Eculizumab precision dosing algorithm for thrombotic microangiopathy in children and young adults undergoing HSCT

Transplant-associated thrombotic microangiopathy (TA-TMA) is a fatal post-transplant complication of hematopoietic stem cell transplantation (HSCT). We recently reported that survival for TA-TMA has been improved by early intervention with eculizumab, a complement C5 inhibitor, guided by pharmacokinetic/pharmacodynamic (PK/PD) model-informed precision dosing. However, patients with gastrointestinal (GI) bleeding showed poor survival even when treated with more frequent dosing. Our objective was to develop separate models in bleeding and non-bleeding TA-TMA patients and propose precision dosing algorithms. Eculizumab PK/PD were analyzed in 19 bleeding and 38 non-bleeding patients (0.5-29.9 years). A complement activation biomarker (sC5b-9) and bodyweight were identified as significant determinants of eculizumab clearance regardless of bleeding. Eculizumab clearance after the first dose was higher in bleeding patients than in non-bleeding patients (83.8 vs. 61.3 mL/h/70kg, p=0.07). The high clearance was maintained over treatment doses in bleeding patients, whereas non-bleeding patients showed a time-dependent decrease in clearance. sC5b-9 levels were highest before the first dose and decreased over time regardless of bleeding complications. A Monte Carlo Simulation analysis showed that the current dosing protocols recommended for aHUS had less than 15% probability of eculizumab target concentration attainment of >100 g/mL in non-bleeding patients. This study identified an intensified loading protocol to reach 80% target attainment. Our data clearly showed the need for individualized dosing for patients with significant bleeding, and for ongoing dose adjustments to optimize outcomes. The developed models will be incorporated into a clinical decision support for precision dosing to improve outcomes in children and young adults with TA-TMA.

Higher teicoplanin blood level needed in elderly critically ill patients

Background: Significant changes in the pathophysiology of older critically ill patients may affect the pharmacokinetics and pharmacodynamics of teicoplanin. This study aimed to determine the optimal teicoplanin blood level in this patient population. Materials & Methods: 128 older critically ill and 86 older non-critically ill patients were involved and analyzed. Results: The target thresholds of teicoplanin blood concentrations in older critically ill patients and non-critically ill patients should be 31.4mg/L and 15.3mg/L, respectively. The dose of teicoplanin in older critically ill patients should be greater than 800 mg to achieve the target blood level. Conclusion : An individualized dosing approach of teicoplanin based on therapeutic drug monitoring is necessary for older critically ill patients.

Cerebrospinal Fluid Concentrations of Meropenem and Vancomycin in Ventriculitis Patients Obtained by TDM-Guided Continuous Infusion

Effective antibiotic therapy of cerebral infections such as meningitis or ventriculitis is hindered by low penetration into the cerebrospinal fluid (CSF). Because continuous infusion of meropenem and vancomycin and routine therapeutic drug monitoring (TDM) have been proposed to optimize antimicrobial exposure in ventriculitis patients, an individualized dosing strategy was implemented in our department. We present a retrospective analysis of meropenem and vancomycin concentrations in serum and CSF in the first nine ventriculitis patients treated with continuous infusion and TDM-guided dose optimization aiming at 20–30 mg/L. Median initial dosing was 8.8 g/24 h meropenem and 4.25 g/24 h vancomycin, respectively, resulting in median serum concentrations of 21.3 mg/L for meropenem and 24.5 mg/L for vancomycin and CSF concentrations of 3.4 mg/L for meropenem and 1.7 mg/L for vancomycin. Median CSF penetration was 15% for meropenem and 7% for vancomycin. With initial dosing, all but one patient achieved CSF concentrations above 1 mg/L. Dose adjustment according to TDM ensured sufficient CSF concentrations in all patients within 48 h of treatment. Given the limited penetration, continuous infusion of meropenem and vancomycin based on renal function and TDM-guided dose optimization appears a reasonable approach to attain sufficient CSF concentrations in ventriculitis patients.

