Molecular Imaging of Primary Amyloid Cardiomyopathy

Primary light chain amyloidosis (AL) is the most common systemic amyloidosis, resulting from
a plasma cell dyscrasia, a hematological malignancy. It causes a restrictive cardiomyopathy
(AL-CMP) in over 70% of individuals. AL-CMP is as lethal as stage 4 lung cancer and more
lethal than any other form of restrictive heart disease; if untreated, the mortality rate is
50% within 18 months. Moreover, myocardial dysfunction, the hallmark of AL-CMP, significantly
increases early treatment related mortality, predominantly cardiovascular death, and is a
powerful predictor of poor long-term survival. Two potentially treatable mechanisms underlie
myocardial dysfunction—mechanical effects of amyloid and toxic effects from circulating light
chain/ amyloid interactions—and predispose to heart failure, arrhythmias, and sudden death in
individuals with AL-CMP. Until now, efforts to determine the mechanisms of AL-CMP have been
hampered by a lack of animal models and the limitations of noninvasive techniques to directly
image myocardial amyloid. A recent breakthrough, 18F-florbetapir PET/CT, has provided for the
first time specific and quantitative imaging of myocardial amyloid including toxic amyloid
protofibrils. Furthermore, we propose to investigate three pre-clinically proven pathways of
light chain toxicity in humans—myocardial oxidative metabolism, oxidative stress, and
coronary microvascular function. Our central hypotheses are that myocardial 18F-florbetapir
retention is a biomarker for aggressiveness of AL-CMP and that effective chemotherapy will,
by reducing circulating light chains, decrease aggressiveness of AL-CMP and improve oxidative
stress, myocardial oxidative metabolism, microvascular function and contractile function,
prior to an improvement in myocardial amyloid content. In Aim 1, we will quantify myocardial
18F-florbetapir retention as a marker of aggressive myocardial disease in individuals with
AL-CMP and active plasma cell dyscrasia compared to control individuals with AL-CMP and
long-term hematological remission. In Aim 2, we propose, using advanced imaging, to assess
the effects of light chain reduction due to chemotherapy on myocardial structure, function,
and metabolism and define the time course of these changes. Serial ECV and strain imaging by
CMR, serum F2-isoprostanes and peroxynitrite levels, myocardial oxidative metabolism (Kmono)
and coronary flow reserve by 11C-acetate PET, and 18F-florbetapir imaging will not only
intricately characterize the myocardial substrate in AL-CMP, but also identify changes in
response to therapy. The proposed studies offer the potential to transform our current
understanding of AL-CMP as a restrictive heart disease caused by passive amyloid-related
architectural damage to that of a more complex disorder resulting from both passive and
aggressive factors. The results of these studies may form the foundation for drug discovery
programs to prevent and cure AL-CMP.

Inclusion criteria:

- Age > 18 years

- Diagnosis of light chain amyloidosis by standard criteria (immunofixation of serum and
urine, IgG free light chain (FLC) assay, a biopsy of fat pad/ bone marrow, or organ
biopsy, followed by typing of the light chain using immunohistochemistry or immunogold
assay with confirmation by Mass spectroscopy as needed)

- Willing and able to provide consent

- Additional inclusion criteria for the Remission AL-CMP: Hematological response defined
as complete hematological remission or very good partial response-differential free
light chain (dFLC)<40 mg/dL for > 1 year prior to enrollment

- Additional inclusion criteria for the Active AL-CMP - exercise: Ability to perform
supine bicycle exercise. Enrollment to this arm will stop after 25 subjects complete
baseline and 6 months studies.

- Additional inclusion criteria for the Active AL Pre-CMP - Normal left ventricular wall
thickness (≤ 12 mm) and normal LVEF (≥55%) on echocardiography within 3 months or
increased wall thickness with normal cardiac biomarker levels not meeting above
definition.

- Additional inclusion criteria for Control Multiple Myeloma subjects: diagnosis of
multiple myeloma without concomitant amyloidosis by standard criteria

- Additional inclusion criteria for Control Heart Failure subjects: diagnosis of heart
failure without amyloidosis by standard criteria

Exclusion Criteria:

- Hemodynamic instability

- Decompensated heart failure (unable to lie flat for 1 hour)

- Concomitant non-ischemic non-amyloid heart disease (valvular heart disease or dilated
cardiomyopathy)

- Known obstructive epicardial coronary artery disease with stenosis > 50% in any single
territory

- Severe claustrophobia despite use of sedatives

- Presence of MRI contraindications such as metallic implants (pacemaker or AICD) at the
time of study enrollment

- Significant renal dysfunction with estimated glomerular filtration rate < 30 ml/min/m2
within 14 days of each cardiac MRI study. Subjects who develop renal dysfunction over
the course of the study, meeting criteria listed above, will be excluded from the
cardiac MRI scan except for group D. Group D subjects with eGFR < 30 ml/min/1.73 m2
will undergo MRI without gadolinium contrast.

- Subjects on dialysis will be excluded

- Pregnant state. For women in child bearing age, a urine pregnancy test will be
performed prior to the PET and the cardiac MRI studies

- Documented allergy to F-18 florbetapir, C-11 acetate or gadolinium.

- Additional exclusion criteria for the active AL-CMP subjects: Subjects unable to
return to BWH for 6 and 12 month clinical evaluation

- Additional exclusion criteria for active AL-CMP-exercise subjects: Inability to
exercise or return to BWH for C-11 acetate PET/CT at baseline and 6 month clinical
evaluations.

- Additional exclusion criteria for active AL Pre-CMP- Inability to return to BWH 12
month clinical evaluation.