The Development of Ofatumumab, a Fully Human Anti-CD20 Monoclonal Antibody for Practical Use in Relapsing Multiple Sclerosis Treatment

The importance of B cells in multiple sclerosis (MS) has been demonstrated through the advent of B-cell-depleting anti-CD20 antibody therapies. Ofatumumab is the first fully human anti-CD20 monoclonal antibody (mAb) developed and tested for subcutaneous (SC) self-administration at monthly doses of 20 mg, and has been approved in the US, UK, EU, and other regions and countries worldwide for the treatment of relapsing MS. The development goal of ofatumumab was to obtain a highly efficacious anti-CD20 therapy, with a safety and tolerability profile that allows for self-administration by MS patients at home and a positive benefit-risk balance for use in the broad relapsing MS population. This development goal was enabled by the unique binding site, higher affinity to B cells, and higher potency of ofatumumab compared to previous anti-CD20 mAbs; these properties of ofatumumab facilitate rapid B-cell depletion and maintenance with a low dose at a low injection volume (20 mg/0.4 ml). The high potency in turn enables the selective targeting of B cells that reside in the lymphatic system via subcutaneous (SC) administration. Through a comprehensive dose-finding program in two phase 2 studies (one intravenous and one SC) and model simulations, it was found that safety and tolerability can be further improved, and the risk of systemic injection-related reactions (IRRs) minimized, by avoiding doses ≥ 30 mg, and by reaching initial and rapid B-cell depletion via stepwise weekly administration of ofatumumab at Weeks 0, 1, and 2 (instead of a single high dose). Once near-complete B-cell depletion is reached, it can be maintained by monthly doses of 20 mg/0.4 ml. Indeed, in phase 3 trials (ASCLEPIOS I/II), rapid and sustained near-complete B-cell depletion (largely independent of body weight, race and other factors) was observed with this dosing regimen, which resulted in superior efficacy of ofatumumab versus teriflunomide on relapse rates, disability worsening, neuronal injury (serum neurofilament light chain), and imaging outcomes. Likely due to its fully human nature, ofatumumab has a low immunogenic risk profile-only 2 of 914 patients receiving ofatumumab in ASCLEPIOS I/II developed anti-drug antibodies-and this may also underlie the infrequent IRRs (20% with ofatumumab vs. 15% with the placebo injection in the teriflunomide arm) that were mostly (99.8%) mild to moderate in severity. The overall rates of infections and serious infections in patients treated with ofatumumab were similar to those in patients treated with teriflunomide (51.6% vs. 52.7% and 2.5% vs. 1.8%, respectively). The benefit-risk profile of ofatumumab was favorable compared to teriflunomide in the broad RMS population, and also in the predefined subgroups of both recently diagnosed and/or treatment-naïve patients, as well as previously disease-modifying therapy-treated patients. Interim data from the ongoing extension study (ALITHIOS) have shown that long-term treatment with ofatumumab up to 4 years is well-tolerated in RMS patients, with no new safety risks identified. In parallel to the phase 3 trials in which SC administration was carried out with a pre-filled syringe, an autoinjector pen for more convenient self-administration of the ofatumumab 20 mg dose was developed and is available for use in clinical practice.

Learning induces unique transcriptional landscapes in the auditory cortex

Learning can induce neurophysiological plasticity in the auditory cortex at multiple timescales. Lasting changes to auditory cortical function that persist over days, weeks, or even a lifetime, require learning to induce de novo gene expression. Indeed, transcription is the molecular determinant for long-term memories to form with a lasting impact on sound-related behavior. However, auditory cortical genes that support auditory learning, memory, and acquired sound-specific behavior are largely unknown. Using an animal model of adult, male Sprague-Dawley rats, this report is the first to identify genome-wide changes in learning-induced gene expression within the auditory cortex that may underlie long-lasting discriminative memory formation of acoustic frequency cues. Auditory cortical samples were collected from animals in the initial learning phase of a two-tone discrimination sound-reward task known to induce sound-specific neurophysiological and behavioral effects. Bioinformatic analyses on gene enrichment profiles from bulk RNA sequencing identified cholinergic synapse (KEGG rno04725), extra-cellular matrix receptor interaction (KEGG rno04512), and neuroactive receptor interaction (KEGG rno04080) among the top biological pathways are likely to be important for auditory discrimination learning. The findings characterize candidate effectors underlying the early stages of changes in cortical and behavioral function to ultimately support the formation of long-term discriminative auditory memory in the adult brain. The molecules and mechanisms identified are potential therapeutic targets to facilitate experiences that induce long-lasting changes to sound-specific auditory function in adulthood and prime for future gene-targeted investigations.

Learning induces unique transcriptional landscapes in the auditory cortex

Learning can induce neurophysiological plasticity in the auditory cortex at multiple timescales. Lasting changes to auditory cortical function that persist over days, weeks, or even a lifetime, require learning to induce de novo gene expression. Indeed, transcription is the molecular determinant for long-term memories to form with a lasting impact on sound-related behavior. However, auditory cortical genes that support auditory learning, memory, and acquired sound-specific behavior are largely unknown. This report is the first to identify in young adult male rats (Sprague-Dawley) genome-wide changes in learning-induced gene expression within the auditory cortex that may underlie the formation of long-lasting discriminative memory for acoustic frequency cues. Auditory cortical samples were collected from animals in the initial learning phase of a two-tone discrimination sound-reward task known to induce sound-specific neurophysiological and behavioral effects (e.g., Shang et al., 2019). Bioinformatic analyses on gene enrichment profiles from bulk RNA sequencing identified cholinergic synapse (KEGG 04725), extra-cellular matrix receptor interaction (KEGG 04512) , and neuroactive ligand-receptor interaction (KEGG 04080) as top biological pathways for auditory discrimination learning. The findings characterize key candidate effectors underlying changes in cortical function that support the initial formation of long-term discriminative auditory memory in the adult brain. The molecules and mechanisms identified are potential therapeutic targets to facilitate lasting changes to sound-specific auditory function in adulthood and prime for future gene-targeted investigations.

