Pharmacotherapeutic group: Antimycobacterials, drugs for treatment of tuberculosis, ATC code: J04AK05
Mechanism of action
Bedaquiline is a diarylquinoline. Bedaquiline specifically inhibits mycobacterial ATP (adenosine 5'-triphosphate) synthase, an essential enzyme for the generation of energy in M. tuberculosis. The inhibition of ATP synthase leads to bactericidal effects for both replicating and non-replicating tubercle bacilli.
Pharmacodynamic effects
Bedaquiline has activity against M. tuberculosis complex strains with a minimal inhibitory concentration (MIC) in the range of ≤0.008 to 0.25 mg/L. The N-monodesmethyl metabolite (M2) is not thought to contribute significantly to clinical efficacy given its lower average exposure (23% to 31%) in humans and lower antimycobacterial activity (3- to 6-fold lower) compared to the parent compound.
The intracellular bactericidal activity of bedaquiline in primary peritoneal macrophages and in a macrophage-like cell line was greater than its extracellular activity. Bedaquiline is also bactericidal against dormant (non-replicating) tubercle bacilli. In the mouse model for TB infection, bedaquiline has demonstrated bactericidal and sterilizing activities.
Bedaquiline is bacteriostatic for many non-tuberculous mycobacterial species. Mycobacterium xenopi, Mycobacterium novocastrense, Mycobacterium shimoidei, Mycobacterium flavescens and non-mycobacterial species are considered inherently resistant to bedaquiline.
Pharmacokinetic/pharmacodynamic relationship
Within the concentration range achieved with the therapeutic dose, no pharmacokinetic/pharmacodynamic relationship was observed in patients.
Mechanisms of resistance
Acquired resistance mechanisms that affect bedaquiline MICs include mutations in the atpE gene, which codes for the ATP synthase target, and in the Rv0678 gene, which regulates the expression of the MmpS5-MmpL5 efflux pump. Target-based mutations generated in preclinical studies lead to 8- to 133-fold increases in bedaquiline MIC, resulting in MICs ranging from 0.25 to 4 mg/L. Efflux-based mutations have been seen in preclinical and clinical isolates. These lead to 2- to 8-fold increases in bedaquiline MICs, resulting in bedaquiline MICs ranging from 0.25 to 0.5 mg/L. The majority of isolates that are phenotypically resistant to bedaquiline are cross-resistant to clofazimine. Isolates that are resistant to clofazimine can still be susceptible to bedaquiline.
The impact of high baseline bedaquiline MICs, the presence of Rv0678 based mutations at baseline, and/or increased post-baseline bedaquiline MICs on microbiological outcomes is unclear because of the low incidence of such cases in the clinical trials.
Susceptibility testing breakpoints
MIC (minimum inhibitory concentration) interpretive criteria for susceptibility testing have been established by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) for bedaquiline and are listed here: https://www.ema.europa.eu/documents/other/minimum-inhibitory-concentration-mic-breakpoints_en.xlsx.
Commonly susceptible species
Mycobacterium tuberculosis
Inherently resistant organisms
Mycobacterium xenopi
Mycobacterium novocastrense
Mycobacterium shimoidei
Mycobacterium flavescens
Non-mycobacterial species
Clinical efficacy and safety
A Phase IIb, placebo-controlled, double-blind, randomised trial (C208) evaluated the antibacterial activity, safety, and tolerability of SIRTURO in newly diagnosed adult patients with sputum smear-positive pulmonary TB due to M. tuberculosis resistant to at least rifampicin and isoniazid, including patients with resistance to second-line injectables or fluoroquinolones. Patients received SIRTURO (N = 79) or placebo (N = 81) for 24 weeks, both in combination with a preferred 5-drug background regimen (BR) consisting of ethionamide, kanamycin, pyrazinamide, ofloxacin, and cycloserine/terizidone. SIRTURO was administered as 400 mg once daily for the first 2 weeks and as 200 mg 3 times/week for the following 22 weeks. After the 24-week investigational period, the background regimen was continued to complete 18 to 24 months of total treatment. A final evaluation was conducted at Week 120. Main demographics for the ITT population were as follows: 63.1% were males, median age 34 years, 35% were Black, and 15% were HIV-positive. Cavitation in one lung was seen in 58% of patients, and in both lungs in 16%. For patients in the mITT population with full characterisation of resistance status, 76% (85/112) were infected with a M. tuberculosis strain resistant to rifampicin and isoniazid and 24% (27/112) with a M. tuberculosis strain also resistant to second-line injectables or fluoroquinolones.
