Pharmaceutical giant Roche Holding said Tuesday it would buy the U.S. gene therapy company Mirus Bio Corp. for US$125 million (79 million euros).

The Madison, Wisconsin-based company is developing RNAi, or gene silencing, a technology that uses mechanisms within the body to target and "turn off" certain genes associated with cancer and other diseases.

Shares in Roche were down 0.23 percent at 170.60 Swiss francs (US$167.00; 105.31 euros) in Zurich.

Roche said it would maintain a RNAi research site in Madison after the takeover. The move is expected to be completed during the second half of this year, Roche said.

Last year, Roche acquired rights for the gene-silencing technology of Biotechnology company Alnylam Pharmaceuticals Inc. as part of a deal potentially worth US$1 billion (630 million euros).