) signalling pathway.

Conclusion: This study reveals the molecular mechanism of LPHP in the treatment of migraine from the perspective of network pharmacology and provides a basis for further research and molecular mechanism research.

The Effect of Ginger and Its Sub-Components on Pain

Zingiber officinale Roscoe (ginger) has long been used as an herbal medicine to treat various diseases, and its main sub-components, [6]-gingerol and [6]-shogaol, were also reported to have anti-inflammatory, anti-oxidant, and anti-tumor effects. However, their effects on various types of pain and their underlying mechanisms of action have not been clearly analyzed and understood yet. Thus, in this review, by analyzing 16 studies that used Z. officinale, [6]-gingerol, and [6]-shogaol on mechanical, spontaneous and thermal pain, their effects and mechanisms of action have been analyzed. Pain was induced by either nerve injury or chemical injections in rodents. Nine studies analyzed the analgesic effect of Z. officinale, and four and three studies focused on [6]-gingerol and [6]-shogaol, respectively. Seven papers have demonstrated the underlying mechanism of action of their analgesic effects. Studies have focused on the spinal cord and one on the dorsal root ganglion (DRG) neurons. Involvement and change in the function of serotonergic receptors (5-HT_1A, _B, _D, and _5A), transient receptor potential vanilloid 1 (TRPV1), N-methyl-D-aspartate (NMDA) receptors, phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2), histone deacetylase 1 (HDAC1), voltage-gated sodium channel 1.8 (Na_v1.8), substance P (SP), and sciatic nerve’s morphology have been observed.

Overexpression of BDNF in the ventrolateral periaqueductal gray regulates the behavior of epilepsy-migraine comorbid rats

OBJECTIVE

To investigate the effects of brain-derived neurotrophic factor (BDNF) overexpression in the ventrolateral periaqueductal gray (vlPAG) on behavioral changes in epilepsy-migraine comorbid rats.

METHOD

We used an adeno-associated virus (AAV)-mediated vector to supplement BDNF in the vlPAG area prior to the establishment of a pilocarpine-nitroglycerin (Pilo-NTG) combination-induced comorbid model of epilepsy and migraine. Seizure- and migraine-related behaviors were analyzed. Cell loss and apoptosis in vlPAG were detected through hematoxylin-eosin (HE) and TUNEL staining. Immunofluorescence staining analyses were employed to detect expressions of BDNF and its receptor, tyrosine kinase B (TrkB), in vlPAG. Immunohistochemical staining was conducted to detect expressions of c-Fos and calcitonin gene-related peptide (CGRP) in the trigeminal nucleus caudalis (TNC) and trigeminal ganglion (TG).

RESULTS

Comparing to control group, AAV-BDNF injected comorbid group showed lower pain sensitivity, scratching head, and spontaneous seizures accompanied by the downregulation of c-Fos labeling neurons and CGRP immunoreactivity in the TNC and TG. However, these changes were still significantly higher in the comorbid group than those in both epilepsy and migraine groups under the same intervention.

CONCLUSION

These data demonstrated that supplying BDNF to vlPAG may protect structural and functional abnormalities in vlPAG and provide an antiepileptic and analgesic therapy.

Fremanezumab in the prevention of high-frequency episodic and chronic migraine: a 12-week, multicenter, real-life, cohort study (the FRIEND study)

BACKGROUND

Fremanezumab has demonstrated to be effective, safe, and tolerated in the prevention of episodic or chronic migraine (CM) in randomized, placebo-controlled trials (RCTs). Real-life studies are needed to explore drug effects in unselected patients in routine circumstances and to provide higher generalizability results. This study explores the effectiveness, safety, and tolerability of fremanezumab in a real-life population of individuals affected by high-frequency episodic (HFEM: 8-14 days/month) or CM.

METHODS

This is a 12-week multicenter, prospective, cohort, real-life study. We considered all consecutive patients affected by HFEM or CM visited at 9 Italian headache centers from 28/07/2020 to 11/11/2020. Eligible patients were given subcutaneous fremanezumab at the doses of 225 mg monthly or 675 mg quarterly, according to their preference. Primary study endpoints were the change in monthly migraine days (MMDs) in HFEM and monthly headache days (MHDs) in CM patients at weeks 9-12 compared to baseline. Secondary endpoints encompassed variation in monthly analgesic intake (MAI), Numerical Rating Scale (NRS), HIT-6 and MIDAS scores, and ≥ 50%, ≥ 75% and 100% responder rates at the same time intervals.

RESULTS

Sixty-seventh number migraine patients had received ≥ 1 subcutaneous fremanezumab dose and were considered for safety analysis, while 53 patients completed 12 weeks of treatment and were included also in the effectiveness analysis. Fremanezumab was effective in both HFEM and CM, inducing at week 12 a significant reduction in MMDs (-4.6, p < 0.05), MHDs (-9.4, p < 0.001), MAI (-5.7, p < 0.05; -11.1, p < 0.001), NRS (-3.1, p < 0.001; -2.5, p < 0.001), and MIDAS scores (-58.3, p < 0.05; -43.7; p < 0.001). HIT-6 was significantly reduced only in HFEM patients (-18.1, p < 0.001). Remission from CM to episodic migraine and from MO to no-MO occurred in 75% and 67.7% of the patients. The ≥ 50%, ≥ 75% and 100% responder rates at week 12 were 76.5%, 29.4% and 9.9% in HFEM and 58.3%, 25% and 0% in CM. Younger age emerged as a positive response predictor (OR = 0.91; 95% CI 0.85-0.98, p = 0.013). Treatment-emergent adverse events were uncommon (5.7%) and mild. No patient discontinued fremanezumab for any reason.

CONCLUSIONS

Fremanezumab seems more effective in real-life than in RCTs. Younger age emerges as a potential response predictor.

