Chiara Resnati

Prolonged inductive effect of rifampicin on linezolid exposure

Sir, Some studies have recently shown that concomitant rifampicin administration significantly reduces linezolid concentrations [1–3]. However, it is currently unknown for how long such effect may persist and, most importantly, when linezolid could be safely administered to guarantee optimal drug exposure in patients previously treated with rifampicin. Here, we describe a patient treated for chronic osteomyelitis initially underexposed to linezolid 2 weeks after rifampicin discontinuation. On September 2014, a young Caucasian man was referred to the Department of Infectious Diseases of our hospital for chronic osteomyelitis involving the tibial plateau secondary to a car accident. In the past 3 years, the patient had been treated with several antibiotic regimens based on positive swab cultures from leg cutaneous fistulas (methicillin-susceptible and then resistant Staphylococcus aureus, Acinetobacter baumannii/haemolyticus) without complete resolution of the infection. Since October 2012, the patient was onmaintenance therapy with rifampicin 600 mg once daily and doxycycline 100 mg twice daily. On the 7th of October 2014, given the poor response to therapy and in vitro susceptibility of the pathogens to linezolid (MIC <2 mg/L), this regimen was replaced by linezolid 600 mg twice daily. Therapeutic drug monitoring (TDM) of linezolid trough concentration on a blood sample drawn 9 days after stopping rifampicin (collected 12 h after the evening drug dose and just before the morning drug intake) retrieved a linezolid concentration of 0.6 mg/L. The patient was not concomitantly taking agents inducing (e.g., St John’s wort) linezolid. We decided to maintain linezolid at the same dose, and a blood sample repeated on October 24th revealed a linezolid trough concentration of 1.1 mg/L. Concomitantly, the patient showed a progressive response to linezolid therapy (mild reduction of C-reactive protein). In order to better investigate the adequacy of exposure of the patient to linezolid, we performed an intensive pharmacokinetic evaluation a week later, showing linezolid trough concentration and AUC0–24 of 1.4 mg/L and 142.8 mg*h/ mL, respectively. This last linezolid trough concentration was similar to previous values (June 6th, 2012—1.4 mg/L; June 24th, 2012—1.5 mg/L) measured when the patient was treated with linezolid 600 mg twice daily for swab samples from the fistula cultured positive for MRSA. At the last visit (November 27th, 2014), linezolid trough concentration was 1.5 mg/L. Due to a new increase of inflammatory markers and the worsening of the follow-up CT scan, surgical debridement has been scheduled for January 2015. In vitro studies documented that rifampicin-inducible drugmetabolizing enzymes have a very minor contribution to C. Gervasoni (*) Department of Infectious Diseases, L. Sacco University Hospital, Via GB Grassi 74, 20157 Milan, Italy e-mail: cristina.gervasoni@unimi.it

Effect of Cobicistat on Tenofovir Disoproxil Fumarate (TDF): What Is True for TAF May Also Be True for TDF

Background: The dose of tenofovir alafenamide is reduced from 25 to 10 mg daily when given with boosting agents. However, such dose reduction has never been adopted for tenofovir disoproxil fumarate (TDF). In this study, we aim to quantify the effect of cobicistat (COBI) both on tenofovir concentrations and TDF durability in real life setting. Methods: HIV-positive patients receiving TDF-containing antiretroviral therapies with at least 1 assessment of tenofovir plasma trough concentrations were included in the study. Univariate and multivariate regression analyses were performed considering tenofovir concentration as the dependent variable and clinical characteristics as independent covariates. Subsequently, survival and Cox analyses were performed considering as the primary outcome TDF discontinuation for any reasons. Results: Patients were given TDF with protease inhibitors/ritonavir (n = 212), non–nucleoside reverse transcriptase inhibitors (n = 176), integrase inhibitors (dolutegravir or raltegravir, n = 46), or with elvitegravir/COBI (ELV/COBI) (n = 76). By multivariate analysis, concomitant antiretroviral therapies resulted significantly associated with tenofovir levels, with the highest drug concentrations measured in patients given ELV/COBI. By survival analysis, we found that patients given TDF with ELV/COBI had the lowest rate of drug durability. Overall, these patients had a 2.3-fold increased risk to experience TDF discontinuation. Conclusions: Coadministration with COBI resulted in significantly higher tenofovir concentrations and higher TDF discontinuation compared with other antiretroviral regimens. Accordingly, the possibility that the lack of proper dose adjustment for TDF when given with COBI might have biased the safety comparisons with tenofovir alafenamide during registrative trials cannot be ruled out.

