Brincidofovir Is Not a Substrate for the Human Organic Anion Transporter 1: A Mechanistic Explanation for the Lack of Nephrotoxicity Observed in Clinical Studies.

BACKGROUND: Brincidofovir (BCV) is an orally bioavailable lipid conjugate of cidofovir (CDV) with increased in vitro potency relative to CDV against all 5 families of double-stranded DNA viruses that cause human disease. After intravenous (IV) administration of CDV, the organic anion transporter 1 (OAT1) transports CDV from the blood into the renal proximal tubule epithelial cells with resulting dose-limiting nephrotoxicity. OBJECTIVE: To study whether OAT1 transports BCV and to evaluate the pharmacokinetic and renal safety profile of oral BCV compared with IV CDV. METHODS: The cellular uptake of BCV and its major metabolites was assessed in vitro. Renal function at baseline and during and after treatment in subjects in BCV clinical studies was examined. RESULTS: In OAT1-expressing cells, uptake of BCV and its 2 major metabolites (CMX103 and CMX064) was the same as in mock-transfected control cells and was not inhibited by the OAT inhibitor probenecid. In human pharmacokinetic studies, BCV administration at therapeutic doses resulted in detection of CDV as a circulating metabolite; peak CDV plasma concentrations after oral BCV administration in humans were <1% of those observed after IV CDV administration at therapeutic doses. Analysis of renal function and adverse events from 3 BCV clinical studies in immunocompromised adult and pediatric subjects indicated little to no evidence of associated nephrotoxicity. Over 80% of subjects who switched from CDV or foscarnet to BCV experienced an improvement in renal function as measured by maximum on-treatment estimated glomerular filtration rate. CONCLUSIONS: The lack of BCV uptake through OAT1, together with lower CDV concentrations after oral BCV compared with IV CDV administration, likely explains the superior renal safety profile observed in immunocompromised subjects receiving BCV compared with CDV.

Analysis of Mutations in the Gene Encoding Cytomegalovirus DNA Polymerase in a Phase 2 Clinical Trial of Brincidofovir Prophylaxis.

Brincidofovir is an oral antiviral in development for prevention of cytomegalovirus disease. Cytomegalovirus genotyping results from a phase 2 trial comparing brincidofovir to placebo for prophylaxis against cytomegalovirus infection in hematopoietic cell transplant recipients provided initial data on the clinical resistance profile for brincidofovir. In this study, no known resistance-associated mutations were detected in brincidofovir-treated subjects; identified genotypic substitutions did not confer resistance to cytomegalovirus antivirals in vitro, suggesting that these changes represent polymorphisms unrelated to brincidofovir resistance. Lack of evidence for genotypic resistance during prophylaxis suggests that first-line use of brincidofovir for prevention of cytomegalovirus infection may preserve downstream options for patients.

Brincidofovir for polyomavirus-associated nephropathy after allogeneic hematopoietic stem cell transplantation.

Polyomavirus-associated nephropathy (PVAN) is common in patients who have undergone kidney transplantation and has been reported in hematopoietic stem cell (HSC) transplant recipients. Aside from reduction of immunosuppression, few therapeutic options exist for treatment of PVAN. We report a case of PVAN in a severely immunocompromised allogeneic HSC transplant recipient that was treated with brincidofovir without reduction of immunosuppression. We review our institutional experience of PVAN in HSC transplantation and discuss the potential use of brincidofovir for treatment.

CMX001 to prevent cytomegalovirus disease in hematopoietic-cell transplantation.

BACKGROUND: The use of available antiviral agents for the prevention of cytomegalovirus (CMV) disease is limited by frequent toxic effects and the emergence of resistance. CMX001 has potent in vitro activity against CMV and other double-stranded DNA viruses. We evaluated the safety and anti-CMV activity of CMX001 in patients who had undergone allogeneic hematopoietic-cell transplantation. METHODS: From December 2009 through June 2011, a total of 230 patients with data that could be evaluated were enrolled in the study. We randomly assigned these adult CMV-seropositive transplant recipients from 27 centers to oral administration of CMX001 or placebo. Patients were assigned in a 3:1 ratio to five sequential study cohorts according to a dose-escalating, double-blind design. Randomization was stratified according to the presence or absence of acute graft-versus-host disease and CMV DNA in plasma. Patients received the study drug after engraftment for 9 to 11 weeks, until week 13 after transplantation. Polymerase-chain-reaction analysis of CMV DNA in plasma was performed weekly. Patients in whom CMV DNA was detected at a level that required treatment discontinued the study drug and received preemptive treatment against CMV infection. The primary end point was a CMV event, defined as CMV disease or a plasma CMV DNA level greater than 200 copies per milliliter when the study drug was discontinued. The analysis was conducted in the intention-to-treat population. RESULTS: The incidence of CMV events was significantly lower among patients who received CMX001 at a dose of 100 mg twice weekly than among patients who received placebo (10% vs. 37%; risk difference, -27 percentage points; 95% confidence interval, -42 to -12; P=0.002). Diarrhea was the most common adverse event in patients receiving CMX001 at doses of 200 mg weekly or higher and was dose-limiting at 200 mg twice weekly. Myelosuppression and nephrotoxicity were not observed. CONCLUSIONS: Treatment with oral CMX001 at a dose of 100 mg twice weekly significantly reduced the incidence of CMV events in recipients of hematopoietic-cell transplants. Diarrhea was dose-limiting in this population at a dose of 200 mg twice weekly. (Funded by Chimerix; CMX001-201 ClinicalTrials.gov number, NCT00942305.).

