The
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Targeting APOC3 in the Familial Chylomicronemia Syndrome Daniel Gaudet, M.D., Ph.D., Diane Brisson, Ph.D., Karine Tremblay, Ph.D., Veronica J. Alexander, Ph.D., Walter Singleton, M.D., Steven G. Hughes, M.B., B.S., Richard S. Geary, Ph.D., Brenda F. Baker, Ph.D., Mark J. Graham, M.S., Rosanne M. Crooke, Ph.D., and Joseph L. Witztum, M.D.
Sum m a r y The familial chylomicronemia syndrome is a genetic disorder characterized by severe hypertriglyceridemia and recurrent pancreatitis due to a deficiency in lipoprotein lipase (LPL). Currently, there are no effective therapies except for extreme restriction in the consumption of dietary fat. Apolipoprotein C-III (APOC3) is known to inhibit LPL, although there is also evidence that APOC3 increases the level of plasma triglycerides through an LPL-independent mechanism. We administered an inhibitor of APOC3 messenger RNA (mRNA), called ISIS 304801, to treat three patients with the familial chylomicronemia syndrome and triglyceride levels ranging from 1406 to 2083 mg per deciliter (15.9 to 23.5 mmol per liter). After 13 weeks of study-drug administration, plasma APOC3 levels were reduced by 71 to 90% and triglyceride levels by 56 to 86%. During the study, all patients had a triglyceride level of less than 500 mg per deciliter (5.7 mmol per liter) with treatment. These data support the role of APOC3 as a key regulator of LPL-independent pathways of triglyceride metabolism.
From the ECOGENE-21 Clinical Research Center, Chicoutimi Hospital, Chicoutimi, and the Department of Medicine, Université de Montréal, Montreal — both in Canada (D.G., D.B., K.T.); and Isis Pharmaceuticals, Carlsbad (V.J.A., W.S., S.G.H., R.S.G., B.F.B., M.J.G., R.M.C.), and the Department of Medicine, Division of Endocrinology–Metabolism, University California, San Diego, School of Medicine, La Jolla (J.L.W.) — both in California. Address reprint requests to Dr. Witztum at the Department of Medicine, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0682, or at jwitztum@ ucsd.edu; or to Dr. Gaudet at the ECOGENE-21 Clinical Research Center, 225 Saint-Vallier, Chicoutimi, QC G7H 7P2, Canada, or at [email protected]. N Engl J Med 2014;371:2200-6. DOI: 10.1056/NEJMoa1400284 Copyright © 2014 Massachusetts Medical Society.
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T
he familial chylomicronemia syndrome is a rare autosomal recessive disease characterized by the buildup in the blood of fat particles called chylomicrons (chylomicronemia), severe hypertriglyceridemia, and the risk of recurrent and potentially fatal pancreatitis and other complications.1 It is caused by mutations in the gene encoding LPL or, less frequently, by mutations in genes encoding other proteins necessary for LPL function.2 Patients with this syndrome have plasma triglyceride levels ranging from 10 to 100 times the normal value (1500 to 15,000 mg per deciliter [17 to 170 mmol per liter]), eruptive xanthomas, arthralgias, neurologic symptoms, lipemia retinalis, and hepatosplenomegaly.3 Nearly all patients have recurrent episodes of severe abdominal pain, with or without pancreatitis, that interfere with normal life and result in frequent hospitalizations. These episodes can result in chronic pancreatitis and symptoms of exocrine or endocrine insufficiency, including diabetes and even fatal events.1 Currently available triglyceride-lowering agents are not completely effective in controlling chylomicronemia in these patients.4,5 Glybera, an LPL gene-replacement therapy, was recently approved in Europe but is not available in the United States.6 Thus, for U.S. patients, the only therapeutic approach that effectively maintains triglyceride levels below 880 mg per deciliter (10 mmol per liter),7 a value that greatly reduces the risk of pancreatitis, is severe dietary fat restriction,
n engl j med 371;23 nejm.org december 4, 2014
The New England Journal of Medicine Downloaded from nejm.org at UNIV OF MEMPHIS on December 4, 2014. For personal use only. No other uses without permission. Copyright © 2014 Massachusetts Medical Society. All rights reserved.
