The Effects of Repeat-Dose Doxorubicin on Cardiovascular Functional Endpoints and Biomarkers in the Telemetry-Equipped Cynomolgus Monkey

Doxorubicin-induced cardiovascular toxicity: a longitudinal evaluation of functional and molecular markers

AIMS

Apart from cardiotoxicity, the chemotherapeutic doxorubicin (DOX) induces vascular toxicity, represented by arterial stiffness and endothelial dysfunction. Both parameters are of interest for cardiovascular risk stratification as they are independent predictors of future cardiovascular events in the general population. However, the time course of DOX-induced cardiovascular toxicity remains unclear. Moreover, current biomarkers for cardiovascular toxicity prove insufficient. Here, we longitudinally evaluated functional and molecular markers of DOX-induced cardiovascular toxicity in a murine model. Molecular markers were further validated in patient plasma.

METHODS AND RESULTS

DOX (4 mg/kg) or saline (vehicle) was administered intra-peritoneally to young, male mice weekly for 6 weeks. In vivo cardiovascular function and ex vivo arterial stiffness and vascular reactivity were evaluated at baseline, during DOX therapy (Weeks 2 and 4) and after therapy cessation (Weeks 6, 9, and 15). Left ventricular ejection fraction (LVEF) declined from Week 4 in the DOX group. DOX increased arterial stiffness in vivo and ex vivo at Week 2, which reverted thereafter. Importantly, DOX-induced arterial stiffness preceded reduced LVEF. Further, DOX impaired endothelium-dependent vasodilation at Weeks 2 and 6, which recovered at Weeks 9 and 15. Conversely, contraction with phenylephrine was consistently higher in the DOX-treated group. Furthermore, proteomic analysis on aortic tissue identified increased thrombospondin-1 (THBS1) and alpha-1-antichymotrypsin (SERPINA3) at Weeks 2 and 6. Up-regulated THBS1 and SERPINA3 persisted during follow-up. Finally, THBS1 and SERPINA3 were quantified in plasma of patients. Cancer survivors with anthracycline-induced cardiotoxicity (AICT; LVEF < 50%) showed elevated THBS1 and SERPINA3 levels compared with age-matched control patients (LVEF ≥ 60%).

CONCLUSIONS

DOX increased arterial stiffness and impaired endothelial function, which both preceded reduced LVEF. Vascular dysfunction restored after DOX therapy cessation, whereas cardiac dysfunction persisted. Further, we identified SERPINA3 and THBS1 as promising biomarkers of DOX-induced cardiovascular toxicity, which were confirmed in AICT patients.

Effect of increase in heart rate after anthracycline chemotherapy on subsequent left ventricular dysfunction

BACKGROUND

Anthracycline chemotherapy-related cardiac dysfunction is believed to be refractory to conventional pharmacological therapy and is associated with a poor prognosis. Increased heart rate (HR) is a known marker of cardiovascular outcomes for various categories of heart failure (HF). However, little interest has been expressed regarding increased HR after anthracycline chemotherapy. Aim of this study was to investigate the effect of increased HR soon after completion of anthracycline chemotherapy on subsequent left ventricular (LV) ejection fraction (LVEF) in cancer patients.

METHODS

We studied 172 patients with breast cancer and malignant lymphoma with preserved LVEF (≥ 50 %) and sinus rhythm treated with anthracyclines. Electrocardiography was performed before and soon after completion of anthracycline chemotherapy (2.3 months), and echocardiography before and late after completion of anthracycline chemotherapy (10.5 months).

RESULTS

HR significantly increased from 74.2 ± 14.2 bpm to 75.9 ± 13.2 bpm (P = 0.05) soon after completion of anthracycline chemotherapy, while LVEF subsequently significantly decreased from 65.3 ± 5.5 % to 62.4 ± 6.1 % (P < 0.01) late after completion of anthracycline chemotherapy. Patients whose HR increased ≥10 bpm subsequently showed a significantly greater decrease in LVEF than those whose HR increased <10 bpm [-4.9 % (-32.7 % - 10.8 %) vs. -2.2 % (-21.2 % - 12.9 %), p = 0.04]. Multivariable logistic regression analysis showed that an increase in HR soon after completion of anthracycline chemotherapy was independently associated with a subsequent decrease in LVEF (odds ratio: 1.022, 95 % confidential interval; 1.008-1.037, P = 0.002).