Update on Intravenous Immunoglobulin in Neurology: Modulating Neuro-autoimmunity, Evolving Factors on Efficacy and Dosing and Challenges on Stopping Chronic IVIg Therapy

In the last 25 years, intravenous immunoglobulin (IVIg) has had a major impact in the successful treatment of previously untreatable or poorly controlled autoimmune neurological disorders. Derived from thousands of healthy donors, IVIg contains IgG1 isotypes of idiotypic antibodies that have the potential to bind pathogenic autoantibodies or cross-react with various antigenic peptides, including proteins conserved among the “common cold”-pre-pandemic coronaviruses; as a result, after IVIg infusions, some of the patients’ sera may transiently become positive for various neuronal antibodies, even for anti-SARS-CoV-2, necessitating caution in separating antibodies derived from the infused IVIg or acquired humoral immunity. IVIg exerts multiple effects on the immunoregulatory network by variably affecting autoantibodies, complement activation, FcRn saturation, FcγRIIb receptors, cytokines, and inflammatory mediators. Based on randomized controlled trials, IVIg is approved for the treatment of GBS, CIDP, MMN and dermatomyositis; has been effective in, myasthenia gravis exacerbations, and stiff-person syndrome; and exhibits convincing efficacy in autoimmune epilepsy, neuromyelitis, and autoimmune encephalitis. Recent evidence suggests that polymorphisms in the genes encoding FcRn and FcγRIIB may influence the catabolism of infused IgG or its anti-inflammatory effects, impacting on individualized dosing or efficacy. For chronic maintenance therapy, IVIg and subcutaneous IgG are effective in controlled studies only in CIDP and MMN preventing relapses and axonal loss up to 48 weeks; in practice, however, IVIg is continuously used for years in all the aforementioned neurological conditions, like is a “forever necessary therapy” for maintaining stability, generating challenges on when and how to stop it. Because about 35-40% of patients on chronic therapy do not exhibit objective neurological signs of worsening after stopping IVIg but express subjective symptoms of fatigue, pains, spasms, or a feeling of generalized weakness, a conditioning effect combined with fear that discontinuing chronic therapy may destabilize a multi-year stability status is likely. The dilemmas of continuing chronic therapy, the importance of adjusting dosing and scheduling or periodically stopping IVIg to objectively assess necessity, and concerns in accurately interpreting IVIg-dependency are discussed. Finally, the merit of subcutaneous IgG, the ineffectiveness of IVIg in IgG4-neurological autoimmunities, and genetic factors affecting IVIg dosing and efficacy are addressed.

Use of Levetiracetam in Epileptic Dogs with Chronic Kidney Disease: A Retrospective Study

In human medicine, doses of levetiracetam (LEV) are individualized for patients with epilepsy, depending on the status of the patient’s renal function. However, there are not reports on the individualized dosing of LEV for small animals. The aim of this study is to investigate whether a dose adjustment of LEV is needed in dogs with chronic kidney disease (CKD). Patient databases were searched, and 37 dogs with seizures or epilepsy were retrospectively included in this study. Based on pre-existing CKD, patients were divided into a CKD group (n = 20) and a non-CKD group (n = 17). We collected kidney panels before and after LEV treatment. Side-effects were monitored for 1 month after the start of LEV administration. In the CKD group, more dogs developed adverse effects (85%) than in the non-CKD group (52.94%). After LEV administration, an increase in blood urea nitrogen and/or serum creatinine was more often reported in the CKD group than it was in the non-CKD group. Our data indicate that in dogs with seizures or epilepsy with pre-existing CKD, an LEV dose-adjustment is needed. During LEV treatment, CKD patients should be monitored for side-effects and may require laboratory evaluation of renal function.

In silico evaluation of limited sampling strategies for individualized dosing of extended half-life factor IX concentrates in hemophilia B patients

Purpose Hemophilia B is a bleeding disorder, caused by a factor IX (FIX) deficiency. Recently, FIX concentrates with extended half-life (EHL) have become available. Prophylactic dosing of EHL-FIX concentrates can be optimized by assessment of individual pharmacokinetic (PK) parameters. To determine these parameters, limited sampling strategies (LSSs) may be applied. The study aims to establish adequate LSSs for estimating individual PK parameters of EHL-FIX concentrates using in silico evaluation. Methods Monte Carlo simulations were performed to obtain FIX activity versus time profiles using published population PK models for N9-GP (Refixia), rFIXFc (Alprolix), and rIX-FP (Idelvion). Fourteen LSSs, containing three or four samples taken within 8 days after administration, were formulated. Bayesian analysis was applied to obtain estimates for clearance (CL), half-life (t1/2), time to 1% (Time1%), and calculated weekly dose (Dose1%). Bias and precision of these estimates were assessed to determine which LSS was adequate. Results For all PK parameters of N9-GP, rFIXFc and rIX-FP bias was generally acceptable (range: −5% to 5%). For N9-GP, precision of all parameters for all LSSs was acceptable (< 25%). For rFIXFc, precision was acceptable for CL and Time1%, except for t1/2 (range: 27.1% to 44.7%) and Dose1% (range: 12% to 29.4%). For rIX-FP, all LSSs showed acceptable bias and precision, except for Dose1% using LSS with the last sample taken on day 3 (LSS 6 and 10). Conclusion Best performing LSSs were LSS with samples taken at days 1, 5, 7, and 8 (N9-GP and rFIXFc) and at days 1, 4, 6, and 8 (rIX-FP), respectively.