A scalable approach for continuous time Markov models with covariates

Existing methods for fitting continuous time Markov models (CTMM) in the presence of covariates suffer from scalability issues due to high computational cost of matrix exponentials calculated for each observation. In this article, we propose an optimization technique for CTMM which uses a stochastic gradient descent algorithm combined with differentiation of the matrix exponential using a Padé approximation. This approach makes fitting large scale data feasible. We present two methods for computing standard errors, one novel approach using the Padé expansion and the other using power series expansion of the matrix exponential. Through simulations, we find improved performance relative to existing CTMM methods, and we demonstrate the method on the large-scale multiple sclerosis NO.MS data set.

The safe use of metformin in heart failure patients both with and without T2DM: a cross-sectional and longitudinal study

AIMS

This study investigated the safe use of metformin in patients with (1) type 2 diabetes mellitus (T2DM) and heart failure on metformin, and (2) heart failure without T2DM and metformin naïve.

METHODS

Two prospective studies on heart failure patients were undertaken. The first was a cross-sectional study with two patient cohorts, one with T2DM on metformin (n=44) and one without T2DM metformin naive (n=47). The second was a 12-week interventional study of patients without T2DM (n=27) where metformin (500 mg immediate release, twice daily) was prescribed. Plasma metformin and lactate concentrations were monitored. Individual pharmacokinetics were compared between cohorts. Univariable and multivariable analysis analysed the effects of variables on plasma lactate concentrations.

RESULTS

Plasma metformin and lactate concentrations mostly (99.9%) remained below safety thresholds (5 mg/L and 5 mmol/L, respectively). Metformin concentration had no significant relationship with lactic acidosis safety markers. In the interventional study, New York Heart Association (NYHA) II (p<0.03) and III (p<0.001) grading was associated with higher plasma lactate concentrations, whereas male sex was associated with 47% higher plasma lactate concentrations (p<0.05). The pharmacokinetics of heart failure patients with and without T2DM were similar.

CONCLUSIONS

We observed no unsafe plasma lactate concentrations in patients with heart failure treated with metformin. Metformin exposure did not influence plasma lactate concentrations; however, NYHA class and sex did. The pharmacokinetics of metformin in heart failure patients are similar irrespective of T2DM. These findings may support the safe use of metformin in heart failure patients with and without T2DM.

117 Sustained and rapid B-cell depletion with ofatumumab: population pharma- cokinetic B-cell modeling in relapsing MS patients

Objectives

To characterize the pharmacokinetic (PK) relationship of ofatumumab for B-cell counts in RMS patients, assess the PK and B-cell dynamics given the Phase 3 dose regimen through PK-B-cell simulations and explore the effect of covariates on PK and B-cells.

Methods

The PK-B-cell model was developed using data from Phase 2 and 3 trials. Simultaneous fitting was performed to assess the interaction between PK and B-cells. Effect of body weight, age, administra- tion route, s.c. injection device, and baseline B-cell count on PK and B-cell parameters were evaluated.

Results

In total, 9,168 plasma concentrations from 1,440 patients were included in PK analysis and 17,158 B-cell counts from 1,486 patients in B-cell analysis. Simulations demonstrated a rapid, median B-cell depletion to <10 cells/µL in 8.75 days; no signs of B-cell repletion occurred between doses, and >94% of patients had <10 cells/µL at B-cell steady state and pre-dose. Regardless of weight, all patients achieved low B-cell counts, similar to results observed in Phase 3 trials. Baseline age, B-cell counts and injection device had negligible effect on PK parameters.

Conclusion

The PK-B-cell model showed early, rapid, and sustained B-cell depletion with ofatumumab, confirming the rationale for the chosen Phase 3 dosing regimen.

Funding statement.This study was funded by Novartis Pharma AG, Basel, Switzerland. teresa.sawtell@novartis.com

Population Pharmacokinetic-B Cell Modeling for Ofatumumab in Patients with Relapsing Multiple Sclerosis

BACKGROUND

Ofatumumab, a fully human anti-CD20 monoclonal antibody indicated for the treatment of relapsing forms of multiple sclerosis (RMS), binds to a unique conformational epitope, thereby depleting B cells very efficiently and allowing subcutaneous administration at lower doses.

OBJECTIVES

The aims were to characterize the relationship between ofatumumab concentration and B cell levels, including the effect of covariates such as body weight, age, or baseline B cell count, and use simulations to confirm the chosen therapeutic dose.

METHODS

Graphical and regression analyses previously performed based on data from a dose-range finding study provided the B cell depletion target used in the present work. All available adult phase 2/3 data for ofatumumab in RMS patients were pooled to develop a population pharmacokinetics (PK)-B cell count model, using nonlinear mixed-effects modeling. The population PK-B cell model was used to simulate B cell depletion and repletion times and the effect of covariates on PK and B cell metrics, as well as the dose response across a range of subcutaneous ofatumumab monthly doses.

RESULTS

The final PK-B cell model was developed using data from 1486 patients. The predetermined B cell target was best achieved and sustained with the 20-mg dose regimen, with median B cell count reaching 8 cells/µL in 11 days and negligible repletion between doses. Only weight had a significant effect on PK, which did not translate into any clinically relevant effect on B cell levels.

CONCLUSION

The PK-B cell modeling confirms the dose chosen for the licensed ofatumumab regimen and demonstrates no requirement for dose adjustment based on adult patient characteristics.

A rare mimic of basal cell carcinoma

Lymphoepithelioma-like carcinoma of the skin is an extremely rare tumour whose aetiology is yet to be established. An 83-year-old female presented with a rapidly growing plaque on the chest wall diagnosed as lymphoepithelioma-like carcinoma histologically.

