Variable Penetrance and Expressivity of a Rare Pore Loss-of-Function Mutation (p.L889V) of Nav1.5 Channels in Three Spanish Families

A novel rare mutation in the pore region of Nav1.5 channels (p.L889V) has been found in three unrelated Spanish families that produces quite diverse phenotypic manifestations (Brugada syndrome, conduction disease, dilated cardiomyopathy, sinus node dysfunction, etc.) with variable penetrance among families. We clinically characterized the carriers and recorded the Na+ current (INa) generated by p.L889V and native (WT) Nav1.5 channels, alone or in combination, to obtain further insight into the genotypic-phenotypic relationships in patients carrying SCN5A mutations and in the molecular determinants of the Nav1.5 channel function. The variant produced a strong dominant negative effect (DNE) since the peak INa generated by p.L889V channels expressed in Chinese hamster ovary cells, either alone (-69.4 ± 9.0 pA/pF) or in combination with WT (-62.2 ± 14.6 pA/pF), was significantly (n ≥ 17, p < 0.05) reduced compared to that generated by WT channels alone (-199.1 ± 44.1 pA/pF). The mutation shifted the voltage dependence of channel activation and inactivation to depolarized potentials, did not modify the density of the late component of INa, slightly decreased the peak window current, accelerated the recovery from fast and slow inactivation, and slowed the induction kinetics of slow inactivation, decreasing the fraction of channels entering this inactivated state. The membrane expression of p.L889V channels was low, and in silico molecular experiments demonstrated profound alterations in the disposition of the pore region of the mutated channels. Despite the mutation producing a marked DNE and reduction in the INa and being located in a critical domain of the channel, its penetrance and expressivity are quite variable among the carriers. Our results reinforce the argument that the incomplete penetrance and phenotypic variability of SCN5A loss-of-function mutations are the result of a combination of multiple factors, making it difficult to predict their expressivity in the carriers despite the combination of clinical, genetic, and functional studies.

Coexistent HCN4 and GATA5 rare variants and Atrial Fibrillation in a large Spanish Family

BACKGROUND

Familial association of atrial fibrillation (AF) can involve single gene variants related to known arrhythmogenic mechanisms; however, genome-wide association studies often disclose complex genetic variants in familial and non-familial AF, making it difficult to relate to known pathogenetic mechanisms.

METHODS

The finding of 4 siblings with AF led to studying 47 members of a family. Long-term Holter monitoring (298 hours average) ruled out silent AFWhole-exome sequencing was performed and variants shared by the index cases were filtered and prioritized according to current recommendations. HCN4 currents (IHCN4) were recorded in Chinese hamster ovary cells expressing human p.P1163H and/or native Hcn4 channels using the patch-clamp technique and topologically associated domain analysis of GATA5 variant carriers were performed.

RESULTS

The clinical study diagnosed 2 more AF cases. Five family members carried the heterozygous p.P1163H, HCN4 variant, 14 the intronic 20,61040536,G,A GATA5 rare variant, and 9 carried both variants (HCN4+GATA5). Five of the 6 AF cases (onset age ranging 33-70 years) carried both variants and one the GATA5 variant alone. Multivariate analysis showed that the presence of HCN4+GATA5 variants significantly and independently increased AF risk [OR=32.740 (1.812-591.408)] and not age, hypertension or overweight. Functional testing showed that IHcn4 generated by heterozygous p.P1163H were normal. Topologically associating domain analysis suggested that GATA5 could affect the expression of many genes, including those encoding microRNA-1.

CONCLUSION

The coincidence of two rare gene variants was independently associated with AF, but functional studies do not allow the postulation of the arrhythmogenic mechanism(s) involved.

Drug-induced atrial fibrillation. A narrative review of a forgotten adverse effect

Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with an increased morbidity and mortality. There is clinical evidence that an increasing number of cardiovascular and non-cardiovascular drugs, mainly anticancer drugs, can induce AF either in patients with or without pre-existing cardiac disorders, but drug-induced AF (DIAF) has not received the attention that it might deserve. In many cases DIAF is asymptomatic and paroxysmal and patients recover sinus rhythm spontaneously, but sometimes, DIAF persists, and it is necessary to perform a cardioversion. Furthermore, DIAF is not mentioned in clinical guidelines on the treatment of AF. The risk of DIAF increases in elderly and in patients treated with polypharmacy and with risk factors and comorbidities that commonly coexist with AF. This is the case of cancer patients. Under these circumstances ascribing causality of DIAF to a given drug often represents a clinical challenge. We review the incidence, the pathophysiological mechanisms, risk factors, clinical relevance, and treatment of DIAF. Because of the limited information presently available, further research is needed to obtain a deeper insight into DIAF. Meanwhile, it is important that clinicians are aware of the problem that DIAF represents, recognize which drugs may cause DIAF, and consider the possibility that a drug may be responsible for a new-onset AF episode.

Clinical evolution and mortality of critically ill patients with SARS-CoV-2 pneumonia treated with remdesivir in an adult intensive care unit of Paraguay

BACKGROUND

The health crisis due to Covid-19 led to the search for therapeutics that could improve the evolution of the disease. Remdesivir, an antiviral that interferes with viral replication, was one of the first to be used for the treatment of this pathology.

OBJECTIVE

To determine clinical course and mortality of patients with severe SARS-CoV-2 pneumonia treated with remdesivir, in comparison of those who didn't receive the medication.

PATIENTS AND METHODS

Retrospective cohort study, with medical records review of COVID-19 patients, between August 2020 and August 2021. The subjects were divided into two groups, those who received remdesivir before or after admission to intensive care and those who didn't. The primary outcome variable was mortality in intensive care.

RESULTS

Of 214 subjects included, 109 (50,9%) received remdesivir. The median of days for the drug administration was 8 (2-20), IQR: 3. The bivariate analysis prove that the use of remdesivir was related with lower risk of develop Acute Respiratory Distress Syndrome (ARDS) (p = 0,019; OR: 0,521) and lower requirement of mechanical ventilation (p = 0,006; OR:0,450). Additionally, patients treated with remdesivir develop less kidney injury (p = 0,009; OR: 0,441). There was a total of 82 deaths, 29 (26,6%) in the remdesivir group and 53 (50,5%) in the control group [p < 0,001; OR: 0,356 (0,201-0,630)]. All the risk factors associated with mortality in the bivariate analysis were entered into the multivariate analysis by logistic regression, the use of remdesivir remained associated as an independent protective factor to mortality (p = 0.034; OR: 0.429).

CONCLUSION

Critically ill patients with SARS-CoV-2 pneumonia treated with remdesivir had a lower risk of death and need for mechanical ventilation and develop less ARDS as compared to the control group. No differences were found in the presentation of adverse effects.

A gain-of-function HCN4 mutant in the HCN domain is responsible for inappropriate sinus tachycardia in a Spanish family

In a family with inappropriate sinus tachycardia (IST), we identified a mutation (p.V240M) of the hyperpolarization-activated cyclic nucleotide-gated type 4 (HCN4) channel, which contributes to the pacemaker current (If) in human sinoatrial node cells. Here, we clinically study fifteen family members and functionally analyze the p.V240M variant. Macroscopic (IHCN4) and single-channel currents were recorded using patch-clamp in cells expressing human native (WT) and/or p.V240M HCN4 channels. All p.V240M mutation carriers exhibited IST that was accompanied by cardiomyopathy in adults. IHCN4 generated by p.V240M channels either alone or in combination with WT was significantly greater than that generated by WT channels alone. The variant, which lies in the N-terminal HCN domain, increased the single-channel conductance and opening frequency and probability of HCN4 channels. Conversely, it did not modify the channel sensitivity for cAMP and ivabradine or the level of expression at the membrane. Treatment with ivabradine based on functional data reversed the IST and the cardiomyopathy of the carriers. In computer simulations, the p.V240M gain-of-function variant increases If and beating rate and thus explains the IST of the carriers. The results demonstrate the importance of the unique HCN domain in HCN4, which stabilizes the channels in the closed state.

