A German court granted an injunction banning sales of Merck (MSD)'s "Keytruda subcutaneous (SC) formulation." An injunction is separate from the main lawsuit, but the product cannot be sold in Germany until a ruling is issued. On the news, Alteogen, whose shares had risen as much as 84% from early this year, plunged 15% on the 5th in a single day.
However, unlike foreigners and institutions who sold Alteogen for two straight days, retail investors were net buyers of about 270 billion won during the period. Retail investors are increasingly wondering, "Is now the entry timing?"
If you are considering investing in Alteogen, there are three short-term points to check. ▲ The impact of the sales ban on Alteogen's earnings ▲ The direction of the MSD–Halozyme patent dispute ▲ The possibility that the injunction that began in Germany will spread across Europe.
First, to understand this patent war, you need to understand the competition over SC formulation technology involving Alteogen, MSD, and Halozyme. For a long time, Halozyme has dominated the market for converting intravenous (IV) drugs to SC form through its proprietary SC formulation technology, Enhanze. Alteogen challenged this by unveiling its self-developed platform technology, Hybrozyme.
In this competitive landscape, global drugmaker MSD chose the enzyme substance ALT-B4, developed on Alteogen's Hybrozyme platform. Based on this, MSD is converting the immuno-oncology drug "Keytruda" from IV to SC. When the formulation is switched, the administration time, which used to take more than 30 minutes, is shortened to 1–2 minutes, and a major advantage is that the key patents for the IV formulation of Keytruda, which begin to expire sequentially from 2028, can be extended by securing the SC formulation.
In response, Halozyme is waging a patent war with MSD, which applied Alteogen's formulation technology. MSD filed patent invalidation proceedings in the United States, Europe and elsewhere, saying "Halozyme's patents are overly broad and the patents themselves are invalid." Halozyme, on the other hand, filed patent infringement suits and sought sales injunctions, saying MSD's Keytruda SC formulation infringes its technology.
How might the patent suits conclude? First, we need to review the patent infringement suit in Germany.
Brokerages said the damage to Alteogen from the injunction would likely be limited. Kim Seon-a, an analyst at Hana Securities, said, "Europe accounts for 17% of MSD Keytruda's sales, and Germany is about 2% of that," adding, "European approval for SC formulation sales is also after Nov. 2025, so the real sales hit to Alteogen is at most 7.7% combined for 2025 and 2026."
The outcome of the suits is expected to take shape as early as the first half of next year. In the brokerage community, the preliminary opinion from the German patent court on whether there is "patent infringement" could come as early as Feb.–Mar. 2026, and the final decision in the patent dispute (PGR) at the U.S. Patent Trial and Appeal Board (PTAB) over patent invalidity is expected around June 2026.
Some say Halozyme's patents could be invalidated, given that the Institution Decision in the U.S. PGR has already presented a view favorable to Merck and Alteogen.
The company also assessed that the likelihood of the German injunction spreading across Europe is low. Vice President Jeon Tae-yeon of Alteogen said at the shareholders meeting the previous day that "the possibility of successive injunctions in major European countries is low," and analyst Kim also said, "Germany is a country where injunctions are comparatively easier to obtain, so the risk of expansion to other countries is smaller than feared."
In the long term, the key issue is the competitiveness of Alteogen's SC formulation technology rather than the outcome of this patent infringement suit. Even when Halozyme's PGR was cited as a representative risk in the past, analyst Lee Ji-su of DAOL Investment & Securities said, "Alteogen has not completely eliminated legal risks such as patent disputes, but it is proceeding without interruption with follow-up license-out (L/O) discussions with global drugmakers such as AstraZeneca," adding, "ALT-B4's technical differentiation and the stability of its clinical and business development are being highly recognized."
For investors wary of volatility, an indirect investment via an active ETF is also possible. Samsung Asset Management's "KoACT Bio-Healthcare Active ETF" has risen 73% from early this year and holds ABL Bio at 16.88% and Alteogen at 10.15%. The strategy manages risk by rebalancing out of less attractive names, while increasing weights when clinical momentum or pipeline expectations grow.