Computational modelling of mouse atrio ventricular node action potential and automaticity.

The atrioventricular node (AVN) is a crucial component of the cardiac conduction system. Despite its pivotal role in regulating the transmission of electrical signals between atria and ventricles, a comprehensive understanding of the cellular electrophysiological mechanisms governing AVN function has remained elusive. This paper presents a detailed computational model of mouse AVN cell action potential (AP). Our model builds upon previous work and introduces several key refinements, including accurate representation of membrane currents and exchangers, calcium handling, cellular compartmentalization, dynamic update of intracellular ion concentrations, and calcium buffering. We recalibrated and validated the model against existing and unpublished experimental data. In control conditions, our model reproduces the AVN AP experimental features, (e.g. rate = 175 bpm, experimental range [121, 191] bpm). Notably, our study sheds light on the contribution of L-type calcium currents, through both Cav1.2 and Cav1.3 channels, in AVN cells. The model replicates several experimental observations, including the cessation of firing upon block of Cav1.3 or INa,r current. If block induces a reduction in beating rate of 11%. In summary, this work presents a comprehensive computational model of mouse AVN cell AP, offering a valuable tool for investigating pacemaking mechanisms and simulating the impact of ionic current blockades. By integrating calcium handling and refining formulation of ionic currents, our model advances understanding of this critical component of the cardiac conduction system, providing a platform for future developments in cardiac electrophysiology. KEY POINTS: This paper introduces a comprehensive computational model of mouse atrioventricular node (AVN) cell action potentials (APs). Our model is based on the electrophysiological data from isolated mouse AVN cells and exhibits an action potential and calcium transient that closely match the experimental records. By simulating the effects of blocking specific ionic currents, the model effectively predicts the roles of L-type Cav1.2 and Cav1.3 channels, T-type calcium channels, sodium currents (TTX-sensitive and TTX-resistant), and the funny current (If) in AVN pacemaking. The study also emphasizes the significance of other ionic currents, including IKr, Ito, IKur, in regulating AP characteristics and cycle length in AVN cells. The model faithfully reproduces the rate dependence of action potentials under pacing, opening the possibility of use in impulse propagation models. The population-of-models approach showed the robustness of this new AP model in simulating a wide spectrum of cellular pacemaking in AVN.

Caveolin-3 and Caveolin-1 Interaction Decreases Channel Dysfunction Due to Caveolin-3 Mutations.

Caveolae constitute membrane microdomains where receptors and ion channels functionally interact. Caveolin-3 (cav-3) is the key structural component of muscular caveolae. Mutations in CAV3 lead to caveolinopathies, which result in both muscular dystrophies and cardiac diseases. In cardiomyocytes, cav-1 participates with cav-3 to form caveolae; skeletal myotubes and adult skeletal fibers do not express cav-1. In the heart, the absence of cardiac alterations in the majority of cases may depend on a conserved organization of caveolae thanks to the expression of cav-1. We decided to focus on three specific cav-3 mutations (Δ62-64YTT; T78K and W101C) found in heterozygosis in patients suffering from skeletal muscle disorders. We overexpressed both the WT and mutated cav-3 together with ion channels interacting with and modulated by cav-3. Patch-clamp analysis conducted in caveolin-free cells (MEF-KO), revealed that the T78K mutant is dominant negative, causing its intracellular retention together with cav-3 WT, and inducing a significant reduction in current densities of all three ion channels tested. The other cav-3 mutations did not cause significant alterations. Mathematical modelling of the effects of cav-3 T78K would impair repolarization to levels incompatible with life. For this reason, we decided to compare the effects of this mutation in other cell lines that endogenously express cav-1 (MEF-STO and CHO cells) and to modulate cav-1 expression with an shRNA approach. In these systems, the membrane localization of cav-3 T78K was rescued in the presence of cav-1, and the current densities of hHCN4, hKv1.5 and hKir2.1 were also rescued. These results constitute the first evidence of a compensatory role of cav-1 in the heart, justifying the reduced susceptibility of this organ to caveolinopathies.

A detailed mathematical model of the human atrial cardiomyocyte: integration of electrophysiology and cardiomechanics.

