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Recent Advances in Multidrug-Resistant TB
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Recent Advances in Multidrug-Resistant TB
Faculty and Disclosure Information
Richard E. Chaisson, MD
Professor of Medicine,
Epidemiology and International
Health
Johns Hopkins University
Director, Johns Hopkins Center
for AIDS Research and Center
for Tuberculosis Research
Baltimore, Maryland
Richard E. Chaisson, MD, has disclosed that his spouse has
ownership interest in Merck.
Maunank Shah, MD, has no significant financial relationships to
disclose.
Maunank Shah, MD
Assistant Professor
Department of Infectious Disease
Johns Hopkins University
Medical Director
Tuberculosis Program
Baltimore City Health Department
Baltimore, Maryland
5. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Tuberculosis Drug Resistance: Definitions
Acquired drug resistance
– Selection of resistant mutants by inadequate treatment
Primary drug resistance
– Disease caused by an organism that was resistant when
infection was acquired
Multidrug-resistant TB
– Resistance to at least isoniazid and rifampin (and other
rifamycins)
Extensively drug–resistant TB
– MDR-TB plus resistance to fluoroquinolones and an
injectable agent (amikacin, kanamycin, capreomycin)
6. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Drug-Resistant TB: MDR and XDR
Drug-resistant TB first arises from improper treatment
– Wrong selection of drugs by doctors or poor adherence to treatment by
patients results in selection of naturally occurring mutants with innate
resistance
Patients with acquired drug-resistant TB can spread infection to
others, causing primary resistance in their contacts
In many countries, transmission of drug-resistant TB is now more
common than acquired resistance[1]
The key prevention strategies for drug-resistant TB are:
– Avoid creating new cases by treating TB properly and thoroughly
– Prevent transmission of infection through early and proper diagnosis and
infection control
1. WHO. 2013. Surveillance of drug resistance in tuberculosis.
7. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
MDR-TB: Epidemiology
In 2012, an estimated 450,000 new cases of MDR-TB emerged
globally[1]
Among all new cases of TB, 3.6% are estimated to have MDR-
TB[1]
An estimated 20% of persons with previously treated TB have
MDR-TB[1,2]
More than one half of the new MDR-TB cases occur in China,
India, and the Russian Federation[1]
Mortality in MDR-TB patients usually exceeds 10%[3]
In 2012, MDR-TB caused an estimated 170,000 deaths[1]
1. WHO. 2013. Update on MDR-TB. 2. CDC. MMWR Morb Mortal Wkly Rep. 2013;62:1-12.
3. Wells CD. Curr Infect Dis Rep. 2010;12:192-197.
9. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
MDR-TB Among Previously Treated TB
Cases, 1994-2013
WHO. 2013. Surveillance of drug resistance in tuberculosis.
11. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Diagnosis of MDR-TB
Gold-standard test: Culture of patient specimen (sputum) to assess inhibition of M
tuberculosis growth in the presence of antibiotics (phenotypic assay)
Solid-media assays: Result may not be available for 3-6 wks
Automated liquid culture systems: Faster and more sensitive than solid-media
cultures; results available in 1-2 wks
Rapid molecular tests can identify genotypic resistance in 1-2 days
– Xpert TB/RIF identifies M tuberculosis and rifampin resistance using cartridge-based real-time
PCR
– Line-probe assays (eg, Hain GenoType) identify genotypic resistance to both isoniazid and
rifampin
1-2 days 1-2 wks 3-6 wks 4-12 wks
Average Turnaround Time for Diagnostic Tests
12. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
WHO Recommendations: Diagnosis of
MDR-TB
Xpert MTB/RIF should be used as the initial diagnostic test in
individuals suspected of MDR-TB[1]
However, Xpert MTB/RIF does not eliminate need for
conventional microscopy, culture, and DST to monitor treatment
progress and to detect resistance to drugs other than rifampin[1]
1. WHO. Xpert MTB/RIF system policy statement 2011.
2. Aurum Institute. Managing TB in a new era of diagnostics. 2012.
Xpert
Result[2]
Xpert Positive,
Rifampin
Susceptible
Xpert Positive,
Rifampin Resistant
Xpert Positive,
Rifampin
Unsuccessful
Xpert Negative Xpert
Unsuccessful
Interpretation Drug-sensitive TB Presumed MDR-TB Presumed
drug-sensitive TB
TB unlikely but
further investigation
necessary
No diagnosis
Actions Treat for drug-
sensitive TB;
collect sputum for
microscopy and
culture with DST
Treat with regimen
for MDR-TB; collect
sputum for TB
culture/DST
Treat for drug-
sensitive TB;
collect sputum for
microscopy and
culture with DST
Collect sputum for TB
microscopy and
culture to exclude TB
Collect sputum
for TB
microscopy and
culture to
exclude TB
13. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Performance of Xpert MTB/RIF vs Other
Diagnostic Modalities
Boehme C, et al. Lancet. 2011;377:1495-1505.
Proportion of TB Cases and Resistance Results by Each Method in Culture-Positive Patients
Liquid culture
MTB/RIF test
Solid culture
Microscopy
TBCasesDetected(%)
100
90
80
70
60
50
40
30
20
10
0
1000 20 40 60 80
Days to Detection
100%
90%
89%
67%
Line-probe assay
MTB/RIF test
Phenotypic drug-susceptibility
testing
0 20 40 60 80 100 120 140
Days to Detection
100%
94%
RIFResistanceDetected(%)
100
90
80
70
60
50
40
30
20
10
0
14. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Time to DST Results Halved With MDR
Line Probe Assay in South Africa
Time Period Median Time, Days (IQR) P Value
Before LPA After LPA
1 Sputum collection to lab
receipt of sample
1 (0-1) 0 (0-1) < .001
2 Lab receipt to DST testing 27 (21-34) 19 (12-31) < .001
Smear positive 26 (21-43) 13 (9-16) < .001
Smear negative 29 (22-43) 29 (22-42) .497
3 DST testing 9 (2-14) 0 (0-1) < .001
Total Sputum collection to DST
results available
52 (41-77) 26 (11-52) .008
Sputum
collection
Lab receipt
of sputum
DST started DST results
reported
1 2 3
Hanrahan CF, et al. PLoS One. 2012;7:e49898.
15. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Time to MDR Treatment Before and After
Line-Probe Assay in South Africa
From initial patient sputum sample to date of appropriate MDR therapy
Mos to MDR Treatment
80 2 4 6
1.00
0.75
0.50
0.25
0
CumulativeProportionon
MDRTreatment
After LPA
Before LPA (study data)
Before LPA (undetected MDR modeled)
Hanrahan CF, et al. PLoS One. 2012;7:e49898.
16. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Resistance at Start of Second-line TB Therapy
Drug Resistance, n (%)
First-line drugs
Ethambutol 826 (64.6)
Streptomycin 881 (69.0)
4 first-line drugs* 625 (49.0)
Second-line drugs
Any second-line drug 559 (43.7)
At least 1 fluoroquinolone 165 (12.9)
Second-line Injectable drugs
Kanamycin 237 (18.5)
Amikacin 205 (16.0)
Capreomycin 152 (12.0)
At least 1 255 (20.0)
All 134 (10.5)
Other oral second-line drug
Ethionamide 249 (19.5)
Aminosalicylic acid 137 (10.7)
At least 1 346 (27.1)
XDR-TB 86 (6.7)
PETTS Study: Prevalence of Drug
Resistance in 1278 Pts With MDR-TB
1278 pts enrolled in several
countries at start of second-line
TB treatment, 2005-2008
DST done centrally at CDC
High levels of resistance to
second-line drugs detected
– 43.7% with resistance to
≥ 1 second-line drug
– 20% with resistance to ≥ 1
injectable second-line drug
– 12.9% with resistance to
≥ 1 fluoroquinolone
– 6.7% with XDR-TB
Dalton T, et al. Lancet. 2012;380:1406-1417.
