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Surrogate Endpoints (surrogate + endpoint)

Distribution by Scientific Domains

Medical Sciences	84%
Mathematics and Statistics	16%

Selected Abstracts

Considerations for Development of Surrogate Endpoints for Antifracture Efficacy of New Treatments in Osteoporosis: A Perspective,,

JOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2008
Mary L Bouxsein
Abstract Because of the broad availability of efficacious osteoporosis therapies, conduct of placebo-controlled trials in subjects at high risk for fracture is becoming increasing difficult. Alternative trial designs include placebo-controlled trials in patients at low risk for fracture or active comparator studies, both of which would require enormous sample sizes and associated financial resources. Another more attractive alternative is to develop and validate surrogate endpoints for fracture. In this perspective, we review the concept of surrogate endpoints as it has been developed in other fields of medicine and discuss how it could be applied in clinical trials of osteoporosis. We outline a stepwise approach and possible study designs to qualify a biomarker as a surrogate endpoint in osteoporosis and review the existing data for several potential surrogate endpoints to assess their success in meeting the proposed criteria. Finally, we suggest a research agenda needed to advance the development of biomarkers as surrogate endpoints for fracture in osteoporosis trials. To ensure optimal development and best use of biomarkers to accelerate drug development, continuous dialog among the health professionals, industry, and regulators is of paramount importance. [source]

Surrogate endpoints and emerging surrogate endpoints for risk reduction of cardiovascular disease

NUTRITION REVIEWS, Issue 2 2008
Crystal M Rasnake
This article reviews surrogate endpoints and emerging biomarkers that were discussed at the annual "Cardiovascular Biomarkers and Surrogate Endpoints" symposium cosponsored by the US Food and Drug Administration (FDA) and the Montreal Heart Institute. The FDA's Center for Food Safety and Applied Nutrition (CFSAN) uses surrogate endpoints in its scientific review of a substance/disease relationship for a health claim. CFSAN currently recognizes three validated surrogate endpoints: blood pressure, blood total cholesterol, and blood low-density lipoprotein (LDL) concentration in its review of a health claim for cardiovascular disease (CVD). Numerous potential surrogate endpoints of CVD are being evaluated as the pathophysiology of heart disease is becoming better understood. However, these emerging biomarkers need to be validated as surrogate endpoints before they are used by CFSAN in the evaluation of a CVD health claim. [source]

Importance of arterial stiffness as cardiovascular risk factor for future development of new type of drugs

FUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 3 2008
Pierre Boutouyrie
Abstract Cardiovascular risk prediction relies on classical risk factors such as age, gender, lipids, hypertension, smoking and diabetes. Although the value of such scales of risk is high for populations, its value for individual is reduced and too much influenced by non-modifiable risk factors (age and gender). Biomarkers of risk have been deceiving and genome wide scan approach is too recent. Target organ damage may help in selecting patients at high risk and in determining intervention. Aortic pulse wave velocity, an index of aortic stiffness, has been widely validated as providing additional risk predictions beyond and above classical risk factors, and has now entered into official guidelines. Many interventions (dietary, behaviour, drug treatment) were shown to influence arterial stiffness positively, but little evidence of a direct effect of intervention on arterial stiffness independent of blood pressure is available. New pharmacological targets and new drugs need to be identified. To become a surrogate endpoint for drug development, there is a need to demonstrate that regression arterial stiffness is associated with improved outcome. In parallel to this demonstration, points to be improved are the homogenization and spreading of the technique of measurement, the establishment of a reference value database. [source]

Introduction to therapy of hepatitis C

HEPATOLOGY, Issue 5B 2002
Karen L. Lindsay 1640 Marengo St.
Since the 1997 National Institutes of Health Consensus Development Conference on management of hepatitis C there have been several important advances that significantly impact its therapy; notably the availability of sensitive, specific, and standardized assays for identifying hepatitis C virus (HCV) RNA in the serum, the addition of ribavirin to alpha interferon, the pegylation of alpha interferon, and the demonstration that sustained virological response (SVR) is the optimal surrogate endpoint of treatment. Using pegylated interferon and ribavirin, virological response with relapse and nonresponse are less common, but remain poorly understood. Current studies are evaluating nonvirological endpoints of treatment, namely biochemical response and histological response. To date, definitive treatment trials have primarily been conducted in adult patients with elevated aminotransferase levels, clinically compensated chronic liver disease, and no other significant medical disorder. Limited data are available from studies of other patient populations, and the safety of interferon-based treatment has not yet been established in several patient groups. Future research is needed to elucidate the mechanisms of viral response and clearance, to develop effective therapies for interferon nonresponse or intolerance, to define the role of complementary and alternative medicine and other nonspecific therapies, and to develop strategies for the optimal management and treatment of special patient populations who probably represent the majority of persons with chronic hepatitis C in the United States. [source]