Mechano-electric regulations (MER) play an important role in the maintenance of cardiac performance. Mechano-calcium and mechano-electric feedback (MCF and MEF) pathways adjust the cardiomyocyte contractile force according to mechanical perturbations and affects electro-mechanical coupling. MER integrates all these regulations in one unit resulting in a complex phenomenon. Computational modelling is a useful tool to accelerate the mechanistic understanding of complex experimental phenomena. We have developed a novel model that integrates the MER loop for human atrial cardiomyocytes with proper consideration of feedforward and feedback pathways. The model couples a modified version of the action potential (AP) Koivumäki model with the contraction model by Quarteroni group. The model simulates iso-sarcometric and isometric twitches and the feedback effects on AP and Ca2+ -handling. The model showed a biphasic response of Ca2+ transient (CaT) peak to increasing pacing rates and highlights the possible mechanisms involved. The model has shown a shift of the threshold for AP and CaT alternans from 4.6 to 4 Hz under post-operative atrial fibrillation, induced by depressed SERCA activity. The alternans incidence was dependent on a chain of mechanisms including RyRs availability time, MCF coupling, CaMKII phosphorylation, and the stretch levels. As a result, the model predicted a 10% slowdown of conduction velocity for a 20% stretch, suggesting a role of stretch in creation of substrate formation for atrial fibrillation. Overall, we conclude that the developed model provides a physiological CaT followed by a physiological twitch. This model can open pathways for the future studies of human atrial electromechanics. KEY POINTS: With the availability of human atrial cellular data, interest in atrial-specific model integration has been enhanced. We have developed a detailed mathematical model of human atrial cardiomyocytes including the mechano-electric regulatory loop. The model has gone through calibration and evaluation phases against a wide collection of available human in-vitro data. The usefulness of the model for analysing clinical problems has been preliminaryly tested by simulating the increased incidence of Ca2+ transient and action potential alternans at high rates in post-operative atrial fibrillation condition. The model determines the possible role of mechano-electric feedback in alternans incidence, which can increase vulnerability to atrial arrhythmias by varying stretch levels. We found that our physiologically accurate description of Ca2+ handling can reproduce many experimental phenomena and can help to gain insights into the underlying pathophysiological mechanisms.

Coupling and heterogeneity modulate pacemaking capability in healthy and diseased two-dimensional sinoatrial node tissue models.

Both experimental and modeling studies have attempted to determine mechanisms by which a small anatomical region, such as the sinoatrial node (SAN), can robustly drive electrical activity in the human heart. However, despite many advances from prior research, important questions remain unanswered. This study aimed to investigate, through mathematical modeling, the roles of intercellular coupling and cellular heterogeneity in synchronization and pacemaking within the healthy and diseased SAN. In a multicellular computational model of a monolayer of either human or rabbit SAN cells, simulations revealed that heterogenous cells synchronize their discharge frequency into a unique beating rhythm across a wide range of heterogeneity and intercellular coupling values. However, an unanticipated behavior appeared under pathological conditions where perturbation of ionic currents led to reduced excitability. Under these conditions, an intermediate range of intercellular coupling (900-4000 MΩ) was beneficial to SAN automaticity, enabling a very small portion of tissue (3.4%) to drive propagation, with propagation failure occurring at both lower and higher resistances. This protective effect of intercellular coupling and heterogeneity, seen in both human and rabbit tissues, highlights the remarkable resilience of the SAN. Overall, the model presented in this work allowed insight into how spontaneous beating of the SAN tissue may be preserved in the face of perturbations that can cause individual cells to lose automaticity. The simulations suggest that certain degrees of gap junctional coupling protect the SAN from ionic perturbations that can be caused by drugs or mutations.

Production and Quality Control of [177Lu]Lu-PSMA-I&T: Development of an Investigational Medicinal Product Dossier for Clinical Trials.

Since prostate cancer is the most commonly diagnosed malignancy in men, the theranostic approach has become very attractive since the discovery of urea-based PSMA inhibitors. Different molecules have been synthesized starting from the Glu-urea-Lys scaffold as the pharmacophore and then optimizing the linker and the chelate to improve functional characteristics. This article aimed to highlight the quality aspects, which could have an impact on clinical practice, describing the development of an Investigational Medicinal Product Dossier (IMPD) for clinical trials with [177Lu]Lu-PSMA-I&T in prostate cancer and other solid tumors expressing PSMA. The results highlighted some important quality issues of the final preparation: radiolabeling of PSMA-I&T with lutetium-177 needs a considerably longer time compared with the radiolabeling of the well-known [177Lu]Lu-PSMA-617. When the final product was formulated in saline, the stability of [177Lu]Lu-PSMA-I&T was reduced by radiolysis, showing a decrease in radiochemical purity (<95% in 24 h). Different formulations of the final product with increasing concentrations of ascorbic acid have been tested to counteract radiolysis and extend stability. A solution of 20 mg/mL of ascorbic acid in saline prevents radiolysis and ensures stability over 30 h.

Circulating androgen receptor gene amplification and resistance to 177Lu-PSMA-617 in metastatic castration-resistant prostate cancer: results of a Phase 2 trial.