*Isoniazid, rifampin, ethambutol, streptomycin.
18. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
MDR-TB General Principles
An individualized approach should be undertaken
– Guided by drug susceptibility testing when available
– Assessment of comorbidities that may affect therapy should
be undertaken before therapy
Never add a single drug to a failing regimen
Use at least 3-5 previously unused drugs to which an
isolate has in vitro susceptibility
Supervise treatment to ensure adherence
Continue treatment for at least 18-24 mos after culture
conversion
WHO. Guidelines for programmatic management of drug-resistant TB. 2011.
Curry International Tuberculosis Center. Drug-resistant tuberculosis: a survival guide for clinicians.
19. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Drugs for MDR-TB
Group 1: First-line oral drugs
Ethambutol
Pyrazinamide
High-dose isoniazid
Group 2: Fluoroquinolones
Levofloxacin
Moxifloxacin
Gatifloxacin
Ofloxacin
Group 3: Injectable drugs
Kanamycin
Amikacin
Capreomycin
Streptomycin
Group 4: Oral bacteriostatic second-line drugs
Ethionamide
Prothionamide
Cycloserine/terizidone
Para-aminosalicylic acid
Group 5: Drugs of unclear efficacy
Clofazimine
Clarithromycin
Amoxicillin-clavulanate
Linezolid
Thiacetazone
Meropenem-clavulanate
Thioridazine
*Other newer drugs
Adapted from: Chang KC, et al. Respirology. 2013;18:8-21.
*Newer drugs will be discussed later in the educational activity.
20. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Building a Treatment Regimen for MDR-TB
Adapted from: Curry International Tuberculosis Center. Drug-resistant tuberculosis: a survival guide for
clinicians. Chang KC, et al. Respirology. 2013;18:8-21.
Step 1: Include any first-line
drugs to which the isolate is
susceptible
Injectables
Kanamycin
Amikacin
Capreomycin
Streptomycin
Step 2: Add a fluoroquinolone
Fluoroquinolone
Levofloxacin
Moxifloxacin
Gatifloxacin
First-line Drugs
Ethambutol
Pyrazinamide
Step 3: Include an
injectable agent
Oral Second-line Drugs
Ethionamide
Prothionamide
Cycloserine/terizidone
Para-aminosalicylic acid
Third-line Drugs
Clofazimine
Clarithromycin
Amoxicillin-clavulanate
Linezolid
Thiacetazone
Meropenem-clavulanate
Thioridazine
Other new drugs
Step 4: Include second-line
drugs until you have 4-6
drugs to which the isolate is
susceptible
Consider third-line drugs if
there are not 4-6 drugs to
which the isolate is
susceptible
21. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Treatment Regimens for MDR-TB
Resistance Pattern Regimen Comments
INH and RIF ± Strept PZA + EMB + FQN + injectable (for
≥ 6 mos) + second-line agent if
extensive disease
Treat 18-24 mos following
conversion
INH, RIF + (PZA or
EMB)
(PZA or EMB) + FQN + 2 second-
line agents + injectable agent (for
first 6 mos)
Treat 18-24 mos following
conversion;
consider additional agents,
high-dose INH
INH, RIF, PZA, EMB FQN + 3 second-line agents +
injectable drug for first 6-12 mos
Treat 18-24 mos following
conversion
INH, RIF, PZA, EMB,
FQN
Injectable + 3 second-line agents +
third-line agents
Treat 24 mos following conversion;
consider high-dose INH,
Surgery
INH, RIF, PZA, EMB,
injectables
FQN + all available second-line
agents; consider any third-line
agents if susceptible
Treat 24 mos following conversion;
consider surgery
Adapted from: Curry International Tuberculosis Center. Drug-resistant tuberculosis: a survival guide for
clinicians.
22. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
“Bangladesh” Regimen: Experimental
Short-Course Treatment for MDR-TB
Controlled trial under way to confirm the efficacy of this regimen
van Deun A, et al. Am J Respir Crit Care Med. 2010;182:684-692.
*Resistance likely for many MDR patients.
Phase Drugs
4-mo intensive phase High-dose INH*
Prothionamide*
Kanamycin
Gatifloxacin
Ethambutol*
Pyrazinamide*
Clofazimine
5-mo continuation phase Gatifloxacin
Ethambutol*
Pyrazinamide*
Clofazimine
23. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Potency and Tolerability of Existing TB
Drugs
Dorman SE, et al. Nat Med. 2007;13:295-298.
Increasing potency,
reliability,
reproducibility of
susceptibility testing
Decreasing
tolerability
First-line
Drugs
Second-line
Drugs
Rifampin
Isoniazid
Pyrazinamide
Ethambutol
Fluoroquinolones
(moxifloxacin, gatifloxacin,
levofloxacin)
Injectable agents
Aminoglycosides (streptomycin,
amikacin, kanamycin)
Polypeptides (capreomycin)
Oral bacteriostatic agents
(ethionamide, protionamide, cycloserine/
terizidone, p-aminosalicylic acid, thiacetazone)
Agents with unclear efficacy (clofazimine,
amoxicillin-clavulanate, clarithromycin, linezolid)
24. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Adverse Effects of MDR-TB Drugs
Drug Toxicities and Adverse Effects
Ethambutol Visual acuity, color vision
Pyrazinamide Hepatotoxicity
Isoniazid Neurologic effects, hepatotoxicity
Injectables Vestibular, renal toxicity, hearing loss
Fluoroquinolones GI, CNS, cardiac toxicities, tendinopathy
Cycloserine/terizidone CNS toxicity, behavioral changes
Ethionamide GI toxicity, hypothyroidism
PAS GI toxicity, hypothyroidism, osteoarticular pain.
Clofazimine Changes in skin and ocular pigmentation, GI effects
Linezolid Thrombocytopenia, neutropenia, neuropathy, metallic taste
Aurum Institute. Managing TB in a new era of diagnostics. 2012.
26. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Bedaquiline
Oral diarylquinoline
Target: ATP synthase
– Activity specific to mycobacteria
Bactericidal activity
comparable to RIF-INH-PZA
in mice
Sterilizing activity comparable
to rifampin in mice
Synergy with PZA
No cross-resistance with other antimycobacterial drugs (INH, RIF,
EMB, PZA, streptomycin, amikacin, or moxifloxacin)
Andreas K, et al. Science. 2005;307:223-227. CDC. MMWR Morb Mortal Wkly Rep. 2013;62:1-12.
Br
N O
(S)
H
O(R) N
27. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
C208: Phase II Trial of Bedaquiline for
MDR-TB
Stage I study: 47 pts with newly
diagnosed pulmonary MDR-TB
randomized to bedaquiline or
placebo in combination with
5-drug second-line TB regimen
– BDQ dose: 400 mg QD for
2 wks, then 200 mg TIW for
6 wks
BL resistance: pyrazinamide,
65%; ethambutol, 59%;
kanamycin, 8%; ofloxacin, 8%;
ethionamide, 8%
BDQ reduced time to culture
conversion (HR: 11.8; 95% CI:
2.3-61.3; P = .003)
Incidence of AEs similar
between arms
– Nausea more frequent in
BDQ vs placebo: 26% vs 4%
(P = .04).Diacon AH, et al. N Engl J Med. 2009;360:2397.
