Clinical Pharmacology for Sirturo
Mechanism Of Action
Bedaquiline is a diarylquinoline antimycobacterial drug [see Microbiology].
Pharmacodynamics
Bedaquiline has activity against M. tuberculosis. The major 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-fold to 6-fold lower) compared to the parent compound. However, M2 plasma concentrations are correlated with QTc prolongation.
Cardiac Electrophysiology
In Study 1, the largest mean increase in QTc during the 24 weeks of SIRTURO treatment was 16 ms compared to 6 ms with placebo treatment (at Week 18). After SIRTURO treatment ended, the QTc gradually decreased, and the mean value was similar to that in the placebo group by study Week 60.
In Study 4, the mean change from baseline in QTc for the SIRTURO-containing arm was 22 ms (95 % CI: 19; 24) at Week 2 (i.e., the end of the 2-week SIRTURO loading period), and 8 ms (95 % CI: 2; 13) in the levofloxacin-containing control arm subgroup.
In Study 4, the mean QTc increased from baseline over the first 12 weeks for both SIRTURO and the non-SIRTURO containing control arm, when a plateau was reached. The largest mean QTc increase from baseline was 35 ms (95% CI: 32 to 38 ms) for the SIRTURO-containing arm and 28 ms (95% CI: 21 to 34 ms) for the levofloxacin-containing control arm subgroup [see Warnings and Precautions (5.1) and Drug Interactions (7.3)].
Pharmacokinetics
Pharmacokinetics (PK) parameters
The pharmacokinetic properties of bedaquiline are summarized in Table 5 as mean (SD) in adult patients.
Table 5: Model-Derived Pharmacokinetic Parameters of Bedaquiline and M2 (mean [SD]) after Multiple Doses of SIRTURO at the Recommended Dosing Regimen
| Pharmacokinetic Parameters |
Bedaquiline |
| Absorption |
| Food effect |
High fat meal (22 grams of fat, 558 total Kcal) increased Cmax and AUC by 2-fold. SIRTURO should be taken with food to enhance its oral bioavailability. |
| Tmax |
Around 5 hours after single oral dose administration of SIRTURO |
| Cmax of bedaquiline |
Week 2: 3060 (1124) ng/mL |
| Week 24: 1838 (684) ng/mL |
| Week 40: 1787 (666) ng/mL |
| Cmax of M2 |
Week 2: 326 (135) ng/mL |
| Week 24: 234 (85) ng/mL |
| Week 40: 246 (103) ng/mL |
| Exposure |
| AUC168h of bedaquiline (AUC24h for Week 2) |
Week 2: 41510 (15064) ng•h/mL |
| Week 24: 163924 (55710) (ng•h/mL) |
| Week 40: 168376 (74476) ng•h/mL |
| AUC168h of M2 (AUC24h for Week 2) |
Week 2: 7267 (3029) ng•h/mL |
| Week 24: 37255 (13998) ng•h/mL |
| Week 40: 39540 (17220) ng•h/mL |
| Distribution |
| Percent bound to human plasma protein |
greater than 99.9%. |
| apparent central volume of distribution |
approximately 117 Liters. |
| Proportionality |
Cmax and AUC increased proportionally up 700 mg (1.75 times the 400 mg loading dose). |
| Elimination |
After reaching Cmax, bedaquiline concentrations decline tri-exponentially. |
| Apparent clearance of bedaquiline |
2.62 L/h |
| Apparent clearance of M2 |
4.95 L/h |
| Terminal half-life |
~ 5.5 months for both bedaquiline and N monodesmethyl metabolite (M2) |
| Metabolism |
Metabolized to the M2 by CYP3A4; Relative exposure M2 versus bedaquiline: 23%~31% |
| Excretion |
| Major route of excretion |
Fecal excretion is the major route of elimination |
| %Excreted unchanged in urine |
less than or equal to 0.001% of the dose in clinical studies |
| SD=Standard Deviation |
Specific Populations
Hepatic Impairment
After single-dose administration of 400 mg SIRTURO to 8 adult patients with moderate hepatic impairment (Child-Pugh B), mean exposure to bedaquiline and M2 (AUC672h) was approximately 20% lower compared to healthy adults. SIRTURO has not been studied in patients with severe hepatic impairment [see WARNINGS AND PRECAUTIONS and Use In Specific Populations].
