Evaluation of SARS-CoV-2 RNA Rebound After Nirmatrelvir/Ritonavir Treatment in Randomized, Double-Blind, Placebo-Controlled Trials - United States and International Sites, 2021-2022.

Rebound of SARS-CoV-2 shedding or COVID-19 signs and symptoms has been described after treatment with nirmatrelvir/ritonavir (Paxlovid). The direct association of nirmatrelvir/ritonavir to COVID-19 rebound remains unclear because most reports are based on individual cases or nonrandomized studies. Viral RNA shedding data from two phase 2/3, randomized, double-blind, placebo-controlled clinical trials of nirmatrelvir/ritonavir (Evaluation of Protease Inhibition for COVID-19 in High-Risk Patients [EPIC-HR] and Evaluation of Protease Inhibition for COVID-19 in Standard-Risk Patients [EPIC-SR]) were analyzed to investigate the role of nirmatrelvir/ritonavir treatment in COVID-19 rebound. Rates of rebound of SARS-CoV-2 RNA shedding, identified based on an increase in nasopharyngeal viral RNA levels from day 5 (end-of-treatment) to day 10 or day 14, were similar between nirmatrelvir/ritonavir and placebo recipients. Among subjects with a virologic response through day 5, viral RNA rebound occurred in 6.4%-8.4% of nirmatrelvir/ritonavir recipients and 5.9%-6.5% of placebo recipients across EPIC-HR and the 2021/pre-Omicron and 2022/Omicron enrollment periods of EPIC-SR. Viral RNA rebound after nirmatrelvir/ritonavir treatment was not associated with COVID-19-related hospitalization or death. Data from randomized trials demonstrated that SARS-CoV-2 rebound can occur with or without antiviral treatment, supporting the Food and Drug Administration's determination of safety and efficacy of nirmatrelvir/ritonavir in eligible patients at high risk for severe COVID-19.

Benefit-risk assessment for brincidofovir for the treatment of smallpox: U.S. Food and Drug Administration's Evaluation.

The development and approval of brincidofovir for the treatment of smallpox, a disease that was eradicated from the world over 40 years ago, has resulted in the second antiviral approved via the Medical Countermeasure Initiative (MCMi) to combat this disease. Approval of brincidofovir required a unique regulatory approach based on the FDA Animal Rule, and development was supported by many years of research and collaboration among academic investigators, the pharmaceutical industry and multiple government agencies. This article summarizes the FDA regulatory pathway and describes the challenges involved.

Sustained virological response rates with direct-acting antivirals in black subjects with HCV genotype 1 infection: systematic analysis of clinical trials.

OBJECTIVES: Under representation of black subjects in trials of hepatitis C virus (HCV) direct-acting antivirals (DAAs) complicates assessment of differential outcomes for black individuals vs non-black individuals. HCV trials submitted to the Food and Drug Administration (2013-2017) to support approval or to expand an indication of 12-week interferon-free DAA regimens with or without ribavirin to treat HCV genotype 1 (GT1) infection were pooled to explore efficacy comparisons by ethnicity. METHODS: Twenty-six trials were pooled and included 2869 individuals with HCV GT1 alone and 742 individuals with both HCV GT1 and HIV. RESULTS: Of the 2869 HCV GT1-mono-infected subjects, 408 (14.2%) were black. Sustained virological response assessed 12 weeks following cessation of treatment (SVR12) was 92%-100% in black individuals and 87.5%-100.0% in non-black individuals. In pooled analyses, SVR12 was numerically similar between black and non-black subjects (97.1% vs 97.3%). Baseline characteristics did not affect SVR12 for the two groups. Of the 742 subjects with both HCV GT1 and HIV, 243 (32.7%) were black: SVR12 was 89.5%-100% in black individuals and 94.4%-100% in non-black individuals. In pooled analyses for HCV GT1/HIV co-infection, black individuals had a 4% (95% confidence interval -7.7% to 0.3%) lower SVR12 than non-black individuals (93.4% vs 97.0%). This difference was driven by ION-4 in which study SVR12 was approximately 10% lower for black than for non-black individuals (89.5% vs 99.1%). Baseline characteristics did not affect SVR12 for the two groups. CONCLUSION: No notable SVR12 differences were seen in between black and non-black individuals with HCV GT1 alone. Although a numerical difference was observed between black and non-black individuals with both HCV GT1 and HIV, this finding was driven by results from a single trial and may be due to reasons other than ethnicity: 19 subgroup analyses showed baseline characteristics did not affect SVR12 for black and non-black individuals with both HCV GT1 and HIV.

Methods for efficacy evaluations of antibacterial treatments in multiple body-site infection trials.

