Colleen Hanrahan

Pharmacodynamics and pharmacokinetics of SQ109, a new diamine‐based antitubercular drug

1 SQ109 is a novel [1,2]‐diamine‐based ethambutol (EMB) analog developed from high‐throughput combinatorial screening. The present study aimed at characterizing its pharmacodynamics and pharmacokinetics. 2 The antimicrobial activity of SQ109 was confirmed in vitro (Mycobacterium tuberculosis‐infected murine macrophages) and in vivo (M. tuberculosis‐infected C57BL/6 mice) and compared to isoniazid (INH) and EMB. SQ109 showed potency and efficacy in inhibiting intracellular M. tuberculosis that was similar to INH, but superior to EMB. In vivo oral administration of SQ109 (0.1–25 mg kg−1 day−1) to the mice for 28 days resulted in dose‐dependent reductions of mycobacterial load in both spleen and lung comparable to that of EMB administered at 100 mg kg−1 day−1, but was less potent than INH at 25 mg kg−1 day−1. Monitoring of SQ109 levels in mouse tissues on days 1, 14 and 28 following 28‐day oral administration (10 mg kg−1 day−1) revealed that lungs and spleen contained the highest concentration of SQ109, at least 10 times above its MIC. 3 Pharmacokinetic profiles of SQ109 in mice following a single administration showed its Cmax as 1038 (intravenous (i.v.)) and 135 ng ml−1 (p.o.), with an oral Tmax of 0.31 h. The elimination t1/2 of SQ109 was 3.5 (i.v.) and 5.2 h (p.o.). The oral bioavailability was 4%. However, SQ109 displayed a large volume of distribution into various tissues. The highest concentration of SQ109 was present in lung (>MIC), which was at least 120‐fold (p.o.) and 180‐fold (i.v.) higher than that in plasma. The next ranked tissues were spleen and kidney. SQ109 levels in most tissues after a single administration were significantly higher than that in blood. High tissue concentrations of SQ109 persisted for the observation period (10 h). 4 This study demonstrated that SQ109 displays promising in vitro and in vivo antitubercular activity with favorable targeted tissue distribution properties.

Body mass index and risk of tuberculosis and death.

Background:High BMI has been shown to be protective against tuberculosis (TB) among HIV-uninfected individuals, as well as against disease progression and mortality among those with HIV. We examined the effect of BMI on all-cause mortality and TB incidence among a cohort of HIV-infected adults in Soweto, South Africa. Methods:A clinical cohort of 3456 HIV-infected adults from South Africa was prospectively followed from 2003 to 2008 with regular monitoring. The primary exposure was BMI and the outcomes of interest were all-cause mortality and a newly diagnosed episode of TB. Cox proportional hazard models assessed associations with risk of mortality or incident TB. Results:Incidence rates of mortality were 10.4/100 person-years for baseline BMI of 18.5 or less, 3.6/100 person-years for baseline BMI 18.6–25, 1.7/100 person-years for baseline BMI 25.1–30, and 1.6/100 person-years for baseline BMI more than 30. Compared to those with normal BMI, overweight and obese participants had a significantly reduced risk of mortality [adjusted hazard ratio 0.59 (95% confidence interval, CI 0.40–0.87) and 0.48 (95% CI 0.29–0.80), respectively]. Incidence rates of TB by baseline BMI were 7.3/100 person-years for underweight, 6.0/100 person-years for normal, 3.2/100 person-years for overweight, and 1.9/100 person-years for obese. Compared to those with normal BMI, those with overweight and obese BMI were at a significantly reduced risk of developing TB [adjusted hazard ratio 0.56 (95% CI 0.38–0.83) and 0.33 (95% CI 0.19–0.55), respectively]. Conclusion:HIV-infected individuals with obese and overweight BMI have a significantly reduced risk of both mortality and TB, after adjusting for HAART use and CD4 cell count.

Candidacy for Kidney Transplantation of Older Adults

To develop a prediction model for kidney transplantation (KT) outcomes specific to older adults with end‐stage renal disease (ESRD) and to use this model to estimate the number of excellent older KT candidates who lack access to KT.

Time to treatment and patient outcomes among TB suspects screened by a single point-of-care xpert MTB/RIF at a primary care clinic in Johannesburg, South Africa.

