Pharmacotherapeutic group: Cardiac therapy, Other cardiac preparations, ATC code: Not yet assigned
Mechanism of action
Aficamten is a reversible allosteric cardiac myosin inhibitor that binds directly to the motor domain of cardiac myosin and prevents it from entering the force-producing state. Nonclinical data indicate that aficamten is selective for the cardiac isoform of myosin compared to fast skeletal myosin. Specifically, aficamten inhibited bovine cardiac myofibrillar ATPase with approximately 5-fold higher potency than rabbit fast skeletal myofibrillar ATPase. It is designed to reduce the hypercontractility in the cardiac sarcomere fundamental to the pathophysiology of HCM. The consequent reduction in cardiac contractility reduces LVOT obstruction in HCM patients.
Pharmacodynamic effects
LVEF
In SEQUOIA-HCM study, the mean [standard deviation (SD)] resting LVEF at baseline was 74.8% (5.5%) for patients in the aficamten group and 74.8% (6.3%) in the placebo group. Consistent with the mechanism of action of aficamten, least squares (LS) mean [standard error (SE)] change from baseline in LVEF was -6.8% (0.6%) in the aficamten group and -2% (0.6%) in the placebo group at the end of the 24-week treatment period. Mean LVEF was similar between the aficamten and placebo groups 4 weeks after the end of treatment.
LVOT obstruction
In SEQUOIA-HCM study, the mean (SD) resting and Valsalva LVOT‑G at baseline were 54.8 (27) and 82.9 (32) mmHg for patients in the aficamten group and 55.3 (32.2) and 83.3 (32.7) mmHg in the placebo group. At week 24, the LS mean (SE) changes from baseline in resting and Valsalva LVOT‑G were -35.8 (2.1) mmHg and -48.1 (2.4) mmHg, respectively, for the aficamten group and 4.1(2.1) mmHg and 2.2 (2.4) mmHg respectively for the placebo group. Valsalva LVOT‑G were similar to baseline for both treatment arms 4 weeks after the discontinuation from treatment.
Cardiac biomarkers
In SEQUOIA-HCM, geometric mean NT-proBNP and troponin I at baseline were 734.7 pg/mL and 17.1 ng/L for patients in the aficamten group and 709.8 pg/mL and 16.6 ng/L in the placebo group. At week 24, the proportional change from based in NT-proBNP and troponin I were 0.19 and 0.58, respectively, for the aficamten group and 0.99 and 1.01, respectively, for the placebo group. NT-proBNP and troponin I were similar to baseline for both treatment arms 4 weeks after the discontinuation from treatment.
Cardiac electrophysiology
The results of a thorough QT study demonstrated a lack of QTc prolongation across the therapeutic concentration range of aficamten. At a single dose of 50 mg (similar exposure as 20 mg daily dosing to steady-state), the upper limits of the predicted placebo-corrected change from baseline in QT interval corrected by Fridericia (ΔΔQTcF) 90% confidence interval for aficamten were all < 10 msec.
Clinical efficacy and safety
The efficacy of aficamten was evaluated in SEQUOIA-HCM study, a phase 3, multicentre, randomised, double-blind, placebo-controlled study in 282 adults (142 aficamten, 140 placebo) with symptomatic NYHA class II and III oHCM, LVEF ≥ 60%, and resting and peak Valsalva LVOT‑G ≥ 30 and ≥ 50 mmHg at screening, respectively.
Patients with a known infiltrative or storage disorder causing cardiac hypertrophy such as Noonan syndrome, Fabry disease or amyloidosis were excluded.
Patients were randomised in a 1:1 ratio to receive either a starting dose of 5 mg of aficamten or placebo once daily for 24 weeks. Stratification factors included baseline use of beta blockers and cardiopulmonary exercise testing (CPET) ergometer (treadmill or cycle). At baseline, beta-blockers were used by 61.3% of patients, and non-dihydropyridine calcium channel blockers were used by 28.7% of participants. In addition, 12.8% of patients were taking disopyramide. Overall, 14.5% of patients were not taking any background medicinal product at baseline.
Overall, baseline demographics and disease characteristics were balanced between treatment groups. The study enrolled patients with a mean age of 59.1 years; (range 18 to 84 years), 59% male, 79% White, 19% Asian and 1% Black or African American. The mean, body mass index was 28.1 kg/m2, mean resting heart rate of 66 bpm and mean blood pressure of 125/74 mmHg. In SEQUOIA-HCM there were 57 patients aged 65 years and older. No patients had undergone prior septal reduction therapy (SRT). At baseline, 76% of the randomised patients were NYHA class II and 24% were NYHA class III. The median LVEF was 75.6%, the mean resting LVOT‑G was 55.1 mmHg, the mean Valsalva LVOT‑G was 83.1 mmHg, and the mean Kansas City Cardiomyopathy Questionnaire – Clinical Summary Score (KCCQ-CSS) was 74.7.
Patients were initiated on aficamten at a dose of 5 mg once daily. Doses were individually titrated at weeks 2, 4 and 6 if Valsalva LVOT‑G ≥ 30 mmHg and LVEF ≥ 55% in 5 mg intervals up to a maximum dose of 20 mg one daily. At week 24 in the aficamten group, 46% of patients were receiving a 20 mg dose, 35% were receiving a 15 mg dose, 15.3% were receiving a 10 mg dose and 3.6% were receiving a 5 mg dose.
Primary endpoint - peak oxygen uptake (pVO2)
In SEQUOIA-HCM study, the primary endpoint of change from baseline in pVO2 to week 24 was statistically significant and greater in the aficamten group compared with placebo, as shown in Table 5.