Real-life data of niraparib maintenance treatment in patients with recurrent platinum-sensitive ovarian cancer.

5560 Background: PARP (poly adenosine diphosphate [ADP]–ribose polymerase) inhibitors are the new standard for maintenance treatment in platinum sensitive recurrent ovarian cancer (PSROC), independent of germline (g-BRCA) or somatic BRCA mutation status. Real-life data after the introduction of new anti-neoplastic agents are needed to evaluate whether the benefit observed in phase III trials can be translated into clinical practice. The aim of this study was to provide real-life data on efficacy and safety of niraparib in non-gBRCA PSROC. Methods: This retrospective multi-center cohort study included patients with PSROC who were enrolled in a national individual patient access program in Norway. Efficacy and safety data were collected from the patients´ electronic medical records. The primary outcome was time from start of niraparib treatment to first subsequent treatment (TFST). Secondary endpoints included prevalence of dose interruption and -reduction, as well as adverse events. Results: The study included 106 patients with median age of 64 years (range 38-81). After median follow up of 15.3 months (95% CI 12.1-18.5), 71 patients (67%) had progressed, 64 (60%) had started a new line of treatment, and 25 (24%) had died. 25 (24%) patients were still receiving niraparib. Median duration of niraparib treatment was 7.6 months (0.4 to 27.3 months). Median TFST was 11.7 months (95% CI 9.2 -14.2). Patients with elevated CA125 after chemotherapy prior to start of niraparib had shorter progression-free survival (PFS) compared to patients with complete serological response (6.5 months (95% CI 5.7 – 7.3) vs 12 months (95% CI 6.2 – 17.9, (p < 0.001)). Grade 3-4 hematologic and non-hematologic events occurred in 25% and 17% of the patients, respectively. The most common grade 3/4 hematologic events were anemia (15%), thrombocytopenia (11%) and neutropenia (8%). Adverse events led to dose interruption in 38% and dose reduction in 44% of the patients. Patients with individualized dosing based on baseline weight and platelet counts had fewer dose reductions (p < 0.001) and -interruptions (p = 0.042) than patients whose dose was not adjusted to those baseline values. Conclusions: In a real-life setting, niraparib maintenance treatment in patients with non-gBRCA PSROC showed efficacy comparable with the published phase III data and an acceptable safety profile. Individualized dosing at start of treatment minimized adverse events. The prolonged PFS in patients with CA125 normalization after last chemotherapy, suggests that these patients in particular benefit from maintenance treatment but warrants confirmation in a larger sample.[Table: see text]

Factors affecting the pharmacokinetics of pyrazinamide and its metabolites in patients co-infected with HIV - implications for individualized dosing

Pyrazinamide is a first-line drug used in the treatment of tuberculosis. High exposure of pyrazinamide and its metabolites may result in hepatotoxicity whereas low exposure of pyrazinamide has been correlated to treatment failure by first-line antitubercular therapy. The aim of this study was to describe the pharmacokinetics and metabolism of pyrazinamide in patients co-infected with tuberculosis and HIV. We further aimed to identify demographic and clinical factors which affect the pharmacokinetics of pyrazinamide and its metabolites in order to suggest individualized dosing regimens. Plasma concentrations of pyrazinamide, pyrazinoic acid and 5-hydroxy pyrazinamide from 63 Rwandan patients co-infected with tuberculosis and HIV were determined by liquid chromatography tandem mass spectrometry followed by non-linear mixed effects modelling. Females had a close to 50% higher pyrazinamide bioavailability than males. The distribution volumes of pyrazinamide and both metabolites were lower in patients on concomitant efavirenz-based HIV therapy. Furthermore, there was a linear relationship between serum creatinine and oral clearance of pyrazinoic acid. Simulations indicated that increasing doses from 25 mg/kg to 35 mg/kg and 50 mg/kg in females and males, respectively would result in adequate exposure with regard to suggested thresholds and increase probability of target attainment to >0.9 for a minimal inhibitory concentration of 25 mg/L. Further, lowering the dose by 40% in patients with high serum creatinine would prevent accumulation of toxic metabolites. Individualized dosing is proposed to decrease variability in exposure to pyrazinamide and its metabolites. Reducing the variability in exposure may lower the risk of treatment failure and resistance development.