Selective Analogues Research Articles

Effect of Thyromimetic GC-1 Selective Signaling on Reproductive and Lactational Performance in the Hypothyroid Rat

Introduction: The potential of the thyroid hormone receptor β (TRβ1) selective analog GC-1 has been widely proven in animal models and humans. However, its effect on the reproductive stage of the female rat has not been evaluated. Methods: The effect of the administration of GC-1 or equimolar doses of triiodothyronine (T3) was evaluated on the reproductive performance of the hypothyroid female rat and the indirect effect on pup thyroid status, weight, and survival. Results: Hypothyroidism reduced the number of embryos implanted in the uterus, whereas T3 and GC-1 treatment in hypothyroid females reestablished the number of implanted embryos to normal. Initiation of labor was delayed by hypothyroidism, and T3 replacement treatment reinstated the normal timing of parturition. The administration of GC-1 alone to the lactating mother did not affect pup survival, weight, or thyroidal status. Conclusions: Our findings show the differential effect of thyroid hormone selective signaling during gestation and the indirect exposure of the pups; we also emphasize the plausible use of GC-1 for treatment of hypothyroid mothers during the lactation period.

The value of [68Ga]Ga-DOTA-TATE PET/CT in diagnosis and management of suspected pituitary tumors

BackgroundGallium 68-tetraazacyclododecane-tetraacetic acid-octreotate ([68Ga]Ga-DOTA-TATE) is a selective somatostatin analogue ligand, which shows increased affinity for somatostatin receptor subtype (SSTR) 2 and has been used routinely for imaging neuroendocrine tumors with PET/CT. We investigated the utility of [68Ga]Ga-DOTA-TATE positron emission tomography/computed tomography (PET/CT) in patients with suspected pituitary pathology. We reviewed imaging for twenty consecutive patients (8 men, 12 women, mean age of 48.2, range 14–78) with suspected pituitary pathology who were referred for [68Ga]Ga-DOTA-TATE PET/CT.ResultsNine patients presented with recurrent Cushing’s syndrome following surgical resection of pituitary adenomas due to recurrent Cushing’s disease (seven patients) and ectopic ACTH secreting tumor (2 patients). All seven patients with recurrent Cushing’s disease showed positive pituitary [68Ga]Ga-DOTA-TATE uptake while both cases of ectopic hormonal secretion had absented pituitary uptake. In 1 of these 2 patients, [68Ga]Ga-DOTA-TATE was able to localize the source of ectopic ACTH tumor.Six patients presented de novo with Cushing’s due to ectopic ACTH secretion; [68Ga]Ga-DOTA-TATE PET/CT was able to localize ectopic tumors in six of eight patients (3 lungs, 2 pancreases, 1 mid-gut)There was high uptake [68Ga]Ga-DOTA-TATE in 3 cases of recurrent central hyperthyroidism (SUVmax 6.6–14.3) and 2 cases of prolactinoma (SUVmax 5.5 and 11.3).ConclusionAbsent [68Ga]Ga-DOTA-TATE activity in the pituitary fossa is useful in excluding pituitary disease in recurrent Cushing’s. Recurrent pituitary thyrotropinomas and prolactinomas showed moderate to high pituitary activity. In addition, in Cushing’s syndrome, [68Ga]Ga-DOTA-TATE is useful for detection of ectopic sources of ACTH production, especially where anatomic imaging is negative.

Novel daidzein molecules exhibited anti-prostate cancer activity through nuclear receptor ERβ modulation, in vitro and in vivo studies

Eight novel ERβ selective daidzein analogues (NCE1-8) were synthesized and their anti-cancer activity was evaluated by in vitro and in vivo methods. Cytotoxicity study, Receptor binding studies, Luciferase assay, cMYC & Cyclin D1 expression and Caspase 3, 8 & 9 activities were measured to ascertain the anticancer activity and mechanism. Uterotropic, anti-androgenic and anti-tumour activities were performed in rodents. The results revealed that NCEs produced anti-prostate cancer activity in DU145, LNCaP and PC3 cell lines and 50% more active than genistein. NCEs was significantly down-regulated cMYC & Cyclin D1 genes and elevated caspase 3 & 9 levels and did not show any difference in uterotropic, anti-androgenic activities. The tumour weight was also reduced. The NCE 1 and 2 have shown ERβ selectivity in receptor binding studies. Daidzein with methyl substitution at R or R1 position exhibited more ERβ selectivity and could be considered as lead molecules for anti-prostate cancer activity.

