Research Spotlight

Elwir, S., C. Anugwom, E. K. Connor, N. H. Giama, A. Ndzengue, J. Menk, E. A. Mohamed, L. R. Roberts and M. Hassan (2018). “Barriers in Hepatitis C Treatment in Somali Patients in the Direct Acting Antiviral Therapy Era.” J Natl Med Assoc 110(6): 556-559.

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BACKGROUND AND AIMS: Hepatitis C virus (HCV) treatment has changed dramatically in the last few years. Our observations suggest that a minority of HCV infected Somalis are treated. In this study, we aimed to evaluate for treatment and health outcome disparities between Somali and non-Somali patients during the direct acting antiviral (DAA) era. METHODS: Patients with HCV seen in the gastroenterology clinic in 2015 were included in the study. Patients were identified using ICD9 and 10 codes. Electronic medical records were analyzed to evaluate for treatment candidacy, acceptance and reasons for refusal of treatment. RESULTS: Genotype 4 followed by 3 were the most common genotypes in the Somalis while genotype 1 was the most common in the non-Somalis. Majority of patients were offered treatment, active alcohol and substance abuse was a common reason for not offering treatment in non-Somalis while the presence of hepatocellular carcinoma was the most common reason in Somalis. Somalis had higher rates of declining treatment given the asymptomatic nature of their disease and the feeling that treatment is not needed. Sustained virologic response rates were comparable in both groups. CONCLUSIONS: Disparities in acceptance of HCV treatment persist in the DAA era. The asymptomatic nature of the infection and potential cultural mistrust makes patients hesitant to undergo treatment. Healthcare providers must find interventions aimed at reducing barriers to treatment and increasing acceptance of HCV treatment.

Deshpande, D., S. Srivastava, E. Nuermberger, T. Koeuth, K. R. Martin, K. N. Cirrincione, P. S. Lee and T. Gumbo (2018). “Multiparameter Responses to Tedizolid Monotherapy and Moxifloxacin Combination Therapy Models of Children With Intracellular Tuberculosis.” Clin Infect Dis 67(suppl_3): S342-s348.

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Background: Children are often neglected during early development of antituberculosis agents, and most receive treatment after it is first tested in adults. However, very young children have tuberculosis that differs in many respects from adult cavitary pneumonia and could have different toxicity profiles to drugs. Linezolid is effective against intracellular tuberculosis, a common manifestation in young children. However, linezolid has considerable toxicity due to inhibition of mitochondrial enzymes. Tedizolid could be a replacement if it shows equal efficacy and reduced toxicity. Methods: We performed tedizolid dose-effect studies in the hollow fiber system model of intracellular tuberculosis. We measured linezolid concentrations, colony-forming units (CFU), time-to-positivity, and monocyte viability and performed RNA sequencing on infected cells collected from repetitive sampling of each system. We also compared efficacy of tedizolid vs linezolid and vs tedizolid-moxifloxacin combination. Results: There was no downregulation of mitochondrial enzyme genes, with a tedizolid 0-24 hour area under the concentration-time curve (AUC0-24) of up to 90 mg*h/L. Instead, high exposures led to increased mitochondrial gene expression and monocyte survival. The AUC0-24 to minimum inhibitory concentration ratio associated with 80% of maximal bacterial kill (EC80) was 184 by CFU/mL (r2 = 0.96) and 189 by time-to-positivity (r2 = 0.99). Tedizolid EC80 killed 4.0 log10 CFU/mL higher than linezolid EC80. The tedizolid-moxifloxacin combination had a bacterial burden elimination rate constant of 0.27 +/- 0.05 per day. Conclusions: Tedizolid demonstrated better efficacy than linezolid, without the mitochondrial toxicity gene or cytotoxicity signatures encountered with linezolid. Tedizolid-moxifloxacin combination had a high bacterial elimination rate.

Deshpande, D., J. G. Pasipanodya, S. Srivastava, P. Bendet, T. Koeuth, S. M. Bhavnani, P. G. Ambrose, W. Smythe, H. McIlleron, G. Thwaites, M. Gumusboga, A. Van Deun and T. Gumbo (2018). “Gatifloxacin Pharmacokinetics/Pharmacodynamics-based Optimal Dosing for Pulmonary and Meningeal Multidrug-resistant Tuberculosis.” Clin Infect Dis 67(suppl_3): S274-s283.

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Background: Gatifloxacin is used for the treatment of multidrug-resistant tuberculosis (MDR-TB). The optimal dose is unknown. Methods: We performed a 28-day gatifloxacin hollow-fiber system model of tuberculosis (HFS-TB) study in order to identify the target exposures associated with optimal kill rates and resistance suppression. Monte Carlo experiments (MCE) were used to identify the dose that would achieve the target exposure in 10000 adult patients with meningeal or pulmonary MDR-TB. The optimal doses identified were validated using probit analyses of clinical data from 2 prospective clinical trials of patients with pulmonary and meningeal tuberculosis. Classification and regression-tree (CART) analyses were used to identify the gatifloxacin minimum inhibitory concentration (MIC) below which patients failed or relapsed on combination therapy. Results: The target exposure associated with optimal microbial kill rates and resistance suppression in the HFS-TB was a 0-24 hour area under the concentration-time curve-to-MIC of 184. MCE identified an optimal gatifloxacin dose of 800 mg/day for pulmonary and 1200 mg/day for meningeal MDR-TB, and a clinical susceptibility breakpoint of MIC 2 mg/L, but 98% were cured if MIC was 90% probability of a cure in patients if treated with 800 mg/day for pulmonary tuberculosis and 1200 mg/day for meningeal tuberculosis. Doses

