Model-based assessment of dosing strategies in children for monoclonal antibodies exhibiting target-mediated drug disposition

Genetic and epigenetic mechanisms influencing acute to chronic postsurgical pain transitions in pediatrics: Preclinical to clinical evidence

Background

Chronic postsurgical pain (CPSP) in children remains an important problem with no effective preventive or therapeutic strategies. Recently, genomic underpinnings explaining additional interindividual risk beyond psychological factors have been proposed.

Aims

We present a comprehensive review of current preclinical and clinical evidence for genetic and epigenetic mechanisms relevant to pediatric CPSP.

Methods

Narrative review.

Results

Animal models are relevant to translational research for unraveling genomic mechanisms. For example, Cacng2, p2rx7, and bdnf mutant mice show altered mechanical hypersensitivity to injury, and variants of the same genes have been associated with CPSP susceptibility in humans; similarly, differential DNA methylation (H1SP) and miRNAs (miR-96/7a) have shown translational implications. Animal studies also suggest that crosstalk between neurons and immune cells may be involved in nociceptive priming observed in neonates. In children, differential DNA methylation in regulatory genomic regions enriching GABAergic, dopaminergic, and immune pathways, as well as polygenic risk scores for enhanced prediction of CPSP, have been described. Genome-wide studies in pediatric CPSP are scarce, but pathways identified by adult gene association studies point to potential common mechanisms.

Conclusions

Bench-to-bedside genomics research in pediatric CPSP is currently limited. Reverse translational approaches, use of other -omics, and inclusion of pediatric/CPSP endophenotypes in large-scale biobanks may be potential solutions. Time of developmental vulnerability and longitudinal genomic changes after surgery warrant further investigation. Emergence of promising precision pain management strategies based on gene editing and epigenetic programing emphasize need for further research in pediatric CPSP-related genomics.

Drug Treatment of Low Bone Mass and Other Bone Conditions in Pediatric Patients

Osteoporosis may affect young individuals, albeit infrequently. In childhood, bone mass increases, reaching its peak between the second and third decades; then, after a period of stability, it gradually declines. Several conditions, including genetic disorders, chronic diseases, and some medications, can have an impact on bone homeostasis. Diagnosis in young patients is based on the criteria defined by the International Society for Clinical Densitometry (ISCD), published in 2013. High risk factors should be identified and monitored. Often simple interventions aimed to eliminate the underlying cause, to minimize the negative bone effects linked to drugs, or to increase calcium and vitamin D intake can protect bone mass. However, in selected cases, pharmacological treatment should be considered. Bisphosphonates remain the main therapeutic agent for children with significant skeletal fragility and are also useful in a large number of other bone conditions. Denosumab, an anti-RANKL antibody, could become a potential alternative treatment. Clinical trials to evaluate the long-term effects and safety of denosumab in children are ongoing.

Allometric scaling of therapeutic monoclonal antibodies in preclinical and clinical settings

Constant technological advancement enabled the production of therapeutic monoclonal antibodies (mAbs) and will continue to contribute to their rapid expansion. Compared to small-molecule drugs, mAbs have favorable characteristics, but also more complex pharmacokinetics (PK), e.g., target-mediated nonlinear elimination and recycling by neonatal Fc-receptor. This review briefly discusses mAb biology, similarities and differences in PK processes across species and within human, and provides a detailed overview of allometric scaling approaches for translating mAb PK from preclinical species to human and extrapolating from adults to children. The approaches described here will remain vital in mAb drug development, although more data are needed, for example, from very young patients and mAbs with nonlinear PK, to allow for more confident conclusions and contribute to further growth of this field. Improving mAb PK predictions will facilitate better planning of (pediatric) clinical studies and enable progression toward the ultimate goal of expediting drug development.

