Raltegravir has a low propensity to cause clinical drug interactions through inhibition of major drug transporters: an in vitro evaluation

Drug-drug interactions that alter the exposure of glucuronidated drugs: Scope, UDP-glucuronosyltransferase (UGT) enzyme selectivity, mechanisms (inhibition and induction), and clinical significance

Drug-drug interactions (DDIs) arising from the perturbation of drug metabolising enzyme activities represent both a clinical problem and a potential economic loss for the pharmaceutical industry. DDIs involving glucuronidated drugs have historically attracted little attention and there is a perception that interactions are of minor clinical relevance. This review critically examines the scope and aetiology of DDIs that result in altered exposure of glucuronidated drugs. Interaction mechanisms, namely inhibition and induction of UDP-glucuronosyltransferase (UGT) enzymes and the potential interplay with drug transporters, are reviewed in detail, as is the clinical significance of known DDIs. Altered victim drug exposure arising from modulation of UGT enzyme activities is relatively common and, notably, the incidence and importance of UGT induction as a DDI mechanism is greater than generally believed. Numerous DDIs are clinically relevant, resulting in either loss of efficacy or an increased risk of adverse effects, necessitating dose individualisation. Several generalisations relating to the likelihood of DDIs can be drawn from the known substrate and inhibitor selectivities of UGT enzymes, highlighting the importance of comprehensive reaction phenotyping studies at an early stage of drug development. Further, rigorous assessment of the DDI liability of new chemical entities that undergo glucuronidation to a significant extent has been recommended recently by regulatory guidance. Although evidence-based approaches exist for the in vitro characterisation of UGT enzyme inhibition and induction, the availability of drugs considered appropriate for use as 'probe' substrates in clinical DDI studies is limited and this should be research priority.

P-Glycoprotein and Organic Anion Transporter Polypeptide 1B/Breast Cancer Resistance Protein Drug Transporter Activity in Pregnant Women Living With HIV

This study evaluates the influence of pregnancy and HIV infection in conjunction with the use of raltegravir, lamivudine, and tenofovir disoproxil fumarate (combined antiretroviral therapy [cART]) on intestinal P-glycoprotein (P-gp) and hepatic organic anion transporter polypeptide (OATP) 1B1/1B3 and/or breast cancer resistance protein (BCRP) drug transporter activity using rosuvastatin (OATP1B/BCRP) and fexofenadine (P-gp) probes. Single oral doses of 5-mg rosuvastatin and 60-mg fexofenadine were administered to women living with HIV under cART in the third trimester of gestation (n = 15) and postpartum period (n = 10). A control group of 12 healthy nonpregnant women also was investigated. Pharmacokinetic parameters were estimated by using a noncompartmental method and evaluated by t test (P < .05). The rosuvastatin area under the plasma concentration-time curve from time 0 to the last quantifiable concentration (AUC_0-last ) value was higher in the third trimester of pregnancy (19.5 [95%CI, 16.8-22.3] ng • h/mL] when compared to postpartum (13.3 [95%CI, 9.3-17.5] ng • h/mL), while the fexofenadine AUC_0-last values did not differ between the third trimester of pregnancy (738.0 [95%CI, 611.4-864.6] ng • h/mL) and postpartum period (874.9 [95%CI, 408.2-1342.0] ng• h/mL). The rosuvastatin AUC_0-last values did not differ between healthy nonpregnant women (13.8 [95%CI, 10.0-17.6] ng • h/mL) and women living with HIV in the postpartum period (13.3 [95%CI, 9.3-17.5] ng • h/mL), and the fexofenadine AUC_0-last values did not differ between the 2 investigated groups (603.6 [95%CI, 467.5-739.7] ng • h/mL vs 874.9 [95%CI, 408.2-1342.0] ng • h/mL). It is suggested that gestation inhibits the hepatic OATP1B1/1B3 and/or BCRP activity but does not alter intestinal P-gp activity. The influence of HIV infection in conjunction with use of cART on OATP1B/BCRP and intestinal P-gp activity was not observed.