Anti-nociceptive effects of ECa 233 a standardized extract of Centella asiatica (L.) Urban on chronic neuropathic orofacial pain in mice

ETHNOPHARMACOLOGICAL RELEVANCE

ECa 233 is a standardized extract of Centella asiatica (L.) Urban, a herb traditionally used to treat a number of diseases including neurological disorders. Accordingly, ECa 233 showed benefits on animal models of cognitive deficits, chronic stress and Parkinson's disease. Analgesic activity of ECa 233 was shown in Tail's flick test in rodent and relieving aphthous ulcer pain in man. Moreover, acute and sub-chronic toxicity testing in rodents and pharmacokinetic study in healthy volunteers, clinical trial phase I demonstrated good safety profiles of ECa 233.

AIM OF THE STUDY

This study aims to evaluate the anti-nociceptive effects of ECa 233 and its synergistic effect with gabapentin on chronic neuropathic orofacial pain after 3 weeks infraorbital nerve chronic constriction injury in mice. The peripheral and central nociceptive activities are also examined.

MATERIALS AND METHODS

Chronic neuropathic orofacial pain was induced by 3 weeks infraorbital nerve chronic constriction injury. Mice were treated with ECa 233 (30, 100 and 300 mg/kg) and gabapentin (10 mg/kg) by oral gavage starting on day 21 and going on for 14 consecutive days. Mechanical hyperalgesia and allodynia were measured on day 7, 14, 21, 28 and 35 after infraorbital nerve chronic constriction injury. At the end of the experiment, mice were observed for the sedative effect using the locomotor activity, the calcitonin gen-related peptide in trigeminal ganglion and c-fos expression in trigeminal nucleus caudalis were investigated after euthanasia.

RESULTS

Infraorbital nerve chronic constriction injury gradually induced marked ipsilateral mechanical hyperalgesia and allodynia. The maximum hyperalgesia and allodynia response presented on day 21 and the response was remained constant until day 35. Treatment with either 300 mg/kg ECa 233 or 10 mg/kg gabapentin were able to attenuate mechanical hyperalgesia and allodynia. The downregulation of calcitonin gen-related peptide on ipsilateral trigeminal ganglion were observed in ECa 233 at 100 and 300 mg/kg and 10 mg/kg gabapentin-treated groups. The c-fos expression on ipsilateral trigeminal nucleus caudalis was also decreased in 300 mg/kg ECa 233 and 10 mg/kg gabapentin-treated groups.

CONCLUSION

ECa 233 reduced hyperalgesia and allodynia by modulating the peripheral calcitonin gen-related peptide expression consequently alleviate the nociceptive activity in trigeminal nucleus caudalis. Further clinical trial to proof ECa 233's efficacy in neuropathic pain in man as well as possible attributable mechanism of action should be further investigated.

Shortening Synthetic Routes to Small Molecule Active Pharmaceutical Ingredients Employing Biocatalytic Methods

Biocatalysis, using enzymes for organic synthesis, has emerged as powerful tool for the synthesis of active pharmaceutical ingredients (APIs). The first industrial biocatalytic processes launched in the first half of the last century exploited whole-cell microorganisms where the specific enzyme at work was not known. In the meantime, novel molecular biology methods, such as efficient gene sequencing and synthesis, triggered breakthroughs in directed evolution for the rapid development of process-stable enzymes with broad substrate scope and good selectivities tailored for specific substrates. To date, enzymes are employed to enable shorter, more efficient, and more sustainable alternative routes toward (established) small molecule APIs, and are additionally used to perform standard reactions in API synthesis more efficiently. Herein, large-scale synthetic routes containing biocatalytic key steps toward >130 APIs of approved drugs and drug candidates are compared with the corresponding chemical protocols (if available) regarding the steps, reaction conditions, and scale. The review is structured according to the functional group formed in the reaction.

Pharmacological, Pharmacokinetic, Pharmacodynamic and Physicochemical Characterization of FE 205030: A Potent, Fast Acting, Injectable CGRP Receptor Antagonist for the Treatment of Acute Episodic Migraine

The neuropeptide calcitonin gene-related peptide (CGRP) is known to play a central role in the underlying pathophysiology of migraine. In comparison to the effective triptan class of antimigraine treatments, the CGRP antagonists possess a comparable efficacy but a superior cardiovascular safety profile in patients. This paper describes the development of selective and potent peptidic CGRP antagonist, FE 205030, that has a fast onset of action and an optimal half-life (subcutaneous T_max ~ 60 min, and t_1/2 ~ 4.4 h in 80 kg pigs, respectively), which is key to prevention of the progression of debilitating migraine symptoms. The in vivo efficacy of this agent has been established a translational pharmacodynamic model (inhibition of capsaicin-induced increase in skin blood flow) in cynomolgus monkeys and shows maximal inhibitory activity at circulating concentrations of 30-100 nM. Antagonist activity of FE 205030 was characterized on CGRP-induced vasodilation in isolated human mesenteric resistance arteries in an ex vivo isometric myograph study, and FE 205030 effectively blocked CGRP-induced vasodilation with a pA₂ of 9.3 ± 0.1, mean ± standard error. Multispecies allometric scaling and modeling of subcutaneous (SC) effective concentrations indicates that a dose of 10-30 mg/day is sufficient to achieve a drug exposure/target coverage of 8h, which is useful to prevent migraine recurrence in patients. The molecule also possesses appropriate physicochemical properties that allows for a convenient dosing form factor of 1 ml injection volume with a sufficient solubility and acceptable short-term stability, optimal for treatment of acute migraine episodes in patients. Hence, FE 205030 may provide an important fast-acting injectable option for patients suffering from frequent acute migraine episodes, complementary to preventative monoclonal antibodies and oral small molecule CGRP-R antagonist therapies.

Development and validation of a reporter gene assay for bioactivity determination of Anti-CGRP monoclonal antibodies

Calcitonin gene-related peptide (CGRP) is critical for the pathophysiology of migraine, and four therapeutic antibodies targeting CGRP and its corresponding receptors have been approved by the Food and Drug Administration (FDA), while many others are in the different stages of clinical trials. Bioactivity determination is essential for the quality control and clinical application of therapeutic monoclonal antibodies (mAbs). However, no bioassay has been reported to date. In this study, we developed a reporter gene assay (RGA) based on SK-N-MC cells stably expressing firefly luciferase driven by cAMP response element (CRE). The key assay parameters were optimized according to signal-to-noise (SNR), the response value, and the fitted dose-response curve. Validation of the RGA in accordance with ICH-Q2 guidelines showed that the method had good specificity, accuracy, linearity, and precision. The established RGA can be utilized as a reference method for release testing and stability studies of relevant antibodies.

