CHICAGO, Dec 7 (Reuters) - A hot new field of genetic therapy known as RNA interference may offer new approaches to medicine down the road, but Merck & Co Inc MRK.N is putting the technology to work now to help ensure that conventional drugs in its pipeline will work.

“Ninety-three percent of our drug programs fail, and 35 to 40 percent of those fail because they are simply the wrong target,” Dr. Alan Sachs, head of the company’s global RNA Therapeutics research operation, said in a telephone interview.

Merck believes RNA interference can help avoid these costly wrong turns.

Sachs is charged with overseeing Merck’s $1.1 billion acquisition two years ago of Sirna Therapeutics, a company focused on developing drugs using RNA interference, or RNAi, which was the basis of the 2006 Nobel Prize in medicine.

RNA stands for ribonucleic acid, a genetic messenger that is emerging as a key player in the disease process.

Dozens of biotechnology companies are looking for ways to manipulate RNA to block genes that produce disease-causing proteins involved in cancer, blindness or AIDS.

And while many are grabbing the spotlight, Sachs likens his company’s work to “busy little bees, knowing exactly where we are going and what it will take to get there.”

Since the Sirna acquisition, Sachs said, his team has been using the technology in animal studies to quickly evaluate the potential of new chemical compounds as future drugs.

“We have a delivery system that is safe in rodents and it is a very, very powerful approach,” he said.

RNA interference also has potential to turn off the activity of genes that cause disease.

“It is absolutely the long-term promise that we anticipate will position Merck for success over the next few decades, but is high risk because it is very early,” Sachs said.

ENSURING SUCCESS

Sachs said a significant part of the value of the Sirna deal “was the increased probability of success of all of our programs.”

“The cost of failure is huge. It’s 65 to 70 percent of the total cost of making medicines,” Sachs said. “Anything that increases your probability of success is a solid investment.”

As for therapies, Sachs said the company will focus first on treatments for acute disease, then move gradually into therapies that would be used on a chronic or continual basis.

But first the company must overcome one of the biggest roadblocks to the RNAi therapies, which is how to deliver the therapy safely and efficiently into people.

The company is working on a delivery system using tiny, synthetic fat molecules called lipid nanoparticles.

“Effectively, it’s a particle that binds to nucleic acid and allows it to circulate in the bloodstream without it being cleared by the kidney,” Sachs said.

“The advantage of this particle is because of the lipid composition, it rapidly is taken up by the liver. Within the first 5 to 10 minutes, over 70 percent of the material is absorbed in the liver.”

That would make it an excellent delivery system for diseases that attack the liver, such as viral hepatitis or hepatocellular carcinoma, a type of liver cancer.

Other potentials include direct delivery, such as injecting RNAi therapies directly into the eye, and inhalation into the lungs.

"We are in collaboration with GlaxoSmithKline GSK.L in the respiratory area and are working jointly on both targets and delivery," Sachs said.

"And we just completed a collaboration with Allergan AGN.N looking at the eye and targets within the eye. Now we are initiating our own efforts within that area." (Editing by Maggie Fox and Mohammad Zargham)