Sex and gender differences in the treatment of arterial hypertension

INTRODUCTION

Arterial hypertension represents the leading modifiable risk factor for all-cause death and early development of cardiovascular disease in women. Current clinical guidelines for the treatment of hypertension noted that women respond to antihypertensive drugs similarly to men and, therefore, treatment recommendations remain the same for both sexes. However, clinical evidence suggests the existence of sex- and gender-related differences (SGRD) in the prevalence, pathophysiology, pharmacodynamics (efficacy and safety) and pharmacokinetics of antihypertensive drugs.

AREAS COVERED

This review summarizes SGRD in the prevalence of hypertension, hypertension-mediated organ damage and blood pressure control, prescription patterns, and pharmacokinetics/ pharmacodynamics and doses of antihypertensive drugs.

EXPERT OPINION

There is limited information on SGRD in antihypertensive drug efficacy because of the underrepresentation of women in randomized clinical trials and, more important, because few trials reported results stratified by sex or performed sex-specific analyses. However, there are SGRD in hypertension-mediated organ damage, drug pharmacokinetics and, particularly, in drug safety. Prospective trials specifically designed to better understand the basis for SGRD in the pathophysiology of hypertension and in the efficacy and safety of antihypertensive drugs are needed to achieve a more personalized treatment of hypertension and hypertension-mediated organ damage in women.

Coronary artery properties in atherosclerosis: A deep learning predictive model

In this work an Artificial Neural Network (ANN) was developed to help in the diagnosis of plaque vulnerability by predicting the Young modulus of the core (E _core ) and the plaque (E _plaque ) of atherosclerotic coronary arteries. A representative in silico database was constructed to train the ANN using Finite Element simulations covering the ranges of mechanical properties present in the bibliography. A statistical analysis to pre-process the data and determine the most influential variables was performed to select the inputs of the ANN. The ANN was based on Multilayer Perceptron architecture and trained using the developed database, resulting in a Mean Squared Error (MSE) in the loss function under 10^-7, enabling accurate predictions on the test dataset for E _core and E _plaque . Finally, the ANN was applied to estimate the mechanical properties of 10,000 realistic plaques, resulting in relative errors lower than 3%.

Pembrolizumab in combination with gemcitabine for patients with HER2-negative advanced breast cancer: GEICAM/2015-04 (PANGEA-Breast) study

BACKGROUND

We evaluated a new chemoimmunotherapy combination based on the anti-PD1 monoclonal antibody pembrolizumab and the pyrimidine antimetabolite gemcitabine in HER2- advanced breast cancer (ABC) patients previously treated in the advanced setting, in order to explore a potential synergism that could eventually obtain long term benefit in these patients.

METHODS

HER2-negative ABC patients received 21-day cycles of pembrolizumab 200 mg (day 1) and gemcitabine (days 1 and 8). A run-in-phase (6 + 6 design) was planned with two dose levels (DL) of gemcitabine (1,250 mg/m² [DL0]; 1,000 mg/m² [DL1]) to determine the recommended phase II dose (RP2D). The primary objective was objective response rate (ORR). Tumor infiltrating lymphocytes (TILs) density and PD-L1 expression in tumors and myeloid-derived suppressor cells (MDSCs) levels in peripheral blood were analyzed.

RESULTS

Fourteen patients were treated with DL0, resulting in RP2D. Thirty-six patients were evaluated during the first stage of Simon's design. Recruitment was stopped as statistical assumptions were not met. The median age was 52; 21 (58%) patients had triple-negative disease, 28 (78%) visceral involvement, and 27 (75%) ≥ 2 metastatic locations. Progression disease was observed in 29 patients. ORR was 15% (95% CI, 5-32). Eight patients were treated ≥ 6 months before progression. Fourteen patients reported grade ≥ 3 treatment-related adverse events. Due to the small sample size, we did not find any clear association between immune tumor biomarkers and treatment efficacy that could identify a subgroup with higher probability of response or better survival. However, patients that experienced a clinical benefit showed decreased MDSCs levels in peripheral blood along the treatment.

CONCLUSION

Pembrolizumab 200 mg and gemcitabine 1,250 mg/m² were considered as RP2D. The objective of ORR was not met; however, 22% patients were on treatment for ≥ 6 months. ABC patients that could benefit of chemoimmunotherapy strategies must be carefully selected by robust and validated biomarkers. In our heavily pretreated population, TILs, PD-L1 expression and MDSCs levels could not identify a subgroup of patients for whom the combination of gemcitabine and pembrolizumab would induce long term benefit.

TRIAL REGISTRATION

ClinicalTrials.gov and EudraCT (NCT03025880 and 2016-001,779-54, respectively). Registration dates: 20/01/2017 and 18/11/2016, respectively.

Empagliflozin and Dapagliflozin Increase Na+ and Inward Rectifier K+ Current Densities in Human Cardiomyocytes Derived from Induced Pluripotent Stem Cells (hiPSC-CMs)

Dapagliflozin (dapa) and empagliflozin (empa) are sodium-glucose cotransporter-2 inhibitors (SGLT2is) that reduce morbidity and mortality in heart failure (HF) patients. Sodium and inward rectifier K+ currents (INa and IK1), carried by Nav1.5 and Kir2.1 channels, respectively, are responsible for cardiac excitability, conduction velocity, and refractoriness. In HF patients, Nav1.5 and Kir2.1 expression are reduced, enhancing risk of arrhythmia. Incubation with dapa or empa (24-h,1 µM) significantly increased INa and IK1 densities recorded in human-induced pluripotent stem cell-cardiomyocytes (hiPSC-CMs) using patch-clamp techniques. Dapa and empa, respectively, shifted to more hyperpolarized potentials the INa activation and inactivation curves. Identical effects were observed in Chinese hamster ovary (CHO) cells that were incubated with dapa or empa and transiently expressed human Nav1.5 channels. Conversely, empa but not dapa significantly increased human Kir2.1 currents in CHO cells. Dapa and empa effects on INa and IK1 were also apparent in Ca-calmodulin kinase II-silenced CHO cells. Cariporide, a Na+/H+ exchanger type 1 (NHE1) inhibitor, did not increase INa or IK1 in hiPSC-CMs. Dapa and empa at therapeutic concentrations increased INa and IK1 in healthy human cardiomyocytes. These SGLT2is could represent a new class of drugs with a novel and long-pursued antiarrhythmic mechanism of action.

A Cantú syndrome mutation produces dual effects on KATP channels by disrupting ankyrin B regulation

ATP-sensitive potassium (KATP) channels composed of Kir6.x and sulfonylurea receptor (SURs) subunits couple cellular metabolism to electrical activity. Cantú syndrome (CS) is a rare disease caused by mutations in the genes encoding Kir6.1 (KCNJ8) and SUR2A (ABCC9) that produce KATP channel hyperactivity due to a reduced channel block by physiological ATP concentrations. We functionally characterized the p.S1054Y SUR2A mutation identified in two CS carriers, who exhibited a mild phenotype although the mutation was predicted as highly pathogenic. We recorded macroscopic and single-channel currents in CHO and HEK-293 cells and measured the membrane expression of the channel subunits by biotinylation assays in HEK-293 cells. The mutation increased basal whole-cell current density and at the single-channel level, it augmented opening frequency, slope conductance, and open probability (Po), and promoted the appearance of multiple conductance levels. p.S1054Y also reduced Kir6.2 and SUR2A expression specifically at the membrane. Overexpression of ankyrin B (AnkB) prevented these gain- and loss-of-function effects, as well as the p.S1054Y-induced reduction of ATP inhibition of currents measured in inside-out macropatches. Yeast two-hybrid assays suggested that SUR2A WT and AnkB interact, while p.S1054Y interaction with AnkB is decreased. The p.E322K Kir6.2 mutation, which prevents AnkB binding to Kir6.2, produced similar biophysical alterations than p.S1054Y. Our results are the first demonstration of a CS mutation whose functional consequences involve the disruption of AnkB effects on KATP channels providing a novel mechanism by which CS mutations can reduce ATP block. Furthermore, they may help explain the mild phenotype associated with this mutation.