Introduction In December 2010, the World Health Organization recommended a single Xpert MTB/RIF assay as the initial diagnostic in people suspected of HIV-associated or drug resistant tuberculosis. Few data are available on the impact of this recommendation on patient outcomes. We describe the diagnostic follow-up, clinical characteristics and outcomes of a cohort of tuberculosis suspects screened using a single point-of-care Xpert. Methods Consecutive tuberculosis suspects at a primary care clinic in Johannesburg, South Africa were assessed for tuberculosis using point-of-care Xpert. Sputum smear microscopy and liquid culture were performed as reference standards. Xpert-negatives were evaluated clinically, and further assessed at the discretion of clinicians. Participants were followed for six months. Results From July-September 2011, 641 tuberculosis suspects were enrolled, of whom 69% were HIV-infected. Eight percent were positive by a single Xpert. Among 116 individuals diagnosed with TB, 66 (57%) were Xpert negative, of which 44 (67%) were empirical or radiological diagnoses and 22 (33%) were Xpert negative/culture-positive. The median time to tuberculosis treatment was 0 days (IQR: 0–0) for Xpert positives, 14 days (IQR: 5–35) for those diagnosed empirically, 14 days (IQR: 7–29) for radiological diagnoses, and 144 days (IQR: 28–180) for culture positives. Xpert negative tuberculosis cases were clinically similar to Xpert positives, including HIV status and CD4 count, and had similar treatment outcomes including mortality and time to antiretroviral treatment initiation. Conclusions In a high HIV-burden setting, a single Xpert identified less than half of those started on tuberculosis treatment, highlighting the complexity of TB diagnosis even in the Xpert era. Xpert at point-of-care resulted in same day treatment initiation in Xpert-positives, but had no impact on tuberculosis treatment outcomes or mortality.

Progression and regression of premalignant cervical lesions in HIV-infected women from Soweto: a prospective cohort.

Objective:To ascertain progression and regression of cervical dysplasia in HIV-infected women in Soweto. Design:Prospective cohort. Methods:Women attending an HIV wellness clinic were offered cervical smears as part of care; smears were assessed using the Bethesda system. Those with high-grade lesions or worse were referred for colposcopy. Progression analyses included women with at least two smears at least 5.5 months apart. Hazard ratios were used to ascertain predictors of progression. Results:Two thousand, three hundred and twenty-five women had a baseline smear; their median age and CD4 cell count was 32 years and 312 cells/μl, respectively; 17% were taking highly active antiretroviral therapy (HAART); 62, 20 and 14% had normal, low-grade squamous intraepithelial lesions (LSIL) or high-grade squamous intraepithelial lesions (HSIL), respectively. Of those with baseline normal or LSIL smears, 1074 had another smear; progression from normal to LSIL was 9.6/100 person-years (95% CI 8.3–11.1) and progression from normal or LSIL to HSIL was 4.6/100 person-years (95% CI 3.9–5.5). Of 225 women with LSIL at baseline and at least one subsequent smear at least 11.5 months later, 44.0% regressed to normal (21.2/100 person-years (95% CI 17.5–25.7)). Multivariate models suggested increasing risk for progression in women with CD4 cell count below 500 cells/μl and HAART may reduce the risk of progression [adjusted hazard ratio (aHR) 0.72 (0.52–0.99)]. Conclusion:HIV-infected women have high rates of prevalent and incident HSIL and LSIL with relatively low risk of regression to normal from LSIL. HAART appears to protect against progression. Our findings suggest cervical screening intervals should be less than 10 years – irrespective of age in women with CD4 cell counts below 500 cells/μl.

Determinants of PCR performance (Xpert MTB/RIF), including bacterial load and inhibition, for TB diagnosis using specimens from different body compartments

The determinants of Xpert MTB/RIF sensitivity, a widely used PCR test for the diagnosis of tuberculosis (TB) are poorly understood. We compared culture time-to-positivity (TTP; a surrogate of bacterial load), MTB/RIF TB-specific and internal positive control (IPC)-specific CT values, and clinical characteristics in patients with suspected TB who provided expectorated (n = 438) or induced sputum (n = 128), tracheal aspirates (n = 71), bronchoalveolar lavage fluid (n = 152), pleural fluid (n = 76), cerebral spinal fluid (CSF; n = 152), pericardial fluid (n = 131), or urine (n = 173) specimens. Median bacterial load (TTP in days) was the strongest associate of MTB/RIF positivity in each fluid. TTP correlated with CT values in pulmonary specimens but not extrapulmonary specimens (Spearmans coefficient 0.5043 versus 0.1437; p = 0.030). Inhibition affected a greater proportion of pulmonary specimens than extrapulmonary specimens (IPC CT > 34: 6% (47/731) versus 1% (4/381; p < 0.0001). Pulmonary specimens had greater load than extrapulmonary specimens [TTPs (interquartile range) of 11 (7–16) versus 22 (18–33.5) days; p < 0.0001]. HIV-infection was associated with a decreased likelihood of MTB/RIF-positivity in pulmonary specimens but an increased likelihood in extrapulmonary specimens. Mycobacterial load, which displays significant variation across different body compartments, is the main determinant of MTB/RIF-positivity rather than PCR inhibition. MTB/RIF CT is a poor surrogate of load in extrapulmonary specimens.

