Clinical Pharmacology for Camzyos
Mechanism Of Action
Mavacamten is an allosteric and reversible inhibitor selective for cardiac myosin. Mavacamten modulates the number of myosin heads that can enter “on actin” (powergenerating) states, thus reducing the probability of force-producing (systolic) and residual (diastolic) cross-bridge formation. Excess myosin actin cross-bridge formation and dysregulation of the super-relaxed state are mechanistic hallmarks of HCM. Mavacamten shifts the overall myosin population towards an energy-sparing, recruitable, super-relaxed state. In HCM patients, myosin inhibition with mavacamten reduces dynamic LVOT obstruction and improves cardiac filling pressures.
Pharmacodynamics
Left Ventricular Ejection Fraction And Left Ventricular Outflow Tract Obstruction
In the EXPLORER-HCM trial, patients achieved reductions in mean resting and provoked (Valsalva) LVOT gradient by Week 4 which were sustained throughout the 30-week trial. At Week 30, the mean (SD) changes from baseline in resting and Valsalva LVOT gradients were -39 (29) mmHg and -49 (34) mmHg, respectively, for the CAMZYOS group and -6 (28) mmHg and -12 (31) mmHg, respectively, for the placebo group. The reductions in Valsalva LVOT gradient were accompanied by decreases in LVEF, generally within the normal range. Eight weeks after discontinuation of CAMZYOS, mean LVEF and Valsalva LVOT gradients were similar to baseline.
Cardiac Structure
In EXPLORER-HCM, echocardiographic measurements of cardiac structure showed a mean (SD) reduction from baseline at Week 30 in left ventricular mass index (LVMI) in the mavacamten group (-7.4 [17.8] g/m²) versus an increase in LVMI in the placebo group (8.9 [15.3] g/m²). There was also a mean (SD) reduction from baseline in left atrial volume index (LAVI) in the mavacamten group (-7.5 [7.8] mL/m²) versus no change in the placebo group (-0.1 [8.7] mL/m²). The clinical significance of these findings is unknown.
Cardiac Biomarkers
In the EXPLORER-HCM trial [see Clinical Studies], reductions in a biomarker of cardiac wall stress, NT-proBNP, were observed by Week 4 and sustained through the end of treatment. At Week 30 compared with baseline, the reduction in NT-proBNP after mavacamten treatment was 80% greater than for placebo (proportion of geometric mean ratio between the two groups, 0.20 [95% CI: 0.17, 0.24]).
In the VALOR-HCM trial [see Clinical Studies], a reduction in NT-proBNP was observed by Week 8 and sustained throughout treatment. At Week 16 compared with baseline, the reduction in NT-proBNP after mavacamten treatment was 67% greater than for placebo (proportion of geometric mean ratio between the two groups, 0.33 [95% CI: 0.27, 0.42]). At Week 16 compared with baseline, a reduction in cardiac troponin I after mavacamten treatment was 47% greater than for placebo (proportion of geometric mean ratio between the two groups, 0.53 [95% CI: 0.41, 0.70]).
The clinical significance of the NT-proBNP and troponin findings is unknown.
Cardiac Electrophysiology
In healthy volunteers receiving multiple doses of CAMZYOS, a concentration-dependent increase in the QTc interval was observed at doses up to 25 mg once daily. No acute QTc changes have been observed at similar exposures during single-dose studies. The mechanism of the QT prolongation effect is not known.
A meta-analysis across clinical studies in HCM patients does not suggest clinically relevant increases in the QTc interval in the therapeutic exposure range. In HCM, the QT interval may be intrinsically prolonged due to the underlying disease, in association with ventricular pacing, or in association with drugs with potential for QT prolongation commonly used in the HCM population. The effect of coadministration of CAMZYOS with other QT-prolonging drugs or in patients with potassium channel variants resulting in a long QT interval have not been characterized.
