Tomas Cihlar

Gilead Sciences, فوستير سيتي، سان ماتيو، كاليفورنيا, California, United States

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Publications (103)387.63 Total impact

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    ABSTRACT: Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections in infants and young children. In addition, RSV causes significant morbidity and mortality in hospitalized elderly and immunocompromised patients. Currently, only palivizumab, a monoclonal antibody against the RSV fusion (F) protein, and inhaled ribavirin, are approved for the prophylactic and therapeutic treatment of RSV, respectively. Therefore, there is a clinical need for a safe and effective therapeutic agents for RSV infections. GS-5806, discovered via chemical optimization of a hit from a high-throughput antiviral screening campaign, selectively inhibits a diverse set of 75 RSV subtype A and B clinical isolates (mean EC 50 = 0.43 nM). The compound maintained potency in primary human airway epithelial cells and exhibited low cytotoxicity in human cell lines and primary cell cultures (selectivity > 23,000-fold). Time-of-addition and temperature shift studies demonstrated that GS-5806 does not block RSV attachment to cells, but interferes with virus entry. Follow-up experiments showed potent inhibition of RSV F-mediated cell-to-cell fusion. RSV A and B variants resistant to GS-5806, due to mutations in F protein (RSV A: L138F or F140L/N517I and RSV B: F488L or F488S), were isolated and showed cross-resistance to other RSV fusion inhibitors such as VP-14637, but remained fully sensitive to palivizumab and ribavirin. In summary, GS-5806 is a potent and selective RSV fusion inhibitor with antiviral activity against a diverse set of RSV clinical isolates. The compound is currently under clinical investigation for the treatment of RSV infection in pediatric, immunocompromised, and elderly patients.
    No preview · Article · Dec 2015 · Antimicrobial Agents and Chemotherapy
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    ABSTRACT: Importance: RSV circulates seasonally causing acute lower respiratory disease. Therapeutic interventions with efficacy throughout the viral replication cycle, rapid viral clearance and prevention of potentially harmful inflammatory responses are desirable. Compounds targeting the RSV polymerase inhibited virus replication late in the viral lifecycle, and, depending on the functional domain targeted, either attenuated or amplified RIG-I and downstream interferon pathways in infected cells. These data will help guide the development of safe and effective therapies by providing new molecular evidence that the mechanism of inhibition by an antiviral compound can directly impact innate antiviral immune responses in the airway epithelium.
    No preview · Article · Nov 2015 · Journal of Virology
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    ABSTRACT: HIV reservoirs and production of viral antigens are not eliminated in chronically infected participants treated with combination antiretroviral therapy (cART). Novel therapeutic strategies aiming at viral reservoir elimination are needed to address chronic immune dysfunction and non-AIDS morbidities that exist despite effective cART. The HIV envelope protein (Env) is emerging as a highly specific viral target for therapeutic elimination of the persistent HIV-infected reservoirs via antibody-mediated cell killing. Dual-Affinity Re-Targeting (DART) molecules exhibit a distinct mechanism of action via binding the cell surface target antigen and simultaneously engaging CD3 on cytotoxic T lymphocytes (CTLs). We designed and evaluated Env-specific DARTs (HIVxCD3 DARTs) derived from known antibodies recognizing diverse Env epitopes with or without broadly neutralizing activity. HIVxCD3 DARTs derived from PGT121, PGT145, A32, and 7B2, but not VRC01 or 10E8 antibodies, mediated potent CTL-dependent killing of quiescent primary CD4 T cells infected with diverse HIV isolates. Similar killing activity was also observed with DARTs structurally modified for in vivo half-life extension. In an ex vivo model using cells isolated from HIV-infected participants on cART, combinations of the most potent HIVxCD3 DARTs reduced HIV expression both in quiescent and activated peripheral blood mononuclear cell cultures isolated from HIV-infected participants on suppressive cART. Importantly, HIVxCD3 DARTs did not induce cell-to-cell virus spread in resting or activated CD4 T cell cultures. Collectively, these results provide support for further development of HIVxCD3 DARTs as a promising therapeutic strategy for targeting HIV reservoirs.
