NNC6019–0001, a humanized monoclonal antibody, in patients with transthyretin amyloid cardiomyopathy (ATTR-CM): rationale and study design of a phase 2, randomized, placebo-controlled trial

Introduction

Transthyretin amyloid cardiomyopathy (ATTR-CM) is a chronic condition associated with progressive heart failure, resulting from extracellular deposition of misfolded transthyretin (TTR) protein as amyloid fibrils in the myocardium. Currently, there are few disease-modifying treatments. NNC6019–0001 is a humanized monoclonal antibody designed to deplete amyloid via antibody-mediated phagocytosis by targeting a unique epitope that is exposed only on misfolded monomeric and aggregated forms of TTR. In a phase 1, open-label, 3-month dose escalation trial, NNC6019–0001 was well tolerated at all doses tested (up to and including 30 mg/kg).1 The maximum tolerated dose was not reached. Exploratory cardiac endpoints were stable or indicated a possible benefit.

Purpose

To evaluate the effect of NNC6019–0001 30 mg/kg and 100 mg/kg on cardiac functional endpoints and predictive biomarkers in patients with ATTR-CM, and to assess pharmacokinetics, safety and tolerability, to establish the optimal dose for a phase 3 trial.

Methods

This is a randomized, double-blind, placebo-controlled trial recruiting 99 patients with hereditary or wild-type ATTR-CM (Figure). Inclusion criteria are New York Heart Association (NYHA) class II or III heart failure, left ventricle wall thickening (LVWT) ≥12 mm, N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels ≥650 pg/mL in sinus rhythm and >1000 pg/mL in atrial fibrillation, and a 6-minute walk test (6MWT) distance of 150–450 m. Patients will be randomly assigned to receive intravenous NNC6019–0001 30 mg/kg or 100 mg/kg or placebo, each in addition to standard of care, every 4 weeks for 52 weeks, followed by a 12-week follow-up. In a sentinel dosing phase, three patients per arm will receive the study drug or placebo, in combination with 24-hour inpatient cardiac monitoring and 7 days of continuous cardiac (tele-) monitoring. The primary endpoints are change from baseline to week 52 in 6MWT and in NT-proBNP levels. Secondary endpoints include cardiac measures: extracellular volume on cardiac magnetic resonance imaging, global longitudinal strain, troponin T levels, hospitalization due to cardiovascular events, and urgent visits due to heart failure. Quality of life will be assessed using the Kansas City Cardiomyopathy Questionnaire (KCCQ). All-cause mortality, pharmacokinetics and treatment-emergent adverse events will also be assessed.

Results

The trial will start mid-2022 with global recruitment.

Conclusion

Disease-modifying treatments are needed for patients with ATTR-CM, where treatment is often limited to managing symptoms and best supportive care; the first disease-modifying therapies recently became available. This phase 2 trial will be used to determine the appropriate dose for the phase 3 trial of NNC6019–0001, a novel antibody therapy designed to deplete amyloid in patients with ATTR-CM.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): This trial was funded by Novo Nordisk A/S. Medical writing support was provided by Johanna Scheinost PhD, PharmaGenesis Oxford Central, Oxford, UK, with funding from Novo Nordisk A/S.

[Amyloidosis of the heart]

Amyloidosis is a heterogeneous group of diseases characterized by the pathological deposition of autologous proteins in an antiparallel β-sheet confirmation forming non-branching linear fibrils of indefinite length and an approximate diameter of 10-12 nm. Cardiac amyloidosis is caused by deposits in the heart and may lead to cardiac arrhythmia and low output failure. Following the diagnosis, classification of the amyloid protein and evaluation of further organ involvement is mandatory. Treatment approaches are based on reduction of the production of amyloid precursor proteins. Standard heart failure treatment is usually not well tolerated and the underlying disease remains unaffected. Cardiac amyloidosis, especially of the light chain type, is associated with a poor outcome. The clinical picture is uncharacteristic, therefore correct diagnosis of cardiac amyloidosis is often delayed in many patients. Combination of clinical symptoms of different organ systems should alert the physician to the diagnosis of amyloidosis.