Peptidomimetics - An infinite reservoir of metal binding motifs in metabolically stable and biologically active molecules

The involvement of metal ions in interactions with therapeutic peptides is inevitable. They are one of the factors able to fine-tune the biological properties of antimicrobial peptides, a promising group of drugs with one large drawback - a problematic metabolic stability. Appropriately chosen, proteolytically stable peptidomimetics seem to be a reasonable solution of the problem, and the use of D-, β-, γ-amino acids, unnatural amino acids, azapeptides, peptoids, cyclopeptides and dehydropeptides is an infinite reservoir of metal binding motifs in metabolically stable, well-designed, biologically active molecules. Below, their specific structural features, metal-chelating abilities and antimicrobial potential are discussed.

Effect of occipitoatlantal decompression on cerebral blood flow dynamics as evaluated by Doppler ultrasonography

Context

Osteopathic manipulative treatment reduces symptoms in patients with headache disorders, but the underlying mechanisms are unclear.

Objective

To evaluate blood flow in the intracranial and extracranial vasculature before and after occipitoatlantal decompression (OAD) using Doppler ultrasonography.

Methods

Healthy, first-year osteopathic medical students from A.T. Still University's Kirksville College of Osteopathic Medicine participated in a randomized, single-blinded, two-period, two-treatment crossover study. The participants were randomly assigned to 1 of 2 treatment interventions: OAD or sham touch. After one week, participants returned to have the other intervention performed. Blood flow parameters-peak systolic velocity (PSV) and end-diastolic velocity (EDV)-in the middle cerebral artery (MCA), internal carotid artery (ICA), and vertebral artery (VA) were evaluated before, immediately after, 5 minutes after, and 10 minutes after treatment. Differences in PSV, EDV, heart rate (HR), and blood pressure (BP) for both interventions were analyzed for the four time points using mixed-effects models.

Results

Thirty healthy medical students (11 men, 19 women; mean age, 24 years) participated in this study. EDV increased after OAD in the MCA, ICA, and VA (all p<0.001); no change occurred after sham touch (all p>0.05). EDV was greater for all post-treatment timepoints after OAD in the MCA, ICA, and VA than after sham touch (all p<0.001). Although baseline PSV in the MCA measured before treatment was different between treatment interventions (p=0.01), no difference was found between interventions at any post-treatment time point (all p>0.59). Changes in PSV in the ICA and VA and for HR and BP did not depend on treatment intervention (p>0.06).

Conclusion

Increases in EDV occurred in major cranial arteries after OAD but not after sham touch, indicating that OAD improves blood flow to the brain. The exact mechanism of this increase is unknown; however, it can be explained by either parasympathetic stimulation through the secretion of vasodilating neurotransmitters or by a decrease in external tissue pressure on ICA and VA, with the resulting flow causing further dilation in the MCA.

Rimegepant Orally Disintegrating Tablet for Acute Migraine Treatment: A Review

OBJECTIVE

To review the pharmacology, pharmacokinetics, efficacy, safety, and place in therapy of rimegepant for treatment of migraine.

DATA SOURCES

A comprehensive PubMed and Cochrane search (1985 to May 2020) was performed utilizing the keywords rimegepant, Nurtec, orally disintegrating tablet, migraine, migraine headache, migraine disorder, calcitonin gene-related peptide, and calcitonin gene-related peptide antagonist. Additional data were obtained from the references of identified articles, manufacturer's product labeling and website, ClinicalTrials.gov, and governmental sources.

STUDY SELECTION AND DATA EXTRACTION

All English-language trials evaluating oral rimegepant were included for this review.

DATA SYNTHESIS

Rimegepant orally disintegrating tablet (ODT) is Food and Drug Administration approved for the treatment of migraine. According to data from 3 phase 3 randomized controlled trials, rimegepant has been shown to significantly improve freedom from pain at 2 hours after the dose and freedom from the most bothersome symptom 2 hours postdose. Additional outcomes improved include freedom from photophobia and phonophobia at 2 hours postdose and pain relief 2 hours after the dose. Adverse effects of rimegepant include nausea, urinary tract infection, and dizziness.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Orally disintegrating rimegepant provides a novel mechanism of action for the treatment of acute migraine. When patients experience inadequate relief from other therapies, have contraindications to triptans, or are unable to tolerate the adverse effects of triptans, rimegepant is a promising therapeutic option.

CONCLUSION

Rimegepant ODT is an efficacious migraine treatment option with a novel mechanism of action, convenient dosage form, and limited adverse effect profile.

Palmatine alleviates hyperalgesia by inhibiting the expression of calcitonin gene-related peptide in the trigeminal ganglion of rats with chronic constriction injury of the infraorbital nerve

Trigeminal neuralgia is one of the most common of the neuropathic pains, and it can seriously influence patients' quality of life. Calcitonin gene-related peptide (CGRP) is a type of nociceptive neurotransmitter that is expressed in neurons of the trigeminal ganglion and plays a major part in transmitting pain. The rat model of trigeminal neuralgia was established by causing a chronic constriction injury of the infraorbital nerve (CCI-ION). Male Sprague-Dawley rats (n=24) were randomly divided into a sham control group (sham, n=6), sham-treated with palmatine group (sham+palmatine, n=6), trigeminal nerve model group (TN, n=6), and trigeminal nerve treated with palmatine group (TN+palmatine, n=6). Fifteen days after the operation the mechanical response threshold was decreased in the TN group compared with the sham group. From postoperative day 7 to day 15, the mechanical response threshold in the TN+palmatine group significantly increased compared with the TN group. On postoperative day 15 the results of quantitative polymerase chain reaction (qPCR), immunohistochemical staining, and western blotting showed an obvious increase in expression of CGRP and its receptors, serum concentrations of interleukin-1β (IL-1β), and tumour necrosis factor-α (TNF-α), and phosphorylation of protein kinase C (PKC) in the trigeminal ganglia of the TN group compared with the sham group, but these increases could be down-regulated by treatment with palmatine. Palmatine might therefore have therapeutic potential for the treatment of trigeminal neuralgia by inhibiting the expression of CGRP and its receptors in trigeminal ganglia, suppressing the serum concentrations of IL-1β and TNF-α, and decreasing the phosphorylation of PKC in the trigeminal ganglia of affected rats.

