Clinical Pharmacology for Lumason
Mechanism Of Action
Within the blood, the acoustic impedance of Lumason microspheres is lower than that of the surrounding non-aqueous tissue. Therefore, an ultrasound beam is reflected from the interface between the microspheres and the surrounding tissue. The reflected ultrasound signal provides a visual image that shows a contrast between the blood and the surrounding tissues.
For ultrasonography of the urinary tract in pediatric patients, the intravesically administered Lumason microspheres increase signal intensity of fluids within the urethra, bladder, ureters, and renal pelvis.
Pharmacodynamics
Lumason provides useful echocardiographic signal intensity for two minutes after intravenous injection. Lumason microspheres are destroyed and contrast enhancement decreases as the mechanical index increases (values of 0.8 or less are recommended).
For ultrasonography of the liver, Lumason provides dynamic patterns of differential signal intensity enhancement between focal liver lesions and liver parenchyma during the arterial, portal venous, and late phase of signal intensity enhancement of the microvasculature.
In ultrasonography of the urinary tract, Lumason facilitates the detection of reflux of fluid from the bladder into the ureters.
Pulmonary Hemodynamic Effects
The effect of Lumason on pulmonary hemodynamics was studied in a prospective, open-label study of 36 patients scheduled for right heart catheterization, including 18 with mean pulmonary arterial pressure (MPAP) > 25 mmHg and 18 with MPAP ≤ 25 mmHg. No clinically important pulmonary hemodynamic changes were observed. This study did not assess the effect of Lumason on visualization of cardiac or pulmonary structures.
Pharmacokinetics
The pharmacokinetic of the SF6 gas component of Lumason was evaluated in 12 healthy adult subjects. After intravenous bolus injections of 0.03 mL/kg and 0.3 mL/kg of Lumason, corresponding to approximately 1 and 10 times the recommended doses, concentrations of SF6 in blood peaked within 1 to 2 minutes for both doses. The terminal half-life of SF6 in blood was approximately 10 minutes for the 0.3 mL/kg dose. The area-under-the-curve of SF6 was dose-proportional over the dose range studied.
Distribution
In a study of healthy subjects, the mean values for the apparent steady-state volume of distribution of SF6 following intravenous administration, were 341 mcL and 710 mcL for Lumason doses of 0.03 mL/kg and 0.3 mL/kg, respectively. Preferential distribution to the lung is likely responsible for these values.
Elimination
Following intravenous administration, the SF6 component of Lumason is eliminated via the lungs. In a clinical study that examined SF6 elimination twenty minutes following Lumason injection, the mean cumulative recovery of SF6 in expired air was 82 ± 20% (SD) at the 0.03 mL/kg dose and 88 ± 26% (SD) at the 0.3 mL/kg dose.
SF6 undergoes first pass elimination within the pulmonary circulation; approximately 40% to 50% of the SF6 content was eliminated in the expired air during the first minute following Lumason injection.
Metabolism
SF6 undergoes little or no biotransformation; following intravenous administration, 88% of an administered dose is recovered unchanged in expired air.
Pharmacokinetics In Specific Populations
Pulmonary Impairment
In a study of patients with pulmonary impairment, blood concentrations of SF6 peaked at 1 to 4 minutes following intravenous Lumason administration. The cumulative recovery of SF6 in expired air was 102 ± 18% (mean ± standard deviation), and the terminal half-life of SF6 in blood was similar to that measured in healthy subjects.
Clinical Studies
Echocardiography
Adults
A total of 191 patients with suspected cardiac disease and suboptimal non-contrast echocardiography received Lumason in three multi-center controlled clinical trials (76 patients in Study A, 62 patients in Study B, and 53 patients in Study C). Among these patients, there were 127 men and 64 women. The mean age was 59 years (range 22 to 96 years). The racial and ethnic representations were 79% White, 16% Black, 4% Hispanic, < 1% Asian, and < 1% other racial or ethnic groups. The mean weight was 204 lbs (range 92 to 405 lbs). Approximately 20% of the patients had a chronic pulmonary disorder and 30% had a history of heart failure. Of the 106 patients for whom a New York Heart Association (NYHA) classification of heart failure was assigned, 49% were Class I, 33% were Class II, and 18% were Class III. Patients with NYHA Class IV heart failure were not included in these studies.
