Repligen Corp. /zigman2/quotes/210324360/composite RGEN -3.93% announced Friday an agreement to buy privately-held filtration company Spectrum Inc. for about $359 million. Under terms of the deal, Repligen will pay $120 million in cash and 6.154 million shares of its stock, which represents about 18% of the shares outstanding. Repligen expects the deal to be completed during the third quarter of 2017, and add $17 million to $18 million to Repligen's 2017 revenue. The deal is expected to add to earnings in 2018. "This is a pivotal transaction for Repligen that meets all of our acquisition criteria and is a major step forward in building Repligen as a global leader in bioprocessing and achieving our long term financial goals," said Repligen Chief Executive Tony Hunt. The stock, which was still inactive in premarket trade, has rallied 30% year to date, while the S&P 500 /zigman2/quotes/210599714/realtime SPX -0.80% has gained 8.7%.