Characterization of the effects of calcitonin gene-related peptide receptor antagonist for Alzheimer's disease

Calcitonin gene-related peptide (cGRP) receptor antagonists effectively treat migraine through reducing neuroinflammation, vasoconstriction and possibly neruogenesis. Since neuroinflammation is also involved in the pathogenesis of Alzheimer's diseases (AD), we hypothesized and tested if a cGRP receptor antagonist, BIBN 4096 BS (BIBN), has effects on AD pathology. Using an AD mouse model, 5XFAD, with different ages, here we report that the BIBN treatment significantly increased the brain expression of PSD95, a postsynaptic protein, in both young and old AD mice. In parallel, BIBN improved learning and memory in the behavior test in the young, but not old, AD mice. The BIBN treatment reduced α-synuclein aggregation in both young and old AD mice. BIBN significantly decreased neuroinflammatory markers of ionized calcium binding adapter molecules-1 (Iba-1) and the p38 MAPK and NFκB signaling pathways in young, but not old, AD mice. The treatment also reduced the accumulation of amyloid-β (Aβ), and decreased tau phosphorylation through the pathway of CDK5/p25 in young mice only. Our study provides the evidence and suggests that the cGRP antagonists might be a therapeutic target to attenuate the pathological cascade and delay cognitive decline of AD in humans.

Calcitonin Gene-Related Peptide Antagonists for the Prevention of Migraine: Highlights From Pivotal Studies and the Clinical Relevance of This New Drug Class

Objective: To review the new drug class of calcitonin gene-related peptide antagonists (monoclonal antibodies) and their clinical relevance in migraine prophylaxis. Data Sources: A literature search was performed in PubMed (January 2009 to November 2019) using the terms migraine, calcitonin gene-related peptide (CGRP), erenumab, fremanezumab, and galcanezumab for clinical trials and studies. Study Selection and Data Extraction: Reports from human studies in English were evaluated for clinical evidence supporting pharmacology, efficacy, and adverse events. Initial pharmacokinetic and preclinical studies were excluded. Data Synthesis: In chronic and episodic migraine, prophylaxis with injections of monoclonal antibodies antagonizing CGRP reduced monthly migraine days with minimal clinically significant adverse events. In addition, there is evidence supporting efficacy in refractory migraine despite optimal prophylaxis. Relevance to Patient Care and Clinical Practice: This is the first target-specific migraine prophylaxis treatment to show efficacy with minimal adverse effects. A higher drug cost is a barrier but is balanced by improved quality of life. Current therapies have limited efficacy and tolerability because of poor side effect profiles. CGRP antagonists represent a shift to more precise migraine treatments. Conclusions: Monoclonal antibodies inhibiting CGRP are effective in migraine prophylaxis with minimal adverse effects. Targeting CGRP is a novel clinical strategy in managing migraine.

Dysregulated Tear Fluid Nociception-Associated Factors, Corneal Dendritic Cell Density, and Vitamin D Levels in Evaporative Dry Eye

Purpose

The purpose of this study was to study the status and association among tear-soluble factors, corneal dendritic cell density, vitamin D, and signs and symptoms in dry eye disease (DED).

Methods

A total of 33 control subjects and 47 evaporative dry eye patients were included in the study. DED diagnosis and classification was based on the 2017 Report of the Tear Film & Ocular Surface Society International Dry Eye Workshop (TFOS DEWS II). DED workup, including tear film break-up time (TBUT), Schirmer's test I (STI), corneal and conjunctival staining, ocular surface disease index (OSDI) scoring, and in vivo confocal microscopy (to assess corneal dendritic cell density [cDCD] and subbasal nerve plexus [SBNP] features) was performed in the study subjects. Tear fluid using Schirmer's strip and serum were collected from the subjects. Multiplex ELISA or single analyte ELISA was performed to measure 34 tear-soluble factors levels including vitamin D.

Results

Significantly higher OSDI discomfort score, lower TBUT, and lower STI were observed in DED patients. cDCD was significantly higher in DED patients. No significant difference was observed in SBNP features. Tear fluid IL-1β, IL-17A, MMP9, MMP10, MMP9/TIMP ratio, and VEGF-B were significantly higher in DED patients. Significantly lower tear fluid IL-2, IP-10, NPY, VEGF-A, and vitamin D was observed in DED patients. These dysregulated tear factors showed significant associations with DED signs and symptoms.

Conclusions

Altered tear fluid soluble factors with potential to modulate nociception exhibited a distinct association with ocular surface discomfort status, TBUT, STI, and cDCD. This implies a functional relationship between the various tear-soluble factors and dry eye pathogenesis, indicating new molecular targets for designing targeted therapies.

