Paris-based drugmaker Sanofi said it will be paying $700 million for the drugs as well as a 12% stake in Alnylam Pharmaceuticals Inc, Bloomberg reported. The deal will with the Cambridge, Massachusetts-based biotechnology company will enable Sanofi to grow its investments in therapies for uncommon genetic illnesses.

The Genzyme unit of the French drugmaker will have greater access to patisiran, a drug developed by Alnylam to treat a rare life-threatening condition that can impair the nervous system because of the deal. It will also give the development and marketing rights of three other drugs to Sanofi. In addition, the drugmaker will also have an option on all the drugs targeted for rare genetic diseases that will be developed by Alnylam.

The transaction will bolster the investments of Sanofi in rare diseases which largely revolved around its acquisition of Genzyme in 2011 for a price tag of $20.1 billion, the report said. Citing figures from London- based market research firm Evaluate Ltd, the report said the market treatments seeking to cure rare diseases is expected to increase from $83 billion in 2012 to $127 billion by 2018. The growth rate is two times the rate of the pharmaceutical industry.

Bloomberg reported that Alnylam has no approved products to date. Its revenue for 2012 was pegged at $67 million. The average of two estimates taken by Bloomberg showed that Alnylam could get sales of $1.1 billion by 2020, the report said.

Alnylam's products are made so that they hinder RNA or ribonucleic acid and can turn off the genes that allow over-producing proteins to cause some illnesses.

In 2012, Sanofi and Alnylam forged a partnership that would develop and sell patisiran in Japan and the Asia-Pacific. Patisiran is an experimental therapy for transthyretin-familial amyloid polyneuropathy, the report said. The statement said Sanofi will take care of selling the drugs outside North America and Western Europe.