Safety and efficacy of CMX001 as salvage therapy for severe adenovirus infections in immunocompromised patients.

No therapeutic agent has yet been established as the definitive therapy for adenovirus infections. We describe the clinical experience of 13 immunocompromised patients who received CMX001 (hexadecyloxypropyl cidofovir), an orally bioavailable lipid conjugate of cidofovir, for adenovirus disease. We retrospectively analyzed 13 patients with adenovirus disease and viremia treated with CMX001; data were available for ≥ 4 weeks after initiation of CMX001 therapy. Virologic response (VR) was defined as a 99% drop from baseline or undetectable adenovirus DNA in serum. The median age of the group was 6 years (range, 0.92-66 years). One patient had severe combined immunodeficiency, 1 patient was a small bowel transplant recipient, and 11 were allogeneic stem cell transplant recipients. Adenovirus disease was diagnosed at a median of 75 days (range, 15-720 days) after transplantation. All patients received i.v. cidofovir for a median of 21 days (range, 5-90 days) before CMX001 therapy. The median absolute lymphocyte count at CMX001 initiation was 300 cells/µL (range, 7-1500 cells/µL). Eight patients (61.5%) had a ≥ 1 log10 drop in viral load after the first week of therapy. By week 8, 9 patients (69.2%) demonstrated a VR, with a median time to achieve VR of 7 days (range, 3-35 days). The change in absolute lymphocyte count was inversely correlated with the change in log10 viral load only at week 6 (r = -0.74; P = .03). Patients with VR had longer survival than those without VR (median 196 days versus 54.5 days; P = .04). No serious adverse events were attributed to CMX001 during therapy. CMX001 may be a promising therapeutic option for the treatment of severe adenovirus disease in immunocompromised patients.

Comparison of real-time PCR assays for monitoring serum hepatitis B virus DNA levels during antiviral therapy.

The performance characteristics of the RealART and Molecular Beacons assays were compared with those of the Digene Hybrid Capture II assay (ultrasensitive). The results of the RealART and Digene Hybrid assays were related (r = 0.94; P < 0.001) and diverged by 2 orders of magnitude. The RealART assay can be used to effectively monitor serum hepatitis B virus DNA levels.

Severe hepatotoxicity associated with nevirapine use in HIV-infected subjects.

Human immunodeficiency virus (HIV)-infected South African patients (n=468) received blinded lamivudine or emtricitabine, stavudine, and either nevirapine or efavirenz (based on screening viral load). Baseline characteristics were analyzed in univariate and multivariate regression, to identify risk factors for hepatotoxicity (grade 3 or greater increase in serum aminotransferase levels). The occurrence of early hepatotoxicity was 17% in the nevirapine group and 0% in the efavirenz group and was balanced between the lamivudine and emtricitabine arms. Two subjects died of hepatic failure. Independent risk factors were body-mass index (BMI) <18.5, female sex, serum albumin level <35 g/L, mean corpuscular volume >85 fL, plasma HIV-1 RNA load <20,000 copies/mL, aspartate aminotransferase level <75 IU/L, and lactate dehydrogenase level <164 IU/L. The use of nevirapine in female patients with a low BMI should be discouraged.

A phase II dose-escalating trial of clevudine in patients with chronic hepatitis B.