Pharmacokinetics
Mavacamten exposure increases dose proportionally following multiple once-daily doses of 1 mg to 15 mg. At the same dose level of CAMZYOS, 170% higher exposures of mavacamten are observed in patients with HCM compared to healthy subjects. Mavacamten accumulation is approximately 100% for Cmax and approximately 600% for AUC in CYP2C19 normal metabolizers (NMs). The accumulation is dependent upon the CYP2C19 metabolism status with the largest accumulation occurring in CYP2C19 poor metabolizers (PMs). At steady-state, the peak-to-trough mavacamten plasma concentration ratio with once daily dosing is approximately 1.5.
Absorption
Mavacamten has an estimated oral bioavailability of at least 85% and median time to maximum concentration (Tmax) of 1 to 2 hours.
Effect Of Food
No clinically significant differences in mavacamten AUC were observed following its administration with a high fat meal.
Distribution
Plasma protein binding of mavacamten is between 97 and 98%.
Elimination
Mavacamten has a variable terminal t½ that depends on CYP2C19 metabolic status. Mavacamten terminal half-life is 6 to 9 days in CYP2C19 normal metabolizers (NMs), which is prolonged in CYP2C19 poor metabolizers (PMs) to 23 days.
Metabolism
Mavacamten is extensively metabolized, primarily through CYP2C19 (74%), CYP3A4 (18%), and CYP2C9 (8%).
Excretion
Following a single 25-mg dose of radiolabeled mavacamten, 7% of the dose was recovered in feces (1% unchanged) and 85% in urine (3% unchanged).
Specific Populations
No clinically significant differences in the pharmacokinetics of mavacamten were observed based on age (range: 18-82 years), sex, race, ethnicity, or mild (eGFR: 60 to 89 mL/min/1.73 m²) to moderate (eGFR: 30 to 59 mL/min/1.73 m²) renal impairment. The effects of severe (eGFR: 15 to 30 mL/min/1.73 m²) renal impairment and kidney failure (eGFR: <15 mL/min/1.73 m²; including patients on dialysis) are unknown.
Hepatic Impairment
Mavacamten exposures (AUC) increased up to 220% in patients with mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment. The effect of severe (Child-Pugh C) hepatic impairment is unknown.
Drug Interactions
Clinical Studies And Model-Informed Approaches
Weak CYP2C19 Inhibitors
Concomitant use of mavacamten (15 mg) with omeprazole (20 mg) once daily increased mavacamten AUCinf by 48% with no effect on Cmax in healthy CYP2C19 NMs and rapid metabolizers (RMs; e.g., *1/*17).
Moderate CYP3A4 Inhibitors
Concomitant use of mavacamten (25 mg) with verapamil sustained release (240 mg) increased mavacamten AUCinf by 16% and Cmax by 52% in intermediate metabolizers (IMs; e.g., *1/*2, *1/*3, *2/*17, *3/*17) and NMs of CYP2C19. Concomitant use of mavacamten with diltiazem in CYP2C19 PMs is predicted to increase mavacamten AUC0-24h and Cmax up to 55% and 42%, respectively.
Strong CYP3A4 Inhibitors
Concomitant use of mavacamten (15 mg) with ketoconazole 400 mg once daily in CYP2C19 poor metabolizers is predicted to increase mavacamten AUC0-24 and Cmax up to 130% and 90%, respectively.
Strong CYP2C19 And CYP3A4 Inducers
Concomitant use of mavacamten (a single 15-mg dose) with a strong CYP2C19 and CYP3A4 inducer (rifampin 600-mg daily dose) is predicted to decrease mavacamten AUC0-inf and Cmax by 87% and 22%, respectively, in CYP2C19 NMs, and by 69% and 4%, respectively, in CYP2C19 PMs.
