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1.
J Biopharm Stat ; : 1-16, 2020 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-32089068

RESUMO

As indicated in a recent published draft guidance on comparative analytical assessment, the United States (US) Food and Drug Administration (FDA) seems to suggest the use of quality range (QR) method for analytical similarity evaluation. It is a concern that the use of QR method for analytical similarity evaluation could potentially approve biological products which are not deemed biosimilar to the reference biological products. In this article, the limitations and potential risk for the use of the QR method for analytical similarity evaluation are discussed. Alternatively, two modified versions of the QR method, which are referred to as effect size (ES) mQR and plausibility interval (PI) mQR methods are suggested. The performance and statistical properties of the mQR methods are evaluated via extensive clinical trial simulation under various scenarios. The results indicate that the modified versions of the QR method not only overcome the limitations of the QR method for analytical similarity evaluation, but also can potentially help in detecting reference product changes during manufacturing process.

2.
J Biopharm Stat ; : 1-10, 2020 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-32065018

RESUMO

Two dissimilarity indices are introduced to measure the disharmony of a human body system by mimicking the population bioequivalence and the individual bioequivalence concepts. Hypotheses for the treatment effect of a traditional Chinese medicine are formulated based on the two indices and then tested under the proposed designs by reverting an approximate confidence upper bound. The proposed methods can also be used when a drug product has multiple components or a trial has multiple endpoints.

3.
J Biopharm Stat ; : 1-13, 2020 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-32065047

RESUMO

One of the most challenges for rare diseases drug development is probably the availability of subjects with the diseases under a small patient population. It is then a great concern how to conduct clinical trials with the limited number of subjects available for obtaining substantial evidence regarding effectiveness and safety for approval of the drug product under investigation. For rare diseases drug development, FDA indicated that the Agency does not have the intention to create a statutory standard for approval of orphan drugs that is different from the standard for approval of drugs in common conditions. In this case, innovative thinking and approach for obtaining substantial evidence for approval of rare diseases drug products are necessarily applied. In this article, basic considerations for rare disease drug development are discussed. The innovative thinking of demonstrating not-ineffectiveness rather than effectiveness with a limited number of subjects available is outlined. In addition, an innovative approach utilizing a two-stage adaptive seamless trial design in conjunction with the concept of real-world data and real-world evidence is proposed not only to obtain substantial evidence for approval of rare diseases drug products, but also to meet the same standard as those drug products in common conditions. Under the two-stage adaptive seamless trial design, sample size calculation for rare diseases clinical trials based on the innovative probability monitoring procedure is also discussed.

4.
Hepatol Int ; 14(1): 105-114, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31898210

RESUMO

BACKGROUND: Controversy exists on whether tenofovir disoproxil fumarate (TDF) is superior to entecavir (ETV) in lowering the risk of hepatocellular carcinoma (HCC) development. This meta-analysis was performed to clarify this issue with critical clinical and methodological considerations. METHODS: PubMed, EMBASE, and Cochrane Library were searched from inception to Oct 28, 2019. Randomized control trials and observational studies reporting the impact of TDF and ETV on the risk of HCC in patients with chronic hepatitis B (CHB) were eligible. Risk ratios (RRs) calculated with cumulative incidence rate and/or annual incidence rate, or hazard ratio (HR) were pooled using random-effect models. Subgroup analyses were performed to assess the potential impact of between-study level and within-study level factors. RESULTS: A total of 32 studies with 78,136 CHB patients were included. Overall cumulative incidence rate of HCC was lower in TDF group than ETV group (3.07% vs. 5.25%; RR 0.55; 95% CI 0.42-0.72). However, this difference was not statistically significant in pooled results of hazard ratio (HR 0.87; 95% CI 0.73-1.04) and RR calculated with annual incidence rate (RR 0.88; 95% CI 0.67-1.16). Potential confounding factors at between-study level included prior nucleos(t)ide usage, disease stage at baseline and region of study. More importantly, at within-study level, disparity in follow-up duration between TDF and ETV groups may impact the result, usually favoring a treatment with shorter follow-up duration. CONCLUSIONS: Compared with ETV, TDF treatment tended to have a lower overall cumulative incidence rate of HCC. However, disparity in follow-up duration may be a key factor to influence the result.