SAT0280 IMPACT OF PLACENTAL FACTORS ON PREGNANCY AND FETAL OUTCOME IN SYSTEMIC SCLEROSIS

Background:

Systemic Sclerosis (SSc) is one of the rheumatic diseases burdened with obstetrical complications. An Italian multicenter study showed that women with SSc have a higher-than-normal risk of intrauterine growth restriction, preterm delivery, very-low birth weight babies and pregnancy should be discouraged in patients with severe organ damage. However, with a multidisciplinary management, patients with SSc can have successful outcomes1. Little is known about the pathogenesis of obstetrical complications, as studies on placenta are case reports or description of a few cases2,3.

Objectives:

The aim of this study was to analyze the placental alterations with a focus on the role of inflammation in the pathogenesis of obstetrical complications in SSc, including the study of the atypical chemokine receptor 2 (ACKR2), involved in immune modulation and known to be highly expressed in circulating leucocytes in SSc patients4-6.

Methods:

Eight SSc pregnant patients were compared with 16 patients with other rheumatic diseases (ORD) and 16 healthy controls (HC), matched for gestational age. Clinical data were collected. Placentas biopsies were obtained for histopathological analysis and immunohistochemistry for CD3, CD20, CD11c, CD68 and ACKR2. Frozen placenta samples from 4 SSc, 8 ORD and 8 HC were analyzed by qPCR for ACKR2 gene expression and proteins were extracted for multiplex assay for cytokines, chemokines and growth factors involved in angiogenesis and inflammation. Statistical analysis was performed with parametric or non-parametric tests depending on samples distribution.

Results:

The number of placental CD3 (p<0.05), CD68 (p<0.001) and CD11c+ (p<0.001) cells was significantly higher considering the group of patients affected by rheumatic diseases (SSc+ORD) compared to HC. The SSc group alone did not show significance due to the lower sample size. No differences were observed between groups in terms of vascular alterations or fibrosis. The percentage of stained area for ACKR2 and the ACKR2 transcripts levels were comparable between groups. Hepatocyte growth factor (HGF), involved in angiogenesis, was significantly increased in the group of rheumatic diseases patients (SSc+ORD) compared to HC (p<0.05), while the chemokine CCL5 was significantly higher in SSc patients compared to patients affected by ORD (p<0.05) and to HC (p<0.01). CCL5 levels directly correlated with the number of all inflammatory cells considered and higher levels were associated to histological villitis (p<0.01).

Conclusion:

The higher number of placental inflammatory cells and the alterations in the levels of HGF and especially CCL5 could play a role in the pathogenesis of the obstetrical complications in SSc. ACKR2 does not seem involved in the obstetrical complications of SSc.

References:

[1]Taraborelli M, et al. Arthritis Rheum. 2012

[2]Ibba-Manneschi L, et al. Ann Rheum Dis. 2010

[3]Doss BJ, et al. Hum Pathol. 1998

[4]Graham GJ. Eur J Immunol. 2009

[5]Martinez de la Torre Y, et al. Proc Natl Acad Sci U S A. 2007

[6]Codullo V, et al. Ann Rheum Dis. 2011

Disclosure of Interests:

None declared

SAT0351 CHEMOKINE PATHWAYS ARE ENRICHED IN PSORIATIC ARTHRITIS (PSA) SKIN LESIONS WITH INCREASED EXPRESSION OF ATYPICAL CHEMOKINE RECEPTOR 2 (ACKR2)

Background:

Skin in people with psoriasis has been comprehensively studied; uninvolved skin has abnormal gene expression. Less is known specifically about skin in PsA, the assumption being that it is identical to psoriasis. Chemokines and ACKR2 are among the upregulated genes in uninvolved psoriasis compared to healthy skin[1]. ACKR2 is a scavenging receptor of inflammatory CC chemokines and has been proposed as a regulator of cutaneous inflammation in psoriasis. It has not been studied in PsA.

Objectives:

To compare the transcriptome of PsA lesional, PsA uninvolved and healthy control skin and evaluate ACKR2 expression in PsA.

Methods:

Biopsies were taken from healthy control (HC) skin and paired lesional and uninvolved skin from patients with PsA. Libraries for bulk RNA sequencing were prepared from polyA selected RNA and sequenced on NovaSeq 6000. Sequencing data were analysed using Searchlight2. ACKR2 mRNA expression was validated by qPCR. RNAscope was used to localise ACKR2 expressing cells and sections were co-stained with podaplanin or stained in serial sections with CD45. Chemokine protein expression in skin was evaluated using Luminex technology.

Results:

Nine HC and 9 paired skin samples from patients with PsA were sequenced. The PsA skin lesions (PsA L) formed a distinct population in the transcriptomic principal component analysis (PCA) plot while HC and PsA uninvolved skin (PsA U) were overlapping. Only 15 genes were differentially expressed between HC and PsA U and none coded for chemokines. There were however significantly upregulated chemokines and receptors in PsA L. Unexpectely, ACKR2 was the 2ndmost upregulated chemokine receptor in PsA L with unchanged expression in PsA U compared with HC (PsA L vs HC log2fold 3.38, p.adj=9.51E-41; PsA L vs PsA U log2fold 3.58, p.adj=3.24E-45; PsA U vs HC log2fold -0.2, p.adj=0.732).

The upregulation of ACKR2 in PsA L and unchanged expression in PsA U was confirmed by qPCR. RNAscope demonstrated strong expression of ACKR2 in the suprabasal layer of the epidermis in PsA L. In HC and PsA U, only occasional ACKR2 positive cells were seen in the epidermis. ACKR2 was expressed in lymphatic vessel walls but was not observed in CD45+ leukocytes.

Provisional skin chemokine protein expression data showed poor correlation between mRNA levels and protein expression for the ACKR2 ligands CCL2, CCL3, CCL7, CCL8, CCL11, CCL13 and CCL22 in HC and PsA U, with negative correlation between ACKR2 mRNA expression and CCL2, CCL8 and CCL11 protein expression. In PsA L, chemokine mRNA correlated with protein expression, but protein expression of chemokine ligands did not correlate with ACKR2 expression.