Analysis of HCRTR2, GNB3, and ADH4 Gene Polymorphisms in a Southeastern European Caucasian Cluster Headache Population

Studies point to an increased hereditary risk of cluster headache. HCRTR2 gene rs2653349 and ADH4 gene rs1800759 polymorphisms have been associated with cluster headache susceptibility. Also, GNB3 rs5443 polymorphism, associated with increased signal transduction via GPCRs, seems to influence triptan treatment response. DNA from 114 cluster headache patients and 570 non-related controls, representing a general Southeastern European Caucasian (SEC) population, was extracted from buccal swabs and genotyped using real-time PCR. Gene distribution for the rs2653349 was GG = 79.8%, GA = 18.4%, and AA = 1.8% for patients and GG = 79.1%, GA = 19.1%, and AA = 1.8% for controls. The frequency of the mutated A allele was 11.0% for patients and 11.3% for controls. The frequencies for rs5443 were CC = 44.7%, CT = 44.7%, and TT = 10.5% for patients and CC = 43.9%, CT = 42.6%, and TT = 13.5% for controls. The frequency of the mutated T allele was 32.9% for patients and 34.8% for controls. A 2.7-fold more frequent appearance of the mutated T allele was observed in patients with better triptan treatment response, although not statistically significant. For rs1800759, the frequencies were CC = 36.0%, CA = 43.0%, and AA = 21.0% for patients and CC = 34.0%, CA = 50.2%, and AA = 15.8% for controls. The frequency of the mutated A allele was 42.5% and 40.9% for patients and controls, respectively. The mutated T allele of GNB3 rs5443 polymorphism was more prevalent in patients with better triptan treatment response, indicating a possible trend of association between this polymorphism and triptan treatment response in SEC population. According to our observation, no association of HCRTR2 rs2653349 and ADH4 rs1800759 polymorphisms and cluster headache in SEC population could be documented.

The CGRP Pathway in Migraine as a Viable Target for Therapies

The neuropeptide calcitonin gene-related peptide is well established as a key player in the pathogenesis of migraine. Clinical studies show calcitonin gene-related peptide levels correlate with migraine attacks, and decreases in this neuropeptide can indicate antimigraine therapy effectiveness. Research has revealed a wide distribution of expression sites for calcitonin gene-related peptide in the central and peripheral nervous system. Of these, the calcitonin gene-related peptide receptor, which binds calcitonin gene-related peptide with high affinity, has attracted growing interest as a viable target for antimigraine therapies. An incentive to pursue such research is the continuing unmet medical need of patients. Triptans have offered some clinical benefit, but many patients do not respond and these drugs have important safety considerations. Initial calcitonin gene-related peptide-focused research led to development of the "gepant" small-molecule calcitonin gene-related peptide receptor blockers. Positive efficacy reports concerning the gepants have been tempered by safety findings which led to the discontinuation of some of these agents. Currently, there is considerable excitement regarding monoclonal antibodies against calcitonin gene-related peptide (eptinezumab, galcanezumab, fremanezumab) and the calcitonin gene-related peptide receptor (erenumab). To date, these monoclonal antibodies have shown promising efficacy in clinical trials, with no major safety concerns. If ongoing long-term studies show that their efficacy can be maintained, this may herald a new era for effective antimigraine therapies.

Anti-CGRP and anti-CGRP receptor monoclonal antibodies as antimigraine agents. Potential differences in safety profile postulated on a pathophysiological basis

Calcitonin gene-related peptide (CGRP) is a peptide neurotransmitter with potent vasodilating properties. CGRP is believed to play a primary role in the pathogenesis of migraine. As such, CGRP and its receptors are obvious druggable targets for novel anti-migraine agents. While the development of small-molecule CGRP receptor antagonists started first, none of these agents is yet available in clinical practice. Conversely, both anti-CGRP and anti-CGRP receptor monoclonal antibodies (mABs) completed clinical development, and the first representatives of these 2 classes are available on the market. MABs are approved for prevention of migraine attacks in chronic or episodic migraine, involving long-term treatments. In light of the physiological role exerted by CGRP in the regulation of vascular tone, the potential risks of a long-term inhibition of CGRP functions raised diffuse concerns. These concerns were correctly addressed by the anti-CGRP receptor mABs erenumab with a 5-year open-label clinical trial; however, this study is currently ongoing and results are not yet available, leaving some uncertainty on the profile of erenumab long-term safety. Similar concerns can be raised with direct anti-CGRP mABs, which entrap the peptide preventing receptor activation. However, evidence exists that plasma CGRP is detectable in patients chronically treated with anti-CGRP mABs. Assuming that plasma CGRP is an indirect marker of peptide levels at the vascular receptor sites, such residual CGRP would maintain a physiological level of receptor stimulation, in spite of a well-established anti-migraine activity of the mABs. This might represent a potential advantage in the safety profile of anti-CGRP mABs, but it needs to be confirmed and expanded with data on free plasma CGRP.

Development of chimeric and bifunctional antagonists for CLR/RAMP receptors

CGRP, adrenomedullin (ADM), and adrenomedullin 2 (ADM2) family peptides are important neuropeptides and hormones for the regulation of neurotransmission, vasotone, cardiovascular morphogenesis, vascular integrity, and feto‒placental development. These peptides signal through CLR/RAMP1, 2 and 3 receptor complexes. CLR/RAMP1, or CGRP receptor, antagonists have been developed for the treatment of migraine headache and osteoarthritis pain; whereas CLR/RAMP2, or ADM receptor, antagonists are being developed for the treatment of tumor growth/metastasis. Based on the finding that an acylated chimeric ADM/ADM2 analog potently stimulates CLR/RAMP1 and 2 signaling, we hypothesized that the binding domain of this analog could have potent inhibitory activity on CLR/RAMP receptors. Consistent with this hypothesis, we showed that acylated truncated ADM/ADM2 analogs of 27–31 residues exhibit potent antagonistic activity toward CLR/RAMP1 and 2. On the other hand, nonacylated analogs have minimal activity. Further truncation at the junctional region of these chimeric analogs led to the generation of CLR/RAMP1-selective antagonists. A 17-amino-acid analog (Antagonist 2–4) showed 100-fold selectivity for CLR/RAMP1 and was >100-fold more potent than the classic CGRP receptor antagonist CGRP8-37. In addition, we showed (1) a lysine residue in the Antagonist 2–4 is important for enhancing the antagonistic activity, (2) an analog consisted of an ADM sequence motif and a 12-amino-acid binding domain of CGRP exhibits potent CLR/RAMP1-inhibitory activity, and (3) a chimeric analog consisted of a somatostatin analog and an ADM antagonist exhibits dual activities on somatostatin and CLR/RAMP receptors. Because the blockage of CLR/RAMP signaling prevents migraine pain and suppresses tumor growth/metastasis, further studies of these analogs, which presumably have better access to the tumor microenvironment and nerve endings at the trigeminal ganglion and synovial joints as compared to antibody-based therapies, may lead to the development of better anti-CGRP therapy and alternative antiangiogenesis therapy. Likewise, the use of bifunctional somatostatin-ADM antagonist analogs could be a promising strategy for the treatment of high-grade neuroendocrine tumors by targeting an antiangiogenesis agent to the neuroendocrine tumor microenvironment.