[Return to work after heart transplantation]

Heart transplantation is the most effective treatment option for patients with end-stage heart failure to improve exercise tolerance and quality of life. This increase in quality of life may assume that heart transplant recipients are also able to return to their work. In general, there are no medical reasons to oppose a return to work. Despite enormous advances in medical rehabilitation after heart transplantation, the rate of working people among heart transplant recipients is very low. According to a survey at the Heidelberg Heart Transplant Center, only 37% of the heart transplant recipients return to work. This may be caused by tranplant-related problems as well as factors independent of heart transplantation. Furthermore, the psychological burden due to heart transplantation might hamper professional rehabilitation. Thus, psychotherapeutical support during transplant process appears to be appropriate. As a major issue for a return to work appears to be the patient's will, the voluntary nature of return to work step by step has to be limited. Programmes with close collaboration between physicians, health insurance companies, retirement insurance companies, employers, and especially the patients are necessary to increase the rate of professional rehabilitation and to underscore the health economic justification of heart transplant programmes.

[Risk stratification and treatment of cardiac amyloidoses]

Cardiac amyloidoses are a heterogeneous group of cardiomyopathies that are resistant to treatment and are associated with a poor outcome. Standard heart failure treatment is usually not well tolerated and the underlying disease remains unaffected. The clinical picture is uncharacteristic. Cardiac amyloidosis is often associated with dysfunction of additional organs. Early cardiac amyloid involvement usually reveals left ventricular hypertrophy, impairment of longitudinal shortening and diastolic ventricular function. Without adequate therapy (bi-)ventricular hypertrophy will progress to severe systolic ventricular function decrease. The combination of low voltage pattern, left ventricular hypertrophy and granular sparkling is characteristic for advanced cardiac amyloid involvement. Cardiac magnetic resonance imaging and scintigraphy yield further information on the pattern and severity of cardiac involvement. In unclear cases (left ventricular) endomyocardial biopsy is necessary. Detection of early cardiac involvement and proper identification of patients at high risk for sudden cardiac death due to rapid progressive amyloidosis is still incompletely defined. Referral to specialized centers is strongly recommended.

[Current diagnostic and therapy of light chain amyloidosis]

Amyloidoses are protein-folding disorders in which soluble proteins are deposited as insoluble fibrillar aggregates due to a change in protein conformation. This might occur intra- or extracellularly, systemically or in a localized manner. The light chain type is the most common form of systemic amyloidoses and has the worst prognosis. The underlying disease is a monoclonal, mostly non-malignant plasma cell disorder. The causative treatment is the reduction of the amyloidogenic light chains with conventional or high-dose chemotherapy. Meanwhile, the"new drugs" used in multiple myeloma are also successfully applied. Early diagnosis is important to be able to treat patients effectively and to avoid further deterioration of organ function. Patients with newly diagnosed amyloidosis should be referred to a specialized center for consultation, diagnosis and treatment recommendation.

[MR imaging in cardiac amyloidosis--morphology, function and late enhancement]

PURPOSE

Since limited data is available using MR imaging in cardiac amyloidosis, the purpose of our study was to evaluate morphological and functional differences of the heart using cardiac MRI.

MATERIALS AND METHODS

19 consecutive patients (14 males, 5 females, mean age 59 +/- 6 years) with histologically proven cardiac amyloidosis were evaluated with MRI at 1.5 T. Results were compared with data of 10 healthy, age-matched control subjects (5 males, 5 females, mean age 60 +/- 6 years). Functional and morphological data including late enhancement (LE) was acquired.

RESULTS

Compared to the control group, patients with cardiac amyloidosis had thickened atrial walls and dilated atriums. Both ventricles and the interventricular septum were thickened. The LV hypertrophy was focal in 11 / 19 (58 %) and global in 4 / 19 (21 %) of patients. A myocardial edema occurred in 2 / 19 patients with cardiac amyloidosis (11 %). An edema of the myocardium was visible in 2 / 19 (11 %) of patients. The LV ejection fraction was statistically significantly decreased. The prevalence of LE was 74 % (14 / 19 of patients). LE was detected predominantly in the LV anterior wall and in the interventricular septum. Within the segments LE was located predominantly in a subendocardial location. Between patients with and without LE no statistically significant differences of functional and morphological results were able to be established.

