Vasiliki Thomeas

Identification of a Variant in KDR Associated with Serum VEGFR2 and Pharmacodynamics of Pazopanib

Purpose: VEGF receptor (VEGFR) kinases are important drug targets in oncology that affect function of systemic endothelial cells. To discover genetic markers that affect VEGFR inhibitor pharmacodynamics, we performed a genome-wide association study of serum soluble vascular VEGFR2 concentrations [sVEGFR2], a pharmacodynamic biomarker for VEGFR2 inhibitors. Experimental Design: We conducted a genome-wide association study (GWAS) of [sVEGFR2] in 736 healthy Old Order Amish volunteers. Gene variants identified from the GWAS were genotyped serially in a cohort of 128 patients with advanced solid tumor with baseline [sVEGFR2] measurements, and in 121 patients with renal carcinoma with [sVEGFR2] measured before and during pazopanib therapy. Results: rs34231037 (C482R) in KDR, the gene encoding sVEGFR2 was found to be highly associated with [sVEGFR2], explaining 23% of the variance (P = 2.7 × 10−37). Association of rs34231037 with [sVEGFR2] was replicated in 128 patients with cancer with comparable effect size (P = 0.025). Furthermore, rs34231037 was a significant predictor of changes in [sVEGFR2] in response to pazopanib (P = 0.01). Conclusion: Our findings suggest that genome-wide analysis of phenotypes in healthy populations can expedite identification of candidate pharmacogenetic markers. Genotyping for germline variants in KDR may have clinical utility in identifying patients with cancer with unusual sensitivity to effects of VEGFR2 kinase inhibitors. Clin Cancer Res; 21(2); 365–72. ©2014 AACR.

Tricuspid regurgitation progression and regression in pulmonary arterial hypertension: implications for right ventricular and tricuspid valve apparatus geometry and patients outcome

Aims The aim of this study was to determine the mechanism of tricuspid regurgitation (TR) progression in pulmonary arterial hypertension (PAH) and its effect on survival. Methods and results We studied 88 patients with PAH and functional TR (mean pulmonary artery pressure 49 ± 14 mmHg; 43% idiopathic PAH) who had serial echocardiograms. TR progression (n = 35) was defined as ⩽mild TR on Echo 1 and ≥moderate TR on Echo 2. TR regression (n = 17) was defined as ≥moderate TR on Echo 1 and ⩽mild TR on Echo 2. Stable TR (n = 36) was defined as ⩽mild TR on both echoes. TR progression was associated with an increase in pulmonary artery systolic pressure (PASP, 62 ± 22–92 ± 23 mmHg, P < 0.0001), right ventricular (RV) enlargement, mainly at mid-ventricular level, increased RV sphericity (6.1 ± 1.7–6.9 ± 1.8, P = 0.004), tricuspid annular (TA) dilatation (4.0 ± 0.7–4.6 ± 0.7 cm, P < 0.0001), and increased tricuspid valve (TV) tenting area (2.0 ± 0.7–2.5 ± 1.0 cm2, P = 0.0003). TR regression was associated with a reduction in PASP (84 ± 15–55 ± 18 mmHg, P < 0.0001), reverse RV remodelling with a reduction in RV sphericity (6.3 ± 1.4–5.5 ± 1.0, P = 0.02), and a reduction in TA size (4.1 ± 0.7–3.6 ± 0.7 cm, P = 0.02) and TV tenting (2.1 ± 0.7–1.3 ± 0.5 cm2, P = 0.0002). TR progression was associated with all-cause mortality (log-rank P = 0.0007). Conclusion In PAH, TR progression was associated with worsening pulmonary hypertension and adverse RV and TV apparatus remodelling. TR progression is associated with poor outcome in PAH.

Sorafenib dose escalation is not uniformly associated with blood pressure elevations in normotensive patients with advanced malignancies.

Hypertension after treatment with vascular endothelial growth factor (VEGF) receptor inhibitors is associated with superior treatment outcomes for advanced cancer patients. To determine whether increased sorafenib doses cause incremental increases in blood pressure (BP), we measured 12‐h ambulatory BP in 41 normotensive advanced solid tumor patients in a randomized dose‐escalation study. After 7 days’ treatment (400 mg b.i.d.), mean diastolic BP (DBP) increased in both study groups. After dose escalation, group A (400 mg t.i.d.) had marginally significant further increase in 12‐h mean DBP (P = 0.053), but group B (600 mg b.i.d.) did not achieve statistically significant increases (P = 0.25). Within groups, individuals varied in BP response to sorafenib dose escalation, but these differences did not correlate with changes in steady‐state plasma sorafenib concentrations. These findings in normotensive patients suggest BP is a complex pharmacodynamic biomarker of VEGF inhibition. Patients have intrinsic differences in sensitivity to sorafenibs BP‐elevating effects.