The need for new acutely acting antimigraine drugs: moving safely outside acute medication overuse

Background

The treatment of migraine is impeded by several difficulties, among which insufficient headache relief, side effects, and risk for developing medication overuse headache (MOH). Thus, new acutely acting antimigraine drugs are currently being developed, among which the small molecule CGRP receptor antagonists, gepants, and the 5-HT_1F receptor agonist lasmiditan. Whether treatment with these drugs carries the same risk for developing MOH is currently unknown.

Main body

Pathophysiological studies on MOH in animal models have suggested that decreased 5-hydroxytryptamine (5-HT, serotonin) levels, increased calcitonin-gene related peptide (CGRP) expression and changes in 5-HT receptor expression (lower 5-HT_1B/D and higher 5-HT_2A expression) may be involved in MOH. The decreased 5-HT may increase cortical spreading depression frequency and induce central sensitization in the cerebral cortex and caudal nucleus of the trigeminal tract. Additionally, low concentrations of 5-HT, a feature often observed in MOH patients, could increase CGRP expression. This provides a possible link between the pathways of 5-HT and CGRP, targets of lasmiditan and gepants, respectively. Since lasmiditan is a 5-HT_1F receptor agonist and gepants are CGRP receptor antagonists, they could have different risks for developing MOH because of the different (over) compensation mechanisms following prolonged agonist versus antagonist treatment.

Conclusion

The acute treatment of migraine will certainly improve with the advent of two novel classes of drugs, i.e., the 5-HT_1F receptor agonists (lasmiditan) and the small molecule CGRP receptor antagonists (gepants). Data on the effects of 5-HT_1F receptor agonism in relation to MOH, as well as the effects of chronic CGRP receptor blockade, are awaited with interest.

Drug updates and approvals: 2018 in review

In 2018, the FDA approved several new drugs for use in primary care. This article highlights the following new drugs: bictegravir, emtricitabine, and tenofovir alafenamide (Biktarvy); doxylamine succinate and pyridoxine hydrochloride (Bonjesta); erenumab-aooe (Aimovig); lofexidine hydrochloride (Lucemyra); tezacaftor and ivacaftor (Symdeko); and tildrakizumab-asmn (Ilumya).

Neuropeptides in asthma, chronic obstructive pulmonary disease and cystic fibrosis

The nervous system mediates key airway protective behaviors, including cough, mucus secretion, and airway smooth muscle contraction. Thus, its involvement and potential involvement in several airway diseases has become increasingly recognized. In the current review, we focus on the contribution of select neuropeptides in three distinct airway diseases: asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis. We present data on some well-studied neuropeptides, as well as call attention to a few that have not received much consideration. Because mucus hypersecretion and mucus obstruction are common features of many airway diseases, we place special emphasis on the contribution of neuropeptides to mucus secretion. Finally, we highlight evidence implicating involvement of neuropeptides in mucus phenotypes in asthma, COPD and cystic fibrosis, as well as bring to light knowledge that is still lacking in the field.

The potentiating effect of calcitonin gene-related peptide on transient receptor potential vanilloid-1 activity and the electrophysiological responses of rat trigeminal neurons to nociceptive stimuli

Growing evidence suggests that calcitonin gene-related peptide (CGRP) participates in trigeminal nociceptive responses. However, the role of CGRP in sensitization or desensitization of nociceptive transduction remains poorly understood. In this study, we sought to further investigate the CGRP-induced up-regulation of transient receptor potential vanilloid-1 (TRPV1) and the responses of trigeminal neurons to nociceptive stimuli. Rat trigeminal ganglion (TG) organ cultures and isolated trigeminal neurons were incubated with CGRP. An increase in TRPV1 levels was observed in CGRP-incubated TG organ cultures. CGRP potentiated capsaicin-induced increase in phosphorylated CaMKII levels in the TG organ cultures. The incubation of the trigeminal neurons with CGRP significantly increased the inward currents in response to capsaicin challenge, and this effect was inhibited by co-incubation with the CGRP receptor antagonist, BIBN4068BS or the inhibitor of protein kinase A, H-89. These findings reveal that CGRP acting on trigeminal neurons may play a significant role in facilitating cellular events that contribute to the peripheral sensitization of the TG in nociceptive transmission.

Calcitonin Gene-Related Peptide Antagonists and Therapeutic Antibodies

The calcitonin gene-related peptide (CGRP) receptor is composed of the calcitonin receptor-like receptor (CLR, a class B GPCR) and a single-pass membrane protein known as receptor activity modifying protein type 1 (RAMP1). The levels of the CGRP peptide increase during a migraine attack and infusion of CGRP can provoke a migraine attack. Consequently, there is much interest in inhibiting the actions of CGRP as a way to control migraine. Here we describe the development of small molecule antagonists designed to bind to the CGRP receptor to block its action by preventing binding of the CGRP peptide. We also describe the development of antibody drugs, designed to bind either to the CGRP receptor to block its action, or to bind directly to the CGRP peptide. The field has been very active, with one antibody drug approved and three antibody drugs in phase III clinical trial. Initial programs on the development CGRP antagonists were frustrated by liver toxicity but the current outlook is very promising with five small molecule antagonists in various stages of clinical trial.

Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of the CGRP Binding Monoclonal Antibody LY2951742 (Galcanezumab) in Healthy Volunteers

Background: Calcitonin gene-related peptide (CGRP) is pivotal in the pathophysiology of migraine headaches and represents a promising target for migraine treatment. The humanized monoclonal antibody galcanezumab (LY2951742) binds to CGRP and may be effective in migraine prophylaxis.