BACKGROUND: In a Phase 2 clinical trial, we aimed to determine the lutetium-177 [177Lu]-PSMA-617 activity and the clinical utility of levels of plasma androgen receptor (AR) gene in patients with heavily pretreated metastatic castration-resistant prostate cancer (mCRPC). METHODS: We determined AR copy number in pretreatment plasma samples. We used logistic regression to estimate the odds ratio (OR) and 95% confidence intervals (95% CIs) in order to evaluate the independent relevance of AR status and to evaluate patients with early progressive disease (PD) defined as treatment interruption occurring within 4 months after the start of 177Lu-PSMA-617. RESULTS: Twelve of the 15 (80%) with AR gene gain and 5 of the 25 (20%) patients with no gain of AR had early PD (p = 0.0002). The OR for patients without PSA response having AR gain was 3.69 (95% CI 0.83-16.36, p = 0.085). The OR for patients with early PD having AR gain was 16.00, (95% CI 3.23-79.27, p = 0.0007). Overall, median PFS and OS were 7.5 and 12.4 months, respectively. AR-gained had a significant shorter OS compared to AR-normal patients (7.4 vs 19.1 months, p = 0.020). No treatment interruptions due to adverse effects were reported. DISCUSSION: Plasma AR status helped to indicate mCRPC with early resistance to 177Lu-PSMA-617. TRIAL REGISTRATION: NCT03454750.

177Lu-PRRT in advanced gastrointestinal neuroendocrine tumors: 10-year follow-up of the IRST phase II prospective study.

PURPOSE: In March 2014, we reported the activity and safety of 177Lu-DOTA-octreotate peptide receptor radionuclide therapy (Lu-PRRT) at two different dosages (18.5 GBq and 27.5 GBq in 5 cycles) in patients with progressive metastatic gastrointestinal neuroendocrine tumors (GI-NETs). Disease control rate (DCR) and toxicity were addressed. Herein, we report the late toxicity, progression-free survival (PFS), and overall survival (OS) in the same cohort after a 10-year follow-up. METHODS: We conducted an open-label, disease-oriented prospective phase II trial. From March 2008 to June 2011, 43 patients received 3.7 GBq or 5.5 GBq of Lu-PRRT every 6 to 8 weeks, each cycle repeated 5 times. All patients showed 68Gallium-DOTA-peptide PET/Octreoscan® positivity (score 3-4 Rotterdam scale) in known lesions. Tumor burden was estimated radiologically. Time-to-event data (PFS and OS) were described using Kaplan-Meier curves and compared with the log-rank test. RESULTS: Forty-three patients (28 males and 15 females) were evaluable and were monitored for a median period of 118 months (range 12.6-139.6). Median PFS in patients receiving 18.5 GBq was 59.8 months (95% confidence interval [95% CI] 14.3-79.6), identical to that of patients treated with 27.5 GBq (59.8 months, 95% CI 23.4-82.0). Median OS was 71.0 months (95% CI 46.1-107.3) in the group who received 18.5 GBq and 97.6 months (95% CI 64.3-not reached) in the group treated with 27.5 GBq (P = 0.22). Patients with progression limited to lymph nodes showed significantly longer median PFS and OS than those with hepatic lesions (P = 0.02 for PFS and P = 0.04 for OS). Age over 65 years at the time of PRRT was also significant for OS. Of note, no late hematological or renal toxicity was observed in either group. CONCLUSIONS: The long-term follow-up of the IRST phase II study shows that Lu-PRRT is a safe and effective therapy for patients with advanced GI-NET, the most important prognostic factor being tumor burden, hepatic lesions, and age. We believe that Lu-PRRT should be offered to patients with early-stage disease.

Combined use of 177Lu-DOTATATE and metronomic capecitabine (Lu-X) in FDG-positive gastro-entero-pancreatic neuroendocrine tumors.

