Overview of recent studies of community-acquired pneumonia

Concordance of early and late endpoints for community-acquired bacterial pneumonia trials

BACKGROUND

While there are ongoing regulatory convergence efforts, differences remain in primary endpoints recommended for community-acquired bacterial pneumonia (CABP) trials. The US Food and Drug Administration recommends assessing CABP symptom resolution at an early time point (3-5 days after randomization). Other regulatory agencies recommend assessing overall clinical response at a later time point (5-10 days after therapy ends).

METHODS

We analyzed participant-level data from six recent CABP trials submitted to the FDA (n=4,645 participants) to evaluate concordance between early and late endpoint outcomes. We used multivariate logistic regression to identify factors associated with discordance.

RESULTS

Early and late endpoint outcomes were concordant for 85.6% of participants. The proportions of early endpoint responders that ultimately failed and early endpoint non-responders that ultimately succeeded were similar (6.0% vs 8.4%, respectively). Early endpoint response was highly predictive of late endpoint success (positive predictive value 92.9%). Multivariate logistic regression identified early endpoint responders/late endpoint failures as less likely to be obese and more likely to be infected with Chlamydophila pneumoniae or Staphylococcus aureus, have received antibacterial drug therapy prior to randomization, and have severe chest pain at baseline. The most common investigator-provided reasons for failure among early endpoint responders/late endpoint failures were receipt of non-study antibacterial drug therapy and loss to follow-up.

CONCLUSION

Early and late endpoint outcomes were highly concordant. These data may be useful in the continuing efforts to reach international regulatory convergence on CABP clinical trial design recommendations.

A simulation study evaluating bio-creep risk in serial non-inferiority clinical trials for preservation of effect

In non-inferiority trials, acceptable efficacy of an experimental treatment is established by ruling out some defined level of reduced effect relative to an effective active control standard. Serial use of non-inferiority trials may lead to newly approved therapies that provide meaningfully reduced levels of benefit; this phenomenon is called bio-creep. Simulations were designed to facilitate understanding of bio-creep risk when approval of an experimental treatment with efficacy less than some proportion of the effect of the active control treatment would constitute harm, such as when new antibiotics that are meaningfully less effective than the most effective current antibiotic would be used for treatment of Community-Acquired Bacterial Pneumonia. In this setting, risk of approval of insufficiently effective therapies may be great, even when the standard treatment effect satisfies constancy across trials. Modifiable factors contributing to this manifestation of bio-creep included the active control selection method, the non-inferiority margin, and bias in the active control effect estimate. Therefore, when non-inferiority testing is performed, the best available treatment should be used as the standard, and margins should be based on the estimated effect of this control, accounting for the variability and for likely sources of bias in this estimate, and addressing the importance of preservation of some portion of the standard's effect.

Cethromycin versus clarithromycin for community-acquired pneumonia: comparative efficacy and safety outcomes from two double-blinded, randomized, parallel-group, multicenter, multinational noninferiority studies

Community-acquired pneumonia (CAP) continues to be a major health challenge in the United States and globally. Factors such as overprescribing of antibiotics and noncompliance with dosing regimens have added to the growing antibacterial resistance problem. In addition, several agents available for the treatment of CAP have been associated with serious side effects. Cethromycin is a new ketolide antibiotic that may provide prescribing physicians with an additional agent to supplement a continually limited armamentarium. Two global phase III noninferiority studies (CL05-001 and CL06-001) to evaluate cethromycin safety and efficacy were designed and conducted in patients with mild to moderate CAP. Study CL05-001 demonstrated an 83.1% clinical cure rate in the cethromycin group compared with 81.1% in the clarithromycin group (95% confidence interval [CI], -4.8%, +8.9%) in the intent to treat (ITT) population and a 94.0% cethromycin clinical cure rate compared with a 93.8% clarithromycin cure rate (95% CI, -4.5%, +5.1%) in the per protocol clinical (PPc) population. Study CL06-001 achieved an 82.9% cethromycin clinical cure rate in the ITT population compared with an 88.5% clarithromycin cure rate (95% CI, -11.9%, +0.6%), whereas the clinical cure rate in the PPc population was 91.5% in cethromycin group compared with 95.9% in clarithromycin group (95% CI, -9.1%, +0.3%). Both studies met the primary endpoints for clinical cure rate based on predefined, sliding-scale noninferiority design. Therefore, in comparison with clarithromycin, these two noninferiority studies demonstrated the efficacy and safety of cethromycin, with encouraging findings of efficacy in subjects with Streptococcus pneumoniae bacteremia. No clinically significant adverse events were observed during the studies. Cethromycin may be a potential oral therapy for the outpatient treatment of CAP.

