Acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) are highly heterogeneous myeloid malignancies where few effective targeted therapies are available. While venetoclax has significantly advanced the treatment landscape, therapeutic resistance remains a critical challenge. Consequently, patients with relapsed or refractory (R/R) AML/MDS face a profound unmet medical need for novel therapeutic options. PBSS1113 has demonstrated robust anti-leukemic activity in both in vitro and in vivo models, alongside an acceptable safety profile in a Phase I study. This Phase Ib/II trial will evaluate the safety, tolerability, pharmacokinetics (PK), and preliminary efficacy of PBSS1113 in combination with azacitidine for treatment-naive unfit AML, R/R AML, and higher-risk MDS populations.