A novel selective mitochondrial-targeted curcumin analog with remarkable cytotoxicity in glioma cells.

Naturally occurring polyphenol curcumin (4) or demethoxycurcumin (5) and their synthetic derivatives display promising anticancer activities. However, their further development is limited by low bioavailability and poor selectivity. Thus, a mitochondria-targeted compound 14 (DMC-TPP) was prepared in the present study by conjugating a triphenylphosphine moiety to the phenolic hydroxyl group of demethoxycurcumin to enhance its bioavailability and treatment efficacy. The invitro biological experiments of DMC-TPP showed that it not only displayed higher cytotoxicity as compared with its parent compound 5, but also exhibited superior mitochondria accumulation ability. Glioma cells were more sensitive to DMC-TPP, which inhibited the proliferation of U251cells with an IC50 of 0.42μM. The mechanism studies showed that DMC-TPP triggers mitochondria-dependent apoptosis, caused by caspase activation, production of reactive oxygen species (ROS) and decrease of mitochondrial membrane potential (MMP). In addition, DMC-TPP efficiently inhibited cellular thioredoxin reductase, which contributed to its cytotoxicity. Significantly, DMC-TPP delayed tumor progression in a mouse xenograft model of human glioma cancer. Taken together, the potent invitro and invivo antitumor activity of DMC-TPP warrant further comprehensive evaluation as a novel anti-glioma agent.

Insight into mithramycin disruption of ETS transcription leads to improved understanding of more selective analogs

Fusion products with the ETS family of transcription factors play critical roles in the etiology of several cancers. In this issue of Structure, Hou etal. (2020) provide insight into allosteric mechanisms by which mithramycin and its analogs perturb protein-DNA interactions in higher-order complexes at a DNA enhancer site.

Correction to: Elucidating the therapeutic activity of selective curcumin analogues: DFT-based reactivity analysis

Correction to: Elucidating the therapeutic activity of selective curcumin analogues: DFT-based reactivity analysis

The Integrated Effects of Brivaracetam, a Selective Analog of Levetiracetam, on Ionic Currents and Neuronal Excitability.

Brivaracetam (BRV) is recognized as a novel third-generation antiepileptic drug approved for the treatment of epilepsy. Emerging evidence has demonstrated that it has potentially better efficacy and tolerability than its analog, Levetiracetam (LEV). This, however, cannot be explained by their common synaptic vesicle-binding mechanism. Whether BRV can affect different ionic currents and concert these effects to alter neuronal excitability remains unclear. With the aid of patch clamp technology, we found that BRV concentration dependently inhibited the depolarization-induced M-type K+ current (IK(M)), decreased the delayed-rectifier K+ current (IK(DR)), and decreased the hyperpolarization-activated cation current in GH3 neurons. However, it had a concentration-dependent inhibition on voltage-gated Na+ current (INa). Under an inside-out patch configuration, a bath application of BRV increased the open probability of large-conductance Ca2+-activated K+ channels. Furthermore, in mHippoE-14 hippocampal neurons, the whole-cell INa was effectively depressed by BRV. In simulated modeling of hippocampal neurons, BRV was observed to reduce the firing of the action potentials (APs) concurrently with decreases in the AP amplitude. In animal models, BRV ameliorated acute seizures in both OD-1 and lithium-pilocarpine epilepsy models. However, LEV had effects in the latter only. Collectively, our study demonstrated BRV’s multiple ionic mechanism in electrically excitable cells and a potential concerted effect on neuronal excitability and hyperexcitability disorders.

AM833 Is a Novel Agonist of Calcitonin Family G Protein-Coupled Receptors: Pharmacological Comparison with Six Selective and Nonselective Agonists.