The primary outcome parameter was the time to sputum culture conversion (i.e., the interval between the first SIRTURO intake and the first of two consecutive negative mycobacteria growth indicator tube (MGIT) cultures from sputum collected at least 25 days apart) during treatment with SIRTURO or placebo (median time to conversion was 83 days for the SIRTURO group, 125 days for the placebo group (hazard ratio, 95% CI: 2.44 [1.57; 3.80]), p <0.0001).
In the SIRTURO group, no or only minor differences in time to culture conversion and culture conversion rates were observed between patients with a M. tuberculosis strain resistant to rifampicin and isoniazid and patients with a M. tuberculosis strain also resistant to second-line injectables or fluoroquinolones.
Response rates at Week 24 and Week 120 (i.e., approximately6 months after stopping all therapy) are presented in Table 3.
Table 3: Culture Conversion Status in C208
| Culture Conversion Status, n (%) | mITT Population |
| N | SIRTURO/BR | N | Placebo/BR |
| Overall responder at Week 24 | 66 | 52 (78.8%) | 66 | 38 (57.6%) |
| Patients with a M. tuberculosis strain resistant to rifampicin and isoniazid | 39 | 32 (82.1%) | 45 | 28 (62.2%) |
| Patients with a M. tuberculosis strain resistant to rifampicin and isoniazid, and also to second-line injectables or fluoroquinolones | 15 | 11 (73.3%) | 12 | 4 (33.3%) |
| Overall non-respondera at Week 24 | 66 | 14 (21.2%) | 66 | 28 (42.4%) |
| Overall responder at Week 120 | 66 | 41 (62.1%) | 66 | 29 (43.9%) |
| Patients with a M. tuberculosis strain resistant to rifampicin and isoniazid | 39b | 27 (69.2%) | 46b,c | 20 (43.5%) |
| Patients infected with a M. tuberculosis strain resistant to rifampicin and isoniazid, and also to second-line injectables or fluoroquinolones | 15b | 9 (60.0%) | 12b | 5 (41.7%) |
| Overall non-respondera at Week 120 | 66 | 25 (37.9%) | 66 | 37 (56.1%) |
| Failure to convert | 66 | 8 (12.1%) | 66 | 15 (22.7%) |
| Relapsed | 66 | 6 (9.1%) | 66 | 10 (15.2%) |
| Discontinued but converted | 66 | 11 (16.7%) | 66 | 12 (18.2%) |
a Patients who died during the trial or discontinued the trial were considered as non-responders.
b Extent of resistance based on central laboratory drug susceptibility testing results was not available for 20 patients in the mITT population (12 in the SIRTURO group and 8 in the placebo group). These subjects were excluded from the subgroup analysis by extent of resistance of M. tuberculosis strain.
c Central laboratory drug susceptibility testing results became available for one additional placebo patient after the Week 24 interim analysis.
d Relapse was defined in the trial as having a positive sputum culture after or during treatment following prior sputum culture conversion.
During the trial, 12.7% (10/79) patients died in the SIRTURO treatment group (N=79) compared to 3.7% (3/81) patients in the placebo group (N=81). One death occurred during administration of SIRTURO. The median time to death for the remaining nine patients was 344 days after last intake of SIRTURO. In the SIRTURO treatment group, the most common cause of death as reported by the investigator was TB (5 patients). The causes of death in the remaining patients treated with SIRTURO varied. During the trial, there was no evidence of antecedent significant QTcF prolongation or clinically significant dysrhythmia in any of the patients who died.
Study C209 evaluated the safety, tolerability, and efficacy of 24 weeks treatment with open-label SIRTURO as part of an individualised treatment regimen in 233 adult patients who were sputum smear positive within 6 months prior to screening. This study included patients with M. tuberculosis strains of all three resistance categories (resistant to rifampicin and isoniazid, also resistant to second-line injectables or fluoroquinolones, and also resistant to second-line injectables and fluoroquinolones).
The primary efficacy endpoint was the time to sputum culture conversion during treatment with SIRTURO (median 57 days, for 205 patients with sufficient data). At Week 24, sputum culture conversion was seen in 163/205 (79.5%) patients. Conversion rates at Week 24 were highest (87.1%; 81/93) in patients with M. tuberculosis isolates resistant to only rifampicin and isoniazid, 77.3% (34/44) in patients with pulmonary TB due to M. tuberculosis resistant to rifampicin, isoniazid, second-line injectables or fluoroquinolones, and lowest (54.1%; 20/37) in patients with M. tuberculosis isolates resistant to rifampicin, isoniazid, second-line injectables and fluoroquinolones. Extent of resistance based on central laboratory drug susceptibility testing results was not available for 31 patients in the mITT population. These patients were excluded from the subgroup analysis by extent of resistance of M. tuberculosis strain.