PURPOSE: FDG-positive neuroendocrine tumors (NETs) have a poorer prognosis and exhibit shorter response duration to peptide receptor radionuclide therapy (PRRT). The aim of this prospective phase II study was to evaluate the efficacy and toxicity of PRRT with 177Lu-DOTATATE associated with metronomic capecitabine as a radiosensitizer agent in patients with advanced progressive FDG-positive gastro-entero-pancreatic (GEP) NETs. PATIENTS AND METHODS: Patients with advanced somatostatin receptor- and FDG-positive G1-G3 GEP-NETs (Ki67 < 55%) were treated with a cumulative activity of 27.5 GBq of 177Lu-DOTATATE divided in five cycles of 5.5 GBq each every 8 weeks. Capecitabine (1000-1500 mg daily) was administered orally in the inter-cycle period between 177Lu-DOTATATE treatments. Prior to commencing capecitabine, all patients were triaged with the dihydropyrimidine dehydrogenase (DPD) test. Only DPD-proficient individuals were enrolled. The primary objectives were disease control rate (DCR) and safety. Secondary aims included progression-free (PFS) and overall survival (OS). Treatment response was assessed per Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST 1.1). Toxicity was assessed by Common Terminology Criteria for Adverse Events (CTCAE) version 4.0. RESULTS: From August 2015 to December 2016, 37 subjects were consecutively enrolled. A total of 25 (68%) were affected by pancreatic neuroendocrine tumors (P-NETs), and 12 (32%) had gastrointestinal neuroendocrine tumors (GI-NETs). By grading (WHO 2010 classification), 12 patients (32%) had G1 (Ki67 ≤ 2%), 22 (59%) had G2 (3% < Ki67 ≤ 20%), and 3 patients (9%) had G3 (Ki67 > 20%) NETs. Grade 3 (G3) or 4 (G4) hematological toxicity occurred in 16.2% of patients. Other G3-G4 adverse events were diarrhea in 5.4% of cases and asthenia in 5.4%. No renal toxicity was observed for the duration of follow-up. In 37 patients, 33 were evaluable for response. Objective responses included partial response (PR) in 10 patients (30%) and stable disease (SD) in 18 patients (55%), with a DCR of 85%. The median follow-up was 38 months (range 4.6-51.1 months). The median PFS was 31.4 months (17.6-45.4), and mOS was not reached. CONCLUSIONS: This study demonstrated that the combination of PRRT with 177Lu-DOTATATE and metronomic capecitabine is active and well tolerated in patients with aggressive FDG-positive G1-G3 GEP-NETs. These data constitute the basis for a randomized study of PPRT alone vs. PRRT plus metronomic capecitabine.

Theragnostic in neuroendocrine tumors.

In the last few decades, the incidence and prevalence of neuroendocrine tumors has been increasing. The theragnostic approach, that allows the diagnosis and treatment of different neoplasms with the same ligand, is a typical nuclear medicine tool. Applied for years, is also pivotal in neuroendocrine tumors (NETs) where it has improved the diagnostic accuracy and the therapeutic efficacy with impact on patient's survival. Theragnostic also allows the identification of important prognostic factors such as tumor location and burden, presence of liver metastases and intensity of somatostatin receptors (SSTR) expression to consider in new and possibly combined studies to ameliorate patient's outcome. Moreover, the possibility to evaluate receptor expression even in non-NET malignancies has de facto widened the possible indications for PRRT. We believe that this innovative therapeutic approach will be implemented in next years by radiomics and biological tumors characterization to better address PRRT applications.

All-Optical Electrophysiology Refines Populations of In Silico Human iPSC-CMs for Drug Evaluation.

High-throughput in vitro drug assays have been impacted by recent advances in human induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) technology and by contact-free all-optical systems simultaneously measuring action potentials (APs) and Ca2+ transients (CaTrs). Parallel computational advances have shown that in silico simulations can predict drug effects with high accuracy. We combine these in vitro and in silico technologies and demonstrate the utility of high-throughput experimental data to refine in silico hiPSC-CM populations and to predict and explain drug action mechanisms. Optically obtained hiPSC-CM APs and CaTrs were used from spontaneous activity and under optical pacing in control and drug conditions at multiple doses. An updated version of the Paci2018 model was developed to refine the description of hiPSC-CM spontaneous electrical activity; a population of in silico hiPSC-CMs was constructed and calibrated using simultaneously recorded APs and CaTrs. We tested in silico five drugs (astemizole, dofetilide, ibutilide, bepridil, and diltiazem) and compared the outcomes to in vitro optical recordings. Our simulations showed that physiologically accurate population of models can be obtained by integrating AP and CaTr control records. Thus, constructed population of models correctly predicted the drug effects and occurrence of adverse episodes, even though the population was optimized only based on control data and in vitro drug testing data were not deployed during its calibration. Furthermore, the in silico investigation yielded mechanistic insights; e.g., through simulations, bepridil's more proarrhythmic action in adult cardiomyocytes compared to hiPSC-CMs could be traced to the different expression of ion currents in the two. Therefore, our work 1) supports the utility of all-optical electrophysiology in providing high-content data to refine experimentally calibrated populations of in silico hiPSC-CMs, 2) offers insights into certain limitations when translating results obtained in hiPSC-CMs to humans, and 3) shows the strength of combining high-throughput in vitro and population in silico approaches.

Human Purkinje in silico model enables mechanistic investigations into automaticity and pro-arrhythmic abnormalities.

