Seo Jin-seok faces defining test at Celltrion

Celltrion's near-term outlook looks solid. The Korean biosimilar giant has just posted its strongest annual earnings on record, underscoring the resilience of its core portfolio. But beyond the upbeat numbers lies a more consequential test. Seo Jin-seok, the 42-year-old CEO and eldest son of founder and Chair Seo Jung-jin, must now prove he can drive Celltrion's next growth engine by advancing its new drug pipelines and expanding its global footprint.

In January, Seo stepped onto the main stage at the JPMorgan Healthcare Conference in San Francisco without his father for the first time. Addressing hundreds of global investors and pharmaceutical executives, he declared that Celltrion is entering a new phase, aiming to launch more than 40 biosimilars by 2038 and submit up to 16 investigational new drug applications over the same period — an ambitious road map that will define his leadership.

Seo has a research and development-focused educational background. He graduated with a bachelor's degree in animal resources from Seoul National University's College of Agriculture and Life Sciences. He earned his master's and a doctorate in biological sciences at KAIST.

After joining Celltrion in 2014, Seo took on his first leadership position as the CEO of Celltrion Skincure in 2017. After being promoted to a senior vice executive president in 2021, he took on the role of leading Celltrion's product development unit. He eventually became CEO of Celltrion and chair of the board at the end of 2023, as Celltrion merged with Celltrion Healthcare.

Seo's education and corporate experience in R&D is what makes him a nontraditional CEO, according to industry watchers.

"(Seo) does not have a (master of business administration) or any experience in legal, (investment banking) or financial sectors," said a biopharmaceutical industry official. "His expertise is rooted in R&D, which is crucial for a company like Celltrion in the long term. New biosimilar products will determine Celltrion's future success and Seo knows the development process of a new drug."

Some investors have questioned Seo's ability as a CEO who must strive to expand revenue and bolster profit for the firm, as he came up short when put in the position to turn around Celltrion Skincure's operating loss during his 3 1/2 years there as the top decision-maker.

However, Seo seemed to have learned from the experience, as he reflected on his time at Celltrion Skincure in a meeting with reporters on the sidelines of the JPMHC.

"It was fun, but it was tough, and depending on how you look at it, I had the worst performances in career," he said about that time.

"I know I'm not the sales king or very good at sales. I'm a supporting role and there are sales kings. I needed to wisely select those superstars and give them roles while there were places in value chains where I could have made a little more investment to support them. I should've figured these out and known these points, but when I went to (Celltrion Skincure), I wanted to be the one. If I were to go back, I would have picked a good sales head and given them some time."

Seo smiled like a child talking about new drugs in development and their pipelines, saying he finds pleasure in studying new drugs and that he had established a team to select biosimilar products.

"There are trends in new drugs development," he said. "I can't say that I understand every trend, but there are members who understand trends and when they work together to draw dots, most trends actually end up following the dots."

As Seo Jin-seok further cements his role as Celltrion's next leader, he faces a far more complex challenge than pipeline execution: ownership.

Celltrion's control structure remains firmly in the hands of his 68-year-old father, Chair Seo Jung-jin, who founded the company in 1991 and drove its rapid ascent. Chair Seo owns 98.13 percent of Celltrion Holdings, the unlisted holding company that in turn holds a 24.7 percent stake in Kospi-listed Celltrion. Separately, he directly owns 4.03 percent of Celltrion, or roughly 9.3 million shares. Celltrion itself controls 54.81 percent of Kosdaq-listed Celltrion Pharm.

By contrast, Seo Jin-seok holds just 5,864 shares in Celltrion — well below a 1 percent stake — an almost negligible holding relative to other major shareholders.

The scale of the inheritance hurdle is daunting. Chair Seo's stake in Celltrion Holdings is valued at between 10 trillion won ($6.9 billion) and 11 trillion won. Under Korea's 50 percent inheritance tax rate for estates exceeding 3 billion won, roughly 5 to 6 trillion won could be owed in taxes. In 2023, Chair Seo publicly acknowledged that succession would be "practically impossible" under the current tax regime.

A securities analyst noted that Seo Jin-seok's minimal ownership could leave him vulnerable if business conditions deteriorate. "His almost nonexistent stake in Celltrion could put him in a tough spot if the company undergoes rough financial outcomes," the analyst said. "He will have to earn and maintain the trust of shareholders and investors to solidify his position."

Celltrion has carried out aggressive share buybacks and cancellations in recent years, which the company says are aimed at boosting shareholder value. While such moves increase Chair Seo's relative ownership, market watchers argue they do little to ease the inheritance tax burden and are unlikely to materially change the succession equation.

Adding another layer of uncertainty is Seo Jin-seok's younger brother, Seo Jun-suk, who is four years his junior. He currently oversees Celltrion's North American operations and recently appeared alongside their father at the opening ceremony of the company's newly acquired biopharmaceutical plant in Branchburg, New Jersey. Like his brother, he holds no meaningful stake in Celltrion.