    Preview · Article · Nov 2015 · PLoS Pathogens
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    ABSTRACT: Tenofovir alafenamide fumarate (TAF) is an oral phoshonoamidate prodrug of HIV reverse transcriptase nucleotide inhibitor tenofovir (TFV). Previous studies suggested a principal role for the lysosomal serine protease cathepsin A (CatA) in the intracellular activation of TAF. Here we further investigated the role of CatA and other human hydrolases in the metabolism of TAF. Overexpression of CatA or liver carboxylesterase 1 (Ces1) in HEK293T cells increased intracellular TAF hydrolysis 2 and 5-fold, respectively. Knockdown of CatA expression with RNAi in HeLa cells reduced intracellular TAF metabolism 5-fold. Additionally, the anti-HIV activity and the rate of CatA hydrolysis showed good correlation within a large set of TFV phosphonoamidate prodrugs. The covalent HCV protease inhibitors (PIs) telaprevir and boceprevir potently inhibited CatA-mediated TAF activation (IC 50 = 0.27 and 0.16 μM, respectively) in vitro and also reduced its anti-HIV activity in primary human CD4+ T lymphocytes (21 and 3-fold, respectively) at pharmacologically relevant concentrations. In contrast, there was no inhibition of CatA or any significant effect on anti-HIV activity of TAF observed with cobicistat, non-covalent HIV and HCV PIs, or various prescribed inhibitors of host serine proteases. Collectively, these studies confirm that CatA plays a pivotal role in the intracellular metabolism of TAF, whereas the liver esterase Ces1 likely contributes to the hepatic activation of TAF. Moreover, this work demonstrates that a wide range of viral and host PIs with the exception of telaprevir and boceprevir do not interfere with the antiretroviral activity of TAF.
    No preview · Article · Oct 2015 · Antimicrobial Agents and Chemotherapy
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    ABSTRACT: Respiratory syncytial virus (RSV) is the leading cause of bronchiolitis and pneumonia in infants. Effective treatment for RSV infection is a significant unmet medical need. While new RSV therapeutics are now in development, there are very few animal models that mimic the pathogenesis of human RSV, making it difficult to evaluate new disease interventions. Experimental infection of Holstein calves with bovine RSV (bRSV) causes a severe respiratory infection that is similar to human RSV infection, providing a relevant model for testing novel therapeutic agents. In this model, viral load is readily detectable in nasal secretions by qRT-PCR and cumulative symptom scoring together with histopathology evaluations of infected tissue allow for the assessment of disease severity. The bovine RSV model was used to evaluate the antiviral activity of a RSV fusion inhibitor, GS1, which blocks virus entry by inhibiting the fusion of the viral envelope with the host cell membrane. The efficacy of GS1, a close structural analog of GS-5806 that is being developed to treat RSV infection in humans was evaluated in two randomized, blinded, placebo controlled studies in bRSV-infected calves. Intravenous administration of GS1 at 4 mg/kg/day for 7 days starting at 24 h or 72 h post-inoculation provided clear therapeutic benefit by reducing the viral load, disease symptom scores, respiration rates and lung pathology associated with bRSV infection. These data support the use of the bovine RSV model for evaluation of experimental therapeutics for treatment of RSV. Copyright © 2015, American Society for Microbiology. All Rights Reserved.
    Full-text · Article · Jun 2015 · Antimicrobial Agents and Chemotherapy
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    ABSTRACT: Screening of a marine natural products library afforded three new analogues of the tetronic acid containing polyketide abyssomicin family and identified abyssomicin 2 as a selective reactivator of latent HIV virus. Examination of the mode of action of this new latent HIV reactivating agent demonstrated that it functions via a distinct mechanism compared to that of existing reactivating agents and is effective at reactivating latent virus in a subset of primary patient cell lines.
