The Food and Drug Administration approved a new drug Tuesday that not only treats a rare inherited disorder that causes extremely high cholesterol levels and heart attacks by age 30 but does so using a long-sought technology that can shut off specific genes that cause disease.
The drug, Kynamro, which was invented by Isis Pharmaceuticals and will be marketed by Sanofi’s Genzyme division, is unlikely to be a blockbuster. It has some worrisome side effects, and there might be no more than a few hundred people in the United States with the disease, known as homozygous familial hypercholesterolemia, or HoFH.
Still, Kynamro could become the first commercial success for the gene-silencing technique, which is known as antisense, and which some experts say is finally poised to fulfill its promise after more than two decades of research.
“What many people have been waiting for is validation where someone actually makes a profit and where patients actually benefit,” said Arthur M. Krieg, chief executive of RaNA Therapeutics, an antisense drug developer in Cambridge, Mass.
Isis, which is based in Carlsbad, Calif., has been pursuing antisense technology since the company’s founding in 1989, spending about $2 billion. It had one drug approved in 1998 for an infection associated with AIDS, but the drug did not sell well, and some experts said it did not really use the gene-silencing mechanism.
Isis’s experience contrasts with that of Gilead Sciences, which was also founded in the late 1980s to pursue antisense technology. It gave up after several years — selling the patents it no longer needed to Isis — and went on to develop antiviral drugs using other techniques. It is now a biotech superstar with a market value of $59.8 billion, compared with $1.4 billion for Isis.
Stanley T. Crooke, the founder and chief executive of Isis since its inception, said the long period of development was not unusual for a new technology.
“I told people it would be at least 20 years and $2 billion before we knew if the technology would work,” he said in an interview Tuesday. “We think it’s a seminal day for the technology and the company.”
The company or its partners are developing drugs to lower triglycerides, treat spinal muscular atrophy and reduce scarring from operations, among other things. The partners include Biogen Idec, Pfizer and AstraZeneca.
Two rival antisense companies, Sarepta Therapeutics and Prosensa, are developing drugs for muscular dystrophy that have shown promise in early clinical trials.