Which Level of Emicizumab Is Necessary for a Good Hemostasis?

Introduction Emicizumab is a recombinant, humanized, bispecific antibody restoring the function of missing activated factor VIII (FVIII) by bridging activated FIX (FIXa) and zymogen factor X (FX), medicating the activation of FX. Emicizumab is approved in several countries, at the doses of 1.5 mg/kg once weekly, 3 mg/kg every 2 weeks or 6 mg/kg every 4 weeks, for the prophylaxis of bleeding episodes in patients with hemophilia A with and without inhibitors. The drug has shown a good efficacy either during registration studies as well as in real-world experiences and was well tolerated without significant side effects. The development of neutralizing anti-emicizumab antibodies has been reported in very few cases which frequently required the switch to other products due to inefficacy of the prophylaxis. Patients maintaining a plasma concentration range of the drug within 30-80 ug/ml did not show significant bleeds. However, real life experiences bring the need of personalization of the drug dose. A recent case series presented at ISTH 2021 from Malaysian authors evaluated the efficacy of a dose of emicizumab between 1.7 and 1.9 mg/kg every 4 weeks, showing that even at a lower dose than that approved could be effective for the prevention of bleeding events. Here we report the case of an adult patient with moderate hemophilia A with inhibitor who developed an anti-emicizumab antibody which reduced the concentration of the drug by 50%. Despite that the patient did not report bleeding events in a follow-up period of 18 weeks. Treatment with emicizumab requires further evaluation to understand the best dose for the prevention of bleeding. Case report A 74 years old patient with moderate hemophilia A (FVIII 1-3%) followed at our Center had history of high-titer inhibitor (maximum titer 20 BU). The patient was treated on-demand with plasma-derived FVIII concentrates, when, in Jul 2000, he developed a neutralizing anti-FVIII antibody requiring treatment with activated prothrombin complex concentrates (Feiba). In Nov 2020 the patient was hospitalized for traumatic brain hemorrhage treated with plasma-derived FVIII (inhibitor titer < 5 BU) and subsequently, for the recurrence of inhibitor, with activated prothrombin complex concentrates. In Feb 2021 the patient started prophylaxis with emicizumab at the initial dose of 3 mg/kg once weekly (loading dose), followed by a maintenance dose of 1.5 mg/kg. The patient underwent periodic blood withdrawal for monitoring drug plasma concentration. In Apr 2021 (week 10) drug concentration showed a slight decrease from initial levels, from 39.1 ug/ml (week 5) to 28.3 (week 10) and a weak positivity for an anti-emicizumab antibody was detected. At the following test (week 15) positivity for the anti-emicizumab antibody was confirmed, witnessed by the consistent reduction in drug plasma concentration up to 20.9 ug/ml. During the following weeks, until week 22, drug plasma concentrations were stable (range 17.0-19.4 ug/ml) and positivity for anti-emicizumab antibody remained, as shown in the table. The results of partial Thromboplastin Time (PTT) were consistent with the drug plasma concentrations during the observation period, in which the patient did not developed any bleeding event. Conclusion This case report may corroborate the hypothesis of the efficacy of a reduced dose of emicizumab in patients with hemophilia A. Close laboratory monitoring in patients in prophylaxis with emicizumab is warranted for the evaluation of drug plasma concentration and the prompt detection of anti-drug antibodies, particularly if patient show a reduced therapeutic efficacy. However, in the absence of bleeding events, positivity for anti-emicizumab antibodies should not bring to sudden drug discontinuation. Indeed, in the view of the above, a lower drug plasma concentration than standard might be effective in the prevention of bleeding. 1. Tang ASO et al. July 2021. Efficacy of Reduced-dose Emicizumab in Haemophilia A with Inhibitors: Real World Experience in East Malaysia. ISTH 2021. Figure 1 Figure 1. Disclosures Peyvandi: Takeda: Consultancy, Honoraria; Sobi: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Roche: Consultancy, Honoraria.