Cardiac Purkinje cells (PCs) are implicated in lethal arrhythmias caused by cardiac diseases, mutations, and drug action. However, the pro-arrhythmic mechanisms in PCs are not entirely understood, particularly in humans, as most investigations are conducted in animals. The aims of this study are to present a novel human PCs electrophysiology biophysically-detailed computational model, and to disentangle ionic mechanisms of human Purkinje-related electrophysiology, pacemaker activity and arrhythmogenicity. The new Trovato2020 model incorporates detailed Purkinje-specific ionic currents and Ca2+ handling, and was developed, calibrated and validated using human experimental data acquired at multiple frequencies, both in control conditions and following drug application. Multiscale investigations were performed in a Purkinje cell, in fibre and using an experimentally-calibrated population of PCs to evaluate biological variability. Simulations demonstrate the human Purkinje Trovato2020 model is the first one to yield: (i) all key AP features consistent with human Purkinje recordings; (ii) Automaticity with funny current up-regulation (iii) EADs at slow pacing and with 85% hERG block; (iv) DADs following fast pacing; (v) conduction velocity of 160 cm/s in a Purkinje fibre, as reported in human. The human in silico PCs population highlights that: (1) EADs are caused by ICaL reactivation in PCs with large inward currents; (2) DADs and triggered APs occur in PCs experiencing Ca2+ accumulation, at fast pacing, caused by large L-type calcium current and small Na+/Ca2+ exchanger. The novel human Purkinje model unlocks further investigations into the role of cardiac Purkinje in ventricular arrhythmias through computer modeling and multiscale simulations.

PRRT neuroendocrine tumor response monitored using circulating transcript analysis: the NETest.

PURPOSE: Peptide receptor radionuclide therapy (PRRT) is effective for metastatic/inoperable neuroendocrine tumors (NETs). Imaging response assessment is usually efficient subsequent to treatment completion. Blood biomarkers such as PRRT Predictive Quotient (PPQ) and NETest are effective in real-time. PPQ predicts PRRT efficacy; NETest monitors disease. We prospectively evaluated: (1) NETest as a surrogate biomarker for RECIST; (2) the correlation of NETest levels with PPQ prediction. METHODS: Three independent 177Lu-PRRT-treated GEP-NET and lung cohorts (Meldola, Italy: n = 72; Bad-Berka, Germany: n = 44; Rotterdam, Netherlands: n = 41). Treatment response: RECIST1.1 (responder (stable, partial, and complete response) vs non-responder). Blood sampling: pre-PRRT, before each cycle and follow-up (2-12 months). PPQ (positive/negative) and NETest (0-100 score) by PCR. Stable < 40; progressive > 40). CgA (ELISA) as comparator. Samples de-identified, measurement and analyses blinded. Kaplan-Meier survival and standard statistics. RESULTS: One hundred twenty-two of the 157 were evaluable. RECIST stabilization or response in 67%; 33% progressed. NETest significantly (p < 0.0001) decreased in RECIST "responders" (- 47 ± 3%); in "non-responders," it remained increased (+ 79 ± 19%) (p < 0.0005). NETest monitoring accuracy was 98% (119/122). Follow-up levels > 40 (progressive) vs stable (< 40) significantly correlated with mPFS (not reached vs. 10 months; HR 0.04 (95%CI, 0.02-0.07). PPQ response prediction was accurate in 118 (97%) with a 99% accurate positive and 93% accurate negative prediction. NETest significantly (p < 0.0001) decreased in PPQ-predicted responders (- 46 ± 3%) and remained elevated or increased in PPQ-predicted non-responders (+ 75 ± 19%). Follow-up NETest categories stable vs progressive significantly correlated with PPQ prediction and mPFS (not reached vs. 10 months; HR 0.06 (95%CI, 0.03-0.12). CgA did not reflect PRRT treatment: in RECIST responders decrease in 38% and in non-responders 56% (p = NS). CONCLUSIONS: PPQ predicts PRRT response in 97%. NETest accurately monitors PRRT response and is an effective surrogate marker of PRRT radiological response. NETest decrease identified responders and correlated (> 97%) with the pretreatment PPQ response predictor. CgA was non-informative.

Dosimetry and safety of 177Lu PSMA-617 along with polyglutamate parotid gland protector: preliminary results in metastatic castration-resistant prostate cancer patients.