Empagliflozin and dapagliflozin increase Na current in human cardiomyocytes

Background

Empagliflozin (EMPA) and dapagliflozin (DAPA) are sodium-glucose cotransporter 2 inhibitors (SGLT2i) used for the treatment of type 2 Diabetes Mellitus (T2DM). Both drugs reduce morbidity and mortality in heart failure (HF) patients with reduced or preserved ejection fraction, even in the absence of T2DM. Moreover, these drugs decrease ventricular arrhythmias and sudden cardiac death in HF patients. The sodium current (INa), carried by Nav1.5 channels, is responsible for cardiac action potential (AP) depolarization and determines excitability and conduction velocity. In HF patients, the expression of Nav1.5 channels is reduced, leading to a decrease of ventricular excitability that enhances the arrhythmic risk.

Purpose

We aimed to determine the effects of EMPA and DAPA on human cardiac INa and AP characteristics.

Methods

Peak INa and ventricular-like APs were recorded in cardiomyocytes derived from human induced pluripotent stem cells (hiPSC-CM) using patch-clamp techniques. INa was also recorded in CHO cells transiently transfected with human Nav1.5+Navβ1 channels. In all cases, EMPA or DAPA (1 μM) were added to culture media and incubated for 24-h.

Results

APs recorded in hiPSC-CMs exhibited automatic activity and incubation with EMPA or DAPA did not modify spontaneous beating frequency (0.39±0.04 Hz; P&gt;0.05, n≥16). In cells driven at 1 Hz, none of the drugs modified resting membrane potential (−76.7±1.4 mV; P&gt;0.05, n≥11), but significantly increased AP amplitude from 98.6±3.6 to 105±2.2 (DAPA) and 107±2.3 mV (EMPA) (P&lt;0.05). Interestingly, only EMPA lengthened AP duration measured at 20%, 50%, and 90% (from 605.6±31.3 to 760.5±59.0 ms, P&lt;0.05) of repolarization. In hiPSC-CMs EMPA increased maximum INa density by 64% (from −156.0±28.0 to −256.4±28.1 pA/pF, P&lt;0.05, n≥7) and shifted the midpoint (Vh) of the inactivation curve to more hyperpolarized potentials (from −97.3±4.5 to −108.6±4.4 mV, P&lt;0.05, n≥7). In turn, DAPA increased maximum INa density by 24% (to −193.8±26.6 pA/pF) and shifted the Vh of the activation curve to more negative potentials (from −47.2±1.6 mV to −55.5±2.8 mV, P&lt;0.05), an effect that would increase the INa at negative potentials coinciding with channel opening. None of the drugs modified the time course of current activation or inactivation. In CHO cells, EMPA and DAPA effects on INa were identical to those observed on hiPSC-CM. These results suggest that both SGLT2i increase INa by enhancing Nav1.5 expression into the cell membrane, by a direct gating effect on the channel, or by a combination of both.

Conclusions

In human cardiomyocytes, EMPA and DAPA increase INa and the AP amplitude. Moreover, EMPA, but not DAPA, prolonged AP duration. We propose that EMPA and DAPA exhibit a unique mechanism that increases cardiac excitability and conduction velocity and could contribute to the prevention of arrhythmic events in HF patients.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ministerio de Ciencia e innovaciόnInstituto de de Salud Carlos III

Hypertrophic cardiomyopathy: an up-to-date snapshot of the clinical drug development pipeline

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is a complex cardiac disease with highly variable phenotypic expression and clinical course most often caused by sarcomeric gene mutations resulting in left ventricular hypertrophy, fibrosis, hypercontractility, and diastolic dysfunction. For almost 60 years, HCM has remained an orphan disease and still lacks a disease-specific treatment.

AREAS COVERED

This review summarizes recent preclinical and clinical trials with repurposed drugs and new emerging pharmacological and gene-based therapies for the treatment of HCM.

EXPERT OPINION

The off-label drugs routinely used alleviate symptoms but do not target the core pathophysiology of HCM or prevent or revert the phenotype. Recent advances in the genetics and pathophysiology of HCM led to the development of cardiac myosin adenosine triphosphatase inhibitors specifically directed to counteract the hypercontractility associated with HCM-causing mutations. Mavacamten, the first drug specifically developed for HCM successfully tested in a phase 3 trial, represents the major advance for the treatment of HCM. This opens new horizons for the development of novel drugs targeting HCM molecular substrates which hopefully modify the natural history of the disease. The role of current drugs in development and genetic-based approaches for the treatment of HCM are also discussed.

Regulation of cardiac ion channels by transcription factors: Looking for new opportunities of druggable targets for the treatment of arrhythmias

Cardiac electrical activity is governed by different ion channels that generate action potentials. Acquired or inherited abnormalities in the expression and/or function of ion channels usually result in electrophysiological changes that can cause cardiac arrhythmias. Transcription factors (TFs) control gene transcription by binding to specific DNA sequences adjacent to target genes. Linkage analysis, candidate-gene screening within families, and genome-wide association studies have linked rare and common genetic variants in the genes encoding TFs with genetically-determined cardiac arrhythmias. Besides its critical role in cardiac development, recent data demonstrated that they control cardiac electrical activity through the direct regulation of the expression and function of cardiac ion channels in adult hearts. This narrative review summarizes some studies showing functional data on regulation of the main human atrial and ventricular Na⁺, Ca²⁺, and K⁺ channels by cardiac TFs such as Pitx2c, Tbx20, Tbx5, Zfhx3, among others. The results have improved our understanding of the mechanisms regulating cardiac electrical activity and may open new avenues for therapeutic interventions in cardiac acquired or inherited arrhythmias through the identification of TFs as potential drug targets. Even though TFs have for a long time been considered as 'undruggable' targets, advances in structural biology have led to the identification of unique pockets in TFs amenable to be targeted with small-molecule drugs or peptides that are emerging as novel therapeutic drugs.

Cancer Chemotherapy-Induced Sinus Bradycardia: A Narrative Review of a Forgotten Adverse Effect of Cardiotoxicity

Cardiotoxicity is a common adverse effect of anticancer drugs (ACDs), including the so-called targeted drugs, and increases morbidity and mortality in patients with cancer. Attention has focused mainly on ACD-induced heart failure, myocardial ischemia, hypertension, thromboembolism, QT prolongation, and tachyarrhythmias. Yet, although an increasing number of ACDs can produce sinus bradycardia (SB), this proarrhythmic effect remains an underappreciated complication, probably because of its low incidence and severity since most patients are asymptomatic. However, SB merits our interest because its incidence increases with the aging of the population and cancer is an age-related disease and because SB represents a risk factor for QT prolongation. Indeed, several ACDs that produce SB also prolong the QT interval. We reviewed published reports on ACD-induced SB from January 1971 to November 2020 using the PubMed and EMBASE databases. Published reports from clinical trials, case reports, and recent reviews were considered. This review describes the associations between ACDs and SB, their clinical relevance, risk factors, and possible mechanisms of onset and treatment.

