Merck Drops Sutro-Partnered IL-2 Drug in Pipeline Review
By Dr. Zubair Khalid, DVM, MS, PhD ·

Merck & Co. has ended development of an IL-2 agonist partnered with Sutro Biopharma, citing a routine pipeline prioritization. The drug was being tested for solid tumors.
The decision was announced without specific details on clinical data or timelines. Merck described the move as a standard portfolio review, not a reflection of safety or efficacy concerns related to the program.
Context
IL-2 agonists are a class of immunotherapies designed to stimulate the immune system to attack tumors. Several companies have pursued modified IL-2 molecules to improve tumor targeting while reducing systemic toxicity. Merck's decision to drop this candidate adds to a pattern of large pharmaceutical companies reassessing early-stage immuno-oncology assets amid a competitive landscape.
Source: original report