Molecular Pharmacology

The full efficacy range of ligands at CB1 and CB2 (i.e., inverse agonists, neutral agonists, partial agonists, full agonists, and high-efficacy agonists) has been reported collectively across numerous laboratories and assay platforms. Canonical Gi/o and {beta}-arrestin signaling have each been suggested to shape physiological effects differently via different classes of cannabinoid ligands. These prior efficacy classifications, however, were obtained in multiple assay systems, often using indirect, amplified readouts and different reference agonists, making them difficult to compare across ligands. Here we profiled a structurally diverse panel of 22 cannabinoid ligands: synthetic cannabinoid receptor agonists (SCRAs), {Delta}-tetrahydrocannabinol ({Delta}-THC) analogues, endocannabinoid analogues, and antagonists/inverse agonists at CB1 and CB2 receptors using bioluminescence resonance energy transfer (BRET) assays, measuring Gi1 engagement and {beta}-arrestin 2 recruitment and normalizing every response to the reference full agonist CP55,940. At CB1, SCRAs and {Delta}-THC analogues acted as high-efficacy agonists. At CB1, these high-efficacy agonists were also highly efficacious in {beta}-arrestin 2 recruitment. Across the panel, the most consistent trend was a loss of agonist efficacy from CB1 to CB2. Among antagonists, inverse agonists suppressed constitutive CB1 activity more than neutral antagonists. Together, these CP55,940-normalized measurements provide a common efficacy scale and a framework for interpreting pharmacodynamics of CB1 and CB2 cannabinoid receptors.

G protein-gated inwardly rectifying potassium (GIRK2) channels regulate neuronal excitability and are implicated in neurodevelopmental disorders. A rare KCNJ6 variant, G154C (hGIRK2G154C), was identified in a patient with mild Keppen-Lubinsky syndrome features, contrasting with severe phenotypes linked to other selectivity filter mutations. Here we combined molecular dynamics simulations and patch-clamp electrophysiology to characterize the hGIRK2G154C mutant, revealing a widened selectivity filter that resulted in loss of potassium selectivity, aberrant sodium permeation, and loss of inward rectification, indicating a severe gain-of-function phenotype. An in silico and electrophysiological drug screen identified FDA-approved compounds, including nefazodone and eletriptan, that potently inhibited GIRK2 and GIRK2G154C through distinct blocking mechanisms. These findings elucidate the structural and functional impact of the G154C mutation and highlight potential pharmacological tools and therapeutic candidates for the treatment of GIRK2 channelopathies.

Peroxisome proliferator-activated receptor (PPAR) is a nuclear receptor that plays a central role in metabolic adaptation by regulating gene expression programs involved in lipid utilization and energy homeostasis. Although the hepatic functions of PPAR and its target genes are well characterized, less is known about its transcriptional activity in extrahepatic tissues. Pemafibrate (K-877), a selective PPAR modulator (SPPARM), is a high-affinity PPAR ligand with improved potency and selectivity compared with conventional fibrates. Here, we investigated pemafibrate-induced tissue-specific transcriptional responses comparing wild type and whole-body PPAR-deficient littermate mice. Twelve-week-old male PPAR+/+ and PPAR-/- mice were treated daily with pemafibrate (0.1 mg/kg) or vehicle by oral gavage for 14 days. We performed genome-wide transcriptomic analyses in the liver, jejunum, kidney, soleus muscle, and BAT. Pemafibrate-induced transcriptional changes were entirely dependent on PPAR, as no differentially expressed genes were detected in PPAR-/- mice. The magnitude and nature of the response were tissue-specific, with the strongest transcriptional effects observed in the liver and jejunum, whereas the kidney, soleus muscle, and BAT showed limited responses. In the liver, pemafibrate primarily induced the expression of genes involved in fatty acid metabolism, mitochondrial function, and energy production. In the jejunum, pemafibrate activated lipid metabolic programs together with tissue-specific pathways related to cellular homeostasis. Collectively, our findings show that pemafibrate is a highly selective PPAR activator with a preferential transcriptional activity in the liver and intestine after oral administration. This study provides a resource for defining tissue-specific PPAR-responsive gene networks and expands our understanding of PPAR functions beyond the liver.