Conclusion:

This data set shows expected upregulation of chemokines and their receptors in PsA L but relatively unchanged gene expression in PsA U, which contrasts to previous studies in psoriasis. Notably, this study demonstrates a strong upregulation of ACKR2 in keratinocytes in PsA L, with unchanged expression in PsA U. The RNA expression and preliminary protein data suggest that ACKR2 has little effect on the levels of its ligands in PsA skin lesions. However, this study may have missed local effects of ACKR2 in the epidermis.

References:

[1]Singh, M.D., et al.,Elevated expression of the chemokine-scavenging receptor D6 is associated with impaired lesion development in psoriasis.Am J Pathol, 2012.181(4): p. 1158-64.

Acknowledgments:

Funded by the Chief Scientist Office and a private donation to the University of Glasgow. Dr Sabarinadh Chilaka helped to prepare libraries for RNA sequencing.

Disclosure of Interests:

Hanna Johnsson: None declared, John Cole: None declared, Gillian Wilson: None declared, Marieke Pingen: None declared, Fiona McMonagle: None declared, Susan Holmes: None declared, Iain McInnes Grant/research support from: Bristol-Myers Squibb, Celgene, Eli Lilly and Company, Janssen, and UCB, Consultant of: AbbVie, Bristol-Myers Squibb, Celgene, Eli Lilly and Company, Gilead, Janssen, Novartis, Pfizer, and UCB, Stefan Siebert Grant/research support from: BMS, Boehringer Ingelheim, Celgene, GlaxoSmithKline, Janssen, Novartis, Pfizer, UCB, Consultant of: AbbVie, Boehringer Ingelheim, Janssen, Novartis, Pfizer, UCB, Speakers bureau: AbbVie, Celgene, Janssen, Novartis, Gerard Graham: None declared

Abstract P3-07-09: ERRβ copy number and expression in triple negative breast cancer

Introduction: Triple negative breast cancer (TNBC) is a highly aggressive form of breast cancer prevalent in African-American (AA) women defined as estrogen receptor- (ER), progesterone receptor- (PR), and human epidermal growth factor receptor 2- (HER2) negative. Because ER- and HER2-targeted therapies are ineffective in TNBC, systemic chemotherapy is the standard of care and there is a tremendous need for new effective therapies with less toxicity. Steroid hormone receptors are highly druggable targets, and orphan nuclear receptors, members of the nuclear receptor superfamily, are emerging as targets for cancer therapy. In fact, we have previously shown that treatment of TNBC cells with a small molecule agonist ligand (DY131) for estrogen related receptor beta (ERRβ), has growth inhibitory and anti-mitotic activity. We have also shown that increased mRNA expression of ERRβ, correlates with better recurrence- and distant metastasis-free survival in TNBC/basal-like breast cancer. The goal of our current work is to comprehensively characterize ERRβ copy number and mRNA status in TNBC and determine its association with patients' prognosis.

Methods: ESRRB copy number was determined in 106 primary breast tumors (TNBC n=56, nonTNBC n=50) by array-CGH, using the Agilent SurePrint G3 Human CGH platform. ESRRB mRNA data and its association with overall survival was determined in systemically untreated patients from METABRIC using Illumina gene expression array data (probe ID ILMN_1707398).

Results: Copy number alterations (CNAs). Copy number losses at the ESRRB locus (14q24.3) were observed in 10/56 (17.8%) of TNBC vs. 10/50 (20%) of nonTNBC, while copy number gains were detected in 43/56 (76.8%) of TNBC vs. 29/50 (58%) of nonTNBC (c2 *p=0.036). Interestingly, in both TNBC and non-TNBC, ESRRB loss was seen with markedly higher frequency in AA patients when compared to Caucasian (CA) patients (c2 *p=0.012 for TNBC, p=0.052 for non-TNBC). mRNA expression. Among patients not treated with systemic chemotherapy in the METABRIC dataset, low ESRRB mRNA was significantly associated with shorter overall survival in TNBC, but not ER+ or HER2+ patients (TNBC hazard ratio 0.24, 95% confidence interval 0.07-0.85, *p=0.016). Low ESRRB also correlated with reduced overall survival in TP53 mutant (but not wild type) tumors (hazard ratio 0.28, 95% confidence interval 0.1-0.82, *p=0.013).

Conclusions: ESRRB presents significantly high levels of copy number losses in TNBC when compared to non-TNBC tumors. In breast tumors from AA women, both the TNBC and non-TNBC subtypes are significantly more likely to have reduced ESRRB copy number vs. CA women. Low ESRRB mRNA expression predicts for poor overall survival in TNBC and TP53 mutant tumors. These data advocate that ERRβ expression has prognostic value in breast cancer, particularly TNBC. Future goals include immunohistochemistry staining, and analysis, of a tissue microarray consisting of 150 primary breast tumors (50 TNBC, 50 ER+, 50 HER2+); as well as ERRβ overexpression and knock-down studies in TNBC cell lines to define the role it plays in TNBC.

Citation Format: Fernandez AI, Graham G, Győrffy B, Cavalli L, Mahajan A, Riggins RB. ERRβ copy number and expression in triple negative breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-07-09.

Does partial muscle reinnervation preserve future re-innervation potential?

INTRODUCTION

Late revision nerve surgery for incomplete motor recovery due to partial reinnervation would improve muscle function if all muscle fibers were protected from developing denervation atrophy.

METHODS

Sixty immature Sprague-Dawley rats underwent the following tibial nerve manipulations (n = 15/group): group A, partial denervation (two thirds of nerve resected and the remaining one third crushed), revision repair at 8 months; group B, partial denervation; group C, complete denervation, immediate reconstruction; group D, complete denervation, reconstruction at 8 months; and group E, control. Final testing at 11 months included muscle force, weight, and histology.

RESULTS

Muscle weight was significantly (P < 0.05) different among all groups (highest to lowest: E > B > C > A > D), and force was significantly lower in groups A and D compared with E. Muscle fiber cross-sectional area was statistically smaller in group A than in groups B, C, or E.

