Sheldon Campbell

Biomarker-assisted dose selection for safety and efficacy in early development of PNU-100480 for tuberculosis.

ABSTRACT Tuberculosis is a serious global health threat for which new treatments are urgently needed. This study examined the safety, tolerability, pharmacokinetics, and pharmacodynamics of multiple ascending doses of the oxazolidinone PNU-100480 in healthy volunteers, using biomarkers for safety and efficacy. Subjects were randomly assigned to PNU-100480 or placebo (4:1) at schedules of 100, 300, or 600 mg twice daily or 1,200 mg daily for 14 days or a schedule of 600 mg twice daily for 28 days to which pyrazinamide was added on days 27 and 28. A sixth cohort was given linezolid at 300 mg daily for 4 days. Signs, symptoms, and routine safety tests were monitored. Bactericidal activity against Mycobacterium tuberculosis was measured in ex vivo whole-blood culture. Plasma drug and metabolite concentrations were compared to the levels required for inhibition of M. tuberculosis growth and 50% inhibition of mitochondrial protein synthesis. All doses were safe and well tolerated. There were no hematologic or other safety signals during 28 days of dosing at 600 mg twice daily. Plasma concentrations of PNU-100480 and metabolites at this dose remained below those required for 50% inhibition of mitochondrial protein synthesis. Cumulative whole-blood bactericidal activity of PNU-100480 at this dose (−0.316 ± 0.04 log) was superior to the activities of all other doses tested (P < 0.001) and was significantly augmented by pyrazinamide (−0.420 ± 0.06 log) (P = 0.002). In conclusion, PNU-100480 was safe and well tolerated at all tested doses. Further studies in patients with tuberculosis are warranted. Biomarkers can accelerate early development of new tuberculosis treatments.

Pharmacokinetics and Whole-Blood Bactericidal Activity against Mycobacterium tuberculosis of Single Doses of PNU-100480 in Healthy Volunteers

BACKGROUND The oxazolidinone PNU-100480 is superior to linezolid against experimental murine tuberculosis. Two metabolites contribute to but do not fully account for its superiority. This study examined the safety, tolerability, pharmacokinetics, and mycobactericidal activity of single ascending doses of PNU-100480. METHODS Nineteen healthy volunteers received 2 escalating single oral doses (35-1500 mg) of PNU-100480 or placebo. Eight subjects received 4 daily doses of 300 mg of linezolid. Drug concentrations and bactericidal activity against Mycobacterium tuberculosis in whole-blood bactericidal culture were measured. RESULTS All doses were safe and well tolerated. PNU-100480 doses to 1000 mg were well absorbed and showed approximately proportional increases in exposures of parent and metabolites. The geometric mean maximal concentrations of PNU-100480, PNU-101603, and PNU-101244 (sulfoxide and sulfone metabolites) at 1000 mg were 839, 3558, and 54 ng/mL, respectively. The maximal whole-blood bactericidal activity (-0.37 +/- .06 log/day) occurred at combined PNU levels > or =2 times the minimum inhibitory concentration. The observed geometric mean maximal concentration for linezolid was 6425 ng/mL. Its maximal whole-blood bactericidal activity also occurred at > or =2 times the minimum inhibitory concentration, but it was only -0.16 +/- .05 log/day (P< .001) Neither drug showed enhanced activity at higher concentrations. CONCLUSIONS Single doses of PNU-100480 to 1000 mg were well tolerated and exhibited antimycobacterial activity superior to 300 mg of linezolid at steady state. Additional studies are warranted to define its role in drug-resistant tuberculosis.

Rapid Evaluation in Whole Blood Culture of Regimens for XDR-TB Containing PNU-100480 (Sutezolid), TMC207, PA-824, SQ109, and Pyrazinamide

There presently is no rapid method to assess the bactericidal activity of new regimens for tuberculosis. This study examined PNU-100480, TMC207, PA-824, SQ109, and pyrazinamide, singly and in various combinations, against intracellular M. tuberculosis, using whole blood culture (WBA). The addition of 1,25-dihydroxy vitamin D facilitated detection of the activity of TMC207 in the 3-day cultures. Pyrazinamide failed to show significant activity against a PZA-resistant strain (M. bovis BCG), and was not further considered. Low, mid, and high therapeutic concentrations of each remaining drug were tested individually and in a paired checkerboard fashion. Observed bactericidal activity was compared to that predicted by the sum of the effects of individual drugs. Combinations of PNU-100480, TMC207, and SQ109 were fully additive, whereas those including PA-824 were less than additive or antagonistic. The cumulative activities of 2, 3, and 4 drug combinations were predicted based on the observed concentration-activity relationship, published pharmacokinetic data, and, for PNU-100480, published WBA data after oral dosing. The most active regimens, including PNU-100480, TMC207, and SQ109, were predicted to have cumulative activity comparable to standard TB therapy. Further testing of regimens including these compounds is warranted. Measurement of whole blood bactericidal activity can accelerate the development of novel TB regimens.