Renal Impairment
SIRTURO has mainly been studied in adult patients with normal renal function. Renal excretion of unchanged bedaquiline is not substantial (less than or equal to 0.001%).
In a population pharmacokinetic analysis of adult TB patients treated with SIRTURO 200 mg three times per week, creatinine clearance was not found to influence the pharmacokinetic parameters of bedaquiline. It is therefore not expected that mild or moderate renal impairment will have a clinically relevant effect on the exposure to bedaquiline. However, in patients with severe renal impairment or end-stage renal disease requiring hemodialysis or peritoneal dialysis bedaquiline concentrations may be increased due to alteration of drug absorption, distribution, and metabolism secondary to renal dysfunction. As bedaquiline is highly bound to plasma proteins, it is unlikely that it will be significantly removed from plasma by hemodialysis or peritoneal dialysis [see Use In Specific Populations].
Sex
In a population pharmacokinetic analysis of adult TB patients treated with SIRTURO no clinically relevant difference in exposure between men and women were observed.
Race/Ethnicity
In a population pharmacokinetic analysis of adult TB patients treated with SIRTURO, systemic exposure (AUC) to bedaquiline was found to be 34% lower in Black patients than in patients from other race categories. This lower bedaquiline exposure in Black patients was not associated with lower efficacy in clinical trials.
HIV Coinfection
Bedaquiline exposure in patients coinfected with HIV was similar to that of patients not infected with HIV.
Geriatric Population
There are limited data on the use of SIRTURO in TB patients 65 years of age and older.
In a population pharmacokinetic analysis of adult TB patients treated with SIRTURO, age was not found to influence the pharmacokinetics of bedaquiline. In five patients 65 to 69 years of age, the systemic bedaquiline exposure was similar to that in other adults.
Pediatric Population
Pediatric patients 12 years to less than 18 years of age with TB due to M. tuberculosis resistant to at least rifampin
The pharmacokinetic parameters of bedaquiline in 15 pediatric patients (body weight at baseline: 38 to 75 kg) who received the same adult dosage regimen of SIRTURO (400 mg once daily for the first two weeks and 200 mg three times/week for the following 22 weeks) in combination with a background regimen were comparable to those in adults. There was no impact of body weight on bedaquiline pharmacokinetics in this cohort.
Pediatric patients 5 years to less than 12 years of age with TB due to M. tuberculosis resistant to at least rifampin
Fifteen pediatric patients (body weight at baseline: 14 to 36 kg) received SIRTURO (200 mg once daily for the first two weeks and 100 mg three times/week for the following 22 weeks) in combination with a background regimen. Of these 15 pediatric patients, complete pharmacokinetic data were obtained for 10 patients at the aforementioned dosage regimen of SIRTURO. In nine of these 10 pediatric patients who weighed at least 15 kg at baseline, the mean bedaquiline Cmax and AUC24h were similar to that of adult patients receiving the recommended adult dosage regimen. In one of these 10 pediatric patients who weighed 14 kg at baseline, the bedaquiline mean Cmax and AUC24h were 3.8-fold and 2.6-fold, respectively, higher than the mean Cmax and AUC24h in adult patients administered the recommended adult dosage regimen. The clinical significance of this higher pharmacokinetic plasma exposure in this one pediatric patient is not known [see Use in Specific Populations (8.4)].
See Table 6 for a summary of the pharmacokinetic parameters in pediatric patients 5 years to less than 18 years of age.
Table 6: Pharmacokinetic Parameters of Bedaquiline Following Repeat Dose Administration of SIRTURO to Pediatric Patients 5 to Less than 18 Years of Age at Week 12 Administered with Food (N=25)
| Pharmacokinetic Parameter |
Bedaquiline Mean (SD) |
14 years to less than 18 years
(N=15) |
5 years to less than 12 years
(N=10) |
| AUC24h (ng•h/mL) |
26300 (10,300) |
32200 (16,300) |
| Cmax (ng/mL) |
1800 (736) |
2430 (1,670) |
| Tmax (h)* |
4 (2-8) |
4 (2-8) |
| Cmin (ng/mL) |
544 (263) |
461 (173) |
SD=Standard Deviation
* Median (range) |
Drug Interactions Studies
In vitro, bedaquiline did not significantly inhibit the activity of the following CYP450 enzymes that were tested: CYP1A2, CYP2A6, CYP2C8/9/10, CYP2C19, CYP2D6, CYP2E1, CYP3A4, CYP3A4/5 and CYP4A, and it does not induce CYP1A2, CYP2C9, CYP2C19, or CYP3A4 activities.
