Real-world outcomes among patients with HER2+ metastatic breast cancer with brain metastases.

BACKGROUND: Among patients with human epidermal growth factor receptor 2-positive (HER2+) metastatic breast cancer (MBC), incidence of brain metastases (BMs) is relatively high and increasing. Despite the high unmet need for patients with HER2+ MBC and BMs, real-world data on treatment patterns and outcomes for these patients are limited. OBJECTIVE: To compare treatment patterns and overall survival (OS) among patients with HER2+ MBC with and without BMs in the United States. METHODS: This was a real-world retrospective cohort study in which adults diagnosed with HER2+ MBC between January 1, 2016, and May 31, 2019, were identified in the Flatiron Health electronic health records database. The cohort was stratified by presence of BMs at MBC diagnosis (baseline) and before the initiation of each line of therapy (LOT). Key outcomes were OS and systemic therapy/regimen used within each LOT. An adjusted Cox proportional hazards model was used to evaluate the impact of BMs on OS. RESULTS: Of 1,755 included patients, 173 (9.9%) had BMs at baseline. Trastuzumab+ pertuzumab-based regimens were the most common first- (n = 689, 44.3%) and second-line (n = 316, 35.3%) treatments for all patients. Among patients with BMs, trastuzumab emtansine was the most common third-line regimen (n = 18, 23.4%). Lapatinib-based regimens were used more frequently among patients with BMs but were used by less than 20% of patients with BMs within any LOT. Median OS was 22.3 and 37.3 months for patients with and without BMs at baseline, respectively. Patients with BMs had a higher risk of death compared with patients without BMs (HR, 3.2; 95% CI = 2.6-3.8). CONCLUSIONS: BMs are associated with an increased risk of mortality among patients with HER2+ MBC. Further studies are needed to evaluate the extent to which novel systemic therapies for HER2+ MBC address the unmet need among patients with BMs. DISCLOSURES: This study was funded by Seagen Inc. Andres Forero-Torres is an employee of and owns stock in Seagen Inc. Kendra DeBusk is an employee of Seagen Inc. and owns stock in Seagen Inc. and Roche. Andy Surinach and Yutong Liu are employees of Genesis Research, which received funding from Seagen Inc. in connection with this study. At the time of this study, Chimeka Ike was an employee of Seagen Inc. and owns stock in Seagen Inc. At the time of this study, Nicolas Lindegger was an employee of Seagen Inc., Seagen International GmbH, and owns stock in Seagen Inc. and Roche. At the time of this study, Naomi Schwartz was a paid consultant to Seagen Inc.; she currently is an employee of and owns stock in Seagen Inc.

Safety of trastuzumab emtansine (T-DM1) in patients with HER2-positive advanced breast cancer: Primary results from the KAMILLA study cohort 1.

BACKGROUND: Many patients with metastatic human epidermal growth factor receptor 2 (HER2)-positive breast cancer (BC) are candidates for trastuzumab emtansine (T-DM1) treatment sometime in their disease history. KAMILLA evaluated safety of T-DM1 in patients with previously treated HER2-positive locally advanced or metastatic BC (advanced BC). METHODS: KAMILLA (NCT01702571) is a single-arm, open-label, international, phase IIIb safety study of patients with HER2-positive advanced BC with progression after prior treatment with chemotherapy and a HER2-directed agent for MBC or within 6 months of completing adjuvant therapy. Patients received T-DM1 (3.6 mg/kg every 3 weeks) until unacceptable toxicity, withdrawal or disease progression. RESULTS: Among 2002 treated patients, median age was 55 years (range, 26-88; 373 [18.6%] aged ≥65 years), 1321 (66.0%) received ≥2 prior metastatic treatment lines and 398 (19.9%) had baseline central nervous system metastases. Adverse events (AEs) and serious AEs occurred in 1862 (93.0%) and 427 (21.3%) patients, respectively. Grade ≥3 AEs occurred in 751 (37.5%) patients; the three most common (individual Medical Dictionary for Regulatory Activity terms) were anaemia (3.0%), thrombocytopaenia (2.7%) and fatigue (2.5%). Median progression-free survival (PFS) was 6.9 months (95% confidence interval [CI], 6.0-7.6). Median overall survival (OS) was 27.2 months (95% CI, 25.5-28.7). With increasing lines of prior advanced therapy (0-1 versus 4+), median PFS and OS decreased numerically from 8.3 to 5.6 months and from 31.3 to 22.5 months, respectively. CONCLUSIONS: KAMILLA is the largest cohort of T-DM1-treated patients studied to date. Results are consistent with prior randomised studies, thereby supporting T-DM1 as safe, tolerable and efficacious treatment for patients with previously treated HER2-positive advanced BC.

Macitentan, a dual endothelin receptor antagonist for the treatment of pulmonary arterial hypertension, does not affect cardiac repolarization in healthy subjects.