{beta}-arrestins 1 and 2 are intracellular adaptor proteins that regulate the subcellular localisation and signalling of GPCRs including Parathyroid Hormone Receptor 1 (PTH1R), which produces {beta}-arrestin-dependent signalling that may selectively stimulate bone anabolism. {beta}-arrestins can themselves be regulated by post-translational modifications including phosphorylation, which dictates the translocation and signalling of the few GPCRs studied in this context to date. We aimed to investigate whether phosphorylation of {beta}-arrestins modulates their subcellular translocation in response to PTH1R activation. Translocation of {beta}-arrestins to the plasma membrane and early endosomes was quantified using BRET biosensors and immunocytochemistry with high content analysis. Phosphoknockout or phosphomimetic mutations were introduced to previously demonstrated phosphorylation sites in {beta}-arrestins 1 and 2, initially in bulk to assess overall effects. Plasma membrane translocation was altered only subtly, whereas early endosome translocation was markedly reduced for both mutations but to a greater degree for the phosphomimetic. Contributions of individual or paired sites were assessed by restoration to wildtype from the bulk phosphomimetic mutants. Dual restoration of S13 and T275 in {beta}-arrestin 1, or the analogous sites in {beta}-arrestin 2, restored the greatest degrees of early endosomal translocation, with complete restoration for {beta}-arrestin 1 and partial for {beta}-arrestin 2. Restoration of other sites had minimal or no effect. Dephosphorylation therefore appears to be required for PTH1R-stimulated {beta}-arrestin early endosomal translocation, with different phosphorylation sites implicated than some other GPCRs. These findings raise the possibility of differential {beta}-arrestin regulation by distinct stimuli which may have implications in therapeutic targeting of {beta}-arrestin-dependent pathways.

Schizophrenia is a debilitating neuropsychiatric disease that lacks effective treatments for many symptom domains including negative, cognitive and sleep disturbances. Lack of clear disease etiology has hampered the development of new, effective treatments for the unmet needs of people with schizophrenia. Large scale human genetics have identified rare loss of function mutations that substantially increase risk of developing schizophrenia, including in GRIA3, the gene that encodes the GluA3 receptor subunit of the AMPA receptor (AMPAR). Several drug discovery programs have been aimed at developing AMPAR positive allosteric modulators (PAMs) as a novel treatment for schizophrenia. Despite intense drug discovery efforts, there are no FDA approved AMPAR PAMs. We therefore hypothesized that selectively targeting GluA3, the AMPAR subunit implicated by human genetics, could yield a safer and more effective AMPAR PAM for the potential treatment of schizophrenia. Using a combination of medicinal chemistry, in vitro, and in vivo studies, we discovered BRD3290, a GluA3-preferring AMPAR PAM with reasonable potency in heterologous cells, as well as favorable tolerability and brain exposure. Peripheral administration of BRD3290 engaged an established AMPAR PAM target engagement biomarker but did not improve performance of wildtype mice in the novel object recognition task (NOR), in contrast to the nonselective AMPAR PAM PF-4778574, which improved mouse NOR. These findings suggest that the GluA3 selectivity profile of BRD3290 was insufficient to enhance cognitive function in this mouse NOR paradigm. This work highlights the challenges of AMPAR subtype-selective modulation and provides molecular insights into the ability to develop subtype-selective AMPAR PAMs. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/740780v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@1c14b74org.highwire.dtl.DTLVardef@140b2b3org.highwire.dtl.DTLVardef@942636org.highwire.dtl.DTLVardef@58bc24_HPS_FORMAT_FIGEXP M_FIG C_FIG

