Carlsbad-based Isis Pharmaceuticals said Nov. 17 that its cholesterol-lowering drug mipomersen met all its goals in a late-stage trial, cutting levels of “bad” LDL cholesterol by an average of 25 percent in people genetically inclined to develop high cholesterol.

But the drug maker’s shares plunged almost 15 percent after the company said it would seek regulatory approval for the drug a year later than anticipated.

Shares of Isis, traded under the same name on Nasdaq, stood at $11.15 at midday Nov. 17, down from a pervious day’s close of $13.40.

Isis partner Genzyme of Massachusetts said it expects to apply for U.S. and European regulatory approval in mid-2011.

The drug maker presented the data at an American Heart Association meeting in Orlando, Fla. The 6.5-month trial tested the drug in 51 people with homozygous familial hypercholesterolemia, an inherited condition from both parents that often leads to cholesterol levels at four times the normal amount.

The trial, designed to test once-weekly injectable mipomersen on top of lipid-lowering statins or Merck & Co.’s Zetia, showed average improvements of 25 percent, compared with 3 percent in the placebo group, although the therapy lowered some patients’ LDL levels by as much as 80 percent.

“Mipomersen has the potential to change the standard of care for (homozygous familial hypercholesterolemia) patients,” said Frederick Raal, the study’s lead investigator.

About 12 percent of patients saw elevated liver enzyme levels, although the company said other tests to check for liver dysfunction returned normal results.

An ongoing Phase 3 study is also testing the drug in patients with heterozygous familial hypercholesterolemia, in which patients inherit a tendency toward high LDL from a single parent.

— Heather Chambers