We describe a directed evolution approach that should find broad application in generating enzymes that meet predefined process-design criteria. It augments recombination-based directed evolution by incorporating a strategy for statistical analysis of protein sequence activity relationships (ProSAR). This combination facilitates mutation-oriented enzyme optimization by permitting the capture of additional information contained in the sequence-activity data. The method thus enables identification of beneficial mutations even in variants with reduced function. We use this hybrid approach to evolve a bacterial halohydrin dehalogenase that improves the volumetric productivity of a cyanation process approximately 4,000-fold. This improvement was required to meet the practical design criteria for a commercially relevant biocatalytic process involved in the synthesis of a cholesterol-lowering drug, atorvastatin (Lipitor), and was obtained by variants that had at least 35 mutations.

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Of the five interventions, only raloxifene appeared to reduce the risk of vertebral fracture in postmenopausal women unselected for low bone mineral density (BMD). However, as the full data have not been made public, there is some uncertainty regarding this result. None of the five interventions has been shown to reduce the risk of non-vertebral fracture in women unselected for low BMD. All of the proposed interventions provided gains in QALYs compared with no treatment in women with sufficient calcium and vitamin D intakes. The size of the QALY gain for each intervention was strongly related to the age of the patient. The estimated costs varied widely for the interventions. These net costs were markedly different by age, with some interventions becoming cost-saving at higher age ranges in patients with a prior fracture. Areas for future research include: the evidence base for the efficacy of fracture prevention in the very elderly, reanalysis of raloxifene using a dedicated breast cancer and CHD model, and more trials considering the cost-effectiveness of teriparatide.

BackgroundIt is estimated that only 39% of men and 29% of women in England achieve the levels of physical activity that are recommended to protect health and prevent disease. One approach to addressing this problem has been the development of exercise referral schemes (ERSs), in which health professionals refer patients to external exercise providers. These schemes have been widely rolled out across the UK despite concerns that they may not produce sustained changes in levels of physical activity and, therefore, may not be cost-effective interventions. The evidence to determine clinical effectiveness and cost-effectiveness was evaluated in 2009. This review seeks to update this earlier work by incorporating new evidence and re-examining the cost-effectiveness.ObjectivesTo assess the clinical effectiveness and cost-effectiveness of ERSs compared with usual care.DesignExhaustive searches of relevant electronic databases and journals were undertaken to identify new studies evaluating ERSs using a randomised controlled trial (RCT) design. RCTs that incorporated a qualitative evaluation of the intervention were identified in order to explore the barriers and facilitators to the uptake of and adherence to ERSs. Data were extracted using a previously designed tool and study quality assessed for potential bias. Where data could be pooled, meta-analyses were carried out. Qualitative analysis was also undertaken using a thematic approach. The cost-effectiveness was evaluated using a Markov structure which estimated the likelihood of becoming physically active and the subsequent risk reduction on coronary heart disease (CHD), stroke and type 2 diabetes mellitus. The model adopts a lifetime horizon, and a NHS and Personal Social Services perspective was taken with discounting at 1.5% for both costs and benefits.ResultsThe search identified one new RCT and one new qualitative study. The new data were pooled with existing data from the 2011 review by Paveyet al.[Pavey TG, Anokye N, Taylor AH, Trueman P, Moxham T, Fox KR,et al.The clinical effectiveness and cost-effectiveness of exercise referral schemes: a systematic review and economic evaluation.Health Technol Assess2011;15(44)] to give a total of eight studies with 5190 participants. The proportion of individuals achieving 90–150 minutes of at least moderate-intensity activity per week at 6–12 months’ follow-up was greater for ERSs than usual care (relative risk 1.12; 95% confidence interval 1.04 to 1.20). Older patients and those referred for CHD risk factors appeared to be more likely than others to increase their levels of physical activity. Qualitative evidence suggests that interventions enabling the development of social support networks are beneficial in promoting uptake and adherence. Exercise referral gained 0.003 quality-adjusted life-years (QALYs) at an additional cost of £225 per person. The estimated mean incremental cost-effectiveness ratio (ICER) in the probabilistic sensitivity analysis was £76,276. In the univariate sensitivity analysis the results were very sensitive (ICERs ranged from < £30,000 to > £100,000) to changes in the effect of ERSs on physical activity uptake and the duration of the protective effects and the direct health-related quality-of-life gains attributable to physical activity.ConclusionsExercise referral schemes result in a small improvement in the number of people who increase their levels of physical activity. The cost-effectiveness analysis indicates that the ICER for ERSs compared with usual care is around £76,000 per QALY, although the cost-effectiveness of ERSs is subject to considerable uncertainty.Study registrationThis study is registered as PROSPERO CRD42013005200.FundingNational Institute for Health Research Health Technology Assessment programme.

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