In vivo antimalarial efficacy of Artemisia afra powder suspensions

BACKGROUND

A global death toll of 608,000 in 2022 and emerging parasite resistance to artemisinin, the mainstay of antimalarial chemotherapy derived from the Chinese herb Artemisia annua, urge the development of novel antimalarials. A clinical trial has found high antimalarial potency for aqueous extracts of A. annua as well as its African counterpart Artemisia afra, which contains only trace amounts of artemisinin. The artemisinin-independent antimalarial activity of A. afra points to the existence of other antimalarials present in the plant. However, the publication was retracted due to ethical and methodological concerns in the trial, so the only evidence for antimalarial activity of A. afra is built on in vitro studies reporting efficacy only in the microgram per milliliter range.

HYPOTHESIS

Our study aims to shed more light on the controversy around the antimalarial activity of A. afra by assessing its efficacy in mice. In particular, we are testing the hypothesis that A. afra contains a pro-drug that is inactive in vitro but active in vivo after metabolization by the mammalian host.

METHODS

Plasmodium berghei-infected mice were treated once or thrice (on three consecutive days) with various doses of A. afra, A. annua, or pure artemisinin.

RESULTS

Aqueous powder suspensions of A. annua but not A. afra showed antimalarial activity in mice.

CONCLUSION

Our experiments conducted in mice do not support the pro-drug hypothesis.

Derivatization-free determination of chiral plasma pharmacokinetics of MDMA and its enantiomers

3,4-Methylenedioxymethamphetamine (MDMA) is an entactogen with therapeutic potential. The two enantiomers of MDMA differ regarding their pharmacokinetics and pharmacodynamics but the chiral pharmacology of MDMA needs further study in clinical trials. Here, an achiral and an enantioselective high performance liquid chromatography-tandem mass spectrometry method for the quantification of MDMA and its psychoactive phase I metabolite 3,4-methylenedioxyamphetamine (MDA) in human plasma were developed and validated. The analytes were detected by positive electrospray ionization followed by multiple reaction monitoring. The calibration range was 0.5-500 ng/mL for the achiral analysis of both analytes, 0.5-1,000 ng/mL for chiral MDMA analysis, and 1-1,000 ng/mL for chiral MDA analysis. Accuracy, precision, selectivity, and sensitivity of both bioanalytical methods were in accordance with regulatory guidelines. Furthermore, accuracy and precision of the enantioselective method were maintained when racemic calibrations were used to measure quality control samples containing only one of the enantiomers. Likewise, enantiomeric calibrations could be used to reliably quantify enantiomers in racemic samples. The achiral and enantioselective methods were employed to assess pharmacokinetic parameters in clinical study participants treated with racemic MDMA or one of its enantiomers. The pharmacokinetic parameters assessed with both bioanalytical methods were comparable. In conclusion, the enantioselective method is useful for the simultaneous quantification of both enantiomers in subjects treated with racemic MDMA. However, as MDMA and MDA do not undergo chiral inversion, enantioselective separation is not necessary in subjects treated with only one of the enantiomers.

Inhibition of the transmembrane transporter ABCB1 overcomes resistance to doxorubicin in patient-derived organoid models of HCC

BACKGROUND

Transarterial chemoembolization is the first-line treatment for intermediate-stage HCC. However, the response rate to transarterial chemoembolization varies, and the molecular mechanisms underlying variable responses are poorly understood. Patient-derived hepatocellular carcinoma organoids (HCCOs) offer a novel platform to investigate the molecular mechanisms underlying doxorubicin resistance.

METHODS

We evaluated the effects of hypoxia and doxorubicin on cell viability and cell cycle distribution in 20 patient-derived HCCO lines. The determinants of doxorubicin response were identified by comparing the transcriptomes of sensitive to resistant HCCOs. Candidate genes were validated by pharmacological inhibition.

RESULTS

Hypoxia reduced the proliferation of HCCOs and increased the number of cells in the G0/G1 phase of the cell cycle, while decreasing the number in the S phase. The IC50s of the doxorubicin response varied widely, from 29nM to >1µM. Doxorubicin and hypoxia did not exhibit synergistic effects but were additive in some HCCOs. Doxorubicin reduced the number of cells in the G0/G1 and S phases and increased the number in the G2 phase under both normoxia and hypoxia. Genes related to drug metabolism and export, most notably ABCB1, were differentially expressed between doxorubicin-resistant and doxorubicin-sensitive HCCOs. Small molecule inhibition of ABCB1 increased intracellular doxorubicin levels and decreased drug tolerance in resistant HCCOs.

CONCLUSIONS

The inhibitory effects of doxorubicin treatment and hypoxia on HCCO proliferation are variable, suggesting an important role of tumor-cell intrinsic properties in doxorubicin resistance. ABCB1 is a determinant of doxorubicin response in HCCOs. Combination treatment of doxorubicin and ABCB1 inhibition may increase the response rate to transarterial chemoembolization.

In vitro and in vivo metabolism of psilocybin's active metabolite psilocin

In vivo, psilocybin is rapidly dephosphorylated to psilocin which induces psychedelic effects by interacting with the 5-HT2A receptor. Psilocin primarily undergoes glucuronidation or conversion to 4-hydroxyindole-3-acetic acid (4-HIAA). Herein, we investigated psilocybin's metabolic pathways in vitro and in vivo, conducting a thorough analysis of the enzymes involved. Metabolism studies were performed using human liver microsomes (HLM), cytochrome P450 (CYP) enzymes, monoamine oxidase (MAO), and UDP-glucuronosyltransferase (UGT). In vivo, metabolism was examined using male C57BL/6J mice and human plasma samples. Approximately 29% of psilocin was metabolized by HLM, while recombinant CYP2D6 and CYP3A4 enzymes metabolized nearly 100% and 40% of psilocin, respectively. Notably, 4-HIAA and 4-hydroxytryptophol (4-HTP) were detected with HLM but not with recombinant CYPs. MAO-A transformed psilocin into minimal amounts of 4-HIAA and 4-HTP. 4-HTP was only present in vitro. Neither 4-HIAA nor 4-HTP showed relevant interactions at assessed 5-HT receptors. In contrast to in vivo data, UGT1A10 did not extensively metabolize psilocin in vitro. Furthermore, two putative metabolites were observed. N-methyl-4-hydroxytryptamine (norpsilocin) was identified in vitro (CYP2D6) and in mice, while an oxidized metabolite was detected in vitro (CYP2D6) and in humans. However, the CYP2D6 genotype did not influence psilocin plasma concentrations in the investigated study population. In conclusion, MAO-A, CYP2D6, and CYP3A4 are involved in psilocin's metabolism. The discovery of putative norpsilocin in mice and oxidized psilocin in humans further unravels psilocin's metabolism. Despite limitations in replicating phase II metabolism in vitro, these findings hold significance for studying drug-drug interactions and advancing research on psilocybin as a therapeutic agent.

Development and validation of an LC-MS/MS method for quantifying diamorphine and its major metabolites 6-monoacetylmorphine, morphine, morphine-3-glucuronide, and morphine-6-glucuronide in human plasma

Diamorphine, commonly known as heroin, is a semi-synthetic opioid analgesic. In the context of heroin-assisted treatment for opioid-dependent patients, diamorphine is mostly administered intravenously. However, recent attention has shifted towards intranasal administration as a better-tolerated alternative to the intravenous route. Here, we developed and validated a rapid bioanalytical method for the simultaneous quantification of diamorphine and its major metabolites 6-monoacetylmorphine, morphine, morphine-3-glucuronide, and morphine-6-glucuronide in human plasma using liquid chromatography-tandem mass spectrometry (LC-MS/MS). A straightforward protein precipitation extraction step was used for sample preparation. Chromatographic analyte separation was achieved using a Kinetex EVO C18 analytical column and a mobile phase gradient comprising an aqueous solution of ammonium hydrogen carbonate and methanol supplied with formic acid. Employing positive electrospray ionization and scheduled multiple reaction monitoring, we established a quantification range of 1-1,000 ng/mL for all analytes. Our validation results demonstrate a mean intra-assay accuracy of 91-106% and an intra-assay precision (CV) between 2 and 9% for all analytes and over three validation runs. The method exhibits a high extraction recovery (> 87%) and a negligible matrix effect (99-125%). Furthermore, no interferences with endogenous plasma compounds were detected. Lastly, we applied the method to assess the plasma concentrations of an opioid-dependent patient after the intranasal administration of diamorphine in a clinical study. In summary, we have successfully developed a rapid, highly reliable, and straightforward bioanalytical method for quantifying diamorphine and its metabolites in low amounts of clinical plasma samples.

Pharmacokinetics-Based Pediatric Dose Evaluation and Optimization Using Saliva - A Case Study

Understanding pharmacokinetics (PK) in children is a prerequisite to determine optimal pediatric dosing. As plasma sampling in children is challenging, alternative PK sampling strategies are needed. In this case study we evaluated the suitability of saliva as alternative PK matrix to simplify studies in infants, investigating metamizole, an analgesic used off-label in infants. Six plasma and 6 saliva PK sample collections were scheduled after a single intravenous dose of 10 mg/kg metamizole. Plasma/saliva pharmacometric (PMX) modeling of the active metabolites 4-methylaminoantipyrine (4-MAA) and 4-aminoantipyrine (4-AA) was performed. Various reduced plasma sampling scenarios were evaluated by PMX simulations. Saliva and plasma samples from 25 children were included (age range, 5-70 months; weight range, 8.7-24.8 kg). Distribution of metamizole metabolites between plasma and saliva was without delay. Estimated mean (individual range) saliva/plasma fractions of 4-MAA and 4-AA were 0.32 (0.05-0.57) and 0.57 (0.25-0.70), respectively. Residual variability of 4-MAA (4-AA) in saliva was 47% (28%) versus 17% (11%) in plasma. A simplified sampling scenario with up to 6 saliva samples combined with 1 plasma sample was associated with similar PK parameter estimates as the full plasma sampling scenario. This case study with metamizole shows increased PK variability in saliva compared to plasma, compromising its suitability as single matrix for PK studies in infants. Nonetheless, rich saliva sampling can reduce the number of plasma samples required for PK characterization, thereby facilitating the conduct of PK studies to optimize dosing in pediatric patients.