5.
J Biopharm Stat ; 29(5): 908-919, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31495271

RESUMO

In pharmaceutical/clinical development, two-stage seamless adaptive designs are commonly considered. Such designs include a two-stage phase I/II or phase II/III adaptive trial that combines one phase IIb study for dose-finding or treatment selection and one phase III study for efficacy confirmation into a single study. At the end of stage 1, promising dose(s) will be selected based on pre-specified selection criteria. In practice, since there is little power with limited subjects available at interim, commonly considered selection criteria for critical decision-making include (i) conditional power, (ii) precision analysis, (iii) predictive probability of success, and (iv) probability of being the best dose or treatment. The selected promising dose(s) will then proceed to the next stage for efficacy confirmation. In this article, we introduce, compare, and evaluate these criteria. Simulation studies and a numeric example are given to illustrate those criteria. Besides, we attempt to address some concerns for the two-stage seamless adaptive clinical trial.

6.
J Biopharm Stat ; 29(5): 941-951, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31454270

RESUMO

In clinical trials, selection of appropriate study endpoints is critical for an accurate and reliable evaluation of safety and effectiveness of a test treatment under investigation. In practice, however, there are usually multiple endpoints available for measurement of disease status and/or therapeutic effect of the test treatment under study. For example, in cancer clinical trials, overall survival, response rate, and/or time to disease progression are usually considered as primary clinical endpoints for evaluation of safety and effectiveness of the test treatment under investigation. Once the study endpoints have been selected, sample size required for achieving a desired power is then determined. It, however, should be noted that different study endpoints may result in different sample sizes. In practice, it is usually not clear which study endpoint can best inform the disease status and measure the treatment effect. Moreover, different study endpoints may not translate one another although they may be highly correlated one another. In this article, we intend to develop an innovative endpoint namely therapeutic index based on a utility function to combine and utilize information collected from all study endpoints. Statistical properties and performances of the proposed therapeutic index are evaluated theoretically. A numerical example concerning a cancer clinical trial is given to illustrate the use of the proposed therapeutic index.

7.
J Biopharm Stat ; 29(5): 887-896, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31454274

RESUMO

In clinical research, power analysis is often performed for sample size calculation. The purpose is to achieve a desired power of correctly detecting a clinically meaningful difference at a pre-specified level of significance if such a difference truly exists. However, in some situations such as (i) clinical trials with extremely low incidence rates and (ii) for rare disease drug development clinical trials, power analysis for sample size calculation may not be feasible because (i) it may require a huge sample size for detecting a relatively small difference and (ii) eligible patients may not be available for a small target patient population. In these cases, other procedures for sample size determination with certain statistical assurance are needed. In this article, an innovative method based on a probability monitoring procedure is proposed for sample size determination. The concept is to select an appropriate sample size for controlling the probability of crossing safety and/or efficacy boundaries. For rare disease clinical development, an adaptive probability monitoring procedure may be applied if a multiple-stage adaptive trial design is used.

8.
J Biopharm Stat ; 29(5): 920-940, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31454290

RESUMO

In analytical similarity assessment of a biosimilar product, key quality attributes of the test and reference products need to be shown statistically similar. When there were multiple references, similarity among the reference products is also required. We proposed a simultaneous confidence approach based on the fiducial inference theory as an alternative to the pairwise comparison method. Three versions with two types of simultaneous confidence intervals for each version were proposed based on different assumptions of the population variance. We conducted extensive simulation studies to compare the performance of our proposed method and the pairwise method, and provided examples to illustrate the concern of using pairwise method.

