Balaratnam, Ganesh

Background The phase 2 PIONEER‐HCM (Phase 2 Open‐label Pilot Study Evaluating Mavacamten in Subjects With Symptomatic Hypertrophic Cardiomyopathy and Left Ventricular Outflow Tract Obstruction) study showed that mavacamten improved left ventricular outflow tract gradients, exercise capacity, and symptoms in patients with obstructive hypertrophic cardiomyopathy (HCM), but the results of longer‐term treatment are less well described. We report interim results from the PIONEER‐OLE (PIONEER Open‐Label Extension) study, the longest‐term study of mavacamten in patients with symptomatic obstructive HCM. Methods and Results Patients who previously completed PIONEER‐HCM (n=20) were eligible to enroll in PIONEER‐OLE. Patients received oral mavacamten, 5 mg once daily (starting dose), with individualized dose titration at week 6. Evaluations included serial monitoring of safety, echocardiography, Kansas City Cardiomyopathy Questionnaire–Overall Summary Score, and serum NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide) levels. Thirteen patients enrolled and received mavacamten (median study duration at data cutoff, 201 weeks). Most patients (92.3%) received β‐blockers concomitantly. Treatment‐emergent adverse events were predominantly mild/moderate. One patient had an isolated reduction in left ventricular ejection fraction to 47%, which recovered and remained normal with continued treatment at a reduced dose. At week 180, mavacamten was associated with New York Heart Association class improvements from baseline (class II to I, n=9; class III to II, n=1; and unchanged, n=2), sustained reductions in left ventricular outflow tract gradients (mean [SD] change from baseline: resting, −50 [55] mm Hg; Valsalva, −70 [41] mm Hg), and serum NT‐proBNP levels (median [interquartile range] change from baseline: −498 [−2184 to −76] ng/L), and improved Kansas City Cardiomyopathy Questionnaire–Overall Summary Score (mean [SD] change from baseline: +17 [16]). Conclusions This long‐term analysis supports the continued safety and effectiveness of mavacamten for >3 years in obstructive HCM. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT03496168.

Abstract Background In a phase 2 PIONEER-HCM study, pts with symptomatic, obstructive hypertrophic cardiomyopathy (oHCM) showed improvement in left ventricular outflow tract (LVOT) obstruction, exercise capacity, and symptoms after 12 wk of treatment with the novel myosin modulator, mavacamten (Mava). Purpose To examine the long-term safety and effectiveness of Mava in PIONEER-OLE study Methods PIONEER-OLE (NCT03496168) is an ongoing 2-y multicenter study for adults with symptomatic oHCM who completed PIONEER-HCM (NCT02842242). The starting dose of Mava is 5 mg/d with titration at wk 6 to an individualized therapeutic dose (5, 10, or 15 mg). Evaluations are at wk 4, 6, 8, 12 and every 12 wk thereafter to monitor LV ejection fraction (LVEF), LVOT gradient, New York Heart Association (NYHA) class, NT-proBNP, drug concentration, and safety. Results 13 pts (mean age, 57.8 y; 9 male; 12 on beta-blockers) were enrolled. Mean baseline LVOT obstruction and LVEF, and wk 12 changes from baseline, were similar to those in PIONEER-HCM (Table). Mava significantly reduced resting and provoked LVOT gradients and NT-proBNP at wk 12 and 24 compared with baseline (P<0.004). Of 10 pts who reached wk 24, 8 reported improvement in NYHA class (1 improved Class III to II; 7 improved Class II to I), and 2 pts remained Class II. Mava has been well tolerated up to 40 wk; 31 adverse events (AEs; 22 mild, 5 moderate) were reported in 8 pts; 1 pt had 3 severe and 1 serious AE (cholangiocarcinoma); all AEs were unrelated to study drug. Results from PIONEER-OLE Parameter PIONEER-HCMa PIONEER-OLE Baseline Wk 12 Baselineb Wk 12 Change at Wk 12 Wilcoxon Signed Wk 24 Change at Wk 24 Wilcoxon Signed Mean ± SD Mean ± SD Mean ± SD Mean ± SD Mean ± SD Rank Mean ± SD Mean ± SD Rank (n=13) (n=13) (n=13)c (n=12)c (n=12)c P value (n=10)c (n=10)c P value LVOT Rest gradient, mmHg 69.7±53.9 27.8±31.3 67.3±42.8 12.0±5.4 −57.9±43.2 0.0005 10.5±4.8 −66.6±42.4 0.0020 LVOT Valsalva gradient, mmHg 93.7±55.6 36.8±37.5 89.9±30.7 (n=12) 23.6±20.0 −66.4±35.3 (n=11) 0.0020 21.1±11.5 −67.3±33.5 (n=9) 0.0039 LVEF, % 73.0±5.6 64.6±10.5 72.0±4.9 67.6±7.2 −4.4±5.5 0.0269 68.2±6.5 −3.2±3.3 0.0195 NT-proBNP, pg/mL 1601.3±2782 (n=12) 684±980 1836±2886 181±211 −1759±2789 0.0005 170±225 −2128±3104 0.0039 Data extraction date January 24, 2019. aCombined results shown for pts from PIONEER-HCM originally in cohort A (n=5) and cohort B (n=8). bBaseline in PIONEER-OLE occurred 6–18 months after completion of PIONEER-HCM. cNumber of pts with data available for analysis, unless otherwise specified. Conclusion Despite management with current therapies, pts enrolled in PIONEER-OLE with similar levels of obstruction and hypercontractility as in PIONEER-HCM. In this longest observation period, Mava significantly reduced obstruction (LVOT gradient) in pts with oHCM beyond standard HCM therapy, while maintaining normal LVEF and improving symptoms. Acknowledgement/Funding MyoKardia