Optimizing Moxifloxacin Dose in MDR-TB Participants with or without Efavirenz Coadministration Using Population Pharmacokinetic Modeling

Moxifloxacin is included in some treatment regimens for drug-sensitive tuberculosis (TB) and multidrug-resistant TB (MDR-TB). Aiming to optimize dosing, we described moxifloxacin pharmacokinetic and MIC distribution in participants with MDR-TB. Participants enrolled at two TB hospitals in South Africa underwent intensive pharmacokinetic sampling approximately 1 to 6 weeks after treatment initiation. Plasma drug concentrations and clinical data were analyzed using nonlinear mixed-effects modeling with simulations to evaluate doses for different scenarios. We enrolled 131 participants (54 females), with median age of 35.7 (interquartile range, 28.5 to 43.5) years, median weight of 47 (42.0 to 54.0) kg, and median fat-free mass of 40.1 (32.3 to 44.7) kg; 79 were HIV positive, 29 of whom were on efavirenz-based antiretroviral therapy. Moxifloxacin pharmacokinetics were described with a 2-compartment model, transit absorption, and elimination via a liver compartment. We included allometry based on fat-free mass to estimate disposition parameters. We estimated an oral clearance for a typical patient to be 17.6 L/h. Participants treated with efavirenz had increased clearance, resulting in a 44% reduction in moxifloxacin exposure. Simulations predicted that, even at a median MIC of 0.25 (0.06 to 16) mg/L, the standard daily dose of 400 mg has a low probability of attaining the ratio of the area under the unbound concentration-time curve from 0 to 24 h to the MIC (fAUC_0-24)/MIC target of >53, particularly in heavier participants. The high-dose WHO regimen (600 to 800 mg) yielded higher, more balanced exposures across the weight ranges, with better target attainment. When coadministered with efavirenz, moxifloxacin doses of up to 1,000 mg are needed to match these exposures. The safety of higher moxifloxacin doses in clinical settings should be confirmed.

Identifying latent tuberculosis in high-risk populations: systematic review and meta-analysis of test accuracy

BACKGROUND: The relative accuracy of interferon-gamma release assays (IGRAs) and the tuberculin skin test (TST) in identifying latent tuberculosis infection (LTBI) is uncertain.OBJECTIVE: To perform a systematic review and meta-analysis to compare the sensitivity and specificity of IGRAs and TST for the prediction of progression to clinical tuberculosis (TB).METHODS: We searched electronic databases (e.g., MEDLINE and EMBASE) from December 2009 to September 2018 for prospective studies that followed up individuals who had undergone testing with commercial IGRAs and/or TST but had not received treatment based on the test result. The sensitivity and specificity estimates were pooled using a Bayesian bivariate random-effects model.RESULTS: Twenty-five studies, mostly with moderate to high risk of bias and a mean follow-up time ranging from 1 to 5 years were included. TST (10–15 mm) tended to have lower sensitivity and higher specificity than QuantiFERON® Gold In-Tube, T-SPOT®.TB and TST (5 mm). The evidence did not indicate that any test outperformed the others due to wide and overlapping 95% credible intervals.CONCLUSION: The evidence following individuals who had undergone testing for LTBI and had progressed to clinical TB is sparse. We did not find that IGRAs were superior to TST or vice versa; however, as our findings are based on a small number of studies with methodological limitations and great uncertainty around the pooled estimates, the results should be interpreted with caution.

Steady state pharmacokinetics of cycloserine in patients on terizidone for multidrug-resistant tuberculosis

SETTING

Terizidone/cycloserine (TRD/CS) is included in standard treatment regimens for multidrug-resistant tuberculosis (MDR-TB) in many countries. The steady state pharmacokinetics (PKs) of CS after TRD administration are not known.

OBJECTIVES AND DESIGN

We recruited in-patients treated with 250-750 mg oral TRD daily as part of standard treatment regimens for pulmonary MDR-TB in Cape Town, South Africa. Plasma CS assays were performed in samples taken pre-dose and at 2, 4, 6, 8 and 10 h post-dose. CS concentrations were measured using a validated liquid chromatography-tandem mass spectrometry method. Non-compartmental PK analyses were performed.