Mechanisms of hepatocellular toxicity associated with the components of St. John's Wort extract hypericin and hyperforin in HepG2 and HepaRG cells

St. John's Wort preparations are used for the treatment of mild to moderate depression. They are usually well tolerated but can cause adverse reactions including liver toxicity in rare cases. To date, the mechanism(s) underlying the hepatotoxicity of St. John's Wort extracts are poorly investigated. We studied the hepatocellular toxicity of hypericin and hyperforin as the two main ingredients of St. John's Wort extracts in HepG2 and HepaRG cells and compared the effects to citalopram (a synthetic serotonin uptake inhibitor) with a special focus on mitochondrial toxicity and oxidative stress. In HepG2 cells, hypericin was membrane-toxic at 100 µM and depleted ATP at 20 µM. In HepaRG cells, ATP depletion started at 5 µM. In comparison, hyperforin and citalopram were not toxic up to 100 µM. In HepG2 cells, hypericin decreased maximal respiration starting at 2 µM and mitochondrial ATP formation starting at 10 µM but did not affect glycolytic ATP production. Hypericin inhibited the activity of complex I, II and IV of the electron transfer system and caused mitochondrial superoxide accumulation in cells. The protein expression of mitochondrial superoxide dismutase 2 (SOD2) and thioredoxin 2 (TRX2) and total and reduced glutathione decreased in cells exposed to hypericin. Finally, hypericin diminished the mitochondrial DNA copy number and caused cell necrosis but not apoptosis. In conclusion, hypericin, but not hyperforin or citalopram, is a mitochondrial toxicant at low micromolar concentrations. This mechanism may contribute to the hepatotoxicity occasionally observed in susceptible patients treated with St. John's Wort preparations.

Pharmacokinetics, pharmacodynamics and urinary recovery of oral lysergic acid diethylamide administration in healthy participants

AIMS

Lysergic acid diethylamide (LSD) is currently investigated for several neurological and psychiatric illnesses. Various studies have investigated the pharmacokinetics and the pharmacokinetic-pharmacodynamic relationship of LSD in healthy participants, but data on urinary recovery and confirmatory studies are missing.

METHODS

The present study characterized the pharmacokinetics, pharmacokinetic-pharmacodynamic relationship and urinary recovery of LSD at doses of 85 and 170 μg administered orally in 28 healthy participants. The plasma concentrations and subjective effects of LSD were continuously evaluated over a period of 24 h. Urine was collected during 3 time intervals (0-8, 8-16 and 16-24 h after LSD administration). Pharmacokinetic parameters were determined using compartmental modelling. Concentration-subjective effect relationships were described using pharmacokinetic-pharmacodynamic modelling.

RESULTS

Mean (95% confidence interval) maximal LSD concentrations were 1.8 ng/mL (1.6-2.0) and 3.4 ng/mL (3.0-3.8) after the administration of 85 and 170 μg LSD, respectively. Maximal concentrations were achieved on average after 1.7 h. Elimination half-lives were 3.7 h (3.4-4.1) and 4.0 h (3.6-4.4), for 85 and 170 μg LSD, respectively. Only 1% of the administered dose was recovered from urine unchanged within the first 24 h, 16% was eliminated as 2-oxo-3-hydroxy-LSD. Urinary recovery was dose proportional. Mean (±standard deviation) durations of subjective effects were 9.3 ± 3.2 and 11 ± 3.7 h, and maximal effects (any drug effects) were 77 ± 18% and 87 ± 13% after 85 and 170 μg of LSD, respectively.

CONCLUSION

The present novel study validates previous findings. LSD exhibited dose-proportional pharmacokinetics and first-order elimination kinetics and dose-dependent duration and intensity of subjective effects. LSD is extensively metabolized and shows dose-proportional urinary recovery.

Acute effects of MDMA and LSD co-administration in a double-blind placebo-controlled study in healthy participants

There is renewed interest in the use of lysergic acid diethylamide (LSD) in psychiatric research and practice. Although acute subjective effects of LSD are mostly positive, negative subjective effects, including anxiety, may occur. The induction of overall positive acute subjective effects is desired in psychedelic-assisted therapy because positive acute experiences are associated with greater therapeutic long-term benefits. 3,4-Methylenedioxymethamphetamine (MDMA) produces marked positive subjective effects and is used recreationally with LSD, known as "candyflipping." The present study investigated whether the co-administration of MDMA can be used to augment acute subjective effects of LSD. We used a double-blind, randomized, placebo-controlled, crossover design with 24 healthy subjects (12 women, 12 men) to compare the co-administration of MDMA (100 mg) and LSD (100 µg) with MDMA and LSD administration alone and placebo. Outcome measures included subjective, autonomic, and endocrine effects and pharmacokinetics. MDMA co-administration with LSD did not change the quality of acute subjective effects compared with LSD alone. However, acute subjective effects lasted longer after LSD + MDMA co-administration compared with LSD and MDMA alone, consistent with higher plasma concentrations of LSD (Cmax and area under the curve) and a longer plasma elimination half-life of LSD when MDMA was co-administered. The LSD + MDMA combination increased blood pressure, heart rate, and pupil size more than LSD alone. Both MDMA alone and the LSD + MDMA combination increased oxytocin levels more than LSD alone. Overall, the co-administration of MDMA (100 mg) did not improve acute effects or the safety profile of LSD (100 µg). The combined use of MDMA and LSD is unlikely to provide relevant benefits over LSD alone in psychedelic-assisted therapy. Trial registration: ClinicalTrials.gov identifier: NCT04516902.

Comparative acute effects of mescaline, lysergic acid diethylamide, and psilocybin in a randomized, double-blind, placebo-controlled cross-over study in healthy participants

Mescaline, lysergic acid diethylamide (LSD), and psilocybin are classic serotonergic psychedelics. A valid, direct comparison of the effects of these substances is lacking. The main goal of the present study was to investigate potential pharmacological, physiological and phenomenological differences at psychoactive-equivalent doses of mescaline, LSD, and psilocybin. The present study used a randomized, double-blind, placebo-controlled, cross-over design to compare the acute subjective effects, autonomic effects, and pharmacokinetics of typically used, moderate to high doses of mescaline (300 and 500 mg), LSD (100 µg), and psilocybin (20 mg) in 32 healthy participants. A mescaline dose of 300 mg was used in the first 16 participants and 500 mg was used in the subsequent 16 participants. Acute subjective effects of 500 mg mescaline, LSD, and psilocybin were comparable across various psychometric scales. Autonomic effects of 500 mg mescaline, LSD, and psilocybin were moderate, with psilocybin causing a higher increase in diastolic blood pressure compared with LSD, and LSD showing a trend toward an increase in heart rate compared with psilocybin. The tolerability of mescaline, LSD, and psilocybin was comparable, with mescaline at both doses inducing slightly more subacute adverse effects (12-24 h) than LSD and psilocybin. Clear distinctions were seen in the duration of action between the three substances. Mescaline had the longest effect duration (mean: 11.1 h), followed by LSD (mean: 8.2 h), and psilocybin (mean: 4.9 h). Plasma elimination half-lives of mescaline and LSD were similar (approximately 3.5 h). The longer effect duration of mescaline compared with LSD was due to the longer time to reach maximal plasma concentrations and related peak effects. Mescaline and LSD, but not psilocybin, enhanced circulating oxytocin. None of the substances altered plasma brain-derived neurotrophic factor concentrations. In conclusion, the present study found no evidence of qualitative differences in altered states of consciousness that were induced by equally strong doses of mescaline, LSD, and psilocybin. The results indicate that any differences in the pharmacological profiles of mescaline, LSD, and psilocybin do not translate into relevant differences in the subjective experience. ClinicalTrials.gov identifier: NCT04227756.

The Activity of Members of the UDP-Glucuronosyltransferase Subfamilies UGT1A and UGT2B is Impaired in Patients with Liver Cirrhosis

BACKGROUND AND OBJECTIVE

The impact of liver cirrhosis on the activity of UDP-glucuronosyltransferases (UGTs) is currently not well characterized. We investigated the glucuronidation capacity and glucuronide accumulation in patients with liver cirrhosis.

METHODS

We administered the Basel phenotyping cocktail (caffeine, efavirenz, flurbiprofen, omeprazole, metoprolol, midazolam) to patients with liver cirrhosis (n = 16 Child A, n = 15 Child B, n = 5 Child C) and n = 12 control subjects and obtained pharmacokinetic profiles of substrates and primary metabolites and their glucuronides.

RESULTS

Caffeine and its metabolite paraxanthine were only slightly glucuronidated. The metabolic ratio (AUCglucuronide/AUCparent, MR) was not affected for caffeine but decreased by 60% for paraxanthine glucuronide formation in Child C patients. Efavirenz was not glucuronidated whereas 8-hydroxyefavirenz was efficiently glucuronidated. The MR of 8-hydroxyefavirenz-glucuronide formation increased three-fold in Child C patients and was negatively correlated with the glomerular filtration rate. Flurbiprofen and omeprazole were not glucuronidated. 4-Hydroxyflurbiprofen and 5-hydroxyomeprazole were both glucuronidated but the corresponding MRs for glucuronide formation were not affected by liver cirrhosis. Metoprolol, but not α-hydroxymetoprolol, was glucuronidated, and the MR for metoprolol-glucuronide formation dropped by 60% in Child C patients. Both midazolam and its metabolite 1'-hydroxymidazolam underwent glucuronidation, and the corresponding MRs for glucuronide formation dropped by approximately 80% in Child C patients. No relevant glucuronide accumulation occurred in patients with liver cirrhosis.

CONCLUSIONS

Detailed analysis revealed that liver cirrhosis may affect the activity of UGTs of the UGT1A and UGT2B subfamilies according to liver function. Clinically significant glucuronide accumulation did not occur in the population investigated.

CLINICAL TRIAL REGISTRATION

NCT03337945.

Pharmacokinetics of ivermectin metabolites and their activity against Anopheles stephensi mosquitoes

BACKGROUND

Ivermectin (22,23-dihydroavermectin B_1a: H₂B_1a) is an endectocide used to treat worm infections and ectoparasites including lice and scabies mites. Furthermore, survival of malaria transmitting Anopheles mosquitoes is strongly decreased after feeding on humans recently treated with ivermectin. Currently, mass drug administration of ivermectin is under investigation as a potential novel malaria vector control tool to reduce Plasmodium transmission by mosquitoes. A "post-ivermectin effect" has also been reported, in which the survival of mosquitoes remains reduced even after ivermectin is no longer detectable in blood meals. In the present study, existing material from human clinical trials was analysed to understand the pharmacokinetics of ivermectin metabolites and feeding experiments were performed in Anopheles stephensi mosquitoes to assess whether ivermectin metabolites contribute to the mosquitocidal action of ivermectin and whether they may be responsible for the post-ivermectin effect.