    No preview · Article · Jan 2015 · Organic Letters
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    ABSTRACT: The steps from HIV-1 cytoplasmic entry until integration of the reverse transcribed genome are currently enigmatic. They occur in ill-defined reverse-transcription- and pre-integration-complexes (RTC, PIC) with various host and viral proteins implicated. In this study, we report quantitative detection of functional RTC/PIC by labeling nascent DNA combined with detection of viral integrase. We show that the viral CA (capsid) protein remains associated with cytoplasmic RTC/PIC but is lost on nuclear PIC in a HeLa-derived cell line. In contrast, nuclear PIC were almost always CA-positive in primary human macrophages, indicating nuclear import of capsids or capsid-like structures. We further show that the CA-targeted inhibitor PF74 exhibits a bimodal mechanism, blocking RTC/PIC association with the host factor CPSF6 and nuclear entry at low, and abrogating reverse transcription at high concentrations. The newly developed system is ideally suited for studying retroviral post-entry events and the roles of host factors including DNA sensors and signaling molecules. DOI: http://dx.doi.org/10.7554/eLife.04114.001
    Full-text · Article · Dec 2014 · eLife Sciences
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    ABSTRACT: Tenofovir disoproxil fumarate (TDF) is a widely used antiretroviral agent with favorable efficacy, safety, and tolerability profiles. However, renal adverse events, including the rare Fanconi syndrome (FS), may occur in a small subset of patients treated for HIV infections. The aim of this study was to identify genetic variants that may be associated with TDF-associated FS (TDF-FS). DNA samples collected from 19 cases with TDF-FS and 36 matched controls were sequenced, and genetic association studies were conducted on eight candidate genes: ATP-binding cassette (ABC) transporters ABCC2 (MRP2) and ABCC4 (MRP4), solute carrier family members SLC22A6 (OAT1) and SLC22A8 (OAT3), adenylate kinases 2 (AK2) and 4 (AK4), chloride transporter CIC-5 CLCN5, and Lowe syndrome protein OCRL. The functional effects of a single nucleotide polymorphism (SNP) predicted to alter the transport of tenofovir were then investigated in cells expressing an identified variant of ABCC4. The case group showed a trend toward a higher proportion of rare alleles. Six SNPs in ABCC2 (three SNPs), ABCC4 (one SNP), and OCRL (two SNPs) were associated with TDF-FS case status; however, this association did not remain significant after correction for multiple testing. Six SNPs, present in OCRL (four SNPs) and ABCC2 (two SNPs), were significantly associated with increased serum creatinine levels in the cases, and this association remained significant after multiple test correction (P<2×10). One synonymous SNP in ABCC2 (rs8187707, P=2.10×10, β=-73.3 ml/min/1.73 m) was also significantly associated with the decreased estimated glomerular filtration rate of creatinine among cases. However, these results were driven by rare SNPs present in a small number of severely affected cases. Finally, a previously uncharacterized, nonsynonymous SNP, rs11568694, that was predicted to alter MRP4 function had no significant effect on tenofovir cellular accumulation in vitro. Although no single predictive genetic marker for the development of TDF-FS was identified, the findings from our study suggest that rare variants in multiple genes involved in the renal handling of tenofovir, and/or renal cell homeostasis, may be associated with increased susceptibility to TDF-FS.