CYP3A4 Substrates
Concomitant use of a 16-day course of mavacamten (25 mg on Days 1 and 2, followed by 15 mg for 14 days) decreased AUCinf and Cmax of midazolam by 13% and 7%, respectively, in healthy subjects. Following coadministration of mavacamten once daily in HCM patients at the upper end of the therapeutic range, midazolam AUCinf and Cmax are predicted to decrease up to 45% and 24%, respectively.
Certain Combined Oral Contraceptives
No clinically significant differences in ethinyl estradiol and norethindrone exposure were observed in healthy female subjects with CYP2C19 NM phenotype following concomitant use of a combined oral contraceptive containing ethinyl estradiol and norethindrone with a 17-day course of mavacamten (25 mg on days 1 and 2, followed by 15 mg for 15 days). The impact of mavacamten on oral contraceptives containing other progestins is unknown.
CYP2C8 Substrates
Concomitant use of mavacamten once daily in HCM patients is predicted to decrease AUC and Cmax of repaglinide, a CYP2C8 and CYP3A substrate, by up to 27% and 19%, respectively, depending on the dose of mavacamten and CYP2C19 phenotype.
CYP2C9 Substrates
Concomitant use of mavacamten once daily in HCM patients is predicted to decrease AUC and Cmax of tolbutamide, a CYP2C9 substrate, by up to 54% and 23%, respectively, depending on the dose of mavacamten and CYP2C19 phenotype.
CYP2C19 Substrates
Concomitant use of mavacamten once daily in HCM patients is predicted to decrease AUC and Cmax of omeprazole, a CYP2C19 substrate, by up to 48% and 17%, respectively, depending on the dose of mavacamten and CYP2C19 phenotype.
Activated Charcoal
Mavacamten AUC0-72h and AUC0-infinity was reduced by 14% and 34%, respectively, following administration of 50 g activated charcoal with sorbitol 2 hours after ingestion of a single mavacamten 15 mg dose. Administration of activated charcoal 6 hours after the mavacamten dose had minimal effect on mavacamten exposure.
In Vitro Studies
CYP Enzymes
Mavacamten does not inhibit CYP1A2, CYP2B6, CYP2C8, CYP2D6, CYP2C9, CYP2C19, or CYP3A4. Mavacamten is a CYP2B6 inducer.
Transporter Systems
Mavacamten does not inhibit P-gp, BCRP, BSEP, MATE1, MATE2-K, organic anion transporting polypeptides (OATPs), organic cation transporters (OCTs), or organic anion transporters (OATs).
Pharmacogenomics
Mavacamten AUCinf increased by 241% and Cmax increased by 47% in CYP2C19 poor metabolizers (PMs) compared to normal metabolizers (NMs) following a single dose of 15 mg mavacamten. Mean half-life is prolonged in CYP2C19 PMs compared to NMs (23 days vs. 6 to 9 days, respectively).
Polymorphic CYP2C19 is the main enzyme involved in the metabolism of CAMZYOS. An individual carrying two normal function alleles is a NM (e.g., *1/*1). An individual carrying two no function alleles is a PM (e.g., *2/*2, *2/*3, *3/*3).
The prevalence of CYP2C19 poor metabolizers differs depending on ancestry. Approximately 2% of individuals of European ancestry and 4% of individuals of African ancestry are PMs; the prevalence of PMs is higher in Asian populations (e.g., approximately 13% of East Asians).
Clinical Studies
EXPLORER-HCM
The efficacy of CAMZYOS was evaluated in EXPLORER-HCM (NCT-03470545) a Phase 3, double-blind, randomized, placebo-controlled, multicenter, international, parallel-group trial in 251 adults with symptomatic NYHA class II and III obstructive HCM, LVEF ≥55%, and LVOT peak gradient ≥50 mmHg at rest or with provocation.
Patients on dual therapy with beta blocker and calcium channel blocker treatment or monotherapy with disopyramide or ranolazine were excluded. Patients with a known infiltrative or storage disorder causing cardiac hypertrophy that mimicked obstructive HCM, such as Fabry disease, amyloidosis, or Noonan syndrome with left ventricular hypertrophy, were also excluded.