Macitentan is an orally active dual endothelin receptor antagonist, which demonstrated a reduction of the risk of morbidity/mortality events in pulmonary arterial hypertension patients. This double-blind, randomized, placebo- and positive-controlled, four-way crossover thorough QTc study was designed to investigate the effects of therapeutic and supratherapeutic doses of macitentan on cardiac repolarization in healthy male and female subjects. Each subject received the following treatments: moxifloxacin 400 mg, macitentan 10 mg, macitentan 30 mg, and placebo. Each treatment period lasted 9 days and was followed by at least 10 days of washout. The primary endpoint of this study was the baseline-adjusted, placebo-corrected QT interval corrected using the Fridericia method (ΔΔQTcF). Pharmacokinetic (PK), safety, and tolerability assessments were performed during each treatment. A total of 64 subjects were randomized. The upper bound of the 2-sided 90% confidence interval for ΔΔQTcF following macitentan was <10 ms at all time points and no correlation was observed between ΔΔQTcF and PK parameters. Findings in the analysis of the morphological patterns of the ECGs were randomly distributed across all treatments and did not indicate an association with macitentan. Macitentan was well tolerated in this study. Headache and nasopharyngitis were the most frequently reported adverse events. No effects on clinical laboratory and vital signs parameters were observed. In summary, repeated doses of macitentan 10 mg and 30 mg did not indicate any pro-arrhythmic potential.

Pharmacokinetics of the novel dual endothelin receptor antagonist macitentan in subjects with hepatic or renal impairment.

Macitentan is under development for the treatment of pulmonary arterial hypertension (PAH). Patients with PAH may suffer from comorbidities such as renal or hepatic impairment. Two prospective, single-center, open-label studies evaluated the pharmacokinetics of macitentan and its metabolites (pharmacologically active ACT-132577 and inactive ACT-373898) in healthy subjects and in subjects with mild, moderate, and severe hepatic impairment or severe renal function impairment (SRFI). After administering a single oral dose of 10 mg macitentan the pharmacokinetic parameters including area under the curve from zero to infinity (AUC∞) were derived from plasma concentration-time profiles. Exposure to macitentan and ACT-132577 was lower in hepatically impaired versus healthy subjects, with no correlation with the degree of hepatic impairment. Exposure to ACT-373898 was lower in subjects with moderate hepatic impairment only. Plasma concentration-time profiles for macitentan and ACT-132577 (active) were similar in healthy subjects and subjects with SRFI. AUC∞ of ACT-373898 (inactive) was 7.3-fold higher in subjects with SRFI versus healthy subjects. No safety concerns were raised in either study. Based on these observations, pharmacokinetic alterations of macitentan due to hepatic or renal function impairment are not considered clinically relevant and no dose adjustment is necessary in these patients.

Phosphorylation of the ryanodine receptor mediates the cardiac fight or flight response in mice.

During the classic "fight-or-flight" stress response, sympathetic nervous system activation leads to catecholamine release, which increases heart rate and contractility, resulting in enhanced cardiac output. Catecholamines bind to ß-adrenergic receptors, causing cAMP generation and activation of PKA, which phosphorylates multiple targets in cardiac muscle, including the cardiac ryanodine receptor/calcium release channel (RyR2) required for muscle contraction. PKA phosphorylation of RyR2 enhances channel activity by sensitizing the channel to cytosolic calcium (Ca²+). Here, we found that mice harboring RyR2 channels that cannot be PKA phosphorylated (referred to herein as RyR2-S2808A+/+ mice) exhibited blunted heart rate and cardiac contractile responses to catecholamines (isoproterenol). The isoproterenol-induced enhancement of ventricular myocyte Ca²+ transients and fractional shortening (contraction) and the spontaneous beating rate of sinoatrial nodal cells were all blunted in RyR2-S2808A+/+ mice. The blunted cardiac response to catecholamines in RyR2-S2808A+/+ mice resulted in impaired exercise capacity. RyR2-S2808A+/+ mice were protected against chronic catecholaminergic-induced cardiac dysfunction. These studies identify what we believe to be new roles for PKA phosphorylation of RyR2 in both the heart rate and contractile responses to acute catecholaminergic stimulation.

Leaky Ca2+ release channel/ryanodine receptor 2 causes seizures and sudden cardiac death in mice.

The Ca2+ release channel ryanodine receptor 2 (RyR2) is required for excitation-contraction coupling in the heart and is also present in the brain. Mutations in RyR2 have been linked to exercise-induced sudden cardiac death (catecholaminergic polymorphic ventricular tachycardia [CPVT]). CPVT-associated RyR2 mutations result in "leaky" RyR2 channels due to the decreased binding of the calstabin2 (FKBP12.6) subunit, which stabilizes the closed state of the channel. We found that mice heterozygous for the R2474S mutation in Ryr2 (Ryr2-R2474S mice) exhibited spontaneous generalized tonic-clonic seizures (which occurred in the absence of cardiac arrhythmias), exercise-induced ventricular arrhythmias, and sudden cardiac death. Treatment with a novel RyR2-specific compound (S107) that enhances the binding of calstabin2 to the mutant Ryr2-R2474S channel inhibited the channel leak and prevented cardiac arrhythmias and raised the seizure threshold. Thus, CPVT-associated mutant leaky Ryr2-R2474S channels in the brain can cause seizures in mice, independent of cardiac arrhythmias. Based on these data, we propose that CPVT is a combined neurocardiac disorder in which leaky RyR2 channels in the brain cause epilepsy, and the same leaky channels in the heart cause exercise-induced sudden cardiac death.