    No preview · Article · Dec 2014 · Pharmacogenetics and Genomics

  • No preview · Article · Jul 2014 · Journal of Antivirals and Antiretrovirals
  • Rujuta A Bam · Stephen R Yant · Tomas Cihlar
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    ABSTRACT: Tenofovir alafenamide (TAF) is a novel prodrug of tenofovir that shows enhanced antiretroviral effect and reduced plasma tenofovir exposures at approximately one-tenth the clinically approved dose of tenofovir disoproxil fumarate (TDF). Tenofovir released from TDF undergoes active renal secretion via organic anion transporters (OAT1, OAT3), leading to higher exposure of renal proximal tubules to tenofovir and a potential for renal adverse effects in a small subset of TDF-treated patients. Here we evaluate the interaction of TAF with OAT1 and OAT3 to assess the potential for its active accumulation in proximal tubules. OAT-mediated transport and cytotoxicity (CC50) of TAF and tenofovir were assessed in cells expressing OATs and compared with matched transporter-null cells. While the OAT1 and OAT3 expression increased the tenofovir cellular uptake by >70-fold and 8.2-fold, respectively, the expression of either OAT did not significantly change TAF intracellular accumulation under identical conditions. In addition, whereas tenofovir was significantly more cytotoxic in OAT1 and OAT3-expressing cells (>21 and >3.6 fold-change in CC50 values, respectively), TAF in vitro cytotoxicity showed little to no change upon over-expression of either renal transporter (0.5 to 3.5 fold-change in CC50). Unlike tenofovir, TAF does not interact with renal transporters OAT1 or OAT3, and exhibits no OAT-dependent cytotoxicity. TAF is thus unlikely to actively accumulate in renal proximal tubules in an OAT-dependent manner, supporting the potential for an improved renal safety profile.
    No preview · Article · Apr 2014 · Antiviral therapy
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    ABSTRACT: Persistent latent reservoir of replication-competent proviruses in memory CD4 T cells is a major obstacle to curing HIV infection. Pharmacological activation of HIV expression in latently infected cells is being explored as one of the strategies to deplete the latent HIV reservoir. In this study, we characterized the ability of romidepsin (RMD), a histone deacetylase inhibitor approved for the treatment of T-cell lymphomas, to activate the expression of latent HIV. In an in vitro T-cell model of HIV latency, RMD was the most potent inducer of HIV (EC50 = 4.5 nM) compared with vorinostat (VOR; EC50 = 3,950 nM) and other histone deacetylase (HDAC) inhibitors in clinical development including panobinostat (PNB; EC50 = 10 nM). The HIV induction potencies of RMD, VOR, and PNB paralleled their inhibitory activities against multiple human HDAC isoenzymes. In both resting and memory CD4 T cells isolated from HIV-infected patients on suppressive combination antiretroviral therapy (cART), a 4-hour exposure to 40 nM RMD induced a mean 6-fold increase in intracellular HIV RNA levels, whereas a 24-hour treatment with 1 µM VOR resulted in 2- to 3-fold increases. RMD-induced intracellular HIV RNA expression persisted for 48 hours and correlated with sustained inhibition of cell-associated HDAC activity. By comparison, the induction of HIV RNA by VOR and PNB was transient and diminished after 24 hours. RMD also increased levels of extracellular HIV RNA and virions from both memory and resting CD4 T-cell cultures. The activation of HIV expression was observed at RMD concentrations below the drug plasma levels achieved by doses used in patients treated for T-cell lymphomas. In conclusion, RMD induces HIV expression ex vivo at concentrations that can be achieved clinically, indicating that the drug may reactivate latent HIV in patients on suppressive cART.
    Full-text · Article · Apr 2014 · PLoS Pathogens
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    ABSTRACT: Respiratory syncytial virus (RSV) is the leading cause of hospitalization due to respiratory illness among infants and young children of industrialized countries. There is a lack of understanding of the severe disease mechanisms as well as limited treatment options, none of which are fully satisfactory. This is partly due to lack of a relevant animal model of perinatal RSV infection that mimics moderate to severe disease in infants. We and others have shown mild disease in perinatal lambs with either a bovine or a human A2 strain of RSV. The Memphis 37 clinical strain of human RSV has been used to produce mild to moderate upper respiratory disease in healthy adult volunteers. We hypothesized that the Memphis 37 strain of RSV would infect perinatal lambs and produce clinical disease similar to that in human infants. Perinatal (3- to 5-day-old) lambs were inoculated intranasally with 2 mL/nostril of 1×10(5) focus-forming units (FFU)/mL (n=2) or 2.1×10(8) FFU/mL (n=3) of RSV Memphis 37. Clinical signs, gross and histological lesions, and immune and inflammatory responses were assessed. Memphis 37 caused moderate to severe gross and histologic lesions along with increased mRNA expression of macrophage inflammatory protein. Clinically, four of the five infected lambs had a mild to severe increase in expiratory effort. Intranasally administered RSV strain Memphis 37 infects neonatal lambs with gross, histologic, and immune responses similar to those observed in human infants.