DISCUSSION

Partial reinnervation still allowed substantial muscle recovery, but it did not preserve the non-innervated muscle fibers. Muscle Nerve 56: 1143-1148, 2017.

Use of an Artificial Sweetener to Identify Sources of Groundwater Nitrate Contamination

The artificial sweetener acesulfame (ACE) is a potentially useful tracer of waste water contamination in groundwater. In this study, ACE concentrations were measured in waste water and impacted groundwater at 12 septic system sites in Ontario, Canada. All samples of septic tank effluent (n = 37) had ACE >6 µg/L, all samples of groundwater from the proximal plume zones (n = 93) had ACE >1 µg/L and, almost all samples from the distal plume zones had ACE >2 µg/L. Mean mass ratios of total inorganic nitrogen/ACE at the 12 sites ranged from 680 to 3500 for the tank and proximal plume samples. At five sites, decreasing ratio values in the distal zones indicated nitrogen attenuation. These ratios were applied to three aquifers in Canada that are nitrate-stressed and an urban stream where septic systems are present nearby to estimate the amount of waste water nitrate contamination. At the three aquifer locations that are agricultural, low ACE values (<0.02-0.15 µg/L) indicated that waste water contributed <15% of the nitrate in most samples. In groundwater discharging to the urban stream, much higher ACE values (0.2-11 µg/L) indicated that waste water was the likely source of >50% of the nitrate in most samples. This study confirms that ACE is a powerful tracer and demonstrates its use as a diagnostic tool for establishing whether waste water is a significant contributor to groundwater contamination or not.

Monozygotic twins discordant for trisomy 13

Monozygotic twins with discordant karyotypes are rare. We report a case of monozygotic twins discordant for trisomy 13 by amniocyte karyotypes. Ultrasound revealed multiple congenital anomalies in Twin A (47,XY,+13), none in Twin B (46,XY), and monochorionic-diamniotic placentation. Zygosity testing performed both prenatally and after birth supported monozygosity. Twin A died in the neontal period. Twin B survived and had normal physical examination, but peripheral blood karyotype revealed 20% mosaicism for trisomy 13. Monochorionic-diamniontic placentation with vascular anastomoses was confirmed by pathological examination. In this paper, we discuss the various mechanisms by which monozygotic twins may have discordant karyotypes. The surviving twin, structurally and developmentally normal at 6 months of age, will be monitored for potential complications of uniparental disomy of chromosome 13 and trisomy 13 mosaicism.

Specific attentional impairments and complex visual hallucinations in eye disease

OBJECTIVE

To test the prediction by the Perception and Attention Deficit (PAD) model of complex visual hallucinations that cognitive impairment, specifically in visual attention, is a key risk factor for complex hallucinations in eye disease.

METHODS

Two studies of elderly patients with acquired eye disease investigated the relationship between complex visual hallucinations (CVH) and impairments in general cognition and verbal attention (Study 1) and between CVH, selective visual attention and visual object perception (Study 2). The North East Visual Hallucinations Inventory was used to classify CVH.

RESULTS

In Study 1, there was no relationship between CVH (n=10/39) and performance on cognitive screening or verbal attention tasks. In Study 2, participants with CVH (n=11/31) showed poorer performance on a modified Stroop task (p<0.05), a novel imagery-based attentional task (p<0.05) and picture (p<0.05) but not silhouette naming (p=0.13) tasks. Performance on these tasks correctly classified 83% of the participants as hallucinators or non-hallucinators.

CONCLUSIONS

The results suggest that, consistent with the PAD model, complex visual hallucinations in people with acquired eye disease are associated with visual attention impairment.

Population pharmacokinetics and optimal design of paediatric studies for famciclovir

AIMS

To develop a population pharmacokinetic model for penciclovir (famciclovir is a prodrug of penciclovir) in adults and children and suggest an appropriate dose for children. Furthermore, to develop a limited sampling design based on sampling windows for three different paediatric age groups (1-2, 2-5 and 5-12 years) using an adequate number of subjects for future pharmacokinetic studies.

METHODS

Penciclovir plasma data from six different adult and paediatric studies were supplied by Novartis. Population pharmacokinetic modelling was undertaken in NONMEM version VI. Simulations in MATLAB were used to select an oral paediatric dose that gives similar exposure to 500 mg in adults. Optimal sampling times and sampling windows were obtained in MATLAB and simulations in NONMEM were used to select adequate sample sizes for three paediatric age groups.

RESULTS

A two-compartment, first-order absorption model with an absorption lag time, allometric weight models on V(1), V(2) and Q, and an allometric weight model, age and creatinine clearance as covariates on CL adequately describe the pharmacokinetics of penciclovir in adults and children. Estimated CL (l h(-1) 70 kg(-1)) and V(ss) (l.70 kg(-1)) were 31.2 and 83.1, respectively. An oral dose of 10 mg kg(-1) body weight in children was predicted to give similar exposure as 500 mg in adults. A single sampling windows design (0.25-0.4, 0.5-1, 1.25-1.75, 2.75-3.5 and 7.25-8 h) for five samples per subject and 10 subjects in each of the paediatric age groups is recommended for future studies.

CONCLUSIONS

A population pharmacokinetic model of penciclovir in adults and children has been developed. A prospective study design, including dose adjustment, cohort size and blood sampling design has been recommended.

