Keba Biological (Jiangsu) Co., Ltd.

Part A: Phase I Monotherapy Bridging ±SOC - Permissible Sub-cohort: Evaluate the safety and tolerability of SPX-303 monotherapy in Chinese cancer patients, observe the occurrence of dose-limiting toxicities (DLT), determine the maximum tolerated dose (MTD) and recommended Phase II dose (RP2D) for the Chinese population; compare the pharmacokinetic (PK) parameters of SPX-303 in Chinese patients with those from overseas, assess the impact of ethnic factors, and thus complete the bridging data required for extrapolating overseas clinical data to the Chinese population. Simultaneously, conduct preliminary observation of the antitumor activity of monotherapy. After determining the RP2D, SPX-303 can be combined with standard treatment regimens in some patients with specific indications based on inclusion and exclusion criteria to explore the safety and preliminary efficacy signals of combination therapy. Part B (Phase II a SPX-303 and Enhertu Combination Therapy Exploration): Evaluate the safety and tolerability of SPX-303 combined with Enhertu, investigate potential interactions or specific toxicities, and determine the recommended dose or administration route of SPX-303 in the combination regimen. This will provide a basis for selecting appropriate combination strategies for Phase IIb or subsequent studies. Simultaneously, biomarker data will be collected to explore the correlation between efficacy and safety, and early discontinuation rules and cohort expansion triggering criteria will be established to support larger-scale clinical development in the future.