9.
J Biopharm Stat ; 29(5): 834-844, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31454298

RESUMO

For review and approval of drug products, a 95% confidence interval approach for evaluation of new drugs is commonly used, while a 90% confidence interval approach is considered for assessment of generic drugs and biosimilar products. In the past decade, FDA has been challenged for adopting different standards (i.e., 5% type-I error rate for new drugs and 10% type-I error rate for generics/biosimilars) for regulatory submissions of drugs and biologics. This note intends to clarify the confusion by pointing out the fundamental differences between (i) the concepts of point hypotheses and interval hypotheses, and (ii) the concepts of interval hypotheses testing and confidence interval approach. In general, the method of interval hypotheses testing is not equivalent to the confidence interval approach although they may be operationally equivalent under certain conditions.

10.
J Biopharm Stat ; 29(5): 874-886, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31454299

RESUMO

One of the most challenges for rare disease clinical trials is probably the availability of a small patient population. It is then a great concern on how to conduct clinical trials with a small number of subjects available for obtaining substantial evidence regarding safety and effectiveness for approval of the rare disease drug product under investigation. FDA, however, does not have the intention to create a statutory standard for approval of orphan drugs that are different from the standard for approval of drugs in common conditions. Thus, it is suggested that innovative trial designs such as a complete n-of-1 trial design or an adaptive design should be used for an accurate and reliable assessment of rare disease drug products under investigation. In this article, basic considerations, innovative trial designs, and statistical methods for data analysis are discussed. In addition, some innovative thinking for the evaluation of rare disease drug products is proposed.

11.
J Biopharm Stat ; 29(5): 897-907, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31454301

RESUMO

For review and approval of new drug products, substantial evidence regarding safety and effectiveness of the drug products under investigation are necessarily provided. A traditional approach is to test a null hypothesis of ineffectiveness against an alternative hypothesis of effectiveness at the 5% level of significance. The rejection of the null hypothesis of ineffectiveness is in favor of the alternative hypothesis of effectiveness. This approach, however, is somewhat misleading because the rejection of the null hypothesis of ineffectiveness leads to the conclusion of not ineffectiveness, which consists of the proportion of inconclusiveness and the proportion of effectiveness. In this article, we explore the potential use of the concept of demonstrating not ineffectiveness and then effectiveness for regulatory approval of new drug products, especially for rare disease drug products. For rare disease drug product development, one of the major obstacles and challenges is how to use small patient population available for achieving the same standards for regulatory approval. To address this problem, a two-stage approach by first demonstrating not ineffectiveness and then ruling out (or controlling) the probability of inconclusiveness for demonstrating effectiveness is proposed. The proposed two-stage approach is useful with small patient population available for achieving the same standards for regulatory approval of rare disease drug products.

12.
South Med J ; 112(4): 222-227, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30943541

RESUMO

OBJECTIVES: Accurate localization of a colonic lesion is crucial to successful resection. Although colonic tattooing is a widely accepted technique to mark lesions for future identification surgery or repeat colonoscopy, no consensus guidelines exist. The objective of this study was to determine whether the current tattooing practice at a tertiary medical center differs from recommendations in the literature and self-reported provider practice. METHODS: The study consisted of an observational retrospective chart review of patients who received colonic tattoos, as well as a provider survey of reported tattooing practices at a tertiary academic medical center. A total of 747 patients older than 18 years of age who underwent colonoscopy with tattoo were included. Forty-four gastroenterologists performing endoscopy were surveyed on tattooing techniques. RESULTS: In the majority of cases, neither the number of tattoos, location of the tattoo nor the distance from the lesion was specified within the report. Following the index procedure, a tattoo was detected in 75% of surgical resections and 73% of endoscopies. At the time of surgery, however, the tattoo and/or the lesion was detected approximately 94% of the time. Twenty-five endoscopists (56.8%) completed the survey. Differences were seen the between the chart review and reported practice. Most providers report placing ≥2 marks (87.2%); however, chart review revealed that only 56.2 % were tattooed with ≥2 marks. CONCLUSIONS: Variation exists between the reported tattooing practice and actual practice. Despite this, most tattoos are identified at the time of surgery or repeat endoscopy. Further research is needed to determine whether a standardized approach to tattooing and reporting could improve localization at repeat endoscopy.