Effect of prefeeding on foraging patterns of brushtail possums (Trichosurus vulpecula) about prefeed transects

Context. Brushtail possums (Trichosurus vulpecula) are a major pest of native biodiversity and agricultural production in New Zealand. To maximise the effectiveness of control operations, prefeeding (free-feeding) of non-toxic bait before poison is often used, but the mechanisms by which it does so, remain unclear. One possibility is that prefeeding changes foraging patterns and space use in ways that increase the likelihood of possums finding and eating a lethal dose of poison bait. Aim. To determine whether prefeeding along transects increases possum activity on the transect, and if so, how long the effect lasts. Methods. We monitored the time that radio-collared possums spent within a few metres of 350 m of aerial wire laid along a transect. Key results. Initially, possums spent only 2.6 min per night in the vicinity of the wire, but after 20 kg of bait per kilometre were placed along the wire, that time increased 20-fold on the first night and remained high for the next four nights (by which time all of the bait had been consumed). After that there was a gradual decline in time spent near the wire over a further 18 days. The increased amount of time spent near the wire was the product of both an increase in the number of visits and the duration of those visits. Conclusions. We conclude that sowing prefeed in concentrated strips is likely to greatly increase the probability of possums rapidly encountering toxic bait sown along the same strips, especially where the toxin can be sown immediately after all of the prefeed has been eaten. Implications. Possum control operations can now be designed to apply much smaller quantities of toxic bait that will potentially reduce concerns about 1080 poisoning because of a move away from broadcast sowing operations that are intuitively disliked by many, to much more localised baiting regimes.

Bayesian sample size for exploratory clinical trials incorporating historical data

This paper presents a simple Bayesian approach to sample size determination in clinical trials. It is required that the trial should be large enough to ensure that the data collected will provide convincing evidence either that an experimental treatment is better than a control or that it fails to improve upon control by some clinically relevant difference. The method resembles standard frequentist formulations of the problem, and indeed in certain circumstances involving 'non-informative' prior information it leads to identical answers. In particular, unlike many Bayesian approaches to sample size determination, use is made of an alternative hypothesis that an experimental treatment is better than a control treatment by some specified magnitude. The approach is introduced in the context of testing whether a single stream of binary observations are consistent with a given success rate p(0). Next the case of comparing two independent streams of normally distributed responses is considered, first under the assumption that their common variance is known and then for unknown variance. Finally, the more general situation in which a large sample is to be collected and analysed according to the asymptotic properties of the score statistic is explored.

Effect of restricted feeding and monopropylene glycol postpartum on metabolic hormones and postpartum anestrus in grazing dairy heifers

This study was designed to determine the effects of feed restriction and monopropylene glycol (MPG) supplementation on the reproductive, milk production, and somatotropic axes in dairy heifers postpartum. At calving, 49 Holstein-Friesian heifers were allowed either unrestricted (UNR; n = 18) or restricted access to pasture with (RES+MPG; n = 13) or without (RES; n = 18) MPG supplementation (250 mL drenched twice daily for 150 d). The average body condition score (BCS) of the heifers was 5.3 +/- 0.2 on a scale from 1 to 10 (where 1 = emaciated and 10 = obese). Body condition score and body weight were similar among the groups at calving and decreased after calving for all groups. However, body weight loss was around 10% greater for the RES and RES+MPG groups from wk 3 to 12 compared with UNR group. The length of the postpartum anestrous interval was similar for all groups (47, 51, and 45 +/- 5 d for the UNR, RES, and RES+MPG, respectively). Average milk production, protein, fat, and lactose yields during the first 12 wk postpartum were greater in the UNR group than in the RES and RES+MPG groups. Feed restriction affected plasma concentrations of insulin, with lower concentrations in the RES group compared with the UNR group. There were no differences in plasma concentrations of insulin between the RES+MPG group and the UNR or RES groups. An effect of feed restriction was observed on insulin-like growth factor-I concentrations and also a treatment by time interaction with a changing pattern through time as concentrations in the UNR group increased relative to the RES and RES+MPG groups. There were no differences in growth hormone concentrations among the groups. Glucose concentrations were lower in the RES group when compared with RES+MPG and UNR groups and this difference lessened over time. Plasma concentrations of nonesterified fatty acids were greater in the RES group compared with the RES+MPG and UNR groups. Leptin concentrations in the UNR group were greater than in the RES and RES+MPG groups. Hepatic growth hormone receptor 1A, total growth hormone receptor, and insulin-like growth factor-I relative mRNA expressions decreased postpartum with no effect of feed restriction, MPG supplementation, or interaction between time and treatment. During a challenge with MPG, insulin secretion was stimulated but no effect on postpartum anestrous interval in the treatment groups was observed. It was concluded that restricted pasture availability postpartum in dairy heifers calving in optimal BCS had no effect on the postpartum anestrous interval. It did however decrease milk production; thus, we can infer that monopropylene glycol supplementation does not act to prevent loss of milk yield.

Assessment of the impact of nutrient management practices on nitrate contamination in the Abbotsford-Sumas aquifer

The impact of recent changes to nutrient management practices in raspberry fields on the loading and subsequent transport of nitrate through the vadose zone of the Abbotsford-Sumas aquifer is investigated numerically. Previous studies have shown that nitrate concentrations in the aquifer have remained relatively stable despite a shift in nutrient management practices. Using an estimate of net annual available nitrogen in fields that are fertilized using synthetic fertilizer, nitrate concentrations as a function of time and depth through the vadose zone are simulated from spring to late fall. Results indicate rapid leaching of nitrate owing to the permeable nature of the aquifer and suggest that nitrate loading to the water table may occur earlier than previously thought, possibly due to spring rains. For an average fertilizer application rate of 90 kg of N/ha, the simulated nitrate concentration on Oct 1 within the top 1 m of soil is 33 mg of N/kg, while the residual soil nitrate measured in late September was 37 mg of N/kg. Taking into account the effects of dilution within the saturated zone, the simulated peak nitrate concentration is similar to average observed peak concentrations in a shallow monitoring well. A solution is offered for estimating nitrate concentration at the water table as a function of the rate of synthetic fertilizer applied to raspberry fields.