At Week 120, sputum culture conversion was seen in 148/205 (72.2%) patients. Conversion rates at Week 120 were highest (73.1%; 68/93) in patients with M. tuberculosis isolates resistant to only rifampicin and isoniazid, 70.5% (31/44) in patients with pulmonary TB due to M. tuberculosis resistant to rifampicin, isoniazid, second-line injectables or fluoroquinolones and lowest (62.2%; 23/37) in patients with M. tuberculosis isolates resistant to rifampicin, isoniazid, second-line injectables and fluoroquinolones.
At both Week 24 and Week 120, responder rates were higher for patients on 3 or more active substances (in vitro) in their background regimen.
In the open‑label C209 trial, 6.9% (16/233) of patients died. The most common cause of death as reported by the investigator was TB (9 patients). Eight of nine patients who died of TB had not converted or had relapsed. The causes of death in the remaining patients varied.
STREAM Stage 2 was a Phase III, open-label, multicentre, active-controlled, randomised trial conducted to evaluate the efficacy and safety of SIRTURO co-administered with other oral anti-TB drugs for 40 weeks in patients with sputum smear-positive pulmonary TB caused by M. tuberculosis that was resistant to at least rifampicin, with or without resistance additionally to isoniazid and/or second-line injectable agents or fluoroquinolones (but not both).
Patients were randomised to one of four treatment groups:
• Group A (N=32), the locally used treatment in accordance with 2011 WHO treatment guidelines with a recommended 20-month duration
• Group B (N=202), a 40-week control treatment of moxifloxacin or levofloxacin, clofazimine, ethambutol, pyrazinamide, supplemented by injectable kanamycin, high-dose isoniazid, and prothionamide in the first 16 weeks (intensive phase)
• Group C (N=211), a 40-week, all-oral treatment of SIRTURO, levofloxacin, clofazimine, ethambutol, and pyrazinamide, supplemented by high-dose isoniazid and prothionamide in the first 16 weeks (intensive phase)
• Group D (N=143), a 28-week treatment consisting of SIRTURO, levofloxacin, clofazimine, and pyrazinamide supplemented by kanamycin injectable and a higher isoniazid dose for the first 8 weeks (intensive phase)
SIRTURO was administered as 400 mg once daily for the first 2 weeks and 200 mg 3 times/week for the following 38 weeks (in Group C) or 26 weeks (in Group D). Changes in treatment regimen were permitted at the discretion of the investigator in all groups.
Enrolment in Groups A and D was stopped prematurely due to changes in the standard of care for TB treatment.
The primary objective was to assess whether the proportion of patients with a favourable efficacy outcome in Group C was noninferior to that in Group B at Week 76.
The primary efficacy outcome measure was the proportion of patients with a favourable outcome at Week 76. A favourable outcome at Week 76 was defined as last 2 consecutive cultures negative and no unfavourable outcome. An unfavourable outcome at Week 76 encompassed clinically relevant changes in treatment, all-cause mortality, at least 1 of the last 2 culture results positive, or no culture results within the Week 76 window.
In the overall study population (N=588), 59.9 % were male, median age was 32.7 years, 47.3% were Asian, 36.6% were Black, 16.2% were White and 16.5% were HIV-coinfected. Most patients had cavitation (73.1%), with multiple cavities in 55.3% of patients. Of the 543 patients in the primary efficacy population (mITT population, defined as patients with a positive culture for M. tuberculosis at screening or randomisation), 12.5% had resistance to rifampicin while susceptible to isoniazid, 76.4% had resistance to at least rifampicin and isoniazid, and 11% had resistance to rifampicin, isoniazid and either second-line injectables or fluoroquinolones.