Zfhx3 Transcription Factor Represses the Expression of SCN5A Gene and Decreases Sodium Current Density (INa)

The ZFHX3 and SCN5A genes encode the zinc finger homeobox 3 (Zfhx3) transcription factor (TF) and the human cardiac Na⁺ channel (Nav1.5), respectively. The effects of Zfhx3 on the expression of the Nav1.5 channel, and in cardiac excitability, are currently unknown. Additionally, we identified three Zfhx3 variants in probands diagnosed with familial atrial fibrillation (p.M1260T) and Brugada Syndrome (p.V949I and p.Q2564R). Here, we analyzed the effects of native (WT) and mutated Zfhx3 on Na⁺ current (I_Na) recorded in HL-1 cardiomyocytes. ZFHX3 mRNA can be detected in human atrial and ventricular samples. In HL-1 cardiomyocytes, transfection of Zfhx3 strongly reduced peak I_Na density, while the silencing of endogenous expression augmented it (from −65.9 ± 8.9 to −104.6 ± 10.8 pA/pF; n ≥ 8, p < 0.05). Zfhx3 significantly reduced the transcriptional activity of human SCN5A, PITX2, TBX5, and NKX25 minimal promoters. Consequently, the mRNA and/or protein expression levels of Nav1.5 and Tbx5 were diminished (n ≥ 6, p < 0.05). Zfhx3 also increased the expression of Nedd4-2 ubiquitin-protein ligase, enhancing Nav1.5 proteasomal degradation. p.V949I, p.M1260T, and p.Q2564R Zfhx3 produced similar effects on I_Na density and time- and voltage-dependent properties in WT. WT Zfhx3 inhibits I_Na as a result of a direct repressor effect on the SCN5A promoter, the modulation of Tbx5 increasing on the I_Na, and the increased expression of Nedd4-2. We propose that this TF participates in the control of cardiac excitability in human adult cardiac tissue.

Sex-related differences in the pharmacological treatment of heart failure

Heart failure (HF) represents a leading cause of morbidity and mortality. However, HF trials highlighted many differences between men and women with HF. Thus, women represent approximately a quarter of people with HF with reduced ejection fraction (HFrEF), while they account for over half of those with HF with preserved EF (HFpEF). There are also sex-related differences (SRDs) in the pharmacokinetics, pharmacodynamics and safety profile of some guideline-recommended drugs for the treatment of HF. As compared with men, women with HFrEF are less often treated with guideline-recommended HF drugs, experience more frequent and severe adverse reactions when these drugs are prescribed at the same doses in both sexes, and recent evidence suggests that women might need lower doses than men, bringing into question which are the optimal doses of HF drugs in women and men separately. However, information on SRDs in drug efficacy and safety in patients with HFrEF is very limited due to the underrepresentation of women and the lack of sex-specific evaluations of drug efficacy and safety in HF clinical trials. As a consequence, current clinical guidelines do not provide sex-specific recommendations, even when significant differences exist, at least, in drug safety. The aim of this article is to review the SRDs in the pharmacokinetics, efficacy and safety of guideline-recommended HF drugs and to identify emerging areas of research to improve our understanding of the SRDs, because a better understanding of these differences is the first step to achieve a personalized treatment of HF in women and men.

The pharmacotherapeutic management of hyperkalemia in patients with cardiovascular disease

Introduction: Patients with cardiovascular diseases (CVD) are at increased risk of hyperkalemia, particularly when treated with renin-angiotensin-aldosterone inhibitors (RAASIs). Because the occurrence or fear of hyperkalemia, RAASIs are frequently down-titrated or discontinued in patients with CVD, with consequent worse outcomes than patients who remain on maximum doses.Areas covered: This article reviews potassium homeostasis, epidemiology, risk factors, and outcomes of hyperkalemia, and efficacy and safety of the drugs used for acute and chronic treatment of hyperkalemia. A literature search was carried out using the PubMed and guidelines for the management of hyperkalemia.Expert opinion: The emergency treatment of hyperkalemia is not supported by high-quality evidence and clinical trials did not report drug effects on clinical outcomes. Two potassium binders, patiromer and sodium zirconium cyclosilicate, represent a new approach in the treatment of chronic hyperkalemia as they may allow the titration and maintenance of guidelines-recommended doses of RAASIs in patients with CVD who otherwise would not tolerate them due to the risk of hyperkalemia.Further studies are needed to evaluate the safety and efficacy of drug therapy and support the development of guidelines for acute and chronic hyperkalemia.

Tbx5 variants disrupt Nav1.5 function differently in patients diagnosed with Brugada or Long QT Syndrome

AIMS

The transcription factor Tbx5 controls cardiogenesis and drives Scn5a expression in mice. We have identified two variants in TBX5 encoding p.D111Y and p.F206L Tbx5, respectively, in two unrelated patients with structurally normal hearts diagnosed with Long QT (LQTS) and Brugada (BrS) Syndrome. Here we characterized the consequences of each variant to unravel the underlying disease mechanisms.

METHODS AND RESULTS

We combined clinical analysis with in vivo and in vitro electrophysiological and molecular techniques in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), HL-1 cells, and cardiomyocytes from mice trans-expressing human wildtype (WT) or mutant proteins. Tbx5 increased transcription of SCN5A encoding cardiac Nav1.5 channels, while repressing CAMK2D and SPTBN4 genes encoding Ca-calmodulin kinase IIδ (CaMKIIδ) and βIV-spectrin, respectively. These effects significantly increased Na current (INa) in hiPSC-CMs and in cardiomyocytes from mice trans-expressing Tbx5. Consequently, action potential (AP) amplitudes increased and QRS interval narrowed in the mouse electrocardiogram. p.F206L Tbx5 bound to the SCN5A promoter failed to transactivate it, thus precluding the pro-transcriptional effect of WT Tbx5. Therefore, p.F206L markedly decreased INa in hiPSC-CM, HL-1 cells, and mouse cardiomyocytes. The INa decrease in p.F206L trans-expressing mice translated into QRS widening and increased flecainide sensitivity. p.D111Y Tbx5 increased SCN5A expression but failed to repress CAMK2D and SPTBN4. The increased CaMKIIδ and βIV-spectrin significantly augmented the late component of INa (INaL) which, in turn, significantly prolonged AP duration in both hiPSC-CMs and mouse cardiomyocytes. Ranolazine, a selective INaL inhibitor, eliminated the QT and QTc intervals prolongation seen in p.D111Y trans-expressing mice.

CONCLUSIONS

In addition to peak INa, Tbx5 critically regulates INaL and the duration of repolarization in human cardiomyocytes. Our original results suggest that TBX5 variants associate with and modulate the intensity of the electrical phenotype in LQTS and BrS patients.

Palbociclib in combination with endocrine therapy versus capecitabine in hormonal receptor-positive, human epidermal growth factor 2-negative, aromatase inhibitor-resistant metastatic breast cancer: a phase III randomised controlled trial-PEARL

BACKGROUND

Palbociclib plus endocrine therapy (ET) is the standard treatment of hormone receptor-positive and human epidermal growth factor receptor 2-negative, metastatic breast cancer (MBC). However, its efficacy has not been compared with that of chemotherapy in a phase III trial.

PATIENTS AND METHODS

PEARL is a multicentre, phase III randomised study in which patients with aromatase inhibitor (AI)-resistant MBC were included in two consecutive cohorts. In cohort 1, patients were randomised 1 : 1 to palbociclib plus exemestane or capecitabine. On discovering new evidence about estrogen receptor-1 (ESR1) mutations inducing resistance to AIs, the trial was amended to include cohort 2, in which patients were randomised 1 : 1 between palbociclib plus fulvestrant and capecitabine. The stratification criteria were disease site, prior sensitivity to ET, prior chemotherapy for MBC, and country of origin. Co-primary endpoints were progression-free survival (PFS) in cohort 2 and in wild-type ESR1 patients (cohort 1 + cohort 2). ESR1 hotspot mutations were analysed in baseline circulating tumour DNA.