Obesity and associated comorbidities are a major health burden, and novel therapeutics to help treat obesity are urgently needed. There is increasing evidence that targeting the amylin receptors (AMYRs), heterodimers of the calcitonin G protein-coupled receptor (CTR) and receptor activity-modifying proteins, improves weight control and has the potential to act additively with other treatments such as glucagon-like peptide-1 receptor agonists. Recent data indicate that AMYR agonists, which can also independently activate the CTR, may have improved efficacy for treating obesity, even though selective activation of CTRs is not efficacious. AM833 (cagrilintide) is a novel lipidated amylin analog that is undergoing clinical trials as a nonselective AMYR and CTR agonist. In the current study, we have investigated the pharmacology of AM833 across 25 endpoints and compared this peptide with AMYR selective and nonselective lipidated analogs (AM1213 and AM1784), and the clinically used peptide agonists pramlintide (AMYR selective) and salmon CT (nonselective). We also profiled human CT and rat amylin as prototypical selective agonists of CTR and AMYRs, respectively. Our results demonstrate that AM833 has a unique pharmacological profile across diverse measures of receptor binding, activation, and regulation. SIGNIFICANCE STATEMENT: AM833 is a novel nonselective agonist of calcitonin family receptors that has demonstrated efficacy for the treatment of obesity in phase 2 clinical trials. This study demonstrates that AM833 has a unique pharmacological profile across diverse measures of receptor binding, activation, and regulation when compared with other selective and nonselective calcitonin receptor and amylin receptor agonists. The present data provide mechanistic insight into the actions of AM833.

Elucidating the therapeutic activity of selective curcumin analogues: DFT-based reactivity analysis

Density functional theory (DFT) has been employed to study the structure, stability and reactivity of curcumin and some of its important analogues by computing HOMO-LUMO energy gap (H-L gap), ionization potential (IP), electron affinity (EA), chemical potential (μ), chemical hardness (η), electrophilicity index (ω) and density of states (DOS). In this study, curcumin is found to be more reactive in dimethyl sulfoxide (DMSO) solvent than in the gas phase in both of its enol and keto isomeric forms. Next, reactivities of the keto-based curcumin analogues are found to follow the order of 1,5-bis(3,4-dimethoxyphenyl)penta-1,4-dien-3-one (GO-035) > 1,5-bis(3,4,5-trimethoxyphenyl)penta-1,4-dien-3-one (GO-Y016) > 1,5-bis[3,5-bis(methoxymethoxy)phenyl]penta-1,4-dien-3-one (GO-Y031) > 1,5-bis[3,5-dimethoxy-4-(methoxymethoxy)phenyl]penta-1,4-dien-3-one (GO-Y030) > dibenzalacetone (DBA) in both gas and DMSO solvent phases. However, there is enhancement in reactivities of the complexes in DMSO solvent from those in the gas phase. The reactivity order is observed on the basis of H-L gap, IP, μ, η and DOS analyses. Moreover, GO-Y030, GO-Y031 and DBA possess similar electrophilic behaviours as indicated by their comparable EA and ω values, while GO-Y016 and GO-035 behave as the strongest and the weakest electrophiles. Furthermore, the nature of the reactive sites in the curcumin analogues has been identified via local reactivity descriptors and the molecular electrostatic potential (MEP) maps, results of which are consistent with the molecular orbital analyses.

Abstract PS18-46: Inhibition of breast cancer stem cells in 2- and 3-dimensional culture by novel salinomycin analogs

Abstract Breast cancer remains one of the leading cancers among women and an estimated 90% of breast cancer deaths are due to metastasis. Cancer stem cells (CSCs) are a sub-population of cancer cells which are responsible for its initiation, progression and metastasis. CSCs are resistant to conventional chemo- and radio-therapies and therefore therapeutic strategies targeting CSCs hold great potential for novel advances in cancer treatment. Salinomycin (SAL) is a naturally occurring polyether ionophore antibiotic which was shown to effectively target breast CSCs. A library of 17 novel SAL analogs was synthesized and screened to identify compounds with improved selectivity against breast cancer stem cells. SAL analogs were either single modified esters or amides in the C1 position or double-modified C20-oxo derivatives. Eight single- and two double-modified analogs were more potent (IC50 range of 1.13 ± 0.19 to 3.93 ± 0.39 µM) towards the breast cancer cell line MDA-MB-231 compared to parent SAL (IC50 of 4.90 ± 1.60 µM). These analogs induced DNA fragmentation suggestive of apoptotic cell death. Compounds 2 (butyl ester analog of SAL) and 17 (double-modified C20-oxosalinomycin with benzhydroxamic acid) have been chosen for follow-up screening due to their improved activity and selectivity versus parent SAL. This included clonogenic assays to assess the ability of the compounds to affect cell renewal, and wound healing assays to assess cell migratory properties. In both assays, compound 17 showed superior properties over SAL. Furthermore, analog 17 showed improved targeting of breast CSCs in both cell monolayer and organoid culture as assessed in assays measuring the CD44+/CD24- stem cell sub-population. Analogs and parent compound were further studied examining (ADP-ribose) polymerase (PARP) cleavage and Bcl-2 levels by immunoblotting. All three compounds induced loss of 116 kDa PARP expression within 48h, with the highest effect induced by analog 17. In addition, treatment with compound 17 caused a decrease in Bcl-2 expression as early as 24 h. Select analogs were next screened against the NCI-60 Human Tumor Cell Line Panel. The described above double-modified analog was found to be more potent than SAL towards all 6 breast cancer cell lines in the panel as well as other tumor types. The present findings highlight the therapeutic potential of SAL analogs towards breast stem cells and support further research and clinical development of these compounds. Funding: The present study was funded by grants (to AM and TCC) from the Arkansas Breast Cancer Research Program. Testing was performed by the Developmental Therapeutics Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute, http://dtp.cancer.gov. Citation Format: Alicja Joanna Urbaniak, Megan R. Reed, Michał Antoszczak, Michał Sulik, Adam Huczyński, Robert L. Eoff, Melanie C. MacNicol, Timothy C. Chambers, Angus M. MacNicol. Inhibition of breast cancer stem cells in 2- and 3-dimensional culture by novel salinomycin analogs [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS18-46.