0
0.2
0.4
0.6
0.8
1.0
0 7 42
Culture-PositivePatients(%)
14 21 28 35 49 56
Placebo (n = 24)
Bedaquiline (n = 23)
Days
52%
91%
28. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
C208: Phase II Trial of Bedaquiline for
MDR-TB
Stage II study: 15 sites in Brazil,
India, Latvia, Peru, Philippines,
Russia, South Africa, Thailand
Pts randomized to receive BDQ
(n = 67) vs placebo (n = 66) for
24 wks with 5-drug BR
– BDQ dose: 400 mg QD for
2 wks, then 200 mg TIW for
22 wks
After Wk 24, both groups
continued the 5-drug BR to
total of 96 wks
Culture conversion at Wk 24
significantly higher with
bedaquiline vs placebo
Cure rate also significantly
higher
WHO. The use of BDQ in treatment of MDR-TB—interim policy guidance. 2013.
Outcome BDQ Placebo P Value
Median time to
sputum conversion,
days (95% CI)
83
(56-97)
125
(98-168)
< .0001
Pts with culture
conversion, %
Wk 24
Wk 72
Wk 120
78.8
71.2
62.1
57.6
56.1
43.9
.008
.069
.035
Proportion cured,
%
57.6 31.8 .003
29. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
FDA Bedaquiline Indication
Approved by FDA in 2012 as part of combination therapy
in adults with pulmonary MDR-TB
– Should be used only when an effective treatment regimen
cannot otherwise be provided[1]
Recommended dose: 400 mg PO QD for 2 wks, then
200 mg PO TIW, for a total duration of 24 wks
First drug with novel mechanism approved by FDA for TB
since 1971
Bedaquiline [package insert].
30. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
CDC Provisional Guidance on Bedaquiline
BDQ may be used as a component of TB therapy when an
effective treatment regimen cannot otherwise be provided
– Administer by DOT for 24 wks with food in adults with
laboratory-confirmed pulmonary MDR-TB
– Use on case-by-case basis in children, HIV-positive pts,
pregnant women, pts with extrapulmonary MDR-TB, and pts
with comorbid conditions on concomitant medications
– Use on case-by-case basis for durations > 24 wks
CDC. MMWR Morb Mortal Wkly Rep. 2013;62:1-12.
31. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
WHO Interim Guidance on Use of
Bedaquiline
BDQ may be added to a WHO-recommended regimen in
adult MDR-TB patients under following conditions:
– When an effective treatment regimen containing 4 second-
line drugs in addition to PZA, according to WHO
recommendations, cannot be designed
– When there is documented resistance to any fluoroquinolone
in addition to MDR
– Recommended for adults older than 18 yrs of age under
carefully monitored conditions
WHO. Bedaquiline for MDR-TB. 2013.
32. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Bedaquiline Safety Concerns
Black box warning: increase in all-cause mortality and
prolongation of QT interval—monitor EKGs[1]
– 30 deaths occurred in the clinical trial program in patients
receiving BDQ vs 6 on placebo[2]
BDQ should be used with caution with other drugs that
can cause QT interval prolongation and EKGs should be
monitored more often[1]
– Includes clofazimine and fluoroquinolones
BDQ should not be used with rifampin or rifapentine,
which are strong inducers of CYP3A4[1]
1. Bedaquiline [package insert]. 2. CDC. MMWR Morb Mortal Wkly Rep. 2013;62:1-12.
33. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Bedaquiline Monitoring
All patients should be monitored wkly for adverse effects
EKGs should be monitored at baseline and at least 2, 12, and 24 wks after
starting treatment
Serum potassium, calcium, and magnesium should be measured at baseline
and whenever clinically indicated, especially if QT interval prolongation is
detected
All patients started should be included in a registry for ongoing monitoring
Additional notes:
– Bedaquiline should never be used as a single drug
– Bedaquiline has a long terminal half-life of 4-5 mos; should be discontinued before
other drugs in regimen
– Rifamycins and other CYP3A4 inducers reduce bedaquiline concentrations
– Bioavailability is significantly affected by food
CDC. MMWR Morb Mortal Wkly Rep. 2013;62:1-12.
34. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Delamanid (OPC-67683)
Nitro-dihydro-imidazooxazole
Derivative of metronidazole
Inhibits mycolic acid synthesis
Potent preclinical in vitro and in vivo activity against both
drug-susceptible and drug-resistant strains of TB
Skripconoka V, et al. Eur Respir J. 2013;41:1393-1400.
N
O
O
F
F
FO
OO
O
N+
N
N
35. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Delamanid: Phase II Trial vs Placebo
Multinational trial of pts with
pulmonary MDR-TB
Pts randomized to 2 mos of
– Delamanid 100 mg (n = 161)
– Delamanid 200 mg (n = 160)
– Placebo (n = 160)
– Each with WHO BR
Primary endpoint: sputum
culture conversion at 2 mos
Delamanid significantly
increased rate of sputum
conversion vs placebo after
2 mos of treatment
QT prolongation reported
significantly more frequently
with delamanid
All other AEs mild to moderate
and similar among groupsGler MT, et al. N Engl J Med. 2012;366:2151-2163.
Patients(%)
41.9
29.6
45.4
100
80
60
40
20
0
Delamanid
200 mg
Delamanid
100 mg
Placebo
57/136 37/12564/141
P = .04
P = .008
n/N =
Mycobacterial Growth Indicator Tube
Culture Conversion at Day 57
36. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
EMEA Delamanid Recommendation
In November 2013, the European Committee for Medicinal
Products for Human Use recommended granting a
conditional marketing authorization for delamanid for the
treatment of MDR-TB
Recommended indication:
– Use as part of an appropriate combination regimen for
pulmonary MDR-TB in adult patients when an effective
treatment regimen cannot otherwise be composed for
reasons of resistance or tolerability
EMEA. Marketing authorization for delamanid. November 2013.
37. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Linezolid
Oxazolidinone, approved to treat
drug-resistant, Gram-positive bacteria
Good activity against MDR-TB in vitro and in animal studies
Use in TB often limited due to long-term toxicities (bone marrow
suppression, neuropathy)
However, retrospective chart review (2003-2007) of 30 pts (29 with
pulmonary TB) who received linezolid 600 mg QD (plus vitamin B6) as
part of a regimen for MDR-TB concluded[1]
:
– Culture conversion occurred in all pulmonary cases at median of 7 wks
– AEs occurred in only 9 patients, including peripheral and optic neuropathy,
anemia/thrombocytopenia, rash, and diarrhea
– Only 3 patients stopped linezolid treatment because of AEs
1. Schecter GF, et al. Clin Infect Dis. 2010;50:49-55.
F
O
N
N
O
O O
N
H
38. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Linezolid 600 mg QD
immediately*
Linezolid 600 mg QD
delayed by 2 mos*
Pts with sputum-
culture–positive XDR-
TB (no response to
any TB drugs in
previous 6 mos)
(N = 41)
Smear conversion or 4 mos
*All pts remained on background regimen of drugs they were taking before study entry.
Second randomization continued at least 18 mos after smear conversion or after 4 mos on first regimen.
Linezolid 600 mg QD
22 mos
Linezolid 300 mg QD
Lee M, et al. N Engl J Med 2012;367:1508-1518.
Phase II Trial of Linezolid in Patients With
XDR-TB
Phase II trial in South Korea
Primary endpoint: time to sputum-culture conversion on solid medium (data
censored 4 mos after study entry)
Linezolid 600 mg QD
Linezolid 300 mg QD
39. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Phase II Trial of Linezolid in Patients With
XDR-TB
Culture conversion at 4 mos:
– 79% (15/19) in immediate arm
vs 35% (7/20) in delayed arm
(P = .001)
87% (34/39) with negative
sputum culture within 6 mos
31 pts (82%) with clinically
significant AEs related to LZD
– 3 pts d/c therapy
Pts on LZD 300 mg on second
randomization had fewer AEs
13 pts completed therapy
without relapse
4 pts acquired LZD resistance
Lee M, et al. N Engl J Med. 2012;367:1508-1518.