Islatravir Is Not Expected to Be a Victim or Perpetrator of Drug-Drug Interactions via Major Drug-Metabolizing Enzymes or Transporters

Islatravir (MK-8591) is a nucleoside reverse transcriptase translocation inhibitor in development for the treatment and prevention of HIV-1. The potential for islatravir to interact with commonly co-prescribed medications was studied in vitro. Elimination of islatravir is expected to be balanced between adenosine deaminase-mediated metabolism and renal excretion. Islatravir did not inhibit uridine diphosphate glucuronosyltransferase 1A1 or cytochrome p450 (CYP) enzymes CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6, or 3A4, nor did it induce CYP1A2, 2B6, or 3A4. Islatravir did not inhibit hepatic transporters organic anion transporting polypeptide (OATP) 1B1, OATP1B3, organic cation transporter (OCT) 1, bile salt export pump (BSEP), multidrug resistance-associated protein (MRP) 2, MRP3, or MRP4. Islatravir was neither a substrate nor a significant inhibitor of renal transporters organic anion transporter (OAT) 1, OAT3, OCT2, multidrug and toxin extrusion protein (MATE) 1, or MATE2K. Islatravir did not significantly inhibit P-glycoprotein and breast cancer resistance protein (BCRP); however, it was a substrate of BCRP, which is not expected to be of clinical significance. These findings suggest islatravir is unlikely to be the victim or perpetrator of drug-drug interactions with commonly co-prescribed medications, including statins, diuretics, anti-diabetic drugs, proton pump inhibitors, anticoagulants, benzodiazepines, and selective serotonin reuptake inhibitors.

HIV in pregnancy: Mother-to-child transmission, pharmacotherapy, and toxicity

An estimated 1.3 million pregnant women were living with HIV in 2018. HIV infection is associated with adverse pregnancy outcomes and all HIV-positive pregnant women, regardless of their clinical stage, should receive a combination of antiretroviral drugs to suppress maternal viral load and prevent vertical fetal infection. Although antiretroviral treatment in pregnant women has undoubtedly minimized mother-to-child transmission of HIV, several uncertainties remain. For example, while pregnancy is accompanied by changes in pharmacokinetic parameters, relevant data from clinical studies are lacking. Similarly, long-term adverse effects of exposure to antiretrovirals on fetuses have not been studied in detail. Here, we review current knowledge on HIV effects on the placenta and developing fetus, recommended antiretroviral regimens, and pharmacokinetic considerations with particular focus on placental transport. We also discuss recent advances in antiretroviral research and potential effects of antiretroviral treatment on placental/fetal development and programming.

Role of transporters in the disposition of a novel β-lactamase inhibitor: relebactam (MK-7655)

OBJECTIVES

To identify the transporters involved in renal elimination of relebactam, and to assess the potential of relebactam as a perpetrator or victim of drug-drug interactions (DDIs) for major drug transporters.

METHODS

A series of bidirectional transport, uptake and inhibition studies were conducted in vitro using transfected cell lines and membrane vesicles. The inhibitory effects of relebactam on major drug transporters, as well as the inhibitory effects of commonly used antibiotics/antifungals on organic anion transporter (OAT) 3-mediated uptake of relebactam, were assessed.

RESULTS

Relebactam was shown to be a substrate of OAT3, OAT4, and multidrug and toxin extrusion (MATE) proteins MATE1 and MATE2K. Relebactam did not show profound inhibition across a panel of transporters, including organic anion-transporting polypeptides 1B1 and 1B3, OAT1, OAT3, organic cation transporter 2, MATE1, MATE2K, breast cancer resistance protein, multidrug resistance protein 1 and the bile salt export pump. Among the antibiotics/antifungals assessed for potential DDIs, probenecid demonstrated the most potent in vitro inhibition of relebactam uptake; however, such in vitro data did not translate into clinically relevant DDIs, suggesting that relebactam can be co-administered with OAT inhibitors, such as probenecid.

CONCLUSIONS

Overall, relebactam has low potential to be a victim or perpetrator of DDIs with major drug transporters.