Bedaquiline is an in vitro substrate of CYP3A4, and because of this, the following clinical drug interaction studies were performed.
Clinical Studies
Ketoconazole
Coadministration of multiple-dose bedaquiline (400 mg once daily for 14 days) and multiple-dose ketoconazole (once daily 400 mg for 4 days) in healthy adult subjects increased the AUC24h, Cmax and Cmin of bedaquiline by 22% [90% CI (12; 32)], 9% [90% CI (-2, 21)] and 33% [90% CI (24, 43)] respectively [see DRUG INTERACTIONS].
Clarithromycin
Coadministration of a single 100 mg dose of SIRTURO with clarithromycin at steady-state in healthy adults increased the mean [90% CI] bedaquiline exposure AUC240h by 14% [9%;19%].
Clofazimine
In Study 3, long-term coadministration of clofazimine and SIRTURO, as part of a combination therapy for up to 24 weeks, did not affect bedaquiline exposure.
Rifampin
In a drug interaction study of single-dose 300 mg bedaquiline and multiple-dose rifampin (once daily 600 mg for 21 days) in healthy adult subjects, the exposure (AUC) to bedaquiline was reduced by 52% [90% CI (-57; -46)] [see DRUG INTERACTIONS].
Antimicrobial Agents
The combination of multiple-dose bedaquiline 400 mg once daily with multiple-dose isoniazid/pyrazinamide (300 mg/2000 mg once daily) in healthy adult subjects did not result in clinically relevant changes in the exposure (AUC) to bedaquiline, isoniazid or pyrazinamide [see DRUG INTERACTIONS].
In a placebo-controlled study in adult patients with TB, no major impact of coadministration of bedaquiline on the pharmacokinetics of ethambutol, kanamycin, pyrazinamide, ofloxacin or cycloserine was observed.
Lopinavir/ritonavir
In a drug interaction study in healthy adults of single-dose bedaquiline (400 mg) and multiple-dose lopinavir (400 mg)/ritonavir (100 mg) given twice daily for 24 days, the mean AUC of bedaquiline was increased by 22% [90% CI (11; 34)] while the mean Cmax was not substantially affected. In Study 4, coadministration of SIRTURO with lopinavir/ritonavir in patients coinfected with HIV increased bedaquiline exposure, with an estimated 68% [90% CI (29%; 117%)] increase in mean AUC168h at Week 24 and 72% [90% CI (32%; 123%)] at Week 40, in HIV-positive Black patients treated with lopinavir/ritonavir (N=16) compared to HIV-positive and -negative Black patients without lopinavir/ritonavir (N=67) treatment [see DRUG INTERACTIONS].
Nevirapine
Coadministration of multiple-dose nevirapine 200 mg twice daily for 4 weeks in HIV-infected adult patients with a single 400 mg dose of bedaquiline did not result in clinically relevant changes in the exposure to bedaquiline. In Study 4, coadministration of nevirapine and SIRTURO as part of combination therapy for up to 40 weeks in patients coinfected with HIV, resulted in a 29% [90% CI (0; 50%)] decrease in bedaquiline exposure (AUC168h).
Efavirenz
Coadministration of a single dose of bedaquiline 400 mg and efavirenz 600 mg daily for 27 days to healthy adult volunteers resulted in approximately a 20% decrease in the AUCinf of bedaquiline; the Cmax of bedaquiline was not altered. The AUC and Cmax of the primary metabolite of bedaquiline (M2) were increased by 70% and 80%, respectively. The effect of efavirenz on the pharmacokinetics of bedaquiline and M2 following steady-state administration of bedaquiline has not been evaluated [see DRUG INTERACTIONS].
Microbiology
Mechanism Of Action
SIRTURO is a diarylquinoline antimycobacterial drug that inhibits mycobacterial ATP (adenosine 5'-triphosphate) synthase, by binding to subunit c of the enzyme that is essential for the generation of energy in M. tuberculosis.
