Phase IIb (8-week) studies D A Mitchison St George’s, University of London

Comparison of the bactericidal activities of the Fluoroquinolones: Gatifloxacin, Moxifloxacin and Ofloxacin, substituted for Ethambutol in the 2- Month initial phase of standard treatment Oflotub phase 2 surrogate marker study South African Medical Research Council, Durban Dr R Rustomjee; Dr F Sirgel; Prof W Sturm; Dr B Fourie and staff Prof D Mitchison; Dr C Lienhardt (Co-ordinator); Dr C Merle (Trial Monitor) Supported by European Commission WHO TDR

Design   Open label Phase II Randomised Controlled Trial Aims   Compare three fluoroquinolones substituted for ethambutol in 2HRZE initial phases using serial sputum colony counting (SSCC)   Compare the use of different surrogate endpoints in Phase II studies

Screening Newly diagnosed smear +ve 412 Willing to collaborate 226 Excluded 11 HRZE Control 54 HRZO Oflo 55 HRZG Gati 54 HRZM Moxi 54 8-weeks RH continuation 4 months Summary of recruitment

hour sputum collection Sputum colony counts on selective 7H11 medium without decontamination at 10 time points during initial 8-week phase Standard 7H11 culture + Liquid culture (MGIT) Comparative bactericidal assessments Standard 7H11 culture Standard 7H11 culture + indirect susceptibility tests

Analysis Jonathan Levin (Durban):   Proportions +ve at 2 months   Survival analysis using SSCC   Polynomial / spline mixed effects modelling of SSCC Geraint Davies (Bangkok):   Non-linear mixed effects modelling of SSCC Denny Mitchison (London):   Summary regression estimates on SSCC

Summary of SSCC results Limit of detection

Days on therapy Log 10 CFU /ml Summary statistics & regression models of colony counts Proportion positive at 2 months Survival analysis & time to conversion Relapse Analytical approaches to Phase II surrogate endpoint studies Limit of detection

Proportion positive at two months Chi-square test  2 (3)=2.63 p= 0.451

Survival analysis Log rank test  2 (3)=10.69 p=

Hazard Ratio for culture conversion* z-test HRZO (p=0.393) HRZG (p=0.284) HRZM (p=0.063) Survival analysis * vs. HRZE

Regression modelling of serial sputum colony counts Limit of detection

Model Log likelihood Akaike Information Criterion Likelihood Ratio Test (p value) Monoexponential Biexponential (<0.0001) Biexponential + Random effects (<0.0001) Biexponential + Random effects + Treatment (0.026) Model fitting sequence

Regression estimates Signs of coefficients reversed ) * <0.05 M vs.E **<0.01 M vs.E * <0.05 M&G vs. E&O **<0.01 M&G vs. E&O

Limit of detection Estimated treatment effects

Forecasting duration of therapy by effect size % Change in versus control HRZO HRZG HRZM (SHRZ) Approximate 95% confidence intervals derived from NLME model

Forecasting duration of therapy by extrapolation 138 days ~100 days ? Biexponential model Triexponential model

Cost assessment (US$) Patients per armCost Standard x (8, ) = 930,000 SSCC5050 x 8,000 = 400,000 Duration of study: 12 months Number of sputum specimens: 2100 Technicians employed: 3

Conclusions 1   When substituted for Ethambutol, both Moxifloxacin and Gatifloxacin killed significantly faster in the early and late phases than control   Ofloxacin substitution had no significant effect   The observed increases in late phase killing with these regimens support a probable reduction in the duration of therapy of at least one and possibly two months

Conclusions 2   Several different methods of analysis detected a treatment effect but culture conversion at 8 weeks did not   It is important that methods discriminate between the early and late phases of killing and avoid overestimating “sterilizing activity”   Non-linear mixed effects modelling appears to be both an informative and sensitive approach

Conclusions 3   Modelling using SSCC data has significant advantages over methods based only on culture conversion   SSCC is also cheaper as it requires a smaller sample size   SSCC modelling should be the basis of future phase II studies aiming to evaluate new regimens suggested by mouse studies.