Assuntos
Pólipos do Colo/cirurgia , Colonoscopia/métodos , Neoplasias Colorretais/cirurgia , Documentação/estatística & dados numéricos , Gastroenterologistas , Padrões de Prática Médica/estatística & dados numéricos , Tatuagem/estatística & dados numéricos , Adulto , Idoso , Idoso de 80 Anos ou mais , Pólipos do Colo/diagnóstico , Neoplasias Colorretais/diagnóstico , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Tatuagem/métodos , Centros de Atenção Terciária , Adulto Jovem
13.
Artigo em Inglês | MEDLINE | ID: mdl-30712076

RESUMO

PURPOSE: Patients with atrial fibrillation (AF) undergoing cardiac surgery are at substantially increased risk for stroke. Increasing evidence has suggested that surgical left atrial appendage occlusion (S-LAAO) may have the potential to substantially mitigate this stroke risk; however, S-LAAO is performed in a minority of patients with AF undergoing cardiac surgery. We sought to identify factors associated with usage of S-LAAO. METHODS: In a nationally-representative, contemporary cohort (07/2011-06/2012) of older patients undergoing cardiac surgery with preoperative AF (n = 11,404) from the Medicare-linked Society of Thoracic Surgeons Adult Cardiac Surgery Database, we evaluated patient and hospital characteristics associated with S-LAAO use by employing logistic and linear regression models. RESULTS: In this cohort (average age, 76 years; 39% female), 4177 (37%) underwent S-LAAO. Neither S-LAAO nor discharge anticoagulation was used in 25% ("unprotected" patients). The overall propensity for S-LAAO decreased significantly with increasing CHA2DS2-VASc (congestive heart failure; hypertension; age 75 years or older; diabetes mellitus; stroke, transient ischemic attack, or thromboembolism; vascular disease; age 65 to 74 years; sex category (female)) score (ptrend < 0.001). There was substantial variability in S-LAAO use across geographic regions, and S-LAAO was more commonly performed at academic and higher-volume valve surgery centers. CONCLUSIONS: Substantial variability in use of S-LAAO exists. In many instances, the procedure is being deferred in the patients that may be poised to benefit the most (i.e., those with increased CHA2DS2-VASc score-defined stroke risk).

15.
J Biopharm Stat ; 29(2): 400-410, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30599798

RESUMO

In clinical trials, where the outcome of interest is the occurrence of an event over a fixed time period, estimation of the event proportion at interim analysis can form a basis for decision-making such as early trial termination, sample size re-estimation, and/or dropping inferior treatment arms. In addition to derivation of mean squared error under an exponential time-to-event distribution, we performed a simulation study to examine the performance of five estimators of the event proportion when time to the event is assessable. The simulation results showed advantages of the Kaplan-Meier estimator over others in terms of robustness, and the bias and variability of the event proportion estimate. An example was given to illustrate how the estimators affect dropping treatment arms in a multi-arm multi-stage adaptive trial. We recommended the use of the Kaplan-Meier estimator and discourage the use of other estimators that discard the inherent time-to-event information.

16.
Ther Innov Regul Sci ; 53(3): 374-380, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-29909649

RESUMO

Regulatory inspection of clinical trial is necessary in order for (1) assessing compliance with statutory requirements and regulatory requirement governing the conduct of clinical trials and (2) verifying the accuracy and reliability of clinical trial data submitted to regulatory agencies such as the United States Food and Drug Administration (FDA) in support of research or marketing applications. This article provides an overview of clinical inspection process and issues that are commonly encountered during the conduct of clinical trials. In addition, a couple of sampling plans for clinical inspection of relatively large trials are proposed. The proposed statistical process for clinical inspection that will achieve a desired degree of inspection accuracy and reliability is useful when the resources of inspectors are limited. The proposed 2-stage sampling plan can be applied to clinical inspection for multicenter and/or multinational multicenter clinical trials.