PURPOSE: Radioligand therapy (RLT) with 177Lu-PSMA-617 is a promising option for patients with metastatic castration-resistant prostate cancer (mCRPC). The present study was designed to define the safety and initial response to a minimal effective injected activity/cycle of 177Lu-PSMA-617 in mCRPC patients. New protective agents for salivary glands and kidney were co-administered and dosimetry was carried out. PATIENTS AND METHODS: A prospective single-arm, open label phase II study on mCRPC was activated at our institute in April 2017. Patients with histologically confirmed advanced mCRPC previously treated with standard life-prolonging agents were enrolled. Folic polyglutamate tablets were orally administered as parotid gland protectors and 500 mL of a 10% mannitol solution was intravenously infused to reduce kidney uptake before the injection of 3.7-5.5 GBq of 177Lu-PSMA-617 repeated four times at interval of 8 weeks. The adsorbed dose calculation was performed with MIRD formalism (OLINDA/EXM software). The Bryant and Day design was used to estimate the sample size taking account of both activity and toxicity. RESULTS: Forty-three eligible patients were evaluated for toxicity and initial response. Dosimetry was carried out in 13 patients. Two (4.8%) patients had G3 and 8 (19.5%) had G2 hematological toxicity. Only 3 (6.9%) patients had mild G1 salivary gland toxicity and 8 (19.5%) had G1 renal toxicity. A decrease of ≥ 30% in prostate-specific antigen (PSA) was achieved after the first cycle in 17 (40.5%) patients, of whom 13 had a PSA decline of >50% after the second cycle. The median adsorbed doses were 0.65 mGy/MBq (range 0.33-2.63) for parotid glands, 0.42 mGy/MBq (0.14-0.81) for kidneys, 0.036 mGy/MBq (0.023-0.067) for red marrow, and 0.038 mGy/MBq (0.018-0.135) for the whole body. CONCLUSION: In advanced, heavily pre-treated mCRPC patients, 3.7 GBq/cycle of 177Lu-PSMA-617 was safe and produced early biochemical and imaging responses at PSMA whole-body scan post injection. Dosimetry of salivary glands suggests that the co-administration of polyglutamate tablets may reduce salivary gland uptake. CLINICAL TRIAL REGISTRATION: EU Clinical Trials Register No.: 2016-002732-32; NCT03454750. Collection and assembly of data: April 2017 and February 2019.

Impact of liver tumour burden, alkaline phosphatase elevation, and target lesion size on treatment outcomes with 177Lu-Dotatate: an analysis of the NETTER-1 study.

PURPOSE: To assess the impact of baseline liver tumour burden, alkaline phosphatase (ALP) elevation, and target lesion size on treatment outcomes with 177Lu-Dotatate. METHODS: In the phase 3 NETTER-1 trial, patients with advanced, progressive midgut neuroendocrine tumours (NET) were randomised to 177Lu-Dotatate (every 8 weeks, four cycles) plus octreotide long-acting release (LAR) or to octreotide LAR 60 mg. Primary endpoint was progression-free survival (PFS). Analyses of PFS by baseline factors, including liver tumour burden, ALP elevation, and target lesion size, were performed using Kaplan-Meier estimates; hazard ratios (HRs) with corresponding 95% CIs were estimated using Cox regression. RESULTS: Significantly prolonged median PFS occurred with 177Lu-Dotatate versus octreotide LAR 60 mg in patients with low (< 25%), moderate (25-50%), and high (> 50%) liver tumour burden (HR 0.187, 0.216, 0.145), and normal or elevated ALP (HR 0.153, 0.177), and in the presence or absence of a large target lesion (diameter > 30 mm; HR, 0.213, 0.063). Within the 177Lu-Dotatate arm, no significant difference in PFS was observed amongst patients with low/moderate/high liver tumour burden (P = 0.7225) or with normal/elevated baseline ALP (P = 0.3532), but absence of a large target lesion was associated with improved PFS (P = 0.0222). Grade 3 and 4 liver function abnormalities were rare and did not appear to be associated with high baseline liver tumour burden. CONCLUSIONS: 177Lu-Dotatate demonstrated significant prolongation in PFS versus high-dose octreotide LAR in patients with advanced, progressive midgut NET, regardless of baseline liver tumour burden, elevated ALP, or the presence of a large target lesion. Clinicaltrials.gov : NCT01578239, EudraCT: 2011-005049-11.

Development of a CO2 Sensor for Extracorporeal Life Support Applications.

Measurement of carbon dioxide (CO2) in medical applications is a well-established method for monitoring patient's pulmonary function in a noninvasive way widely used in emergency, intensive care, and during anesthesia. Even in extracorporeal-life support applications, such as Extracorporeal Carbon Dioxide Removal (ECCO2R), Extracorporeal Membrane Oxygenation (ECMO), and cardiopulmonary by-pass (CPB), measurement of the CO2 concentration in the membrane oxygenator exhaust gas is proven to be useful to evaluate the treatment progress as well as the performance of the membrane oxygenator. In this paper, we present a new optical sensor specifically designed for the measurement of CO2 concentration in oxygenator exhaust gas. Further, the developed sensor allows measurement of the gas flow applied to the membrane oxygenator as well as the estimation of the CO2 removal rate. A heating module is implemented within the sensor to avoid water vapor condensation. Effects of temperature on the sensor optical elements of the sensors are disclosed, as well as a method to avoid signal-temperature dependency. The newly developed sensor has been tested and compared against a reference device routinely used in clinical practice in both laboratory and in vivo conditions. Results show that sensor accuracy fulfills the requirements of the ISO standard, and that is suitable for clinical applications.