Patients were randomized in a 1:1 ratio to receive either a starting dose of 5 mg of CAMZYOS or placebo once daily for 30 weeks. Treatment assignment was stratified by baseline NYHA functional class, baseline use of beta blockers, and type of ergometer (treadmill or exercise bicycle).
Groups were well matched with respect to age (mean 59 years), BMI (mean 30 kg/m²), heart rate (mean 62 bpm), blood pressure (mean 128/76 mmHg), and race (90% Caucasian). Males comprised 54% of the CAMZYOS group and 65% of the placebo group.
At baseline, approximately 73% of the randomized patients were NYHA class II and 27% were NYHA class III. The mean LVEF was 74%, and the mean Valsalva LVOT gradient was 73 mmHg. About 10% had prior septal reduction therapy, 75% were on beta blockers, 17% were on calcium channel blockers, and 14% had a history of atrial fibrillation.
All patients were initiated on CAMZYOS 5 mg (or matching placebo) once daily, and the dose was periodically adjusted to optimize patient response (decrease in LVOT gradient with Valsalva maneuver) and maintain LVEF ≥50%. The dose was also informed by plasma concentrations of CAMZYOS.
In the CAMZYOS group, at the end of treatment, 49% of patients were receiving the 5-mg dose, 33% were receiving the 10-mg dose, and 11% were receiving the 15-mg dose. Three patients temporarily interrupted their dose due to LVEF <50%, of whom two resumed treatment at the same dose and one had the dose reduced from 10 mg to 5 mg.
Primary Endpoint
The primary composite functional endpoint, assessed at 30 weeks, was defined as the proportion of patients who achieved either improvement of peak oxygen consumption (pVO2) by ≥1.5 mL/kg/min plus improvement in NYHA class by at least 1 or improvement of pVO2 by ≥3.0 mL/kg/min plus no worsening in NYHA class.
A greater proportion of patients met the primary endpoint at Week 30 in the CAMZYOS group compared to the placebo group (37% vs. 17%, respectively, p=0.0005; see Table 2).
Table 2: Primary Endpoint at 30 Weeks
|
CAMZYOS n (%)
N = 123 |
Placebo n (%)
N=128 |
Difference (95% CI) |
p-value |
| Total responders |
45 (37%) |
22 (17%) |
19% (9, 30) |
0.0005 |
| Change from baseline pVO2 ≥1.5 mL/kg/min and decreased NYHA |
41 (33%) |
18 (14%) |
19% (9, 30) |
|
| Change from baseline pVO2 ≥3 mL/kg/min and NYHA not increased |
29 (23%) |
14 (11%) |
13% (3, 22) |
|
A range of demographic characteristics, baseline disease characteristics, and baseline concomitant medications were examined for their influence on outcomes. Results of the primary analysis consistently favored CAMZYOS across all subgroups analyzed (Figure 4).
Figure 4: Subgroup Analysis of the Primary Composite Functional Endpoint
The dashed vertical line represents the overall treatment effect and the solid vertical line (no effect) indicates no difference between treatment groups.
Note: The figure above presents effects in various subgroups, all of which are baseline characteristics. The 95% confidence limits that are shown do not take into account the number of comparisons made and may not reflect the effect of a particular factor after adjustment for all other factors. Apparent homogeneity or heterogeneity among groups should not be over interpreted.
Although the benefit of mavacamten was smaller in patients on background beta blocker therapy compared to those who were not (attenuated improvement in pVO2), analyses of other secondary endpoints (symptoms, LVOT gradient) suggest that patients might benefit from mavacamten treatment regardless of beta blocker use.