Hypercalcemia and hypercalciuria during denosumab treatment in children with osteogenesis imperfecta type VI

Children with osteogenesis imperfecta (OI) type VI often have high fracture rates despite the current standard treatment with bisphosphonates. Subcutaneous injections of denosumab have been proposed as an alternative treatment approach, but safety data on denosumab in children are limited. Here we describe fluctuations in bone and mineral metabolism during denosumab treatment in four children with OI type VI who started denosumab (basic protocol: 1 mg per kg body mass every 3 months) between 1.9 and 9.0 years of age, after having received intravenous bisphosphonates previously. All four children developed hypercalciuria during active denosumab therapy. In two children aged 3.9 and 4.6 years, episodes of hypercalcemia were observed between 7 and 12 weeks after the preceding denosumab injection. During times when the interval between denosumab injections was increased to 6 months for clinical reasons, lumbar spine bone mineral density z-scores decreased rapidly. It appears that the duration of action of denosumab is short and variable in children with OI type VI. These observations call into question the concept that denosumab can be used as a stand-alone alternative to bisphosphonates to treat children with OI.

Denosumab: an Emerging Therapy in Pediatric Bone Disorders

PURPOSE OF REVIEW

Denosumab is an inhibitor of receptor activator of nuclear factor kappa-B ligand (RANKL), and has emerged as an important novel therapy for skeletal disorders. This article examines the use of denosumab in children.

RECENT FINDINGS

Considerable safety and efficacy data exists for denosumab treatment of adults with osteoporosis, bone metastases, and giant cell tumors. Pediatric data is limited; however, evidence suggests denosumab may be beneficial in decreasing bone turnover, increasing bone density, and preventing growth of certain skeletal neoplasms in children. Denosumab's effect on bone turnover is rapidly reversible after drug discontinuation, representing a key difference from bisphosphonates. Rebound increased bone turnover has led to severe hypercalcemia in several pediatric patients. Denosumab is a promising therapy for pediatric skeletal disorders. At present, safety concerns related to rebounding bone turnover and mineral homeostasis impact use of denosumab in children. Research is needed to determine if and how these effects can be mitigated.

Variable Eculizumab Clearance Requires Pharmacodynamic Monitoring to Optimize Therapy for Thrombotic Microangiopathy after Hematopoietic Stem Cell Transplantation

Thrombotic microangiopathy (TMA) after hematopoietic stem cell transplantation (HSCT) associated with terminal complement activation, as measured by elevated plasma terminal complement (sC5b-9) concentrations, has a very high mortality. The complement inhibitor eculizumab may be a therapeutic option for HSCT-associated TMA. We examined the pharmacokinetics and pharmacodynamics (PK/PD) of eculizumab in children and young adult HSCT recipients with TMA and activated complement to determine drug dosing requirements for future efficacy trials. We analyzed prospectively collected laboratory samples and clinical data from 18 HSCT recipients with high-risk TMA presenting with complement activation who were treated with eculizumab. We measured eculizumab serum concentrations, total hemolytic complement activity, and plasma sC5b-9 concentrations. Population PK/PD analyses correlated eculizumab concentrations with complement blockade and clinical response and determined interindividual differences in PK parameters. We also compared transplant survival in patients treated with eculizumab (n = 18) with patients with the same high-risk TMA features who did not receive any targeted therapy during a separate prospective observational study (n = 11). In the PK analysis, we found significant interpatient variability in eculizumab clearance, ranging from 16 to 237 mL/hr/70 kg in the induction phase. The degree of complement activation measured by sC5b-9 concentrations at the start of therapy, in addition to actual body weight, was a significant determinant of eculizumab clearance and disease response. Sixty-one percent of treated patients had complete resolution of TMA and were able to safely discontinue eculizumab without disease recurrence. Overall survival was significantly higher in treated subjects compared with untreated patients (56% versus 9%, P = .003). Complement blocking therapy is associated with improved survival in HSCT patients with high-risk TMA who historically have dismal outcomes, but eculizumab pharmacokinetics in HSCT recipients differ significantly from reports in other diseases like atypical hemolytic uremic syndrome and paroxysmal nocturnal hemoglobinuria. Our eculizumab dosing algorithm, including pr-treatment plasma sC5b-9 concentrations, patient's actual body weight, and the first eculizumab dose (mg), accurately determined eculizumab concentration-time profiles for HSCT recipients with high-risk TMA. This algorithm may guide eculizumab treatment and ensure that future efficacy studies use the most clinically appropriate and cost-efficient dosing schedules.