The neutrophil NADPH oxidase is activated by signals generated by formyl peptide receptor (FPR) agonists recognized by FPR1 (fMLF) and FPR2 (WKYMVM), respectively. Also, the antagonists cyclosporin H (specific for FPR1) and PBP10 (specific for FPR2) inhibit the NADPH oxidase activity when induced by the two peptide agonists. When bound to its receptor, the non-activating positive allosteric modulator Cmp58, specific for the free fatty acid 2 receptor (FFA2R), affects not only the response induced by agonists specific for FFA2R, but also the activating potency but not the efficacy of the two FPR activating peptides. Even though Cmp58 is without effect on the efficacy of the response induced by the FPR agonists, the inhibitory effect of the respective FPR specific antagonists is reduced. This sensitivity shift was reversed by an FFA2R specific antagonist suggesting that two different signals generated by the FPRs activate the NADPH oxidase. According to a receptor trans-regulation model, the activated FPRs generate signals that directly activate the NADPH oxidase and signals that activate the allosterically modulated FFA2Rs to elicit activation of the NADPH.

Allosteric modulation of G protein-coupled receptors (GPCR) is a rapidly advancing area of drug discovery with considerable therapeutic potential. In this study, we used various bioluminescence resonance energy transfer (BRET) assay configurations to investigate the differential activity of LY3154207, a dopamine D1 receptor (D1R)- positive allosteric modulator (PAM), in potentiating D1R-mediated signaling pathways. Our data showed that LY3154207 demonstrated clear bias toward {beta}-arrestin recruitment over G-protein engagement. Among the G-protein subtypes, LY3154207 preferentially potentiated Gs signaling induced by DA. Interestingly, when tested for its effect on the Gs-selective D1R agonist DHX and the Golf-selective agonist TAV, LY3154207 further enhanced the selectivity of these compounds, suggesting a probe-dependent effect. We also studied the structural mechanism underlying this subtype selectivity and found that W123 and R130 in the intracellular loop 2 (ICL2) of D1R were crucial for the activity of LY3154207. Furthermore, the N domain of the G-protein appeared to make minor contributions to this G-protein subtype selectivity of LY3154207. Lastly, our data demonstrated that LY3154207 induced cAMP production in the absence of the orthosteric ligand, indicating that this compound is an ago-PAM.

We published recently that one of the main constituents of cannabis products, cannabidiol (CBD), is an efficacious negative allosteric modulator (NAM) of the mu opioid receptor (MOR1) (Bosquez-Berger et al., 2023). Here, we investigated how the presence of cannabidiol (CBD) is associated with fentanyl (FEN) binding across MOR1 conformations. We performed molecular dynamics simulations of systems containing FEN alone or FEN+CBD in three mouse MOR1 conformational backgrounds: active-like 5C1M, inactive-like 4DKL, and a modeled Morph50 intermediate between the 5C1M and 4DKL conformations. Three independently seeded 200 ns trajectories were analyzed per model and condition (18 trajectories total), with the trajectory treated as the independent unit. Across the matched 0-200 ns window, consensus CBD contacts and CBD-associated changes in FEN contacts were strongly state dependent. Corrected intracellular TM3 to TM6 analyses separated the expected active-like, intermediate, and inactive-like backgrounds but did not identify a CBD-associated shift that was consistent across both geometric definitions and all three replicates. Equal-weight replicate-composite density maps preserved both the shared ligand distributions and this between-trajectory variability. These descriptive results support receptor-state-dependent CBD, FEN, MOR1 interactions while emphasizing the limited inferential power of three trajectories per condition.