Use of a Bile Salt Export Pump Knockdown Rat Susceptibility Model to Interrogate Mechanism of Drug-Induced Liver Toxicity

Inhibition of the bile salt export pump (BSEP) may be associated with clinical drug-induced liver injury, but is poorly predicted by preclinical animal models. Here we present the development of a novel rat model using siRNA knockdown (KD) of Bsep that displayed differentially enhanced hepatotoxicity to 8 Bsep inhibitors and not to 3 Bsep noninhibitors when administered at maximally tolerated doses for 7 days. Bsep KD alone resulted in 3- and 4.5-fold increases in liver and plasma levels, respectively, of the sum of the 3 most prevalent taurine conjugated bile acids (T3-BA), approximately 90% decrease in plasma and liver glycocholic acid, and a distinct bile acid regulating gene expression pattern, without resulting in hepatotoxicity. Among the Bsep inhibitors, only asunaprevir and TAK-875 resulted in serum transaminase and total bilirubin increases associated with increases in plasma T3-BA that were enhanced by Bsep KD. Benzbromarone, lopinavir, and simeprevir caused smaller increases in plasma T3-BA, but did not result in hepatotoxicity in Bsep KD rats. Bosentan, cyclosporine A, and ritonavir, however, showed no enhancement of T3-BA in plasma in Bsep KD rats, as well as Bsep noninhibitors acetaminophen, MK-0974, or clarithromycin. T3-BA findings were further strengthened through monitoring TCA-d4 converted from cholic acid-d4 overcoming interanimal variability in endogenous bile acids. Bsep KD also altered liver and/or plasma levels of asunaprevir, TAK-875, TAK-875 acyl-glucuronide, benzbromarone, and bosentan. The Bsep KD rat model has revealed differences in the effects on bile acid homeostasis among Bsep inhibitors that can best be monitored using measures of T3-BA and TCA-d4 in plasma. However, the phenotype caused by Bsep inhibition is complex due to the involvement of several compensatory mechanisms.

Assessment of drug interaction potential between the HCV direct-acting antiviral agents elbasvir/grazoprevir and the HIV integrase inhibitors raltegravir and dolutegravir

BACKGROUND

Elbasvir/grazoprevir is a once-daily fixed-dose combination therapy for the treatment of chronic HCV infection, including HCV/HIV coinfection.

OBJECTIVES

To evaluate the pharmacokinetic interaction of elbasvir and grazoprevir with raltegravir or dolutegravir.

METHODS

Three open-label trials in healthy adult participants were conducted. In the raltegravir trials, participants received a single dose of raltegravir 400 mg, a single dose of elbasvir 50 mg or grazoprevir 200 mg, and raltegravir with either elbasvir or grazoprevir. In the dolutegravir trial, participants received a single dose of dolutegravir 50 mg alone or co-administered with once-daily elbasvir 50 mg and grazoprevir 200 mg.

RESULTS

The raltegravir AUC0-∞ geometric mean ratio (GMR) (90% CI) was 1.02 (0.81-1.27) with elbasvir and 1.43 (0.89-2.30) with grazoprevir. Dolutegravir AUC0-∞ GMR (90% CI) was 1.16 (1.00-1.34) with elbasvir and grazoprevir. The elbasvir AUC0-∞ GMR (90% CI) was 0.81 (0.57-1.17) with raltegravir and 0.98 (0.93-1.04) with dolutegravir. The grazoprevir AUC0-24 GMR (90% CI) was 0.89 (0.72-1.09) with raltegravir and 0.81 (0.67-0.97) with dolutegravir.

CONCLUSIONS

Elbasvir or grazoprevir co-administered with raltegravir or dolutegravir resulted in no clinically meaningful drug-drug interactions and was generally well tolerated. These results support the assertion that no dose adjustments for elbasvir, grazoprevir, raltegravir or dolutegravir are needed for co-administration in HCV/HIV-coinfected people.