    Full-text · Article · Apr 2014
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    ABSTRACT: Many xenobiotics including the pharmacoenhancer cobicistat increase serum creatinine by inhibiting its renal active tubular secretion without affecting the glomerular filtration rate. This study aimed to define the transporters involved in creatinine secretion, applying that knowledge to establish the mechanism for xenobiotic-induced effects. The basolateral uptake transporters organic anion transporter OAT2 and organic cation transporters OCT2 and OCT3 were found to transport creatinine. At physiologic creatinine concentrations, the specific activity of OAT2 transport was over twofold higher than OCT2 or OCT3, establishing OAT2 as a likely relevant creatinine transporter and further challenging the traditional view that creatinine is solely transported by a cationic pathway. The apical multidrug and toxin extrusion transporters MATE1 and MATE2-K demonstrated low-affinity and high-capacity transport. All drugs known to affect creatinine inhibited OCT2 and MATE1. Similar to cimetidine and ritonavir, cobicistat had the greatest effect on MATE1 with a 50% inhibition constant of 0.99 μM for creatinine transport. Trimethoprim potently inhibited MATE2-K, whereas dolutegravir preferentially inhibited OCT2. Cimetidine was unique, inhibiting all transporters that interact with creatinine. Thus, the clinical observation of elevated serum creatinine in patients taking cobicistat is likely a result of OCT2 transport, facilitating intracellular accumulation, and MATE1 inhibition.Kidney International advance online publication, 19 March 2014; doi:10.1038/ki.2014.66.
    Full-text · Article · Mar 2014 · Kidney International
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    ABSTRACT: Tenofovir alafenamide (TAF) is a novel investigational prodrug of tenofovir (TFV) that permits enhanced delivery of TFV into peripheral blood mononuclear cells (PBMCs) and lymphatic tissues. A critical step in the intracellular metabolic activation of TAF is mediated by the lysosomal protease cathepsin A (CatA). Here we investigated CatA levels together with intracellular metabolism and antiretroviral activity of TAF in primary CD4(+) T lymphocytes (CD4s) and monocyte-derived macrophages (MDMs) isolated from a demographically diverse group of blood donors. CD4s and MDMs were prepared from fresh PBMCs. CatA levels were quantified in cell extracts by monitoring TAF hydrolysis using HPLC. Intracellular TAF metabolites were quantified by HPLC combined with mass spectrometry. Antiviral activities in activated CD4s and MDMs were determined using a HIV-1 single-cycle reporter and p24 antigen production assays, respectively. The levels of CatA and intracellular TAF metabolites differed minimally in CD4s and MDMs among 13 tested donors. TAF was >600-fold and 80-fold more potent than parent TFV in CD4s and MDMs, respectively, and its relative range of antiviral activity across all tested donors was comparable to that of other HIV-1 reverse transcriptase inhibitors, with mean ± SD (range) EC50 values of 11.2 ± 3.2 (6.6 -19.9) nM and 8.8 ± 4.4 (2.5 - 15.7) nM in CD4s and MDMs, respectively. These results indicate consistent intracellular metabolism and antiretroviral potency of TAF in relevant target cells of HIV-1 infection across multiple donors of variable gender, age and ethnicity, supporting further clinical investigation of TAF.