Effect of Legal Status on the Early Treatment Outcomes of Migrants Beginning Combined Antiretroviral Therapy at an Outpatient Clinic in Milan, Italy.

Objective: In a setting of free access to HIV care, we compared the early treatment outcomes of HIV-infected undocumented migrants (UMs), documented migrants (DMs), and Italian subjects. Methods: The clinical data of 640 Italians and 245 migrants who started combined antiretroviral therapy (cART) at an HIV clinic in Milan, Italy, were reviewed. The migrants were mainly Latin Americans (83 DMs and 56 UMs) or sub-Saharan Africans (52 DMs and 11 UMs), but a minority were of other origin (33 DMs and 10 UMs). Retention in follow-up and HIV suppression were compared between UMs, DMs, and natives 12 months ± 90 days after start of cART. Results: There were no significant between-group differences in the stage of HIV infection at the start of cART or the type of regimen received. The Latin American DMs and UMs included a higher proportion of transgender women than the other ethnic groups (P < 0.001). The UMs were less frequently followed up after 12 months than the DMs and natives (P = 0.004) and were more frequently permanently lost to follow-up (P < 0.001). UM status was an independent predictor of lost to follow-up (adjusted odds ratio 8.05, P < 0.001). The DMs and UMs were less frequently HIV suppressed after 12 months than the natives (78% and 80.7% vs 90.5%, P = 0.001), and Latin American migrants were significantly less likely to be virologically suppressed than the natives (adjusted odds ratio 0.30, P = 0.001). Conclusions: Despite their free access to cART, subgroups of migrants facing multiple levels of vulnerability still have difficulties in gaining optimal HIV care.

Abacavir-induced liver toxicity

Abacavir-induced liver toxicity is a rare event almost exclusively occurring in HLA B*5701-positive patients. Herein, we report one case of abnormal liver function tests occurring in a young HLA B*5701-negative woman on a stable nevirapine-based regimen with no history of liver problems or alcohol abuse after switching to abacavir from tenofovir. We also investigated the reasons for abacavir discontinuation in a cohort of patients treated with abacavir-lamivudine-nevirapine.

Comparison of the pharmacokinetics of raltegravir given at 2 doses of 400 mg by swallowing versus one dose of 800 mg by chewing in healthy volunteers: a randomized, open-label, 2-period, single-dose, crossover phase 1 study.

Background: The pharmacokinetics of raltegravir (RAL) in HIV patients is characterized by high interindividual and intraindividual variability. We documented previously that HIV patients taking RAL at 400 mg bid by chewing the tablets had significantly higher drug absorption and reduced pharmacokinetic variability than patients taking the drug by swallowing the tablets. This study extends our previous findings. Methods: An open-label, 2-period crossover study compared the pharmacokinetics of 2 doses of RAL given at 400 mg every 12 hours (that mimics a bid administration) by swallowing with 1 dose of 800 mg (that mimics a qd administration) by chewing the tablets in 12 healthy volunteers. RAL plasma concentrations were measured by a chromatographic method coupled with mass spectrometry. Results: Subjects taking RAL by chewing had significantly higher drug exposure (RAL area under the curve[AUC]0–24: 40722 ± 14843 versus 21753 ± 12229 ng·h/mL, P < 0.0001) and reduced pharmacokinetic variability compared with those taking the drug by swallowing the whole tablet, with no difference in the minimum RAL concentrations (RAL Cmin: 36 ± 23 versus 43 ± 23 ng/mL, P = 0.298). Subjects taking RAL by chewing the tablets had significantly higher drug absorption and reduced pharmacokinetic variability compared with those taking the drug by swallowing. No differences were observed in the minimum RAL concentrations. Conclusions: RAL at 800 mg once daily by chewing the tablets may represent a novel therapeutic option for the treatment of HIV being associated with higher drug absorption, reduced pharmacokinetic variability, and potentially better compliance compared with patients swallowing the 400-mg bid intact tablets.