Publication of noninferiority clinical trials: changes over a 20-year interval

STUDY OBJECTIVES

The primary objective was to evaluate the change in publication rate of noninferiority trials over a 20-year interval (1989-2009). Secondary objectives were to analyze the frequency of noninferiority trials by therapeutic category, the frequency of noninferiority trial publication by journal, the impact factors of the publishing journals, any potential special advantages of the study drug over the control, the funding sources of the trials, pharmaceutical industry affiliation of the authors, and the use of ghostwriters in the creation of manuscripts.

DESIGN

Retrospective literature review of 583 articles.

DATA SOURCES

PubMed (January 1989-December 2009) and EMBASE (first quarter 1989-fourth quarter 2009) databases.

MEASUREMENTS AND MAIN RESULTS

A total of 583 articles of the results of randomized controlled clinical trials with a noninferiority study design that evaluated drug therapies, published in English, between 1989 and 2009, were included in the analysis. A consistent increase was noted in their yearly publication rates, with no trials published in 1989 versus 133 in 2009. One hundred twenty-six articles (21.6%) were in the therapeutic category of infectious diseases, followed by 78 (13.4%) in cardiology. Among the journals identified, The New England Journal of Medicine had the highest publication rate of trials with a noninferiority design, with 29 (5.0%) of the identified trials published in this journal. The median impact factor of the journals publishing noninferiority trials was 4.807 (interquartile range 3.064-7.5). The most common advantage of the study drug over the control was reduced duration of treatment or reduced pill burden (80 studies [22.9%]). A total of 425 trials (72.9%) listed the pharmaceutical industry as the only funding source. Among 369 trials with authors employed by the pharmaceutical industry, 101 (17.3%) disclosed an acknowledgment to an individual, other than those listed as authors, who contributed to writing the manuscript and who was affiliated with a medical information company and/or a pharmaceutical company (i.e., potential ghostwriters).

CONCLUSION

The publication of noninferiority trials increased during the 20 years from 1989 until 2009, particularly in the therapeutic areas of infectious diseases and cardiology. Because of this growth, clinicians and researchers need to be familiar with the caveats of the noninferiority study design to appropriately interpret and design these clinical studies.

Design of clinical trials of antibacterial agents for community-acquired bacterial pneumonia

Standards for the conduct of clinical trials of antibacterial agents for community-acquired bacterial pneumonia (CABP) have changed dramatically in recent years. A draft guidance from the US FDA on the conduct of such trials was issued in March 2009. However, the guidance has already faced substantial criticism during the open public comment period, resulting in uncertainty regarding the appropriate design of such studies from a regulatory perspective. Controversies regarding the magnitude of the treatment effect associated with antibacterial therapy versus placebo/no therapy, the appropriate timing, nature and noninferiority margin for the primary efficacy end point, and other clinical and statistical issues have complicated efforts to reach consensus on appropriate trial design of antibacterial therapy for CABP. It is critical that studies of new drugs for CABP are designed to ensure that they are feasible to conduct and that their results are scientifically valid, statistically rigorous and clinically meaningful. Based on 3 years of active dialog between clinical, statistical, and regulatory experts, this article proposes an approach to enable a balance of clinical trial feasibility with appropriate scientific, statistical and clinical rigor.

Historical and regulatory perspectives on the treatment effect of antibacterial drugs for community-acquired pneumonia

A noninferiority margin based on the treatment effect of antibacterial drugs is required for noninferiority studies of community-acquired pneumonia. A quantitative estimate of treatment effect is generally determined from placebo-controlled trials, but, since the mid-to-late 1930s, no studies have compared outcomes for patients who received placebo (or no specific therapy) with those for patients who received an antibacterial drug for treatment of community-acquired pneumonia. In this article, early controlled studies, as well as observational data, are reviewed, and the beneficial effect of antibacterial drugs on mortality rates among patients with pneumococcal pneumonia is demonstrated. However, because these data were obtained in the early 20th century, several important factors have changed, including patient populations, the etiological agents of pneumonia, and medical standards of care. Thus, the applicability of these studies to the determination of a noninferiority margin for contemporary trials for community-acquired pneumonia remains in question.