METHODS

Ivermectin was incubated in the presence of recombinant human cytochrome P₄₅₀ 3A4/5 (CYP 3A4/5) to produce ivermectin metabolites. In total, nine metabolites were purified by semi-preparative high-pressure liquid chromatography. The pharmacokinetics of the metabolites were assessed over three days in twelve healthy volunteers who received a single oral dose of 12 mg ivermectin. Blank whole blood was spiked with the isolated metabolites at levels matching the maximal blood concentration (C_max) observed in pharmacokinetics study samples. These samples were fed to An. stephensi mosquitoes, and their survival and vitality was recorded daily over 3 days.

RESULTS

Human CYP3A4 metabolised ivermectin more rapidly than CYP3A5. Ivermectin metabolites M1-M8 were predominantly formed by CYP3A4, whereas metabolite M9 (hydroxy-H₂B_1a) was mainly produced by CYP3A5. Both desmethyl-H₂B_1a (M1) and hydroxy-H₂B_1a (M2) killed all mosquitoes within three days post-feeding, while administration of desmethyl, hydroxy-H₂B_1a (M4) reduced survival to 35% over an observation period of 3 days. Ivermectin metabolites that underwent deglycosylation or hydroxylation at spiroketal moiety were not active against An. stephensi at C_max levels. Interestingly, half-lives of M1 (54.2 ± 4.7 h) and M4 (57.5 ± 13.2 h) were considerably longer than that of the parent compound ivermectin (38.9 ± 20.8 h).

CONCLUSION

In conclusion, the ivermectin metabolites M1 and M2 contribute to the activity of ivermectin against An. stephensi mosquitoes and could be responsible for the "post-ivermectin effect".

Acute effects of intravenous DMT in a randomized placebo-controlled study in healthy participants

N,N-dimethyltryptamine (DMT) is distinct among classic serotonergic psychedelics because of its short-lasting effects when administered intravenously. Despite growing interest in the experimental and therapeutic use of intravenous DMT, data are lacking on its clinical pharmacology. We conducted a double-blind, randomized, placebo-controlled crossover trial in 27 healthy participants to test different intravenous DMT administration regimens: placebo, low infusion (0.6 mg/min), high infusion (1 mg/min), low bolus + low infusion (15 mg + 0.6 mg/min), and high bolus + high infusion (25 mg + 1 mg/min). Study sessions lasted for 5 h and were separated by at least 1 week. Participant's lifetime use of psychedelics was ≤20 times. Outcome measures included subjective, autonomic, and adverse effects, pharmacokinetics of DMT, and plasma levels of brain-derived neurotropic factor (BDNF) and oxytocin. Low (15 mg) and high (25 mg) DMT bolus doses rapidly induced very intense psychedelic effects that peaked within 2 min. DMT infusions (0.6 or 1 mg/min) without a bolus induced slowly increasing and dose-dependent psychedelic effects that reached plateaus after 30 min. Both bolus doses produced more negative subjective effects and anxiety than infusions. After stopping the infusion, all drug effects rapidly decreased and completely subsided within 15 min, consistent with a short early plasma elimination half-life (t_1/2α) of 5.0-5.8 min, followed by longer late elimination (t_1/2β = 14-16 min) after 15-20 min. Subjective effects of DMT were stable from 30 to 90 min, despite further increasing plasma concentrations, thus indicating acute tolerance to continuous DMT administration. Intravenous DMT, particularly when administered as an infusion, is a promising tool for the controlled induction of a psychedelic state that can be tailored to the specific needs of patients and therapeutic sessions.Trial registration: ClinicalTrials.gov identifier: NCT04353024.

Dose adjustment in patients with liver cirrhosis - comparison of two different modeling approaches

Failure to perform adequate dose adjustment in patients with liver cirrhosis may be associated with increased toxicity. We compared the prediction of AUC and clearance for the six compounds of the Basel phenotyping cocktail (caffeine, efavirenz, flurbiprofen, omeprazole, metoprolol, midazolam) using a well-known physiology-based pharmacokinetic approach ("PBPK approach", Simcyp®) and a novel top-down method based on the systemic clearance in healthy volunteers adjusted for markers of liver and renal dysfunction ("top-down approach"). With few exceptions, plasma concentration-time curves were accurately predicted by the PBPK approach. In comparison to the measured AUC and clearance of these drugs in patients with liver cirrhosis and healthy controls, except for efavirenz, the estimates of both approaches were within 2 standard deviations of the mean for total and free drug concentrations. For both approaches, a correction factor for dose adjustment in patients with liver cirrhosis could be calculated for the drugs administered. AUCs calculated using the adjusted doses were comparable to the AUCs measured in control subjects, with slightly more accurate predictions generated by the PBPK approach. For drugs with a free fraction <50%, predictions using free drug concentrations were more accurate than with total drug concentrations. In conclusion, both methods provided good qualitative predictions of the changes by liver cirrhosis in the pharmacokinetics of the six compounds investigated. The top-down approach is easier to implement but the PBPK approach predicted changes in drug exposure more accurately than the top-down approach and provided reliable estimates for plasma concentrations.

Pharmacokinetics and Pharmacodynamics of Oral Psilocybin Administration in Healthy Participants

Psilocybin is being investigated as a potential treatment for psychiatric and neurological disorders. Only a few studies have evaluated the pharmacokinetics (PKs) of psilocybin and have used body weight-adjusted dosing. Data on PKs and the PK-pharmacodynamic (PD) relationship of fixed doses that are commonly used are unavailable. The present study characterized the PKs and PK-PD relationship of 15, 25, and 30 mg of orally administered psilocybin in 28, 23, and 28 healthy subjects, respectively. Plasma levels of unconjugated psilocin (the psychoactive metabolite of psilocybin) and corresponding subjective effects were repeatedly assessed up to 24 hours. PK parameters were determined using compartmental modeling. Concentration-subjective effect relationships were described using PK-PD modeling. Mean (95% confidence interval) maximal psilocin concentrations were 11 ng/mL (10-13), 17 ng/mL (16-19), and 21 ng/mL (19-24) after the administration of 15, 25, and 30 mg psilocybin, respectively. Maximal concentrations were reached after an average of 2 hours. Elimination half-lives were 1.8 hours (1.7-2.0), 1.4 hours (1.2-1.7), and 1.8 hours (1.6-1.9) for 15, 25, and 30 mg psilocybin, respectively. Mean (± SD) durations of subjective effects were 5.6 ± 2.2 hours, 5.5 ± 1.6 hours, and 6.4 ± 2.2 hours, and maximal effects ("any drug" effects) were 58% ± 25%, 73% ± 27%, and 80% ± 18% after 15, 25, and 30 mg psilocybin, respectively. Psilocin exhibited dose-proportional PKs. The duration and intensity of subjective effects were dose-dependent. Body weight did not influence pharmacokinetics or the response to psilocybin. These data may serve as a reference for future clinical trials.

Allosteric targeting resolves limitations of earlier LFA-1 directed modalities

Integrins are a family of cell surface receptors well-recognized for their therapeutic potential in a wide range of diseases. However, the development of integrin targeting medications has been impacted by unexpected downstream effects, reflecting originally unforeseen interference with the bidirectional signalling and cross-communication of integrins. We here selected one of the most severely affected target integrins, the integrin lymphocyte function-associated antigen-1 (LFA-1, α_Lβ₂, CD11a/CD18), as a prototypic integrin to systematically assess and overcome these known shortcomings. We employed a two-tiered ligand-based virtual screening approach to identify a novel class of allosteric small molecule inhibitors targeting this integrin's αI domain. The newly discovered chemical scaffold was derivatized, yielding potent bis-and tris-aryl-bicyclic-succinimides which inhibit LFA-1 in vitro at low nanomolar concentrations. The characterisation of these compounds in comparison to earlier LFA-1 targeting modalities established that the allosteric LFA-1 inhibitors (i) are devoid of partial agonism, (ii) selectively bind LFA-1 versus other integrins, (iii) do not trigger internalization of LFA-1 itself or other integrins and (iv) display oral availability. This profile differentiates the new generation of allosteric LFA-1 inhibitors from previous ligand mimetic-based LFA-1 inhibitors and anti-LFA-1 antibodies, and is projected to support novel immune regulatory regimens selectively targeting the integrin LFA-1. The rigorous computational and experimental assessment schedule described here is designed to be adaptable to the preclinical discovery and development of novel allosterically acting compounds targeting integrins other than LFA-1, providing an exemplary approach for the early characterisation of next generation integrin inhibitors.

BOHEMIA: Broad One Health Endectocide-based Malaria Intervention in Africa-a phase III cluster-randomized, open-label, clinical trial to study the safety and efficacy of ivermectin mass drug administration to reduce malaria transmission in two African settings

BACKGROUND

Residual malaria transmission is the result of adaptive mosquito behavior that allows malaria vectors to thrive and sustain transmission in the presence of good access to bed nets or insecticide residual spraying. These behaviors include crepuscular and outdoor feeding as well as intermittent feeding upon livestock. Ivermectin is a broadly used antiparasitic drug that kills mosquitoes feeding on a treated subject for a dose-dependent period. Mass drug administration with ivermectin has been proposed as a complementary strategy to reduce malaria transmission.

METHODS

A cluster randomized, parallel arm, superiority trial conducted in two settings with distinct eco-epidemiological conditions in East and Southern Africa. There will be three groups: human intervention, consisting of a dose of ivermectin (400 mcg/kg) administered monthly for 3 months to all the eligible population in the cluster (>15 kg, non-pregnant and no medical contraindication); human and livestock intervention, consisting human treatment as above plus treatment of livestock in the area with a single dose of injectable ivermectin (200 mcg/kg) monthly for 3 months; and controls, consisting of a dose of albendazole (400 mg) monthly for 3 months. The main outcome measure will be malaria incidence in a cohort of children under five living in the core of each cluster followed prospectively with monthly RDTs DISCUSSION: The second site for the implementation of this protocol has changed from Tanzania to Kenya. This summary presents the Mozambique-specific protocol while the updated master protocol and the adapted Kenya-specific protocol undergo national approval in Kenya. BOHEMIA will be the first large-scale trial evaluating the impact of ivermectin-only mass drug administration to humans or humans and cattle on local malaria transmission TRIAL REGISTRATION: ClinicalTrials.gov NCT04966702 . Registered on July 19, 2021. Pan African Clinical Trials Registry PACTR202106695877303.