Filaggrin mutations are genetic modifying factors exacerbating X-linked ichthyosis

Mutations inactivating the STS gene cause X-linked ichthyosis (XLI), whereas null mutations in the FLG gene cause ichthyosis vulgaris. Two brothers presented with XLI. One had a typical fine scaling, and the other was much more severely affected. Both patients carried STS missense mutation T165I. Furthermore, the more severely affected patient also carried heterozygous FLG mutation R501X, which was absent from his mildly affected brother. These data suggest that disrupting epidermal differentiation via different pathways can increase phenotypic severity. Owing to the high population frequency of FLG mutations, filaggrin is a possible genetic modifier in other genodermatoses.

A program for individual and population optimal design for univariate and multivariate response pharmacokinetic-pharmacodynamic models

The design of pharmacokinetic and pharmacodynamic experiments concerns a number of issues, among which are the number of observations and the times when they are taken. Often a model is used to describe these data and the pharmacokinetic-pharmacodynamic behavior of a drug. Knowledge of the data analysis model at the design stage is beneficial for collecting patient data for parameter estimation. A number of criteria for model-oriented experiments, which maximize the information content of the data, are available. In this paper we present a program, Popdes, to investigate the D-optimal design of individual and population multivariate response models, such as pharmacokinetic-pharmacodynamic, physiologically based pharmacokinetic, and parent drug and metabolites models. A pre-clinical and clinical pharmacokinetic-pharmacodynamic model describing the concentration-time profile and effect of an oncology compound in development is used for illustration.

Optimal design for multiresponse pharmacokinetic-pharmacodynamic models - dealing with unbalanced designs

This paper addresses the problem of determining D-optimal designs for multiresponse pharmacokinetic-pharmacodynamic (PKPD) experiments where data on each response variable can be collected at different times. Most previous multiresponse model optimal design applications have considered the case where all response variables are measured at the same time points. However in practice it may not be possible to have all responses measured at the same sampling times. We propose an optimal design method to take into account the unbalanced nature of the problem. The method developed was applied to a PKPD problem that involved describing the time course of drug plasma concentrations, heart rate and mean arterial blood pressure for both a fixed effects and mixed effects regression model. Additionally a simulation study was carried out in NONMEM for one such population optimal design problem.

Epidemiology and incidence of Clostridium difficile-associated diarrhoea diagnosed upon admission to a university hospital

Patients with Clostridium difficile-associated diarrhoea (CDAD) may initially develop symptoms in the community and be subsequently diagnosed at hospital admission. At the present time there is no national surveillance system and no standardized case definition of CDAD in the USA, and baseline data on the incidence and epidemiology of CDAD are scarce. The objective of this study was to report the incidence of CDAD at a tertiary care hospital, and to determine the epidemiology of cases diagnosed within 48h of hospital admission, compared with cases of nosocomial CDAD diagnosed 48h or more after hospitalization. The average incidence was 4.0 cases/10 000 patient-days for CDAD on admission and 7.0 cases/10 000 patient-days for nosocomial CDAD. A significant difference was observed in CDAD rates on admission compared with nosocomial CDAD rates (P=0.017), but no differences were observed over time for either rate. Overall, 44% of cases had CDAD on admission and 56% of cases had nosocomial CDAD. Fifty-six (62%) patients with CDAD on admission had been admitted to the same hospital and 24 (27%) had been admitted to another hospital within the previous 90 days. Only eight (9%) patients had not been exposed to any healthcare services in the 90 days preceding hospital admission. A standardized case definition of healthcare-associated CDAD should include previous hospitalizations. Admitting physicians should consider C. difficile in the differential diagnosis of patients admitted with diarrhoea, with or without a history of admission to healthcare facilities.

Sample size calculations based on generalized estimating equations for population pharmacokinetic experiments

We present a method for calculating the sample size of a pharmacokinetic study analyzed using a mixed effects model within a hypothesis testing framework. A sample size calculation method for repeated measurement data analyzed using generalized estimating equations has been modified for nonlinear models. The Wald test is used for hypothesis testing of pharmacokinetic parameters. A marginal model for the population pharmacokinetic is obtained by linearizing the structural model around the subject specific random effects. The proposed method is general in that it allows unequal allocation of subjects to the groups and accounts for situations where different blood sampling schedules are required in different groups of patients. The proposed method has been assessed using Monte Carlo simulations under a range of scenarios. NONMEM was used for simulations and data analysis and the results showed good agreement.

Optimum blood sampling time windows for parameter estimation in population pharmacokinetic experiments

Clinical trials requiring the collection of pharmacokinetic information often specify blood samples to be taken at fixed times. This may be feasible when trial participants are in a controlled environment such as in early phase clinical trials, however it becomes problematic in trials where patients are in an out-patient clinic setting such as in late phase drug development. In such a situation it is common to take blood samples when it is convenient for all involved and may result in data that are uninformative. This paper proposes an approach to pharmacokinetic study design that allows greater flexibility as to when blood samples can be taken and still result in data that allows satisfactory parameter estimation. The sampling window approach proposed in this paper is based on determining time intervals around the D-optimum pharmacokinetic sampling times. These intervals are determined by allowing the sampling window design to result in a specified level of efficiency when compared to the fixed times D-optimum design. Several approaches are suggested for dealing with this design problem.

The use of a modified Fedorov exchange algorithm to optimise sampling times for population pharmacokinetic experiments

We propose a new algorithm for optimising sampling times for population pharmacokinetic experiments using D-optimality. The algorithm was used in conjunction with the population Fisher information matrix as implemented in MATLAB (PFIM 1.1 and 1.2) to evaluate population pharmacokinetic designs. The new algorithm based on the classical Fedorov exchange algorithm optimises the determinant of the population Fisher information matrix. The performance of the new algorithm has been compared with other existing algorithms including simplex, simulated annealing and adaptive random search. The new algorithm performed better especially when dealing with complex designs at the expense of longer computing times.

Measurement of dijet azimuthal decorrelations at central rapidities in pp collisions at sqrt s =1.96 TeV

Correlations in the azimuthal angle between the two largest transverse momentum jets have been measured using the D0 detector in p (-)p collisions at a center-of-mass energy sqrt[s]=1.96 TeV. The analysis is based on an inclusive dijet event sample in the central rapidity region corresponding to an integrated luminosity of 150 pb(-1). Azimuthal correlations are stronger at larger transverse momenta. These are well described in perturbative QCD at next-to-leading order in the strong coupling constant, except at large azimuthal differences where contributions with low transverse momentum are significant.