Evaluation of the concentrations of psychotropic drugs in HIV-infected versus HIV-negative patients: Potential implications for clinical practice

Abstract Objectives: The management of psychiatric illness in HIV-infected patients is clinically challenging because of the risk of potential drug–drug interactions. Here, we aimed to measure the antidepressant and/or antipsychotic drug concentrations in HIV-infected patients during routine outpatient visits. Methods: Six hundred HIV-infected patients were screened during the first 15 months after the introduction of our outpatient polytherapy management service in a search for subjects treated with psychotropic drugs for at least 3 months. The distribution of psychotropic drug concentrations in HIV-infected patients was compared with that observed in a control group of HIV-negative patients monitored over the same period. Results: The search identified 82 HIV-infected patients concomitantly receiving antiretroviral and psychotropic drug treatment, 55% of whom had plasma psychotropic drug concentrations that were below minimum effective levels. The same result was found in only 26% of the samples taken from HIV-negative patients. These results were not affected by patients’ gender, age, adherence to therapies or drug–drug interactions. Conclusions: A higher rate of sub-therapeutic antidepressant and/or antipsychotic drugs concentrations were found in HIV-infected patients. The creation of multidiscliplinary specialist teams may contribute to improving the management of such complex patients.

The impact of gastrectomy on the pharmacokinetics of atazanavir and tenofovir

Sir, Poor drug absorption after gastric resection has been documented in some instances. This happens because patients who underwent major gastric resection have decreased surface area for drug absorption, increased pH, and accelerated gastric emptying, all of which can contribute to alter the pharmacokinetics of some but not all molecules, according to their chemico–physical properties [1]. Indeed, the rate and extent of absorption of drugs that are highly lipophilic, require acidic pH for dissolution, undergo entero-hepatic recirculation or, more in general, have low bioavailability are more likely to be impacted by a total gastrectomy [1]. This may be relevant for antiretroviral medications because their adequate exposure is critical to success and to prevent the development of resistance [2, 3]. Accordingly, if limited gastrointestinal drug absorption takes place, the patients may experience suboptimal drug exposure increasing the risk of virologic failure. Here we deal with the pharmacokinetics of atazanavir and tenofovir in an HIV-infected patient before and after total gastrectomy. A 56-year-old HIV-infected man was on maintenance combined antiretroviral therapy with atazanavir/ritonavir 300/ 100 mg once daily plus tenofovir/emtricitabine since 2011. His HIV-RNA in plasma was not detectable (<37 copies/mL) by years; however, CD4+ cell count has never been higher than 300 cells/mL. Increased bilirubin levels (around 5.0 and 0.8 mg/dL of total and direct bilirubin, respectively) was the only alteration in the laboratory examinations recorded after starting antiretroviral therapy, associated with mild clinical signs of jaundice and scleral icterus. Atazanavir and tenofovir trough concentrations measured periodically (at least once per year) were always within 600–700 and 90–120 ng/mL, respectively. On August 2015, the patient was diagnosed with gastric adenocarcinoma and underwent total gastrectomy followed by an oesophagojejunostomy with a Roux-enY reconstruction and chemotherapy with intravenous oxaliplatin and fluorouracil administrated for a total of 12 cycles. A few days after surgery, total and direct bilirubin levels dropped and stabilized to less than 1.5 and 0.7 mg/dL, respectively. Two pharmacokinetic evaluations performed 1 and 3 months after chemotherapy revealed a significant decrease in atazanavir trough concentrations (178 and 150 ng/mL, respectively) but similar tenofovir trough concentrations (89 and 119 ng/mL, respectively). Our patient did never assume drugs known to interfere with atazanavir pharmacokinetics (including herbal remedies) before and after gastrectomy and had a history of optimal compliance to antiretroviral therapy. At the last available follow-up (January 2017), plasma HIV-RNA and CD4+ T-cell count resulted <37 copies/mL and 359 cells/mL, respectively. Atazanavir is classified as a class II drug according to the Biopharmaceutics Classification Systems (BCS), given its poor water solubility and high permeability (with a log p of 4.11) [4]. Due to this intense lipophilicity, the oral absorption of atazanavir is characterized by both a pH-dependent dissolution and rapid first-pass metabolism in liver by cytochrome 3A (CYP3A) isoenzymes, which result in low systemic bioavailability [5]. As exemplified in our patient, the limited systemic bioavailability of atazanavir can be further reduced by gastrectomy, a clinical condition characterized by increased gastrointestinal pH. Indeed, when pH increases, there is consequent increment in the ionized form of atazanavir, which is * Cristina Gervasoni cristina.gervasoni@unimi.it