Stimulatory MAIT cell antigens reach the circulation and are efficiently metabolised and presented by human liver cells

OBJECTIVE

Mucosal-associated invariant T (MAIT) cells are the most abundant T cells in human liver. They respond to bacterial metabolites presented by major histocompatibility complex-like molecule MR1. MAIT cells exert regulatory and antimicrobial functions and are implicated in liver fibrogenesis. It is not well understood which liver cells function as antigen (Ag)-presenting cells for MAIT cells, and under which conditions stimulatory Ags reach the circulation.

DESIGN

We used different types of primary human liver cells in Ag-presentation assays to blood-derived and liver-derived MAIT cells. We assessed MAIT cell stimulatory potential of serum from healthy subjects and patients with portal hypertension undergoing transjugular intrahepatic portosystemic shunt stent, and patients with inflammatory bowel disease (IBD).

RESULTS

MAIT cells were dispersed throughout healthy human liver and all tested liver cell types stimulated MAIT cells, hepatocytes being most efficient. MAIT cell activation by liver cells occurred in response to bacterial lysate and pure Ag, and was prevented by non-activating MR1 ligands. Serum derived from peripheral and portal blood, and from patients with IBD stimulated MAIT cells in MR1-dependent manner.

CONCLUSION

Our findings reveal previously unrecognised roles of liver cells in Ag metabolism and activation of MAIT cells, repression of which creates an opportunity to design antifibrotic therapies. The presence of MAIT cell stimulatory Ags in serum rationalises the observed activated MAIT cell phenotype in liver. Increased serum levels of gut-derived MAIT cell stimulatory ligands in patients with impaired intestinal barrier function indicate that intrahepatic Ag-presentation may represent an important step in the development of liver disease.

Ketanserin Reverses the Acute Response to LSD in a Randomized, Double-Blind, Placebo-Controlled, Crossover Study in Healthy Participants

BACKGROUND

Lysergic acid diethylamide (LSD) is currently being investigated in psychedelic-assisted therapy. LSD has a long duration of acute action of 8-11 hours. It produces its acute psychedelic effects via stimulation of the serotonin 5-hydroxytryptamine-2A (HT2A) receptor. Administration of the 5-HT2A antagonist ketanserin before LSD almost fully blocks the acute subjective response to LSD. However, unclear is whether ketanserin can also reverse the effects of LSD when administered after LSD.

METHODS

We used a double-blind, randomized, placebo-controlled, crossover design in 24 healthy participants who underwent two 14-hour sessions and received ketanserin (40 mg p.o.) or placebo 1 hour after LSD (100 µg p.o.). Outcome measures included subjective effects, autonomic effects, acute adverse effects, plasma brain-derived neurotrophic factor levels, and pharmacokinetics up to 12 hours.

RESULTS

Ketanserin reversed the acute response to LSD, thereby significantly reducing the duration of subjective effects from 8.5 hours with placebo to 3.5 hours. Ketanserin also reversed LSD-induced alterations of mind, including visual and acoustic alterations and ego dissolution. Ketanserin reduced adverse cardiovascular effects and mydriasis that were associated with LSD but had no effects on elevations of brain-derived neurotrophic factor levels. Ketanserin did not alter the pharmacokinetics of LSD.

CONCLUSIONS

These findings are consistent with an interaction between ketanserin and LSD and the view that LSD produces its psychedelic effects only when occupying 5-HT2A receptors. Ketanserin can effectively be used as a planned or rescue option to shorten and attenuate the LSD experience in humans in research and LSD-assisted therapy.

TRIAL REGISTRY

ClinicalTrials.gov (NCT04558294).

Effects of 3,4-Methylenedioxymethamphetamine on Conditioned Fear Extinction and Retention in a Crossover Study in Healthy Subjects

Background: 3,4-Methylenedioxymethamphetamine (MDMA) has shown initial promise as an adjunct in psychotherapy to treat posttraumatic stress disorder (PTSD). Its efficacy and safety have been demonstrated across phase I-III studies. However, the mechanism underlying the potential utility of MDMA to treat PTSD in humans has not yet been thoroughly investigated. Preliminary evidence suggests that MDMA may facilitate fear extinction recall, which may be through the release of oxytocin. To test this hypothesis, we examined the efficacy of acute MDMA treatment to enhance fear extinction learning and recall. Methods: We used a two-period, double-blind, randomized, placebo-controlled crossover design in 30 healthy male subjects who received a placebo and a single dose of MDMA (125 mg). Fear extinction was tested using two separate Pavlovian fear conditioning paradigms, one using skin conductance response (SCR), and the other fear-potentiated startle (FPS) to conditioned cues. MDMA treatment occurred after fear conditioning and 2 h before extinction learning. Extinction recall was tested 23 h after MDMA intake. Additional outcome measures included subjective effects, emotion recognition tasks, plasma levels of oxytocin, and pharmacokinetics. Results: Fear conditioning and extinction learning were successful in both fear extinction paradigms (generalized eta-squared [ges] for SCR: 0.08; FPS: 0.07). Compared to placebo treatment, MDMA treatment significantly reduced SCRs to the reinforced conditioned stimulus (CS+) during extinction learning (ges = 0.03) and recall (ges = 0.06). Intensity of the subjective effects of MDMA (good effect, trust, and openness) during extinction learning negatively correlated with the discrimination between CS+ and the safety stimulus (CS-) during recall. MDMA did not influence FPS to conditioned cues. Oxytocin concentration was increased fourfold on average by MDMA during acute effects but was not associated with fear extinction outcomes. Conclusions: MDMA treatment facilitated rapid fear extinction and retention of extinction as measured by SCR to fear cues, in line with animal studies of MDMA facilitation of extinction. However, this effect may be limited to certain forms of learned fear responses, as it was not observed in the extinction model using startle reactivity as the outcome. This study provides further evidence for the facilitation of extinction with MDMA treatment and suggests this may be a component of its efficacy when paired with psychotherapy. Clinical Trial registration: clinicaltrials.gov identifier: NCT03527316.

Direct comparison of the acute effects of lysergic acid diethylamide and psilocybin in a double-blind placebo-controlled study in healthy subjects

Growing interest has been seen in using lysergic acid diethylamide (LSD) and psilocybin in psychiatric research and therapy. However, no modern studies have evaluated differences in subjective and autonomic effects of LSD and psilocybin or their similarities and dose equivalence. We used a double-blind, randomized, placebo-controlled, crossover design in 28 healthy subjects (14 women, 14 men) who underwent five 25 h sessions and received placebo, LSD (100 and 200 µg), and psilocybin (15 and 30 mg). Test days were separated by at least 10 days. Outcome measures included self-rating scales for subjective effects, autonomic effects, adverse effects, effect durations, plasma levels of brain-derived neurotrophic factor (BDNF), prolactin, cortisol, and oxytocin, and pharmacokinetics. The doses of 100 and 200 µg LSD and 30 mg psilocybin produced comparable subjective effects. The 15 mg psilocybin dose produced clearly weaker subjective effects compared with both doses of LSD and 30 mg psilocybin. The 200 µg dose of LSD induced higher ratings of ego-dissolution, impairments in control and cognition, and anxiety than the 100 µg dose. The 200 µg dose of LSD increased only ratings of ineffability significantly more than 30 mg psilocybin. LSD at both doses had clearly longer effect durations than psilocybin. Psilocybin increased blood pressure more than LSD, whereas LSD increased heart rate more than psilocybin. However, both LSD and psilocybin showed comparable cardiostimulant properties, assessed by the rate-pressure product. Both LSD and psilocybin had dose-proportional pharmacokinetics and first-order elimination. Both doses of LSD and the high dose of psilocybin produced qualitatively and quantitatively very similar subjective effects, indicating that alterations of mind that are induced by LSD and psilocybin do not differ beyond the effect duration. Any differences between LSD and psilocybin are dose-dependent rather than substance-dependent. However, LSD and psilocybin differentially increased heart rate and blood pressure. These results may assist with dose finding for future psychedelic research.Trial registration: ClinicalTrials.gov identifier: NCT03604744.

Improvement of muscle strength in a mouse model for congenital myopathy treated with HDAC and DNA methyltransferase inhibitors

To date there are no therapies for patients with congenital myopathies, muscle disorders causing poor quality of life of affected individuals. In approximately 30% of the cases, patients with congenital myopathies carry either dominant or recessive mutations in the RYR1 gene; recessive RYR1 mutations are accompanied by reduction of RyR1 expression and content in skeletal muscles and are associated with fiber hypotrophy and muscle weakness. Importantly, muscles of patients with recessive RYR1 mutations exhibit increased content of class II histone de-acetylases and of DNA genomic methylation. We recently created a mouse model knocked-in for the p.Q1970fsX16+p.A4329D RyR1 mutations, which are isogenic to those carried by a severely affected child suffering from a recessive form of RyR1-related multi-mini core disease. The phenotype of the RyR1 mutant mice recapitulates many aspects of the clinical picture of patients carrying recessive RYR1 mutations. We treated the compound heterozygous mice with a combination of two drugs targeting DNA methylases and class II histone de-acetylases. Here we show that treatment of the mutant mice with drugs targeting epigenetic enzymes improves muscle strength, RyR1 protein content and muscle ultrastructure. This study provides proof of concept for the pharmacological treatment of patients with congenital myopathies linked to recessive RYR1 mutations.

Targeting immunoliposomes to EGFR-positive glioblastoma

Background

We assessed the capacity of epidermal growth factor receptor (EGFR)-targeted immunoliposomes to deliver cargo to brain tumor tissue in patients with relapsed glioblastoma harboring an EGFR amplification. We aimed to assess the tolerability and effectiveness of anti-EGFR immunoliposomes loaded with doxorubicin (anti-EGFR ILs-dox) in glioblastoma multiforme patients.

Patients and methods

Patients with EGFR-amplified, relapsed glioblastoma were included in this phase I pharmacokinetic trial. Patients received up to four cycles of anti-EGFR ILs-dox. Twenty-four hours later, plasma and cerebrospinal fluid (CSF) samples were obtained. In addition, we also treated three patients with anti-EGFR ILs-dox before resection of their relapsed glioblastoma. Doxorubicin concentrations were measured in plasma, CSF, and tumor tissue. Safety and efficacy parameters were also obtained.