Unmet medical need exists for serious bacterial diseases caused by multidrug-resistant infections, necessitating an urgent need for newer therapies with greater treatment benefits to patients. For meeting this need, the usual approach has been to conduct separate clinical trials, each trial targeting infection at a single body-site, e.g., for respiratory tract, intra-abdominal site, urinary tract, or blood. However, for the unmet medical need situations, this approach seems inefficient for developing antibacterial drugs with activity against single species or against multiple species of bacteria for a broader indication. Instead, a streamlined clinical development program for such situations can benefit by considering multiple body-site infection trials. Such trials would enroll patients with infections at different body-sites, but with similar severity and comorbidity for avoiding potential treatment effect heterogeneity. Such trials, when properly designed and conducted, can be informative and can save time and resources in drug development. Goals for such trials would be to first demonstrate that there is evidence of an overall treatment effect, and then to show that the treatment effects at individual body-sites reveal consistency in contributing to the overall treatment effect, or to identify a subset of body-sites for which greater treatment effect can be supported by a specified statistical decision criterion. For this, we propose here an information-based procedure for the demonstration of treatment effect overall across all body-sites, or for a subset of body-sites, on considering two types of error rates of falsely concluding treatment effect.

Consistency ensured test strategies for supportive evidence of treatment efficacy in noninferiority clinical trials.

Noninferiority (NI) clinical trials are designed to demonstrate that a new treatment is not unacceptably worse than an active control on a clinically meaningful endpoint. While such an endpoint can be of any type, the focus of this manuscript is on the binary-type endpoint. Examples of this endpoint can be clinical cure endpoint for patients with bacterial diseases or based on a pre-specified virological threshold for viral diseases. However, in addition to assessing such a binary endpoint for the NI comparison, the trial may also evaluate a second clinically relevant endpoint for providing additional support to the evidence of the designated primary endpoint. Specifically, if the trial is successful in demonstrating statistical significance on the first endpoint, then observing at least a positive trend in efficacy on the second endpoint may provide additional supportive evidence of efficacy. The second endpoint can be a time-to-event type endpoint, such as time-to-symptom resolution (TSR) or time to all-cause mortality for infectious disease trials, time-to-wound closure for wound healing trials, or other endpoints. We propose two consistency ensured test strategies for the two hypotheses of a trial, one associated with the binary endpoint and the other with the second endpoint, both with the objective of drawing inference regarding the efficacy of the new treatment based on findings from testing the two hypotheses. A key feature of these test strategies is that basically it does not require multiplicity adjustment of the significance levels. We conclude with general discussion of the testing methods and possible applications to unmet medical need trials.

Hierarchical nested trial design (HNTD) for demonstrating treatment efficacy of new antibacterial drugs in patient populations with emerging bacterial resistance.

In the last decade or so, pharmaceutical drug development activities in the area of new antibacterial drugs for treating serious bacterial diseases have declined, and at the same time, there are worries that the increased prevalence of antibiotic-resistant bacterial infections, especially the increase in drug-resistant Gram-negative infections, limits available treatment options . A recent CDC report, 'Antibiotic Resistance Threats in the United States', indicates that antimicrobial resistance is one of our most serious health threats. However, recently, new ideas have been proposed to change this situation. An idea proposed in this regard is to conduct randomized clinical trials in which some patients, on the basis of a diagnostic test, may show presence of bacterial pathogens that are resistant to the control treatment, whereas remaining patients would show pathogens that are susceptible to the control. The control treatment in such trials can be the standard of care or the best available therapy approved for the disease. Patients in the control arm with resistant pathogens can have the option for rescue therapies if their clinical signs and symptoms worsen. A statistical proposal for such patient populations is to use a hierarchical noninferiority-superiority nested trial design that is informative and allows for treatment-to-control comparisons for the two subpopulations without any statistical penalty. This design can achieve in the same trial dual objectives: (i) to show that the new drug is effective for patients with susceptible pathogens on the basis of a noninferiority test and (ii) to show that it is superior to the control in patients with resistant pathogens. This paper addresses statistical considerations and methods for achieving these two objectives for this design. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Robust extraction of covariate information to improve estimation efficiency in randomized trials.

