FILE PHOTO - The logo of Swiss pharmaceutical company Roche is seen outside the Shanghai Roche Pharmaceutical Co. Ltd. headquarters in Shanghai May 22, 2014. REUTERS/Aly Song

(Reuters) - Swiss drugmaker Roche Holding AG is nearing a deal to acquire U.S. biotechnology company Spark Therapeutics Inc, the Wall Street Journal reported on Saturday, citing people familiar with the matter.

The deal for Spark could be announced Monday, if not sooner, at a price tag of nearly $5 billion, but could still fall through, the Journal said, citing the unidentified sources. Spark’s market value was just under $2 billion at Friday’s market close.

The newspaper reported there was at least one other unidentified bidder for Spark as of Friday.

Officials with Roche and Spark said their companies do not comment on market rumors.

Spark is a gene therapy company with a pipeline of potential products targeting blindness, hemophilia and neurodegenerative diseases.