Results

There were no or negligible levels of doxorubicin found in the CSF demonstrating that anti-EGFR ILs-dox are not able to cross the blood–brain barrier (BBB). However, significant levels were detected in glioblastoma tissue 24 h after the application, indicating that the disruption of BBB integrity present in high-grade gliomas might enable liposome delivery into tumor tissue. No new safety issues were observed. The median progression-free survival was 1.5 months and the median overall survival was 8 months. One patient undergoing surgery had a very long remission suggesting that neoadjuvant administration may have a positive effect on outcome.

Conclusions

We clearly demonstrate that anti-EGFR-immunoliposomes can be targeted to EGFR-amplified glioblastoma and cargo—in this case doxorubicin—can be delivered, although these immunoliposomes do not cross the intact BBB. (The GBM-LIPO trial was registered as NCT03603379).

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Human pharmacokinetic and pharmacodynamic data for EGFR-targeted immunoliposomes.

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Demonstration of delivery of immunoliposomes to glioblastoma tissue.

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EGFR as a target to deliver drug-containing nanoparticles to glioma tissue.

Acute Effects of Psilocybin After Escitalopram or Placebo Pretreatment in a Randomized, Double-Blind, Placebo-Controlled, Crossover Study in Healthy Subjects

The psychedelic psilocybin is being investigated for the treatment of depression and anxiety. Unclear is whether antidepressant treatments interact with psilocybin. The present study used a double‐blind, placebo‐controlled, crossover design with two experimental test sessions to investigate the response to psilocybin (25 mg) in healthy subjects after pretreatment with escitalopram or placebo. The treatment order was random and counterbalanced. Pretreatment consisted of 10 mg escitalopram daily for 7 days, followed by 20 mg daily for 7 days, including the day of psilocybin administration, or 14 days of placebo pretreatment before psilocybin administration. Psilocybin treatments were separated by at least 16 days. The outcome measures included self‐rating scales that evaluated subjective effects, autonomic effects, adverse effects, plasma brain‐derived neurotrophic factor (BDNF) levels, electrocardiogram QTc time, whole‐blood HTR2A and SCL6A4 gene expression, and pharmacokinetics. Escitalopram pretreatment had no relevant effect on positive mood effects of psilocybin but significantly reduced bad drug effects, anxiety, adverse cardiovascular effects, and other adverse effects of psilocybin compared with placebo pretreatment. Escitalopram did not alter the pharmacokinetics of psilocin. The half‐life of psychoactive free (unconjugated) psilocin was 1.8 hours (range 1.1–2.2 hours), consistent with the short duration of action of psilocybin. Escitalopram did not alter HTR2A or SCL6A4 gene expression before psilocybin administration, QTc intervals, or circulating BDNF levels before or after psilocybin administration. Further studies are needed with a longer antidepressant pretreatment time and patients with psychiatric disorders to further define interactions between antidepressants and psilocybin.

Cytochrome P450 1A2 is the most important enzyme for hepatic metabolism of the metamizole metabolite 4-methylaminoantipyrine

Aims

Metamizole (dipyrone) is a prodrug not detectable in serum or urine after oral ingestion. The primary metabolite, 4‐methylaminoantipyrine (4‐MAA), can be N‐demethylated to 4‐aminoantipyrine (4‐AA) or oxidized to 4‐formylaminoantipyrine (4‐FAA) by cytochrome P450 (CYP)‐dependent reactions. We aimed to identify the CYPs involved in 4‐MAA metabolism and to quantify the effect of CYP inhibition on 4‐MAA metabolism.

Methods

We investigated the metabolism of 4‐MAA in vitro using CYP expressing supersomes and the pharmacokinetics of metamizole in the presence of CYP inhibitors in male subjects.

Results

The experiments in supersomes revealed CYP1A2 as the major CYP for 4‐MAA N‐demethylation and 4‐FAA formation with CYP2C19 and CYP2D6 contributing to N‐demethylation. In the clinical study, we investigated the influence of ciprofloxacin (CYP1A2 inhibitor), fluconazole (CYP2C19 inhibitor) and the combination ciprofloxacin/fluconazole on the pharmacokinetics of metamizole in n = 12 male subjects in a randomized, placebo‐controlled, double‐blind study. The geometric mean ratios for the area under the concentration–time curve of 4‐MAA after/before treatment were 1.17 (90% CI 1.09–1.25) for fluconazole, 1.51 (90% CI 1.42–1.60) for ciprofloxacin and 1.92 (90% CI 1.81–2.03) for ciprofloxacin/fluconazole. Fluconazole increased the half‐life of 4‐MAA from 3.22 hours by 0.47 hours (95% CI 0.13–0.81, P < .05), ciprofloxacin by 0.69 hours (95% CI 0.44–0.94, P < .001) and fluconazole/ciprofloxacin by 2.85 hours (95% CI 2.48–3.22, P < .001).

Conclusion

CYP1A2 is the major CYP for the conversion of 4‐MAA to 4‐AA and 4‐FAA. The increase in 4‐MAA exposure by the inhibition of CYP1A2 and by the combination CYP1A2/CYP2C19 may be relevant for dose‐dependent adverse reactions of 4‐MAA.

Comparative Effects of Metamizole (Dipyrone) and Naproxen on Renal Function and Prostacyclin Synthesis in Salt-Depleted Healthy Subjects - A Randomized Controlled Parallel Group Study

Aim: The objective was to investigate the effect of metamizole on renal function in healthy, salt-depleted volunteers. In addition, the pharmacokinetics of the four major metamizole metabolites were assessed and correlated with the pharmacodynamic effect using urinary excretion of the prostacyclin metabolite 6-keto-prostaglandin F1α. Methods: Fifteen healthy male volunteers were studied in an open-label randomized controlled parallel group study. Eight subjects received oral metamizole 1,000 mg three times daily and seven subjects naproxen 500 mg twice daily for 7 days. All subjects were on a low sodium diet (50 mmol sodium/day) starting 1 week prior to dosing until the end of the study. Glomerular filtration rate was measured using inulin clearance. Urinary excretion of sodium, potassium, creatinine, 6-keto-prostaglandin F1α, and pharmacokinetic parameters of naproxen and metamizole metabolites were assessed after the first and after repeated dosing. Results: In moderately sodium-depleted healthy subjects, single or multiple dose metamizole or naproxen did not significantly affect inulin and creatinine clearance or sodium excretion. Both drugs reduced renal 6-keto-prostaglandin F1α excretion after single and repeated dosing. The effect started 2 h after intake, persisted for the entire dosing period and correlated with the concentration-profile of naproxen and the active metamizole metabolite 4-methylaminoantipyrine (4-MAA). PKPD modelling indicated less potent COX-inhibition by 4-MAA (EC₅₀ 0.69 ± 0.27 µM) compared with naproxen (EC₅₀ 0.034 ± 0.033 µM). Conclusions: Short term treatment with metamizole or naproxen has no significant effect on renal function in moderately sodium depleted healthy subjects. At clinically relevant doses, 4-MAA and naproxen both inhibit COX-mediated renal prostacyclin synthesis.

The effect of food on the pharmacokinetics of oral ivermectin

BACKGROUND

Ivermectin is an older anthelminthic agent that is being studied more intensely given its potential for mass drug administration against scabies, malaria and other neglected tropical diseases. Its pharmacokinetics (PK) remain poorly characterized. Furthermore, the majority of PK trials are performed under fasted-state dosing conditions, and the effect of food is therefore not well known. To better plan and design field trials with ivermectin, a model that can account for both conditions would be valuable.

OBJECTIVES

To develop a PK model and characterize the food effect with single oral doses of ivermectin.

PATIENTS AND METHODS

We performed a population-based PK analysis of data pooled from two previous trials of a single dose of 12 mg ivermectin, one with dosing after a high-fat breakfast (n=12) and one with fasted-state dosing (n=3).

RESULTS

The final model described concentration-time profiles after fed and fasted dosing accurately, and estimated the food effect associated with relative bioavailability to 1.18 (95% CI 1.10-1.67).

CONCLUSIONS

In this analysis, the effect of a high-fat breakfast compared with a fasted-state administration of a single oral dose of 12 mg ivermectin was minimal.

Effect of Liver Cirrhosis on the Pharmacokinetics, Metabolism, and Tolerability of Daridorexant, A Novel Dual Orexin Receptor Antagonist

BACKGROUND AND OBJECTIVE

Daridorexant is a dual orexin receptor antagonist in clinical development for insomnia. As daridorexant is cleared mainly via cytochrome P450 (CYP) 3A4, the effect of hepatic impairment on the pharmacokinetics (PK), metabolism, and tolerability of daridorexant was evaluated. Sleep disorders are common in patients with liver cirrhosis and, therefore, sleep-promoting drugs with a better tolerability than currently available would be preferable, a premise that dual orexin receptor antagonists may fulfill.

METHODS

This was a single-dose, open-label, phase I study. Subjects with mild (Child-Pugh A, N = 8) or moderate (Child-Pugh B, N = 8) liver cirrhosis and matched healthy control subjects (N = 8) received 25 mg of daridorexant orally. Blood samples were collected for 72 h post-dose for PK assessments of daridorexant and three major metabolites.

RESULTS

Compared with healthy subjects, patients showed a decrease in total daridorexant area under the plasma concentration-time curve from zero to infinity (AUC_0-inf) and maximum plasma concentration with a geometric mean ratio (GMR, 90% confidence interval [CI]) of 0.51 (0.28-0.92) and 0.50 (0.35-0.72) in Child-Pugh A and 0.74 (0.39-1.41) and 0.42 (0.29-0.60) in Child-Pugh B patients, respectively. Furthermore, the median time to reach maximum plasma concentration was slightly delayed (1.0 h [90% CI 0.0-2.0] in Child-Pugh A patients and 0.5 h [90% CI 0.0-1.5] in Child-Pugh B patients), while for Child-Pugh B patients, a doubling in half-life was observed (GMR [90% CI]: 2.09 [1.32-3.30]). Considering the high plasma protein binding (> 99%) and a 1.9-fold to 2.3-fold increase in the unbound fraction in patients, the PK of unbound daridorexant was also assessed. Compared with healthy subjects, Child-Pugh B patients had a higher AUC_0-inf (GMR [90% CI] 1.60 [0.93-2.73]), a lower apparent plasma clearance (GMR [90% CI] 0.63 [0.37-1.07]), and the same doubling in the half-life observed for total daridorexant, whereas maximum plasma concentration and apparent volume of distribution were not different. Unbound daridorexant PK in Child-Pugh A patients did not differ from healthy subjects. In addition, the metabolic ratios (parent to metabolite), i.e., a marker of CYP 3A4 activity, of the two most abundant daridorexant metabolites were higher in patients with liver cirrhosis compared with healthy subjects. All treatment-emergent adverse events were transient and of mild or moderate intensity and no other treatment-related effects were apparent.