Introduction to therapy of hepatitis C

HEPATOLOGY, Issue S1 2002
Karen L. Lindsay M.D.
Since the 1997 National Institutes of Health Consensus Development Conference on management of hepatitis C there have been several important advances that significantly impact its therapy; notably the availability of sensitive, specific, and standardized assays for identifying hepatitis C virus (HCV) RNA in the serum, the addition of ribavirin to alpha interferon, the pegylation of alpha interferon, and the demonstration that sustained virological response (SVR) is the optimal surrogate endpoint of treatment. Using pegylated interferon and ribavirin, virological response with relapse and nonresponse are less common, but remain poorly understood. Current studies are evaluating nonvirological endpoints of treatment, namely biochemical response and histological response. To date, definitive treatment trials have primarily been conducted in adult patients with elevated aminotransferase levels, clinically compensated chronic liver disease, and no other significant medical disorder. Limited data are available from studies of other patient populations, and the safety of interferon-based treatment has not yet been established in several patient groups. Future research is needed to elucidate the mechanisms of viral response and clearance, to develop effective therapies for interferon nonresponse or intolerance, to define the role of complementary and alternative medicine and other nonspecific therapies, and to develop strategies for the optimal management and treatment of special patient populations who probably represent the majority of persons with chronic hepatitis C in the United States. (HEPATOLOGY 2002;36:S114,S120). [source]

Considerations for Development of Surrogate Endpoints for Antifracture Efficacy of New Treatments in Osteoporosis: A Perspective,,

Analysis of Implantable Cardioverter Defibrillator Therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 9 2003
RICHARD C. KLEIN M.D.
Introduction: The implantable cardioverter defibrillator (ICD) is commonly used to treat patients with documented sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Arrhythmia recurrence rates in these patients are high, but which patients will receive a therapy and the forms of arrhythmia recurrence (VT or VF) are poorly understood. Methods and Results: The therapy delivered by the ICD was examined in 449 patients randomized to ICD therapy in the Antiarrhythmics Versus Implantable Defibrillators (AVID) Trial. Events triggering ICD shocks or antitachycardia pacing (ATP) were reviewed for arrhythmia diagnosis, clinical symptoms, activity at the onset of the arrhythmia, and appropriateness and results of therapy. Both shock and ATP therapies were frequent by 2 years, with 68% of patients receiving some therapy or having an arrhythmic death. An appropriate shock was delivered in 53% of patients, and ATP was delivered in 68% of patients who had ATP activated. The first arrhythmia treated in follow-up was diagnosed as VT (63%), VF (13%), supraventricular tachycardia (18%), unknown arrhythmia (3%), or due to ICD malfunction or inappropriate sensing (3%). Acceleration of an arrhythmia by the ICD occurred in 8% of patients who received any therapy. No physical activity consistently preceded arrhythmias, nor did any single clinical factor predict the symptoms of the arrhythmia. Conclusion: Delivery of ICD therapy in AVID patients was common, primarily due to VT. Inappropriate ICD therapy occurred frequently. Use of ICD therapy as a surrogate endpoint for death in clinical trials should be avoided. (J Cardiovasc Electrophysiol, Vol. 14, pp. 940-948, September 2003) [source]

A preclinical pharmacokinetic/pharmacodynamic approach to determine a dose of GnRH, for treatment of ovarian follicular cyst in cattle

JOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 6 2004
S. MONNOYER
The objective of this study was to explore the value of a preclinical PK/PD approach to determine a gonadotropin-releasing hormone (GnRH) dose in cows using the pituitary LH response as a surrogate endpoint. Using an indirect effect model with stimulation of the LH entry rate, the in vivo basic pharmacodynamic parameters of GnRH were determined. The EC50 of GnRH was 51 ± 16 pg/mL, the EC50 being the GnRH plasma concentration able to produce 50% of the maximum possible stimulation (Smax) of the hypophysis (Smax = 48 ± 13). From individual PK/PD parameters, the ED50 of GnRH, i.e. the estimated dose of GnRH required to determine half the maximum possible stimulating effect on LH release, was calculated to 62 ,g/h per cow. Using the PK/PD model, the GnRH dose required to achieve a selected breakpoint value of 5 ng/mL for maximum LH concentration (surrogate value for LH concentration predicting clinical efficacy for cystic conditions), was 52 ± 18 ,g and for a standard GnRH dose of 100 ,g, the mean maximum plasma LH concentration predicted by the model was 7.22 ± 0.98 ng/mL. [source]