On the Number of Empty Cells in a Non-Homogeneous Allocation Scheme

It considered a non-homogeneous allocation scheme of distinguishable particles by different cells. We proved gaussian and Poisson limit theorems for the number of empty cells from the first $$K$$ cells. These results we apply to study the type I error and the type II error in select analogs of the empty box test.

Design, Synthesis and In Vitro Investigation of Novel Basic Celastrol Carboxamides as Bio-Inspired Leishmanicidal Agents Endowed with Inhibitory Activity against Leishmania Hsp90.

The natural triterpene celastrol (CE) is here used as lead compound for the design and synthesis of a panel of eleven CE carboxamides that were tested in vitro for their growth inhibitory activity against Leishmania infantum and L. tropica parasites. Among them, in vitro screening identified four basic CE carboxamides endowed with nanomolar leishmanicidal activity, against both the promastigotes and the intramacrophage Leishmania amastigotes forms. These compounds also showed low toxicity toward two human (HMEC-1 and THP-1) and one murine (BMDM) cell lines. Interestingly, the most selective CE analogue (compound 3) was also endowed with the ability to inhibit the ATPase activity of the Leishmania protein chaperone Hsp90 as demonstrated by the in vitro assay conducted on a purified, full-length recombinant protein. Preliminary investigations by comparing it with the naturally occurring Hsp90 active site inhibitor Geldanamycin (GA) in two different in vitro experiments were performed. These promising results set the basis for a future biochemical investigation of the mode of interaction of celastrol and CE-inspired compounds with Leishmania Hsp90.

Conformational selection of vasopressin upon V1a receptor binding

The neuropeptide vasopressin (VP) and its three G protein-coupled receptors (V1aR, V1bR and V2R) are of high interest in a wide array of drug discovery programs. V1aR is of particular importance due to its cardiovascular functions and diverse roles in the central nervous system. The structure–activity relationships underpinning ligand-receptor interactions remain however largely unclear, hindering rational drug design. This is not least due to the high structural flexibility of VP in its free as well as receptor-bound states. In this work, we developed a novel approach to reveal features of conformational selectivity upon VP-V1aR complex formation. We employed virtual screening strategies to probe VP’s conformational space for transiently adopted structures that favor binding to V1aR. To this end, we dissected the VP conformational space into three sub-ensembles, each containing distinct structural sets for VP’s three-residue C-terminal tail. We validated the computational results with experimental nuclear magnetic resonance (NMR) data and docked each sub-ensemble to V1aR. We observed that the conformation of VP’s three-residue tail significantly modulated the complex dissociation constants. Solvent-exposed and proline trans-configured VP tail conformations bound to the receptor with three-fold enhanced affinities compared to compacted or cis-configured conformations. The solvent-exposed and more flexible structures facilitated unique interaction patterns between VP and V1aR transmembrane helices 3, 4, and 6 which led to high binding energies. The presented “virtual conformational space screening” approach, integrated with NMR spectroscopy, thus enabled identification and characterization of a conformational selection-type complex formation mechanism that confers novel perspectives on targeting the VP-V1aR interactions at the level of the encounter complex – an aspect that opens novel research avenues for understanding the functionality of the evolutionary selected conformational properties of VP, as well as guidance for ligand design strategies to provide more potent and selective VP analogues.

