Despite major advances in modern drug discovery and development, the number of new drug approvals has not kept pace with the increased cost of their development. Increasingly, innovative uses of biomarkers are employed in an attempt to speed new drugs to market. Still, widespread adoption of biomarkers is impeded by limited experience interpreting biomarker data and an unclear regulatory climate. Key differences preclude the direct application of existing validation paradigms for drug analysis to biomarker research. Following the AAPS 2003 Biomarker Workshop (J. W. Lee, R. S. Weiner, J. M. Sailstad, et al. Method validation and measurement of biomarkers in nonclinical and clinical samples in drug development. A conference report. Pharm Res 22:499-511, 2005), these and other critical issues were addressed. A practical, iterative, "fit-for-purpose" approach to biomarker method development and validation is proposed, keeping in mind the intended use of the data and the attendant regulatory requirements associated with that use. Sample analysis within this context of fit-for-purpose method development and validation are well suited for successful biomarker implementation, allowing increased use of biomarkers in drug development.

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Remyelination is the generation of new myelin sheaths after injury facilitated by processes of differentiating oligodendrocyte precursor cells (OPCs). Although this repair phenomenon occurs in lesions of multiple sclerosis patients, many lesions fail to completely remyelinate. A number of factors have been identified that contribute to remyelination failure, including the upregulated chondroitin sulfate proteoglycans (CSPGs) that comprise part of the astrogliotic scar. We show that in vitro, OPCs have dramatically reduced process outgrowth in the presence of CSPGs, and a medication library that includes a number of recently reported OPC differentiation drugs failed to rescue this inhibitory phenotype on CSPGs. We introduce a novel CSPG synthesis inhibitor to reduce CSPG content and find rescued process outgrowth from OPCs in vitro and accelerated remyelination following focal demyelination in mice. Preventing CSPG deposition into the lesion microenvironment may be a useful strategy to promote repair in multiple sclerosis and other neurological disorders.

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Our objective was to develop a beta regression (BR) model to describe the longitudinal progression of the 11 item Alzheimer's disease (AD) assessment scale cognitive subscale (ADAS-cog) in AD patients in both natural history and randomized clinical trial settings, utilizing both individual patient and summary level literature data. Patient data from the coalition against major diseases database (3,223 patients), the Alzheimer's disease neruroimaging initiative study database (186 patients), and summary data from 73 literature references (representing 17,235 patients) were fit to a BR drug-disease-trial model. Treatment effects for currently available acetyl cholinesterase inhibitors, longitudinal changes in disease severity, dropout rate, placebo effect, and factors influencing these parameters were estimated in the model. Based on predictive checks and external validation, an adequate BR meta-analysis model for ADAS-cog using both summary-level and patient-level data was developed. Baseline ADAS-cog was estimated from baseline MMSE score. Disease progression was dependent on time, ApoE4 status, age, and gender. Study drop out was a function of time, baseline age, and baseline MMSE. The use of the BR constrained simulations to the 0-70 range of the ADAS-cog, even when residuals were incorporated. The model allows for simultaneous fitting of summary and patient level data, allowing for integration of all information available. A further advantage of the BR model is that it constrains values to the range of the original instrument for simulation purposes, in contrast to methodologies that provide appropriate constraints only for conditional expectations.

For decades lysophosphatidylcholine (LPC, lysolecithin) has been used to induce demyelination, without a clear understanding of its mechanisms. LPC is an endogenous lysophospholipid so it may cause demyelination in certain diseases. We investigated whether known receptor systems, inflammation or nonspecific lipid disruption mediates LPC-demyelination in mice. We found that LPC nonspecifically disrupted myelin lipids. LPC integrated into cellular membranes and rapidly induced cell membrane permeability; in mice, LPC injury was phenocopied by other lipid disrupting agents. Interestingly, following its injection into white matter, LPC was cleared within 24 hr but by five days there was an elevation of endogenous LPC that was not associated with damage. This elevation of LPC in the absence of injury raises the possibility that the brain has mechanisms to buffer LPC. In support, LPC injury in culture was significantly ameliorated by albumin buffering. These results shed light on the mechanisms of LPC injury and homeostasis.

Although immune attack against central nervous system (CNS) myelin is a central feature of multiple sclerosis (MS), its root cause is unresolved. In this report, we provide direct evidence that subtle biochemical modifications to brain myelin elicit pathological immune responses with radiological and histological properties similar to MS lesions. A subtle myelinopathy induced by abbreviated cuprizone treatment, coupled with subsequent immune stimulation, resulted in lesions of inflammatory demyelination. The degree of myelin injury dictated the resulting immune response; biochemical damage that was too limited or too extensive failed to trigger overt pathology. An inhibitor of peptidyl arginine deiminases (PADs), enzymes that alter myelin structure and correlate with MS lesion severity, mitigated pathology even when administered only during the myelin-altering phase. Moreover, cultured splenocytes were reactive against donor myelin isolates, a response that was substantially muted when splenocytes were exposed to myelin from donors treated with PAD inhibitors. By showing that a primary biochemical myelinopathy can trigger secondary pathological inflammation, "cuprizone autoimmune encephalitis" potentially reconciles conflicting theories about MS pathogenesis and provides a strong rationale for investigating myelin as a primary target for early, preventative therapy.

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