Secondary Endpoints
The treatment effects of CAMZYOS on LVOT obstruction, functional capacity, and health status were assessed by change from baseline through Week 30 in post-exercise LVOT peak gradient, change in pVO2, proportion of patients with improvement in NYHA class, Kansas City Cardiomyopathy Questionnaire-23 (KCCQ-23) Clinical Summary Score (CSS), and Hypertrophic Cardiomyopathy Symptom Questionnaire (HCMSQ) Shortness of Breath (SoB) domain score. At Week 30, patients receiving CAMZYOS had greater improvement compared to the placebo group across all secondary endpoints (Table 3, Figure 5, Figure 6, Table 4, and Figures 7-10).
Table 3: Change from Baseline to Week 30 in Post-Exercise LVOT Gradient, pVO2, and NYHA Class
|
CAMZYOS N=123 |
Placebo N=128 |
Difference (95% CI) |
p-value |
| Post-Exercise LVOT gradient (mmHg), mean (SD) |
-47 (40) |
-10 (30) |
-35
(-43, -28) |
<0.0001 |
| pVO2 (mL/kg/min), mean (SD) |
1.4 (3.1) |
-0.1 (3.0) |
1.4
(0.6, 2.1) |
<0.0006 |
| Number (%) with NYHA Class improved ≥1 |
80 (65%) |
40 (31%) |
34%
(22%, 45%) |
<0.0001 |
Figure 5: Cumulative Distribution of Change from Baseline to Week 30 in LVOT Peak Gradient
Figure 6: Cumulative Distribution of Change from Baseline to Week 30 in pVO2
Table 4: Change from Baseline to Week 30 in KCCQ-23 CSS and HCMSQ SoB Domain
|
Baseline, Mean (SD) |
Change from Baseline to Week 30, Mean (SD) |
Difference, LS Mean (95%CI) and p-value |
| CAMZYOS |
Placebo |
CAMZYOS |
Placebo |
| KCCQ-23 CSS† |
n=99
71 (16) |
n=97
71 (19) |
14 (14) |
4 (14) |
9 (5, 13) p<0.0001 |
| KCCQ-23 TSS |
71 (17) |
69 (22) |
12 (15) |
5 (16) |
|
| KCCQ-23 PL |
70 (18) |
72 (19) |
15 (17) |
4 (15) |
|
| HCMSQ SoB‡ |
n=108 5 (3) |
n=109 5 (3) |
-3 (3) |
-1 (2) |
-2 (-2,-1) p<0.0001 |
† The KCCQ-23 CSS is derived from the Total Symptom Score (TSS) and the Physical Limitations (PL) score of the KCCQ-23. The CSS ranges from 0 to 100 with higher scores representing less severe symptoms and/or physical limitations.
‡ The HCMSQ SoB domain score measures the frequency and severity of shortness of breath. The HCMSQ SoB domain score ranges from 0 to 18 with lower scores representing less shortness of breath.
Missing data were not imputed to summarize the baseline and change from baseline to Week 30 values. Difference in mean change from baseline between treatment groups wasestimated using a mixed model for repeated measures. |
Figure 7 shows the time course for changes in KCCQ-23 CSS. Figure 8 shows the distribution of changes from baseline to Week 30 for KCCQ-23 CSS.
Figure 7: KCCQ-23 Clinical Summary Score: Mean Change from Baseline Over Time
Figure 8: KCCQ-23 Clinical Summary Score: Cumulative Distribution of Change from Baseline to Week 30
Figure 9 shows the time course for changes in HCMSQ SoB. Figure 10 shows the distribution of changes from baseline to Week 30 for HCMSQ SoB.
Figure 9: HCMSQ Shortness of Breath Domain: Mean Change from Baseline Over Time
Figure 10: HCMSQ Shortness of Breath Domain: Cumulative Distribution of Change from Baseline to Week 30
VALOR-HCM
The efficacy of CAMZYOS was evaluated in VALOR-HCM, a Phase 3, double-blind, randomized, 16-week placebo-controlled trial in 112 patients (mean age of 60 years; 51% men; 93% ≥NYHA class III) randomized 1:1 to receive treatment with CAMZYOS or placebo. At baseline, all patients had symptomatic obstructive HCM and were SRT eligible.