Chromium Picolinate Intake and Risk of Type 2 Diabetes: An Evidence-Based Review by the United States Food and Drug Administration

NUTRITION REVIEWS, Issue 8 2006
Paula R. Trumbo PhD
The labeling of both health claims that meet significant scientific agreement (SSA) and qualified health claims on conventional foods and dietary supplements requires pre-market approval by the US Food and Drug Administration (FDA). Approval by the FDA involves, in part, a thorough review of the scientific evidence to support an SSA or a qualified health claim. This article discusses FDA's evidence-based review of the scientific evidence on the role of chromium picolinate supplements in reducing the risk of type 2 diabetes. Based on this evidence-based review, FDA issued a letter of enforcement discretion for one qualified health claim on chromium picolinate and risk of insulin resistance, a surrogate endpoint for type 2 diabetes. The agency concluded that the relationship between chromium picolinate intake and insulin resistance is highly uncertain. SUMMARY In summary (Table 1), there was one intervention study that showed a beneficial effect of chromium picolinate intake on risk of insulin resistance. One other intervention study that provided chromium chloride showed no beneficial effect on insulin resistance. None of the five intervention studies showed a statistically significant beneficial effect of chromium picolinate on FBS and/or OGTT. Furthermore, none of the 10 intervention studies using other forms of chromium showed a beneficial effect of on FBS or OGTT in individuals with normal glucose tolerance. Based on FDA's evidence-based review, the agency concluded that there is very limited credible evidence for a qualified health claim for chromium picolinate and reduced risk of insulin resistance, and therefore reduced risk of type 2 diabetes. The findings of Cefalu et al. have not been replicated, and replication of scientific findings is important to substantiate results. For these reasons, FDA concluded that the existence of a relationship between chromium picolinate intake and reduced risk of either insulin resistance or type 2 diabetes is highly uncertain. On August 25, 2005, FDA issued a letter of enforcement discretion for the labeling of dietary supplements with the following qualified health claim: "One small study suggests that chromium picolinate may reduce the risk of insulin resistance, and therefore possibly may reduce the risk of type 2 diabetes. FDA concludes, however, that the existence of such a relationship between chromium picolinate and either insulin resistance or type 2 diabetes is highly uncertain." The agency concluded that there was no credible evidence to suggest that chromium picolinate intake may reduce the risk of elevated blood glucose levels. [source]

Antiretroviral effects on HIV-1 RNA, CD4 cell count and progression to AIDS or death: a meta-regression analysis

HIV MEDICINE, Issue 10 2008
EJ Mills
Objective Governments, clinicians and drug-licensing bodies have adopted changes in CD4 cell counts and HIV-1 RNA levels as evidence of effectiveness for new therapeutic interventions. We aimed to determine the strength of the association between the magnitude of the effect of changes in CD4 cell count and HIV-1 RNA and progression to AIDS or death in the highly active antiretroviral therapy (HAART) era. Methods We identified all randomized clinical trials (RCTs) evaluating the effect of HAART on both clinical and surrogate endpoints (1994 to September 2006). We performed a meta-regression and weighted linear regression. We additionally estimated potential RCT sample sizes that would be required to assess the effectiveness of new interventions in terms of clinical endpoints. Results We included data from 178 RCTs. We were unable to demonstrate a strong relationship at any time-point. Specifically, this was the case when CD4 T-cell change and clinical outcomes were examined at week 24 [coefficient ,0.01, 95% confidence interval (CI) ,0.03 to 0.001, P=0.54], week 48 (coefficient ,0.01, 95% CI ,0.02 to 0.001, P=0.83) and week 96 (coefficient 0.00, 95% CI ,0.03 to 0.04, P=0.76). This was also the case when viral load was examined as a surrogate marker. Given the small number of clinical events occurring in new interventional RCTs, any RCT aiming to evaluate clinical endpoints within these time-points would require an exceptionally large sample size. Conclusions Our findings indicate that, within short-term clinical trial settings, it is not possible to estimate the proportion of treatment effect associated with surrogate endpoints. [source]

Evidence for prolonged clinical benefit from initial combination antiretroviral therapy: Delta extended follow-up