1.0
0.8
0.6
0.4
0.2
0
0 30 60 90 120 150 180
Days Since Start of LZDCumulativeProbability
ofConversion
Conversion Probability
According to Time on Treatment
40. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Sutezolid (PNU-100480)
Oxazolidinone, related to linezolid
MOA: protein synthesis inhibition[1]
Like LZD, has a high barrier to
resistance
More potent than LZD in mice,
whole blood culture
Efficacy in mice similar to isoniazid and/or rifampin and may be
synergistic with other first-line drugs
May be safer than LZD
S
N
F
O
N O
OH
N
H
CH3
1. Alffenaar JW, et al. Antimicrob Agents Chemother. 2011;55:1287-1289.
41. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Early Bactericidal Activity of Sutezolid in
HIV+/- Pts With Drug-Susceptible TB
Significant log CFU reductions with
both sutezolid regimens during the
14-day treatment period
– 600 mg BID: -0.09 log/day
(90% CI: -0.06 to -0.11)
– 1200 mg QD: -0.07 log/day
(90% CI: -0.04 to -0.09)
– Trend toward superior response
with BID dosing
Both dosing schedules generally
safe and relatively well tolerated
– 7/50 sutezolid-treated pts
experienced ALT increases to
2-3 x ULN, which were
asymptomatic and resolved
spontaneously
Wallis RS, et al. AIDS 2012. Abstract THLBB02. Graphic used with permission.
0
-1
-2
-3
140 2 4 6 8 10 12
Day
ChangeinlogCFU 1200 QD
600 BID
HREZ
42. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
PA-824
PA-824: nitroimidazole-oxazine
– Active in vitro and in mouse
models
Cross-resistant with delamanid
High protein binding may render PA-824 less accessible in
cavities of pulmonary TB
May be useful in combination regimens; synergistic with
other drugs
F
F F
O
O
O
O
ON
N+
43. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Novel Drug Combinations With PA-824
Show Promise in Mouse Models
PA-824 with moxifloxacin and
pyrazinamide cures TB more
rapidly than the first-line regimen in
mice[1]
Bedaquiline + PA-824 + sutezolid
may provide a novel 3-drug
backbone for a universally active
short-course regimen[2]
Regimen
(Duration)
Mice Cured, % (n/N)
4 Mos 5 Mos 6 Mos
RIF-INH-PZA (2
mos) + RIF-INH (4
mos)
50
(10/20)
100
(20/20)
100
(20/20)
RIF-MXF-PZA (2
mos) + RIF-MXF (3
mos)
95
(19/20)
100
(20/20)
100
(20/20)
Pa-MXF-PZA (2
mos) + Pa-MXF (4
mos)
100
(20/20)
100
(20/20)
100
(20/20)
Regimen
Relapse, % (n/N) After Tx for
2 Mos 3 Mos 4 Mos
RIF + PZA +
INH
ND
100
(15/15)
64
(9/14)
BDQ + SUT +
CFZ + Pa
93
(14/15)
13
(2/15)
7
(1/15)
BDQ + SUT +
CFZ
87
(13/15)
27
(4/15)
7
(1/14)
BDQ + SUT +
Pa
100
(15/15)
43
(6/14)
0
(0/15)
BDQ + CFZ +
Pa
100
(15/15)
60
(9/15)
33
(5/15)
SUT + CFZ +
Pa
100
(15/15)
100
(15/15)
100
(15/15)
1. Nuermberger EL, et al. Antimicrob Agents
Chemother. 2008;52:1522-1524. 2. Williams K, et al.
Antimicrob Agents Chemother. 2012;56:3114-3120.
44. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
HIV-negative or
HIV-positive pts* with
newly diagnosed
pulmonary smear and
culture-positive drug-
sensitive TB
(N = 83)
Day 14
Early Bactericidal Activity of Novel
Combinations of TB Drugs
Phase II trial in TB-infected pts
Diacon AH, et al. Lancet. 2012;380:986-993.
Bedaquiline + Pyrazinamide
(n = 15)
Bedaquiline + PA-824
(n = 15)
PA-824 + Pyrazinamide
(n = 15)
Rifampin/Isoniazid/Ethambutol/Pyrazinamide
(n = 8)
Bedaquiline
(n = 15)
PA-824 + Pyrazinamide + Moxifloxacin
(n = 15)
*6 HIV-positive subjects.
45. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Early Bactericidal Activity of Novel TB
Regimens
0.5
0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
0 142 4 6 8 10 12
Day
LogCFUChangeFromBaseline
Bedaquiline
Bedaquiline + PZA
Bedaquiline + PA-824
RHEZ
PA-824 + PZA
PA-824 + PZA + moxifloxacin
Diacon AH, et al. Lancet. 2012;380:986-993.
Standard-of-
care regimen
Novel PA-824/
PZA/moxifloxacin
regimen
46. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Prevention of MDR-TB
Prevention of MDR-TB involves adequate, proper treatment of
initial disease to prevent selection of resistance
– Prompt diagnosis with adequate TB treatment under DOT
– Rapid identification of MDR-TB and use of appropriate second-line
regimens
– Avoid further evolution of resistance
– Airborne infection control
– Preventive treatment of TB/HIV coinfection with optimal use of
ART
Management strategies for established cases mainly rely on
specific alternative treatment regimens complemented with
surgery in carefully selected cases
47. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Preventive Therapy in Contacts of Pts
With MDR-TB in Micronesia
232 contacts of 5 pts with 2 different MDR-TB strains
105 with positive TST received preventive therapy
Strain A: resistant to isoniazid, rifampin, pyrazinamide,
ethambutol, and streptomycin
– Contacts offered fluoroquinolone alone or in combination
with ethionamide
Strain B: resistant to isoniazid, rifampin, and ethionamide
– Contacts offered fluoroquinolone with ethambutol
No cases of MDR-TB developed in those treated
– 28 untreated contacts developed MDR-TB
ECDC. Management of contacts of MDR TB and XDR TB patients. 2012.
48. clinicaloptions.com/hiv
Recent Advances in Multidrug-Resistant TB
Conclusions
Current approaches to MDR-TB therapy are long, with
much toxicity
Bedaquiline is the first drug with a novel mechanism of
action to be approved by FDA for MDR-TB since 1971
Delamanid recently approved by European Medicines
Agency
– Both agents indicated only when an effective regimen
cannot otherwise be provided
Multiple new drugs are in the pipeline
Successful eradication of MDR-TB will require new drug
regimens with novel drug combinations
49. Go Online for More CCO
Educational Content on Multidrug-
Resistant TB!
Interactive Virtual Presentation featuring streaming narration of these
slides by expert faculty Richard E. Chaisson, MD, and Maunank Shah,
MD
clinicaloptions.com/hiv
Editor's Notes
TB, tuberculosis.
Hello, my name is Richard E. Chaisson, MD, and I’d like to welcome you to this CME-certified program, “Recent Advances in Multidrug-Resistant TB.”
You are welcome to use these slides for personal study and for your own noncommerical presentations but please do not change content or attribution.
I am Professor of Medicine, Epidemiology and International Health at Johns Hopkins University School of Medicine and Bloomberg School of Public Health, and I direct the Johns Hopkins Center for AIDS Research and the Center for Tuberculosis Research. I was joined by Maunank Shah, MD, also of Johns Hopkins University, to plan the content for this educational activity.
MDR, multidrug resistant; TB, tuberculosis.
Let’s discuss the epidemiology of multidrug-resistant tuberculosis.
MDR, multidrug resistant; TB, tuberculosis.
Tuberculosis drug resistance can be defined as acquired or primary. Acquired drug resistance is the selection of preexistent natural mutants through inadequate treatment. Primary drug resistance is infection with an organism that was resistant to antimicrobials when the infection was acquired.