Polyethlyene Glycol 200 can Protect Rats against Drug-Induced Kidney Toxicity through Inhibition of the Renal Organic Anion Transporter 3

MK-7680, a cyclic nucleotide prodrug, caused significant kidney tubule injury in female rats when administered orally at 1000 mg/kg/day for 2 weeks using 10% Polysorbate 80 as vehicle. However, kidney injury was absent when MK-7680 was administered at the same dose regimen using 100% Polyethylene Glycol 200 (PEG 200) as the vehicle. Subsequent investigations revealed that MK-7680 triphosphate concentrations in kidney were much lower in rats treated with MK-7680 using PEG 200 compared to 10% Polysorbate 80 vehicle while plasma exposures of MK-7680 prodrug were similar. In vitro studies demonstrated that PEG 200 is an inhibitor of human renal uptake transporter organic anion transporter 3 (OAT3), of which MK-7680 is a substrate. Furthermore, PEG 200 and PEG 400 were found to interfere in vitro with human renal transporters OAT3, organic cation transporter (OCT) 2, multidrug resistance-associated protein (MRP) 2 and 4, and multidrug and toxin extrusion protein (MATE) 1 and 2K, but not OAT1. These results support a conclusion that PEG 200 may prevent MK-7680-induced kidney injury by inhibiting its active uptake into proximal tubular cells by OAT3. Caution should be exercised therefore when using PEGs as vehicles for toxicity assessment for compounds that are substrates of renal transporters.

In Vitro Evaluation of the Drug Interaction Potential of Doravirine

Doravirine is a novel nonnucleoside reverse transcriptase inhibitor for the treatment of human immunodeficiency virus type 1 infection. In vitro studies were conducted to assess the potential for drug interactions with doravirine via major drug-metabolizing enzymes and transporters. Kinetic studies confirmed that cytochrome P450 3A (CYP3A) plays a major role in the metabolism of doravirine, with ∼20-fold-higher catalytic efficiency for CYP3A4 versus CYP3A5. Doravirine was not a substrate of breast cancer resistance protein (BCRP) and likely not a substrate of organic anion transporting polypeptide 1B1 (OATP1B1) or OATP1B3. Doravirine was not a reversible inhibitor of major CYP enzymes (CYP1A2, -2B6, -2C8, -2C9, -2C19, -2D6, and -3A4) or of UGT1A1, nor was it a time-dependent inhibitor of CYP3A4. No induction of CYP1A2 or -2B6 was observed in cultured human hepatocytes; small increases in CYP3A4 mRNA (≤20%) were reported at doravirine concentrations of ≥10 μM but with no corresponding increase in enzyme activity. In vitro transport studies indicated a low potential for interactions with substrates of BCRP, P-glycoprotein, OATP1B1 and OATP1B3, the bile salt extrusion pump (BSEP), organic anion transporter 1 (OAT1) and OAT3, organic cation transporter 2 (OCT2), and multidrug and toxin extrusion 1 (MATE1) and MATE2K proteins. In summary, these in vitro findings indicate that CYP3A4 and CYP3A5 mediate the metabolism of doravirine, although with different catalytic efficiencies. Clinical trials reported elsewhere confirm that doravirine is subject to drug-drug interactions (DDIs) via CYP3A inhibitors and inducers, but they support the notion that DDIs (either direction) are unlikely via other major drug-metabolizing enzymes and transporters.

Renal Drug Transporters and Drug Interactions

Transporters in proximal renal tubules contribute to the disposition of numerous drugs. Furthermore, the molecular mechanisms of tubular secretion have been progressively elucidated during the past decades. Organic anions tend to be secreted by the transport proteins OAT1, OAT3 and OATP4C1 on the basolateral side of tubular cells, and multidrug resistance protein (MRP) 2, MRP4, OATP1A2 and breast cancer resistance protein (BCRP) on the apical side. Organic cations are secreted by organic cation transporter (OCT) 2 on the basolateral side, and multidrug and toxic compound extrusion (MATE) proteins MATE1, MATE2/2-K, P-glycoprotein, organic cation and carnitine transporter (OCTN) 1 and OCTN2 on the apical side. Significant drug-drug interactions (DDIs) may affect any of these transporters, altering the clearance and, consequently, the efficacy and/or toxicity of substrate drugs. Interactions at the level of basolateral transporters typically decrease the clearance of the victim drug, causing higher systemic exposure. Interactions at the apical level can also lower drug clearance, but may be associated with higher renal toxicity, due to intracellular accumulation. Whereas the importance of glomerular filtration in drug disposition is largely appreciated among clinicians, DDIs involving renal transporters are less well recognized. This review summarizes current knowledge on the roles, quantitative importance and clinical relevance of these transporters in drug therapy. It proposes an approach based on substrate-inhibitor associations for predicting potential tubular-based DDIs and preventing their adverse consequences. We provide a comprehensive list of known drug interactions with renally-expressed transporters. While many of these interactions have limited clinical consequences, some involving high-risk drugs (e.g. methotrexate) definitely deserve the attention of prescribers.