Albumin binding can substantially alter the unbound concentration and apparent cellular potency of small-molecule anticancer agents. BAY-1816032 is a selective BUB1 kinase inhibitor with activity in malignant pleural mesothelioma, but its interaction with serum albumin has not been defined. This study combined intrinsic bovine serum albumin (BSA) fluorescence measurements, molecular docking, and cell-viability assays to examine whether albumin association influences BAY-1816032 activity. BAY-1816032 produced pronounced quenching of BSA fluorescence at low drug-to-protein molar ratios, and the quenching response was greater at mildly acidic pH than at mildly basic pH. Docking to BSA (PDB 4F5S) placed the top-ranked pose in Sudlow site I (subdomain IIA), with a Vina score of -7.8 kcal/mol and predicted hydrogen-bond contacts with Tyr149, Arg256, and Asp450. In NCI-H28, NCI-H2052, NCI-H2452, and AB12 mesothelioma cells, supplementation of 10% fetal bovine serum medium with 2% (w/v; 20 mg/mL) BSA shifted BAY-1816032 concentration-response curves to the right. Relative to 10% serum alone, IC50 values increased from 2.4 to 11.1 uM in H28, 3.6 to 22.0 uM in H2052, 2.0 to 4.9 uM in H2452, and 2.4 to 11.1 uM in AB12. These data support an albumin-dependent reduction in the freely available drug fraction and identify site I as the leading computational binding-site hypothesis. Because fluorescence-intensity and docking data do not independently establish a dissociation constant or quenching mechanism, direct unbound-fraction measurements and competitive displacement experiments are required for quantitative confirmation.

Background and Purpose: Among new psychoactive substances, synthetic cannabinoid receptor agonists (SCRAs) encompass considerable structural diversity and show wide variation in cannabinoid receptor 1 (CB1) potency and efficacy, but the molecular and receptor-interaction characteristics underlying these differences remain unclear. We assessed the pharmacological profiles of 16 SCRAs and examined structural features associated with differences in CB1 potency and efficacy. Experimental Approach: CB1 agonist activity was measured in a CB1-G15-based Ca2+ assay, and cataleptic effects were assessed in mice. Ligand-receptor interactions were characterized by molecular docking to an active-state CB1 structure. Principal component analysis (PCA) was applied to residue-level interaction profiles, and the resulting scores were tested for associations with CB1 potency and efficacy. Key Results: Potency and efficacy varied widely across cellular and animal assays, with several SCRAs exhibiting different pharmacological responses across the two experimental systems. PCA identified an interaction pattern whose PC1 scores were significantly associated with Emax but not EC50, with contributions from activation-related CB1 residues including the PHE200-TRP356 toggle switch. Molecular descriptor analysis likewise identified structural features significantly associated with in vitro and in vivo Emax. Conclusion and Implications: Our findings suggest that CB1 efficacy is associated with distinct receptor-interaction patterns among structurally diverse SCRAs. Combining functional pharmacology with receptor-level interaction analysis provides structural insight into SCRA efficacy and may help prioritize emerging compounds for further pharmacological and behavioral evaluation.

GPR27/SREB1 is a highly conserved orphan class A G-protein coupled receptor implicated in insulin production, metabolic regulation, tumour biology, neurodegeneration and L-lactate homeostasis, but its immediate second-messenger signalling remains poorly defined. We used single-cell Forster resonance energy transfer nanosensors to monitor cytosolic Ca2+ and cAMP in wild-type 3T3 MEF cells, CRISPR-Cas9 GPR27-knockout cells (GPR27KO) and GPR27-knockout cells transiently re-expressing FLAG-tagged GPR27 (GPR27-rescued). The GPR27 surrogate agonist 8535n (1 {micro}M) increased intracellular Ca2+ in wild-type and rescued cells but not in GPR27-knockout cells and produced no significant cAMP response in wild-type cells. Basal Ca2+ and cAMP levels were unaffected by GPR27 deletion. Extracellular L-lactate (2 mM) induced a GPR27-dependent increase in Ca2+ and cAMP in wild-type and rescued cells, but not in knockout cells, raising the possibility that L-lactate acts as an endogenous ligand or modulator of GPR27. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/743761v1_ufig1.gif" ALT="Figure 1"> View larger version (10K): org.highwire.dtl.DTLVardef@2af45dorg.highwire.dtl.DTLVardef@113e2corg.highwire.dtl.DTLVardef@8dea4org.highwire.dtl.DTLVardef@50ec49_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIGPR27 surrogate agonist 8535n increases intracellular Ca2+ but not cAMP in 3T3 cells. C_LIO_LIExtracellular L-lactate induces GPR27-dependent intracellular Ca2+ and cAMP increases in 3T3 cells. C_LIO_LIThese findings identify GPR27 as a putative candidate lactate sensor. C_LI