Assuntos
Ensaios Clínicos como Assunto/normas , United States Food and Drug Administration/normas , Ensaios Clínicos como Assunto/legislação & jurisprudência , Guias como Assunto , Humanos , Controle de Qualidade , Estados Unidos , United States Food and Drug Administration/organização & administração
17.
Pharmaceut Med ; 33(5): 379-388, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31933227

RESUMO

Under the US Biologics Price Competition and Innovation Act of 2009 (BPCI), the development of biosimilar (test) products provides affordable alternatives to innovative biological (reference) products for the general patient population. However, in practice, as the number of biosimilar products available on the market increases, whether these biosimilars can be used interchangeably is a concern. Thus, using switching studies to evaluate the risk of reduced efficacy and increased safety concerns with and without switch(es) in the development of biosimilar products is of interest. For this purpose, the US FDA, in its recent draft guidance on interchangeability, suggested using a 2 × 2 crossover design (RT, RR) to evaluate a single switch and (RTR, RRR) and (RTRT, RRRR) to evaluate multiple switches. In this article, we examine the statistical properties, analyses, and sample size requirements of these switching study designs. We also investigate the relative efficiencies of these switching designs compared with the complete  n-of-1 trial design.

18.
JAMA ; 320(12): 1249-1258, 2018 09 25.
Artigo em Inglês | MEDLINE | ID: mdl-30264119

RESUMO

Importance: The appropriate duration of antibiotics for staphylococcal bacteremia is unknown. Objective: To test whether an algorithm that defines treatment duration for staphylococcal bacteremia vs standard of care provides noninferior efficacy without increasing severe adverse events. Design, Setting, and Participants: A randomized trial involving adults with staphylococcal bacteremia was conducted at 16 academic medical centers in the United States (n = 15) and Spain (n = 1) from April 2011 to March 2017. Patients were followed up for 42 days beyond end of therapy for those with Staphylococcus aureus and 28 days for those with coagulase-negative staphylococcal bacteremia. Eligible patients were 18 years or older and had 1 or more blood cultures positive for S aureus or coagulase-negative staphylococci. Patients were excluded if they had known or suspected complicated infection at the time of randomization. Interventions: Patients were randomized to algorithm-based therapy (n = 255) or usual practice (n = 254). Diagnostic evaluation, antibiotic selection, and duration of therapy were predefined for the algorithm group, whereas clinicians caring for patients in the usual practice group had unrestricted choice of antibiotics, duration, and other aspects of clinical care. Main Outcomes and Measures: Coprimary outcomes were (1) clinical success, as determined by a blinded adjudication committee and tested for noninferiority within a 15% margin; and (2) serious adverse event rates in the intention-to-treat population, tested for superiority. The prespecified secondary outcome measure, tested for superiority, was antibiotic days among per-protocol patients with simple or uncomplicated bacteremia. Results: Among the 509 patients randomized (mean age, 56.6 [SD, 16.8] years; 226 [44.4%] women), 480 (94.3%) completed the trial. Clinical success was documented in 209 of 255 patients assigned to algorithm-based therapy and 207 of 254 randomized to usual practice (82.0% vs 81.5%; difference, 0.5% [1-sided 97.5% CI, -6.2% to ∞]). Serious adverse events were reported in 32.5% of algorithm-based therapy patients and 28.3% of usual practice patients (difference, 4.2% [95% CI, -3.8% to 12.2%]). Among per-protocol patients with simple or uncomplicated bacteremia, mean duration of therapy was 4.4 days for algorithm-based therapy vs 6.2 days for usual practice (difference, -1.8 days [95% CI, -3.1 to -0.6]). Conclusions and Relevance: Among patients with staphylococcal bacteremia, the use of an algorithm to guide testing and treatment compared with usual care resulted in a noninferior rate of clinical success. Rates of serious adverse events were not significantly different, but interpretation is limited by wide confidence intervals. Further research is needed to assess the utility of the algorithm. Trial Registration: ClinicalTrials.gov Identifier: NCT01191840.


