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
5887 - Factors of importance in procuring tumoroids from colorectal liver metastasis biopsies for precision medicine.
Presenter: Lars Henrik Jensen
Session: Poster Display session 2
Resources:
Abstract
2196 - FUSAFE individual patient data meta-analysis (MA) to assess the performance of dihydropyrimidine dehydrogenase (DPD) gene polymorphisms for predicting grade 4-5 fluoropyrimidine (FP) toxicity
Presenter: Marie-Christine Etienne-Grimaldi
Session: Poster Display session 2
Resources:
Abstract
2859 - Treatments (tx) after progression to first-line FOLFOXIRI + bevacizumab (bev) in metastatic colorectal cancer (mCRC) patients (pts): A pooled analysis of TRIBE and TRIBE-2 studies by GONO.
Presenter: Daniele Rossini
Session: Poster Display session 2
Resources:
Abstract
3888 - Randomized phase III study of sequential treatment with capecitabine or 5-fluorouracil (FP) plus bevacizumab (BEV) followed by the addition with oxaliplatin (OX) versus initial combination with OX+FP+ BEV in the first-line chemotherapy for metastatic colorectal cancer: The C-cubed study
Presenter: Takeshi Nagasaka
Session: Poster Display session 2
Resources:
Abstract
1065 - Early tumour shrinkage (ETS), depth of response (DpR) and associated survival outcomes in patients (pts) with RAS wild type (WT) metastatic colorectal cancer (mCRC) classified according to Köhne prognostic category: retrospective analysis of the panitumumab (Pmab) PRIME study
Presenter: Andrea Sartore-Bianchi
Session: Poster Display session 2
Resources:
Abstract
1702 - Randomized phase II trial of CAPOX with planned oxaliplatin stop-and-go strategy as adjuvant chemotherapy after curative resection of colon cancer (CCOG-1302 study)
Presenter: Hiroyuki Yokoyama
Session: Poster Display session 2
Resources:
Abstract
5104 - A metabolomic recurrence score for risk-stratification of elderly patients (pts) with early colorectal cancer (eCRC)
Presenter: Samantha Di Donato
Session: Poster Display session 2
Resources:
Abstract
5285 - RAS mutant allele fraction in plasma predicts benefit to anti-angiogenic based first line treatment in metastatic colorectal cancer
Presenter: Giulia Martini
Session: Poster Display session 2
Resources:
Abstract
1790 - Impact of prophylactic systemic antibiotics (SA) on outcome of patients (pts) with RAS-wildtype (RAS-wt) metastatic colorectal carcinoma (mCRC) treated with cetuximab-based first-line therapy. Subgroup analysis of the german non-interventional study ERBITAG
Presenter: Stephan Sahm
Session: Poster Display session 2
Resources:
Abstract
3059 - Intraoperative chemotherapy with 5-FU for colorectal cancer patients receiving curative resection (IOCCRC): A randomized, multicenter, prospective, phase III trial
Presenter: Rongxin Zhang
Session: Poster Display session 2
Resources:
Abstract