Resistance
A potential for development of resistance to bedaquiline in M. tuberculosis exists. Modification of the atpE target gene, and/or upregulation of the MmpS5-MmpL5 efflux pump (Rv0678 mutations) have been associated with increased bedaquiline MIC values in isolates of M. tuberculosis. 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 micrograms per mL. 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 micrograms per mL.
M. tuberculosis isolates that had developed at least a 4-fold increase in bedaquiline MIC were associated with mutations in Rv0678 gene that lead to upregulation of the MmpS5-MmpL5 efflux pump. Isolates with these efflux-based mutations are less susceptible to clofazimine. Isolates that are phenotypically resistant to bedaquiline should be tested for cross-resistance to clofazimine, if clofazimine is being considered as part of the treatment regimen. In Studies 2, 3 and 4 there was no clear relationship between the presence of Rv0678 mutations at baseline and treatment outcome.
Antimicrobial Activity
SIRTURO has been shown to be active in vitro and in clinical infections against most isolates of M. tuberculosis [see INDICATIONS and Clinical Studies].
Susceptibility Testing
MICs for baseline M. tuberculosis isolates from patients in Studies 1 and 3 and their sputum culture conversion rates at Week 24 and from patients in the 40-week SIRTURO arm of Study 4 at Week 76 are shown in Table 7 below. Based on the available data, there was no relationship between poor microbiological outcomes and baseline bedaquiline MIC.
Table 7: Culture Conversion Rates in SIRTURO Treatment Groups at Week 24 (Study 1 and 3) and at Week 76 (Study 4), by Baseline Bedaquiline MIC (mITT population)a
| Baseline Bedaquiline MIC (micrograms/mL) |
SIRTURO Treatment Group 24-Week Culture Conversion Rate (Study 1 and Study 3)
n/N (%) |
SIRTURO Treatment Group 76-Week Culture Conversion Rate (Study 4, 40-Week Arm)b
n/N (%) |
| ≤ 0.008 |
2/2 (100) |
5/5 (100) |
| 0.015 |
13/15 (86.7) |
26/26 (100) |
| 0.03 |
36/46 (78.3) |
67/69 (97.1) |
| 0.06 |
82/107 (76.6) |
51/51 (100) |
| 0.12 |
36/42 (85.7) |
20/20 (100) |
| 0.25 |
3/4 (75.0) |
2/2 (100) |
| 0.5 |
5/6 (83.3) |
0 |
| ≥ 1 |
0/1 (0) |
0 |
N=number of patients with data per baseline BDQ MIC category; n=number of patients with culture conversion; MIC=minimum inhibitory concentration
a 7H11 agar. Patients who prematurely discontinued were categorized as culture converted (or not) based on the available data. All available data were utilized regardless of changes in treatment.
b In addition, at Week 76 in the 40-week SIRTURO arm, there were 6 patients for whom no baseline MIC data were available. All 6 patients culture converted. |
Nineteen patients in the efficacy population of Study 3 had bedaquiline susceptibility testing results of paired (baseline and post-baseline, all of which were at Week 24 or later) genotypically identical M. tuberculosis isolates. Twelve of the 19 had a post-baseline ≥4-fold increase in bedaquiline MIC. Whole genome sequencing of nine of these 12 post-baseline isolates was done and no mutations were found in the ATP synthase operon. All nine were found to have a mutation in Rv0678. Eleven of the twelve (11/12) increases in bedaquiline MIC were seen in patients with isolates that also demonstrated increase MICs to fluoroquinolones and/or second-line injectables.
Based on available data, response rate (culture conversion at Week 120 endpoint) was similar in patients with ≥4-fold increases in bedaquiline MIC (5/12) and patients with <4-fold increases (3/7).
In the 40-week SIRTURO arm of Study 4, paired isolates (baseline and postbaseline, genotypically identical) susceptibility testing (MIC) results were available for 30 of 196 patients in the mITT population. At Week 132, three of five patients with a ≥4-fold increase in bedaquiline MIC and 25 of 25 patients with <4-fold increases had culture converted. Similarly, in the 28-week arm of Study 4, for 25 of 134 patients in the mITT population with paired isolates, two of four patients, with a ≥4-fold increase in bedaquiline MIC and 20 of 21 patients with <4-fold increases had culture converted. Based on the limited data, there was no clear relationship between bedaquiline MIC and microbiological outcomes.