Multiple Drug Transporters Are Involved in Renal Secretion of Entecavir

Entecavir (ETV) is a first-line antiviral agent for the treatment of chronic hepatitis B virus infection. Renal excretion is the major elimination path of ETV, in which tubular secretion plays the key role. However, the secretion mechanism has not been clarified. We speculated that renal transporters mediated the secretion of ETV. Therefore, the aim of our study was to elucidate which transporters contribute to the renal disposition of ETV. Our results revealed that ETV (50 μM) remarkably reduced the accumulation of probe substrates in MDCK cells stably expressing human multidrug and toxin efflux extrusion proteins (hMATE1/2-K), organic cation transporter 2 (hOCT2), and carnitine/organic cation transporters (hOCTNs) and increased the substrate accumulation in cells transfected with multidrug resistance-associated protein 2 (hMRP2) or multidrug resistance protein 1 (hMDR1). Moreover, ETV was proved to be a substrate of the above-described transporters. In transwell studies, the transport of ETV in MDCK-hOCT2-hMATE1 showed a distinct directionality from BL (hOCT2) to AP (hMATE1), and the cellular accumulation of ETV in cells expressing hMATE1 was dramatically lower than that of the mock-treated cells. The accumulation of ETV in mouse primary renal tubular cells was obviously affected by inhibitors of organic anion transporter 1/3 (Oat1/3), Oct2, Octn1/2, and Mrp2. Therefore, the renal uptake of ETV is likely mediated by OAT1/3 and OCT2 while the efflux is mediated by MATEs, MDR1, and MRP2, and OCTN1/2 may participate in both renal secretion and reabsorption.

Switching to Raltegravir From a Virologically Effective Boosted Protease Inhibitor Regimen: A Comparative Effectiveness Analysis From the French Hospital Database on HIV (FHDH-ANRS CO4)

BACKGROUND

In individuals with viral load (VL) suppression on a boosted protease inhibitor (PI) regimen, a switch to raltegravir (RAL) can be an option in case of comorbidities, but the SWITCHMRK trials challenged this strategy. Here, among individuals with VL suppression on a boosted PI, we compared outcomes between those who continued on the same regimen and those who switched to RAL.

METHODS

In this cohort study from the French Hospital Database on HIV, each individual who switched to RAL was matched with up to 3 individuals who continued PI, were being followed up during the calendar period of the switch, and had the same duration of VL suppression (both ±6 months). The primary endpoint was a composite endpoint of hospitalization, or AIDS event or death, and secondary endpoints the immunovirologic responses. To control for measured confounders, the inverse probability treatment weighting (IPTW) method was applied to estimate hazards ratios between the 2 groups.

RESULTS

We matched 282 RAL switchers with 838 nonswitchers. Although several variables differed significantly between the groups, including a higher prevalence of comorbidities in the RAL group, the IPTW method yielded standardized differences <10% for all variables. After IPTW, there was no difference in the risk of hospitalization or AIDS event or death between the 2 groups (13.6% and 10.5%, respectively; hazard ratio, 1.16 [95% confidence interval, .74-1.83]) and no difference in the likelihood of virologic failure or CD4 cell gain.

CONCLUSIONS

In individuals with controlled VL on a boosted PI regimen who switched to RAL, none of the endpoints differed with nonswitchers after IPTW.

