Retrospective Analysis Using Pharmacokinetic/Pharmacodynamic Modeling and Simulation Offers Improvements in Efficiency of the Design of Volunteer Infection Studies for Antimalarial Drug Development

Volunteer infection studies using the induced blood stage malaria (IBSM) model have been shown to facilitate antimalarial drug development. Such studies have traditionally been undertaken in single-dose cohorts, as many as necessary to obtain the dose-response relationship. To enhance ethical and logistic aspects of such studies, and to reduce the number of cohorts needed to establish the dose-response relationship, we undertook a retrospective in silico analysis of previously accrued data to improve study design. A pharmacokinetic (PK)/pharmacodynamic (PD) model was developed from initial fictive-cohort data for OZ439 (mixing the data of the three single-dose cohorts as: n = 2 on 100 mg, 2 on 200 mg, and 4 on 500 mg). A three-compartment model described OZ439 PKs. Net growth of parasites was modeled using a Gompertz function and drug-induced parasite death using a Hill function. Parameter estimates for the PK and PD models were comparable for the multidose single-cohort vs. the pooled analysis of all cohorts. Simulations based on the multidose single-cohort design described the complete data from the original IBSM study. The novel design allows for the ascertainment of the PK/PD relationship early in the study, providing a basis for rational dose selection for subsequent cohorts and studies.

Model-Informed Drug Development for Malaria Therapeutics

Malaria is a critical public health problem resulting in substantial morbidity and mortality, particularly in developing countries. Owing to the development of resistance toward current therapies, novel approaches to accelerate the development efforts of new malaria therapeutics are urgently needed. There have been significant advancements in the development of in vitro and in vivo experiments that generate data used to inform decisions about the potential merit of new compounds. A comprehensive disease-drug model capable of integrating discrete data from different preclinical and clinical components would be a valuable tool across all stages of drug development. This could have an enormous impact on the otherwise slow and resource-intensive process of traditional clinical drug development.

Genetic imprinting of autoantibody repertoires in systemic lupus erythematosus patients

Systemic lupus erythematosus (SLE) is an autoimmune disease distinguished by great heterogeneity in clinical manifestations and autoantibody expression. While only a handful of autoantibody specificities have proved useful for clinical diagnosis, to characterize complex lupus-associated autoantibody profiles more fully we have applied proteome microarray technology. Our multiplex microarrays included control ligands and 65-autoantigens, which represent diverse nuclear and cytoplasmic antigens recognized by disease-associated and natural autoantibodies. From longitudinal surveys of unrelated SLE patients, we found that autoantibody profile patterns can be patient-specific and highly stable overtime. From profiles of 38 SLE patients that included 14 sets of SLE twins, autoantibodies to the phospholipid neo-determinants, malondialdehyde (MDA) and phosphorylcholine (PC), which are exposed on apoptotic but not healthy cells, were among the most prevalent and highly expressed. We also found that immunoglobulin M (IgM) reactivity to MDA and PC ligands had significant direct correlations with DNA-containing antigens, while such a general relationship was not found with a panel of RNA-related antigens, or for IgG-autoantibodies. Significantly, hierarchical analysis revealed co-distribution/clustering of the IgM autoantibody repertoire patterns for six of 14 twin sets, and such patterns were even more common (10 of 14) for IgG autoantibody profiles. Our findings highlight the potentially distinct roles of IgM and IgG autoantibodies, as we postulate that the direct correlations for IgM autoantibodies to DNA antigens with apoptosis-related determinants may be due to co-expression arising from common pro-homeostatic protective roles. In contrast, the sharing of IgG autoantibody fingerprints by monozygotic twins suggests that lupus IgG autoantibodies can arise in predisposed individuals in genetically determined patterns.

Abdominal sensitivity in the first year of life: comparison of infants with and without prenatally diagnosed unilateral hydronephrosis

There are few studies on visceral pain in infants, despite its clinical importance. We have used the abdominal skin reflex (ASR) to measure changes in abdominal sensitivity in the presence of visceral pathology in infants. The reflex was elicited by applying calibrated von Frey hairs to each side of the abdomen and the mechanical threshold and the degree of reflex radiation as denoted by hip flexion were measured. The developmental progression of ASR properties during the first year of life was studied in a cross-sectional sample of healthy infants ranging from 30 to 95 weeks postconceptional age (PCA). These properties were compared to those in infants with unilateral hydronephrosis (UH) using a blinded protocol. Infants with UH were studied at their first outpatient appointment after birth, and postoperatively following surgery if this was indicated. The investigators were blinded to laterality and severity of hydronephrosis until data were analysed, or until surgery. A total of 30 patients with UH and 77 healthy infants were included in the study. In 21 (70%) patients, the side of hydronephrosis had a significantly lower ASR threshold than the contralateral side of the abdomen. There was a significant increase in reflex threshold and decrease in reflex radiation with increasing PCA in control infants. However, in UH infants, this relationship did not exist, even on the unaffected side of the abdomen.Our results show that infants with prenatally diagnosed UH demonstrate increased abdominal sensitivity compared with control infants. Using the ASR, we have provided the first evidence of referred visceral hypersensitivity in infants.

A comparison of rectal and intramuscular codeine phosphate in children following neurosurgery

Codeine is frequently used for postoperative analgesia in children. Intramuscular injections are not ideal and the rectal route may be preferable. We compared rectal and intramuscular codeine administered following neurosurgery. 20 children (over 3 months) undergoing elective neurosurgical procedures, were randomized to receive either rectal or intramuscular codeine phospate (1 mg.kg-1) at the end of the procedure. Serum levels of codeine and morphine were assayed at intervals following administration (0, 30, 60, 120, 240 min). Fentanyl was the intraoperative analgesic and postoperative rescue analgesia was paracetamol, diclofenac and intramuscular codeine. The Children's Hospital of Eastern Ontario Pain Scale was used to assess analgesia. Peak codeine levels in both groups were observed at 30 min and morphine levels were consistently low. The plasma codeine levels were significantly greater at 30 and 60 min following intramuscular injection, and were associated with slightly better analgesia scores, but did not reach statistical significance. However, the peak plasma level occurred at similar times in both groups. Codeine is absorbed as rapidly via the rectal route compared with the intramuscular route but the peak levels are lower.

Developmental regulation of the human zeta globin gene in transgenic mice

We have characterized the expression of the human zeta (zeta) gene, which encodes an embryonic alpha-like globin, in transgenic mice. We find that a 777 base pair fragment spanning erythroid specific hypersensitive site II (HSII) from the distal 5. region of the human beta globin gene cluster potentiates expression of the zeta globin gene. In the absence of the HSII fragment, no zeta expression is observed. Expression of the human zeta gene in mice parallels expression of a murine embryonic alpha-like globin gene (x). Thus, expression of the human zeta gene in mice requires linkage to an erythroid-specific enhancer sequence, but the presence of the enhancer does not affect the developmental regulation of the transgene. Our results indicate that the factors involved in switching from embryonic to adult alpha globin gene expression during development are evolutionarily conserved, and suggest that the transgenic mouse is an in vivo system in which the requirements for the developmental switch in alpha globin gene expression can be analyzed in detail.

Newborn screening by DNA analysis of dried blood spots

Amplification of DNA recovered from a dried blood spot was used to genotype individuals with sickle cell disease, sickle cell carriers, and controls. A single 200-microliters blood spot applied to a filter paper provides sufficient material for more than 20 genetic analyses. In addition, the stability of the DNA is such that adequate material for amplification can be isolated from dried blood spots up to a year following collection. The DNA analysis methods described in this study could be applied to large-scale screening of newborns for genetic disorders.