Hypocalcemia-Induced Slowing of Human Sinus Node Pacemaking.

Each heartbeat is initiated by cyclic spontaneous depolarization of cardiomyocytes in the sinus node forming the primary natural pacemaker. In patients with end-stage renal disease undergoing hemodialysis, it was recently shown that the heart rate drops to very low values before they suffer from sudden cardiac death with an unexplained high incidence. We hypothesize that the electrolyte changes commonly occurring in these patients affect sinus node beating rate and could be responsible for severe bradycardia. To test this hypothesis, we extended the Fabbri et al. computational model of human sinus node cells to account for the dynamic intracellular balance of ion concentrations. Using this model, we systematically tested the effect of altered extracellular potassium, calcium, and sodium concentrations. Although sodium changes had negligible (0.15 bpm/mM) and potassium changes mild effects (8 bpm/mM), calcium changes markedly affected the beating rate (46 bpm/mM ionized calcium without autonomic control). This pronounced bradycardic effect of hypocalcemia was mediated primarily by ICaL attenuation due to reduced driving force, particularly during late depolarization. This, in turn, caused secondary reduction of calcium concentration in the intracellular compartments and subsequent attenuation of inward INaCa and reduction of intracellular sodium. Our in silico findings are complemented and substantiated by an empirical database study comprising 22,501 pairs of blood samples and in vivo heart rate measurements in hemodialysis patients and healthy individuals. A reduction of extracellular calcium was correlated with a decrease of heartrate by 9.9 bpm/mM total serum calcium (p < 0.001) with intact autonomic control in the cross-sectional population. In conclusion, we present mechanistic in silico and empirical in vivo data supporting the so far neglected but experimentally testable and potentially important mechanism of hypocalcemia-induced bradycardia and asystole, potentially responsible for the highly increased and so far unexplained risk of sudden cardiac death in the hemodialysis patient population.

Re-treatment with radium-223: 2-year follow-up from an international, open-label, phase 1/2 study in patients with castration-resistant prostate cancer and bone metastases.

BACKGROUND: Radium-223 dichloride (radium-223) is approved for patients with castration-resistant prostate cancer (CRPC), symptomatic bone metastases, and no visceral disease using a dosing regimen of 6 injections (55 kBq/kg intravenously; 1 injection every 4 weeks). Early results from international, open-label, phase 1/2 study NCT01934790 showed that re-treatment with radium-223 was well tolerated with favorable effects on disease progression. Here we report safety and efficacy findings from 2-year follow-up of the radium-223 re-treatment study. METHODS: Patients with CRPC and bone metastases who completed 6 initial radium-223 injections with no disease progression in bone and later progressed were eligible for radium-223 re-treatment (up to 6 additional radium-223 injections), provided that hematologic parameters were adequate and chemotherapy had not been administered after the initial course of radium-223. Concomitant cytotoxic agents were not allowed during re-treatment but were allowed at the investigator's discretion during follow-up; other concomitant agents for prostate cancer (including abiraterone acetate or enzalutamide) were allowed at investigator's discretion. The primary objective was safety. Exploratory objectives included time to radiographic bone progression, radiographic progression-free survival (rPFS), time to total alkaline phosphatase (tALP), and prostate-specific antigen (PSA) progression, overall survival (OS), time to first symptomatic skeletal event (SSE), and SSE-free survival, all calculated from re-treatment start. Evaluation of safety and exploratory efficacy objectives included active 2-year follow-up. Safety results from active follow-up and updated efficacy are reported. RESULTS: Overall, 44 patients were re-treated with radium-223; 29 (66%) completed all 6 injections, and 34 (77%) entered 2-year active follow-up, during which no new safety concerns and no serious drug-related adverse events were noted. rPFS events (progression or death) occurred in 19 (43%) of 44 patients; median rPFS was 9.9 months. Radiographic bone progression occurred in 5 (11%) of 44 patients. Median OS was 24.4 months. Median times to first SSE and SSE-free survival were 16.7 and 12.8 months, respectively. Median time to tALP progression was not reached; median time to PSA progression was 2.2 months. CONCLUSIONS: Re-treatment with radium-223 in this selected patient population was well tolerated, led to minimal hematologic toxicity, and provided continued disease control in bone at 2-year follow-up.

Ten-year experience of the multidisciplinary Osteoncology Center.