RESULTS

From March 2014 to July 2018, 296 and 305 patients were included in cohort 1 and cohort 2, respectively. Palbociclib plus ET was not superior to capecitabine in both cohort 2 [median PFS: 7.5 versus 10.0 months; adjusted hazard ratio (aHR): 1.13; 95% confidence interval (CI): 0.85-1.50] and wild-type ESR1 patients (median PFS: 8.0 versus 10.6 months; aHR: 1.11; 95% CI: 0.87-1.41). The most frequent grade 3-4 toxicities with palbociclib plus exemestane, palbociclib plus fulvestrant and capecitabine, respectively, were neutropenia (57.4%, 55.7% and 5.5%), hand/foot syndrome (0%, 0% and 23.5%), and diarrhoea (1.3%, 1.3% and 7.6%). Palbociclib plus ET offered better quality of life (aHR for time to deterioration of global health status: 0.67; 95% CI: 0.53-0.85).

CONCLUSIONS

There was no statistical superiority of palbociclib plus ET over capecitabine with respect to PFS in MBC patients resistant to AIs. Palbociclib plus ET showed a better safety profile and improved quality of life.

A rare HCN4 variant with combined sinus bradycardia, left atrial dilatation, and hypertrabeculation/left ventricular noncompaction phenotype

INTRODUCTION AND OBJECTIVES

HCN4 variants have been reported to cause combined sick sinus syndrome (SSS) and left ventricular noncompaction (LVNC) cardiomyopathy. This relationship has been proven in few cases and no previous patients have associated left atrial dilatation (LAD). Our objective was to study a familial disorder characterized by SSS, LAD, and hypertrabeculation/LVNC and to identify the underlying genetic and electrophysiological characteristics.

METHODS

A family with SSS and LVNC underwent a clinical, genetic, and electrophysiological assessment. They were studied via electrocardiography, Holter recording, echocardiography, and exercise stress tests; cardiac magnetic resonance imaging was additionally performed in affected individuals. Genetic testing was undertaken with targeted next-generation sequencing, as well as a functional study of the candidate variant in Chinese hamster ovary cells.

RESULTS

Twelve members of the family had sinus bradycardia, associated with complete criteria of LVNC in 4 members and hypertrabeculation in 6 others, as well as LAD in 9 members. A HCN4 c.1123C>T;(p.R375C) variant was present in heterozygosis in all affected patients and absent in unaffected individuals. Electrophysiological analyses showed that the amplitude and densities of the HCN4 currents (I_HCN4) generated by mutant p.R375C HCN4 channels were significantly lower than those generated by wild-type channels.

CONCLUSIONS

The combined phenotype of SSS, LAD, and LVNC is associated with the heritable HCN4 c.1123C>T;(p.R375C) variant. HCN4 variants should be included in the genetic diagnosis of LVNC cardiomyopathy and of patients with familial forms of SSS, as well as of individuals with sinus bradycardia and LAD.

The p.P888L SAP97 polymorphism increases the transient outward current (Ito,f) and abbreviates the action potential duration and the QT interval

Synapse-Associated Protein 97 (SAP97) is an anchoring protein that in cardiomyocytes targets to the membrane and regulates Na⁺ and K⁺ channels. Here we compared the electrophysiological effects of native (WT) and p.P888L SAP97, a common polymorphism. Currents were recorded in cardiomyocytes from mice trans-expressing human WT or p.P888L SAP97 and in Chinese hamster ovary (CHO)-transfected cells. The duration of the action potentials and the QT interval were significantly shorter in p.P888L-SAP97 than in WT-SAP97 mice. Compared to WT, p.P888L SAP97 significantly increased the charge of the Ca-independent transient outward (I_to,f) current in cardiomyocytes and the charge crossing Kv4.3 channels in CHO cells by slowing Kv4.3 inactivation kinetics. Silencing or inhibiting Ca/calmodulin kinase II (CaMKII) abolished the p.P888L-induced Kv4.3 charge increase, which was also precluded in channels (p.S550A Kv4.3) in which the CaMKII-phosphorylation is prevented. Computational protein-protein docking predicted that p.P888L SAP97 is more likely to form a complex with CaMKII than WT. The Na⁺ current and the current generated by Kv1.5 channels increased similarly in WT-SAP97 and p.P888L-SAP97 cardiomyocytes, while the inward rectifier current increased in WT-SAP97 but not in p.P888L-SAP97 cardiomyocytes. The p.P888L SAP97 polymorphism increases the I_to,f, a CaMKII-dependent effect that may increase the risk of arrhythmias.

Clinical outcome and subchondral bone edema presence at two-year follow-up after high density autologous chondrocyte implantation treatment in the knee

BACKGROUND

Recently, a new approach of autologous chondrocyte implantation technique (using as biomaterial a collagen type i/iii membrane) based on increasing cell density called HD-ACI (High Density Autologous Chondrocyte Implantation) has been described. The objective of this paper was to study the clinical outcome and incidence of subchondral bone oedema in patients with cartilage lesions in the knee treated with HD-ACI at 1-2 years of follow-up.

METHODS

This is a retrospective study performed with forty patients with chondral injuries grade iii-iv. All patients were treated with HD-ACI with a cellular dose of 5×10⁶ chondrocytes /cm² of lesion. The subjective perception of improvement of symptoms and functionality was measured with the IKDC score (International Knee Documentation Committee). The presence of bone oedema was assessed at 6, 12 and 24 months of follow-up by magnetic resonance imaging.

RESULTS

IKDC values showed a significant improvement at 12 and 24 months (P<.001). The mean difference of IKDC between the baseline visit and 12 months was 26.3 points, and 31.6 points at 24 months. Twenty-seven point five percent of the patients presented subchondral bone oedema at 2 years of follow-up.

CONCLUSIONS

HD-ACI is an effective and safe treatment that improves pain, clinical perception and functionality of the joint. No correlation was found between the presence of bone oedema and the patients' clinical outcome.

Pharmacotherapy for hypertension in pregnant patients: special considerations

INTRODUCTION

Hypertensive disorders of pregnancy (HDP) represent a major cause of maternal, fetal and neonatal morbidity and mortality and identifies women at risk for cardiovascular and other chronic diseases later in life. When antihypertensive drugs are used during pregnancy, their benefit and harm to both mother and fetus should be evaluated.

AREAS COVERED

This review summarizes the pharmacological characteristics of the recommended antihypertensive drugs and their impact on mother and fetus when administered during pregnancy and/or post-partum. Drugs were identified using MEDLINE and the main international Guidelines for the management of HDP.

EXPERT OPINION

Although there is a consensus that severe hypertension should be treated, treatment of mild hypertension without end-organ damage (140-159/90-109 mmHg) remains controversial and there is no agreement on when to initiate therapy, blood pressure targets or recommended drugs in the absence of robust evidence for the superiority of one drug over others. Furthermore, the long-term outcomes of in-utero antihypertensive exposure remain uncertain. Therefore, evidence-based data regarding the treatment of HDP is lacking and well designed randomized clinical trials are needed to resolve all these controversial issues related to the management of HDP.

Abstract P5-12-03: Genome copy number entropy as predictor of response for neoadjuvant therapy in early breast cancer

Background

Copy Number Alterations (CNAs) represent changes in the copy number of genomic segments of somatic cells due to chromosomal instability. CNAs include gene amplifications or deletions and can be involved in tumorigenesis. We analyzed CNAs data in pre- and post-treatment (ttm) tumors from patients (pts) with early breast cancer (BC) in the neoadjuvant trials GEICAM/2006-03 and GEICAM/2006-14, with the aim to identify CNAs in particular genomic regions (genetic entropy) associated with treatment response.

Methods

GEICAM/2006-03 (NCT00432172) HER2-negative pts were selectively treated according to clinical subtypes: triple negative (TN) pts were treated with standard anthracycline/taxane -based chemotherapy (AT-CT) +/- carboplatin, while luminal patients were randomized to AT-CT vs. hormonotherapy; GEICAM/2006-14 (NCT00841828) HER2+ pts received AT-CT plus anti-HER2 therapy.Shallow-whole genome Illumina sequencing DNA data from 204 paraffin-embedded tumors (100 pre- and 104 post-ttm) were segmented to obtain CNAs and recurrent altered genomic regions were defined. We used Wilcoxon test to analyze the frequency of altered regions and logistic regression analyses to explore their association with tumor response, in terms of pathological complete response (pCR) in breast and axilla. Validation of altered genes associated with therapy response was performed in the microarray gene expression-based Hatzis dataset (GSE25066) from pts receiving neoadjuvant AT-CT (1).