    No preview · Article · Mar 2014 · Antiviral therapy
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    ABSTRACT: An extract of Humicola fuscoatra (UCSC strain no. 108111A) was shown to reactivate latent HIV-1 expression in an in vitro model of central memory CD4+ T cells. We report the bioassay-guided isolation and structure determination of several resorcyclic acid lactones, including four known compounds, radicicol (1, aka. monorden) and pochonins B (2), C (3), and N (4), and three new analogues, radicicols B-D (5-7). Compounds 1-3 and 5 showed moderate activities in the memory T cell model of HIV-1 latency. Radicicol (1) displayed lower potency in reactivating latent HIV-1 (EC50 = 9.1 μM) relative to the HDAC inhibitors apicidin (EC50 = 0.3 μM), romidepsin (EC50 = 0.003 μM), and SAHA (EC50 = 0.6 μM); however, it achieved equivalent maximum efficacy relative to the positive control compounds (98% of SAHA and romidepsin).
    Full-text · Article · Feb 2014 · Journal of Natural Products
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    ABSTRACT: Insertions in the protease (PR) region of human immunodeficiency virus (HIV) represent an interesting mechanism of antiviral resistance against HIV PR inhibitors (PIs). Here, we demonstrate the improved ability of a phosphonate-containing experimental HIV PI, GS-8374, relative to that of other PIs, to effectively inhibit patient-derived recombinant HIV strains bearing PR insertions and numerous other mutations. We correlate enzyme inhibition with the catalytic activities of corresponding recombinant PRs in vitro and provide a biochemical and structural analysis of the PR-inhibitor complex.
    Full-text · Article · Dec 2013 · Journal of Virology
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    ABSTRACT: Human rhinovirus type C (HRV-C) is a newly discovered enterovirus species frequently associated with exacerbation of asthma and other acute respiratory conditions. Until recently, HRV-C could not be propagated in vitro, hampering in-depth characterization of the virus replication cycle and preventing efficient testing of antiviral agents. Herein we describe several sub-genomic RNA replicon systems and a cell culture infectious model for HRV-C that can be used for antiviral screening. The replicon constructs consist of genome sequences from HRVc15, HRVc11, HRVc24, and HRVc25 strains, with the P1 capsid region replaced by a Renilla luciferase coding sequence. Following the replicon RNA transfection into HeLa cells, the constructs produced time-dependent increases in luciferase signal that can be inhibited in a dose-dependent manner by known inhibitors of HRV replication including the 3C protease inhibitor rupintrivir, nucleoside analog inhibitor MK-0608, and PI4-IIIβ kinase inhibitor PIK93. Furthermore, with the exception of pleconaril and pirodavir, the other tested classes of HRV inhibitors blocked the replication of full length HRVc15 and HRVc11 viruses in human airway epithelial cells (HAEs) differentiated in air liquid interface, exhibiting antiviral activities similar to those observed with HRV-16. In summary, this study is the first comprehensive profiling of multiple classes of antivirals against HRV-C and the set of newly developed quantitative HRV-C antiviral assays represent indispensable tools for the identification and evaluation of novel pan-serotype HRV inhibitors.
    Preview · Article · Dec 2013 · Antimicrobial Agents and Chemotherapy
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    ABSTRACT: Respiratory syncytial virus (RSV) is the most common cause of bronchiolitis in infants and young children. A small percentage of these individuals develop severe and even fatal disease. To better understand the pathogenesis of severe disease and develop therapies unique to the less-developed infant immune system, a model of infant disease is needed. The neonatal lamb pulmonary development and physiology is similar to that of infants, and sheep are susceptible to ovine, bovine, or human strains of RSV. RSV grown in Vero (African green monkey) cells has a truncated attachment G glycoprotein as compared to that grown in HEp-2 cells. We hypothesized that the virus grown in HEp-2 cells would cause more severe clinical symptoms and cause more severe pathology. To confirm the hypothesis, lambs were inoculated simultaneously by two different delivery methods (intranasal and nebulized inoculation) with either Vero-grown or HEp-2-grown RSV Memphis 37 (M37) strain of virus to compare viral infection and disease symptoms. Lambs infected with HEp-2 cell-derived virus by either intranasal or nebulization inoculation had significantly higher levels of viral RNA in lungs as well as greater clinical disease including both gross and histopathologic lesions compared to lambs similarly inoculated with Vero-grown virus. Thus, our results provide convincing in vivo evidence for differences in viral infectivity that corroborate previous in vitro mechanistic studies demonstrating differences in the G glycoprotein expression by RSV grown in Vero cells.