PURPOSE: Bone metastases (BMs) are responsible for high morbidity in patients. A multidisciplinary approach involving a team of specialists offers an effective therapeutic strategy based on disease characteristics, medical history, and performance status. We evaluated the impact of our 10-year multidisciplinary experience on the management of patients with BM. METHODS: We retrospectively analyzed 2194 medical reports of 1628 patients referred to our Osteoncology Center from 2005 to 2015. Cases were discussed weekly by a multidisciplinary team. RESULTS: Eight hundred thirty-eight (38.2%) of the 2194 visits were requested because of a risk of complications from BM. Antiblastic treatment and bone-targeted therapy were modified in 709 (66.3%) and 309 (31%) of cases, respectively. Radiotherapy was scheduled in 220 (20%) of the 1099 patients for whom information was recorded. Patients completed the Brief Pain Inventory (BPI) during their first visit, 1296 (59.1%) reporting pain (median intensity 4), and 537 (41.4%) experiencing a level that interfered substantially with daily activities. New ortheses and/or antalgic therapy was prescribed accordingly. After 7 days, 208 (16%) patients were re-evaluated and a new BPI administered. A significant improvement in the worst (p < 0.0001) and current pain (p = 0.03) was seen, together with a favorable impact on daily activities (p = 0.02). Two thousand fifty-one patients completed an anonymous questionnaire on the quality of the service, the majority (69.4%) expressing high satisfaction. CONCLUSIONS: Our 10-year osteoncology experience confirms the importance of a multidisciplinary approach to optimize BM management. Further evaluations are needed in relation to quality of life, outcome, and costs.

Acute effect of a peritoneal dialysis exchange on electrolyte concentration and QT interval in uraemic patients.

BACKGROUND: Hemodialysis (HD) sessions induce changes in plasma electrolytes that lead to modifications of QT interval, virtually associated with dangerous arrhythmias. It is not known whether such a phenomenon occurs even during peritoneal dialysis (PD). The aim of the study is to analyze the relationship between dialysate and plasma electrolyte modifications and QT interval during a PD exchange. METHODS: In 15 patients, two manual PD 4-h exchanges were performed, using two isotonic solutions with different calcium concentration (Ca++1.25 and Ca1.75++ mmol/L). Dialysate and plasma electrolyte concentration and QT interval (ECG Holter recording) were monitored hourly. A computational model simulating the ventricular action potential during the exchange was also performed. RESULTS: Dialysis exchange induced a significant plasma alkalizing effect (p < 0.001). Plasma K+ significantly decreased at the third hour (p < 0.05). Plasma Na+ significantly decreased (p < 0.001), while plasma Ca++ slightly increased only when using the Ca 1.75++ mmol/L solution (p < 0.01). The PD exchange did not induce modifications of clinical relevance in the QT interval, while a significant decrease in heart rate (p < 0.001) was observed. The changes in plasma K+ values were significantly inversely correlated to QT interval modifications (p < 0.001), indicating that even small decreases of K+ were consistently paralleled by small QT prolongations. These results were perfectly confirmed by the computational model. CONCLUSIONS: The PD exchange guarantees a greater cardiac electrical stability compared to the HD session and should be preferred in patients with a higher arrhythmic risk. Moreover, our study shows that ventricular repolarization is extremely sensitive to plasma K+ changes, also in normal range.

Dosimetry of 177Lu-PSMA-617 after Mannitol Infusion and Glutamate Tablet Administration: Preliminary Results of EUDRACT/RSO 2016-002732-32 IRST Protocol.

Radio-ligand therapy (RLT) with177Lu-PSMA-617 is a promising option for patients with metastatic castration-resistant prostate-cancer (mCRPC). A prospective phase-II study (EUDRACT/RSO,2016-002732-32) on mCRPC is ongoing at IRST (Meldola, Italy). A total of 9 patients (median age: 68 y, range: 53⁻85) were enrolled for dosimetry evaluation of parotid glands (PGs), kidneys, red marrow (RM) and whole body (WB). Folic polyglutamate tablets were orally administered as PGs protectors and 500 mL of a 10% mannitol solution was intravenously infused to reduce kidney uptake. The whole body planar image (WBI) and blood samples were acquired at different times post infusion (1 h, 16⁻24 h, 36⁻48 h and 120 h). Dose calculation was performed with MIRD formalism (OLINDA/EXM software). The median effective half-life was 33.0 h (range: 25.6⁻60.7) for PGs, 31.4 h (12.2⁻80.6) for kidneys, 8.2 h (2.5⁻14.7) for RM and 40.1 h (31.6⁻79.7) for WB. The median doses were 0.48 mGy/MBq (range: 0.33⁻2.63) for PGs, 0.70 mGy/MBq (0.26⁻1.07) for kidneys, 0.044 mGy/MBq (0.023⁻0.067) for RM and 0.04 mGy/MBq (0.02⁻0.11) for WB. A comparison with previously published dosimetric data was performed and a significant difference was found for PGs while no significant difference was observed for the kidneys. For PGs, the possibility of reducing uptake by administering glutamate tablets during RLT seems feasible while further research is warranted for a more focused evaluation of the reduction in kidney uptake.