Results

A total of 672 regions covering the whole genome were identified upon analysis of CNAs data. Regions were categorized according to their alteration status as amplified, normal and lost. Comparative analysis of alterations revealed 11 regions significantly different (p&lt;0.05) in pre- vs post-ttm tumors. Logistic regression analysis showed that in pre-ttm tumors specific alterations of 8 regions localized in 3 different genomic loci (11q12, 16q22 and 21q22) were significantly associated with pCR (p&lt;0.05). Independent analyses of CNAs data with “CGH regions” and “GISTIC2.0” tools confirmed the special relevance of 2 of these 8 regions (#653 and #654), amplified in the locus 21q22.12. This locus contains 20 genes whose expression was tested in Hatzis dataset (1) (GSE25066): the analysis showed that overexpression of 5 of these 20 genes (CHAF1B, CBR1, CBR3, RCAN1 and SLC5A3) turned out to be significantly higher in the cohort of pts who reached pCR, in agreement with our findings. Some of these genes have already been described as proliferation markers (CHAF1B) or involved in treatment response (CBR1) in BC. Other genes related to BC in this genomic region are the transcription factor RUNX1 and the Lysine Methyltransferase SETD4.

Conclusions

According to our results, neoadjuvant therapy can modulate genomic aberrations landscape in BC. Our data suggest that amplification of specific genes in the genomic locus (21q22.12) is involved in the neoadjuvant therapy response in early BC.

(1): Hatzis et al., JAMA 2011, 305(18) 1873-81

Citation Format: Alba E, Rueda OM, Lluch A, Albanell J, Chin S-F, Chacón JI, Calvo L, De la Haba-Rodriguez J, Bermejo B, Ribelles N, Sánchez-Rovira P, Plazaola A, Barnadas A, Cirauqul B, Ramos M, Arcusa A, Carrasco E, Herranz J, Chiesa M, Caballero R, Santonja A, Rojo F, Caldas C. Genome copy number entropy as predictor of response for neoadjuvant therapy in early breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-12-03.

Brugada syndrome trafficking-defective Nav1.5 channels can trap cardiac Kir2.1/2.2 channels

Cardiac Nav1.5 and Kir2.1-2.3 channels generate Na (INa) and inward rectifier K (IK1) currents, respectively. The functional INa and IK1 interplay is reinforced by the positive and reciprocal modulation between Nav15 and Kir2.1/2.2 channels to strengthen the control of ventricular excitability. Loss-of-function mutations in the SCN5A gene, which encodes Nav1.5 channels, underlie several inherited arrhythmogenic syndromes, including Brugada syndrome (BrS). We investigated whether the presence of BrS-associated mutations alters IK1 density concomitantly with INa density. Results obtained using mouse models of SCN5A haploinsufficiency, and the overexpression of native and mutated Nav1.5 channels in expression systems - rat ventricular cardiomyocytes and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) - demonstrated that endoplasmic reticulum (ER) trafficking-defective Nav1.5 channels significantly decreased IK1, since they did not positively modulate Kir2.1/2.2 channels. Moreover, Golgi trafficking-defective Nav1.5 mutants produced a dominant negative effect on Kir2.1/2.2 and thus an additional IK1 reduction. Moreover, ER trafficking-defective Nav1.5 channels can be partially rescued by Kir2.1/2.2 channels through an unconventional secretory route that involves Golgi reassembly stacking proteins (GRASPs). Therefore, cardiac excitability would be greatly affected in subjects harboring Nav1.5 mutations with Golgi trafficking defects, since these mutants can concomitantly trap Kir2.1/2.2 channels, thus unexpectedly decreasing IK1 in addition to INa.

Increasing stomatal conductance in response to rising atmospheric CO2

Background and Aims

Studies have indicated that plant stomatal conductance (gs) decreases in response to elevated atmospheric CO2, a phenomenon of significance for the global hydrological cycle. However, gs increases across certain CO2 ranges have been predicted by optimization models. The aim of this work was to demonstrate that under certain environmental conditions, gs can increase in response to elevated CO2.

Methods

Using (1) an extensive, up-to-date synthesis of gs responses in free air CO2 enrichment (FACE)experiments, (2) in situ measurements across four biomes showing dynamic gs responses to a CO2 rise of ~50 ppm (characterizing the change in this greenhouse gas over the past three decades) and (3) a photosynthesis-stomatal conductance model, it is demonstrated that gs can in some cases increase in response to increasing atmospheric CO2.

Key Results

Field observations are corroborated by an extensive synthesis of gs responses in FACE experiments showing that 11.8 % of gs responses under experimentally elevated CO2 are positive. They are further supported by a strong data-model fit (r2 = 0.607) using a stomatal optimization model applied to the field gs dataset. A parameter space identified in the Farquhar-Ball-Berry photosynthesis-stomatal conductance model confirms field observations of increasing gs under elevated CO2 in hot dry conditions. Contrary to the general assumption, positive gs responses to elevated CO2, although relatively rare, are a feature of woody taxa adapted to warm, low-humidity conditions, and this response is also demonstrated in global simulations using the Community Land Model (CLM4).

Conclusions

The results contradict the over-simplistic notion that global vegetation always responds with decreasing gs to elevated CO2, a finding that has important implications for predicting future vegetation feedbacks on the hydrological cycle at the regional level.

Outcomes of single versus double hormone receptor-positive breast cancer. A GEICAM/9906 sub-study

BACKGROUND

Retrospective data suggest better outcomes for patients with double hormonal receptor (oestrogen [ER] and progesterone receptor [PgR])-positive (dHR+) early breast cancer, compared with single hormonal receptor-positive, sHR+, (ER+/PgR- or ER-/PgR+) disease. Here, we evaluate the classification according to intrinsic subtypes and clinical outcomes of sHR+ versus dHR+ in HER2-negative breast cancer patients enrolled in GEICAM/9906 study (NCT00129922).

METHODS

Archival tumours were retrieved retrospectively for the analysis of ER, PgR and HER2 status and classified into intrinsic subtypes using the PAM50 gene expression assay. Disease-free survival (DFS) and overall survival (OS) were explored using a Cox proportional hazard analysis.

RESULTS

Data on intrinsic subtypes were available in 571 (50%) patients with ER+ and/or PR+, and HER2-negative primary tumours. The incidence of luminal A and luminal B subtypes were 52%/36% in dHR+ tumours (ER+/PgR+), and 15%/58% in ER+/PgR-tumours. ER-/PgR+ tumours were mainly luminal A (52%). Compared with ER+/PgR+ patients, DFS was similar in ER-/PgR+ (hazard ratio [HR] 1.15, 95% confidence interval [CI] 0.57-2.34, p = 0.70) but worse in ER+/PgR- patients (HR 1.60, 95% CI 1.12-2.28, p < 0.01). Similar results were observed for OS (HR 1.50, p = 0.30 and HR 1.86, p < 0.01, respectively).

CONCLUSIONS

The ER+/PgR- group is characterised by higher proliferation and worse outcomes. In spite of the ER-/PgR+ subgroup resembles ER+/PgR+ disease in terms of molecular subtypes and outcomes, the small number of patients in this subgroup prevents from drawing any conclusions.

TRIAL REGISTRATION

EudraCT: 2005-003108-12 (retrospectively registered 28/06/2005). CLINICALTRIALS.

GOV IDENTIFIER

NCT00129922 (retrospectively registered 10/08/2005).