RESULTS

Of 35 participants enrolled, 22 were males, and 20 (57%) were infected with the human immunodeficiency virus; the median age was 37 years. The median duration on TRD at the time of sampling was 33 days (interquartile range [IQR] 28-39). The area under the concentration-time curve at 0-10 h (AUC0-10) was 319 μg.h/ml (IQR 267.5-378.7), and peak concentration was 38.1 μg/ml (IQR 32.6-47.2). On multiple regression, dose (mg/kg) was the only factor independently associated with AUC0-10.

CONCLUSION

Steady state concentrations of CS in patients treated with TRD for MDR-TB were higher than those reported with CS formulations. Our findings support once-daily dosing.

Effect of tablet crushing on drug exposure in the treatment of multidrug-resistant tuberculosis

SETTING: Treatment outcomes in multidrug-resistant tuberculosis (MDR-TB) are poor. Due to drug toxicity and a long treatment duration, approximately half of patients are treated successfully. Medication is often crushed for patients who have difficulty swallowing whole tablets. Whether crushing tablets affects drug exposure in MDR-TB treatment is not known.OBJECTIVE AND DESIGN: We performed a sequential pharmacokinetic study in patients aged >18 years on MDR-TB treatment at two hospitals in Cape Town, South Africa. We compared the bioavailability of pyrazinamide, moxifloxacin, isoniazid (INH), ethambutol and terizidone when the tablets were crushed and mixed with water before administration vs. swallowed whole. We sampled blood at six time points over 10 h under each condition separated by 2 weeks. Non-compartmental analysis was used to derive the key pharmacokinetic measurements.RESULTS: Twenty participants completed the study: 15 were men, and the median age was 31.5 years. There was a 42% reduction in the area under the curve AUC0-10 of INH when the tablets were crushed compared with whole tablets (geometric mean ratio 58%; 90%CI 47-73). Crushing tablets of pyrazinamide, moxifloxacin, ethambutol and terizidone did not affect the bioavailability significantly.CONCLUSION: We recommend that crushing of INH tablets in the MDR-TB treatment regimen be avoided. Paediatric INH formulations may be a viable alternative if the crushing of INH tablets is indicated.

Quality assurance of rifampicin-containing fixed-drug combinations in South Africa: dosing implications

SETTING:

Rifampicin (RMP) drives treatment response in drug-susceptible tuberculosis. Low RMP concentrations increase the risk of poor outcomes, and drug quality needs to be excluded as a contributor to low RMP exposure.

OBJECTIVES AND DESIGN:

We performed an open-label, three-way cross-over study of three licensed RMP-containing formulations widely used in South Africa to evaluate the bioavailability of RMP in a two-drug fixed-dose combination tablet (2FDC) and a four-drug FDC (4FDC) against a single-drug reference. RMP dosed at 600 mg was administered 2 weeks apart in random sequence. Plasma RMP concentrations were measured pre-dose and 1, 2, 3, 4, 6, 8 and 12 h post-dose. The area under the concentration-time curve (AUC_0–12) of the FDCs was compared to the single drug reference. Simulations were used to predict the impact of our findings.

RESULTS:

Twenty healthy volunteers (median age 22.8 years, body mass index 24.2 kg/m²) completed the study. The AUC_0–12 of the 4FDC/reference (geometric mean ratio [GMR] 78%, 90%CI 69–89) indicated an average 20% reduction in RMP bioavailability in the 4FDC. The 2FDC/reference (GMR 104%, 90%CI 97–111) was bioequivalent. Simulations suggested dose adjustments to compensate for the poor bioavailability of RMP with the 4FDC, and revised weight-band doses to prevent systematic underdosing of low-weight patients.

CONCLUSION:

Post-marketing surveillance of in vivo bioavailability of RMP and improved weight band-based dosing are recommended.

Short- and long-term clinical outcomes of use of beta-interferon or glatiramer acetate for people with clinically isolated syndrome: a systematic review of randomised controlled trials and network meta-analysis

Background

Beta-interferon (IFN-β) and glatiramer acetate (GA) have been evaluated in people with clinically isolated syndrome (CIS) with the aim to delay a second clinical attack and a diagnosis of clinically definite multiple sclerosis (CDMS). We systematically reviewed trials evaluating the short- and long-term clinical effectiveness of these drugs in CIS.

Methods

We searched multiple electronic databases. We selected randomised controlled studies (RCTs) conducted in CIS patients and where the interventions were IFN-β and GA. Main outcomes were time to CDMS, and discontinuation due to adverse events (AE). We compared interventions using random-effect network meta-analyses (NMA). We also reported outcomes from long-term open-label extension (OLE) studies.