brief report
together with avoidance of alcohol and certain medications.8 Lifetime compliance with these requirements is difficult, and episodes of chylomicronemia, abdominal pain, and recurrent pancreatitis are common. Therefore, additional therapies are required to maintain triglyceride levels below 880 mg per deciliter. APOC3 is a glycoprotein (consisting of 79 amino acids) that is synthesized principally in the liver and to a lesser extent in the intestines and is associated with lipoproteins containing apolipoprotein B, including chylomicrons and very-low-density lipoprotein (VLDL) particles, as well as high-density lipoprotein (HDL) particles.9 In genetic, preclinical, and phase 1 clinical studies, APOC3 has emerged as a key regulator of plasma triglyceride levels.10-17 Since the 1970s, data have indicated that the mode of action of APOC3 is through its inhibition of LPL activity.18 APOC3 is a potent inhibitor of the activation of LPL that is mediated by apolipoprotein C-II, resulting in the inhibition of lipolysis of triglyceride-rich-lipoproteins.19 APOC3 has also been reported to inhibit hepatic lipase activity,20 to promote intrahepatic VLDL assembly and secretion,21 and to inhibit hepatic clearance of remnants of triglyceride-rich lipoproteins.22 However, the importance of these LPL-independent mechanisms is unknown. ISIS 304801 is a second-generation 2′-O-(2methoxyethyl)–modified antisense inhibitor of APOC3 synthesis.10 Inhibition of APOC3 synthesis in the liver occurs through sequence-specific binding of ISIS 304801 to APOC3 mRNA, which in turn elicits the degradation of APOC3 mRNA by RNase H1, an endogenous ribonuclease expressed ubiquitously in mammalian cells.23 In a phase 1 clinical study involving healthy volunteers, ISIS 304801 caused dose-dependent and prolonged reductions in plasma APOC3 levels with concomitant lowering of plasma triglyceride levels,10 and in recent phase 2 studies, ISIS 304801 was effective in lowering triglyceride levels in patients with elevated VLDL levels due to a variety of conditions.24,25 Because patients with the familial chylomicronemia syndrome lack functional LPL activity, and because the primary mode of action of APOC3 is postulated to be the inhibition of the LPL-dependent pathway of clearance of triglyceride-rich lipoproteins, one would predict that ISIS
304801 would have either no effect or only a minimal effect in lowering the elevated triglyceride levels in patients with this syndrome. However, since these patients do not have exponential accumulation of triglyceride-rich lipoproteins, an LPL-independent rescue pathway must exist in order for them to survive. Preclinical studies suggest that APOC3 also modulates triglyceride levels through LPL-independent pathways. We conducted a study to determine whether treatment with ISIS 304801 would reduce triglyceride levels in three patients with the familial chylomicronemia syndrome and triglyceride levels ranging from 1406 to 2083 mg per deciliter (15.9 to 23.5 mmol per liter).
Me thods Patients
The three study patients, who were unrelated to one another, had either homozygous or compound heterozygous null LPL mutations, P207L and G188E (see Table S1 in the Supplementary Appendix, available with the full text of this article at NEJM.org). These genetic variants result in the production of LPL protein that is catalytically defective. Both mutations have been extensively studied and are known to result in a mutant protein that has less than 5% of normal LPL activity.6 Patient 2 had received Glybera 5 years earlier. In Patients 2 and 3, measurements of LPL activity after the administration of heparin showed values that were less than 2 to 4 nmol of free fatty acids per minute per milliliter of plasma (
n e w e ng l a n d j o u r na l
of
m e dic i n e
brief report
Targeting APOC3 in the Familial Chylomicronemia Syndrome Daniel Gaudet, M.D., Ph.D., Diane Brisson, Ph.D., Karine Tremblay, Ph.D., Veronica J. Alexander, Ph.D., Walter Singleton, M.D., Steven G. Hughes, M.B., B.S., Richard S. Geary, Ph.D., Brenda F. Baker, Ph.D., Mark J. Graham, M.S., Rosanne M. Crooke, Ph.D., and Joseph L. Witztum, M.D.
Sum m a r y The familial chylomicronemia syndrome is a genetic disorder characterized by severe hypertriglyceridemia and recurrent pancreatitis due to a deficiency in lipoprotein lipase (LPL). Currently, there are no effective therapies except for extreme restriction in the consumption of dietary fat. Apolipoprotein C-III (APOC3) is known to inhibit LPL, although there is also evidence that APOC3 increases the level of plasma triglycerides through an LPL-independent mechanism. We administered an inhibitor of APOC3 messenger RNA (mRNA), called ISIS 304801, to treat three patients with the familial chylomicronemia syndrome and triglyceride levels ranging from 1406 to 2083 mg per deciliter (15.9 to 23.5 mmol per liter). After 13 weeks of study-drug administration, plasma APOC3 levels were reduced by 71 to 90% and triglyceride levels by 56 to 86%. During the study, all patients had a triglyceride level of less than 500 mg per deciliter (5.7 mmol per liter) with treatment. These data support the role of APOC3 as a key regulator of LPL-independent pathways of triglyceride metabolism.
From the ECOGENE-21 Clinical Research Center, Chicoutimi Hospital, Chicoutimi, and the Department of Medicine, Université de Montréal, Montreal — both in Canada (D.G., D.B., K.T.); and Isis Pharmaceuticals, Carlsbad (V.J.A., W.S., S.G.H., R.S.G., B.F.B., M.J.G., R.M.C.), and the Department of Medicine, Division of Endocrinology–Metabolism, University California, San Diego, School of Medicine, La Jolla (J.L.W.) — both in California. Address reprint requests to Dr. Witztum at the Department of Medicine, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0682, or at jwitztum@ ucsd.edu; or to Dr. Gaudet at the ECOGENE-21 Clinical Research Center, 225 Saint-Vallier, Chicoutimi, QC G7H 7P2, Canada, or at [email protected]. N Engl J Med 2014;371:2200-6. DOI: 10.1056/NEJMoa1400284 Copyright © 2014 Massachusetts Medical Society.