A program for the optimum design of pharmacokinetic, pharmacodynamic, drug metabolism and drug-drug interaction models

Planning any experiment includes issues such as how many samples are to be taken and their location given some predictor variable. Often a model is used to explain these data; hence including this formally in the design will be beneficial for any subsequent parameter estimation and modelling. A number of criteria for model oriented experiments, which maximise the information content of the collected data are available. In this paper we present a program, Optdes, to investigate the optimal design of pharmacokinetic, pharmacodynamic, drug metabolism and drug-drug interaction models. Using the developed software the location of either a predetermined number of design points (exact designs) or together with the proportion of samples at each point (continuous designs) can be determined. Local as well as Bayesian designs can be optimised by either D- or A-optimality criteria. Although often the optimal design cannot be applied for practical reasons, alternative designs can be readily evaluated.

Search for supersymmetry with gauge-mediated breaking in diphoton events at D0

We report the results of a search for supersymmetry (SUSY) with gauge-mediated breaking in the missing transverse energy distribution of inclusive diphoton events using 263 pb(-1) of data collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2004. No excess is observed above the background expected from standard model processes, and lower limits on the masses of the lightest neutralino and chargino of about 108 and 195 GeV, respectively, are set at the 95% confidence level. These are the most stringent limits to date for models with gauge-mediated SUSY breaking with a short-lived neutralino as the next-to-lightest SUSY particle.

Measurement of the B0s lifetime in the exclusive decay channel B0s-->J/psiphi

Using the exclusive decay B0s-->J/psi(mu+mu-)phi(K+K-), we report the most precise single measurement of the B0s lifetime. The data sample corresponds to an integrated luminosity of approximately 220 pb(-1) collected with the D0 detector at the Fermilab Tevatron Collider in 2002-2004. We reconstruct 337 signal candidates, from which we extract the B0s lifetime, tau(B0s)=1.444(+0.098)(-0.090)(stat)+/-0.020(sys) ps. We also report a measurement for the lifetime of the B0 meson using the exclusive decay B0-->J/psi(mu+mu-)K*0(892)(K+pi-). We reconstruct 1370 signal candidates, obtaining tau(B0)=1.473(+0.052)(-0.050)(stat)+/-0.023(sys) ps, and the ratio of lifetimes, tau(B0s)/tau(B0)=0.980(+0.076)(-0.071)(stat)+/-0.003(sys).

Observation and properties of the X(3872) decaying to J/psipi(+)pi(-) in pp collisions at sqrt[s]=1.96 TeV

We report the observation of the X(3872) in the J/psipi(+)pi(-) channel, with J/psi decaying to mu(+)mu(-), in pp collisions at sqrt[s]=1.96 TeV. Using approximately 230 pb(-1) of data collected with the Run II D0 detector, we observe 522+/-100 X(3872) candidates. The mass difference between the X(3872) state and the J/psi is measured to be 774.9+/-3.1(stat)+/-3.0(syst) MeV/c(2). We have investigated the production and decay characteristics of the X(3872) and find them to be similar to those of the psi(2S) state.

Search for doubly charged higgs boson pair production in the decay to mu(+)mu(+)mu(-)mu(-) in pp collisions at sqrt[s]=1.96 TeV

A search for pair production of doubly charged Higgs bosons in the process pp -->H(++)H(--) -->mu(+)mu(+)mu(-)mu(-) is performed with the D0 run II detector at the Fermilab Tevatron. The analysis is based on a sample of inclusive dimuon data collected at an energy of sqrt[s]=1.96 TeV, corresponding to an integrated luminosity of 113 pb(-1). In the absence of a signal, 95% confidence level mass limits of M(H(+/-+/-)(L))>118.4 GeV/c(2) and M(H(+/-+/-)(R))>98.2 GeV/c(2) are set for left-handed and right-handed doubly charged Higgs bosons, respectively, assuming 100% branching into muon pairs.

Silencing of CDKN1C (p57KIP2) is associated with hypomethylation at KvDMR1 in Beckwith-Wiedemann syndrome

CONTEXT

Beckwith-Wiedemann syndrome (BWS) arises by several genetic and epigenetic mechanisms affecting the balance of imprinted gene expression in chromosome 11p15.5. The most frequent alteration associated with BWS is the absence of methylation at the maternal allele of KvDMR1, an intronic CpG island within the KCNQ1 gene. Targeted deletion of KvDMR1 suggests that this locus is an imprinting control region (ICR) that regulates multiple genes in 11p15.5. Cell culture based enhancer blocking assays indicate that KvDMR1 may function as a methylation modulated chromatin insulator and/or silencer.

OBJECTIVE

To determine the potential consequence of loss of methylation (LOM) at KvDMR1 in the development of BWS.

METHODS

The steady state levels of CDKN1C gene expression in fibroblast cells from normal individuals, and from persons with BWS who have LOM at KvDMR1, was determined by both real time quantitative polymerase chain reaction (qPCR) and ribonuclease protection assay (RPA). Methylation of the CDKN1C promoter region was assessed by Southern hybridisation using a methylation sensitive restriction endonuclease.

RESULTS

Both qPCR and RPA clearly demonstrated a marked decrease (86-93%) in the expression level of the CDKN1C gene in cells derived from patients with BWS, who had LOM at KvDMR1. Southern analysis indicated that downregulation of CDKN1C in these patients was not associated with hypermethylation at the presumptive CDKN1C promoter.

CONCLUSIONS

An epimutation at KvDMR1, the absence of maternal methylation, causes the aberrant silencing of CDKN1C, some 180 kb away on the maternal chromosome. Similar to mutations at this locus, this silencing may give rise to BWS.