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Background/Objectives: Fluvoxamine is commonly prescribed for depressive disorders in elderly patients, a population that frequently exhibits variable drug responses and increased susceptibility to adverse effects due to age-related physiological changes. CYP2D6 polymorphisms may further affect fluvoxamine pharmacokinetics in elderly patients, complicating dose optimization for this group. Previous pharmacogenetic studies examining the impact of CYP2D6 phenotype on fluvoxamine treatment outcomes have primarily focused on younger adults, leaving a gap in understanding its effects on the elderly. Methods: The impact of CYP2D6 phenotypes on fluvoxamine exposure in geriatrics was evaluated using a physiologically based pharmacokinetic (PBPK) modeling approach incorporating geriatric-specific physiological parameters. Results: The fluvoxamine PBPK model was verified using clinical pharmacokinetic data from younger and older adults, along with phenotype-dependent exposure differences between CYP2D6 poor metabolizers (PMs) and extensive metabolizers (EMs). Simulations showed that steady-state exposure in elderly patients was 1.8-fold higher than those in younger adults, and 2.1-fold higher in CYP2D6 PMs compared with EMs. Based on these simulations, doses of approximately 50 mg/day for PMs, 50–100 mg/day for intermediate metabolizers (IMs), 100 mg/day for EMs, and 150–200 mg/day for ultrarapid metabolizers (UMs) may be appropriate for elderly patients, accompanied by cautious dose escalation and clinical monitoring. Conclusions: These findings suggest that CYP2D6 genotype-guided dosing may be a useful strategy for optimizing fluvoxamine therapy in elderly patients, with the potential to improve treatment outcomes while minimizing the risk of adverse drug reactions in this high-risk population.

Due to climate changes, there has been a large expansion of emerging tick-borne zoonotic viruses, including Heartland bandavirus (HRTV) and Dabie bandavirus (DBV). As etiologic agents of hemorrhagic fever with high fatality, HRTV and DBV have been recognized as dangerous viral pathogens that likely cause future wide epidemics. Despite serious health concerns, the mechanisms underlying viral infection are largely unknown. HRTV and DBV Gn and Gc are viral surface glycoproteins required for early entry events during infection. Glycosphingolipids, including galactosylceramide (GalCer), glucosylceramide (GlcCer) and lactosylceramide (LacCer), are a class of membrane lipids that play essential roles in membrane structure and viral lifecycle. Here, our genome-wide CRISPR/Cas9 knockout screen identifies that glycosphingolipid biosynthesis pathway is essential for HRTV and DBV infection. The deficiency of UDP-glucose ceramide glucosyltransferase (UGCG) that produces GlcCer resulted in the loss of infectivity of recombinant viruses pseudotyped with HRTV or DBV Gn/Gc glycoproteins. Conversely, exogenous supplement of GlcCer, but not GalCer or LacCer, recovered viral entry of UGCG-deficient cells in a dose-dependent manner. Biophysical analyses showed that GlcCer targeted the lipid-head-group binding pocket of Gc to form a stable protein-lipid complex, which allowed the insertion of Gc protein into host lysosomal membrane lipid bilayers for viral fusion. Mutagenesis showed that D841 residue at the Gc lipid binding pocket was critical for GlcCer interaction and thereby, viral entry. These findings reveal detailed mechanism of GlcCer glycosphingolipid in HRTV and DBV Gc-mediated membrane fusion and provide a potential therapeutic target for tickborne virus infection.

Background/Objectives: The increasing use of statins in people with cystic fibrosis (CF) necessitates the investigation of potential drug–drug interactions (DDI) of statins with cystic fibrosis transmembrane conductance regulator (CFTR) modulators, including elexacaftor, tezacaftor, and ivacaftor (ETI). The interactions may involve the potential inhibition of cytochrome P450 isoenzymes (CYPs), organic anion-transporting polypeptides (OATPs), and Breast Cancer Resistance Protein (BCRP) by ETI. This presents a therapeutic challenge in CF due to the potential for elevated statin levels, consequently heightening the risk of myopathy. This study aimed to predict potential DDIs between statins and ETI using a physiologically based pharmacokinetic (PBPK) modeling approach. Methods: We performed in vitro assays to measure the inhibitory potency of ETI against OATPs and CYP2C9 and incorporated these data into our PBPK models alongside published inhibitory parameters for BCRP and CYP3A4. Results: The PBPK simulation showed that atorvastatin had the highest predicted AUC ratio (3.27), followed by pravastatin (2.27), pitavastatin (2.24), and rosuvastatin (1.83). Conclusions: Based on these findings, rosuvastatin appears to exhibit a weak interaction with ETI, whereas other statins exhibited a moderate interaction, potentially requiring appropriate dose reductions. These data indicate potential clinically significant DDIs between ETI and certain statins, which warrants a clinical study to validate these findings.