Identification of SQ609 as a lead compound from a library of dipiperidines

We recently reported that compounds created around a dipiperidine scaffold demonstrated activity against Mycobacterium tuberculosis (Mtb) (Bogatcheva, E.; Hanrahan, C.; Chen, P.; Gearhart, J.; Sacksteder, K.; Einck, L.; Nacy, C.; Protopopova, M. Bioorg. Med. Chem. Lett.2010, 20, 201). To optimize the dipiperidine compound series and to select a lead compound to advance into preclinical studies, we evaluated the structure-activity relationship (SAR) of our proprietary libraries. The (piperidin-4-ylmethyl)piperidine scaffold was an essential structural element required for antibacterial activity. Based on SAR, we synthesized a focused library of 313 new dipiperidines to delineate additional structural features responsible for antitubercular activity. Thirty new active compounds with MIC 10-20 μg/ml on Mtb were identified, but none was better than the original hits of this series, SQ609, SQ614, and SQ615. In Mtb-infected macrophages in vitro, SQ609 and SQ614 inhibited more than 90% of intracellular bacterial growth at 4 μg/ml; SQ615 was toxic to these cells. In mice infected with Mtb, weight loss was completely prevented by SQ609, but not SQ614, and SQ609 had a prolonged therapeutic effect, extended by 10-15 days, after cessation of therapy. Based on in vitro and in vivo antitubercular activity, SQ609 was identified as the best-in-class dipiperidine compound in the series.

Xpert MTB/RIF Assay Shortens Airborne Isolation for Hospitalized Patients With Presumptive Tuberculosis in the United States

BACKGROUND In the United States, individuals with presumptive pulmonary tuberculosis are placed in airborne infection isolation (AII) and assessed by smear microscopy on 3 respiratory specimens collected 8-24 hours apart. Xpert MTB/RIF assay (Xpert) on 1, 2, or 3 specimens may be more efficient for determining AII discontinuation. METHODS This single-center, observational cohort study of inpatients with presumptive pulmonary tuberculosis enrolled adults with 1 or more sputum specimens submitted for smear microscopy. Smear microscopy and Xpert were performed on each sputum specimen. Clinicians were blinded to Xpert results. The primary endpoint was AII duration. Secondary endpoints were laboratory processing time, strategy-based tuberculosis detection, and sensitivity and specificity. RESULTS Among 207 subjects, the median AII duration was 68.0 hours (interquartile range [IQR], 47.1-97.5) for smear microscopy compared with 20.8 hours (IQR, 16.8-32.0) for the 1-specimen Xpert, 41.2 hours (IQR, 26.6-54.8) for the 2-specimen Xpert, and 54.0 hours (IQR, 43.3-80.0) for the 3-specimen Xpert strategies (P ≤ .004). Median laboratory processing time for smear microscopy was 2.5 times as long as Xpert (P < .001). The 2- and 3-specimen Xpert and smear microscopy strategies captured all 6 tuberculosis cases. The 1-specimen Xpert strategy missed 1 case. No difference was observed between smear microscopy and Xpert in sensitivity or specificity for detection of Mycobacterium tuberculosis. CONCLUSIONS Xpert-based strategies significantly reduced AII duration compared with the smear-based strategy. The 2-specimen Xpert strategy was most efficient in minimizing AII time while identifying all tuberculosis cases among individuals with presumptive tuberculosis in this low-burden setting.

The high-risk donor: Viral infections in solid organ transplantation

PURPOSE OF REVIEW Recently, four organ recipients were infected with HIV through transplantation, raising questions about current serologic testing policies. Currently, the decision to use enzyme-linked immunosorbent assay or nucleic acid testing, an expensive and time-consuming method capable of detecting more recent infections, is left up to individual organ procurement organizations. The purpose of this review was to present estimates of the window period between infection and detection by enzyme-linked immunosorbent assay and nucleic acid testing for HIV, hepatitis B virus, and hepatitis C virus; and to evaluate the impact of those infections on posttransplant outcomes. RECENT FINDINGS Nucleic acid testing for HIV can detect infections 12-13 days earlier than enzyme-linked immunosorbent assay; in the case of hepatitis B virus, infections are detected 21.8-36 days earlier; and in the case of hepatitis C virus, infections are detected 26-60 days earlier. Studies indicate that it is possible to manage all three infections posttransplant. HIV/hepatitis C virus coinfections seem to present the greatest posttransplant management challenges due to drug toxicities. SUMMARY Nucleic acid testing can reduce the window period and thus increase the probability of detecting viral infections. HIV, hepatitis B virus, and hepatitis C virus positive organs may be appropriate for use in some situations; nucleic acid testing helps patients and physicians make informed decisions about their use.

Point-of-care Xpert® MTB/RIF for smear-negative tuberculosis suspects at a primary care clinic in South Africa

OBJECTIVE To assess the clinical utility and cost of point-of-care Xpert® MTB/RIF for the diagnosis of smear-negative tuberculosis (TB). DESIGN Cohort study of smear-negative TB suspects at a South African primary care clinic. Participants provided one sputum sample for fluorescent smear microscopy and culture and an additional sample for Xpert. Outcomes of interest were TB diagnosis, linkage to care, patient and provider costs. RESULTS Among 199 smear-negative TB suspects, 16 were positive by Xpert, 15 by culture and 7 by microscopy. All cases identified by Xpert began anti-tuberculosis treatment the same or next day; only one of five Xpert-negative culture-positive cases started treatment after 34 days. Xpert at point of care offered similar diagnostic yield but a faster turnaround time than smear and culture performed at a centralized laboratory. Compared to smear plus culture, Xpert (at US