T-cell receptor gene rearrangement and expression in human natural killer cells: natural killer activity is not dependent on the rearrangement and expression of T-cell receptor α , β , or γ genes

To test the hypothesis that the T-cell receptor ( Tcr ) λ gene encodes a natural killer (NK) cell receptor molecule, three human NK clones and fresh peripheral blood lymphocytes with NK activity from two patients with a CD16 + lymphocytosis were analyzed for rearrangements and expression of the human Tcr α, β , and λ genes. Two of the clones displayed distinct rearrangements of their Tcr β and λ genes and expressed mature Tcr α, β , and αl RNA. However, one of the clones and both patient samples displayed marked NK activity but failed to rearrange or express any of their Tcr genes. These findings demonstrate that human natural killer activity is not dependent on Tcr λ gene rearrangement and expression. In addition, they confirm previous findings concerning the lack of Tcr α and β gene expression in some natural killer cells. Thus, they suggest the existence of additional NK-specific recognition molecules.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46745/1/251_2004_Article_BF00376117.pd

Effect of Tipranavir-Ritonavir on Pharmacokinetics of Raltegravir▿

Raltegravir (RAL) is a novel and potent human immunodeficiency virus type 1 integrase inhibitor that is predominantly metabolized via glucuronidation. The protease inhibitor combination tipranavir (TPV) at 500 mg and ritonavir (RTV) at 200 mg (TPV-RTV) has inhibitory and inductive effects on metabolic enzymes, which includes the potential to induce glucuronosyltransferase. Because RAL may be coadministered with TPV-RTV, there is the potential for the induction of RAL metabolism. Consequently, we assessed the effect of TPV-RTV on the pharmacokinetics of RAL and the safety and tolerability of this combination. Eighteen healthy adults were enrolled in this open-label study. The participants received RAL at 400 mg twice daily for 4 days (period 1) and TPV-RTV twice daily for 7 days (period 2), followed immediately by 400 mg RAL with TPV-RTV twice daily for 4 days (period 3). Under steady-state conditions, the RAL concentration at 12 h (C12) was decreased when RAL was administered with TPV-RTV (geometric mean ratio [GMR], 0.45; 90% confidence interval [CI] 0.31, 0.66; P = 0.0021); however, the area under the concentration-time curve from time zero to 12 h (GMR, 0.76; 90% CI, 0.49, 1.19; P = 0.2997) and the maximum concentration in serum (GMR, 0.82; 90% CI, 0.46, 1.46; P = 0.5506) were not substantially affected. There were no serious adverse experiences or discontinuations due to study drug-related adverse experiences, and RAL coadministered with TPV-RTV was generally well tolerated. Although the RAL C12 was decreased with TPV-RTV in this study, favorable efficacy data collected in phase III studies substantiate that TPV-RTV may be coadministered with RAL without dose adjustment

Refinement of Stopping Rules During Treatment of Hepatitis C Genotype 1 Infection With Boceprevir and Peginterferon/Ribavirin

In comparison with peginterferon/ribavirin alone, boceprevir with peginterferon/ribavirin significantly improves sustained virological response (SVR) rates in patients with chronic hepatitis C virus (HCV) genotype 1 infections, but treatment failure remains a significant problem. Using phase 3 trial databases, we sought to develop stopping rules for patients destined to fail boceprevir-based combination therapy in order to minimize drug toxicity, resistance, and costs in the face of ultimate futility. Exploratory post hoc analyses using data from the Serine Protease Inhibitor Therapy 2 (SPRINT-2) study (treatment-naive patients) and the Retreatment With HCV Serine Protease Inhibitor Boceprevir and Pegintron/Rebetol 2 (RESPOND-2) study (treatment-experienced patients) were undertaken to determine whether protocol-specified stopping rules (detectable HCV RNA at week 24 for SPRINT-2 and at week 12 for RESPOND-2) could be refined and harmonized. In SPRINT-2, a week 12 rule with an HCV RNA cutoff of 100 IU/mL would have discontinued therapy in 65 of 195 failures (sensitivity 5 33%) without sacrificing a single SVR among 475 successes (specificity 5 100%). Viral variants emerged after week 12 in 36 of the 49 evaluable patients (73%) who would have discontinued at week 12 using a 100 IU/mL stopping rule. In RESPOND-2, five of six patients with week 12 HCV RNA levels between the lower limit of detection (9.3 IU/mL) and the lower limit of quantification (25 IU/mL) who continued therapy despite the protocol-stipulated futility rule achieved SVR; one additional patient with a week 12 HCV RNA level of 148 IU/mL also continued therapy, had undetectable HCV RNA at week 16, and attained SVR. Conclusion: Although a stopping rule of detectable HCV RNA at week 12 would have forfeited some SVR cases, week 12 HCV RNA levels 100 IU/mL almost universally predicted a failure to achieve SVR in both treatment-naive and treatment-experienced patients. In boceprevir recipients, the combination of 2 stopping rules-an HCV RNA level 100 IU/mL at week 12 and detectable HCV RNA at week 24-maximized the early discontinuation of futile therapy and minimized premature treatment discontinuation. (HEPATOLOGY 2012;56:567-575) C ombination therapy with peginterferon alfa/ ribavirin (P/R) has been the standard approach to the management of chronic hepatitis C virus (HCV) infections for the last decade. Sustained virological response (SVR) rates of 54% to 56% were achieved in the pivotal trials of Abbreviations: HCV, hepatitis C virus; LLD, lower limit of detection; LLQ, lower limit of quantification; P/R, pegintron alfa/ribavirin; RESPOND-2, Retreatment With HCV Serine Protease Inhibitor Boceprevir and Pegintron/Rebetol 2; SPRINT-2, Serine Protease Inhibitor Therapy 2; SVR, sustained virological response. From th