Physiological and Clinical Responses in Pigs in Relation to Plasma Concentrations during Anesthesia with Dexmedetomidine, Tiletamine, Zolazepam, and Butorphanol

Reliable protocols for short-term anesthetics are essential to safeguard animal welfare during medical investigations. The aim of the study was to assess the adequacy and reliability of an anesthetic protocol and to evaluate physiological and clinical responses, in relation to the drug plasma concentrations, for pigs undergoing short-term anesthesia. A second aim was to see whether an intravenous dosage could prolong the anesthesia. The anesthesia was induced by an intramuscular injection of dexmedetomidine, tiletamine zolazepam, and butorphanol in 12 pigs. In six of the pigs, a repeated injection intravenously of one-third of the initial dose was given after one hour. The physiological and clinical effects from induction to recovery were examined. Plasma concentrations of the drugs were analyzed and pharmacokinetic parameters were calculated. Each drug’s absorption and time to maximal concentration were rapid. All pigs were able to maintain spontaneous respiration. The route of administration did not alter the half-life of the drug. The results suggest that intramuscular administration of the four-drug combination provides up to two hours of anesthesia with stable physiological parameters and an acceptable level of analgesia while maintaining spontaneous respiration. A repeated intravenous injection may be used to extend the time of anesthesia by 30 min.

Clozapine Metabolism is Associated With Absolute Neutrophil Count in Individuals With Treatment-Resistant Schizophrenia

Up to one-third of those with schizophrenia fail to respond to standard antipsychotics and are considered to have treatment-resistant schizophrenia, a condition for which clozapine is the only evidence-based medication. While up to 60% of treated individuals obtain therapeutic benefits from clozapine, it is currently underprescribed worldwide, partly because of concerns related to its broad adverse effect profile. In particular, the potential effects of clozapine on the immune system have gained relevance after a recent study showed that drug plasma concentrations were inversely correlated with neutrophil counts in individuals routinely undergoing treatment. Seeking to investigate this relationship in more detail, we extracted metabolic, immune, and genetic data from a UK cohort of long-term clozapine users linked to a clozapine monitoring service, CLOZUK2 (N = 208). Whilst a correlation analysis was compatible with the original results, a multiple linear regression accounting for dose and other confounding factors additionally allowed us to estimate the decrease in absolute neutrophil counts to approximately 141 cells/mm3 for every 0.1 mg/L increase in clozapine concentration. However, this association was attenuated after controlling for the metabolic ratio between clozapine and its main metabolite, norclozapine, which was itself negatively associated with neutrophil concentrations. Further analyses revealed that these relationships are likely moderated by genetic factors, as three pharmacogenomic SNPs previously associated to norclozapine plasma concentrations and the metabolic ratio (rs61750900, rs2011425 and rs1126545) were shown to be independently associated with a variation in neutrophil counts of about 400 cells/mm3 per effect allele. Such results are compatible with an effect of norclozapine, but not necessarily clozapine, on immune cell counts, and highlight the need for further investigations into the potential role of genetic determinants of clozapine pharmacokinetics in the occurrence of adverse effects during treatment.

Flow Cytometric Assessment of Endothelial and Platelet Microparticles in Patients With Atrial Fibrillation Treated With Dabigatran

The prothrombotic state in patients with atrial fibrillation (AF) is related to endothelial injury, the activation of platelets and the coagulation cascade. We evaluated the levels of platelet- (CD42b) and endothelial-derived (CD144) microparticles in the plasma patients with non-valvular AF treated with dabigatran at the time of expected minimum and maximum drug plasma concentrations. Following that, we determined the peak dabigatran plasma concentration (cpeak ). CD42b increased after taking dabigatran (median [IQR] 36.7 [29.4-53.3] vs. 45.6 [32.3-59.5] cells/µL; p = 0.025). The concentration of dabigatran correlated negatively with the post-dabigatran change in CD42b (ΔCD42b, r = -0.47, p = 0.021). In the multivariate model, the independent predictors of ΔCD42b were: cpeak (HR -0.55; with a 95% confidence interval, CI [-0.93, -0.16]; p = 0.007), coronary artery disease (CAD) (HR -0.41; 95% CI [-0.79, -0.02]; p = 0.037) and peripheral artery disease (PAD) (HR 0.42; 95% CI [0.07, 0.74]; p = 0.019). CD144 did not increase after dabigatran administration. These data suggest that low concentrations of dabigatran may be associated with platelet activation. PAD and CAD have distinct effects on CD42b levels during dabigatran treatment.

