UPDATE 1-FDA approves Sanofi drug for rare cholesterol disorder

* Drug from Sanofi and Isis Pharmaceuticals to be sold as Kynamro

* FDA requiring four post-marketing studies

* Condition affects about 1 million Americans

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Jan 29 (Reuters) - The U.S. Food and Drug Administration on Tuesday approved a drug made by Sanofi SA and Isis Pharmaceuticals Inc designed to treat a rare genetic disorder that causes dangerously high levels of bad LDL cholesterol.

The FDA's decision comes after an outside panel of experts recommended in October that the agency approve the drug, saying it is, on balance, safe and effective for the roughly 1 million Americans suffering from homozygous familial hypercholesterolemia, or HoFH.

The ruling follows a rejection by European regulators over safety concerns. The European Medicines Agency noted in December that a high proportion of patients stopped taking the drug within two years, mainly due to side effects such as injection site reactions, flu-like symptoms and liver toxicity.

Sanofi said it planned to request a re-examination of the European decision and expects feedback from the agency in the second quarter of 2013.

The FDA said it was requiring four post-marketing studies as a condition of approval, including an enhanced pharmacovigilance program to monitor reports of malignancy, immune reactions and liver problems. The approval also included a Risk Evaluation and Mitigation Strategy (REMS) to assure safe use, including documentation of safe-use conditions, which requires an authorization form for each new prescription.

Kynamro is administered by injection once a week and is expected to be used on top of more traditional cholesterol-lowering medicines, such as statins.

Patients with HoFH have inherited abnormalities in liver cells that are responsible for clearing "bad" LDL particles from the blood. As a results, those with severe forms of the disease can have LDL levels that are two to four times higher than recommended levels, even when they are taking multiple cholesterol medications.

In clinical trials patients who took Kynamro, known generically as mipomersen, saw their LDL cholesterol levels drop nearly 22 percent further than those who took a placebo. Nonetheless, some experts have expressed concern about the potential for the drug to cause liver problems and increase the risk of cancer.

In December, the FDA approved a drug for the same condition made by Aegerion Pharmaceuticals Inc. Aegerion's drug, Juxtapid, carries a boxed warning, the strongest possible, and will be available through a restricted program due to the risk of liver damage.

(Reporting By Toni Clarke and Bill Berkrot; editing by Carol Bishopric and Andrew Hay)