For specific information regarding susceptibility test criteria and associated test methods and quality control standards recognized by FDA for this drug, please see: www.fda.gov/STIC.
Animal Toxicology And/Or Pharmacology
Bedaquiline is a cationic, amphiphilic drug that induced phospholipidosis (at almost all doses, even after very short exposures) in drug-treated animals, mainly in cells of the monocytic phagocytic system (MPS). All species tested showed drug-related increases in pigment-laden and/or foamy macrophages, mostly in the lymph nodes, spleen, lungs, liver, stomach, skeletal muscle, pancreas and/or uterus. After treatment ended, these findings were slowly reversible. Muscle degeneration was observed in several species at the highest doses tested. For example, the diaphragm, esophagus, quadriceps and tongue of rats were affected after 26 weeks of treatment at doses similar to clinical exposures based on AUC comparisons. These findings were not seen after a 12-week, treatment-free, recovery period and were not present in rats given the same dose biweekly. Degeneration of the fundic mucosa of the stomach, hepatocellular hypertrophy and pancreatitis were also seen.
Clinical Studies
Adult Patients
Study 1 (NCT00449644, Stage 2) was a placebo-controlled, double-blind, randomized trial conducted in patients with newly diagnosed sputum smear-positive pulmonary TB due to M. tuberculosis resistant to at least rifampin and isoniazid. Patients were randomized to receive a combination of SIRTURO or placebo with five other antimycobacterial drugs (i.e., ethionamide, kanamycin, pyrazinamide, ofloxacin, and cycloserine/terizidone or available alternative) for a total duration of 18 to 24 months or at least 12 months after the first confirmed negative culture. Treatment was 24 weeks of treatment with SIRTURO 400 mg once daily for the first two weeks followed by 200 mg three times per week for 22 weeks or matching placebo for the same duration. Overall, 79 patients were randomized to the SIRTURO arm and 81 to the placebo arm. A final evaluation was conducted at Week 120.
Sixty-seven patients randomized to SIRTURO and 66 patients randomized to placebo had confirmed pulmonary TB due to M. tuberculosis resistant to at least rifampin and isoniazid, based on susceptibility tests (taken prior to randomization) or medical history if no susceptibility results were available, and were included in the efficacy analyses. Demographics were as follows: 64% of the study population was male, with a median age of 33 years, 38% were Black, 17% were Hispanic, 11% were White, 11% were Asian, and 24% were of another race; and 14% were HIV-positive (median CD4 cell count 446 cells/μL). Most patients had cavitation in one lung (62%); and 20% of patients had cavitation in both lungs.
Time to sputum culture conversion was defined as the interval in days between the first dose of study drug and the date of the first of two consecutive negative sputum cultures collected at least 25 days apart during treatment. In this trial, the SIRTURO treatment group had a decreased time to culture conversion and improved culture conversion rates compared to the placebo treatment group at Week 24. Median time to culture conversion was 83 days for the SIRTURO treatment group compared to 125 days for the placebo treatment group. Table 8 shows the proportion of patients with sputum culture conversion at Week 24 and Week 120.
Table 8: Culture Conversion Status and Clinical Outcome at Week 24 and Week 120 in Study 1
| Microbiologic Status |
SIRTURO (24 weeks) + combination of other anti-mycobacterial drugs
N=67 |
Placebo (24 weeks) + combination of other anti-mycobacterial drugs
N=66 |
Difference
[95% CI]
p-value |
| Week 24 |
| Sputum Culture Conversion |
78% |
58% |
20.0%
[4.5%, 35.6%]
0.014 |
| Treatment failurea |
22% |
42% |
|
| Died |
1% |
0% |
|
| Lack of conversion |
21% |
35% |
|
| Discontinuation |
0% |
8% |
|
| Week 120b |
| Sputum Culture Conversion |
61% |
44% |
17.3%
[0.5%, 34.0%]
0.046 |
| Treatment failurea |
39% |
56% |
|
| Died |
12% |
3% |
|
| Lack of conversion/relapse |
16% |
35% |
|
| Discontinuation |
10% |
18% |
|
a A patient’s reason for treatment failure was counted only in the first row for which a patient qualifies.