BackgroundMedulloblastoma is the most common malignant pediatric brain tumor. Although advances in conventional therapies have improved survival over the years, acquired drug resistance remains a major barrier to durable cure. As dysregulation of epigenetic mechanisms is increasingly recognized as a driver of medulloblastoma pathogenesis and therapeutic adaptation, targeting epigenetic vulnerabilities represents a promising strategy to overcome treatment resistance. MethodsWe generated vincristine-resistant medulloblastoma cell line models and performed chemical screening to identify therapeutically targetable vulnerabilities. Candidate hits were validated using transcriptomic analyses, chromatin immunoprecipitation, and CRISPR-mediated genetic ablation to define the molecular mechanisms underlying drug sensitivity. ResultsChemical screening identified multiple active epigenetic compound classes capable of resensitizing vincristine-resistant medulloblastoma cells, including histone methyltransferase inhibitors, histone deacetylase inhibitors, and bromodomain inhibitors. Among these, the CBP/p300 bromodomain inhibitor SGC-CBP30 emerged as the most potent sensitizer to vincristine. Transcriptomic profiling revealed that, while ABCB1 was among the most highly upregulated genes in resistant cells, SGC-CBP30 treatment selectively downregulated ABCC3 and ABCA4, an effect not observed in parental cells. Mechanistically, chromatin immunoprecipitation demonstrated enrichment of p300 and H3K27ac at the ABCC3 and ABCA4 promoters in resistant cells, which was markedly reduced following SGC-CBP30 treatment. Consistent with these findings, genetic ablation of CREBBP or EP300 phenocopied the effects of pharmacological inhibition. Analysis of patient datasets further demonstrated elevated CREBBP, EP300, and ABCC3 expression in SHH MB, with positive correlations between ABCC3 and both CREBBP and EP300, supporting the clinical relevance of this regulatory axis. ConclusionsTogether, our findings demonstrate that CBP/p300 activity contributes to acquired vincristine-resistance in medulloblastoma. Targeting this axis represents a promising strategy to overcome drug resistance and enhance the efficacy of vincristine-based chemotherapy particularly in the context of relapsed or refractory disease. PLAIN ENGLISH SUMMARYMedulloblastoma is the most common cancerous brain tumor in children. Although many children respond well to the treatment, some tumors become resistant to chemotherapy, making them much harder to treat. Understanding why this resistance develops could lead to better treatment options for children whose cancer returns or no longer respond to therapy. In this study, we created laboratory models of medulloblastoma that had become resistant to the chemotherapy drug vincristine. We then tested a collection of drugs to identify compounds, which would restore the cancer cells sensitivity to treatment. We have discovered that several drugs were effective, with one compound, called SGC-CBP30, showing particularly strong activity. We investigated how SGC-CBP30 works and found that it decreases the activity of genes that are linked to chemotherapy resistance. Using multiple complementary experimental approaches, we confirmed that this gene-regulating pathway plays an important role in helping medulloblastoma cells survive treatment. Our findings suggest that targeting this pathway could restore the effectiveness of chemotherapy in drug-resistant tumors. Although further research is needed before this approach can be used in patients, these results provide a promising foundation for developing new treatments for children with relapsed or treatment-resistant medulloblastoma.