Neural correlates of the DMT experience assessed with multivariate EEG

Studying transitions in and out of the altered state of consciousness caused by intravenous (IV) N,N-Dimethyltryptamine (DMT - a fast-acting tryptamine psychedelic) offers a safe and powerful means of advancing knowledge on the neurobiology of conscious states. Here we sought to investigate the effects of IV DMT on the power spectrum and signal diversity of human brain activity (6 female, 7 male) recorded via multivariate EEG, and plot relationships between subjective experience, brain activity and drug plasma concentrations across time. Compared with placebo, DMT markedly reduced oscillatory power in the alpha and beta bands and robustly increased spontaneous signal diversity. Time-referenced and neurophenomenological analyses revealed close relationships between changes in various aspects of subjective experience and changes in brain activity. Importantly, the emergence of oscillatory activity within the delta and theta frequency bands was found to correlate with the peak of the experience - particularly its eyes-closed visual component. These findings highlight marked changes in oscillatory activity and signal diversity with DMT that parallel broad and specific components of the subjective experience, thus advancing our understanding of the neurobiological underpinnings of immersive states of consciousness.

Neural correlates of the DMT experience as assessed via multivariate EEG

Studying transitions in and out of the altered state of consciousness caused by intravenous (IV) N,N-Dimethyltryptamine (DMT – a fast-acting tryptamine psychedelic) offers a safe and powerful means of advancing knowledge on the neurobiology of conscious states. Here we sought to investigate the effects of IV DMT on the power spectrum and signal diversity of human brain activity (6 female, 7 male) recorded via multivariate EEG, and plot relationships between subjective experience, brain activity and drug plasma concentrations across time. Compared with placebo, DMT markedly reduced oscillatory power in the alpha and beta bands and robustly increased spontaneous signal diversity. Time-referenced analyses revealed close relationships between changes in various aspects of subjective experience and changes in brain activity. Importantly, the emergence of oscillatory activity within the delta and theta frequency bands was found to correlate with the peak of the experience, and particularly its eyes-closed visual component. These findings highlight marked changes in oscillatory activity and signal diversity with DMT that parallel broad and specific components of the relevant subjective experience and thus further our understanding of the neurobiological underpinnings of immersive states of consciousness.

Point-of-Care Coagulation Tests Monitoring of Direct Oral Anticoagulants and Their Reversal Therapy: State of the Art

Direct oral anticoagulants (DOACs) exert similar anticoagulant effects to vitamin K antagonists and are increasingly used worldwide. Nevertheless, an evidence-based approach to patients receiving DOACs when any unplanned urgent surgery or bleeding (either spontaneous or traumatic) occurs is still missing. In this review, we investigate the role of point-of-care coagulation tests when other, more specific tests are not available. Indeed, thromboelastography and activated clotting time can detect dabigatran-induced coagulopathy, while their accuracy is limited for apixaban and rivaroxaban, mostly in cases of low drug plasma concentrations. These tests can also be used to guide the reversal of DOAC-induced coagulopathy providing a quick, before-and-after picture in case of therapeutic use of hemostatic compounds.

Bioequivalence Study of Modified-Release Gliclazide Tablets in Healthy Volunteers

This study was aimed to investigate bioequivalence of modified-release 30 mg gliclazide tablets in 18 healthy Thai volunteers. A test product, Glycon MR (Siam Bheasach, TH), was compared with a reference product, Diamicron MR (Servier, France). The study was performed under a single-dose, two-treatment, two-period, and two-sequence crossover design in fasted and fed conditions with a washout period of 2 weeks. Blood samples were collected for 72 h after drug administration. Drug plasma concentrations were determined by HPLC with a UV detector. Analysis of pharmacokinetic characteristics was based on a non-compartmental model. The logarithmically transformed data of Cmax and AUCs were analyzed for 90% confidence intervals using ANOVA. The test product gave slightly higher Cmax in both conditions and shorter Tmax in the fed condition. However, there is no significant difference in pharmacokinetic characteristics between both products under fasted and fed conditions. Effect of food was not significantly observed. The 90% confidence intervals were within the acceptance criteria of 0.80–1.25 regardless of the food effect, indicating bioequivalence between the two products on the rate and extent of gliclazide MR absorption without regard to meals.