Pharmacogenetics-based optimisation of atazanavir treatment: potential role of new genetic predictors

Abnormalities in liver function are described in HIV-1-infected patients treated with atazanavir (ATV), an HIV-1 protease inhibitor that is usually boosted with ritonavir (r) to inhibit drug metabolism and increase its bioavailability [1]. Patients treated with ATV/r frequently show increased bilirubin plasma concentrations due to ATV-inhibition of the UDP-glucuronosyl transferase (UGT) 1A1 gene [2]. This is enhanced in patients carrying the UGT1A1 promoter tandem TA repeat (UGT1A1*28), which has been associated with unconjugated hyperbilirubinemia [3]. ATV is mainly metabolised by CYP3A enzymes, whose activity has been shown to be significantly affected by CYP3A5*3/rs776746 or CYP3A4*22/rs35599367 polymorphisms [4, 5]. Given that the above mentioned polymorphisms fail to explain all the variability in CYP3A activity, additional variants outside the CYP3A locus may be involved. In particular, the peroxisome proliferatoractivated receptor alpha (PPARA) gene acts as a CYP3A trans-acting factor; the knockdown of PPAR-α resulted in up to ~70% reduction in CYP3A4 mRNA levels and the homozygous carrier of the rs4253728 variant allele expresses less PPAR-α protein in the liver [6]. The correlation between the expressions of PPARA and UGT1A, as recently reported by Nie et al. [7], is also noteworthy. Based on the above, we studied the effect of genetic variants in the UGT1A1, CYP3A4, CYP3A5 and PPARA genes on the drug pharmacokinetics and drug safety in patients on maintenance ATV-based antiretroviral therapy. Patients provided their informed consent prior to undergoing pharmacogenetics analysis. Given the retrospective observational nature of the present investigation, no formal approval from the local ethics committee was required according to the legislation of the national drug agency. A total of 129 HIV-patients treated with ATV/RTV 300/100 mg/day were included. Genomic DNA was isolated from peripheral blood cells using an automatic DNA extraction system (Maxwell® 16 System, Promega, Madison, WI, USA), in accordance with the manufacturer’s instructions. Single-nucleotide polymorphisms (SNPs) were determined by Real-Time PCR, using LightSNiP assay (TIB-MolBiol, Berlin, Germany), on the LightCycler 480 instrument (Roche, Mannheim, Germany). We evaluated the SNPs in UGT1A1 (*28), CYP3A4 (rs35599367), CYP3A5 (rs776746) and PPARA (rs4253728) genes. Blood trough samples drawn into EDTA-containing Vacutainers were collected from all patients immediately before the next drug intake. Plasma ATV concentrations were determined by a high-performance liquid chromatography tandem mass-spectrometry. Continuous variables were described as means and standard error (SE) if normally distributed and as median and interquartile range (IQR) if not. Univariate comparisons were performed using analysis of variance, *Corresponding author: Felicia Stefania Falvella, BiolSciD Geneticist, Department of Biomedical and Clinical Sciences L. Sacco, “Luigi Sacco” University Hospital, Università di Milano, Via Giovanni Battista Grassi 74, 20157 Milan, Italy, E-mail: stefania.falvella@asst-fbf-sacco.it Elena Ricci, Chiara Resnati, Cristina Gervasoni, Massimo Galli and Agostino Riva: Infectious Diseases Unit, Department of Biomedical and Clinical Sciences L. Sacco, “Luigi Sacco” University Hospital, Università di Milano, Milan, Italy Stefania Cheli, Valeria Cozzi and Dario Cattaneo: Unit of Clinical Pharmacology, Department of Biomedical and Clinical Sciences L. Sacco, “Luigi Sacco” University Hospital, Università di Milano, Milan, Italy Emilio Clementi: Scientific Institute IRCCS Eugenio Medea, Bosisio Parini, Lecco, Italy; and Unit of Clinical Pharmacology, CNR Institute of Neuroscience, Department of Biomedical and Clinical Sciences L. Sacco, “Luigi Sacco” University Hospital, Università di Milano, Milan, Italy

