TBTC Study 24: Intermittent Treatment of TB With Isoniazid Resistance or Intolerance
TBTC Study 24: Intermittent Treatment of TB With Isoniazid Resistance or Intolerance
This study is a prospective, open-label, nonrandomized trial using a largely-intermittent,
 six-month tuberculosis treatment regimen among patients who will not receive isoniazid due to
 the presence of initial isoniazid resistance or intolerance. Subjects are enrolled after
 resistance or intolerance to isoniazid has been documented, and are treated for a total of
 six months (nine months if baseline chest x-ray shows cavitation and 2-month sputum culture
 is positive) with twice weekly or thrice weekly rifampin, ethambutol, and pyrazinamide.
Primary Objective:

 To evaluate the efficacy of a directly-observed, largely-intermittent, six-month regimen of
 rifampin, pyrazinamide, ethambutol among patients with culture confirmed isoniazid-resistant
 M. tuberculosis.

 Secondary Objectives:

 To describe the rate, severity and timing of toxicities and drug intolerances associated with
 this treatment regimen.

 To describe the utility of this regimen among patients who are unable to continue the
 standard 4-drug regimen due to the development of intolerance to isoniazid
Inclusion criteria:

 1. Culture-confirmed pulmonary or extrapulmonary tuberculosis due to a strain of M
 tuberculosis sensitive to rifampin, ethambutol and pyrazinamide based upon specimens
 (sputum or other pulmonary or extrapulmonary disease site specimens) collected no more
 than 8 weeks before and no more than 2 weeks after the start of the initial therapy.
 Susceptibility testing results documenting susceptibility to rifampin and ethambutol
 must be available at the time of enrollment. Susceptibility results to pyrazinamide
 may be pending at enrollment as long as pyrazinamide resistance is not known to be
 present based on prior testing. If pyrazinamide resistance is detected and confirmed
 (see Study Definitions) the patient will be withdrawn from the study therapy,
 treatment continued as recommended by the treating physician, and follow-up continued
 as per the protocol.

 2. Decision to discontinue or not use isoniazid for one or both of these following
 conditions within the first 70 days of therapy:

 -  Isoniazid resistant strain (growth in 0.2 mcg/ml or 0.1 mcg/ml of isoniazid on
 solid or liquid media, respectively)

 -  The discontinuation of isoniazid due to intolerance (as judged by the principal
 investigator - see Study Definitions)

 3. For patients enrolled after the start of therapy, documentation of adequate initial
 regimen as recommended in the CDC/ATS Treatment Guidelines (Appendix 1) is required.
 There are two means by which this requirement can be met:

 -  The standard 4-drug regimen of isoniazid, rifampin, pyrazinamide, and either
 ethambutol or streptomycin or both.

 -  The same regimen with isoniazid excluded for some or all doses in patients with
 known isoniazid intolerance or tuberculosis due to an isoniazid-resistant strain
 (i.e., the 3-drug regimen of rifampin, pyrazinamide and either ethambutol or
 streptomycin or both)

 4. A minimum duration of daily treatment as defined by one of two methods:

 -  14 daily doses within 17 days (with at least 10 of the 14 doses directly
 observed)

 -  14 directly observed doses within 23 days

 Following the minimum daily phase of therapy, adequate pre-enrollment treatment is
 defined as directly administered therapy given daily, twice weekly, or thrice weekly
 using CDC/ATS guidelines. Documenting pre-enrollment therapy is accomplished by
 hospital medical records and/or clinic entries of DOT.

 5. Age: 18 years or older

 6. Documentation of negative test for human immunodeficiency virus (HIV) infection.
 Documentation means written copies of HIV laboratory test results. A negative HIV test
 result within the 6 months prior to enrollment is acceptable.

 7. Documentation of study baseline laboratory parameters. Baseline laboratory parameters
 obtained no more than 2 weeks prior to enrollment and must be within the following
 limits:

 1. . Amino aspartate transferase (AST) activity less than 3 times upper limit of
 normal;

 2. . Total bilirubin level less than 2.5 times upper limit of normal;

 3. . Creatinine level less than 2 times upper limit of normal;

 4. . Hemoglobin level of at least 7.0 g/dL;

 5. . Platelet count of at least 50,000 mm3

 8. Karnofsky score of at least 60. See Appendix 6 for Karnofsky scoring system.

 9. A negative pregnancy test within the past 14 days for women with child-bearing
 potential, and a willingness to practice an adequate (preferably barrier) method of
 birth control. In addition, women with child-bearing potential should be offered
 information concerning sources of contraceptive counseling and services.

 10. Informed consent signed by patient and investigator documenting the willingness to use
 the 3-drug, intermittent regimen is required, in accordance with state law and local
 IRB requirements. Patients who are unable to provide informed consent due to an
 inability to comprehend English may be enrolled by providing informed consent by
 either of two means:

 -  the use of a translator to provide a verbal translation of the IRB-approved
 English version of the consent form; the translator will sign the English form
 attesting the translation and the patient will sign the IRB-approved translation
 of the short form

 -  the use of a translated consent document, approved by the IRB, that is in the
 patient's native language.

 Exclusion criteria

 1. Patients with known treatment-limiting reaction to rifamycins, pyrazinamide, or
 ethambutol.

 2. Diagnosis of silicotuberculosis or tuberculosis of the central nervous system

 3. Patients who, during initial therapy with CDC/ATS recommended therapy with isoniazid,
 rifampin and pyrazinamide plus either ethambutol or streptomycin or both, have
 received greater than 21 days of treatment with additional drugs with known
 antituberculosis activity - see Concomitant Medications During Study Phase Therapy.

 4. Patients with isoniazid intolerance or isoniazid-resistant tuberculosis who during
 pre-enrollment therapy have missed a total of two weeks of directly observed therapy
 doses due to non-compliance.

 5. Patients enrolled due to isoniazid intolerance who during pre-enrollment therapy have
 missed a total of over 4 weeks of directly observed therapy doses for management of
 drug intolerance.