Alnylam Notches a Game-Changing RNAi Win

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Alnylam Pharmaceuticals, Inc. (NASDAQ: ALNY) is researching therapies that can treat genetic diseases by interfering with gene expression. Though Alnylam has yet to validate its approach with a Food and Drug Administration approval for one of its drugs, that could change following the release of positive late-stage trial results for patisiran, a drug that may delay disease progression in patients diagnosed with hereditary forms of amyloidosis with polyneuropathy.

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What's RNAi?

In 1986, Richard Jorgensen of the University of Arizona in Tucson introduced a genetic code (DNA) into petunias to make their color more vivid. Instead, he stumbled upon an important genetic discovery. Instead of the gene's messengers (RNA) creating proteins that enhanced the petunias' color, some petunias lost all their color altogether.

The research inspired by his failed petunia experiment led to the discovery of tiny bits of messenger RNA called siRNA that can naturally interfere with gene expression in a biological process called RNA interference (RNAi). Researchers have been studying ways to harness RNAi to control the production of proteins and alter the course of disease ever since.

What's hereditary transthyretin amyloidosis?

Transthyretin (TTR) is a protein produced in the liver that is a carrier of vitamin A. In some patients, inherited genes cause the production of mutated TTR that results in amyloid proteins building up in tissue and vital organs, including the heart.

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Over time, amyloid buildups can damage peripheral nerves and organs, leading to neuropathy and oftentimes death. Globally, about 50,000 people have hereditary amyloidosis and on average, patients pass away from their disease within 2.5 to 15 years after the onset of symptoms.

A treatment breakthrough

Alnylam's patisiran may soon become the standard of care in treating hereditary transthyretin amyloidosis in patients with widespread neuropathy.

In phase 3 trials, patisiran significantly reduced the progression of neuropathy and it improved patients' quality of life. Specifically, 225 patients were enrolled in a study comparing patisiran to placebo. Patients were treated for 18 months and patients receiving patisiran experienced a highly significant reduction in neuropathy versus placebo, as measured by a composite neuropathy score, with a p-value of 0.00001. Patients also experienced an improvement in the quality of life as measured by a questionnaire.

Despite worry over safety risks associated with interfering with RNA, patisiran's safety profile doesn't appear to raise a lot of eyebrows. The rate of adverse events in the patisiran and placebo arms was similar (96.6% and 97.4%, respectively), as was the rate of serious adverse events (36.5% and 40.3%, respectively).

What's next

Alnylam is partnered up with global pharmaceutical giant Sanofi (NYSE: SNY) on patisiran. Alnylam plans to file for patisiran's approval in the U.S. and Europe later this year and early next year, respectively. Meanwhile, Sanofi's planning to file for approval next year in Japan and other countries where it has licensing rights.

If patisiran wins approval, it could produce hundreds of millions of dollars in revenue per year. More importantly, an approval adds conviction that siRNA research may be able to transform how we treat many other diseases. Given that backdrop, patisiran's success could be game-changing.

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Todd Campbell has no position in any of the stocks mentioned. His clients may have positions in the companies mentioned. The Motley Fool owns shares of and recommends Alnylam Pharmaceuticals. The Motley Fool has a disclosure policy.