[WePe3.2C03] CONCENTRATIONS OF ENFUVIRTIDE DO NOT CORRELATE WITH CONCENTRATIONS OF CONCOMITANT PROTEASE INHIBITORS IN HUMAN IMMUNODEFICIENCY VIRUS INFECTED PATIENTS

3rd International AIDS Society Conference on HIV Pathogenesis and Treatment

Rio de Janeiro - July 24 - 27, 2005

CONCENTRATIONS OF ENFUVIRTIDE DO NOT CORRELATE WITH CONCENTRATIONS OF CONCOMITANT PROTEASE INHIBITORS IN HUMAN IMMUNODEFICIENCY VIRUS INFECTED PATIENTS

IAS Conf HIV Pathog Treat 2005 Jul 24-27;3rd: Abstract No. WePe3.2C03

Stocker H.¹, Breske A.², Kruse G.², Schulbin H.¹, Kreckel P.¹, Weber C.¹, Goebel F.³, Roeling J.³, Staszewski S.⁴, Plettenberg A.⁵, Moecklinghoff C.⁶, Arastéh K.¹, Kurowski M.²
¹ Vivantes Auguste-Viktoria Klinikum, KompNet HIV/AIDS, Berlin, Germany, ² HIV-Lab c/o Vivantes Auguste-Viktoria Klinikum, KompNet HIV/AIDS, Berlin, Germany, ³ Ludwig-Maximilians-Universität München, KompNet HIV/AIDS, Munich, Germany, ⁴ HIV Center, J.W. Goethe Universität, Frankfurt am Main, Germany, ⁵ ifi-institute of interdisciplinary infectiology and immunology, Hamburg, Germany, ⁶ Hoffmann-La Roche AG, Grenzach, Germany

INTRODUCTION: ENF concentrations measured in clinical settings are characterised by a high interindividual variability. Surprisingly 14% of patients have ENF trough levels below 1000 ng/ml (suggested cut-off for antiviral efficacy). These findings contrast the results of PK trials and are contrary to what would be expected from an injectable drug which is not metabolised by cytochromes. A number of reasons may account for these findings: So far undefined interactions or conditions like wasting or HIV induced endocrine or cytokine dysregulation may alter ENF pharmacokinetics. Another cause could be the mode of administration which involves the reconstitution, correct storage aspiration and injection of the drug. Overall, adherence is likely to impact drug levels. The objective of this study was to investigate whether complete non adherence, identified by low PI concentrations is responsible for low and highly variable ENF concentrations.

METHODS: Trough levels of ENF and concomitant PI were determined in 56 consecutive patient samples using validated LC-MS/MS methods. ENF and PI concentrations were log-transformed and standardised. [(concentration-mean)/standard deviation] The reference values (means and standard deviations) for each PI regimen were derived from data sets representing the normal population. Standardised ENF and PI concentrations were correlated.

RESULTS: From the 56 12h-samples containing both ENF and PI 90% were from male patients. The median age was 42, the median weight was 67kg. The median CD4 count and virus load were 127/µl and 4,4 log respectively. Co-administered Drugs (n) were LPV: (28), SQV: (21), ATV: (15), APV: (6), IDV: (2) and NFV: (1). 16 Patients received double-PI treatment. ENF trough concentrations ranged from 467ng/ml to 7180ng/ml. PI concentrations showed less variability. There was no correlation between ENF and PI concentrations.

CONCLUSIONS: The lack of correlation between ENF and PI concentrations indicates that complete non adherence involving both enfuvirtide and the concomitant PI is not the cause of low ENF concentrations.

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Clinical | WePe3.2C03 | Hartmut Stocker
Pharmacological Monitoring Of Arv Therapy

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