Objectives: The primary objective was to evaluate the safety and tolerability of single and multiple doses of galcanezumab in humans. Secondary objectives included assessing the pharmacokinetics and evaluating target engagement.

Methods: A double-blind, randomized, placebo-controlled study (NCT 01337596) with single escalating and multiple subcutaneous (SC) doses of galcanezumab was performed in healthy male volunteers. Single doses of 1, 5, 25, 75, 200, and 600 mg of galcanezumab (n = 7/dose) or placebo (n = 2/dose) were injected SC in six consecutive cohorts of nine subjects each. One cohort of nine subjects received multiple (4) 150 mg doses of galcanezumab or placebo every other week. Target engagement was evaluated by measuring inhibition of capsaicin-induced increase in dermal blood flow (DBF).

Findings: Sixty-three subjects were randomized and included in the safety analyses. Galcanezumab was well tolerated in single doses (1–600 mg SC) and consecutive doses (150 mg SC). There was no dose-dependent difference in type or frequency of treatment-emergent adverse events, and no clinically meaningful difference when compared with placebo. Pharmacokinetics were linear. Galcanezumab induced a robust, dose-dependent, and durable inhibition of capsaicin-induced increase in DBF, supporting the continued clinical development of galcanezumab for prophylaxis in migraine patients.

Histamine and Migraine

BACKGROUND

Histamine is an ancient "tissue amine" preceding multicellular organisms. In the central nervous system (CNS), its fibers originate solely from the tuberomammillary nucleus and travel throughout the brain. It is mainly responsible for wakefulness, energy homeostasis, and memory consolidation. Recently, several studies suggest a potential role of histamine in migraine pathogenesis and management.

METHODS

Narrative review of current literature regarding histamine and migraine.

RESULTS

Histamine plays a crucial role in migraine pathogenesis: sustaining the neurogenic inflammation pathway. Interaction between mast cells (MC) and calcitonin-gene related protein (CGRP) results in sensitization of trigeminal afferents and trigeminal ganglia (TG). Histamine binds with differing affinities to four different histaminergic G-protein coupled receptors, activating protein kinases, or triggering calcium release with subsequent mode of actions. Histamine 1 receptor (H₁ R) and histamine 2 receptor (H₂ R) antagonists are frequently used for the treatment of allergy and gastric acid secretion, respectively, but their antagonism is probably ineffective for migraine. Histamine 3 receptor (H₃ R) and histamine 4 receptor (H₄ R) have a threefold higher affinity than H₁ R/H₂ R for histamine and are found almost exclusively on neurons and immune tissues, respectively. H₃ R acts as an autoreceptor or as a heteroreceptor, lowering the release of histamine and other neurotransmitters. This is a potential target for anti-nociception and anti-neurogenic inflammation. To date, several small clinical trials using low dose histamine or N^α -methylhistamine have demonstrated migraine prophylactic efficacy, probably via H₃ R or other undetermined pathways.

CONCLUSION

The histamine system interacts with multiple regions in the CNS and may hypothetically modulate the migraine response. Low dose histamine may be a promising option for migraine prevention.

Drosophila DH31 Neuropeptide and PDF Receptor Regulate Night-Onset Temperature Preference

Body temperature exhibits rhythmic fluctuations over a 24 h period (Refinetti and Menaker, 1992) and decreases during the night, which is associated with sleep initiation (Gilbert et al., 2004; Kräuchi, 2007a,b). However, the underlying mechanism of this temperature decrease is largely unknown. We have previously shown that Drosophila exhibit a daily temperature preference rhythm (TPR), in which their preferred temperatures increase during the daytime and then decrease at the transition from day to night (night-onset) (Kaneko et al., 2012). Because Drosophila are small ectotherms, their body temperature is very close to that of the ambient temperature (Stevenson, 1985), suggesting that their TPR generates their body temperature rhythm. Here, we demonstrate that the neuropeptide diuretic hormone 31 (DH31) and pigment-dispersing factor receptor (PDFR) contribute to regulate the preferred temperature decrease at night-onset. We show that PDFR and tethered-DH31 expression in dorsal neurons 2 (DN2s) restore the preferred temperature decrease at night-onset, suggesting that DH31 acts on PDFR in DN2s. Notably, we previously showed that the molecular clock in DN2s is important for TPR. Although PDF (another ligand of PDFR) is a critical factor for locomotor activity rhythms, Pdf mutants exhibit normal preferred temperature decreases at night-onset. This suggests that DH31-PDFR signaling specifically regulates a preferred temperature decrease at night-onset. Thus, we propose that night-onset TPR and locomotor activity rhythms are differentially controlled not only by clock neurons but also by neuropeptide signaling in the brain.

SIGNIFICANCE STATEMENT

Body temperature rhythm (BTR) is fundamental for the maintenance of functions essential for homeostasis, such as generating metabolic energy and sleep. One major unsolved question is how body temperature decreases dramatically during the night. Previously, we demonstrated that a BTR-like mechanism, referred to as temperature preference rhythm (TPR), exists in Drosophila Here, we demonstrate that the diuretic hormone 31 (DH31) neuropeptide and pigment-dispersing factor receptor (PDFR) regulate preferred temperature decreases at night-onset via dorsal neurons 2. This is the first in vivo evidence that DH31 could function as a ligand of PDFR. Although both DH31 and PDF are ligands of PDFR, we show that DH31 regulates night-onset TPR, but PDF does not, suggesting that night-onset TPR and locomotor activity rhythms are controlled by different neuropeptides via different clock cells.