Technical considerations in the development of circulating peptides as pharmacodynamic biomarkers for angiogenesis inhibitors

To determine the biological reproducibility and estimate relevant covariates for candidate circulating biomarkers of angiogenesis, we conducted 3 sub‐studies with ≤15 subjects each. In study 1, 6 healthy subjects provided 13 blood samples across 14–24 days. In study 2, 15 advanced solid tumor patients provided single blood samples before, and approximately 8 and 40 days after sorafenib treatment. In study 3, 4 healthy subjects provided blood samples on 3 occasions over 14 days, processed simultaneously in 2 different laboratories at a single institution. Vascular endothelial growth factor (VEGFA), soluble VEGF receptor‐2 (sVEGFR2), and angiopoietin‐2 (Ang2) concentrations in plasma and serum were determined by standard immunoassays. Ang2 and sVEGFR2 demonstrated low variance within and high variance across individuals reflected by the high intraclass correlation coefficient (for Ang2: 0.86 for plasma, 0.89 for serum; for sVEGFR2: 0.91 for plasma, 0.87 for serum). Repeated measures linear modeling from 15 patients demonstrated increased Ang2 (P ≤ 0.05) and decreased sVEGFR2 (P ≤ 0.05) after exposure to sorafenib. VEGFA had high intraindividual variance, and study 3 demonstrated the laboratory to have significant effects on plasma measurements (P ≤ 0.05). The biological reproducibility of sVEGFR2 and Ang2 support further use of these markers in studies of vasculature‐targeted therapeutics.

Phase I safety study of ranolazine in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) causes right ventricular ischemia, dysfunction, and failure. PAH patients may benefit from antianginal agents based on a shared pathophysiology with left ventricular ischemia. A single-center, randomized, placebo-controlled trial (1 : 1) to assess the acute vasoreactivity and safety of ranolazine in PAH was conducted. Plasma samples for pharmacokinetic (PK) studies were drawn during hemodynamic measurements at 0, 60, 90, 120, 240, and 360 minutes from a Swan-Ganz catheter. All patients received 500-mg doses, uptitrated to 1,000 mg at week 4, monthly evaluations, and a complete objective assessment after 12 weeks, followed by an open-label extension. Thirteen patients were randomized and 12 enrolled (6 ranolazine, 6 placebo). All patients completed the acute phase; 10 completed the 12-week study. There were no acute changes in invasive hemodynamics. At 12 weeks ranolazine was well tolerated. Only 1 of the 5 patients on ranolazine had a serum concentration considered to be in the therapeutic range. Two serious adverse events required early withdrawal (both in the ranolazine group); gastrointestinal complaints were the most common adverse event. Efficacy measures did not demonstrate any differences between treatment groups. During the open-label trial, 2 additional patients reached a therapeutic concentration. Ranolazine in PAH appears safe, without acute hemodynamic effects after a 500-mg dose. Ranolazine administrated to PAH patients receiving background PAH therapies did not consistently reach therapeutic levels. Future studies should first perform PK analysis in PAH patients receiving PAH therapies and explore the safety and tolerability of the higher doses perhaps necessary to achieve therapeutic levels in PAH patients. (Trial registration: Clinicaltrials.gov identifier NCT01757808.)

A Serial NT-proBNP Model to Improve Prognostication in Patients with Pulmonary Arterial Hypertension

Background: Baseline elevation in N-terminal pro-brain natriuretic peptide (NT-proBNP) in pulmonary arterial hypertension (PAH) patients is associated with worse outcomes. Serial measurement of commonly available biomarkers could improve the precision of prognostic estimates and our understanding of PAH pathophysiology. Methods: Included were 103 PAH patients with baseline elevated NT-proBNP prior to the initiation or escalation of therapy with at least two subsequent NT-proBNP measurements. Using patients’ serial measurements, a linear mixed-effects model extrapolated a baseline NT-proBNP (intercept) and evolution (slope). These model-determined values were then used in Cox proportional hazards analysis to determine predictors of survival. Time-dependent area under the curve (AUC) analysis compared survival discrimination of serial versus single measurements of NTproBNP. Results: Subjects were 50 ± 14 years; most had idiopathic PAH, congenital heart disease, or connective tissue disease. Survivors were younger than non-survivors 47 ± 14 versus 55 ± 12 years (p=0.002). A multivariable survival model using invasive and non-invasive covariates found NT-proBNP significantly predicted mortality. Timedependent AUC was significantly greater for modeled (intercept) versus measured NT-proBNP. Conclusions: Prognostic modeling utilizing serial NT-proBNP measurements better predict survival than a single baseline value. This evidence supports the conduct of future studies of serial measurement of NT-proBNP to further clarify its role in the clinical care of PAH patients.