Role and modulation of drug transporters in HIV-1 therapy

Current treatment of human immunodeficiency virus type-1 (HIV-1) infection involves a combination of antiretroviral drugs (ARVs) that target different stages of the HIV-1 life cycle. This strategy is commonly referred to as highly active antiretroviral therapy (HAART) or combined antiretroviral therapy (cART). Membrane-associated drug transporters expressed ubiquitously in mammalian systems play a crucial role in modulating ARV disposition during HIV-1 infection. Members of the ATP-binding cassette (ABC) and solute carrier (SLC) transporter superfamilies have been shown to interact with ARVs, including those that are used as part of first-line treatment regimens. As a result, the functional expression of drug transporters can influence the distribution of ARVs at specific sites of infection. In addition, pathological factors related to HIV-1 infection and/or ARV therapy itself can alter transporter expression and activity, thus further contributing to changes in ARV disposition and the effectiveness of HAART. This review summarizes current knowledge on the role of drug transporters in regulating ARV transport in the context of HIV-1 infection.

The Complexities of Interpreting Reversible Elevated Serum Creatinine Levels in Drug Development: Does a Correlation with Inhibition of Renal Transporters Exist?

In humans, creatinine is formed by a multistep process in liver and muscle and eliminated via the kidney by a combination of glomerular filtration and active transport. Based on current evidence, creatinine can be taken up into renal proximal tubule cells by the basolaterally localized organic cation transporter 2 (OCT2) and the organic anion transporter 2, and effluxed into the urine by the apically localized multidrug and toxin extrusion protein 1 (MATE1) and MATE2K. Drug-induced elevation of serum creatinine (SCr) and/or reduced creatinine renal clearance is routinely used as a marker for acute kidney injury. Interpretation of elevated SCr can be complex, because such increases can be reversible and explained by inhibition of renal transporters involved in active secretion of creatinine or other secondary factors, such as diet and disease state. Distinction between these possibilities is important from a drug development perspective, as increases in SCr can result in the termination of otherwise efficacious drug candidates. In this review, we discuss the challenges associated with using creatinine as a marker for kidney damage. Furthermore, to evaluate whether reversible changes in SCr can be predicted prospectively based on in vitro transporter inhibition data, an in-depth in vitro-in vivo correlation (IVIVC) analysis was conducted for 16 drugs with in-house and literature in vitro transporter inhibition data for OCT2, MATE1, and MATE2K, as well as total and unbound maximum plasma concentration (Cmax and Cmax,u) data measured in the clinic.

Reduced raltegravir clearance in HIV-infected liver transplant recipients: an unexpected interaction with immunosuppressive therapy?

OBJECTIVES

Liver transplantation (LTx) is considered a safe procedure in selected HIV-infected patients. In this clinical setting raltegravir is the antiretroviral of choice due to its optimal tolerability and its negligible interactions with immunosuppressive drugs. We aimed at providing data on the pharmacokinetics of raltegravir in LTx recipients, on which the available information is inconclusive.

METHODS

In this retrospective multicentre study we characterized the pharmacokinetics of raltegravir in a consecutive series of HIV-infected LTx recipients referred to our laboratory for therapeutic drug monitoring (TDM) and compared the obtained profiles with those collected from a control group of HIV-infected patients.

RESULTS

Seventeen HIV-infected LTx patients were considered. LTx recipients had significantly higher raltegravir AUC0-12 compared with the control group of HIV-infected patients [14 314 (11 627-19 998) versus 8795 (5218-12 954) ng·h/mL; P < 0.01]. Two LTx patients experienced moderate increments in serum transaminases, nausea and vomiting that improved after raltegravir dose reduction.

CONCLUSIONS

High raltegravir exposure and acceptable safety profile were observed in HIV-infected LTx recipients. Our results highlight that some patients may obtain an advantage from TDM-guided raltegravir dose adjustments with potential benefits in terms of drug tolerability.

Raltegravir plus two nucleoside analogues as combination antiretroviral therapy in HIV-infected patients who require cancer chemotherapy

BACKGROUND

There are few data on the best combination antiretroviral therapy in patients with HIV infection who need cancer chemotherapy because of drug-drug interactions and increased risk of toxic effects.