Educating medical students in laboratory medicine: a proposed curriculum.

As the 100th anniversary of the Flexner report nears, medical student education is being reviewed at many levels. One area of concern, expressed in recent reports from some national health care organizations, is the adequacy of training in the discipline of laboratory medicine (also termed clinical pathology). The Academy of Clinical Laboratory Physicians and Scientists appointed an ad hoc committee to review this topic and to develop a suggested curriculum, which was subsequently forwarded to the entire membership for review. The proposed medical student laboratory medicine curriculum defines goals and objectives for training, provides guidelines for instructional methods, and gives examples of how outcomes can be assessed. This curriculum is presented as a potentially helpful outline for use by medical school faculty and curriculum committees.

Home Testing To Detect Human Immunodeficiency Virus: Boon or Bane?

With the waiver of the Orasure Oraquick rapid human immunodeficiency virus (HIV) test in January 2003, testing for HIV infection in the United States moved from the laboratory to the clinic, the emergency room, and other outpatient settings. By now, millions of rapid HIV tests have been performed, largely by nonlaboratorians and largely outside of dedicated laboratory space. This experience has significantly transformed HIV testing nationally. The next logical step in broadening the settings in which HIV testing can be performed, approval of an HIV test for sale “over the counter” (OTC), involves clinical, technical, psychological, and public health issues along with a fair sprinkling of politics. Much of the rationale for both rapid, “waived” and home-use HIV testing can be summarized by two simple statistics: (i) approximately 30% of HIV-infected persons in the United States are unaware of their serostatus, and (ii) in 2004, 39% of persons with AIDS (e.g., opportunistic infection or CD4+-T-cell count of <200) first tested positive for HIV within 1 year of their AIDS diagnosis (7). Current evaluative approaches are missing substantial numbers of infected persons and detect HIV infection at a later stage than is optimal. Expanding access to HIV testing is a logical approach to addressing these inadequacies. Newly proposed methods for HIV testing must be compared not with an ideal system but with the current state of HIV surveillance and testing. In the United States, kits for home diagnostic testing are available for a limited set of analytes (9). There are currently no OTC tests for infectious diseases; tests for group A streptococcal pharyngitis and for influenza were rejected for home use due to insufficient sensitivity. There are, however, home collection kits for hetatitis C virus and HIV infection that allow consumers to collect specimens and send them to laboratories for testing and direct reporting. The scientific literature on home testing has recently been reviewed and can best be described as “sparse” (12). There have been few studies of the accuracy of home testing methods beyond those performed for Food and Drug Administration (FDA) approval. Even for well-established practices such as home glucose monitoring, there are limited data with respect to outcomes: the recommendations of the American Diabetes Association and the World Health Organization are based primarily on cohort studies and expert opinion and not on controlled studies showing a clinically significant impact on outcomes. The randomized clinical trials that have been performed demonstrated mixed results; a few showed improvement in outcome measures such as hemoglobin A1c levels, but more trials showed no significant effects. Although tests are widely available, an estimation of the clinical or public health impact of any home testing method is nearly pure guesswork at this time.

SQ109 and PNU-100480 interact to kill Mycobacterium tuberculosis in vitro

OBJECTIVES To investigate in vitro interaction between two compounds, SQ109 and PNU-100480, currently in development for the treatment of Mycobacterium tuberculosis (MTB). METHODS The two-drug interactions between SQ109 and PNU-100480 and its major metabolite PNU-101603 were assessed by chequerboard titration, and the rate of killing and intracellular activity were determined in both J774A.1 mouse macrophages and whole blood culture. RESULTS In chequerboard titration, interactions between SQ109 and either oxazolidinone were additive. In time-kill studies, SQ109 killed MTB faster than PNU compounds, and its rate of killing was further enhanced by both oxazolidinones. The order of efficacy of single compounds against intracellular MTB was SQ109 > PNU-100480 > PNU-101603. At sub-MIC, combinations of SQ109 + PNU compounds showed improved intracellular activity over individual drugs; at ≥MIC, the order of efficacy was SQ109 > SQ109 + PNU-100480 > SQ109 + PNU-101603. In whole blood culture, the combined bactericidal activities of SQ109 and PNU-100480 and its major metabolite against intracellular M. tuberculosis did not differ significantly from the sum of the compounds tested individually. CONCLUSIONS SQ109 and PNU combinations were additive and improved the rate of MTB killing over individual drugs. These data suggest that the drugs may work together cooperatively to eliminate MTB in vivo.