Novel BuChE-IDO1 inhibitors from sertaconazole: Virtual screening, chemical optimization and molecular modeling studies

In our effort towards the identification of novel BuChE-IDO1 dual-targeted inhibitor for the treatment of Alzheimer’s disease (AD), sertaconazole was identified through a combination of structure-based virtual screening followed by MM-GBSA rescoring. Preliminary chemical optimization was performed to develop more potent and selective sertaconazole analogues. In consideration of the selectivity and the inhibitory activity against target proteins, compounds 5c and 5d were selected for the next study. Further modification of compound 5c led to the generation of compound 10g with notably improved selectivity towards BuChE versus AChE. The present study provided us with a good starting point to further design potent and selective BuChE-IDO1 inhibitors, which may benefit the treatment of late stage AD.

High Selectivity of an α-Conotoxin LvIA Analogue for α3β2 Nicotinic Acetylcholine Receptors Is Mediated by β2 Functionally Important Residues.

The α3β2 and α3β4 nicotinic acetylcholine receptors (nAChRs) are widely expressed in the central and peripheral nervous systems, playing critical roles in various physiological processes and in such pathologies as addiction to nicotine and other drugs of abuse. α-Conotoxin LvIA, which we previously isolated from Conus lividus, modestly discriminates α3β2 and α3β4 rat nAChRs exhibiting a ∼17-fold tighter binding to the former. Here, alanine scanning resulted in two more selective analogues [N9A]LvIA and [D11A]LvIA, the former having a >2000-fold higher selectivity for α3β2. The determined crystal structures of [N9A]LvIA and [D11A]LvIA bound to the acetylcholine-binding protein (AChBP) were followed by homologous modeling of the complexes with the α3β2 and α3β4 nAChRs and by receptor mutagenesis, which revealed Phe106, Ser108, Ser113, and Ser168 residues in the β2 subunit as essential for LvIA binding. These results may be useful for the design of novel compounds of therapeutic potential targeting α3β2 nAChRs.

Contemporary use of Selexipag in pulmonary arterial hypertension associated with congenital heart disease: a case series

BackgroundThere are significant risks of parenteral prostacyclin use in patients with pulmonary arterial hypertension associated with congenital heart disease (PAH-CHD), which may limit their use. Selexipag is an oral, selective prostacyclin analogue that has been shown to reduce disease progression and improve exercise capacity in patients with PAH-CHD. Administering Selexipag in patients with PAH-CHD could potentially overcome some of the risks of parenteral therapy while improving clinical outcomes. Case summaryWe report five cases highlighting the clinical uses of Selexipag in patients with PAH-CHD. In the first two cases, Selexipag was initiated as part of a Treat-to-close strategy. In the third case, initiation of Selexipag improved symptoms and objective exercise capacity in a patient with Eisenmenger syndrome. In the fourth and fifth cases, rapid cross-titration protocols were used to transition from parenteral prostacyclins to Selexipag. In the fourth case, Selexipag was initiated in the context of significant side effects limiting parenteral prostacyclin use. In the fifth case, Selexipag was used to down-titrate from parenteral prostacyclins following closure of a sinus venosus atrial septal defect and redirection of anomalous pulmonary veins.DiscussionSelexipag is a promising oral therapy for patients with at various stages of the spectrum of PAH-CHD to improve symptoms, exercise capacity and, in some cases, haemodynamics. Our cases also highlight practical aspects of Selexipag use including targeting the individualized maximally tolerated dose for each patient, managing side effects and managing dose interruptions.

Potent antiproliferative activity of bradykinin B2 receptor selective agonist FR-190997 and analogue structures thereof: A paradox resolved?