Deshpande, D., J. G. Pasipanodya, S. G. Mpagama, S. Srivastava, P. Bendet, T. Koeuth, P. S. Lee, S. K. Heysell and T. Gumbo (2018). “Ethionamide Pharmacokinetics-Pharmacodynamics-derived Dose, the Role of MICs in Clinical Outcome, and the Resistance Arrow of Time in Multidrug-resistant Tuberculosis.” Clin Infect Dis 67(suppl_3): S317-s326.

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Background: Ethionamide is used to treat multidrug-resistant tuberculosis (MDR-TB). The antimicrobial pharmacokinetics/pharmacodynamics, the contribution of ethionamide to the multidrug regimen, and events that lead to acquired drug resistance (ADR) are unclear. Methods: We performed a multidose hollow fiber system model of tuberculosis (HFS-TB) study to identify the 0-24 hour area under the concentration-time curve (AUC0-24) to minimum inhibitory concentration (MIC) ratios that achieved maximal kill and ADR suppression, defined as target exposures. Ethionamide-resistant isolates underwent whole-genome and targeted Sanger sequencing. We utilized Monte Carlo experiments (MCEs) to identify ethionamide doses that would achieve the target exposures in 10000 patients with pulmonary tuberculosis. We also identified predictors of time-to-sputum conversion in Tanzanian patients on ethionamide- and levofloxacin-based regimens using multivariate adaptive regression splines (MARS). Results: An AUC0-24/MIC >56.2 was identified as the target exposure in the HFS-TB. Early efflux pump induction to ethionamide monotherapy led to simultaneous ethambutol and isoniazid ADR, which abrogated microbial kill of an isoniazid-ethambutol-ethionamide regimen. Genome sequencing of isolates that arose during ethionamide monotherapy revealed mutations in both ethA and embA. In MCEs, 20 mg/kg/day achieved the AUC0-24/MIC >56.2 in >95% of patients, provided the Sensititre assay MIC was <2.5 mg/L. In the clinic, MARS revealed that ethionamide Sensititre MIC had linear negative relationships with time-to-sputum conversion until an MIC of 2.5 mg/L, above which patients with MDR-TB failed combination therapy. Conclusions: Ethionamide is an important contributor to MDR-TB treatment regimens, at Sensititre MIC <2.5 mg/L. Suboptimal ethionamide exposures led to efflux pump-mediated ADR.

Deshpande, D., J. G. Pasipanodya, S. G. Mpagama, P. Bendet, S. Srivastava, T. Koeuth, P. S. Lee, S. M. Bhavnani, P. G. Ambrose, G. Thwaites, S. K. Heysell and T. Gumbo (2018). “Levofloxacin Pharmacokinetics/Pharmacodynamics, Dosing, Susceptibility Breakpoints, and Artificial Intelligence in the Treatment of Multidrug-resistant Tuberculosis.” Clin Infect Dis 67(suppl_3): S293-s302.

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Background: Levofloxacin is used for the treatment of multidrug-resistant tuberculosis; however the optimal dose is unknown. Methods: We used the hollow fiber system model of tuberculosis (HFS-TB) to identify 0-24 hour area under the concentration-time curve (AUC0-24) to minimum inhibitory concentration (MIC) ratios associated with maximal microbial kill and suppression of acquired drug resistance (ADR) of Mycobacterium tuberculosis (Mtb). Levofloxacin-resistant isolates underwent whole-genome sequencing. Ten thousands patient Monte Carlo experiments (MCEs) were used to identify doses best able to achieve the HFS-TB-derived target exposures in cavitary tuberculosis and tuberculous meningitis. Next, we used an ensemble of artificial intelligence (AI) algorithms to identify the most important predictors of sputum conversion, ADR, and death in Tanzanian patients with pulmonary multidrug-resistant tuberculosis treated with a levofloxacin-containing regimen. We also performed probit regression to identify optimal levofloxacin doses in Vietnamese tuberculous meningitis patients. Results: In the HFS-TB, the AUC0-24/MIC associated with maximal Mtb kill was 146, while that associated with suppression of resistance was 360. The most common gyrA mutations in resistant Mtb were Asp94Gly, Asp94Asn, and Asp94Tyr. The minimum dose to achieve target exposures in MCEs was 1500 mg/day. AI algorithms identified an AUC0-24/MIC of 160 as predictive of microbiologic cure, followed by levofloxacin 2-hour peak concentration and body weight. Probit regression identified an optimal dose of 25 mg/kg as associated with >90% favorable response in adults with pulmonary tuberculosis. Conclusions: The levofloxacin dose of 25 mg/kg or 1500 mg/day was adequate for replacement of high-dose moxifloxacin in treatment of multidrug-resistant tuberculosis.