Induction of Migraine-Like Photophobic Behavior in Mice by Both Peripheral and Central CGRP Mechanisms

The neuropeptide calcitonin gene-related peptide (CGRP) is a key player in migraine. Although migraine can be treated using CGRP antagonists that act peripherally, the relevant sites of CGRP action remain unknown. To address the role of CGRP both within and outside the CNS, we used CGRP-induced light-aversive behavior in mice as a measure of migraine-associated photophobia. Peripheral (intraperitoneal) injection of CGRP resulted in light-aversive behavior in wild-type CD1 mice similar to aversion seen previously after central (intracerebroventricular) injection. The phenotype was also observed in C57BL/6J mice, although to a lesser degree and with more variability. After intraperitoneal CGRP, motility was decreased in the dark only, similar to motility changes after intracerebroventricular CGRP. In addition, as with intracerebroventricular CGRP, there was no general increase in anxiety as measured in an open-field assay after intraperitoneal CGRP. Importantly, two clinically effective migraine drugs, the 5-HT1B/D agonist sumatriptan and a CGRP-blocking monoclonal antibody, attenuated the peripheral CGRP-induced light aversion and motility behaviors. To begin to address the mechanism of peripheral CGRP action, we used transgenic CGRP-sensitized mice that have elevated levels of the CGRP receptor hRAMP1 subunit in nervous tissue (nestin/hRAMP1). Surprisingly, sensitivity to low light was not seen after intraperitoneal CGRP injection, but was seen after intracerebroventricular CGRP injection. These results suggest that CGRP can act in both the periphery and the brain by distinct mechanisms and that CGRP actions may be transmitted to the CNS via indirect sensitization of peripheral nerves.

SIGNIFICANCE STATEMENT

The neuropeptide calcitonin gene-related peptide (CGRP) is a central player in migraine pathogenesis, yet its site(s) of action remains unknown. Some preclinical studies have pointed to central sites in the brain and brainstem. However, a peripheral site of action is indicated by the ability of intravenous CGRP to trigger migraine in humans and the efficacy of CGRP receptor antagonists that evidently do no penetrate the CNS in effective amounts. Resolving this issue is particularly important given recent clinical trials showing that anti-CGRP monoclonal antibodies can reduce and even prevent migraine attacks. In this study, we report that CGRP can act in both the brain and the periphery of the mouse to cause migraine-like photophobia by apparently distinct mechanisms.

Privileged heterocycles: bioactivity and synthesis of 1,9-diazaspiro[5.5]undecane-containing compounds

This review discusses the biological activity and synthesis of 1,9-diazaspiro[5.5]undecanes, including those ring-fused with arenes and heteroarenes and/or containing a carbonyl group at position 2. These compounds could be used for the treatment of obesity, pain, as well as various immune system, cell signaling, cardiovascular, and psychotic disorders.

Anatomy and immunochemical characterization of the non-arterial peptidergic diffuse dural innervation of the rat and Rhesus monkey: Implications for functional regulation and treatment in migraine

Objective

The interplay between neuronal innervation and other cell types underlies the physiological functions of the dura mater and contributes to pathophysiological conditions such as migraine. We characterized the extensive, but understudied, non-arterial diffuse dural innervation (DDI) of the rat and Rhesus monkey.

Methods

We used a comprehensive integrated multi-molecular immunofluorescence labeling strategy to extensively profile the rat DDI and to a lesser extent that of the Rhesus monkey.

Results

The DDI was distributed across a dense, pervasive capillary network and included free nerve endings of peptidergic CGRP-expressing C fibers that were closely intertwined with noradrenergic (NA) sympathetic fibers and thin-caliber nonpeptidergic “C/Aδ” fibers. These newly identified C/Aδ fibers were unmyelinated, like C fibers, but expressed NF200, usually indicative of Aδ fibers, and uniquely co-labeled for the CGRP co-receptor, RAMP1. Slightly-larger caliber NF200-positive fibers co-labeled for myelin basic protein (MBP) and terminated as unbranched corpuscular endings. The DDI peptidergic fibers co-labeled for the lectin IB4 and expressed presumably excitatory α1-adrenergic receptors, as well as inhibitory 5HT1D receptors and the delta opioid receptor (δOR), but rarely the mu opioid receptor (µOR). Labeling for P2X3, TRPV1, TRPA1, and parasympathetic markers was not observed in the DDI.

Interpretation

These results suggest potential functional interactions, wherein peptidergic DDI fibers may be activated by stress-related sympathetic activity, resulting in CGRP release that could be detected in the circulation. CGRP may also activate nonpeptidergic C/Aδ fibers that are likely mechanosensitive or polymodal, leading to activation of post-synaptic pain transmission circuits. The distribution of α1-adrenergic receptors, RAMP1, and the unique expression of the δOR on CGRP-expressing DDI fibers suggest strategies for functional modulation and application to therapy.

Neuronal differentiation in the developing human spinal ganglia

The spatiotemporal developmental pattern of the neural crest cells differentiation toward the first appearance of the neuronal subtypes was investigated in developing human spinal ganglia (SG) between the fifth and tenth developmental week using immunohistochemistry and immunofluorescence methods. First neurofilament-200- (NF200, likely myelinated mechanoreceptors) and isolectin-B4-positive neurons (likely unmyelinated nociceptors) appeared already in the 5/6th developmental week and their number subsequently increased during the progression of development. Proportion of NF200-positive cells was higher in the ventral parts of the SG than in the dorsal parts, particularly during the 5/6th and 9/10th developmental weeks (Mann-Whitney, P = 0.040 and P = 0.003). NF200 and IB4 colocalized during the whole investigated period. calcitonin gene-related peptide (CGRP; nociceptive responses), vanilloid receptor-1 (VR1; polymodal nociceptors), and calretinin (calcium signaling) cell immunoreactivity first appeared in the sixth week and eighth week, respectively, especially in the dorsal parts of the SG. VR1 and CGRP colocalized with NF00 during the whole investigated period. Our results indicate the high potential of early differentiated neuronal cells, which slightly decreased with the progression of SG differentiation. On the contrary, the number of neuronal subtypes displayed increasing differentiation at later developmental stage. The great diversity of phenotypic expression found in the SG neurons is the result of a wide variety of influences, occurring at different stages of development in a large potential repertory of these neurons. Understanding the pathway of neural differentiation in the human, SG could be important for the studies dealing with the process of regeneration of damaged spinal nerves or during the repair of pathological changes within the affected ganglia. Anat Rec, 299:1060-1072, 2016. © 2016 Wiley Periodicals, Inc.