In Studies A and B, each patient received four intravenous bolus injections of Lumason (0.5, 1, 2, and 4 mL), in randomized order. In Study C, each patient received two doses of Lumason (1 mL and 2 mL) in randomized order. All three studies assessed endocardial border delineation and left ventricular opacification. For each patient in each study, echocardiography with Lumason was compared to non-contrast (baseline) echocardiography. A recording of 2D echocardiography was obtained from 30 seconds prior to each injection to at least 15 minutes after dosing or until the disappearance of the contrast effect, whichever was longer. Contrast and non-contrast echocardiographic images for each patient were evaluated by two independent reviewers, who were blinded to clinical information and the Lumason dose. Evaluation of left ventricular endocardial border consisted of segment based assessment involving six endocardial segments and using two apical views (2-and 4-chamber views).
Endocardial Border Delineation and Duration of Useful Contrast Effect
In all three studies, administration of Lumason improved left ventricular endocardial border delineation. The majority of the patients who received a 2.0 mL dose of Lumason had improvement in endocardial border delineation manifested as visualization of at least two additional endocardial border segments. Table 3 demonstrates the improvement in endocardial border delineation following Lumason administration as a reduction in percentage of patients with inadequate border delineation in at least one pair of adjacent segments (combined 2-chamber and 4-chamber view). The results are shown by reader.
Table 3. Reduction in Percentage of Patients with Inadequate BorderDelineation
| Reader |
Study A
N = 76 |
Study B
N = 62 |
Study C
N = 53 |
| Non-contrast |
Lumason |
Non-contrast |
Lumason |
Non-contrast |
Lumason |
| A |
60 (79%) |
22 (33%) |
31 (50%) |
12 (19%) |
12 (23%) |
10 (19%) |
| B |
62 (82%) |
29 (37%) |
54 (87%) |
6 (10%) |
45 (85%) |
20 (38%) |
Following the first appearance of contrast within the left ventricle the mean duration of useful contrast effect ranged from 1.7 to 3.1 minutes.
Left Ventricular Opacification
In all three studies, complete left ventricular opacification was observed in 52% to 80% of the patients following administration of a 2.0-mL dose of Lumason. The studies did not sufficiently assess the effect of Lumason upon measures of left ventricular ejection fraction and wall motion.
Pediatric Patients
Twelve pediatric patients 9 to 17 years of age with suspected cardiac disease and suboptimal non-contrast echocardiography received Lumason in one prospective multi-center clinical trial. Patients received Lumason at a dose of 0.03 mL/kg (mean 1.83 mL). There were 7 female, 10 white, and 2 black patients.
For both the non-contrast and contrast-enhanced images, standard apical 4-, 2-, and 3chamber views with harmonic imaging were acquired. Contrast and non-contrast images for each patient were evaluated by three independent reviewers, who were blinded to clinical information.
Endocardial Border Delineation
Evaluation of left ventricular endocardial border delineation consisted of segment-based assessment of the left ventricle divided into 17 endocardial segments. The delineation of each segment’s endocardial border was rated as inadequate, sufficient, or good. An exam was considered suboptimal if any of the patient’s apical views had 2 or more adjacent segments with inadequate delineation scores.
The majority of screened patients had adequate delineation of the left ventricular endocardial border without administration of contrast. The number of patients with inadequate left ventricular endocardial border delineation without contrast and after Lumason are shown for the 12 patients, by reader, in Table 4.
Table 4. Number of Pediatric Patients with Inadequate Border Delineation withand without Lumason
|
Reader A |
Reader B |
Reader C |
| Non-contrast |
12/12 |
11/11b |
12/12 |
| Lumason |
1/11a |
0/9bb |
0/11c |
a Reader A had missing segment data with contrast echocardiography for one patient;
b Reader B had missing segment data with non-contrast echocardiography for one patient;
bb Reader B had missing segment data with contrast echocardiography for three patients;
c Reader C had missing segment data with contrast echocardiography for one patient |
Left Ventricular Opacification
Complete left ventricular opacification was observed in all the patients by all 3 readers following administration of Lumason.
Ultrasonography Of The Liver
Adults
A total of 499 patients with at least 1 focal liver lesion requiring characterization were evaluated in two studies (259 patients in Study A, 240 patients in Study B). Among these patients, there were 259 men and 240 women. The mean age was 56 years (range 19 to 93 years). The racial and ethnic representations were 74% White, 11% Black, 9% Hispanic, 5% Asian, and 1% other racial or ethnic groups. The mean weight was 80 kg (range 44 to 173 kg).