Background: Subtype-selectivity predictions are scored against measured selectivity and judged against an assumed noise ceiling. We asked what an 2-adrenergic benchmark rewards and which controls change its interpretation. Research design and methods: On a frozen benchmark of 586 paired 2A/2C compounds we evaluated Glide SP docking, CNN rescoring, ligand-only fingerprint models, receptor descriptors and pose contacts, with dopamine D3/D2 as comparator, applying five controls: a measured ceiling, a cluster-identity null, a nonselective reference, a same-receptor floor and a trivial-descriptor baseline. Results: Five descriptors from SMILES reached Spearman 0.645, 72% of the measured ceiling, against 0.071 for Glide SP and 0.188 for CNN rescoring; receptor properties and pose contacts reduced to size under control, while a non-size signal of 0.258 survived. Measured rather than propagated noise raised that ceiling from 0.704 to 0.897; cluster identity alone reached R2 0.499 on D3/D2 and none on 2; a nonselective reference received +1.43 to +4.79 kcal/mol where zero is expected; and a same-receptor floor reached 1.77-fold against 1.88-fold across subtypes. Conclusions: Such benchmarks reward molecular size first; a method must exceed 0.645 before its score indicates structural reasoning. The controls are inexpensive; conclusions rest on two receptor pairs, a three-pair floor and static structures.

We have examined how ibogaine may enhance synaptic plasticity and neural repair. Extracellular efflux analysis showed that ibogaine (3, 10 or 30 M) produced a rapid (<5 minutes) and concentration-dependent suppression of mitochondrial function and glycolysis in mouse cortical neurons. Cell-based imaging demonstrated this metabolic inhibition was preceded by an elevation of the mitochondrial membrane potential and followed by increased mitochondrial reactive oxygen species levels. Like ibogaine, which blocks potassium channels, mitochondrial Kv1.3 channel (mitoKv1.3) inhibitors produce concordant changes over a similar timeframe. Following treatment with ibogaine (3, 10 or 30 M) for 4 hours, a marked concentration-dependent rebound of energy production occurred 20 hours later suggestive of metabolic preconditioning. Indeed, proteomic profiling showed that oral ibogaine (100 mg/kg) administration to female mice produced changes in spinal cord protein abundance indicative of increasing metabolic stress from 0.25-24 hours that resolved by 72 hours. This was accompanied by activation, inhibition and reactivation of synaptic plasticity and neural repair signaling pathways at 0.25, 4-24 and 72 hours, respectively. Hence, by inducing transient metabolic stress, ibogaine may re-open a neurodevelopmental window characterized by enhanced synaptic plasticity and neural repair. Ibogaine binds with high affinity to the sigma-2 receptor. Like mitoKv1-3 inhibitors and sigma-2 receptor ligands, ibogaine transiently elevated AMP-activated protein kinase (0.25 hours) and temporally suppressed mechanistic target of rapamycin and lipid synthesis pathways (0.25-24 hours) implicated in enhanced synaptic plasticity and neural repair. These findings suggest ibogaine rewires and repairs neural circuits by a metabolic preconditioning mechanism, perhaps involving mitoKv1.3 and the sigma-2 receptor.

Intestinal insect cells are integral to pharmacokinetic research, unfortunately they do not serve as cell models for more advanced studies comparable to transport studies typically conducted in mammalian models. To overcome this limitation, in this study, we developed a Caco-2 cell line that has been genetically modified to mimic insect-like characteristics, providing a robust insectified screening platform to monitor transport processes of xenobiotics. This platform consists of Wild Type (Pgpwild type) cells, an Pgp Knockout (PgpKO) line to eliminate endogenous background interference, and species-specific P-gp rescue lines. These rescue lines allow for the stable expression of human (Hs Pgp), cotton bollworm (Ha Pgp), and malaria mosquito (Ag Pgp) homologs, enabling a direct comparative analysis of efflux kinetics across different pesticide target and non-target biological systems. Functional validation using the substrate Digoxin confirmed high P-gp dependency within the platform. Methyl-parathion, an organophospate insecticide, was recognised and transported by both insect and human Pgps. This is consistent with the low mammalian selectivity of the compound. In contrast, Triflumezopyrim exhibited a high efflux ratio that remained remarkably stable even in the absence of MDR1, indicating that the uptake and pharmacokinetics of this compound are not Pgp-dependent. By successfully differentiating between transporter-specific and independent pathways these cell lines can serve as a high-fidelity screening tool for predicting novel pesticide selectivity and possibly validating the potential role of transporters in resistance. The system can be expanded and exploit also other transporters.