Multidrug-resistant TB—MDR-TB—is conventionally defined as resistance to at least isoniazid and rifampin (and other rifamycins). However, many people with MDR-TB have organisms resistant to a variety of drugs. Extensively drug–resistant TB—or XDR-TB—is MDR-TB with additional resistance to fluoroquinolones and one of the injectable agents amikacin, kanamycin, streptomycin, or capreomycin.
MDR, multidrug resistant; TB, tuberculosis; XDR, extensively drug resistant.
Drug-resistant TB that is acquired generally results from improper treatment: either the wrong selection of drugs by physicians or poor adherence to the treatment by patients, either of which results in the selection of naturally occurring mutants with innate resistance.
Patients with acquired drug-resistant TB can then spread infection to others, causing primary resistance in their contacts. In many countries, transmission of drug-resistant TB is now more common than acquired resistance.
Therefore, the key prevention strategies for drug-resistant TB are to avoid the creation of new cases by treating TB properly and preventing transmission of infection through early and proper diagnosis and infection control for those with MDR-TB.
MDR, multidrug resistant; TB, tuberculosis.
The World Health Organization monitors the global epidemiology of MDR-TB. Their 2012 report estimated that there were at least 450,000 new cases of MDR-TB across the world.
Among all new cases of tuberculosis, approximately 3.5% are MDR-TB. Among individuals with previous treatment for tuberculosis, about 20% have MDR-TB. More than one half of the new MDR-TB cases occur in 3 countries: China, India, and the Russian Federation. Mortality in MDR-TB patients usually exceeds 10%—in 2012, MDR-TB caused an estimated 170,000 deaths.
MDR, multidrug resistant; TB, tuberculosis.
This slide shows a map of the prevalence of MDR-TB among TB cases during the period 1994-2012. The areas shaded in darker blue indicate a high prevalence of MDR-TB; the darkest blue shading represents areas where more than 18% of all new cases of tuberculosis were among those with MDR-TB. It can be seen that the former Soviet Union is the area of the world with the highest prevalence of MDR-TB, but China, India, and some countries in sub-Saharan Africa have an appreciable prevalence of multiple drug–resistant TB.
MDR, multidrug resistant; TB, tuberculosis.
This slide shows MDR-TB cases among previously treated TB patients, who as mentioned earlier, have a higher prevalence of resistance. Here, the darker colors represent prevalence considerably higher than on the last slide—the darker orange represents that MDR-TB is seen in &gt; 50% of patients with TB that was previously treated. This very high prevalence is seen among several states of the former Soviet Union.
MDR, multidrug resistant; TB, tuberculosis.
Let’s talk about the diagnosis of MDR-TB.
DST, drug sensitivity test; MDR, multidrug resistant; PCR, polymerase chain reaction; TB, tuberculosis.
There are multiple diagnostic modalities for detecting drug-resistant TB. The gold standard is the phenotypic assay: culture of a sputum specimen or other tissue specimen to assess inhibition of mycobacterial growth in the presence of antibiotics.
Historically, solid-media assays have been used most commonly for phenotypic drug resistance testing, but the results from these assays take as long as 8 weeks to return. The automated liquid-culture systems, such as the Midget System and others like it, are much faster and more sensitive than solid media assays, and results are available within several weeks after the primary isolation of mycobacterium tuberculosis on culture.
In the last several years, several innovative, new rapid molecular tests for identification of genotypic resistance within a day have been introduced on the market. One of the most widely used new molecular test is the Xpert TB/RIF test, which identifies mycobacterium tuberculosis genes and also identifies rifampin resistance, using a cartridge‑based real-time PCR assay. Another widely used test is a line probe assay, such as the one made by Hain, the GenoType, which identifies genotypic resistance to both isoniazid and rifampin.
The average turnaround time for these diagnostic tests is illustrated in the graphic at the bottom of the slide. As shown at the left, rapid molecular tests can identify both tuberculosis and drug resistance in 1-2 days. Liquid culture systems take 1-2 weeks, solid culture media take 3-6 weeks; and phenotypic drug susceptibility testing using either liquid or solid culture media take 4-12 weeks.
DST, drug sensitivity testing; MDR, multidrug resistant; TB, tuberculosis; WHO, World Health Organization.
The World Health Organization has issued recommendations for the diagnosis of MDR-TB, using both molecular and conventional tests. The WHO recommends that the Xpert MTB/RIF test should be used as the initial diagnostic test in individuals suspected of having MDR-TB. However, the use of the Xpert MTB/RIF test does not eliminate the need for conventional microscopy, culture, and drug-susceptibility testing, both to confirm the diagnosis and to monitor treatment progress, and detect resistance to drugs other than rifampin. We must remember that the Xpert MTB/RIF test can detect resistance to rifampin only.
The table at the bottom of this slide illustrates the possible results that an Xpert test might yield and how they should be interpreted. I’ll draw your attention to the third column, which includes results that are Xpert positive and show rifampin resistance. In this instance, we have to presume that the patient has MDR-TB and begin treatment with a regimen appropriate for MDR-TB. However, it’s important to also collect sputum for conventional culture and drug-susceptibility testing, as Xpert only informs about rifampin resistance and cannot tell us about resistance to other important antibiotics such as isoniazid, fluoroquinolones, and other first- and second-line drugs. These results would affect the type of regimen chosen for management of the MDR-TB.
TB, tuberculosis.
This slide illustrates the performance characteristics of the Xpert test and several other diagnostic modalities.
On the left side of the slide, we see data regarding the time to the return of test results and the proportion of cases diagnosed. The yellow line illustrates results with smear microscopy. What we can see is that smear microscopy results are returned very quickly, usually within several days. However, the sensitivity of the test is only 67%.
In orange, we see the Xpert MTB/RIF test, showing that 90% of the patients are identified by this test and results are obtained within 1-2 days. In blue, we see mycobacterial culture using liquid-culture medium. This test has 100% sensitivity, but the results take slightly longer to return, with a median time of about 10-12 days and an ultimate time of about 3-4 weeks before all results are obtained. Solid culture, shown in green, has sensitivity that is as good as the Xpert test, but the median time to make a diagnosis in solid culture is about 40 days.
On the right-hand side, we see a comparison of the Xpert MTB/RIF test and the line probe assay, along with traditional, conventional phenotypic drug susceptibility testing. Once again, the sensitivity of the Xpert test (shown in orange) is extremely high—94%—and results are available within 1-2 days. In green, we see results from the standard phenotypic drug-susceptibility testing, which takes many weeks—a median of over 100 days for results to return. And in the middle in blue, we see the line probe assay, which has a median time to result of about 20 days and, overall, has 100% sensitivity.
DST, drug sensitivity testing; IQR, interquartile range; LPA, line-probe assay; MDR, multidrug resistant.
An important study on the clinical impact of drug-susceptibility testing with molecular assays was done by Hanrahan and colleagues and published in PLOS One in 2012. This study, done in a real-world setting in South Africa, looked at the impact of the introduction of the line probe assay on the time to obtaining test results.
What we see in this table at the bottom is that the time from the collection of sputum to the availability of drug-susceptibility test results was cut in half by introduction of the line probe assay. On average, it took 52 days for a result to return in the pre–line probe assay days compared with 26 days after introduction of the line probe assay.
LPA, line-probe assay; MDR, multidrug resistant.
In this slide, we see in orange the median time to beginning MDR treatment after submission of a sputum specimen before the line probe assay was introduced was about 70 days. With the introduction of the line probe assay, shown in blue, this time was reduced by about 20 days. However, this overlooks an important fact, which is that the line probe assay increased the sensitivity of testing for MDR-TB and doubled the number of patients with MDR-TB who were detected. If we include the patients who were diagnosed with MDR-TB prior to the introduction of the line probe assay, along with those who were not diagnosed and went untreated, shown in green, one can see that the line probe assay had a significant impact on both the rate of detection and the time to treatment of patients with MDR-TB. This therefore, represents an important public health advance.