In both studies, prior to Lumason administration, gray scale and Doppler (color or power imaging) ultrasound examinations of the target lesion were performed using commercially available ultrasound equipment and using standard techniques. Each patient received an intravenous injection of 2.4 mL of Lumason (up to 2 injections were allowed, 91% patients received 1 injection). Following Lumason administration, ultrasound examination of the target lesion was carried out using contrast-specific imaging modes operating at MI ≤ 0.4. The probe was positioned to provide optimal visualization over the target lesion and was kept in the same position for at least 180 seconds.
Truth standard included: histology/surgery, contrast CT, contrast MRI, and/or 6 month follow-up.
For each study, the interpretation of images was conducted by three independent readers who were blinded to clinical data. Lesions were characterized as malignant or benign. Separate blinded readers assessed the truth standard images. Results of both studies demonstrated an improvement in characterization of focal liver lesions using Lumason ultrasound compared to non-contrast ultrasound images. Table 5 summarizes the efficacy results by reader.
Table 5. Diagnostic Performance of Lumason Ultrasound for Characterization of Focal Liver Lesions
| Study A: |
|
Sensitivity (patients with malignant lesions)
N=119 |
Specificity (patients with benign lesions)
N=140 |
| Lumason % |
Non-contrast % |
Difference
(95% CI) |
Lumason % |
Non-contrast % |
Difference
(95% CI) |
| Reader 1 |
87* |
49 |
38 (30, 54) |
71 |
63 |
8 (-4, 21) |
| Reader 2 |
76* |
35 |
41 (29, 52) |
83* |
54 |
29 (21, 44) |
| Reader 3 |
92* |
16 |
76 (67, 84) |
73* |
22 |
51 (40, 61) |
| Study B: |
|
Sensitivity (patients with malignant lesions)
N=124 |
Specificity (patients with benign lesions)
N=116 |
| Lumason % |
Non-contrast % |
Difference
(95% CI) |
Lumason % |
Non-contrast % |
Difference
(95% CI) |
| Reader 4 |
65 |
53 |
12 (-1, 23) |
72* |
24 |
48 (35, 58) |
| Reader 5 |
61* |
41 |
20 (7, 32) |
67* |
7 |
60 (50, 70) |
| Reader 6 |
47 |
66 |
-19 (-31, -7) |
88* |
59 |
29 (18, 40) |
| * Statistically significant improvement from non-contrast (p<0.05 based on McNemar’s test) |
Pediatric Patients
In one published study, 44 patients with an indeterminate focal liver lesion (23 males, 21 females, age range: 4-18 years, median 11.5 years) were evaluated after intravenous bolus administration of 1.2 to 2.4 mL of Lumason. The findings of Lumason ultrasound images were compared to CT, MRI or histology. Specificity was 98% (43/44 patients).
Ultrasonography Of The Urinary Tract
Pediatric Patients
The efficacy of Lumason for the evaluation of pediatric patients with suspected or known vesicoureteral reflux was established in two published open-label single center studies (A and B). Patients received 1 mL of Lumason intravesically and underwent voiding urosonography (VUS). Patients were also evaluated with voiding cystourethrography (VCUG) as the reference standard. The presence or absence of urinary reflux with Lumason ultrasound was compared to the radiographic reference standard.
Study A evaluated 183 patients (94 male, 89 female; age 2 days -44 months) with a total of 366 kidney-ureter units. The images were interpreted by one on-site reader, blinded to the reference standard. Out of 103 reference standard-positive images, Lumason VUS was positive in 89 units and falsely negative in 14 units. In 263 units with negative reference standard, the Lumason ultrasonography was negative in 226 and falsely positive in 37.
Study B evaluated 228 patients (123 male, 105 female; age 6 days -13 years) with a total of 463 kidney-ureter units (some patients had more than 2 units). The images were interpreted independently by two on-site readers, blinded to the reference standard. Out of 71 reference standard positive images, Lumason ultrasonography was positive in 57 and falsely negative in 14. In 392 units with negative reference standard, Lumason ultrasonography was negative in 302 and falsely positive in 90.