Cardiac Kir2.1 and NaV1.5 Channels Traffic Together to the Sarcolemma to Control Excitability

RATIONALE

In cardiomyocytes, Na_V1.5 and Kir2.1 channels interact dynamically as part of membrane bound macromolecular complexes.

OBJECTIVE

The objective of this study was to test whether Na_V1.5 and Kir2.1 preassemble during early forward trafficking and travel together to common membrane microdomains.

METHODS AND RESULTS

In patch-clamp experiments, coexpression of trafficking-deficient mutants Kir2.1^Δ314-315 or Kir2.1^R44A/R46A with wild-type (WT) Na_V1.5^WT in heterologous cells reduced inward sodium current compared with Na_V1.5^WT alone or coexpressed with Kir2.1^WT. In cell surface biotinylation experiments, expression of Kir2.1^Δ314-315 reduced Na_V1.5 channel surface expression. Glycosylation analysis suggested that Na_V1.5^WT and Kir2.1^WT channels associate early in their biosynthetic pathway, and fluorescence recovery after photobleaching experiments demonstrated that coexpression with Kir2.1 increased cytoplasmic mobility of Na_V1.5^WT, and vice versa, whereas coexpression with Kir2.1^Δ314-315 reduced mobility of both channels. Viral gene transfer of Kir2.1^Δ314-315 in adult rat ventricular myocytes and human induced pluripotent stem cell-derived cardiomyocytes reduced inward rectifier potassium current and inward sodium current, maximum diastolic potential and action potential depolarization rate, and increased action potential duration. On immunostaining, the AP1 (adaptor protein complex 1) colocalized with Na_V1.5^WT and Kir2.1^WT within areas corresponding to t-tubules and intercalated discs. Like Kir2.1^WT, Na_V1.5^WT coimmunoprecipitated with AP1. Site-directed mutagenesis revealed that Na_V1.5^WT channels interact with AP1 through the Na_V1.5^Y1810 residue, suggesting that, like for Kir2.1^WT, AP1 can mark Na_V1.5 channels for incorporation into clathrin-coated vesicles at the trans-Golgi. Silencing the AP1 ϒ-adaptin subunit in human induced pluripotent stem cell-derived cardiomyocytes reduced inward rectifier potassium current, inward sodium current, and maximum diastolic potential and impaired rate-dependent action potential duration adaptation.

CONCLUSIONS

The Na_V1.5-Kir2.1 macromolecular complex pre-assembles early in the forward trafficking pathway. Therefore, disruption of Kir2.1 trafficking in cardiomyocytes affects trafficking of Na_V1.5, which may have important implications in the mechanisms of arrhythmias in inheritable cardiac diseases.

Abstract P5-21-23: Evaluation of the drug interaction potential of palbociclib and exemestane – Results from the PEARL pharmacokinetic sub-Study

Background: Palbociclib (PAL) is an oral cyclin-dependent kinase (CDK) 4/6 inhibitor that is under investigation in multiple oncologic clinical trials and is currently approved for use in combination with aromatase inhibitors (AIs) or fulvestrant (FUL) in patients with hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2–) advanced breast cancer (BC).

The PEARL Study is an ongoing international, open label, controlled, randomized Phase 3 study comparing the efficacy and safety of PAL in combination with endocrine therapy (exemestane [EXE] or FUL) versus capecitabine in postmenopausal women with HR+/ HER2– metastatic BC whose disease progressed on AIs. A secondary objective of the study was to evaluate the pharmacokinetics (PK) of PAL (125mg QD, 3 weeks on/1 week off) and EXE (25mg QD, continuously) when coadministered. This is the first study to investigate the drug-drug interaction (DDI) potential of the combination of PAL and the AI EXE.

Methods: Patients (pts) randomized to the PAL+EXE arm of the PEARL Study in seven selected sites had the option of participating in the PK sub-study. Those who enrolled in the PK sub-study received EXE alone in a 7-day lead-in period immediately prior to Cycle 1 Day 1, when both drugs were coadministered on their standard dosing regimens. Sub-study pts were to have 2 pre-dose plasma PK samples drawn at steady-state (ss) during the lead-in period ("EXE Alone") for EXE determination, and 2 ss PK samples drawn for EXE and PAL determination (2 per analyte) during coadministration ("PAL+EXE"). Plasma concentrations of PAL and EXE were measured using validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. The withinpatient mean concentration of the PK samples which met ss acceptance criteria (WPM-Ctrough) for each analyte were generated for each treatment period as the input for DDI analyses.

To assess the effect of coadministration of PAL on EXE PK, the WPM-Ctrough of EXE was compared within patients between the "PAL+EXE" (Test) and "EXE Alone" (Reference) treatment periods using a one-way analysis of variance (ANOVA) model with treatment as a fixed effect and patient as a random effect. To assess the effect of coadministration of EXE on PAL PK, the WPM-Ctrough of PAL was compared between the "PAL+EXE" period (Test) and historical data (Reference) using an ANOVA model. Analysis of covariance (ANCOVA) models were used to assess the impact of demographic differences between analysis populations in covariates known to impact PAL PK on the ANOVA model conclusions.

Results: A total of 26 pts randomized to the PAL+EXE arm were enrolled in the PK sub-study and had PK samples analysed, of which 23 meet ss acceptance criteria. The ratio of the adjusted geometric means for EXE WPM-Ctrough was 106.9% (90%CI: 82.4-138.8), when EXE was administered with PAL, compared with its administration alone. Likewise, the models to assess potential for EXE to perpetrate DDI on PAL PK showed ratios of adjusted geometric means of 102.4% (90%CI: 82.0-127.9) and 111.6% (90%CI: 90.3137.8), when adjusted for covariates.

Conclusion: The PK data indicate a lack of a clinically meaningful DDI between PAL and EXE when the 2 drugs are coadministered.

Sponsor: GEICAM

Citation Format: Martín M, Hoffman J, Ruiz-Borrego M, Muñoz M, Calvo L, Crownover P, García-Sáenz JA, Alba E, Wang D, Thallinger C, Stradella A, Montaño Á, Adamo B, Antolín S, Moreno-Antón F, Falo C, Ruiz V, Martín N, Caballero R, Carrasco E, Gil-Gil M. Evaluation of the drug interaction potential of palbociclib and exemestane – Results from the PEARL pharmacokinetic sub-Study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-21-23.

Abstract OT1-01-02: A multicenter phase II trial to evaluate the efficacy and safety of pembrolizumab and gemcitabine in patients with HER2-negative advanced breast cancer: GEICAM/2015-04 PANGEA-Breast

Background: Treatment options for advanced breast cancer (ABC) are multiple but unable to properly respond to current clinical needs. In particular, improved therapies are needed for triple negative and hormone receptor (HR)-positive but heavily pretreated patients. Pembrolizumab (P) is a human monoclonal antibody that blocks the PD-1/PD-L1 interaction hence potentiates anticancer T cell responses. Gemcitabine (G) is a cytotoxic drug with well-known immunostimulatory properties. Here, we report an ongoing phase II clinical trial to identify the Recommended Phase II Dose (RP2D) and the efficacy of the combination of these two agents in ABC patients. We hypothesize that these agents may synergize to induce responses with long term clinical benefit (ClinicalTrials.gov Identifier: NCT03025880).