Suspected pharmacokinetic interaction between raltegravir and the 3D regimen of ombitasvir, dasabuvir and paritaprevir/ritonavir in an HIV-HCV liver transplant recipient

After the introduction of the highly active antiretroviral therapy (HAART), human immunodeficiency virus (HIV) infection is no longer considered an absolute contraindication for solid organ transplantation in patients with end-stage liver disease [1–3]. However, recurrence of hepatitis C virus (HCV) infection after liver transplantation is frequent and may lead to allograft loss [4, 5]. Thus, safe and effective treatment of HCV in the post-transplant setting is a mandatory task that needs to be addressed properly. The combination of ombitasvir, dasabuvir and paritaprevir/ritonavir (referred as 3D regimen) has been proven to be associated with high sustained virologic response in HIV-HCV co-infected patients [6, 7] and optimal tolerability when co-administered with immunosuppressive drugs in healthy volunteers [8]. Theoretically, 3D regimen has also a limited propensity to interact with raltegravir (RAL) that is usually given to HIV-infected patients undergoing solid organ transplantation to limit drugto-drug interactions between HAART and immunosuppressive agents [9, 10]. A 57-year-old HIV-infected patient received orthotopic liver transplantation in 2008 for HCV and hepatocellular carcinoma. Post-transplant, he had recurrence of chronic infection with the HCV genotype 1a. He was on maintenance HAART with abacavir, lamivudine and RAL since 2008 with an optimal virologic response (HIV RNA <37 cp/mL) and CD4 count of 272 cells/μL. Long-term immunosuppressive regimen was of 50mg cyclosporine monotherapy twice daily with trough concentrations ranging from 80 to 140 ng/mL. On July 2014, 3D treatment was started. His Child-Pugh class was B with a score of 8 with minimal alterations in serum transaminases (aspartate aminotransferase 93 IU/mL, alanine aminotransferase 38 IU/mL) and with surveillance abdominal imaging negative for the recurrence of hepatocellular carcinoma. In agreement with the available literature [8], the dose of cyclosporine was initially reduced to 20 mg qd and subsequently increased up to 30 mg bid on the basis of trough drug concentrations. Therapeutic drug monitoring (TDM) of RAL plasma concentrations, performed by the collection of blood samples immediately before and at 1, 2, 3 and 4 h after the morning drug dose, was carried out before, during and at the end of 3D treatment (two assessments for each time period). RAL area under curve over 12 h (AUC0–12) was estimated using a previously validated algorithm [11]. As shown in Fig. 1, a dramatic increase in the RAL AUC0–12 was observed during co-administration of the 3D regimen (from 8.68±4.48 to 31.72±0.45 μgxh/mL; +265 %). No other drugs known to potentially interfere with RAL pharmacokinetics were given during the 3D treatment period. The patient did not experience alterations in serum transaminases or creatine phosphokinase levels and was able to complete the 6-month scheduled 3D therapy. At the conclusion of the antiviral treatment, the patient exhibited sustained viral clearance with tests negative for HCV RNA at week 12 post-therapy. * Cristina Gervasoni cristina.gervasoni@unimi.it

Elvitegravir/cobicistat-associated toxic optical neuropathy in an HIV-infected patient: a call for caution?

Ocular toxicity may not only be caused by medication overdoses and drug-drug interactions, but also by chronic administration of medications at recommended doses. We describe a case of an HIV-infected patient who experienced significant and sustained bilateral visual loss 2 months after starting treatment with elvitegravir/cobicistat/tenofovir/emtricitabine. Given the absence of any evidence of tenofovir- or emtricitabine-induced optical neuropathy after several years of clinical use, the antiretroviral therapy was promptly changed to tenofovir/emtricitabine plus atazanavir/ritonavir, which led to a progressive improvement in visual acuity. However, visual evoked potentials never returned to normal amplitudes. This is the first report of toxic optical neuropathy associated with the use of elvitegravir/cobicistat. It is imperative to recognize any signs of possible eye toxicity as rapidly as possible, and refer affected patients to an ophthalmologist promptly because early detection and the withdrawal of the offending agent are crucial in reversing this adverse ocular event.