CONCLUSION

There are three major outcomes of our assessment: 1. The LV hypertrophy is focal in the majority of patients with cardiac amyloidosis. 2. No statistically significant differences can be established in regard to the functional and morphological features between patients with and without LE. 3. Myocardial edema is a possible feature in cardiac amyloidosis.

Respiratory muscle dysfunction in idiopathic pulmonary arterial hypertension

Idiopathic pulmonary arterial hypertension (IPAH) is a pulmonary vasculopathy of unknown aetiology. Dyspnoea, peripheral airway obstruction and inefficient ventilation are common in IPAH. Data on respiratory muscle function are lacking. This prospective single-centre study included 26 female and 11 male patients with IPAH in World Health Organization functional classes II-IV. Mean+/-SD pulmonary artery pressure was 48.6+/-16.9 in females and 53.1+/-22.9 mmHg in males; cardiac output was 3.7+/-1.3 and 4.2+/-1.7 L x min(-1). Maximal inspiratory pressure (PI,max) was lower in the female patients than in 20 controls (5.3+/-2.0 versus 8.2+/-2.0 kPa). In the male patients, PI,max was lower than in 25 controls (6.8+/-2.2 versus 10.5+/-3.7 kPa). Maximal expiratory pressure (PE,max) was lower in the female patients than in controls (6.2+/-2.6 versus 9.5+/-2.1 kPa), and in male patients as compared to controls (7.1+/-1.6 versus 10.3+/-3.9 kPa). There was no correlation between PI,max or PE,max and parameters of pulmonary haemodynamics or exercise testing. The ratio of mouth occlusion pressure within the first 0.1 s of inspiration and PI,max was higher in IPAH than in controls (females 0.067+/-0.066 versus 0.021+/-0.008; males 0.047+/-0.061 versus 0.023+/-0.016). In conclusion, this study provides the first evidence of inspiratory and expiratory muscle weakness in idiopathic pulmonary arterial hypertension. The pathomechanisms and the prognostic significance should be further investigated.

Central hypercapnic chemoreflex modulation of renal sympathetic nerve activity in experimental heart failure

Activation of the sympathetic nervous system plays an important role in the pathophysiology and progression of congestive heart failure (CHF). The precise mechanisms responsible for sympathetic activation in CHF are not yet clearly established. An altered central hypercapnic chemoreflex modulation of sympathetic nerve activity (SNA) might be an explanation. Therefore, the response of postganglionic renal SNA to elevation of CO2 concentration in the inspiratory air to 2, 4, and 6% was determined in anesthetized, artificially ventilated rats after denervation of peripheral baro- and chemoreceptors 2 weeks (group A; n=8) or 6 weeks (group B; n=11) after induction of an aorto-caval shunt, or 4 weeks after aortic banding (group C; n=7). In all CHF models, left ventricular enddiastolic pressure was increased (A 8 +/- 1, B 8 +/- 1, C 10 +/- 2 mmHg) as compared to sham operated controls (A 3 +/- 1, B 4 +/- 1, C 5 +/- 1 mmHg). Indicative of left ventricular hypertrophy and pulmonary congestion, wet weight of heart (A + 60%, B + 93%, C + 49%) and lungs (A + 15%, B + 36%, C + 12%) were also enhanced as compared to controls. Elevation of inspiratory CO2 concentration to 2,4, and 6% increased renal SNA by approximately 10, 20, and 30% from resting activity in all groups. The maximum SNA responses at 6% CO2 in the groups with CHF (A + 390 +/- 95, B + 425 +/- 133, C + 368 +/- 158 microVs) did not differ from those in the respective controls (A + 510 +/- 130, B + 570 +/- 180, C + 275 +/- 25 microVs). It is concluded that under these experimental conditions the central hypercapnic chemoreflex sensitivity is not altered in either of the employed models of CHF and therefore may not play a major role for the well-known elevation of SNA in CHF.