METHODS

We evaluated the safety, efficacy and interactions of a raltegravir (RAL)-based regimen in 30 HIV-infected patients who received antineoplastic agents.

RESULTS

A total of 17 patients had a non-AIDS-defining malignancy (7 with Hodgkin disease) and 13 had an HIV-related cancer (9 non-Hodgkin lymphoma, 2 Kaposi sarcoma and 2 anal cancer). Overall, they received 49 cycles of chemotherapy with 19 different antineoplastic drugs, including antimetabolites in 4 patients (5-FU, gemcitabine), alkylating agents in 10 cases (cyclophosphamide, ifosfamide), vinca alkaloids in 17 patients (vincristine, vinblastine), anti-tumour antibiotics in 18 cases (doxorubicin), cisplatin or carboplatin in 6, and monoclonal antibodies in 13 patients (rituximab, trastuzumab, cetuximab). Six patients modified the doses of antineoplastic agents due to toxicity not related to raltegravir. During a median follow-up of 67.8 patient-years (median 170 days in concomitant therapy) there was only 1 case of virological failure and no patient discontinued RAL. Geometric mean trough levels of RAL were 143 ng/ml (79-455). There were no opportunistic infections, median CD4(+) T-cell count increased by 49 cells/ml and four (13%) patients died during the study (not related to AIDS progression).

CONCLUSIONS

Our results show that a RAL-based regimen is safe and effective in patients requiring chemotherapy, irrespective of type and of duration of chemotherapy.

Raltegravir permeability across blood-tissue barriers and the potential role of drug efflux transporters

The objectives of this study were to investigate raltegravir transport across several blood-tissue barrier models and the potential interactions with drug efflux transporters. Raltegravir uptake, accumulation, and permeability were evaluated in vitro in (i) P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), multidrug resistance-associated protein 1 (MRP1), or MRP4-overexpressing MDA-MDR1 (P-gp), HEK-ABCG2, HeLa-MRP1, or HEK-MRP4 cells, respectively; (ii) cell culture systems of the human blood-brain (hCMEC/D3), mouse blood-testicular (TM4), and human blood-intestinal (Caco-2) barriers; and (iii) rat jejunum and ileum segments using an in situ single-pass intestinal perfusion model. [(3)H]Raltegravir accumulation by MDA-MDR1 (P-gp) and HEK-ABCG2-overexpressing cells was significantly enhanced in the presence of PSC833 {6-[(2S,4R,6E)-4-methyl-2-(methylamino)-3-oxo-6-octenoic acid]-7-L-valine-cyclosporine}, a P-gp inhibitor, or Ko143 [(3S,6S,12aS)-1,2,3,4,6,7,12,12a-octahydro-9-methoxy-6-(2-methylpropyl)-1,4-dioxopyrazino[1',2':1,6]pyrido[3,4-b]indole-3-propanoic acid 1,1-dimethylethyl ester], a BCRP inhibitor, suggesting the inhibition of a P-gp- or BCRP-mediated efflux process, respectively. Furthermore, [(3)H]raltegravir accumulation by human cerebral microvessel endothelial hCMEC/D3 and mouse Sertoli TM4 cells was significantly increased by PSC833 and Ko143. In human intestinal Caco-2 cells grown on Transwell filters, PSC833, but not Ko143, significantly decreased the [(3)H]raltegravir efflux ratios. In rat intestinal segments, [(3)H]raltegravir in situ permeability was significantly enhanced by the concurrent administration of PSC833 and Ko143. In contrast, in the transporter inhibition assays, raltegravir (10 to 500 μM) did not increase the accumulation of substrate for P-gp (rhodamine-6G), BCRP ([(3)H]mitoxantrone), or MRP1 [2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF)] by MDA-MDR1 (P-gp)-, HEK-ABCG2-, or HeLa-MRP1-overexpressing cells, respectively. Our data suggest that raltegravir is a substrate but not an inhibitor of the drug efflux transporters P-gp and BCRP. These transporters might play a role in the restriction of raltegravir permeability across the blood-brain, blood-testicular, and blood-intestinal barriers, potentially contributing to its low tissue concentrations and/or low oral bioavailability observed in the clinic setting.