CDC, Centers for Disease Control and Prevention; DST, drug sensitivity testing; MDR, multidrug resistant; TB, tuberculosis; XDR, extensively drug resistant.
Finally I’d like to reiterate the importance of testing for resistance to drugs other than rifampin. The PETTS study, done by the Centers for Disease Control and Prevention and collaborators around the world, looked at over 1200 patients who had MDR-TB and studied the prevalence of resistance to other drugs besides isoniazid and rifampin. Overall, half of the patients had resistance to 4 first-line drugs for TB; that is, in addition to resistance to isoniazid and rifampin, they also had resistance to ethambutol and streptomycin,
A large proportion—44%—also had resistance to at least 1 second-line drug for tuberculosis,and 13% had resistance to a fluoroquinalone. A total of 7% had XTR-TB. These data underscore the importance of additional drug-susceptibility testing for those patients who are identified as having MDR-TB. As mentioned earlier, these patients frequently have resistance to multiple drugs, not just to the 2 drugs—isoniazid and rifampin—which constitute the official definition of MDR-TB.
MDR, multidrug resistant; TB, tuberculosis.
Hello. My name is Dr. Maunank Shah, and I will continue the program by discussing the treatment and prevention of multidrug-resistant tuberculosis.
MDR, multidrug resistant; TB, tuberculosis.
Let’s first start with some general MDR-TB treatment principles.
Perhaps the first thing to remember is to take a comprehensive medical history, which includes an assessment of comorbidities, since these may impact upon drug selection and monitoring for toxicities. Whenever possible, an individualized regimen should be constructed based upon the isolate’s drug susceptibility testing to first- and second-line drugs because resistance patterns are not uniformly predictable. In general, one should never add a single drug to a failing regimen, since this will likely lead to the acquisition of further drug resistance.
When possible, at least 3-5 drugs to which the isolate has in vitro susceptibility should be used, and preferably these should not be drugs to which the patient has previously been exposed. Given the long duration of MDR-TB treatment, supervision—usually direct observation—is generally needed to ensure good adherence and meticulous monitoring for drug toxicities. Overall, treatment duration should last for at least 18-24 months after cultures have converted to negative.
MDR, multidrug resistant; TB, tuberculosis.
So, what are the actual drugs that we use to treat MDR-TB? On this slide, you see a partial list of drugs that is grouped into 5 distinct categories.
In group 1 are first-line oral agents. It is important to remember that even if there is resistance to isoniazid and rifampin, other first-line agents such as ethambutol and pyrazinamide may still be active.
The backbone of therapy for MDR-TB, however, is the fluoroquinolones and injectable drugs. Among the fluoroquinolones, the newer-generation agents such as moxifloxacin and levofloxacin are generally preferred, since they are more potent against tuberculosis.
The injectable agents include aminoglycosides, such as streptomycin, amikacin, and kanamycin. Capreomycin, another injectable agent active against MDR-TB, is not an aminoglycoside but shares pharmacokinetic properties and drug toxicities with the other aminoglycosides.
The oral bacteriostatic second-line agents are less potent than the first‑line agents, fluoroquinolones and injectable drugs, but are often used to make up the rest of an MDR-TB treatment regimen. These include ethionamide, cycloserine, and para-aminosalicylic acid (PAS).
Finally, there are other agents that are sometimes included in MDR-TB treatment regimens to which we do not necessarily have great data in terms of efficacy but are sometimes included.
MDR, multidrug resistant; TB, tuberculosis.
So, how do we build a treatment regimen for multidrug-resistant tuberculosis? The first step is to include any first-line agents to which the isolate appears to be susceptible, such as ethambutol and pyrazinamide. Occasionally, if there is documented to be only low-level resistance to isoniazid, high-dose isoniazid may be utilized in the regimen.
After including any first-line agents to which the isolate is susceptible, a fluoroquinolone should be always included as part of the backbone to an MDR-TB treatment regimen. In addition to fluoroquinolones, injectable bactericidal agents, such as kanamycin, amikacin, capreomycin, or streptomycin, should be utilized in the intensive phase of therapy.
Once first-line drugs, fluoroquinolones, and injectables have been included, one completes the regimen by including oral second-line agents until there is a total of 4-6 drugs to which the isolate is susceptible. The second-line drugs, once again, include drugs such as ethionamide, prothionamide, cycloserine, and PAS.
In the event that, due to extensive drug resistance or intolerability, a regimen of 4-6 drugs is not able to be constructed from the first 4 groups of agents, third-line drugs can be considered as additions until a complement of 4-6 drugs is attained.
EMB, ethambutol; FQN, fluoroquinalone; INH, isoniazid; MDR, multidrug resistant; PZA, pyrazinamide; RIF, rifampin; Strept, streptomycin; TB, tuberculosis.
This slide illustrates some of the potential treatment regimens that could be constructed for various MDR-TB isolates based on resistance patterns and the general treatment principles that we have just outlined. In the left column of the table, one can see the different resistance patterns; in the middle, some potential regimen choices; and on the far right, the suggested treatment durations. As an example (looking at the first row), if a patient is resistant to isoniazid and rifampin alone, but susceptible to other first-line agents, a regimen consisting of pyrazinamide and ethambutol in conjunction with fluoroquinolones and injectable agents could be constructed. In this scenario, second-line agents could be added to make up 4 to 6 drugs or if there is extensive disease.
For all of these treatment regimens, the injectable agent should generally be utilized for a minimum of 6 months, and preferably for at least 6 months after sputum culture conversion has been achieved. The complete treatment duration is generally for an additional 18 to 24 months following culture conversion.
INH, isoniazid; MDR, multidrug resistant; TB, tuberculosis.
The treatment of MDR-TB can be quite prolonged. It is worth noting that several experimental shorter-course regimens are being evaluated. This slide illustrates that one of these—the Bangladesh Regimen. Researchers have examined the treatment outcomes of this short-course intensified regimen which uses 7 drugs in a 4-month intensive phase, followed by 4 drugs in a 5-month continuation phase. In uncontrolled, unblinded studies, the authors reported that nearly 85% of patients achieved relapse-free cure. Such research is promising and enticing, but further controlled trial data are needed to better examine the efficacy of this regimen and to assess the impact of different patterns of resistance on the success or failure of shorter-course therapy.
TB, tuberculosis.
In addition to MDR-TB therapy being significantly prolonged compared with that of drug-sensitive TB treatment, the drugs are also difficult to tolerate and have significant toxicities. In this slide, we provide a generalized picture of the reduced potency and increased toxicity associated with drugs currently used for MDR-TB.
CNS, central nervous system; GI, gastrointestinal; MDR, multidrug resistant; PAS, para-aminosalicylic acid; TB, tuberculosis.
These toxicities can unfortunately be quite significant and are summarized here. Gastrointestinal toxicities in particular are extremely common with many of these agents. Ethionamide, for example, can be associated with severe nausea and vomiting, and PAS often causes abdominal pain and lower GI tract symptoms, including diarrhea. Similarly, fluoroquinolones, when used for a prolonged period of time, can sometimes lead to Clostridium difficile–associated diarrhea, as well as other potential cardiac toxicities.
The most common and difficult-to-manage side effects of MDR-TB therapy are related to the injectable agents. The injectable agents, including the aminoglycosides and capreomycin, may be associated with ototoxicity, including hearing loss. These agents also have the potential to cause renal toxicity and insufficiency, particularly when used at higher doses or for prolonged periods of time.
