A new trial design to accelerate tuberculosis drug development : the Phase IIC Selection Trial with Extended Post-treatment follow-up (STEP)
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Background The standard 6-month four-drug regimen for the treatment of drug-sensitive tuberculosis has remained unchanged for decades and is inadequate to control the epidemic. Shorter, simpler regimens are urgently needed to defeat what is now the world’s greatest infectious disease killer. Methods We describe the Phase IIC Selection Trial with Extended Post-treatment follow-up (STEP) as a novel hybrid phase II/III trial design to accelerate regimen development. In the Phase IIC STEP trial, the experimental regimen is given for the duration for which it will be studied in phase III (presently 3 or 4 months) and patients are followed for clinical outcomes of treatment failure and relapse for a total of 12 months from randomisation. Operating characteristics of the trial design are explored assuming a classical frequentist framework as well as a Bayesian framework with flat and sceptical priors. A simulation study is conducted using data from the RIFAQUIN phase III trial to illustrate how such a design could be used in practice. Results With 80 patients per arm, and two (2.5 %) unfavourable outcomes in the STEP trial, there is a probability of 0.99 that the proportion of unfavourable outcomes in a potential phase III trial would be less than 12 % and a probability of 0.91 that the proportion of unfavourable outcomes would be less than 8 %. With six (7.5 %) unfavourable outcomes, there is a probability of 0.82 that the proportion of unfavourable outcomes in a potential phase III trial would be less than 12 % and a probability of 0.41 that it would be less than 8 %. Simulations using data from the RIFAQUIN trial show that a STEP trial with 80 patients per arm would have correctly shown that the Inferior Regimen should not proceed to phase III and would have had a high chance (0.88) of either showing that the Successful Regimen could proceed to phase III or that it might require further optimisation. Conclusions Collection of definitive clinical outcome data in a relatively small number of participants over only 12 months provides valuable information about the likelihood of success in a future phase III trial. We strongly believe that the STEP trial design described herein is an important tool that would allow for more informed decision-making and accelerate regimen development.
Phillips , P P J , Dooley , K E , Gillespie , S H , Heinrich , N , Stout , J E , Nahid , P , Diacon , A H , Aarnoutse , R E , Kibiki , G S , Boeree , M J & Hoelscher , M 2016 , ' A new trial design to accelerate tuberculosis drug development : the Phase IIC Selection Trial with Extended Post-treatment follow-up (STEP) ' BMC Medicine , vol 14 , 51 , pp. 1-11 . DOI: 10.1186/s12916-016-0597-3
© 2016 Phillips et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License, which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver applies to the data made available in this article, unless otherwise stated.
DescriptionThe PanACEA consortium was funded by the European Developing Country Partnership through grants IP.2007.32011.011, IP.2007.32011.012, and IP.2007.32011.013. PN is supported by the NIAID of the National Institutes of Health (R01AI104589) and the TBTC. KED is supported by NIAID/NID (R01AI111992) and the TBTC.
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