Βradykinin stimulation of B2 receptor is known to activate the oncogenic ERK pathway and overexpression of bradykinin receptors B1 and B2 has been reported to occur in glioma, colorectal and cervical cancers. B1R and B2R antagonists have been shown to reverse tumor proliferation and invasion. Paradoxically, B1R and B2R agonism has also been reported to elicit antiproliferative benefits. In order to complement the data accumulated to date with the natural substrate bradykinin and peptidic B2R antagonists, we decided to examine for the first time the response elicited by B2R stimulation in breast cancer lines with a non-peptidic small molecule B2R agonist. We synthesized and assessed the highly selective and potent B2R partial agonist FR-190997 in MCF-7 and MDA-MBA-231 breast cancer lines and found it possessed significant antiproliferative activity (IC50 2.14 and 0.08 μΜ, respectively). The modular nature of FR-190997 allowed us to conduct a focused SAR study and discover compound 10 which exhibits subnanomolar antiproliferative activity (IC 50 0.06 nΜ) in the TNBC MDA-MBA-231 cell line. This performance surpasses, in most cases by several orders of magnitude, those of established anticancer agents and FDA-approved breast cancer drugs. In line with the established literature we suggest that this remarkable activity precipitates from a dual mode of action involving agonist-induced receptor internalization/degradation combined with sequestration of functional intracellular B2 receptors and inhibition of the associated endosomal signaling. The latter mode may be realized by appropriate ligands regardless of B2R agonist/antagonist designation which only relates to membrane residing GCPRs. Under this prism the controversy over the antiproliferative effects of B2 agonists and antagonists is potentially neutralized.

Gas chromatography with dual cold electron ionization mass spectrometry and vacuum ultraviolet detection for the analysis of phenylethylamine analogues

Identification of phenethylamine (PEA) analogues is of great importance and requires analytical methods of high specificity. Forensic drug analysis is often performed by gas chromatography (GC) most commonly coupled with mass spectrometric (MS) detection. However, analysis of labile compounds is problematic with classical electron ionization (EI)-MS, and positional isomers may be difficult to differentiate by MS. Cold electron ionization (cold EI) improves molecular ion relative intensity by reducing the analyte vibrational energy prior to ionization. Vacuum ultraviolet (VUV) is a gas phase technique that can provide complementary selectivity to MS for identification. In this study, cold EI-MS was used in parallel with VUV detection for the analysis of select PEA analogues and positional isomers. Molecular ion relative intensity was increased for nearly all compounds included in this study. Principal component analysis demonstrated that VUV is more successful at distinguishing between positional isomers than MS. A library database of VUV spectra was set up to identify compounds, which was later used to deconvolute spectra of coeluting compounds. Detection limits for VUV are lower than those of MS with cold-EI, where VUV is capable of reaching sub-microgram per milliliter levels. Linearity tests on VUV showed high correlation coefficients (R2 > 0.999) for close to or over and order-of-magnitude dynamic range.

Machine Learning-Based Hybrid Precoding With Low-Resolution Analog Phase Shifters

In this letter, inspired by the cross-entropy (CE) optimization in machine learning, we propose a CE-based algorithm for hybrid precoding with low-resolution analog phase shifters in millimeter wave (mmWave) multi-input multi-output (MIMO) systems. The main idea is to generate some candidate analog precoders according to a series of pre-defined probability distributions and select partial analog precoders as elites to update the probability distributions. Through iteration, the probability distributions will converge to a stable state and the optimal precoders can be obtained with a sufficiently high probability. Furthermore, we extend the proposed algorithm to multi-user hybrid precoding. The simulation results demonstrate that the proposed algorithm can achieve near-optimal performance of the fully-digital precoding with lower computational complexity than other near-optimal algorithms.

α-Conotoxin Peptidomimetics: Probing the Minimal Binding Motif for Effective Analgesia.

Several analgesic α-conotoxins have been isolated from marine cone snails. Structural modification of native peptides has provided potent and selective analogues for two of its known biological targets—nicotinic acetylcholine and γ-aminobutyric acid (GABA) G protein-coupled (GABAB) receptors. Both of these molecular targets are implicated in pain pathways. Despite their small size, an incomplete understanding of the structure-activity relationship of α-conotoxins at each of these targets has hampered the development of therapeutic leads. This review scrutinises the N-terminal domain of the α-conotoxin family of peptides, a region defined by an invariant disulfide bridge, a turn-inducing proline residue and multiple polar sidechain residues, and focusses on structural features that provide analgesia through inhibition of high-voltage-activated Ca2+ channels. Elucidating the bioactive conformation of this region of these peptides may hold the key to discovering potent drugs for the unmet management of debilitating chronic pain associated with a wide range of medical conditions.