Escitalopram (S-CIT) is commonly prescribed for depression and anxiety in older patients. Previous research has reported that the effect of CYP2C19 polymorphism on S-CIT pharmacokinetics is more pronounced in older adults than in young adults. The current study investigated whether older adults taking S-CIT face a greater risk for CYP2C19-mediated drug-drug interaction (DDI) than young adults. Using a physiologically-based pharmacokinetic (PBPK) model, we quantitatively compared the risk of CYP2C19-mediated DDIs in older adults taking S-CIT with any of four CYP2C19 inhibitors (omeprazole, esomeprazole, fluconazole, and fluoxetine). These CYP2C19 inhibitors were selected based on their prevalence of co-administration with S-CIT, as determined by a retrospective analysis of the 2019 Korean National Health Insurance Service senior cohort database. Our PBPK modeling-based simulations predicted that the extent of DDI incurred by S-CIT would be greater in older adults than in young adults and vary significantly by CYP2C19 phenotypes (extensive, intermediate, and poor metabolizers). Based on the prediction results, we propose CYP2C19 phenotype-guided S-CIT dosing strategies for older adults. Implementing the proposed dosing recommendation may reduce the incidence of potentially inappropriate use of medication and adverse events in older adults prescribed S-CIT.

Elexacaftor/tezacaftor/ivacaftor (ETI) treatment has potential benefits in lung transplant recipients, including improvements in extrapulmonary manifestations, such as gastrointestinal and sinus disease; however, ivacaftor is an inhibitor of cytochrome P450 3A (CYP3A) and may, therefore, pose a risk for elevated systemic exposure to tacrolimus. The aim of this investigation is to determine the impact of ETI on tacrolimus exposure and devise an appropriate dosing regimen to manage the risk of this drug–drug interaction (DDI). The CYP3A-mediated DDI of ivacaftor–tacrolimus was evaluated using a physiologically based pharmacokinetic (PBPK) modeling approach, incorporating CYP3A4 inhibition parameters of ivacaftor and in vitro enzyme kinetic parameters of tacrolimus. To further support the findings in PBPK modeling, we present a case series of lung transplant patients who received both ETI and tacrolimus. We predicted a 2.36-fold increase in tacrolimus exposure when co-administered with ivacaftor, which would require a 50% dose reduction of tacrolimus upon initiation of ETI treatment to avoid the risk of elevated systemic exposure. Clinical cases (N = 13) indicate a median 32% (IQR: −14.30, 63.80) increase in the dose-normalized tacrolimus trough level (trough concentration/weight-normalized daily dose) after starting ETI. These results indicate that the concomitant administration of tacrolimus and ETI may lead to a clinically significant DDI, requiring the dose adjustment of tacrolimus.

Background Omadacycline offers a potential advancement in the management of infections in people with cystic fibrosis (CF) because of its spectrum of activity, intrapulmonary penetration, and oral bioavailability. A prospective single-dose, single-arm study was conducted to characterize the pharmacokinetic (PK) profile of omadacycline in people with CF, considering the known alterations in PK observed in this population (NCT04460586, 2020-07-01). Methods Plasma samples were obtained from nine adults with CF who received a single dose of intravenous omadacycline 100 mg over 0.5 h followed by a 1-week washout and an oral dose of omadacycline 300 mg. The data were analyzed using noncompartmental PK. Results The maximum plasma concentration ( C max ) and area under the curve extrapolated to infinity (AUC 0-∞ ) after intravenous administration of omadacycline were similar between healthy volunteers and people with CF. The absorption kinetics of oral omadacycline, encompassing both the rate ( C max and time to C max [ t max ]) and the extent (AUC 0-∞ ), also showed consistency between healthy volunteers and people with CF. The absolute bioavailability of the oral tablet formulation of omadacycline in people with CF (31.2%) was also consistent with that observed in healthy volunteers (34.5%). In comparing the two routes of administration, intravenous omadacycline 100 mg provided plasma exposures equivalent to those with oral omadacycline 300 mg in people with CF, as evidenced by geometric mean ratios for both AUC 0-∞ (0.9381; 90% confidence intervals [CI] 0.6783–1.2975) and C max (0.7746; 90% CI 0.5478–1.0951). Conclusions Overall, the similarity in plasma PK observed in this study when comparing healthy volunteers and infected patients indicates that no dosing alterations are necessary when using omadacycline in people with CF.