Table 4 shows the proportion of patients with a favourable or unfavourable outcome at Week 76 in the STREAM Stage 2 Phase II trial. The proportion of participants with a favourable outcome at Week 76 was 82.7% in Group C compared to 71.1% in Group B. The main reason for an unfavourable outcome in both groups was extension or modification of the assigned treatment regimen. Limitations of the study included its open-label design; changes to the allocated treatment regimens were permitted in case of treatment failure, recurrence or serious toxicity.
| Table 4: Primary Analysis in STREAM Stage 2 (Phase III Trial) |
| | mITT Population |
| SIRTUROa (N=196) | Active Controlb (N=187) |
| Favourable outcome at Week 76 n (%) | 162 (82.7) | 133 (71.1) |
| Unfavourable outcome at Week 76 n (%) | 34 (17.3) | 54 (28.9) |
| Reasons for unfavourable outcome through Week 76c |
| Treatment modified or extended | 16 (8.2) | 43 (23.0) |
| No culture results within Week 76 window | 12 (6.1%) | 7 (3.7) |
| Death through Week 76 | 5 (2.6) | 2 (1.1) |
| At least one of last 2 cultures positive at Week 76 | 1 (0.5) | 2 (1.1) |
| mITT = modified intent-to-treat a Group C 40-week, all-oral regimen of SIRTURO, levofloxacin, clofazimine, ethambutol, and pyrazinamide, supplemented by high-dose isoniazid and prothionamide in the first 16 weeks (intensive phase). b Group B 40-week control treatment of moxifloxacin or levofloxacin, clofazimine, ethambutol, pyrazinamide, supplemented by injectable kanamycin, high dose isoniazid and prothionamide in the first 16 weeks (intensive phase). c Patients were classified by the first event that made the patient unfavourable. Of the patients with an unfavourable outcome at Week 76 in the control group, 29 patients had a treatment modification from their allocated treatment that included SIRTURO as part of a salvage regimen. |
The frequency of deaths was similar across treatment groups through Week 132. In the 40-week SIRTURO group, 11/211 (5.2%) patients died; the most common cause of death was related to TB (5 patients). In the 40-week active control group, 8/202 (4.0%) patients died, including 4 of 29 patients who received SIRTURO as part of a salvage treatment; the most common cause of death was related to respiratory pathology. The adjusted difference in proportion of fatal adverse events between the 40-week SIRTURO group and the 40-week active control group was 1.2% [95% CI (-2.8%; 5.2%)].
Paediatric population
The pharmacokinetics, safety and tolerability of SIRTURO in combination with a background regimen were evaluated in trial C211, a single-arm, open-label multi-cohort Phase II trial in 45 patients with confirmed or probable pulmonary TB due to M. tuberculosis resistant to at least rifampicin.
Paediatric patients (12 years to less than 18 years of age)
Fifteen patients had a median age of 16 years (range: 14 to 17 years), weighed 38 to 75 kg, and were 80% female, 53% Black, 33% White and 13% Asian. The patients were to complete at least 24 weeks of treatment with SIRTURO administered as 400 mg once daily for the first 2 weeks and 200 mg 3 times/week for the following 22 weeks using 100 mg tablets.
In the subset of patients with MGIT culture positive pulmonary TB at baseline, treatment with a regimen including SIRTURO resulted in conversion to a negative culture in 87.5% (7/8 MGIT culture evaluable patients) at Week 24, which was sustained at Week 120.
Paediatric patients (5 years to less than 12 years of age)
Fifteen patients had a median age of 7 years (range: 5 to 10 years), weighed 14 to 36 kg, and were 60% female, 60% Black, 33% White and 7% Asian. The patients were to complete at least 24 weeks of treatment with SIRTURO administered as 200 mg once daily for the first 2 weeks and 100 mg 3 times/week for the following 22 weeks using 20 mg tablets.
In the subset of patients with MGIT culture positive pulmonary TB at baseline, treatment with a regimen including SIRTURO resulted in conversion to a negative culture in 100% (3/3 MGIT culture evaluable patients) at Week 24, which was sustained at Week 120.
Paediatric patients (2 years to less than 5 years of age)
Fifteen patients had a median age of 3.8 years (range: 2.0 to 4.9 years), weighed 10 to 16 kg, and were 47% female, 27% Black and 73% Asian. The patients were to complete at least 24 weeks of treatment with SIRTURO administered as 80 to 120 mg once daily for the first 2 weeks and 40 to 60 mg 3 times/week for the following 22 weeks based on weight, using 20 mg tablets.
In the one patient with MGIT culture positive pulmonary TB at baseline, treatment with a regimen including SIRTURO resulted in conversion to a negative culture (1/1 MGIT culture evaluable patients) at Week 24, which was sustained at Week 120.
The European Medicines Agency has deferred the obligation to submit the results of studies with SIRTURO in one or more subsets of the paediatric population in the treatment of M. tuberculosis resistant to at least rifampicin and isoniazid (see section 4.2 for information on paediatric use).