Gabapentin (GBP) and pregabalin (PGB) are widely used gabapentinoids. Previously, we have demonstrated, for the first time, that GBP and PGB modulate the nociceptive response to noxious heat in C. elegans at an optimal concentration. In the current study, we use C. elegans and paired thermal nociception assays with direct internal drug concentration measurements to characterize the pharmacokinetic (PK)/pharmacodynamic (PD) relationship of both compounds. Neither drug altered baseline mobility or quadrant preference, confirming that behavioral effects reflected genuine antinociceptive action. Both GBP and PGB produced dose- and time-dependent reductions in thermal avoidance, with 500 uM exposures generating a biphasic, V-shaped time course in which suppression of thermal sensitivity deepened before partially reversing. This partial reversal occurred later with PGB than with GBP. Internal concentrations confirmed dose-dependent absorption and retention for both drugs, yet at 500 uM, internal drug levels remained elevated through 360 min even as behavioral avoidance recovered, indicating that the recovery limb reflects active counter-regulation rather than passive clearance, consistent with previously reported transcriptional and proteomic signatures. Exposure-response profiles were notably flat, suggesting a saturable pharmacodynamic ceiling. Molecular modeling revealed conserved electronic pharmacophores supporting shared alpha-2-delta engagement, alongside shape-descriptor differences that may contribute to divergent absorption kinetics. These findings position C. elegans as a valuable model for dissecting gabapentinoid PK/PD relationships. Beyond mechanistic insight, these findings support the continued investigation of C. elegans as a screening platform whose validation could help address the 3R (Replacement, Reduction, Refinement) principles guiding animal research.

Aims Rosuvastatin is commonly co-administered with ticagrelor in patients with acute coronary syndrome. Ticagrelor inhibits breast cancer resistance protein (BCRP/ABCG2), increasing rosuvastatin exposure and potentially the risk of rhabdomyolysis. This risk may be further influenced by age and the ABCG2 c.421C>A variant. We aimed to predict optimal rosuvastatin dosing with ticagrelor in elderly patients stratified by ABCG2 genotype using physiologically based pharmacokinetic (PBPK) modelling Methods PBPK models for rosuvastatin and ticagrelor were developed and validated in PK-Sim using clinical data from healthy adults, elderly patients, and individuals with wild-type or homozygous ABCG2 c.421C>A genotypes. Key parameters, including BCRP catalytic activity and age-dependent declines in CYP2C9 and CYP3A4 activity, were optimized. The drug-drug interaction model incorporated competitive BCRP inhibition by ticagrelor. Rosuvastatin steady-state exposure was simulated with half or quarter standard doses during ticagrelor co-administration, and exposure matching approach was used to identify optimal dosing. Results The PBPK models demonstrated good predictive performance across populations and genotypes. In young adults with the wild-type genotype, halving the rosuvastatin dose resulted in an AUC fold change of 1.44, supporting a half-dose strategy. In young homozygous variant carriers, half-dose co-administration produced comparable exposure (AUC fold change 0.78). In elderly wild-type individuals, a four-fold dose reduction achieved comparable exposure (AUC fold change 1.06), whereas elderly variant carriers required only a half-dose reduction (1.12). Conclusions PBPK modelling supported age- and ABCG2 genotype-specific rosuvastatin dosing with ticagrelor. Elderly wild-type patients may require a further dose reduction to minimise toxicity while maintaining therapeutic exposure.

