Stocks of biotechnology firm Celltrion and its subsidiaries -- Celltrion Healthcare and Celltrion Pharm -- often called the “Celltrion trio,” were mixed Monday over a merger plan announced late last week.

Celltrion Pharm, which runs sales operations for chemical and biosimilar drugs produced by Celltrion, saw its stock soar 19.55 percent to 123,500 won ($105.20) in the morning trading session, while Celltrion Healthcare’s stock jumped 8.32 percent to 95,000 won in intraday trading.

Celltrion Healthcare is an overseas sales affiliate of drug manufacturer Celltrion. The biosimilar drug producer’s stock grew 4.26 percent to 269,500 won early in the morning.

Celltrion shares, however, closed at 255,000 won, down 1.35 percent, while Celltrion Healthcare remained flat at 87,700 won. Celltrion Pharm closed up 6.68 percent to 110,200 won.

After the stock market closed Friday, the drug producer announced that it would carry out a merger between Celltrion Holdings and a newly launched holding company, named Celltrion Healthcare Holdings, in a move to streamline the ownership structure.

Celltrion group chairman Seo Jung-jin effectively controls Celltrion and Celltrion Pharm via Celltrion Holdings. The CEO also owns a controlling stake of Celltrion Healthcare.

The planned merger is expected to help absolve the pharmaceutical businesses of unfair trading among Celltrion affiliates.

According to the plan, the new holding company will be merged with Celltrion Holdings, likely sometime next year.

“With the merger, the Celltrion group will be able to cut costs as development, production, distribution and sale of drugs can be all done under one business entity, and to improve management transparency,” said Lee Dal-mi, an analyst from SK Securities.

(wone0102@heraldcorp.com)