CONCLUSIONS

No safety issue of concern was detected following administration of 25 mg of daridorexant in the study population. Moderate liver cirrhosis causes impaired hepatic clearance of unbound daridorexant, which prolongs the half-life. A 25-mg dose of daridorexant should, therefore, not be exceeded in Child-Pugh B patients. A dose adjustment is not required in Child-Pugh A patients, while avoidance of daridorexant in patients with Child-Pugh C cirrhosis is recommended.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT03713242.

Effect of deglucuronidation on the results of the Basel phenotyping cocktail

We investigated the effect of deglucuronidation on the plasma concentration of the constituents of the Basel phenotyping cocktail and on the interpretation of the phenotyping results under basal conditions and after cytochrome P450 (CYP) induction with metamizole. The cocktail containing caffeine (CYP1A2), efavirenz (CYP2B6), flurbiprofen (CYP2C9), omeprazole (CYP2C19), metoprolol (CYP2D6) and midazolam (CYP3A4) was administered to 12 healthy subjects before (basal) and after treatment with metamizole for 1 week. In the basal state, deglucuronidation caused an increase in the plasma concentrations and area under the curve (AUC) of metoprolol, 8'-hydroxyefavirenz, 4'-hydroxyflurbiprofen and 1'-hydroxymidazolam. This effect could be visualized in Bland-Altman plots, where the values for 8'-hydroxyefavirenz, 4'-hydroxyflurbiprofen and 1'-hydroxymidazolam were mostly above the +20% threshold. As a result, the metabolic ratio (MR), calculated as AUC_{parent drug} /AUC_metabolite , decreased with deglucuronidation for CYP2B6, CYP2C9 and CYP3A4 and increased for CYP2D6. Treatment with metamizole, a constitutive androstane receptor-dependent inducer of CYP2B6, CYP2C9, CYP2C19 and CYP3A4, accentuated the effect of deglucuronidation on AUC and MR. The correlation of MRs calculated as the plasma concentration ratio parent drug/metabolite with the MR calculated as the AUC ratio showed that 1 sample obtained between 2 and 6 hours after cocktail ingestion and analysed with and without deglucuronidation is sufficient to obtain reliable phenotyping results. Importantly, CYP2C9 and 3A4 induction would have been missed without deglucuronidation of the plasma samples. In conclusion, deglucuronidation of the plasma samples improves the stability of the phenotyping results of the Basel phenotyping cocktail and is necessary to reliably detect CYP induction.

Potential metabolic resistance mechanisms to ivermectin in Anopheles gambiae: a synergist bioassay study

Background

Despite remarkable success obtained with current malaria vector control strategies in the last 15 years, additional innovative measures will be needed to achieve the ambitious goals for malaria control set for 2030 by the World Health Organization (WHO). New tools will need to address insecticide resistance and residual transmission as key challenges. Endectocides such as ivermectin are drugs that kill mosquitoes which feed on treated subjects. Mass administration of ivermectin can effectively target outdoor and early biting vectors, complementing the still effective conventional tools. Although this approach has garnered attention, development of ivermectin resistance is a potential pitfall. Herein, we evaluate the potential role of xenobiotic pumps and cytochrome P450 enzymes in protecting mosquitoes against ivermectin by active efflux and metabolic detoxification, respectively.

Methods

We determined the lethal concentration 50 for ivermectin in colonized Anopheles gambiae; then we used chemical inhibitors and inducers of xenobiotic pumps and cytochrome P450 enzymes in combination with ivermectin to probe the mechanism of ivermectin detoxification.

Results

Dual inhibition of xenobiotic pumps and cytochromes was found to have a synergistic effect with ivermectin, greatly increasing mosquito mortality. Inhibition of xenobiotic pumps alone had no effect on ivermectin-induced mortality. Induction of xenobiotic pumps and cytochromes may confer partial protection from ivermectin.

Conclusion

There is a clear pathway for development of ivermectin resistance in malaria vectors. Detoxification mechanisms mediated by cytochrome P450 enzymes are more important than xenobiotic pumps in protecting mosquitoes against ivermectin.

The pharmacokinetics and drug-drug interactions of ivermectin in Aedes aegypti mosquitoes

Mosquitoes are vectors of major diseases such as dengue fever and malaria. Mass drug administration of endectocides to humans and livestock is a promising complementary approach to current insecticide-based vector control measures. The aim of this study was to establish an insect model for pharmacokinetic and drug-drug interaction studies to develop sustainable endectocides for vector control. Female Aedes aegypti mosquitoes were fed with human blood containing either ivermectin alone or ivermectin in combination with ketoconazole, rifampicin, ritonavir, or piperonyl butoxide. Drug concentrations were quantified by LC-MS/MS at selected time points post-feeding. Primary pharmacokinetic parameters and extent of drug-drug interactions were calculated by pharmacometric modelling. Lastly, the drug effect of the treatments was examined. The mosquitoes could be dosed with a high precision (%CV: ≤13.4%) over a range of 0.01–1 μg/ml ivermectin without showing saturation (R²: 0.99). The kinetics of ivermectin were characterised by an initial lag phase of 18.5 h (CI_90%: 17.0–19.8 h) followed by a slow zero-order elimination rate of 5.5 pg/h (CI_90%: 5.1–5.9 pg/h). By contrast, ketoconazole, ritonavir, and piperonyl butoxide were immediately excreted following first order elimination, whereas rifampicin accumulated over days in the mosquitoes. Ritonavir increased the lag phase of ivermectin by 11.4 h (CI_90%: 8.7–14.2 h) resulting in an increased exposure (+29%) and an enhanced mosquitocidal effect. In summary, this study shows that the pharmacokinetics of drugs can be investigated and modulated in an Ae. aegypti animal model. This may help in the development of novel vector-control interventions and further our understanding of toxicology in arthropods.

Mosquitoes are responsible for the transmission of pathogens, which cause diseases that are of major health significance such as dengue fever and malaria. Preventive strategies involving the use of insecticides, however, have led to the emergence of resistant mosquitoes. Consequently, development of complementary approaches is urgently needed to stop the spread of these pathogens. Our study reports on a pioneering approach to investigate how well drugs are taken up by the mosquitoes and how long they reside in their body. We focused on ivermectin, which is toxic for mosquitoes, and several drugs that interfere with drug metabolising enzymes. We demonstrated that the exposure of drugs can be precisely determined in individual mosquitoes and that drugs interact with each other in the same way as observed in vertebrates. In this regard, we were able to increase the exposure and mosquito toxicity of ivermectin by co-administering ritonavir, a broad-spectrum inhibitor of drug metabolising enzymes. This study establishes Aedes mosquitoes as a new model organism for pharmacokinetic studies. It opens the door for the investigation of novel insecticide strategies and optimisation of lead compounds against mosquitoes.

Acute dose-dependent effects of lysergic acid diethylamide in a double-blind placebo-controlled study in healthy subjects

Growing interest has been seen in using lysergic acid diethylamide (LSD) in psychiatric research and therapy. However, no modern studies have evaluated subjective and autonomic effects of different and pharmaceutically well-defined doses of LSD. We used a double-blind, randomized, placebo-controlled, crossover design in 16 healthy subjects (eight women, eight men) who underwent six 25 h sessions and received placebo, LSD (25, 50, 100, and 200 µg), and 200 µg LSD 1 h after administration of the serotonin 5-hydroxytryptamine-2A (5-HT_2A) receptor antagonist ketanserin (40 mg). Test days were separated by at least 10 days. Outcome measures included self-rating scales that evaluated subjective effects, autonomic effects, adverse effects, plasma brain-derived neurotrophic factor levels, and pharmacokinetics up to 24 h. The pharmacokinetic-subjective response relationship was evaluated. LSD showed dose-proportional pharmacokinetics and first-order elimination and dose-dependently induced subjective responses starting at the 25 µg dose. A ceiling effect was observed for good drug effects at 100 µg. The 200 µg dose of LSD induced greater ego dissolution than the 100 µg dose and induced significant anxiety. The average duration of subjective effects increased from 6.7 to 11 h with increasing doses of 25-200 µg. LSD moderately increased blood pressure and heart rate. Ketanserin effectively prevented the response to 200 µg LSD. The LSD dose-response curve showed a ceiling effect for subjective good effects, and ego dissolution and anxiety increased further at a dose above 100 µg. These results may assist with dose finding for future LSD research. The full psychedelic effects of LSD are primarily mediated by serotonin 5-HT_2A receptor activation.

Metamizole is a Moderate Cytochrome P450 Inducer Via the Constitutive Androstane Receptor and a Weak Inhibitor of CYP1A2

Metamizole is an analgesic and antipyretic drug used intensively in certain countries. Previous studies have shown that metamizole induces cytochrome (CYP) 2B6 and possibly CYP3A4. So far, it is unknown whether metamizole induces additional CYPs and by which mechanism. Therefore, we assessed the activity of 6 different CYPs in 12 healthy male subjects before and after treatment with 3 g of metamizole per day for 1 week using a phenotyping cocktail approach. In addition, we investigated whether metamizole induces CYPs by an interaction with the constitutive androstane receptor (CAR) or the pregnane X receptor (PXR) in HepaRG cells. In the clinical study, we confirmed a moderate induction of CYP2B6 (decrease in the efavirenz area under the plasma concentration time curve (AUC) by 79%) and 3A4 (decrease in the midazolam AUC by 68%) by metamizole. In addition, metamizole weakly induced CYP2C9 (decrease in the flurbiprofen AUC by 22%) and moderately CYP2C19 (decrease in the omeprazole AUC by 66%) but did not alter CYP2D6 activity. In addition, metamizole weakly inhibited CYP1A2 activity (1.79‐fold increase in the caffeine AUC). We confirmed these results in HepaRG cells, where 4‐MAA, the principal metabolite of metamizole, induced the mRNA expression of CYP2B6, 2C9, 2C19, and 3A4. In HepaRG cells with a stable knockout of PXR or CAR, we could demonstrate that CYP induction by 4‐MAA depends on CAR and not on PXR. In conclusion, metamizole is a broad CYP inducer by an interaction with CAR and an inhibitor of CYP1A2. Regarding the widespread use of metamizole, these findings are of substantial clinical relevance.