Measurement of serum D-arabinitol/creatinine ratios for initial diagnosis and for predicting outcome in an unselected, population-based sample of patients with Candida fungemia.

ABSTRACT d-Arabinitol (DA) is a useful diagnostic marker for candidiasis in patients with neutropenia and other high-risk groups, but its use in unselected patients with a broad range of underlying diseases and conditions has not been studied. We used an automated enzymatic fluorometric assay to measure serum DA/creatinine ratios (DA/crs) in 30 healthy adults, 100 hospitalized controls without Candida fungemia, and 83 patients from a study of all Candida fungemias in Connecticut between October 1998 and September 1999. Sixty-three of 83 (76%) fungemic patients and 11 of 100 (11%) nonfungemic controls had serum DA/crs ≥3.9 μM/mg/dl (mean + 3 standard deviations for 30 healthy adults). High serum DA/crs were less frequent in patients with cancer or fungemia caused by the DA nonproducer Candida glabrata than in patients with cancer or fungemia caused by a DA producer, C. albicans, C. tropicalis, or C. parapsilosis. The serum DA/cr was first ≥3.9 μM/mg/dl before, on the same day as, or after the first positive blood culture was drawn for 30 (36%), 22 (27%), and 11 (13%) fungemia patients, respectively. Mortality did not differ significantly among the patients with high or normal initial or peak serum DA/crs, but mortality was higher if any serum DA/cr value was ≥3.9 μM/mg/dl 3 or more days after the onset of fungemia (18/27 versus 4/24 patients, respectively; P < 0.001). We conclude that serum DA/crs are useful both for the initial diagnosis of Candida fungemia and for prognostic purposes for unselected patients with a broad range of underlying diseases and conditions.

Clinical Utility of On-Demand Multiplex Respiratory Pathogen Testing among Adult Outpatients.

ABSTRACT Multiplex tests for respiratory tract infections include up to 20 targets for common pathogens, predominantly viruses. A specific therapeutic intervention is available for individuals testing positive for influenza viruses (oseltamivir), and it is potentially beneficial to identify non-influenza viruses to avoid unnecessary antibiotic use. We evaluated antimicrobial prescriptions following respiratory pathogen testing among outpatients at a large Veterans Administration (VA) medical center. Results of the FilmArray respiratory panel (BioFire, Salt Lake City, UT) from 15 December 2014 to 15 April 2015 were evaluated among 408 outpatients, and patient medical records were reviewed. Differences in antibiotic and oseltamivir prescription rates were analyzed. Among 408 patients tested in outpatient centers (emergency departments, urgent care clinics, and outpatient clinics), 295 (72.3%) were managed as outpatients. Among these 295 outpatients, 105 (35.6%) tested positive for influenza virus, 109 (36.9%) tested positive for a non-influenza virus pathogen, and 81 (27.5%) had no respiratory pathogen detected. Rates of oseltamivir and antibiotic prescriptions were significantly different among the three test groups (chi-squared values of 167.6 [P < 0.0001] and 10.48 [P = 0.005], respectively), but there was no significant difference in antibiotic prescription rates between the non-influenza virus pathogen group and those who tested negative (chi-square value, 0; P = 1.0). Among adult outpatients, testing positive for influenza virus was associated with receiving fewer antibiotic prescriptions, but no such effect was seen for those who tested positive for a non-influenza virus. These data suggest that testing for influenza viruses alone may be sufficient and more cost-effective than multiplex pathogen testing for outpatients.

HIV Testing Near the Patient: Changing the Face of HIV Testing

Virological, epidemiologic, and operational barriers have slowed the progress toward effective management and eradication of HIV infection, despite significant advances in diagnosis since the early 1980s. Because early diagnosis profoundly affects the health care and survival of infected/high-risk individuals, and because the time required for conventional testing remains a barrier in many settings, rapid HIV testing has been developed for use both in the clinical laboratory and at the point of care. Recent studies have identified applications, advantages, and limitations of these assays, which may influence the development of new and more effective public health testing and screening protocols. In the United States, the Food and Drug Administration has approved the use of six rapid HIV tests. This review summarizes these modern rapid point-of-care HIV tests and their role in preventing the spread of HIV and in detecting, managing, and treating patients affected by the HIV pandemic.

The Clinical Microbiology Laboratory in the Diagnosis of Lower Respiratory Tract Infections

Lower respiratory tract infections (LRTIs) produce between 5 and 10% of all deaths reported to the CDC via the 122 Cities Mortality Reporting System ([5][1]). The clinical laboratory plays a vital role in the diagnosis of these infections but faces numerous challenges due to the complexity of LRTIs