Omadacycline offers a potential advancement in the management of infections in people with cystic fibrosis (CF) because of its spectrum of activity, intrapulmonary penetration, and oral bioavailability. A prospective single-dose, single-arm study was conducted to characterize the pharmacokinetic (PK) profile of omadacycline in people with CF, considering the known alterations in PK observed in this population (NCT04460586, 2020-07-01). Plasma samples were obtained from nine adults with CF who received a single dose of intravenous omadacycline 100 mg over 0.5 h followed by a 1-week washout and an oral dose of omadacycline 300 mg. The data were analyzed using noncompartmental PK. The maximum plasma concentration (C ) and area under the curve extrapolated to infinity (AUC ) after intravenous administration of omadacycline were similar between healthy volunteers and people with CF. The absorption kinetics of oral omadacycline, encompassing both the rate (C and time to C [t ]) and the extent (AUC ), also showed consistency between healthy volunteers and people with CF. The absolute bioavailability of the oral tablet formulation of omadacycline in people with CF (31.2%) was also consistent with that observed in healthy volunteers (34.5%). In comparing the two routes of administration, intravenous omadacycline 100 mg provided plasma exposures equivalent to those with oral omadacycline 300 mg in people with CF, as evidenced by geometric mean ratios for both AUC (0.9381; 90% confidence intervals [CI] 0.6783-1.2975) and C (0.7746; 90% CI 0.5478-1.0951). Overall, the similarity in plasma PK observed in this study when comparing healthy volunteers and infected patients indicates that no dosing alterations are necessary when using omadacycline in people with CF.

Due to climate changes, there has been a large expansion of emerging tick-borne zoonotic viruses, including Heartland bandavirus (HRTV) and Dabie bandavirus (DBV). As etiologic agents of hemorrhagic fever with high fatality, HRTV and DBV have been recognized as dangerous viral pathogens that likely cause future wide epidemics. Despite serious health concerns, the mechanisms underlying viral infection are largely unknown. HRTV and DBV Gn and Gc are viral surface glycoproteins required for early entry events during infection. Glycosphingolipids, including galactosylceramide (GalCer), glucosylceramide (GlcCer) and lactosylceramide (LacCer), are a class of membrane lipids that play essential roles in membrane structure and viral lifecycle. Here, our genome-wide CRISPR/Cas9 knockout screen identifies that glycosphingolipid biosynthesis pathway is essential for HRTV and DBV infection. The deficiency of UDP-glucose ceramide glucosyltransferase (UGCG) that produces GlcCer resulted in the loss of infectivity of recombinant viruses pseudotyped with HRTV or DBV Gn/Gc glycoproteins. Conversely, exogenous supplement of GlcCer, but not GalCer or LacCer, recovered viral entry of UGCG-deficient cells in a dose-dependent manner. Biophysical analyses showed that GlcCer targeted the lipid-head-group binding pocket of Gc to form a stable protein-lipid complex, which allowed the insertion of Gc protein into host lysosomal membrane lipid bilayers for viral fusion. Mutagenesis showed that D841 residue at the Gc lipid binding pocket was critical for GlcCer interaction and thereby, viral entry. These findings reveal detailed mechanism of GlcCer glycosphingolipid in HRTV and DBV Gc-mediated membrane fusion and provide a potential therapeutic target for tickborne virus infection.

The most frequent fetal birth defect associated with prenatal Zika virus (ZIKV) infection is brain calcification, which in turn may potentially affect neurological development in infants. Understanding the mechanism could inform the development of potential therapies against prenatal ZIKV brain calcification. In perivascular cells, bone morphogenetic protein (BMP) is an osteogenic factor that undergoes maturation to activate osteogenesis and calcification. Here, we show that ZIKV infection of cultivated primary human brain pericytes triggers BMP2 maturation, leading to osteogenic gene expression and calcification. We observed extensive calcification near ZIKV + pericytes of fetal human brain specimens and in vertically transmitted ZIKV + human signal transducer and activator of transcription 2-knockin mouse pup brains. ZIKV infection of primary pericytes stimulated BMP2 maturation, inducing osteogenic gene expression and calcification that were completely blocked by anti-BMP2/4 neutralizing antibody. Not only did ZIKV NS3 expression alone induce BMP2 maturation, osteogenic gene expression and calcification, but purified NS3 protease also effectively cleaved pro-BMP2 in vitro to generate biologically active mature BMP2. These findings highlight ZIKV-induced calcification where the NS3 protease subverts the BMP2-mediated osteogenic signalling pathway to trigger brain calcification. Zika virus infection of human brain pericytes triggers maturation of an osteogenic factor, thereby resulting in osteogenic gene expression and calcification.