Altered Na+ channels promote pause-induced spontaneous diastolic activity in long QT syndrome type 3 myocytes.

Long QT syndrome (LQTS) type 3 (LQT3), typified by the DeltaKPQ mutation (LQT3 mutation in which amino acid residues 1505 to 1507 [KPQ] are deleted), is caused by increased sodium entry during the action potential plateau resulting from mutation-altered inactivation of the Na(v)1.5 channel. Although rare, LQT3 is the most lethal of common LQTS variants. Here we tested the hypothesis that cellular electrical dysfunction, caused not only by action potential prolongation but also by mutation-altered Na(+) entry, distinguishes LQT3 from other LQTS variants and may contribute to its distinct lethality. We compared cellular electrical activity in myocytes isolated from mice heterozygous for the DeltaKPQ mutation (DeltaKPQ) and myocytes from wild-type littermates. Current-clamp pause protocols induced rate-dependent spontaneous diastolic activity (delayed after depolarizations) in 6 of 7 DeltaKPQ, but no wild-type, myocytes (n=11) tested. Voltage-clamp pause protocols that independently control depolarization duration and interpulse interval identified a distinct contribution of both depolarization duration and mutant Na(+) channel activity to the generation of Ca(i)(2+)-dependent diastolic transient inward current. This was found at rates and depolarization durations relevant both to the mouse model and to LQT3 patients. Flecainide, which preferentially inhibits mutation-altered late Na(+) current and is used to treat LQT3 patients, suppresses transient inward current formation in voltage-clamped DeltaKPQ myocytes. Our results demonstrate a marked contribution of mutation-altered Na(+) entry to the incidence of pause-dependent spontaneous diastolic activity in DeltaKPQ myocytes and suggest that altered Na(+) entry may contribute to the elevated lethality of LQT3 versus other LQTS variants.

The nitrodibenzofuran chromophore: a new caging group for ultra-efficient photolysis in living cells.

Photochemical uncaging of bio-active molecules was introduced in 1977, but since then, there has been no substantial improvement in the properties of generic caging chromophores. We have developed a new chromophore, nitrodibenzofuran (NDBF) for ultra-efficient uncaging of second messengers inside cells. Photolysis of a NDBF derivative of EGTA (caged calcium) is about 16-160 times more efficient than photolysis of the most widely used caged compounds (the quantum yield of photolysis is 0.7 and the extinction coefficient is 18,400 M(-1) cm(-1)). Ultraviolet (UV)-laser photolysis of NDBF-EGTA:Ca(2+) rapidly released Ca(2+) (rate of 20,000 s(-1)) and initiated contraction of skinned guinea pig cardiac muscle. NDBF-EGTA has a two-photon cross-section of approximately 0.6 GM and two-photon photolysis induced localized Ca(2+)-induced Ca(2+) release from the sarcoplasmic recticulum of intact cardiac myocytes. Thus, the NDBF chromophore has great promise as a generic and photochemically efficient protecting group for both one- and two-photon uncaging in living cells.

Paradoxical SR Ca2+ release in guinea-pig cardiac myocytes after beta-adrenergic stimulation revealed by two-photon photolysis of caged Ca2+.

In heart muscle the amplification and shaping of Ca(2+) signals governing contraction are orchestrated by recruiting a variable number of Ca(2+) sparks. Sparks reflect Ca(2+) release from the sarcoplasmic reticulum (SR) via Ca(2+) release channels (ryanodine receptors, RyRs). RyRs are activated by Ca(2+) influx via L-type Ca(2+) channels with a specific probability that may depend on regulatory mechanisms (e.g. beta-adrenergic stimulation) or diseased states (e.g. heart failure). Changes of RyR phosphorylation may be critical for both regulation and impaired function in disease. Using UV flash photolysis of caged Ca(2+) and short applications of caffeine in guinea-pig ventricular myocytes, we found that Ca(2+) release signals on the cellular level were largely governed by global SR content. During beta-adrenergic stimulation resting myocytes exhibited smaller SR Ca(2+) release signals when activated by photolysis (62.3% of control), resulting from reduced SR Ca(2+) content under these conditions (58.6% of control). In contrast, local signals triggered with diffraction limited two-photon photolysis displayed the opposite behaviour, exhibiting a larger Ca(2+) release (164% of control) despite reduced global and local SR Ca(2+) content. This apparent paradox implies changes of RyR open probabilities after beta-adrenergic stimulation, enhancing local regenerativity and reliability of Ca(2+) signalling. Thus, our results underscore the importance of phosphorylation of RyRs (or of a related protein), as a regulatory physiological mechanism that may also provide new therapeutic avenues to recover impaired Ca(2+) signalling during cardiac disease.