Results

We identified five primary studies. Four had open-label extensions following double-blind periods comparing outcomes between early vs delayed DMT. Short-term clinical results (double-blind period) showed that all drugs delayed CDMS compared to placebo. Indirect comparisons did not suggest superiority of any one active drug over another. We could not undertake a NMA for discontinuation due to AE. Long-term clinical results (OLE studies) showed that the risk of developing CDMS was consistently reduced across studies after early DMT treatment compared to delayed DMT (HR = 0.64, 95% CI 0.55, 0.74). No data supported the benefit of DMTs in reducing the time to, and magnitude of, disability progression.

Conclusions

Meta-analyses confirmed that IFN-β and GA delay time to CDMS compared to placebo. In the absence of evidence that early DMTs can reduce disability progression, future research is needed to better identify patients most likely to benefit from long-term DMTs.

Electronic supplementary material

The online version of this article (10.1007/s00415-018-8752-8) contains supplementary material, which is available to authorized users.

A systematic review of evidence on malignant spinal metastases: natural history and technologies for identifying patients at high risk of vertebral fracture and spinal cord compression

BACKGROUND

Spinal metastases can lead to significant morbidity and reduction in quality of life due to spinal cord compression (SCC). Between 5% and 20% of patients with spinal metastases develop metastatic spinal cord compression during the course of their disease. An early study estimated average survival for patients with SCC to be between 3 and 7 months, with a 36% probability of survival to 12 months. An understanding of the natural history and early diagnosis of spinal metastases and prediction of collapse of the metastatic vertebrae are important.

OBJECTIVES

To undertake a systematic review to examine the natural history of metastatic spinal lesions and to identify patients at high risk of vertebral fracture and SCC.

DATA SOURCES

The search strategy covered the concepts of metastasis, the spine and adults. Searches were undertaken from inception to June 2011 in 13 electronic databases [MEDLINE; MEDLINE In-Process & Other Non-Indexed Citations; EMBASE; Cochrane Database of Systematic Reviews; Cochrane Central Register of Controlled Trials (CENTRAL); Database of Abstracts of Reviews of Effects (DARE), NHS Economic Evaluation Database (NHS EED), HTA databases (NHS Centre for Reviews and Dissemination); Science Citation Index and Conference Proceedings (Web of Science); UK Clinical Research Network (UKCRN) Portfolio Database; Current Controlled Trials; ClinicalTrials.gov].

REVIEW METHODS

Titles and abstracts of retrieved studies were assessed by two reviewers independently. Disagreement was resolved by consensus agreement. Full data were extracted independently by one reviewer. All included studies were reviewed by a second researcher with disagreements resolved by discussion. A quality assessment instrument was used to assess bias in six domains: study population, attrition, prognostic factor measurement, outcome measurement, confounding measurement and account, and analysis. Data were tabulated and discussed in a narrative review. Each tumour type was looked at separately.

RESULTS

In all, 2425 potentially relevant articles were identified, of which 31 met the inclusion criteria. No study examined natural history alone. Seventeen studies reported retrospective data, 10 were prospective studies, and three were other study designs. There was one systematic review. There were no randomised controlled trials (RCTs). Approximately 5782 participants were included. Sample sizes ranged from 41 to 859. The age of participants ranged between 7 and 92 years. Types of cancers reported on were lung alone (n= 3), prostate alone (n= 6), breast alone (n= 7), mixed cancers (n= 13) and unclear (n= 1). A total of 93 prognostic factors were identified as potentially significant in predicting risk of SCC or collapse. Overall findings indicated that the more spinal metastases present and the longer a patient was at risk, the greater the reported likelihood of development of SCC and collapse. There was an increased risk of developing SCC if a cancer had already spread to the bones. In the prostate cancer studies, tumour grade, metastatic load and time on hormone therapy were associated with increased risk of SCC. In one study, risk of SCC before death was 24%, and 2.37 times greater with a Gleason score ≥ 7 than with a score of < 7 (p= 0.003). Other research found that patients with six or more bone lesions were at greater risk of SCC than those with fewer than six lesions [odds ratio (OR) 2.9, 95% confidence interval (CI) 1.012 to 8.35, p= 0.047]. For breast cancer patients who received a computerised tomography (CT) scan for suspected SCC, multiple logistic regression in one study identified four independent variables predictive of a positive test: bone metastases ≥ 2 years (OR 3.0 95% CI 1.2 to 7.6; p= 0.02); metastatic disease at initial diagnosis (OR 3.4, 95% CI 1.0 to 11.4; p= 0.05); objective weakness (OR 3.8, 95% CI 1.5 to 9.5; p= 0.005); and vertebral compression fracture on spine radiograph (OR 2.6, 95% CI 1.0 to 6.5; p= 0.05). A further study on mixed cancers, among patients who received surgery for SCC, reported that vertebral body compression fractures were associated with presurgery chemotherapy (OR 2.283, 95% CI 1.064 to 4.898; p= 0.03), cancer type [primary breast cancer (OR 4.179, 95% CI 1.457 to 11.983; p= 0.008)], thoracic involvement (OR 3.505, 95% CI 1.343 to 9.143; p= 0.01) and anterior cord compression (OR 3.213, 95% CI 1.416 to 7.293; p= 0.005).