Lack of a Significant Drug Interaction between Raltegravir and Tenofovir▿

Raltegravir is a novel human immunodeficiency virus type 1 (HIV-1) integrase inhibitor with potent in vitro activity (95% inhibitory concentration of 31 nM in 50% human serum). This article reports the results of an open-label, sequential, three-period study of healthy subjects. Period 1 involved raltegravir at 400 mg twice daily for 4 days, period 2 involved tenofovir disoproxil fumarate (TDF) at 300 mg once daily for 7 days, and period 3 involved raltegravir at 400 mg twice daily plus TDF at 300 mg once daily for 4 days. Pharmacokinetic profiles were also determined in HIV-1-infected patients dosed with raltegravir monotherapy versus raltegravir in combination with TDF and lamivudine. There was no clinically significant effect of TDF on raltegravir. The raltegravir area under the concentration time curve from 0 to 12 h (AUC0-12) and peak plasma drug concentration (Cmax) were modestly increased in healthy subjects (geometric mean ratios [GMRs], 1.49 and 1.64, respectively). There was no substantial effect of TDF on raltegravir concentration at 12 h postdose (C12) in healthy subjects (GMR [TDF plus raltegravir-raltegravir alone], 1.03; 90% confidence interval [CI], 0.73 to 1.45), while a modest increase (GMR, 1.42; 90% CI, 0.89 to 2.28) was seen in HIV-1-infected patients. Raltegravir had no substantial effect on tenofovir pharmacokinetics: C24, AUC, and Cmax GMRs were 0.87, 0.90, and 0.77, respectively. Coadministration of raltegravir and TDF does not change the pharmacokinetics of either drug to a clinically meaningful degree. Raltegravir and TDF may be coadministered without dose adjustments

Effect of Rifampin, a Potent Inducer of Drug-Metabolizing Enzymes, on the Pharmacokinetics of Raltegravir▿

Raltegravir is a human immunodeficiency virus type 1 integrase strand transfer inhibitor that is metabolized by glucuronidation via UGT1A1 and may be affected by inducers of UGT1A1, such as rifampin (rifampicin). Two pharmacokinetic studies were performed in healthy subjects: study 1 examined the effect of administration of 600-mg rifampin once daily on the pharmacokinetics of a single dose of 400-mg raltegravir, and study 2 examined the effect of 600-mg rifampin once daily on the pharmacokinetics of 800-mg raltegravir twice daily compared to 400-mg raltegravir twice daily without rifampin. Raltegravir coadministered with rifampin resulted in lower plasma raltegravir concentrations: in study 1, the geometric mean ratios (GMRs) and 90% confidence intervals (90% CIs) for the plasma raltegravir concentration determined 12 h postdose (C12), area under the concentration-time curve from 0 h to ∞ (AUC0-∞), and maximum concentration of drug in plasma (Cmax) (400-mg raltegravir plus rifampin/400-mg raltegravir) were 0.39 (0.30, 0.51), 0.60 (0.39, 0.91), and 0.62 (0.37, 1.04), respectively. In study 2, the GMRs and 90% CIs for raltegravir C12, AUC0-12, and Cmax (800-mg raltegravir plus rifampin/400-mg raltegravir) were 0.47 (0.36, 0.61), 1.27 (0.94, 1.71), and 1.62 (1.12, 2.33), respectively. Doubling the raltegravir dose to 800 mg when coadministered with rifampin therefore compensates for the effect of rifampin on raltegravir exposure (AUC0-12) but does not overcome the effect of rifampin on raltegravir trough concentrations (C12). Coadministration of rifampin and raltegravir is not contraindicated; however, caution should be used, since raltegravir trough concentrations in the presence of rifampin are likely to be at the lower limit of clinical experience