Other notable toxicities associated with these MDR-TB drugs are the behavioral changes and CNS toxicity that can be seen with cycloserine and hypothyroidism, seen with ethionamide and PAS. Substantial monitoring for toxicity is important with use of all of these drugs.
MDR, multidrug-resistant; TB, tuberculosis.
Let’s now move on to a discussion of newer drugs for MDR-TB therapy. For many decades, the pipeline for new TB agents was very small. But in recent years, a number of promising new drugs are being developed which may have efficacy against MDR-TB.
ATP, adenosine triphosphate; EMB, ethambutol; INH, isoniazid; PZA, pyrazinamide; RIF, rifampin.
Perhaps the most significant of these newer agents is bedaquiline. Bedaquiline is a new drug class altogether—an ATP-synthase inhibitor. It is an oral diarylquinoline which has shown bactericidal activity in mice comparable to first-line agents. Interestingly, in addition to its bactericidal activity, it appears to have strong sterilizing activity comparable to rifampin in murine models. It appears to be synergistic with pyrazinamide, and because it represents a new drug class, there is no cross-resistance with other antimycobacterial drugs that has been documented.
AE, adverse event; BDQ, bedaquiline; BL, baseline; MDR, multidrug resistant; QD, once daily; TIW, 3 times weekly; TB, tuberculosis.
Bedaquiline efficacy has been evaluated in a number of studies, including a 2‑stage phase II trial, which is represented here. The initial stage was exploratory; the second stage was a larger, randomized placebo-controlled trial.
On this slide, some of the data from the initial stage is shown. In total, 47 patients with newly diagnosed pulmonary TB were randomized to an 8-week regimen that included bedaquiline in combination with 5 second-line TB drugs. Individuals who were receiving bedaquiline had a reduced time to the primary endpoint, culture conversion. Incidence of adverse events was similar between arms.
BDQ, bedaquiline; BR, background regimen; MDR, multidrug resistant; QD, once daily; TIW, 3 times weekly; TB, tuberculosis.
On the basis of these promising data, the larger stage II study, which examined longer courses of bedaquiline, was conducted in 15 sites across multiple countries. Patients were randomized to receive bedaquiline at 400 mg daily for 2 weeks, followed by 200 mg 3 times a week for 22 weeks, in combination with a 5‑drug optimized background regimen. This was compared with a placebo arm given for the same time period. The primary endpoint of this study was median time to sputum culture conversion. Patients were then followed up for an additional 72 weeks of therapy with the background regimen.
The table in the slide shows that the group receiving bedaquiline had a shorter median time to sputum culture conversion, a higher percentage of patients with culture conversion, and a higher percentage of patients with cure at 24, 72, and 120 weeks.
FDA, US Food and Drug Administration; MDR, multidrug resistant; PO, orally; QD, once daily; TB, tuberculosis; TIW, 3 times weekly.
Given these promising efficacy data, the FDA approved bedaquiline as part of an accelerated approval process in 2012. The indication was for use in combination therapy in adults with pulmonary MDR-TB at a dose of 400 mg daily for 2 weeks, followed by 200 mg 3 times per week, for a total duration of 24 weeks.
The approval of bedaquiline was quite notable because it represented the first time a drug with a novel mechanism of action had been approved by the FDA for the treatment of tuberculosis since 1971.
BDQ, bedaquiline; DOT, directly observed therapy; MDR, multidrug resistant; TB, tuberculosis.
This recommendation was later followed by provisional guidance offered by the CDC. In 2013, the CDC offered guidance that suggested that bedaquiline could be used as a component of TB therapy when an effective treatment regimen could not otherwise be provided. Bedaquiline should be used in directly observed therapy for 24 weeks with food in adults in patients with laboratory-confirmed pulmonary TB. On a case-by-case basis, bedaquiline may be considered for use in children, HIV-positive patients, pregnant women, or in patients with extrapulmonary MDR-TB. It should be noted, however, that the pharmacokinetics and other drug outcomes have not yet been fully studied in these particular subpopulations. On a case-by-case basis, depending on treatment outcomes, bedaquiline can be considered for durations greater than 24 weeks.
BDQ, bedaquiline; MDR, multidrug resistant; PZA, pyrazinamide; TB, tuberculosis; WHO, World Health Organization.
Similar to the CDC guidance, the WHO also offered interim guidance in 2013, with very similar recommendations. The WHO suggested that bedaquiline may be used in addition to a WHO-recommended background regimen in adults with MDR-TB when an effective treatment regimen containing at least 4 second-line drugs in addition to pyrazinamide cannot be designed.
The WHO also suggested that bedaquiline might be considered when documented resistance was found to fluoroquinolones in addition to drug resistance to isoniazid and rifampin. It is recommended primarily for adults older than 18 years of age under carefully monitored conditions.
BDQ, bedaquiline; EKG, electrocardiogram.
Despite the optimism surrounding this new agent, there are several important safety concerns that should be monitored when bedaquiline is used. Bedaquiline comes with a black box warning because of an increase in all‑cause mortality, as well as prolongation of the QT interval.
In the clinical studies that have evaluated bedaquiline to date, it was noted that despite the improvement in sputum culture conversion, at the end of follow-up, 30 deaths had occurred in the clinical trial program in patients receiving bedaquiline compared with 6 in those receiving placebo. Detailed analyses were undertaken to ascertain the reasons for these deaths. Most of the deaths have appeared to have occurred after bedaquiline had been stopped, and to date, there has been no definitive relationship established between bedaquiline serum levels or QT interval prolongation in conjunction with these deaths. Nonetheless, given this increase in all-cause mortality, any patient receiving bedaquiline should be carefully monitored and be included in the patient registry monitoring users of this drug.
Given the increase in QT interval prolongation that has been observed with those patients receiving bedaquiline, EKGs should be monitored frequently. Bedaquiline should also not be used in conjunction with rifampin, rifapentine, or other strong inducers of the cytochrome P450 system.
EKG, electrocardiogram.
If bedaquiline is prescribed in a patient with multidrug-resistant TB, several important aspects of monitoring should be incorporated. The patient should be monitored on at least a weekly basis for adverse events, and given this increase in QT interval prolongation, EKGs should be obtained at a minimum at baseline, at 2 weeks, 12 weeks, and 24 weeks, with additional EKGs as needed.
In order to prevent cardiac toxicity, electrolytes including potassium, magnesium, and calcium should also be monitored at baseline and whenever clinically indicated, particularly if QT interval prolongation has been detected. All patients should be included in a registry for ongoing monitoring.
Bedaquiline has a very long terminal half-life of 4-5 months and should discontinued before other drugs in the regimen to avoid bedaquiline exposure system as monotherapy.
Rifamycins and other cytochrome P450 system inducers may reduce bedaquiline concentrations, and bioavailability is significantly affected by food intake.
TB, tuberculosis.
Let’s move on now to the next agent for which there has been a great deal of optimism. Delamanid is a derivative of metronidazole that works by inhibiting mycolic acid synthesis and has been shown in preclinical studies to have in vitro and in vivo activity against both drug-susceptible and drug-resistant strains of tuberculosis.
AE, adverse event; BR, background regimen; MDR, multidrug resistant; TB, tuberculosis; WHO, World Health Organization.
This slide represents a multinational, randomized, double-blind placebo-controlled trial published in 2012 in the New England Journal of Medicine. Patients in this study were randomized to receive 2 months of delamanid at either of 2 doses or placebo, in conjunction with a WHO-optimized background regimen consisting of multiple other second-line agents. The primary endpoint was sputum culture conversion at 2 months.