    Full-text · Article · Nov 2013 · Viruses
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    ABSTRACT: HIV-1 integrase (IN) is the target for two classes of antiretrovirals: i) the integrase strand-transfer inhibitors (INSTIs) and ii) the non-catalytic site integrase inhibitors (NCINIs). NCINIs bind at the IN dimer interface and are thought to interfere primarily with viral DNA (vDNA) integration in the target cell by blocking IN-vDNA assembly as well as the IN-LEDGF/p75 interaction. Herein we show that treatment of virus-producing cells, but not of mature virions or target cells, drives NCINI antiviral potency. NCINIs target an essential late-stage event in HIV replication that is insensitive to LEDGF levels in the producer cells. Virus particles produced in the presence of NCINIs displayed normal Gag-Pol processing and endogenous reverse transcriptase activity, but were defective at initiating vDNA synthesis following entry into the target cell. NCINI-resistant virus carrying a T174I mutation in the IN dimer interface was less sensitive to the compound-induced late-stage effects, including the reverse transcription block. Wild-type, but not T174I virus, produced in the presence of NCINIs exhibited striking defects in core morphology and an increased level of IN oligomers that was not observed upon treatment of mature cell-free particles. Collectively, these results reveal that NCINIs act through a novel mechanism that is unrelated to the previously observed inhibition of IN activity or IN-LEDGF interaction, and instead involves the disruption of an IN function during HIV-1 core maturation and assembly.
    Full-text · Article · Sep 2013 · PLoS ONE
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    ABSTRACT: Once-daily single-tablet antiretroviral regimen containing tenofovir (TFV) disoproxil fumurate, emtricitabine, elvitegravir and cobicistat (COBI) is an approved combination for the treatment of patients infected with HIV. COBI and TFV have been reported to interact with distinct transporters in renal proximal tubules; while TFV is renally eliminated by a combination of glomerular filtration and tubular secretion via anion transporters OAT1, OAT3 and MRP4, COBI inhibits renal cation transporters, particularly MATE1, resulting in a measurable decrease in the tubular secretion of creatinine. To investigate the potential for a renal drug-drug interaction between TFV and COBI in vitro, the uptake of TFV in the presence and absence of COBI was determined in fresh human renal cortex tissue and in cells expressing the relevant renal transporters. At concentrations exceeding clinical protein-unbound plasma levels, COBI did not significantly inhibit the transport of TFV by the anion transporters OAT1, OAT3 or MRP4 (IC50 values of >15, 6.6 and 8.5 μM, respectively). Conversely, TFV had little or no effect on the cation transporters OCT2 and MATE1 (IC50 > 100 μM). Consistent with studies using individual transporters, no increase in the accumulation of TFV in freshly isolated human renal cortex tissue or renal proximal tubule cells (RPTECs) was observed in the presence of COBI. Finally, COBI alone or in combination with FTC and EVG did not affect the sensitivity to TFV of cultured primary RPTECs or cells co-expressing OAT1 and MRP4. These results illustrate that COBI and TFV interact primarily with distinct renal transporters and indicate a low potential for pharmacokinetic renal drug-drug interaction.
    Full-text · Article · Jul 2013 · Antimicrobial Agents and Chemotherapy

Publication Stats

4k Citations
387.63 Total Impact Points

Institutions

  • 1997-2015
    • Gilead Sciences
      • • Department of Biology
      • • Medicinal Chemistry
      فوستير سيتي، سان ماتيو، كاليفورنيا, California, United States
  • 2011
    • University of Minnesota Duluth
      • College of Pharmacy
      Duluth, Minnesota, United States
  • 1994-2010
    • Academy of Sciences of the Czech Republic
      • Ústav organické chemie a biochemie
      Praha, Hlavni mesto Praha, Czech Republic
  • 2007
    • Novartis Institutes for BioMedical Research
      Cambridge, Massachusetts, United States