A Study to Evaluate YF550 in Participants With Locally Advanced or Metastatic Solid Tumors.

This study consists of two parts: Phase Ia (dose escalation) and Phase Ib (dose expansion), with each treatment cycle lasting 21 days. Up to 84 participants will be enrolled in Phase Ia and up to 120 participants in Phase Ib. The primary objectives of Phase Ia are to determine the dose-limiting toxicities (DLTs), maximum tolerated dose (MTD), and recommended dose for expansion (RDE) of YF550. The primary objective of Phase Ib is to evaluate the antitumor activity of YF550 in participants with locally advanced or metastatic solid tumors. Blood samples will be collected from participants in both Phase Ia and Phase Ib to assess the pharmacokinetics (PK) of YF550.