Monte Rosa Therapeutics Inc

Item 5. Other information

Development Progress Update for MRT-6160

On May 9, 2024, we announced additional results from completed preclinical 28-day GLP toxicology studies of MRT-6160 in rats and non-human primates, or cynomolgus monkeys. The data demonstrated a highly favorable safety profile for MRT-6160 with no observable adverse effect level, or NOAEL, in cynomolgus monkeys of approximately 600-fold over predicted human efficacious exposure and in rat of approximately 1000-fold over predicted human efficacious exposure, including with no significant changes in peripheral immune cell compartments in cynomolgus monkeys, no impact on bone marrow, peripheral hematopoietic cells counts, GI tract, and no off-targets identified in in-vitro safety profiling, no genotoxicity, phototoxicity, or hERG activity. Studies also demonstrated robust VAV1 degradation and recovery in both low dose (0.5mg per kg per day) and high dose (30mg per kg per day) groups in cynomolgus monkeys.

Rule 10b5-1 Trading Plans

During the fiscal quarter ended on June 30, 2024, none of our directors and officers (as defined in Rule 16a-1(f) under the Exchange Act)adopted, modified orterminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as those terms are defined in Item 408(a) of Regulation S-K.