Objective: Evaluate differences in side effects between a low and standard dose compounded semaglutide paired with a behavioral companion in the first 16 weeks of treatment using a real-world, retrospective cohort. Methods: Side effects were compared between the low dose protocol (Noom Microdose GLP-1 Rx Program; NMGP, up to 0.6mg/weekly compounded semaglutide) and Noom's standard dose of compounded semaglutide (Noom GLP-1 Rx Program; NGP, up to 1.2mg/weekly). Users were propensity score matched on side effect rate in the first 8 weeks when dosing protocols were identical, and longitudinal side effect trajectories were compared via logistic regression. Analyses were conducted on a second cohort with additional matched baseline characteristics. Results: The full sample included 7,682 NGP and 2,877 NMGP users. NMGP users had 34% lower and 29% lower relative odds of reporting GI side effects (p=0.001) and any side effects (p=0.001) by week 16, respectively (n=2,481 per group). Results of the second cohort demonstrated 38% lower odds of any side effect by week 16 among NMGP users (n=958 per group, p=0.019). Conclusions: Lower doses of compounded semaglutide alongside a behavioral companion are associated with fewer side effects in the first 16 weeks compared to a higher dose program.

Voltage-gated Kv7 (KCNQ, M-type) potassium channels regulate cellular excitability through interactions with phosphatidylinositol 4,5-bisphosphate (PIP2;) and calmodulin (CaM). The distal B helix of Kv7.2-5 channels contains a conserved protein kinase C (PKC) phosphorylation site, suggesting that phosphorylation may regulate channel activity by altering CaM- and PIP2;-dependent mechanisms. Here, we investigated the effects of phosphorylation of Thr552 within the Kv7.4 B helix using electrophysiology, biophysical assays, NMR spectroscopy, and molecular dynamics simulations. Phosphomimetic substitution of Thr552 produced a loss-of-function phenotype characterized by reduced current density and a depolarizing shift in voltage-dependent activation without altering channel surface expression. Biophysical studies demonstrated that phosphorylation produced only modest effects on overall CaM association. However, NMR spectroscopy revealed phosphorylation-dependent changes in apoCaM interactions, and molecular dynamics simulations identified remodeling of the local interaction network surrounding the distal B-helix polybasic (KRK motif) region. In contrast, phosphorylation markedly reduced PIP2; binding to both the isolated B helix and CaM-associated Kv7.4 regulatory complexes. Mutation of the distal B-helix KRK motif similarly impaired PIP2; binding, identifying this region as an important determinant of lipid recognition. Together, these findings support a model in which phosphorylation of Thr552 suppresses Kv7.4 activity primarily by reducing PIP2; interactions while reorganizing, rather than disrupting, CaM binding. These results identify Thr552 as a critical regulatory site linking phosphorylation-dependent signaling to Kv7.4 channel gating.

People are widely exposed to the antimicrobial cetylpyridinium chloride (CPC) via consumer products, but CPC is a mitochondrial toxicant with potency comparable to that of canonical mitotoxicants. CPC is largely unregulated despite growing usage, bioavailability, and ability to cross the blood-brain barrier. Previously, we showed, in several cell types at non-cytotoxic and exposure-relevant doses, CPC inhibits ATP and OCR, endpoints of the electron transport chain (ETC). Mitochondrial toxicity is linked to multiple diseases (e.g., diabetes, Parkinsons, myalgic encephalomyelitis), but CPC has not been studied epidemiologically, and little mechanistic information is available. To determine why OCR and ATP are hampered by CPC, we hypothesized that CPC inhibits individual ETC components, cardiolipin, or TCA enzymes. Here, we show that, in primary human skin cells, an immune mast cell model, and isolated mitochondria, CPC apparently inhibits multiple ETC Complexes. Detailed investigation pinpointed the mechanism to the distal end of ETC: Complex III-cytochrome C-Complex IV. Using multiple approaches, we show that CPC does not directly inhibit any of the Complexes (not even Complex I as earlier reported), nor TCA enzymes, nor coenzyme Q. Yet, we found that CPC exhibits mitotoxicity as potent as cyanide. Anionic lipid cardiolipin attracts cytochrome C to the inner mitochondrial membrane so that it may shuttle electrons from Complex III to IV. Despite not altering levels of cardiolipin, CPC hinders cytochrome C by electrostatically interfering with cardiolipin. To aid epidemiology, risk analysis, and predictive toxicology, we have determined the precise biochemical mechanism of action of this ubiquitous compound.