b Patients received 24 weeks of SIRTURO or placebo for the first 24 weeks and received a combination of other antimycobacterial drugs for up to 96 weeks. |
Study 2 (NCT00449644, Stage 1) was a smaller placebo--controlled study designed similarly to Study 1 except that SIRTURO or placebo was given for only eight weeks instead of 24 weeks. Patients were randomized to either SIRTURO and other drugs used to treat pulmonary TB due to M. tuberculosis resistant to at least rifampin and isoniazid (SIRTURO treatment group) (n=23) or placebo and other drugs used to treat TB (placebo treatment group) (n=24). Twenty-one patients randomized to the SIRTURO treatment group and 23 patients randomized to the placebo treatment group had confirmed pulmonary TB due to M. tuberculosis resistant to at least rifampin and isoniazid based on patients’ baseline M. tuberculosis isolate obtained prior to randomization. The SIRTURO treatment group had a decreased time to culture conversion and improved culture conversion rates compared to the placebo treatment group at Week 8. At Weeks 8 and 24, the differences in culture conversion proportions were 38.9% [95% CI: (12.3%; 63.1%) and p-value: 0.004], 15.7% [95% CI (-11.9%; 41.9%) and p-value: 0.32], respectively.
Study 3 (NCT00910871) was a Phase 2b, uncontrolled study to evaluate the safety, tolerability, and efficacy of SIRTURO as part of an individualized treatment regimen in 233 patients with sputum smear positive (within 6 months prior to screening) pulmonary TB due to M. tuberculosis resistant to at least rifampin and isoniazid, including patients with isolates resistant to second-line injectables and/or fluoroquinolones. Patients received SIRTURO for 24 weeks in combination with antimycobacterial drugs. Upon completion of the 24-week treatment with SIRTURO, all patients continued to receive their background regimen in accordance with national TB program (NTP) treatment guidelines. A final evaluation was conducted at Week 120. Treatment responses to SIRTURO at Week 120 were generally consistent with those from Study 1.
Study 4 (NCT02409290) was a Phase 3, open-label, multicenter, active-controlled, randomized trial to evaluate the efficacy and safety of SIRTURO, coadministered 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 rifampin. Patients in whom the M. tuberculosis strain was known to be resistant at screening to second-line injectable agents or fluoroquinolones were excluded from enrollment. When phenotypic susceptibility testing of the baseline isolates became available post-randomization, patients infected with M. tuberculosis resistant to either second-line injectable agents or fluoroquinolones were kept in the study, however, those with M. tuberculosis resistant to both second-line injectables and fluoroquinolones were discontinued from the study.
Patients were randomized to one of four treatment arms:
- Arm A (N=32), the locally used treatment in accordance with 2011 WHO treatment guidelines with a recommended 20-month duration
- Arm B (N=202), a 40-week treatment of moxifloxacin (N=140) or levofloxacin (N=62), clofazimine, ethambutol, pyrazinamide, supplemented by injectable kanamycin, high-dose isoniazid and prothionamide in the first 16 weeks (intensive phase)
- Arm 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)
- Arm 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 eight weeks (intensive phase)
SIRTURO was administered 400 mg once daily for the first two weeks and 200 mg three times a week for the following 38 weeks (in Arm C) or 26 weeks (in Arm D).
All patients were to be followed up until study completion at Week 132. During study conduct, enrollment in Arms A and D was stopped due to changes in the standard of care for TB treatment. Patients already randomized to these study arms were to complete their assigned treatment and follow-up.
The primary objective was to assess whether the proportion of patients with a favorable efficacy outcome in Arm C was noninferior to that in Arm B at Week 76.
The primary efficacy outcome measure was the proportion of patients with a favorable outcome at Week 76. A favorable outcome at Week 76 was defined as the last two consecutive cultures being negative, and with no unfavorable outcome. An unfavorable outcome at Week 76 was assessed as a composite endpoint, covering both clinical and microbiological aspects such as changes in TB treatment, all-cause mortality, at least one of the last two culture results positive, or no culture results within the Week 76 window. In case of treatment failure, recurrence or serious toxicity on the allocated treatment, salvage treatment that could include SIRTURO was provided, based on investigator judgment.