Secondary endpoints
The treatment effects of aficamten on health status, functional capacity, and LVOT obstruction were assessed by change in KCCQ-CSS, proportion of patients with ≥ 1 class improvement in NYHA functional class, change from baseline in Valsalva LVOT‑G, proportion of patients with Valsalva LVOT‑G ≤ 30 mmHg and duration of eligibility for septal reduction therapy (SRT). At week 24, patients receiving aficamten had greater improvement compared to the placebo group across all secondary points (Table 5).
| Table 5: Analysis of endpoints from SEQUOIA-HCM study |
| Endpoints | Aficamten N=142 | Placebo N=140 |
| Change from baseline in pVO2 by CPET |
| Baseline (mL/min/kg), mean (SD) | 18.4 (4.4) | 18.6 (4.5) |
| Week 24 |
| LS mean (SE) | 1.76 (0.25) | 0.02 (0.25) |
| LS mean difference vs. placebo (95% CI) | 1.74 (1.04, 2.44) |
| p-value | < 0.0001 |
| Change from baseline in KCCQ-CSS1 |
| Baseline, mean (SD) | 75.6 (18.4) | 73.7 (17.6) |
| Week 12, n (%) | 11.1 (0.9) | 4 (0.9) |
| Difference (95% CI) | 7 (4.5, 9.5) |
| p-value | < 0.0001 |
| Week 24, n (%) | 11.6 (1) | 4.3 (1) |
| Difference (95% CI) | 7.3 (4.6, 10.1) |
| p-value | < 0.0001 |
| Proportion of patients with improvement of ≥ 10 points in KCCQ-CSS1 |
| Week 12, n (%) | 63 (44.4) | 33 (23.6) |
| Difference (95% CI) | 20.8 (10, 31.6) |
| p-value | < 0.001 |
| Week 24, n (%) | 69 (48.6) | 38 (27.1) |
| Difference (95% CI) | 21.5 (10.6, 32.5) |
| p-value | < 0.001 |
| Proportion of patients who remained eligible for SRT4 |
| Baseline | N = 32 | N = 29 |
| Week 24, n (%) | 4 (12.5) | 14 (48.3) |
| Difference (95% CI) | OR: 0.16 (0.03, 0.61) Difference: -36.5 (-58.5, -14.5) |
| p-value | OR, p = 0.005 Difference, p = 0.002 |
| Duration of SRT eligibility1 |
| Days spent SRT-eligible during 24 weeks of treatment, n (%) | 35.3 (7.9) | 113.4 (8.1) |
| Difference (95% CI) | −78.1 (−99.8, −56.3) |
| p-value | < 0.0001 |
| Change from baseline in Valsalva LVOT‑G (mmHg)1 |
| Baseline, mean (SD) | 83 (32) | 83 (32.7) |
| Week 12, n (%) | -46 (2.4) | 2.6 (2.4) |
| Difference (95% CI) | -48 (-55, -42) |
| p-value | < 0.0001 |
| Week 24, n (%) | -48 (2.4) | 2.2 (2.4) |
| Difference (95% CI) | -50 (-57, -44) |
| p-value | < 0.0001 |
| Proportion of patients with Valsalva LVOT‑G < 30 (mmHg)4 |
| Week 12, n (%) | 74 (52.1) | 8 (5.7) |
| Difference (95% CI) | OR: 18 (7.8, 44.4) Difference: 46.4 (37.3, 55.5) |
| p-value | < 0.0001 |
| Week 24, n (%) | 70 (49.3) | 5 (3.6) |
| Difference (95% CI) | OR: 25.5 (10.1, 88.2) Difference: 45.7 (36.9, 54.5) |
| p-value | < 0.0001 |
| Proportion of patients with ≥ 1 NYHA class improvement4 |
| Week 12, n (%) | 69 (48.6) | 25 (17.9) |
| Difference (95% CI) | OR: 4.6 (2.6, 8.4) Difference: 30.8 (20.6, 41) |
| p-value | < 0.0001 |
| Week 24, n (%) | 83 (58.5) | 34 (24.3) |
| Difference (95% CI) | OR: 4.4 (2.6, 7.6) Difference: 34.2 (23.4, 45) |
| p-value | < 0.0001 |
| CPET: Cardiac Pulmonary Exercise Test; KCCQ CSS: Kansas City Cardiomyopathy Questionnaire – Clinical Summary Score; NYHA: New York Heart Association; LVOT‑G: left ventricular outflow tract gradient; SRT: septal reduction therapy 1 LS means (SE) and LS mean difference (95% CI) presented for continuous endpoints. 2 The KCCQ CSS measures patient-perceived physical limitations and symptoms associated with heart failure. The KCCQ CSS ranges from 0 to 100, with higher scores representing better health status. 3 NYHA includes Classes I to IV. 4 The number (percentage) of responders and rate difference (Diff) and common OR (exact 95% CI of the OR) are presented for binary endpoints. |
A range of demographic characteristics, baseline disease characteristics, and baseline concomitant medicinal products (e.g. use of beta blockers) were examined for their influence on outcomes. Results of the primary analysis favoured aficamten consistently across all subgroups.
The effect of aficamten on the left ventricular outflow tract gradient after the Valsalva maneuver was relatively rapid, with a LS mean difference between the groups of −20 mm Hg (95% CI, −27.3 to −13.3) after 2 weeks.
Paediatric population
The European Medicines Agency has deferred the obligation to submit the results of studies with MYQORZO in one or more subsets of the paediatric population in the treatment of hypertrophic cardiomyopathy (see section 4.2 for information on paediatric use).