Effects of Hypericum perforatum (St John's wort) on the pharmacokinetics and pharmacodynamics of rivaroxaban in humans

AIMS

To investigate the influence of a cytochrome P450 CYP3A4 and efflux transporter P-glycoprotein (P-gp) inducing Hypericum perforatum extract on the pharmacokinetics and pharmacodynamics of rivaroxaban.

METHODS

Open-label, nonrandomized, sequential treatment interaction study. Following CYP3A4 and P-gp phenotyping using low-dose midazolam and fexofenadine, 12 healthy volunteers received a single oral dose of 20 mg rivaroxaban and rivaroxaban plasma concentrations and inhibition of the activated coagulation factor X (factor Xa) activity were measured prior to and up to 48 h postdosing. The procedures were repeated after 2 weeks' treatment with the H. perforatum extract.

RESULTS

The geometric mean ratios for the area under the concentration-time curve and C_max of rivaroxaban after/before induction with the H. perforatum extract were 0.76 (90% confidence interval [CI] 0.70, 0.82) and 0.86 (90% CI 0.76, 0.97), respectively. Inhibition of factor Xa activity was reduced with a geometric mean area under the effect-time curve ratio after/before induction of 0.80 (90% CI 0.71, 0.89). No clinically significant differences were found regarding T_max (median 1.5 vs 1 h, P = .26) and terminal elimination half-life (mean 10.6 vs 10.8 h, P = .93) of rivaroxaban. The H. perforatum extract significantly induced CYP3A4 and P-gp activity, as evidenced by phenotyping.

CONCLUSION

The CYP3A4/P-gp inducing H. perforatum extract caused a decrease of rivaroxaban exposure with a proportional decrease of the pharmacodynamic effect. Although the data do not justify a contraindication for the combination or a systematic adjustment of rivaroxaban dosage, avoidance of the combination or laboratory monitoring should be considered in patients taking hyperforin-containing H. perforatum extracts with rivaroxaban.

Pharmacokinetics and Pharmacodynamics of Lysergic Acid Diethylamide Microdoses in Healthy Participants

“Microdoses” of lysergic acid diethylamide (LSD) are used recreationally to enhance mood and cognition. Increasing interest has also been seen in developing LSD into a medication. Therefore, we performed a pharmacokinetic‐pharmacodynamic study using very low doses of LSD. Single doses of LSD base (5, 10, and 20 µg) and placebo were administered in a double‐blind, randomized, placebo‐controlled crossover study in 23 healthy participants. Test days were separated by at least 5 days. Plasma levels of LSD and subjective effects were assessed up to 6 hours after administration. Pharmacokinetic parameters were determined using compartmental modeling. Concentration‐subjective effect relationships were described using pharmacokinetic‐pharmacodynamic modeling. Mean (95% confidence interval) maximal LSD concentrations were 151 pg/mL (127–181), 279 pg/mL (243–320), and 500 pg/mL (413–607) after 5, 10, and 20 µg LSD administration, respectively. Maximal concentrations were reached after 1.1 hours. The mean elimination half‐life was 2.7 hours (1.5–6.2). The 5 µg dose of LSD elicited no significant acute subjective effects. The 10 µg dose of LSD significantly increased ratings of “under the influence” and “good drug effect” compared with placebo. These effects began an average of 1.1 hours after 10 µg LSD administration, peaked at 2.5 hours, and ended at 5.1 hours. The 20 µg dose of LSD significantly increased ratings of “under the influence,” “good drug effects,” and “bad drug effects.” LSD concentrations dose‐proportionally increased at doses as low as 5–20 µg and decreased with a half‐life of 3 hours. The threshold dose of LSD base for psychotropic effects was 10 µg.

PGC-1α plays a pivotal role in simvastatin-induced exercise impairment in mice

AIM

Statins decrease cardiovascular complications, but can induce myopathy. Here, we explored the implication of PGC-1α in statin-associated myotoxicity.

METHODS

We treated PGC-1α knockout (KO), PGC-1α overexpression (OE) and wild-type (WT) mice orally with 5 mg simvastatin kg^-1  day^-1 for 3 weeks and assessed muscle function and metabolism.

RESULTS

In WT and KO mice, but not in OE mice, simvastatin decreased grip strength, maximal running distance and vertical power assessed by ergometry. Post-exercise plasma lactate concentrations were higher in WT and KO compared to OE mice. In glycolytic gastrocnemius, simvastatin decreased mitochondrial respiration, increased mitochondrial ROS production and free radical leak in WT and KO, but not in OE mice. Simvastatin increased mRNA expression of Sod1 and Sod2 in glycolytic and oxidative gastrocnemius of WT, but decreased it in KO mice. OE mice had a higher mitochondrial DNA content in both gastrocnemius than WT or KO mice and simvastatin exhibited a trend to decrease the citrate synthase activity in white and red gastrocnemius in all treatment groups. Simvastatin showed a trend to decrease the mitochondrial volume fraction in both muscle types of all treatment groups. Mitochondria were smaller in WT and KO compared to OE mice and simvastatin further reduced the mitochondrial size in WT and KO mice, but not in OE mice.

CONCLUSIONS

Simvastatin impairs skeletal muscle function, muscle oxidative metabolism and mitochondrial morphology preferentially in WT and KO mice, whereas OE mice appear to be protected, suggesting a role of PGC-1α in preventing simvastatin-associated myotoxicity.

Pharmacokinetics and phenotyping properties of the Basel phenotyping cocktail combination capsule in healthy male adults

AIMS

We compared the phenotyping metrics of a combination capsule formulation to its individual components of the newly composed Basel phenotyping cocktail. Moreover, we investigated a reduced sampling regimen for clinical applications.

METHODS

We performed in vitro experiments and a crossover pharmacokinetic study in twelve healthy male subjects to compare the Basel phenotyping cocktail capsule containing 6 cytochrome P450 (CYP) probe drugs with individual administration of the same drugs. Parent compounds and selected metabolites were determined by liquid chromatography-tandem mass spectrometry. Metabolic ratios (MR) for are under the curve (AUC) and single time point measurements and their correlation were determined.

RESULTS

Experiments with human liver microsomes and primary human hepatocytes in 3D co-culture confirmed that flurbiprofen is a suitable CYP2C9 substrate. Both cocktail formulations (capsule and individual probe drug administration) were well-tolerated and yielded reproducible MRs, which were almost identical. Correlations between single time point ratios and the corresponding AUC ratios depended on the sampling time point and the concentration time curve of the probe drugs. The MR of the capsule (Spearman rank correlation coefficient, R_s : 0.77-0.97) as well as the individual components (R_s : 0.69-0.99) correlated best at 6 h post-treatment considering all 6 CYPs. Moreover, the 2-h time points of the capsule agreed suitably with the AUC; however, the MR of omeprazole could not be determined for 10 out of 12 subjects.

CONCLUSION

The capsule is easy to swallow, well tolerated and provides reliable estimates for CYP activity. The optimal sampling point for the capsule formulation is 6 h after intake.

Using dried blood spots to facilitate therapeutic drug monitoring of antiretroviral drugs in resource-poor regions

Objectives

We evaluated whether dried blood spots (DBS) are suitable to monitor combined ART when samples are collected in rural Tanzania and transported over a long distance to a specialized bioanalytical laboratory.

Methods

Plasma and DBS samples were collected in Tanzania from study patients treated with nevirapine, efavirenz or lopinavir. In addition, plasma, whole blood and DBS samples were obtained from a cohort of HIV patients at the site of the bioanalytical laboratory in Switzerland. DBS samples were analysed using a fully automated LC-MS/MS method.

Results

Comparison of DBS versus plasma concentrations of samples obtained from the bridging study in Switzerland indicated an acceptable bias only for nevirapine (18.4%), whereas for efavirenz and lopinavir a pronounced difference of -47.4% and -48.1% was found, respectively. Adjusting the DBS concentrations by the haematocrit and the fraction of drug bound to plasma proteins removed this bias [efavirenz +9.4% (-6.9% to +25.7%), lopinavir +2.2% (-20.0% to +24.2%)]. Storage and transportation of samples from Tanzania to Switzerland did not affect the good agreement between plasma and DBS for nevirapine [-2.9% (-34.7% to +29.0%)] and efavirenz [-9.6% (-42.9% to +23.8%)]. For lopinavir, however, adjusted DBS concentrations remained considerably below [-32.8% (-70.4% to +4.8%)] corresponding plasma concentrations due to decay of lopinavir in DBS obtained under field conditions.

Conclusions

Our field study shows that the DBS technique is a suitable tool for therapeutic drug monitoring in resource-poor regions; however, sample stability remains an issue for certain analytes and therefore needs special consideration.

Dose evaluation of intravenous metamizole (dipyrone) in infants and children: a prospective population pharmacokinetic study

PURPOSE

The prodrug metamizole is prescribed intravenously for postoperative pain in children, including off-label use in infants < 1 year. We aimed to assess the pharmacokinetics of the main metabolites of metamizole in children aged 3-72 months.

METHODS

A single dose of 10 mg/kg metamizole was administered intravenously for postoperative analgesia. Pharmacokinetic samples were drawn at predefined time points. Pharmacokinetics of the main active metabolite 4-methylaminoantipyrine and three other metabolites was characterized by both non-compartmental and population pharmacokinetic analysis. AUC_0-inf of 4-methylaminoantipyrine was calculated by non-compartmental analysis for two age cohorts (3-23 months, 2-6 years) and compared with the 80-125% range of adult dose-adjusted reference exposure (AUC_ref). Population pharmacokinetic analysis investigated age and weight dependency of the pharmacokinetics and optimal dosing strategies to achieve equivalent adult exposure.