Assuntos
Algoritmos , Antibacterianos/uso terapêutico , Bacteriemia/tratamento farmacológico , Infecções Estafilocócicas/tratamento farmacológico , Staphylococcus aureus , Adulto , Idoso , Idoso de 80 Anos ou mais , Antibacterianos/efeitos adversos , Coagulase , Intervalos de Confiança , Esquema de Medicação , Feminino , Humanos , Análise de Intenção de Tratamento , Masculino , Pessoa de Meia-Idade , Método Simples-Cego , Staphylococcus/isolamento & purificação , Staphylococcus aureus/isolamento & purificação
19.
Helicobacter ; 23(6): e12540, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30246287

RESUMO

BACKGROUND & AIMS: Guidelines recommend that patients with Helicobacter pylori (H. pylori)-associated peptic ulcer disease (PUD) receive H. pylori eradication therapy followed by post-treatment testing to prove eradication; however, post-treatment testing rates are suboptimal and barriers to testing are poorly understood. Our aim was to identify factors that predicted receipt of post-treatment testing. METHODS: We performed a retrospective cohort study of 152 patients with H. pylori-associated PUD diagnosed between 2007 and 2015 at a large tertiary medical center in the United States, who received standard eradication therapy and ambulatory follow-up within one year. The primary outcome of interest was receipt of post-treatment testing. Logistic regression models compared post-treatment testing rates in those diagnosed while outpatient vs inpatient, patients with vs without repeat endoscopy, and patients with vs without gastroenterology (GI) clinic follow-up. Propensity scores controlled for age, sex, race, ulcer location, and symptom persistence. RESULTS: Among 152 patients, 67 (44%) patients received post-treatment testing. There were significant differences in post-treatment testing rates in those diagnosed as outpatients vs inpatients (57% vs 33%; OR 3.87, P = 0.001) and in patients with vs without GI follow-up (62% vs 11%; OR 9.85, P < 0.0001). CONCLUSIONS: The rate of testing for eradication after treatment in patients with H. pylori- associated PUD was low. However, this was significantly improved in patients who have GI follow-up and whose diagnosis was made in the outpatient setting. Our study demonstrates a clear opportunity for quality improvement initiatives.


Assuntos
Infecções por Helicobacter/microbiologia , Úlcera Péptica/microbiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Helicobacter pylori/patogenicidade , Humanos , Modelos Logísticos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Adulto Jovem
20.
J Biopharm Stat ; 28(6): 1143-1159, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29513612

RESUMO

For approval of biosimilar products, the U.S. Food and Drug Administration (FDA) recommends a stepwise approach for obtaining the totality-of-the-evidence for assessing biosimilarirty between a proposed biosimilar product and its corresponding innovative (reference) biologic product. The stepwise approach starts with the assessment of analytical similarity of critical quality attributes (CQAs) for structural/physicochemical and functional properties in the manufacturing process of biosimilar products. For Tier 1 CQAs which are most relevant to clinical outcomes, the FDA recommends an equivalence test be performed for similarity assessment based on an equivalence acceptance criterion (EAC). While performing the equivalence test, sample size is a critical component of the equivalence test. This article focuses on the discussion of the FDA's proposal: select an appropriate sample size by adjusting EAC margin and variability ([Formula: see text]). The article provides a thorough discussion on the FDA's proposal; sample size requirement under different scenarios are briefly described and a numerical study which compares sample size requirement under various combinations of study parameters is conducted.


Assuntos
Medicamentos Biossimilares/uso terapêutico , Bioestatística/métodos , Aprovação de Drogas/estatística & dados numéricos , Estudos de Equivalência como Asunto , Tamanho da Amostra , Medicamentos Biossimilares/efeitos adversos , Simulação por Computador , Interpretação Estatística de Dados , Humanos , Modelos Estatísticos , Análise Numérica Assistida por Computador , Equivalência Terapêutica , Resultado do Tratamento , Estados Unidos , United States Food and Drug Administration
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