Scientific Publications by FDA Staff

Stat Med 2014 Nov 9;33(25):4321-36

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

Huque MF, Valappil T, Soon GG

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.