Malmaruha Arasaratnam1,2,3, Megan Crumbaker4, Atul Bhatnagar5, Matthew J McKay5, Mark P Molloy6,5, Howard Gurney7,8. 1. Department of Medical Oncology, Gosford Hospital, Sydney, Australia. mal.maruha@gmail.com. 2. Kolling Institute, The University of Sydney, Royal North Shore Hospital, Sydney, Australia. mal.maruha@gmail.com. 3. Gosford Hospital, Holden St, Gosford, NSW, 2250, Australia. mal.maruha@gmail.com. 4. Department of Medical Oncology, The Kinghorn Cancer Centre, Sydney, Australia. 5. Department of Molecular Sciences, Macquarie University, Sydney, Australia. 6. Kolling Institute, The University of Sydney, Royal North Shore Hospital, Sydney, Australia. 7. Department of Medical Oncology, Crown Princess Mary Cancer Centre, Westmead Hospital, Sydney, Australia. 8. Macquarie University Clinic, Macquarie University Hospital, Sydney, Australia.
Abstract
PURPOSE: This study examined the inter- and intra-patient variability in pharmacokinetics of AA and its metabolites abiraterone and Δ(4)-abiraterone (D4A), and potential contributing factors. METHODS: AA administered daily for ≥4 weeks concurrently with androgen deprivation therapy (ADT) for mCRPC were included. Pharmacokinetic evaluation was performed at two consecutive visits at least 4 weeks apart. Plasma samples were collected 24 h after last dose of AA to obtain drug trough level (DTL) of two active metabolites, abiraterone and D4A. RESULTS: 39 plasma samples were obtained from 22 patients, with 17 patients had repeat DTL measurement. Considerable inter-patient variability in DTL was seen, with initial DTL for abiraterone ranging between 1.5 and 25.4 ng/ml (CV 61%) and for D4A between 0.2 and 2.5 ng/ml (CV 61%). Intra-patient variability in DTL for abiraterone varied between 0.85 and 336% and for D4A between 1.14 and 199%. There was no increase in AA exposure with use of dexamethasone (n = 5; DTL 13.9) compared with prednisone (n = 17; DTL 11.0 p = 0.5), dosing in fasted state (n = 13, DTL 12.1) compared to dosing in fed state (n = 9; DTL 11.1, p = 0.8), or chemotherapy-exposed (n = 10; DTL 8.9) compared to chemotherapy naïve (n = 12; DTL 14.0, p = 0.1). CONCLUSIONS: Our cohort demonstrated high inter- and intra-patient variability in both abiraterone and D4A with fixed dosing of AA, with no effect from choice of corticosteroids, prior use of chemotherapy, or dosing in fasting state. Monitoring DTL of AA may be necessary to minimise risk of patients being under-dosed and earlier development of resistance.
PURPOSE: This study examined the inter- and intra-patient variability in pharmacokinetics of AA and its metabolites abiraterone and Δ(4)-abiraterone (D4A), and potential contributing factors. METHODS: AA administered daily for ≥4 weeks concurrently with androgen deprivation therapy (ADT) for mCRPC were included. Pharmacokinetic evaluation was performed at two consecutive visits at least 4 weeks apart. Plasma samples were collected 24 h after last dose of AA to obtain drug trough level (DTL) of two active metabolites, abiraterone and D4A. RESULTS: 39 plasma samples were obtained from 22 patients, with 17 patients had repeat DTL measurement. Considerable inter-patient variability in DTL was seen, with initial DTL for abiraterone ranging between 1.5 and 25.4 ng/ml (CV 61%) and for D4A between 0.2 and 2.5 ng/ml (CV 61%). Intra-patient variability in DTL for abiraterone varied between 0.85 and 336% and for D4A between 1.14 and 199%. There was no increase in AA exposure with use of dexamethasone (n = 5; DTL 13.9) compared with prednisone (n = 17; DTL 11.0 p = 0.5), dosing in fasted state (n = 13, DTL 12.1) compared to dosing in fed state (n = 9; DTL 11.1, p = 0.8), or chemotherapy-exposed (n = 10; DTL 8.9) compared to chemotherapy naïve (n = 12; DTL 14.0, p = 0.1). CONCLUSIONS: Our cohort demonstrated high inter- and intra-patient variability in both abiraterone and D4A with fixed dosing of AA, with no effect from choice of corticosteroids, prior use of chemotherapy, or dosing in fasting state. Monitoring DTL of AA may be necessary to minimise risk of patients being under-dosed and earlier development of resistance.
Entities:
Keywords:
Abiraterone; D4A; Pharmacokinetics; Prostate cancer
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