LIMITATIONS

Many of the included studies provided limited information about patient populations and selection criteria and they varied in methodological quality, rigour and transparency. Several studies identified type of cancer (e.g. breast, lung or prostate cancer) as a significant factor in predicting SCC, but it remains difficult to determine the risk differential partly because of residual bias. Consideration of quantitative results from the studies does not easily allow generation of a coherent numerical summary, studies were heterogeneous especially with regard to population, results were not consistent between studies, and study results almost universally lacked corroboration from other independent studies.

CONCLUSION

No studies were found which examined natural history. Overall burden of metastatic disease, confirmed metastatic bone involvement and immediate symptomatology suggestive of spinal column involvement are already well known as factors for metastatic SCC, vertebral collapse or progression of vertebral collapse. Although we identified a large number of additional possible prognostic factors, those which currently offer the most potential are unclear. Current clinical consensus favours magnetic resonance imaging and CT imaging modalities for the investigation of SCC and vertebral fracture. Future research should concentrate on: (1) prospective randomised designs to establish clinical and quality-of-life outcomes and cost-effectiveness of identification and treatment of patients at high risk of vertebral collapse and SCC; (2) Service Delivery and Organisation research on magnetic resonance imaging (MRI) scans and scanning (in tandem with research studies on use of MRI to monitor progression) in order to understand best methods for maximising use of MRI scanners; and (3) investigation of prognostic algorithms to calculate probability of a specified event using high-quality prospective studies, involving defined populations, randomly selected and clearly identified samples, and with blinding of investigators.

FUNDING

This report was commissioned by the National Institute for Health Research Health Technology Assessment Programme NIHR HTA Programme as project number HTA 10/91/01.

Operationalizing early antiretroviral therapy in HIV-infected in-patients with opportunistic infections including tuberculosis

BACKGROUND

We describe the outcomes of a program in which antiretroviral therapy (ART) is offered to human immunodeficiency virus (HIV) infected patients in South Africa admitted with tuberculosis (TB) or other opportunistic infection (OI) as part of in-patient care.

METHODS

Patients admitted with HIV and concurrent TB or other OI were initiated on early in-patient ART. The primary and secondary endpoints were respectively 24-week mortality and 24-week virologic suppression. Multivariable logistic regression modeling explored the associations between baseline (i.e., pre-hospital discharge) characteristics and mortality at 24 weeks.

RESULTS

A total of 382 patients were prospectively enrolled (48% women, median age 37 years, median CD4 count 33 cells/mm(3)). Acute OIs were pulmonary TB, 39%; extra-pulmonary TB, 25%; cryptococcal meningitis (CM), 10%; and chronic diarrhea, 9%. The median time from admission to ART initiation was 14 days (range 4-32, IQR 11-18). At 24 weeks of follow-up, as-treated and intention-to-treat virologic suppression were respectively 57% and 93%. Median change in CD4 cell count was +100 cells/mm(3), overall 24-week mortality was 25% and loss to follow-up, 5%. Excess mortality was not observed among patients with CM who initiated early ART. A longer interval between admission and ART was associated with mortality (>21 days vs. <21 days after admission OR 2.1, 95%CI 1.2-4.0, P = 0.016).

CONCLUSIONS

For HIV-infected in-patients with TB or an acquired immune-deficiency syndrome defining OI, we demonstrate the operational feasibility of early ART initiation in in-patients.