Phase IIb (8-week) studies

D A MitchisonD A MitchisonSt George’s, University of LondonSt 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

ScreeningNewly diagnosed smear +ve

412

Willing to collaborate226 Excluded

11

HRZEControl

54

HRZOOflo55

HRZGGati54

HRZMMoxi

548-weeks

RHcontinuation 4 months

Summary of recruitment

0 56

14 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)

2 7 14 21 28

Comparative bactericidal assessments

35 42 49

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

0 2 7 14 21 28 35 42 49 56

02

46

810

Days on therapy

Log 1

0CFU

/ m

l spu

tum

210

206

205

194

173127

105 60 3018

Summary of SSCC results

Limit of detection

Days on therapy 0 10 20 30 40 50

02

46

810

Log 1

0 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

0.000.10

0.200.300.400.50

0.600.700.80

0.901.00

HRZE HRZO HRZG HRZM

Prop

ortio

n po

sitiv

e

Proportion positive at two months

49.058.5

43.446.9

Chi-square test

2 (3)=2.63

p= 0.451

0 10 20 30 40 50 60

0.0

0.2

0.4

0.6

0.8

1.0

Days on therapy

Pro

babi

lity

of s

putu

m c

onve

rsio

n

HRZEHRZOHRZGHRZM

Survival analysis

Log rank test

2 (3)=10.69

p= 0.0136

Hazard Ratio for culture conversion*

z-test

HRZO 0.83 -0.85 (p=0.393)

HRZG 1.25 1.07 (p=0.284)

HRZM 1.47 1.86 (p=0.063)

Survival analysis

* vs. HRZE

0 10 20 30 40 50

02

46

810

Days on therapy

Log 1

0CFU

/ m

l spu

tum

MonoexponentialBiexponential

Regression modelling of serial sputum colony counts

Limit of detection

ModelLog

likelihoodAkaike

Information Criterion

Likelihood Ratio Test

(p value)

Monoexponential -2141.314 4288.628 -

Biexponential -1967.841 3945.682 346.9456 (<0.0001)

Biexponential + Random effects

-1582.434 3182.867 754.500 (<0.0001)

Biexponential + Random effects +

Treatment

-1577.804 3179.608 9.259 (0.026)

Model fitting sequence

(early, 0-7 days)

Polynomial / Spline Mixed Effects

Summary regressions

b0-2 b0-7

Non-linear Mixed Effects

HRZM 0.220 0.615 0.340 0.742 HRZG 0.177 0.553 0.304 0.723 HRZO 0.099 0.421 0.254 0.481 HRZE 0.096 0.459 0.250 0.586 p-value **

** * **

** **

** **

β (late,

7-56 days)

b7-28

b7-56

HRZM 0.157 0.138 0.131 0.128 HRZG 0.153 0.138 0.134 0.120 HRZO 0.148 0.113 0.111 0.105 HRZE 0.139 0.125 0.113 0.105 p-value

* **

**

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

0 10 20 30 40 50

01

23

45

67

Days on therapy

Log 1

0CFU

/ m

l spu

tum

HRZE = -0.586 HRZO = -0.481 HRZG = -0.723 HRZM = -0.742

HRZE = -0.104 HRZO = -0.093 HRZG = -0.123 HRZM = -0.121

Limit of detection

Estimated treatment effects

Forecasting duration of therapy by effect size

0 50 100-50-100

-17.8 9.2

-7.0 23.8

1.4 35.2

9.0 103.1

% Change in versus control

HRZO

HRZG

HRZM

(SHRZ)

-5.3

6.5

17.3

48.7

Approximate 95% confidence intervals derived from NLME

model

0 50 100 150 200

-20

-15

-10

-50

510

Days on therapyLo

g 10C

FU /

ml s

putu

m

HRZEHRZQ

Forecasting duration of therapy by extrapolation

138 days

~100 days ?

Biexponential model Triexponential model

0 50 100 150 200

-20

-15

-10

-50

510

Days on therapy

Log 1

0CFU

/ m

l spu

tum

HRZEHRZQ

Cost assessment (US$)

Patientsper arm Cost

Standard 120 120 x (8,000-250) = 930,000

SSCC 50 50 x 8,000= 400,000

Duration of study: 12 monthsNumber 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.