CONCLUSIONS

Our findings may have a novel effect on the management of cancer patients scheduled for anthracycline chemotherapy.

Key Characteristics of Cardiovascular Toxicants

BACKGROUND

The concept of chemical agents having properties that confer potential hazard called key characteristics (KCs) was first developed to identify carcinogenic hazards. Identification of KCs of cardiovascular (CV) toxicants could facilitate the systematic assessment of CV hazards and understanding of assay and data gaps associated with current approaches.

OBJECTIVES

We sought to develop a consensus-based synthesis of scientific evidence on the KCs of chemical and nonchemical agents known to cause CV toxicity along with methods to measure them.

METHODS

An expert working group was convened to discuss mechanisms associated with CV toxicity.

RESULTS

The group identified 12 KCs of CV toxicants, defined as exogenous agents that adversely interfere with function of the CV system. The KCs were organized into those primarily affecting cardiac tissue (numbers 1-4 below), the vascular system (5-7), or both (8-12), as follows: 1) impairs regulation of cardiac excitability, 2) impairs cardiac contractility and relaxation, 3) induces cardiomyocyte injury and death, 4) induces proliferation of valve stroma, 5) impacts endothelial and vascular function, 6) alters hemostasis, 7) causes dyslipidemia, 8) impairs mitochondrial function, 9) modifies autonomic nervous system activity, 10) induces oxidative stress, 11) causes inflammation, and 12) alters hormone signaling.

DISCUSSION

These 12 KCs can be used to help identify pharmaceuticals and environmental pollutants as CV toxicants, as well as to better understand the mechanistic underpinnings of their toxicity. For example, evidence exists that fine particulate matter [PM ≤2.5μm in aerodynamic diameter (PM2.5)] air pollution, arsenic, anthracycline drugs, and other exogenous chemicals possess one or more of the described KCs. In conclusion, the KCs could be used to identify potential CV toxicants and to define a set of test methods to evaluate CV toxicity in a more comprehensive and standardized manner than current approaches. https://doi.org/10.1289/EHP9321.

Evaluation of moxifloxacin in canine and non-human primate telemetry assays: Comparison of QTc interval prolongation by timepoint and concentration-QTc analysis

The in vivo correct QT (QTc) assay is used by the pharmaceutical industry to characterize the potential for delayed ventricular repolarization and is a core safety assay mentioned in International Conference on Harmonization (ICH) S7B guideline. The typical telemetry study involves a dose‐response analysis of QTc intervals over time using a crossover (CO) design. This method has proven utility but does not include direct integration of pharmacokinetic (PK) data. An alternative approach has been validated and is used routinely in the clinical setting that pairs pharmacodynamic (PD) responses with PK exposure (e.g., concentration‐QTc (C‐QTc) analysis. The goal of our paper was to compare the QTc sensitivity of two experimental approaches in the conscious dog and non‐human primate (NHP) QTc assays. For timepoint analysis, a conventional design using eight animals (8 × 4 CO) to detect moxifloxacin‐induced QTc prolongation was compared to a PK/PD design in a subset (N = 4) of the same animals. The findings demonstrate that both approaches are equally sensitive in detecting threshold QTc prolongation on the order of 10 ms. Both QTc models demonstrated linearity in the QTc prolongation response to moxifloxacin dose escalation (6 to 46 ms). Further, comparison with human QTc findings with moxifloxacin showed agreement and consistent translation across the three species: C‐QTc slope values were 0.7‐ (dog) and 1.2‐ (NHP) fold of the composite human value. In conclusion, our data show that dog and NHP QTc telemetry with an integrated PK arm (C‐QTc) has the potential to supplement clinical evaluation and improve integrated QTc risk assessment.