HIV MEDICINE, Issue 3 2001
Delta Coordinating Committee
Background The findings from therapeutic trials in HIV infection with surrogate endpoints based on laboratory markers are only partially relevant for clinical decisions on treatment. Although the collection of clinical follow-up data from such a trial would be relatively straightforward, this rarely occurs. An important reason for this may be the perception that such data have little value because the number of participants remaining on their original allocated therapy has usually fallen substantially. Methods Delta was an international, multicentre trial in which 3207 HIV infected individuals were randomly allocated to treatment with zidovudine (ZDV) alone, ZDV combined with didanosine (ddI) or ZDV combined with zalcitabine (ddC). Although the trial closed in September 1995, information on vital status, AIDS events, treatment changes and CD4 counts was still collected every 12 months until at least March 1997. This has allowed analyses of the longer term clinical effect of treatment. Results The median follow-up to date of death or last known vital status was 43 months (10th percentile 18 months; 90th percentile 55 months). The proportion of participants remaining on their allocated treatment fell steadily over time; by 4 years after trial entry, 3% remained on ZDV, 20% on ZDV + ddI and 21% on ZDV + ddC. Changes mainly involved the stopping, addition or switching of a nucleoside reverse transcriptase inhibitor (NRTIs). There was little use of protease inhibitors (PIs) or non-nucleoside reverse transcriptase inhibitors (NNRTIs) before the third year of the trial. Between the third and fourth years, regimens included a drug from one of these classes for approximately 17% of person-time in all treatment groups. Relative to ZDV monotherapy, the beneficial effects of combination therapy on mortality and disease progression rates increased significantly with time since randomization. The maximum effects on mortality were observed between 2 and 3 years, with a 48% reduction for ZDV + ddI and a 26% reduction for ZDV + ddC. These rates were observed when the original allocated treatment was received 42% and 47% of the time in the ZDV + ddI and ZDV + ddC groups, respectively. The mean CD4 count remained significantly higher (approximately 50 cells/,L) in the combination therapy groups 4 years after randomization, suggesting a projection of a clinical benefit beyond this time point. Conclusions The sustained clinical effect of the initial allocation to combination therapy, particularly ZDV + ddI, was remarkable in light of the convergence of drug regimens actually received across the three treatment groups. Interpretation of this finding is not straightforward. One of the possible explanations is that the effectiveness of ddI and ddC is diminished if first used later in infection or with greater prior exposure to ZDV, although the data do not clearly support either hypothesis. This analysis highlights the value of long-term clinical follow-up of therapeutic trials in HIV infection, which should be considered in the planning of all new studies. [source]

Considerations for Development of Surrogate Endpoints for Antifracture Efficacy of New Treatments in Osteoporosis: A Perspective,,

Surrogate endpoints and emerging surrogate endpoints for risk reduction of cardiovascular disease

Biomarkers in drug development: friend or foe?

PHARMACEUTICAL STATISTICS: THE JOURNAL OF APPLIED STATISTICS IN THE PHARMACEUTICAL INDUSTRY, Issue 4 2007
A personal reflection gained working within oncology
Abstract Hopes and expectations for the use and utility of new, emerging biomarkers in drug development have probably never been higher, especially in oncology. Biomarkers are exalted as vital patient selection tools in an effort to target those most likely to benefit from a new drug, and so to reduce development costs, lessen risk and expedite developments times. It is further hoped that biomarkers can be used as surrogate endpoints for clinical outcomes, to demonstrate effectiveness and, ultimately, to support drug approval. However, I perceive that all is not straightforward, and, particularly in terms of the promise of accelerated drug development, biomarker strategies may not in all cases deliver the advances and advantages hoped for. Copyright © 2007 John Wiley & Sons, Ltd. [source]

The Elephant in the Room: Failings of Current Clinical Endpoints in Kidney Transplantation

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 5 2010
J. D. Schold
In this opinion piece, we address the limitations of the two most common clinical endpoints in kidney transplantation trials (acute rejection and renal function) and attempt to offer a reasonable framework by which to find true and reliable early endpoints that reflect long-term outcomes. Other potential endpoints tested in recent years, including the use of genomic and proteomic markers are still in development. Until other reliable endpoints are established, it is important to understand what can be inferred from ongoing studies that utilize these endpoints and what further information we need to derive ,true' surrogate endpoints. We consider evaluation of current markers using the ,Prentice criteria', which bases assessment of endpoints as true surrogates on four primary rules. Based on our assessment, progress in understanding the safety and efficacy of new therapies and interventions in kidney transplantation will remain limited with current makers. Prospectively, we advocate: (i) significant caution in extrapolating long-term outcomes from currently utilized clinical markers, (ii) use of traditional hard endpoints whenever feasible and (iii) dedication of efforts for more data collection on specific disease entities and greater diligence in determining the onset of deleterious processes. [source]

Validation of Surrogate Markers in Multiple Randomized Clinical Trials with Repeated Measurements