RESULTS

A total of 25 children aged 5 months-5.8 years (7.8-24.8 kg) with at least one concentration sample were included; 19 children had ≥ 5 predefined samples up to 10 h after metamizole dose administration. AUC_0-inf of 4-methylaminoantipyrine in children 2-6 years was 29.9 mg/L/h (95% CI 23.4-38.2), significantly lower than AUC_ref (80-125% range 39.2-61.2 mg/L/h). AUC_0-inf of 4-methylaminoantipyrine in infants < 2 years was 43.6 mg/L/h (95% CI 15.8-119.0), comparable with AUC_ref, while infants < 12 months showed increased exposure. Observed variability could be partially explained by covariates weight and age.

CONCLUSIONS

Age-related changes in pharmacokinetics of 4-methylaminoantipyrine requires reduced weight-based IV dosing in infants < 1 year compared with infants and children up to 6 years (5 versus 10-20 mg/kg) to achieve equivalent adult exposure.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT02660177 .

Toxicity of metamizole on differentiating HL60 cells and human neutrophil granulocytes

Metamizole is an analgesic and antipyretic with a superior analgesic efficacy than paracetamol. Since metamizole can cause neutropenia and agranulocytosis, it is currently used in only few countries. In a previous study, we have shown that N-methyl-4-aminoantipyrine (MAA), the active metamizole metabolite, reacts with hemin and forms an electrophilic metabolite that is toxic for HL60 cells, but not for mature neutrophil granulocytes. In the current study, we investigated the toxicity of hemin (12.5 μM) and MAA (100 μM) on differentiating HL60 cells. In undifferentiated HL60 cells, hemin decreased the viability and this effect was significantly increased by MAA. Similarly, hemin/MAA was more toxic than hemin alone on human cord blood cells. At 3 days (metamyelocyte stage) and 5 days of differentiation (mature neutrophils), hemin/MAA was not toxic on HL60 cells, whereas hemin alone was still toxic. No toxicity was observed on freshly isolated human neutrophils. The protein expression of enzymes responsible for hemin metabolism increased with HL60 cell differentiation. Inhibition of heme oxygenase-1 or cytochrome P450 reductase increased the toxicity of hemin and hemin/MAA in undifferentiated, but only for hemin in differentiated HL60 cells. Similar to the enzymes involved in hemin metabolism, the protein expression of enzymes involved in antioxidative defense and the cellular glutathione pool increased with HL60 cell differentiation. In conclusion, HL60 cells become resistant to the toxicity of hemin/MAA and partly also of hemin during their differentiation. This resistance is associated with the development of heme metabolism and of the antioxidative defense system including the cellular glutathione pool.

Pharmacokinetics and subjective effects of a novel oral LSD formulation in healthy subjects

AIMS

The aim of the present study was to characterize the pharmacokinetics and exposure-subjective response relationship of a novel oral solution of lysergic acid diethylamide (LSD) that was developed for clinical use in research and patients.

METHOD

LSD (100 μg) was administered in 27 healthy subjects using a placebo-controlled, double-blind, cross-over design. Plasma levels of LSD, nor-LSD, and 2-oxo-3-hydroxy-LSD (O-H-LSD) and subjective drug effects were assessed up to 11.5 hours.

RESULTS

First-order elimination kinetics were observed for LSD. Geometric mean maximum concentration (C_max ) values (range) of 1.7 (1.0-2.9) ng/mL were reached at a t_max (range) of 1.7 (1.0-3.4) hours after drug administration. The plasma half-life (t_1/2 ) was 3.6 (2.4-7.3) hours. The AUC_∞ was 13 (7.1-28) ng·h/mL. No differences in these pharmacokinetic parameters were found between male and female subjects. Plasma O-H-LSD but not nor-LSD (< 0.01 ng/mL) concentrations could be quantified in all subjects. Geometric mean O-H-LSD C_max values (range) of 0.11 (0.07-0.19) ng/mL were reached at a t_max (range) of 5 (3.2-8) hours. The t_1/2 and AUC_∞ values of O-H-LSD were 5.2 (2.6-21) hours and 1.7 (0.85-4.3) ng·h/mL, respectively. The subjective effects of LSD lasted (mean ± SD) for 8.5 ± 2.0 hours (range: 5.3-12.8 h), and peak effects were reached 2.5 ± 0.6 hours (range 1.6-4.3 h) after drug administration. EC₅₀ values were 1.0 ± 0.5 ng/mL and 1.9 ± 1.0 ng/mL for "good" and "bad" subjective drug effects, respectively.

CONCLUSION

The present study characterized the pharmacokinetics of LSD and its main metabolite O-H-LSD. The subjective effects of LSD were closely associated with changes in plasma concentrations over time.

Cytochrome P450 enzymes contribute to the metabolism of LSD to nor-LSD and 2-oxo-3-hydroxy-LSD: Implications for clinical LSD use

In recent years, experimental research on lysergic acid diethylamide (LSD) in humans has gained new momentum. In humans, LSD is metabolized rapidly into several metabolites but knowledge of the involved metabolizing enzymes is limited. The aim of the current study was to identify the cytochrome P450 (CYP) isoforms involved in the metabolism of LSD to 6-norlysergic acid diethylamide (nor-LSD) and 2-oxo-3-hydroxy-LSD (O-H-LSD) in vitro, in order to evaluate potential effects of enzyme polymorphisms or prescription drugs on LSD pharmacokinetics. Additionally, interactions of LSD and both metabolites with 5-hydroxytryptamine (5-HT) receptors were assessed. LSD was incubated with human liver microsomes over 4 h and the production of nor-LSD and O-H-LSD was quantified by liquid chromatography tandem mass spectrometry. Metabolism was inhibited by the addition of specific CYP inhibitors. Additionally, recombinant CYPs were used to verify the inhibition results obtained with microsomes and induction of metabolism was investigated in human hepatocyte-derived cells. Radioligand binding and calcium mobilization assays were used to determine 5-HT receptor affinities and activities, respectively. Human liver microsomes displayed minor metabolite formation (<1% metabolized) over 4 h. CYP2D6, 2E1, and 3A4 significantly contributed to the formation of nor-LSD, and CYP1A2, 2C9, 2E1, and 3A4 were significantly involved in the formation of O-H-LSD. These findings could be verified using recombinant CYPs. Enzyme induction with rifampicin distinctly increased the formation of both metabolites, whereas treatment with omeprazole only slightly increased formation of nor-LSD. LSD and nor-LSD were pharmacologically active at the 5-HT_1A, 5-HT_2A, 5-HT_2B, and 5-HT_2C receptors. Nor-LSD mainly differed from the parent compound by having a lower affinity to the 5-HT_2C receptor. O-H-LSD displayed substantially weaker affinity and activity at serotonergic receptors in comparison to LSD. To conclude, human liver microsomes converted only small amounts of LSD to nor-LSD and O-H-LSD but several CYPs significantly contributed. Genetic polymorphisms and drug interactions could therefore influence pharmacokinetics and pharmacodynamics of LSD. Nor-LSD likely has hallucinogenic activity similar to LSD, whereas O-H-LSD is inactive. Drug-drug interaction studies in humans are required to further assess the clinical relevance of these findings.

Population pharmacokinetics of oral ivermectin in venous plasma and dried blood spots in healthy volunteers

AIMS

The anthelminthic ivermectin is receiving new attention as it is being repurposed for new indications such as mass drug administrations for the treatment of scabies or in malaria vector control. As its pharmacokinetics are still poorly understood, we aimed to characterize the population pharmacokinetics of ivermectin in plasma and dried blood spots (DBS), a sampling method better suited to field trials, with special focus on the influence of body composition and enterohepatic circulation.

METHODS

We performed a clinical trial in 12 healthy volunteers who each received a single oral dose of 12 mg ivermectin, and collected peripheral venous and capillary DBS samples. We determined ivermectin concentrations in plasma and DBS by liquid chromatography tandem mass spectrometry using a fully automated and scalable extraction system for DBS sample processing. Pharmacokinetic data were analysed using non-linear mixed effects modelling.

RESULTS

A two-compartment model with a transit absorption model, first-order elimination, and weight as an influential covariate on central volume of distribution and clearance best described the data. The model estimates (inter-individual variability) for a 70 kg subject were: apparent population clearance 7.7 (25%) l h^-1 , and central and peripheral volumes of distribution 89 (10%) l and 234 (20%) l, respectively. Concentrations obtained from DBS samples were strongly linearly correlated (R²  = 0.97) with plasma concentrations, and on average 30% lower.

CONCLUSION

The model accurately depicts population pharmacokinetics of plasma and DBS concentrations over time for oral ivermectin. The proposed analytical workflow is scalable and applicable to the requirements of mass drug administrations.

Cytochrome P450 Enzymes Involved in Metoprolol Metabolism and Use of Metoprolol as a CYP2D6 Phenotyping Probe Drug

Metoprolol is used for phenotyping of cytochrome P450 (CYP) 2D6, a CYP isoform considered not to be inducible by inducers of the CYP2C, CYP2B, and CYP3A families such as rifampicin. While assessing CYP2D6 activity under basal conditions and after pre-treatment with rifampicin in vivo, we surprisingly observed a drop in the metoprolol/α-OH-metoprolol clearance ratio, suggesting CYP2D6 induction. To study this problem, we performed in vitro investigations using HepaRG cells and primary human hepatocytes (before and after treatment with 20 μM rifampicin), human liver microsomes, and CYP3A4-overexpressing supersomes. While mRNA expression levels of CYP3A4 showed a 15- to 30-fold increase in both cell models, mRNA of CYP2D6 was not affected by rifampicin. 1'-OH-midazolam formation (reflecting CYP3A4 activity) increased by a factor of 5-8 in both cell models, while the formation of α-OH-metoprolol increased by a factor of 6 in HepaRG cells and of 1.4 in primary human hepatocytes. Inhibition studies using human liver microsomes showed that CYP3A4, 2B6, and 2C9 together contributed 19.0 ± 2.6% (mean ± 95%CI) to O-demethylation, 4.0 ± 0.7% to α-hydroxylation, and 7.6 ± 1.7% to N-dealkylation of metoprolol. In supersomes overexpressing CYP3A4, metoprolol was α-hydroxylated in a reaction inhibited by the CYP3A4-specific inhibitor ketoconazole, but not by the CYP2D6-specific inhibitor quinidine. We conclude that metoprolol is not exclusively metabolized by CYP2D6. CYP3A4, 2B6, and 2C9, which are inducible by rifampicin, contribute to α-hydroxylation, O-demethylation, and N-dealkylation of metoprolol. This contribution is larger after CYP induction by rifampicin but is too small to compromise the usability of metoprolol α-hydroxylation for CYP2D6 phenotyping.