In randomized trials, investigators typically rely upon an unadjusted estimate of the mean outcome within each treatment arm to draw causal inferences. Statisticians have underscored the gain in efficiency that can be achieved from covariate adjustment in randomized trials with a focus on problems involving linear models. Despite recent theoretical advances, there has been a reluctance to adjust for covariates based on two primary reasons: (i) covariate-adjusted estimates based on conditional logistic regression models have been shown to be less precise and (ii) concern over the opportunity to manipulate the model selection process for covariate adjustments to obtain favorable results. In this paper, we address these two issues and summarize recent theoretical results on which is based a proposed general methodology for covariate adjustment under the framework of targeted maximum likelihood estimation in trials with two arms where the probability of treatment is 50%. The proposed methodology provides an estimate of the true causal parameter of interest representing the population-level treatment effect. It is compared with the estimates based on conditional logistic modeling, which only provide estimates of subgroup-level treatment effects rather than marginal (unconditional) treatment effects. We provide a clear criterion for determining whether a gain in efficiency can be achieved with covariate adjustment over the unadjusted method. We illustrate our strategy using a resampled clinical trial dataset from a placebo controlled phase 4 study. Results demonstrate that gains in efficiency can be achieved even with binary outcomes through covariate adjustment leading to increased statistical power.

Registration trials of antibacterial drugs for the treatment of nosocomial pneumonia.

Since 1989, 12 registration trials have been submitted to the US Food and Drug Administration to support the clinical efficacy of 8 antibacterial drugs for the treatment of nosocomial pneumonia. Six trials used noninferiority designs, whereas the others were equivalence trials or lacked a prespecified hypothesis. Patients with nosocomial pneumonia and ventilator-associated pneumonia were frequently enrolled in the same clinical trials. Enrolled patients were predominantly male and had mean Acute Physiology and Chronic Health Evaluation II scores of 12-18. The investigator's assessment of clinical response was the primary end point, which was usually measured 7-14 days after study drug completion. Clinical cure rates among the intent-to-treat population for nosocomial pneumonia and ventilator-associated pneumonia ranged from 37% to 69% and 25% to 58%, respectively. All-cause mortality ranged from 8% to 28%. Pseudomonas aeruginosa, Acinetobacter species, and methicillin-resistant Staphylococcus aureus were common bacterial pathogens. The design, implementation, and limitations of the clinical trials and implications for future clinical research are discussed.

Meta-analysis of a possible signal of increased mortality associated with cefepime use.

BACKGROUND: On the basis of meta-analyses, concern has been raised regarding a possible signal of increased mortality associated with the use of cefepime versus other beta-lactam antibiotics. To further investigate this possible signal, we accessed findings and data from published and unpublished cefepime clinical trials. METHODS: We performed meta-analyses using trial- and patient-level data from comparative trials. Trial-level analyses were performed using summary data from all patients in the trials, and patient-level analyses were performed on trials for which patient-level data were available. Thirty-day, all-cause mortality was analyzed using the Mantel-Haenszel adjusted risk difference (ARD) method. RESULTS: The trial-level meta-analysis was based on 88 trials (9467 cefepime patients and 8288 comparator patients). The 30-day, all-cause mortality rates were 6.21% (588/9467) for the cefepime patients and 6.00% (497/8288) for comparator patients (ARD per 1000 population, 5.38; 95% confidence interval [CI], -1.53 to 12.28). In the patient-level analysis (35 trials, 5058 cefepime patients, and 3976 comparator patients), 30-day, all-cause mortality rates were 5.63% (285/5058) for cefepime patients and 5.68% (226/3976) for comparator patients (ARD per 1000 population, 4.83; 95% CI, -4.72 to 14.38). A sensitivity analysis based solely on the 24 febrile neutropenia trials did not show a statistically significant increase in mortality with cefepime use (ARD per 1000 population, 9.67; 95% CI, -2.87 to 22.21). CONCLUSIONS: In both trial-level and patient-level meta-analyses, we did not identify a statistically significant increase in mortality among cefepime-treated patients, compared with those treated with other antibacterials.

Female condom and male condom failure among women at high risk of sexually transmitted diseases.

OBJECTIVE: The objective of this study was to study the frequency and determinants of breakage and slippage during female and male condom use. GOAL: The goal of this study was to determine condom breakage and slippage rate. STUDY: We conducted a 6-month prospective follow-up study of women attending 2 sexually transmitted disease clinics. Breakage and slippage rates were computed. Logistic regression was used to evaluate baseline characteristics and time-dependent behaviors. RESULTS: A total of 869 women used condoms in 20,148 acts of intercourse. Breakage was less common for female condoms (0.1%; 95% confidence interval [CI], 0.05-0.21) than for male condoms (3.1%; 95% CI, 2.80-3.42). Slippage was more common for female condoms (5.6%; 95% CI, 5.10-6.13) than for male condoms (1.1%; 95% CI, 0.90-1.28). Rates significantly decreased with use and increased with number of previous failures. From first use to >15 uses, combined failure rate fell from 20% to 1.2% for female condoms (P < 0.0001) and 9% to 2.3% for male condoms (P < 0.01). CONCLUSIONS: Both condoms may provide good protection against sexually transmitted diseases. Experience determines success with either condom.