Trial Design:

Eligible patients are HER2-negative ABC patients who received prior treatment with anthracyclines and taxanes and two or more prior lines of hormone therapy, if HR-positive disease. Patients with CNS involvement are also eligible if clinically stable. Treatment consists of 21-day cycles with 200 mg P on day 1 and G on days 1 and 8. In the safety dose testing, we use a standard 6+6 design with 2 dose levels (DL) of G: 1250 mg/m2 (DL0) and 1000 mg/m2 (DL1). Patients are treated until radiologic or symptomatic progression, or unacceptable toxicity. The primary objectives are RP2D and objective response rate (ORR) of the combination; secondary objectives include evaluation of safety and tolerability and other efficacy variables (progression-free survival [PFS], clinical benefit rate [CBR], response duration [RD] and overall survival [OS]). Efficacy is measured by RECIST 1.1. and irRECIST. Safety is measured using the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) 4.0. As exploratory objectives, immunological biomarkers are analyzed in tumor biopsies and blood samples and correlated with (1) clinical efficacy and (2) disease outcomes.Sequential tumor samples are collected at baseline, cycle 3 and at progression. Blood samples are drawn at baseline, cycle 3, and cycle 6, or at post-treatment visit (whatever occurs first). Tumor samples are characterized for intratumoral and stromal tumor-infiltrating lymphocytes, tumor-associated macrophages and myeloid-derived suppressor cells, PD-L1 expression in tumor cells and stroma. Moreover, molecular and genetic profiling will be performed. Blood samples are characterized for peripheral blood mononuclear cell (PBMC) phenotype (including expression of co-activatory and co-inhibitory receptors), cytokine profile, and activity of other immunosuppressive pathways (e.g., IDO1-dependent tryptophan catabolism). These results will be compared with data from a cohort of healthy volunteers.

A maximum of 65 patients will be included. The study is approved by the ethical committee and Competent Authority of Spain and already open for patient recruitment in 2 of the 10 participating sites.

Keywords:

Breast

HER2 negative

Pembrolizumab

Immunotherapy

Citation Format: de la Cruz L, Sánchez-Margalet V, Berraondo P, Benito S, Escudero MJ, Caballero R, Carrasco E, Galluzzi L, Rojo F. A multicenter phase II trial to evaluate the efficacy and safety of pembrolizumab and gemcitabine in patients with HER2-negative advanced breast cancer: GEICAM/2015-04 PANGEA-Breast [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT1-01-02.

Kir2.1-Nav1.5 Channel Complexes Are Differently Regulated than Kir2.1 and Nav1.5 Channels Alone

Cardiac Kir2.1 and Nav1.5 channels generate the inward rectifier K⁺ (I_K1) and the Na⁺ (I_Na) currents, respectively. There is a mutual interplay between the ventricular I_Na and I_K1 densities, because Nav1.5 and Kir2.1 channels exhibit positive reciprocal modulation. Here we compared some of the biological properties of Nav1.5 and Kir2.1 channels when they are expressed together or separately to get further insights regarding their putative interaction. First we demonstrated by proximity ligation assays (PLAs) that in the membrane of ventricular myocytes Nav1.5 and Kir2.1 proteins are in close proximity to each other (<40 nm apart). Furthermore, intracellular dialysis with anti-Nav1.5 and anti-Kir2.1 antibodies suggested that these channels form complexes. Patch-clamp experiments in heterologous transfection systems demonstrated that the inhibition of the Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) decreased the I_Na and the I_K1 generated by Nav1.5 and Kir2.1 channels when they were coexpressed, but not the I_K1 generated by Kir2.1 channels alone, suggesting that complexes, but not Kir2.1 channels, are a substrate of CaMKII. Furthermore, inhibition of CaMKII precluded the interaction between Nav1.5 and Kir2.1 channels. Inhibition of 14-3-3 proteins did not modify the I_Na and I_K1 densities generated by each channel separately, whereas it decreased the I_Na and I_K1 generated when they were coexpressed. However, inhibition of 14-3-3 proteins did not abolish the Nav1.5-Kir2.1 interaction. Inhibition of dynamin-dependent endocytosis reduced the internalization of Kir2.1 but not of Nav1.5 or Kir2.1-Nav1.5 complexes. Inhibition of cytoskeleton-dependent vesicular trafficking via the dynein/dynactin motor increased the I_K1, but reduced the I_Na, thus suggesting that the dynein/dynactin motor is preferentially involved in the backward and forward traffic of Kir2.1 and Nav1.5, respectively. Conversely, the dynein/dynactin motor participated in the forward movement of Kir2.1-Nav1.5 complexes. Ubiquitination by Nedd4-2 ubiquitin-protein ligase promoted the Nav1.5 degradation by the proteasome, but not that of Kir2.1 channels. Importantly, the Kir2.1-Nav1.5 complexes were degraded following this route as demonstrated by the overexpression of Nedd4-2 and the inhibition of the proteasome with MG132. These results suggested that Kir2.1 and Nav1.5 channels closely interact with each other leading to the formation of a pool of complexed channels whose biology is similar to that of the Nav1.5 channels.

Abstract OT3-02-07: A phase II study to compare fulvestrant (F) 500mg plus placebo versus (vs) F 500mg plus palbociclib (P) as first line treatment for postmenopausal women with hormone receptor (HR)-positive advanced breast cancer (BC) sensitive to endocrine therapy (ET). “The FLIPPER study” (GEICAM/2014-12)

Background: Delaying/overcoming resistance to ET in HR-positive HER2-negative BC patients (pts) is a major need to futhrt improve safe and efficacious treatment options. F is a selective estrogen receptor (ER) downregulator currently indicated for the treatment of HR-positive metastatic BC in postmenopausal women with disease progression following anti-estrogen therapy. In FIRST trial F 500mg improved median time to progression (TTP) over anastrozole (23.4 vs 13.1 months, respectively) in untreated metastatic BC. P is a selective reversible inhibitor of cyclin-dependent kinase 4/6. FDA granted its accelerated approval based on progression-free survival (PFS) in combination with letrozole for postmenopausal women with ER-positive and HER2-negative advanced BC as initial ET (PALOMA-1). In another study, after progression to ET, P in combination with F resulted in longer PFS than F alone (PALOMA-3).

The high median TTP achieved with F alone (FIRST) coupled with the significant benefit of adding P to F (PALOMA-3) suggest that F 500mg in combination with P in the first-line setting may significantly improve long-term disease control.

Trial Design:This is an international, randomized, double-blind, multicentre phase II study comparing F 500mg in combination with P vs F 500mg plus placebo as first line therapy in postmenopausal women with HR-positive, HER2-negative metastatic BC who have received ≥5 years of adjuvant ET for early disease and remained disease free for &gt;12 months following its completion or have “de novo” metastatic disease. HR and HER2 status will be based on central testing on the most recent tumour biopsy. Patients will be randomized 1:1. The primary objective is to compare the efficacy of both treatment arms in terms of PFS at 1 year according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 by investigator assessment. As secondary efficacy objectives,PFS, Objective Response Rate (ORR), Clinical Benefit Rate (CBR), Overall Survival (OS), and 1-year and 2-year survival probabilities, have been considered. Other secondary objectives include the comparison of safety, tolerability and health-related quality of life between the treatment arms. As exploratory objectives, the identification of promising biomarkers related with response to study therapy and primary/acquired drug resistance. Pts will be stratified by the site of disease (visceral vs non-visceral) and disease presentation at study entry (recurrent disease vs metastatic “de novo”). With a sample size of 190 pts, the analysis would have 80% power to detect a difference between both treatment arms, assuming PFS proportions of 0.545 and 0.695, respectively. This study is sponsored by GEICAM and Cancer Trials Ireland (formerly ICORG) is also participating. Recruitment started in February 2016 with 14 pts included. Analysis of the primary endpoint is planned for Q1 2018. ClinicalTrials.gov identifier:NCT02690480.

Citation Format: Moreno F, Martínez-Jañez N, Garau I, Guerra JA, Alarcón J, Bermejo B, Gonzalez-Cortijo L, Bueno C, Lao J, Bezares S, Rosell L, Blanch A, Caballero R, Carrasco E, Rojo F, Martín M, O'Connor M, Hernando A, Albanell J. A phase II study to compare fulvestrant (F) 500mg plus placebo versus (vs) F 500mg plus palbociclib (P) as first line treatment for postmenopausal women with hormone receptor (HR)-positive advanced breast cancer (BC) sensitive to endocrine therapy (ET). “The FLIPPER study” (GEICAM/2014-12) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr OT3-02-07.