The modified intent-to-treat population (mITT) was the primary efficacy population and included all randomized patients with a positive sputum culture for M. tuberculosis that was resistant to at least rifampin and not resistant to both second-line injectables and fluoroquinolones, based on susceptibility results (taken prior to randomization). A total of 196 and 187 patients were included in the mITT population in Arm C and Arm B, respectively. Overall, in both treatment arms, 62% were male of median age 33 years, 47% were Asian, 34% were Black, 19% were White, and 14% were HIV-coinfected. Most patients had lung cavitation (74%), with multiple cavities in 63% and 47% of patients in Arm C and Arm B, respectively. The baseline drug resistance profile of M. tuberculosis for Arms C and B were as follows: 14% had resistance to rifampin while susceptible to isoniazid, 75% had resistance to rifampin and isoniazid, and 10% had resistance to rifampin, isoniazid, and either a second-line injectable or a fluoroquinolone.
For efficacy analyses beyond Week 76, data collection was stopped at the point when the last recruited patient was projected to reach Week 96. The long-term efficacy data therefore include data up to at least Week 96 for all patients, and up to Week 132 for 146/196 (74.5%) patients in Arm C and 145/187 (77.5%) patients in Arm B.
Table 9 shows results for favorable and unfavorable outcomes at Week 76 and Week 132 in Study 4.
Table 9: Clinical Outcome at Week 76 and Week 132 in the mITT Population in Study 4
|
SIRTUROa
(N=196) |
Active Controlb
(N=187) |
| Favorable outcome at Week 76 n (%) |
162 (82.7) |
133 (71.1) |
| Differencec SIRTUROa vs Active Controlb (95% CI) |
11.0% (2.9%, 19.0%) |
| Unfavorable outcome at Week 76 n (%) |
34 (17.3) |
54 (28.9) |
| Reasons for unfavorable outcome through Week 76d |
| 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) |
| Favorable outcome at Week 132 n (%)e |
154 (78.6) |
129 (69.0) |
| Differencec SIRTUROa vs Active Controlc (95% CI) |
9.0% (0.6%,17.5%) |
mITT = modified intent-to-treat
a Arm 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 Arm 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 The adjusted difference in proportions was estimated using a stratified analysis of the risk difference from each stratum using Cochran Mantel-Haenszel weights. The analysis was stratified by randomization protocol and HIV and CD4 cell count status.
d Patients were classified by the first event that made the patient unfavorable. Of the patients with an unfavorable outcome at Week 76 in the control arm, 29 patients had a treatment modification from their allocated treatment that included SIRTURO as part of a salvage regimen.
e Week 132 outcome reflects efficacy follow up until the last patient reached Week 96. |
Pediatric Patients (5 years to less than 18 years of age)
The pediatric trial, (NCT02354014), was designed as a single-arm, open-label, multi-cohort trial to evaluate the pharmacokinetics, safety and tolerability of SIRTURO in combination with a background regimen in patients 5 to less than 18 years of age with confirmed or probable pulmonary TB due to M. tuberculosis resistant to at least rifampin.
Pediatric Patients (12 years to less than 18 years of age)
Fifteen patients 14 years to less than 18 years of age were enrolled in the first cohort. The median age was 16 years, 80% were female, 53% were Black, 33% were White and 13% were Asian. No patient 12 years to less than 14 years of age was enrolled in this cohort. SIRTURO was administered as 400 mg once daily for the first two weeks and 200 mg three times/week for the following 22 weeks using the 100 mg tablet.
In the subset of patients with culture positive pulmonary TB resistant to at least rifampin at baseline, treatment with bedaquiline resulted in conversion to a negative culture in 75.0% (6/8 patients) at Week 24.
Pediatric Patients (5 years to less than 12 years of age)
Fifteen patients 5 years to 10 years of age were enrolled in the second cohort. The median age was seven years, 60% were female, 60% were Black, 33% were White and 7% were Asian. No patient older than 10 years to less than 12 years of age was enrolled in this cohort. The body weight range was 14 kg to 36 kg; only one patient weighing 14 kg was enrolled. SIRTURO was administered as 200 mg once daily for the first two weeks and 100 mg three times/week for the following 22 weeks using the 20 mg tablet.
In the subset of patients with culture positive pulmonary TB resistant to at least rifampin at baseline, treatment with bedaquiline resulted in conversion to a negative culture in 100% (3/3 patients) at Week 24.