Patients with severely symptomatic drug-refractory obstructive HCM (including 33% on any combination of beta-blocker, calcium channel blocker and/or disopyramide; 20% were on disopyramide alone or in combination with other treatment), and NYHA class III/IV or class II with exertional syncope or near syncope, were included in the study. Patients were required to have LVOT peak gradient ≥50 mmHg at rest or with provocation, and LVEF ≥60%. Patients must have been referred or under active consideration within the past 12 months for SRT and actively considering scheduling the procedure.
Patients received CAMZYOS (2.5 mg, 5 mg, 10 mg, or 15 mg) or a placebo capsule once daily for 16 weeks. Dose adjustment was based on clinical echocardiogram parameters.
Primary Endpoint
CAMZYOS was shown to be superior to placebo in reducing the proportion of patients who met the primary endpoint (the composite of patient decision to proceed with SRT prior to or at Week 16 or met SRT eligibility (LVOT gradient of ≥50 mmHg and NYHA class III-IV, or class II with exertional syncope or near syncope) at Week 16 (18% vs. 77%, respectively, p<0.0001; see Table 5).
Table 5: Primary Endpoint at 16 Weeks
|
CAMZYOS n (%)
n = 56 |
Placebo n (%)
n = 56 |
Treatment difference (95% CI) |
p-value |
| Primary efficacy composite endpoint |
10 (18) |
43 (77) |
59% (44%, 74%) |
<0.0001 |
| Patient decision to proceed with SRT |
2 (3.6) |
2 (3.6) |
|
|
| SRT-eligible based on guideline criteria* |
8 (14) |
39 (70) |
|
|
| SRT status not evaluable (imputed as meeting guideline criteria) |
0 |
2 (3.6) |
|
|
| *NYHA Class III or IV, or Class II with exertion induced syncope or near syncope and dynamic LVOT gradient at rest or with provocation (i.e., Valsalva or exercise) ≥50 mmHg. |
Secondary Endpoints
The treatment effects of CAMZYOS on LVOT obstruction, functional capacity, and health status were assessed by change from baseline through Week 16 in post-exercise LVOT gradient, proportion of patients with improvement in NYHA class, and KCCQ-23 CSS.
Table 6: Change from Baseline to Week 16 in Secondary Endpoints
|
CAMZYOS
n = 56 |
Placebo
n=56 |
Difference (95% CI) |
p-value |
| Post-Exercise LVOT gradient (mmHg), mean (SD) |
-39 (37) |
-2 (29) |
-38 (-49, -28) |
<0.0001 |
| Number (%) with NYHA Class improved ≥1 |
35 (63%) |
12 (21%) |
41% (25%, 58%) |
<0.0001 |
| KCCQ-23 CSS†, mean (SD) |
10 (16) |
2 (12) |
9 (5, 14) |
<0.0001 |
| KCCQ-23 TSS, mean (SD) |
10 (16) |
2 (14) |
10 (5, 15) |
|
| KCCQ-23 PL, mean (SD) |
10 (19) |
2 (17) |
10 (5, 16) |
|
| † The KCCQ-23 CSS is derived from the Total Symptom Score (TSS) and the Physical Limitations (PL) score of the KCCQ-23. The CSS ranges from 0 to 100 with higher scores representing less severe symptoms and/or physical limitations. |
Figure 11 shows the time course for changes in KCCQ-23 CSS. Figure 12 shows the distribution of changes from baseline to Week 16 for KCCQ-23 CSS.
Figure 11: KCCQ-23 Clinical Summary Score: Mean Change from Baseline Over Time
Figure 12: KCCQ-23 Clinical Summary Score: Cumulative Distribution of Change from Baseline to Week 16
The figure displays the cumulative percentage of patients achieving a certain level of response.