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siRNA drug safely halved LDL cholesterol in phase 3 ORION-11
  Publish date: September 4, 2019
https://www.mdedge.com/cardiology/article/207511/lipid-disorders/sirna-drug-safely-halved-ldl-cholesterol-phase-3-orion-11?utm_source=News_CARD_cc_090819_F&utm_medium=email&utm_content=ESC 2019: dapagliflozin for heart failure, siRNA drug cuts LDL cholesterol, and more
PARIS - A small interfering RNA drug, inclisiran, safely halved LDL cholesterol levels in more than 800 patients in a phase 3, multicenter study, in a big step toward this drug coming onto the market and offering an alternative way to harness the potent cholesterol-lowering power of PCSK9 inhibition.
In the reported study - which enrolled patients with established cardiovascular disease, familial hypercholesterolemia, type 2 diabetes, or a high Framingham Risk Score - participants received inclisiran as a semiannual subcutaneous injection. The safe efficacy this produced showed the viability of a new way to deliver lipid-lowering therapy that guarantees compliance and is convenient for patients.
The prospect of lowering cholesterol with about the same potency as the monoclonal antibodies that block PCSK9 (proprotein convertase subtilisin/kexin type 9) activity but administered as a biannual injection "enables provider control over medication adherence, and may offer patients a meaningful new choice that is safe and convenient and has assured results," Kausik K. Ray, MD, said at the annual congress of the European Society of Cardiology. The durable effect of the small interfering RNA (siRNA) agent "offers a huge advantage," and "opens the field," said Dr. Ray, a cardiologist and professor of public health at Imperial College, London.
He also highlighted the "excellent" safety profile seen in the 811 patients treated with inclisiran, compared with 804 patients in the study who received placebo. After four total injections of inclisiran spaced out over 450 days (about 15 months), the rate of treatment-emergent adverse events and serious events was virtually the same in the two treatment arms, and with no signal of inclisiran causing liver effects, renal or muscle injury, damage to blood components, or malignancy. The serial treatment with inclisiran that patients received - at baseline, 90, 270, and 450 days - produced no severe injection-site reactions, and transient mild or moderate injection-site reactions in just under 5% of patients.
Safety issues, such as more-severe injection-site reactions, thrombocytopenia, hepatotoxicity, and flu-like symptoms, plagued siRNA drugs during their earlier days of development, but more recently next-generation siRNA drugs with modified structures have produced much better safety performance, noted Richard C. Becker, MD, professor of medicine and director of the Heart, Lung, & Vascular Institute at the University of Cincinnati. The new-generation siRNAs such as inclisiran are "very well tolerated," he said in an interview.
The Food and Drug Administration approved the first siRNA drug in August 2018, and in the year since then a few others have also come onto the U.S. market, Dr. Becker said.
Like other siRNA drugs, the activity of inclisiran comes from a short RNA segment that is antisense to a particular messenger RNA (mRNA) target. In the case of inclisiran, the target is the mRNA for the PCSK9 enzyme produced in hepatocytes, and that decreases the number of LDL cholesterol receptors on the cell's surface. When the antisense RNA molecule encounters a PCSK9 mRNA, the two bind and the mRNA is then degraded by a normal cell process. This cuts the cell's production of the PCSK9 protein, resulting in more LDL cholesterol receptors on the cell's surface that pull more LDL cholesterol from the blood. The blocking of PCSK9 activity by inclisiran is roughly equivalent to the action of the PCSK9 monoclonal antibodies that have now been on the U.S. market for a few years. Also like other siRNA drugs, the RNA of inclisiran is packaged so that, once injected into a patient, the RNA molecules travel to the liver and enter hepatocytes, where they exert their activity.
"No one has concerns about inclisiran being able to lower LDL [cholesterol], and there have been no safety signals. The data we have seen so far look very reassuring, and in particular has been very safe for the liver," commented Marc S. Sabatine, MD, professor of medicine at Harvard Medical School, Boston, who has led several studies involving PCSK9-targeted drugs and is helping to run ORION-4, a 15,000-patient study of inclisiran designed to assess the drug's effect on clinical events. Results from ORION-4 are not expected until about 2024.
"The PCSK9 inhibitors in general have been a huge advance for patients, and the more kinds of drugs we have to target PCSK9, the better," he said in an interview.
The study reported by Dr. Ray, ORION-11, enrolled 1,617 patients with high atherosclerotic disease risk at 70 sites in six European countries and South Africa. The study's primary efficacy endpoint was reduction from baseline in LDL cholesterol both at 510 days (about 17 months) after the first dose and also throughout the 15-month period that started 3 months after the first dose. The average reduction seen after 510 days was 54%, compared with baseline, and the time-averaged reduction during the 15-month window examined was 50%, Dr. Ray said. The results also showed a consistent reduction in LDL cholesterol in virtually every patient treated with inclisiran.
Inclisiran shows sustained and significant declines in LDL-C
Two other phase 3 studies of inclisiran with similar design have been completed, and the results will come out before the end of 2019, according to a statement from the Medicines Company, which is developing the drug. The statement also said that the company plans to file their data with the FDA for marketing approval for inclisiran before the end of 2019. In the recent past, the FDA has approved drugs for the indication of lowering LDL cholesterol before evidence is available to prove that the agent has benefits for reducing clinical events.
Future studies of inclisiran will explore the efficacy of a single annual injection of the drug as an approach to primary prevention of cardiovascular disease, Dr. Ray said.
ORION-11 was sponsored by the Medicines Company. Dr. Ray is a consultant to it and to several other companies. Dr. Becker had no relevant disclosures. Dr. Sabatine has received research support from the Medicines Company and several other companies, and has received personal fees from Anthos Therapeutics, Bristol-Myers Squibb, CVS Caremark, Daiichi Sankyo, DalCor Pharmaceuticals, Dyrnamix, and Ionis.

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