The results are shown on the right side of the slide. Delamanid in either dose significantly increased the rate of sputum conversion vs placebo after 2 months of therapy. A total of 40% to 45% of individuals had culture conversion at 8 weeks when delamanid was included in the regimen compared with 29% of individuals receiving placebo. Adverse events were graded as mild to moderate and were similar among all groups, although it was noted that QT interval prolongation occurred more frequently in those receiving delamanid.
EMEA, European Medicines Agency; MDR, multidrug resistant; TB, tuberculosis.
Based on these initial data on safety and efficacy, the European Medicines Agency in November 2013 granted the makers of delamanid conditional marketing authorization for use of the drug in the treatment of MDR-TB. The initial recommendation was that delamanid may be used as part of an appropriate combination regimen for pulmonary MDR-TB in adults when an effective treatment regimen cannot otherwise be composed because of resistance or tolerability.
AE, adverse event; MDR, multidrug resistant; QD, once daily; TB, tuberculosis.
Linezolid, an oxazolidinone, has been available since 2000 for the treatment of drug-resistant Gram-positive infections. However, it has become increasingly recognized that this drug has good activity against MDR-TB in vitro and in animal studies.
Its use in TB, however, has often been limited due to long-term toxicities, including bone marrow suppression and neuropathy. However, retrospective chart reviews and multiple case series have shown that linezolid, when used at a dose of 600 mg once daily as part of an MDR-TB regimen can result in improved treatment outcomes including culture conversion, without a significant increase in adverse events.
QD, once daily; TB, tuberculosis; XDR, extensively drug resistant.
A phase II trial of linezolid in difficult-to-treat patients with XDR-TB has been completed in South Korea with promising results. Individuals with XDR-TB that were failing their background regimens were randomized to receive either linezolid 600 mg once daily either immediately or delayed by 2 months. There was a second randomization after smear conversion to either continue linezolid at 600 mg once daily or to reduce the dose to linezolid 300 mg once daily.
AE, adverse event; d/c, discontinued; LZD, linezolid; TB, tuberculosis; XDR, extensively drug resistant.
This slide shows the results: 87% of individuals with XDR-TB who had been failing their current regimen achieved sputum culture conversion within 6 months when linezolid was added to their treatment regimen.
Although 82% of individuals did experience significant adverse events to linezolid, only 3 patients had dose-limiting toxicity that required discontinuation of their therapy. Interestingly, patients that received linezolid at the lower dose of 300 mg daily after the second randomization had fewer adverse events. However, 4 patients acquired linezolid resistance—2 in the 300-mg group and 2 in the 600-mg group.
These data suggest that linezolid may be an effective additional agent in our MDR- and XDR-TB armamentarium.
LZD, linezolid; MOA, mechanism of action.
Sutezolid is a drug similar to linezolid. It has the same mechanism and action as linezolid but in mouse models appears to have a higher barrier to resistance and may be more potent. It also appears in initial studies to confer less toxicity than linezolid. Early bactericidal activity data are now available.
ALT, alanine aminotransferase; BID, twice daily; CFU, colony-forming units; QD, once daily; HREZ, isoniazid/rifampin/ethambutol/pyrazinamide; ULN, upper limit of normal.
These are data in which individuals with tuberculosis who were given a regimen of sutezolid. This study suggested that sutezolid does have good early bactericidal activity at 14 days, at doses of 1200 mg once daily and 600 mg twice daily, but the twice-daily dose appears to be more effective.
TB, tuberculosis.
The last agent that we will discuss in this lecture is known as PA-824. This agent has some level cross-resistance with delamanid but appears to be potent and synergistic with other drugs.
BDQ, bedaquiline; CFZ, clofazimine; INH, isoniazid; MXF, moxifloxacin; Pa, PA-824; PZA, pyrazinamide; RIF, rifampin; SUT, sutezolid; TB, tuberculosis; Tx, treatment.
These data are from murine studies, using this drug in combination with other TB agents. On the left is a table in which PA-824 was combined with moxifloxacin and pyrazinamide. At 4 months, 100% of mice receiving PA-824, moxifloxacin, and pyrazinamide achieved cure compared with only 50% of those receiving the conventional first-line drug regimen of rifampin, isoniazid, and pyrazinamide.
In the study on the right side of the slide, PA-824 was combined with bedaquiline and sutezolid as part of a novel 3-drug backbone. By 4 months (highlighted here with the red circle), none of patients receiving this novel combination of drugs had relapsed. This suggests that this combination may represent a universally active short-course regimen.
TB, tuberculosis.
PA-824 has also been studied in early bactericidal activity trials in humans. This is a phase II trial in TB patients with smear-positive, culture-positive drug-sensitive TB who were randomized to receiving 1 of 6 different regimens, including regimens with PA-824.
CFU, colony-forming units; RHEZ, rifampin/isoniazid/ethambutol/pyrazinamide; PZA, pyrazinamide; TB, tuberculosis.
The novel combination of PA-824, pyrazinamide, and moxifloxacin showed the greatest reduction in colony-forming units of M tuberculosis in sputum by Day 14 of any of the drug regimens studied that are listed on this slide, including the standard regimen of isoniazid, rifampin, ethambutol, and pyrazinamide.
ART, antiretroviral therapy; DOT, directly observed therapy; MDR, multidrug resistant; TB, tuberculosis.
We will end our discussion of treatment and prevention of MDR-TB by examining steps that can be taken to prevent MDR-TB spread and/or progression to MDR-TB disease. Perhaps the first step in prevention of MDR-TB is to ensure adequate and proper treatment of drug-sensitive TB to prevent selection of further drug resistance. This means ensuring adequate TB treatment and drug supplies and ensuring high levels of drug adherence, which can often be accomplished with directly observed therapy. When possible, drug-resistance testing before treatment should be undertaken to avoid inclusion of drugs in inadequate regimens that may result in further evolution of drug resistance. When possible, particularly in conjugate living facilities or in hospital settings, airborne infection control should be undertaken to prevent onward spread of MDR-TB strains.
MDR, multidrug resistant; TB, tuberculosis; TST, tuberculin skin test.
In the event that individuals are infected latently with MDR-TB, preventive therapy can be considered. There is currently no consensus on acceptable preventive therapy regimens, and there have been no controlled trials to offer guidance as to which drugs would be best to treat latent MDR-TB. However, there are numerous cohorts that offer us some insights.
In the study represented on this slide, 232 contacts of 5 patients with 2 MDR-TB strains were followed as part of contact investigations conducted by the CDC in Micronesia. In total, 119 individuals were diagnosed with latent tuberculosis after a positive skin test, and of those, 105 accepted preventative therapy. The index case strains were resistant to first-line drugs and some second-line drugs, as indicated on this slide. The latent MDR-TB regimens that were offered as part of this contact investigation were a fluoroquinolone, either in combination with ethionamide or ethambutol.
Interestingly, at the time of follow-up to date, no cases of MDR-TB have occurred in individuals that were offered preventive therapy. By contrast, 28 other individuals that did not receive any preventive therapy—including 2 who declined therapy that had been identified as part of the initial contact investigation—have gone on to develop MDR-TB.
Whereas there is no consensus recommendation, often a fluoroquinolone, in combination with a second agent, has been utilized based on this experience for the treatment of MDR-TB in high-risk individuals.
FDA, US Food and Drug Administration; MDR, multidrug resistant; TB, tuberculosis.
In conclusion, the current therapeutic approaches to MDR-TB therapy are long and confer a significant amount of toxicity. Bedaquiline is the first drug with a novel mechanism of action that has now been approved by the FDA for MDR-TB therapy since 1971. Other agents including delamanid also show promise, and delamanid has recently been approved by the European Medicines Agency. Multiple new drugs are in the pipeline that offer opportunities for new combinations. Successful eradication of MDR-TB in the future is likely to make use of these new drug regimens that may potentially be used for shorter periods of time.