The initiation of the Phase 1 oncology trial for Kymera Therapeutics' MDM2 degrader KT-253 is a significant milestone in the drug's development. This news could positively impact the company's stock price as it demonstrates progress in their pipeline and brings them closer to potential regulatory approval and commercialization of the drug. However, the impact may be limited in the short term as the trial is still in its early stages and the outcome is uncertain.