Current therapies available for the treatment of chronic hepatitis B are limited in their ability to result in a cure. Clevudine is a new pyrimidine analog with potent anti-hepatitis B virus (HBV) activity in vitro. A multicenter dose-escalation study evaluated clevudine at 10, 50, 100, and 200 mg once daily for 28 days. Eligible patients had HBV DNA levels of 3 x 10(6) copies/mL or more, had not undergone nucleoside treatment, and were without human immunodeficiency or hepatitis C virus coinfection. Thirty-two patients were enrolled (5, 10, 10, and 7 patients in the 10-, 50-, 100-, and 200-mg dose groups, respectively), 81% were male, 81% Asian, and 88% were hepatitis Be antigen (HBeAg) positive at baseline. Median pretreatment serum HBV DNA levels ranged from 7.3 to 8.8 log(10) copies/mL. After 28 days, the median HBV DNA log(10) change from baseline was -2.5, -2.7, -3.0, and -2.6 log(10). Six months after dosing, median changes from baseline were -1.2, -1.4, -2.7 and -1.7 log(10) in the 10-, 50-, 100-, and 200-mg cohorts, respectively. Six of 27 patients lost HBeAg, and 3 of 27 patients seroconverted to HBe antibody. Clevudine was well tolerated, with no dose-limiting toxicities. A transient increase in alanine aminotransferase of up to 7.8 times the upper limit of normal (increase ranged from 20 to 186 IU/L) was observed in six patients in the 100-mg cohort, without signs of liver failure. These increases were associated with improved viral suppression. The pharmacokinetic profile of clevudine was proportional to the dose. In conclusion, these results demonstrate the tolerability and potent activity of clevudine in HBV-infected patients and support further clinical study.

Prospective randomized trial of emtricitabine versus lamivudine short-term monotherapy in human immunodeficiency virus-infected patients.

We conducted a randomized, open-label, 10-day study that compared the antiretroviral activity of emtricitabine (FTC) 25, 100, and 200 mg once daily and lamivudine (3TC) 150 mg 2 times/day in 82 human immunodeficiency virus (HIV)-infected patients with virus loads >5000 and <100,000 copies/mL who were naive for 3TC and abacavir. All FTC doses demonstrated potent antiretroviral activity. Significantly greater virus suppression was seen at the 200 mg/day dose of FTC than with the lower FTC doses and/or 3TC (P=.02, P=.04, and P=.04, respectively). At the 200 mg/day dose, FTC produced a 1.7-log10 mean reduction in virus load. Trough FTC levels at the 200 mg/day dose exceeded the in vitro 90% inhibitory concentration dose for FTC by 5-fold. The long plasma half-life and the superior antiviral activity versus 3TC of the 200 mg/day FTC dose confirmed the results of other studies and led to the selection of this dose for subsequent therapeutic trials.

Herpes simplex virus type 2 as a cause of severe meningitis in immunocompromised adults.

We reviewed the clinical and demographic characteristics and outcomes for 13 immunocompromised patients with herpes simplex virus (HSV)-induced meningitis. Eleven patients were receiving chemotherapy for leukemia or lymphoma, and 10 had acquired immunodeficiency syndrome. Patients presented with acute febrile meningitis. The median white blood cell count at the onset of symptoms was 400 cells/mm3. Examination of cerebrospinal fluid (CSF) specimens showed lymphocytic meningitis, but activated lymphocytes and low glucose levels were both noted in 7 patients. HSV DNA was detected in all CSF specimens, and HSV type 2 was identified in 7. Eight patients had suspected HSV-associated mucocutaneous lesions at the time of meningitis onset. Six patients had initial radiculalgia, with sphincter involvement in 2. Eleven patients received intravenous antiviral therapy, but treatment was delayed for 6 patients. Two of the 6 patients for whom treatment was delayed developed encephalitis and died, whereas 2 others experienced persistent neurological symptoms. HSV-2 can cause severe meningitis in immunocompromised patients. Early recognition and treatment might improve the outcome of such infections.

Serum HBV DNA as a marker of efficacy during therapy for chronic HBV infection: analysis and review of the literature.

Currently, compounds under evaluation for treatment of chronic hepatitis B virus (HBV) infection are evaluated with liver histology as the primary end point for efficacy. However, because of practical limitations in serial liver biopsies, there is a need for alternate markers to assess efficacy over shorter periods of time. Considering the direct correlation between viral replication and disease progression during human immunodeficiency virus and hepatitis C virus infection, we explored whether such a correlation exists for HBV infection. We reviewed the literature and conducted an analysis to investigate the relationship between absolute or treatment-induced changes in HBV DNA levels and other accepted markers of disease activity. A total of 26 prospective studies met our selection criteria, including 33 evaluable treatment arms. The study treatments consisted of nucleosides and/or interferon regimens and control arms. We found statistically significant and consistent correlations between viral load level or change and histologic grading and biochemical and serologic response. Our analysis suggests that a treatment-induced reduction in HBV DNA level can be used for assessing efficacy of treatment regimens. Further, we observed that quantitative HBV DNA has a broader dynamic range than histology, allowing demonstration of differences between 2 active treatments of unequal potency. The analysis showed stronger results in studies using nucleoside regimens and in hepatitis B e antigen (HBeAg)-positive patients. In conclusion, the goal of anti-HBV therapy should be profound and durable viral suppression, as defined by very sensitive assays. Additional prospective studies are needed to precisely determine the desirable level of viremia to attain.