Merck & Co. invests in Kelun bispecific ADC, exits CLDN18.2 program

Merck & Co. is once again refining its antibody-drug conjugate (ADC) partnership with Sichuan Kelun-Biotech Pharmaceutical. This time, Merck has chosen to license the bispecific ADC candidate SKB571, while relinquishing rights to another asset targeting CLDN18.2. The two companies initially formed a partnership in 2022, granting Merck overseas development rights to the TROP2-targeting ADC asset MK-2870 (SKB-264) for a potential sum exceeding $1.4 billion. Merck later invested an additional $175 million in an expanded collaboration that could potentially bring Kelun over $9 billion. Despite committing to ADCs via a substantial $22 billion deal with Daiichi Sankyo late last year, Merck decided to stop developing two preclinical therapies with Kelun. Now, the partnership with the Chinese biotech is being fine-tuned once more.

In a recent half-year results announcement, Kelun disclosed that Merck has opted to proceed with SKB571 for a payment of $37.5 million. According to Kelun, this program is primarily aimed at treating solid tumors such as lung and gastrointestinal cancers. The company stated that the bispecific antibody molecules are designed through a scientific selection of target combinations and a differentiated approach to enhance tumor targeting and help overcome tumor heterogeneity, thereby improving efficacy. Preclinical studies of SKB571 have shown promising anti-tumor efficacy and a good safety profile in several patient-derived xenograft models and cynomolgus monkeys. Kelun plans to submit an investigational new drug (IND) application for this bispecific ADC in the near future.

Simultaneously, Merck has returned global rights to Kelun's CLDN18.2-directed ADC candidate, SKB315. Kelun reported that early-stage clinical data for SKB315 have demonstrated positive efficacy and an acceptable safety profile in gastric cancer (GC) patients with high CLDN18.2 expression. The company intends to present these findings at upcoming conferences. Kelun is optimistic about the market prospects of SKB315 in China, given the significant number of GC patients in the country. They are committed to accelerating the development of SKB315 in China and exploring possibilities for expanding into international markets.

These updates to the Kelun-Merck collaboration come at a time when the broader immuno-oncology (I-O) landscape appears to be slowing down. Recently, Roche merged its I-O unit into a broader oncology group following a series of setbacks for TIGIT inhibitors, indicating a shift in the I-O sector.