Abstract 2642
Background
About 20% of breast cancer (BC) patients do not attain tamoxifen’s (TAM) active metabolite endoxifen (ENDX) target concentrations when receiving 20 mg TAM once daily (q.d.). Thus, individualised dosing of up to 120 mg TAM q.d. for ENDX target attainment (TA) has been proposed. Combining concentrations and antiestrogenic activities of ENDX and its 3 precursors, the antiestrogenic activity score (AAS) has been developed as alternative TA metric. We aimed to integrate experimental and clinical data from diverse sources in an innovative modelling approach to identify patient groups at risk of treatment failure and to assess whether ENDX- or AAS-guided dosing would be more favourable for TA applying in silico simulation.
Methods
In vitro data from enzyme kinetic experiments, pharmacokinetic (PK) parameters from previous clinical studies and in vivo data from three clinical trials were synthesised into a minimal nonlinear mixed-effects physiologically-based pharmacokinetic (NLME-PBPK) model. Using simulation, lowest doses needed for TA, applying either the ENDX (≥5.97 ng/mL) or the AAS (≥1798) threshold, were investigated in a representative virtual BC population with various CYP2D6 activity scores (AS) and age.
Results
The developed NLME-PBPK model captured individual TAM and 3 metabolite concentration profiles from 406 BC patients well. Bioactivation to ENDX was 4.5-fold higher in CYP2D6 normal (NM) than in poor metabolisers (PM). Patients with low CYP2D6 activity and young age showed highest risks for ENDX non-TA. Among all patients, 76% received the same dose irrespective of the TA metric used. For the remaining 23% with different dose selections, applying the AAS instead of the ENDX target, TA increased in NM and intermediate metabolisers (IM) (+21.7% and +6.9%, respectively), while TA decreased in PM (-11.7%).
Conclusions
Our modelling approach combined pharmacogenetic factors, physiological changes and variability on PK parameters in a quantitative manner and allowed to translate PK information on TAM and its three major metabolites into individualised dosing. While ENDX-guided dosing was preferable for PM in our simulation, AAS-guided dosing was superior for NM and IM.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
L. Klopp-Schulze: Full / Part-time employment: Merck Healthcare KGaA. S.L. Koolen: Speaker Bureau / Expert testimony, Research grant / Funding (institution): Novartis; Speaker Bureau / Expert testimony: Pfizer; Speaker Bureau / Expert testimony: Roche; Research grant / Funding (institution): Astellas; Research grant / Funding (institution): Cristal Therapeutics; Travel / Accommodation / Expenses: Ipsen. R.H.J. Mathijssen: Research grant / Funding (institution), Travel / Accommodation / Expenses: Astellas; Research grant / Funding (institution): Bayer; Research grant / Funding (institution): Boehringer; Research grant / Funding (institution): Cristal Therapeutics; Advisory / Consultancy, Research grant / Funding (institution): Novartis; Research grant / Funding (institution): Pamgene; Research grant / Funding (institution): Roche; Research grant / Funding (institution): Sanofi; Research grant / Funding (institution), Travel / Accommodation / Expenses: Pfizer; Advisory / Consultancy: Servier. C. Kloft: Research grant / Funding (institution), Grants received outside the submitted work: DDMoRe; Research grant / Funding (institution), Grants received outside the submitted work: Industry consortium (AbbVie Deutschland GmbH & Co. KG, Boehringer Ingelheim Pharma GmbH & Co. KG, Gruenenthal GmbH, F. Hoffmann-La Roche Ltd., Merck KGaA and SANOFI); Research grant / Funding (institution), Grants received outside the submitted work: Federal Ministry of Education and Research; Research grant / Funding (institution), Grants received outside the submitted work: Diurnal Ltd. All other authors have declared no conflicts of interest.
Resources from the same session
3716 - Prognostic factors for predicting early recurrence within the first year of surgery in pancreatic ductal adenocarcinoma
Presenter: Naru Kim
Session: Poster Display session 2
Resources:
Abstract
3947 - Integrated population pharmacokinetic modelling of liposomal irinotecan in patients with various tumour types, including untreated metastatic pancreatic cancer (mPC)
Presenter: Teresa Macarulla
Session: Poster Display session 2
Resources:
Abstract
2880 - Expression of long noncoding RNA and clinical outcomes of pancreatic cancer patients who received adjuvant chemotherapy by S-1 or GEM after curative resection.
Presenter: Mariko Kamiya
Session: Poster Display session 2
Resources:
Abstract
5029 - POLO: Time to treatment discontinuation and subsequent therapies following maintenance olaparib for patients (pts) with a germline BRCA mutation and metastatic pancreatic cancer (mPC)
Presenter: Eric Van Cutsem
Session: Poster Display session 2
Resources:
Abstract
4730 - Diagnostic Value of Digital Multiplexed Detection of Single Nucleotide Variants in Pancreatic Cancer Specimens Collected by Endoscopic Ultrasound Fine-Needle Aspiration
Presenter: Irina Cazacu
Session: Poster Display session 2
Resources:
Abstract
3303 - Phase I/II study of LDE225 in combination with gemcitabine and nab-paclitaxel in patients with metastatic pancreatic cancer
Presenter: Esther Pijnappel
Session: Poster Display session 2
Resources:
Abstract
2009 - Efficacy of platinum-containing chemotherapy and prognosis of pancreatic cancer patients with homologous recombination deficiency: meta-analysis of published clinical studies
Presenter: Elizeveta Polyanskaya
Session: Poster Display session 2
Resources:
Abstract
2164 - Plasmatic CXCL8 is a marker for TGFß-activated kinase 1 (TAK1) activation which may predict resistance to nanoliposomal irinotecan (nal-IRI) in gemcitabine-refractory pancreatic cancer (PC) patients
Presenter: Valeria Merz
Session: Poster Display session 2
Resources:
Abstract
2529 - A protein level signature of four selected genes associated with survival outcomes of patients with pancreatic ductal adenocarcinoma
Presenter: Jie Hua
Session: Poster Display session 2
Resources:
Abstract
4947 - Pre-treatment serum 25-hydroxyvitamin D levels and survival in a Danish cohort of patients with pancreatic cancer
Presenter: Louise Rasmussen
Session: Poster Display session 2
Resources:
Abstract