1. Aaron K. Banks
Department of Chemistry, Rhodes College, Memphis, TN 38112
Recombinant Apolipoprotein AIMilano and its Potential as an Atherosclerosis Treatment
Atherosclerosis is a disease in which plaque builds up in arteries over decades,
reducing the bodies ability to transport oxygen through the blood1.
Apolipoprotein A-I (apo A-I) is the primary component of High Density
Lipoprotein (HDL), constituting 60% of its mass2. HDL has been shown to have
significant athero-protective properties3; these properties have been suggested
to be due to HDL’s role in reverse cholesterol transport (RCT)4.The Milano
variant of Apoliprotein A-I (apo A-IM) has a cysteine inserted in place of
arginine at position 1735. Individuals with the apo A-IM mutation express a
phenotype of decreased HDL and apo A-I levels, yet lowered levels of
atherosclerosis6.
In 2010, atherosclerotic vascular diseases (AVD) accounted for more than
500,000 deaths in the US alone. While this number has decreased by 15% since
1990, AVD is still one of the leading causes of death in the US8. Recombinant
apo A-IM shows promise as a treatment for the prevention of these diseases.
Background Methods
Conclusions
Figure 1: Illustration of three proposed structures of HDL.
A shows wild-type HDL before cholesterol uptake. B
shows wild-type HDL after uptake. C shows a proposed
structure of HDLMilano; note the parallel double belt
formation in comparison to the bent formation of
HDLWT
7.
Motivation References
Figure 2: Diagram describing RCT from
peripheral tissues to the liver, where
cholesterol is excreted as either feces or
bile4.
Results/Discussion
Two random, double blind studies were performed on the effects of a drug (ETC-216)
made of recombinant apo A-IM and a natural phopholipid to mimic the effects of nascent
HDL. ETC-216 was given intravenously at two different dosage levels (15 or 45 mg/kg)
once per week for five weeks. Intravenous ultrasound (IVUS) was used to determine
intravenous measurements9,10.
• ETC-216, a drug made from recombinant apo A-IM was found to be able to
significantly reduce arterial plaque in two clinical trials
• While ETC-216 was able to reduce plaque volume, lumen volume did not
change significantly
• More trials are needed to determine the overall effects of drugs based upon
recombinant apo A-IM
Figure 5: IVUS cross-section of target
artery of a patient who received high
dose of ETC-216. Atheroma
regression can be seen from 8.1 mm2
to 5.35 mm2, yet lumen area did not
change significantly (6.27 to 6.23
mm2)9.
Table 1: Data comparing causes of death in the United States in both 1990 and
2010. Note the decrease in deaths due to cardiovascular diseases from 1990 to
20108.
1. Strong et al. Prevalence and extent of atherosclerosis in adolescents and young adults: implications for prevention from the Pathobiological
Determinants of Atherosclerosis in Youth Study. Jama (1999) 281, 727–735.
2. Tall. Plasma high density lipoproteins. Metabolism and relationship to atherogenesis. Journal of Clinical Investigation (1990) 86, 379.
3. LaRosa et al. The cholesterol facts. A summary of the evidence relating dietary fats, serum cholesterol, and coronary heart disease. A joint
statement by the American Heart Association and the National Heart, Lung, and Blood Institute. The Task Force on Cholesterol Issues,
American Heart Association. Circulation (1990) 81, 1721.
4. Rader et al. The role of reverse cholesterol transport in animals and humans and relationship to atherosclerosis. Journal of Lipid Research
(2009) 50, S189–S194.
5. Weisgraber et al. A-I Milano apoprotein. Isolation and characterization of a cysteine-containing variant of the AI apoprotein from human high
density lipoproteins. Journal of Clinical Investigation (1980) 66, 901.
6. Franceschini et al. A-I Milano apoprotein. Decreased high density lipoprotein cholesterol levels with significant lipoprotein modifications and
without clinical atherosclerosis in an Italian family. Journal of Clinical Investigation (1980) 66, 892.
7. Gursky et al. Structural basis for distinct functions of the naturally occurring Cys mutants of human apolipoprotein AI. Journal of Lipid
Research (2013) 54, 3244–3257.
8. Murphy et al. Deaths: Final Data for 2010. National Vital Statistics Reports (2010) 61(4), 1-99. National Center for Health Statistics.
9. Nissen et al. Effects of Recombinant Apo A-I Milano on Coronary Atherosclerosis in Patients with Acute Coronary Symptoms. Jama (2003)
290(17), 2292-2300.
10. Nicholls et al. Relationship Between Atheroma Regression and Change in Lumen Size After Infusion of Apolipoprotein A-I Milano. JACC
(2006) 47(5), 922-927.
Figure 4: Cross-sections of target arteries are shown, taken via IVUS. The atheroma area is
determined by subtracting the lumen area from the external elastic membrane (EEM) area9.
Figure 6: Top image shows illustration of
decreasing arterial plaque, yet constant lumen
area. Middle and bottom images are IVUS cross-
sections of patients who were given ETC-216. Left
images show baseline, while right images show
arteries after treatment. Much like the Nissen
study, lumen area was unchanged, even with a
significant reduction in arterial plaque10.
Table 2: Data from Nissen study on percent atheroma volume in the target artery.
Note the slight increase in plaque with placebo (0.14%) and decrease with ETC-216
(1.06%)9.
Table 3: Data on total atheroma volume in target artery. Note the baseline difference
between placebo and ETC-216 groups, along with the difference between change from
baseline9.
Table 4: Data from Nicholls study
comparing effects of ETC-216 on
greatest and least diseased
segments of the study, as
determined by baseline plaque
volume. The greatest diseased
segment showed a marked
reduction in plaque volume, yet
little change in lumen in lumen
volume. This lack of change in
lumen size can be attributed to a
shrinkage of external elastic
membrane (EEM). The least
diseased segment showed no
significant change in plaque
burden nor lumen size10.
Figure 3: Diagram showing
proposed models of the double
belt formations of both apo A-
IWT and apo A-IM. Figures A
and B show both molecules
laid on top of one another,
while C and D show only one
molecule. Cysteine insertion at
position 173 in apo A-IM is
marked by yellow diamonds. It
has been suggested that the
structural differences in apo A-
IM allows HDLMilano to uptake
cholesterol at a faster rate than
wild type HDL, thereby
allowing more efficient reverse
cholesterol transport7.