BIOMETRICAL JOURNAL, Issue 8 2003
Ariel Alonso
Abstract Part of the recent literature on the validation of biomarkers as surrogate endpoints proposes to undertake the validation exercise in a multi-trial context which led to a definition of validity in terms of the quality of both trial level and individual level association between the surrogate and the true endpoints (Buyse et al., 2000). These authors concentrated on continuous univariate responses. However, in many randomized clinical studies, repeated measurements are encountered on either or both endpoints. When both the surrogate and true endpoints are measured repeatedly over time, one is confronted with the modelling of bivariate longitudinal data. In this work, we show how such a joint model can be implemented in the context of surrogate marker validation. In addition, another challenge in this setting is the formulation of a simple and meaningful concept of "surrogacy". We propose the use of a new measure, the so-called variance reduction factor, to evaluate surrogacy at the trial and individual level. On the other hand, most of the work published in this area assume that only one potential surrogate is going to be evaluated. We also show that this concept will let us evaluate surrogacy when more than one surrogate variable is available for the analysis. The methodology is illustrated on data from a meta-analysis of five clinical trials comparing antipsychotic agents for the treatment of chronic schizophrenia. [source]

Assessing Vaccine Effects in Repeated Low-Dose Challenge Experiments

BIOMETRICS, Issue 4 2009
Michael G. Hudgens
Summary Evaluation of HIV vaccine candidates in nonhuman primates (NHPs) is a critical step toward developing a successful vaccine to control the HIV pandemic. Historically, HIV vaccine regimens have been tested in NHPs by administering a single high dose of the challenge virus. More recently, evaluation of candidate HIV vaccines has entailed repeated low-dose challenges, which more closely mimic typical exposure in natural transmission settings. In this article, we consider evaluation of the type and magnitude of vaccine efficacy from such experiments. Based on the principal stratification framework, we also address evaluation of potential immunological surrogate endpoints for infection. [source]

On Assessing Surrogacy in a Single Trial Setting Using a Semicompeting Risks Paradigm

BIOMETRICS, Issue 2 2009
Debashis Ghosh
Summary There has been a recent emphasis on the identification of biomarkers and other biologic measures that may be potentially used as surrogate endpoints in clinical trials. We focus on the setting of data from a single clinical trial. In this article, we consider a framework in which the surrogate must occur before the true endpoint. This suggests viewing the surrogate and true endpoints as semicompeting risks data; this approach is new to the literature on surrogate endpoints and leads to an asymmetrical treatment of the surrogate and true endpoints. However, such a data structure also conceptually complicates many of the previously considered measures of surrogacy in the literature. We propose novel estimation and inferential procedures for the relative effect and adjusted association quantities proposed by Buyse and Molenberghs (1998, Biometrics54, 1014,1029). The proposed methodology is illustrated with application to simulated data, as well as to data from a leukemia study. [source]

Ultrasonographic measurements of subclinical carotid atherosclerosis in prediction of ischemic stroke

ACTA NEUROLOGICA SCANDINAVICA, Issue 2009
E. B. Mathiesen
Carotid intima-media thickness (IMT) and plaque measurements are widely used to quantify atherosclerosis and assess the risk of future stroke, and are used as surrogate endpoints for clinical disease. In recent years, it has become clear that carotid IMT and plaque reflect biologically and genetically different aspects of the atherosclerotic process, and are differentially related to risk factors and cardiovascular disease. Plaques are focal manifestations of atherosclerosis while increased IMT represents mainly hypertensive medial hypertrophy. Several prospective studies have showed that IMT and plaque measurements, such as total plaque area and plaque number, are predictive of future stroke. Plaque echogenicity predicts future stroke independent of plaque size. The contribution of IMT and plaque measurements in individual stroke risk prediction in the general population seems to be limited, but may be useful as a tool for individual stratification of high-risk patients. [source]

Newer risk markers and surrogate endpoints in atherosclerosis management

CLINICAL CARDIOLOGY, Issue S3 2001
Christie M. Ballantyne M.D.
Abstract Summary: Risk markers that allow improved and individualized assessment of atherosclerotic disease risk and response to treatment are needed. Current candidate markers include cell adhesion molecules, such as intercellular adhesion molecule-1 and E-selectin, and inflammatory markers, such as C-reactive protein; advances in genomics and proteomics will suggest additional candidate markers. Noninvasive imaging procedures such as electron-beam computed tomography and magnetic resonance imaging also show considerable promise for monitoring disease status and response to treatment, and ultimately could provide surrogate endpoints for clinical trials of therapeutic interventions. [source]