2200
T
he familial chylomicronemia syndrome is a rare autosomal recessive disease characterized by the buildup in the blood of fat particles called chylomicrons (chylomicronemia), severe hypertriglyceridemia, and the risk of recurrent and potentially fatal pancreatitis and other complications.1 It is caused by mutations in the gene encoding LPL or, less frequently, by mutations in genes encoding other proteins necessary for LPL function.2 Patients with this syndrome have plasma triglyceride levels ranging from 10 to 100 times the normal value (1500 to 15,000 mg per deciliter [17 to 170 mmol per liter]), eruptive xanthomas, arthralgias, neurologic symptoms, lipemia retinalis, and hepatosplenomegaly.3 Nearly all patients have recurrent episodes of severe abdominal pain, with or without pancreatitis, that interfere with normal life and result in frequent hospitalizations. These episodes can result in chronic pancreatitis and symptoms of exocrine or endocrine insufficiency, including diabetes and even fatal events.1 Currently available triglyceride-lowering agents are not completely effective in controlling chylomicronemia in these patients.4,5 Glybera, an LPL gene-replacement therapy, was recently approved in Europe but is not available in the United States.6 Thus, for U.S. patients, the only therapeutic approach that effectively maintains triglyceride levels below 880 mg per deciliter (10 mmol per liter),7 a value that greatly reduces the risk of pancreatitis, is severe dietary fat restriction,
n engl j med 371;23 nejm.org december 4, 2014
The New England Journal of Medicine Downloaded from nejm.org at UNIV OF MEMPHIS on December 4, 2014. For personal use only. No other uses without permission. Copyright © 2014 Massachusetts Medical Society. All rights reserved.
brief report
together with avoidance of alcohol and certain medications.8 Lifetime compliance with these requirements is difficult, and episodes of chylomicronemia, abdominal pain, and recurrent pancreatitis are common. Therefore, additional therapies are required to maintain triglyceride levels below 880 mg per deciliter. APOC3 is a glycoprotein (consisting of 79 amino acids) that is synthesized principally in the liver and to a lesser extent in the intestines and is associated with lipoproteins containing apolipoprotein B, including chylomicrons and very-low-density lipoprotein (VLDL) particles, as well as high-density lipoprotein (HDL) particles.9 In genetic, preclinical, and phase 1 clinical studies, APOC3 has emerged as a key regulator of plasma triglyceride levels.10-17 Since the 1970s, data have indicated that the mode of action of APOC3 is through its inhibition of LPL activity.18 APOC3 is a potent inhibitor of the activation of LPL that is mediated by apolipoprotein C-II, resulting in the inhibition of lipolysis of triglyceride-rich-lipoproteins.19 APOC3 has also been reported to inhibit hepatic lipase activity,20 to promote intrahepatic VLDL assembly and secretion,21 and to inhibit hepatic clearance of remnants of triglyceride-rich lipoproteins.22 However, the importance of these LPL-independent mechanisms is unknown. ISIS 304801 is a second-generation 2′-O-(2methoxyethyl)–modified antisense inhibitor of APOC3 synthesis.10 Inhibition of APOC3 synthesis in the liver occurs through sequence-specific binding of ISIS 304801 to APOC3 mRNA, which in turn elicits the degradation of APOC3 mRNA by RNase H1, an endogenous ribonuclease expressed ubiquitously in mammalian cells.23 In a phase 1 clinical study involving healthy volunteers, ISIS 304801 caused dose-dependent and prolonged reductions in plasma APOC3 levels with concomitant lowering of plasma triglyceride levels,10 and in recent phase 2 studies, ISIS 304801 was effective in lowering triglyceride levels in patients with elevated VLDL levels due to a variety of conditions.24,25 Because patients with the familial chylomicronemia syndrome lack functional LPL activity, and because the primary mode of action of APOC3 is postulated to be the inhibition of the LPL-dependent pathway of clearance of triglyceride-rich lipoproteins, one would predict that ISIS
304801 would have either no effect or only a minimal effect in lowering the elevated triglyceride levels in patients with this syndrome. However, since these patients do not have exponential accumulation of triglyceride-rich lipoproteins, an LPL-independent rescue pathway must exist in order for them to survive. Preclinical studies suggest that APOC3 also modulates triglyceride levels through LPL-independent pathways. We conducted a study to determine whether treatment with ISIS 304801 would reduce triglyceride levels in three patients with the familial chylomicronemia syndrome and triglyceride levels ranging from 1406 to 2083 mg per deciliter (15.9 to 23.5 mmol per liter).
Me thods Patients
The three study patients, who were unrelated to one another, had either homozygous or compound heterozygous null LPL mutations, P207L and G188E (see Table S1 in the Supplementary Appendix, available with the full text of this article at NEJM.org). These genetic variants result in the production of LPL protein that is catalytically defective. Both mutations have been extensively studied and are known to result in a mutant protein that has less than 5% of normal LPL activity.6 Patient 2 had received Glybera 5 years earlier. In Patients 2 and 3, measurements of LPL activity after the administration of heparin showed values that were less than 2 to 4 nmol of free fatty acids per minute per milliliter of plasma (
