This is a multicenter, open-label study to assess the safety and preliminary efficacy and to determine the maximum tolerated dose (MTD) or maximum administration dose (MAD) and recommended Phase 2 doses (RP2D) of PRJ1-3024 in subjects with relapsed/refractory solid tumors. The study consists of two parts, one is a 3+3 dose escalation study and another is a pharmaceutical extension of RP2D.

Using dose escalation, the study will evaluate the safety, tolerability, PK, and pharmacodynamics of PRJ1-3024 and will determine the maximum tolerated dose in subjects with advanced solid tumors.

Participants with advanced solid tumor will receive PRJ1-3024 daily as an oral therapy and test the impact of of PRJ1-3024 on tumors.

This study will find the safe and tolerable recommended dose in subjects with advanced solid tumors in a open-label, 3+3 dose escalation study and use the RP2D to assess the preliminary efficacy of PRJ1-3024 in a long-term extension study.

- Key Inclusion Criteria:

• Histologically or cytologically confirmed locally advanced (unresectable) or metastatic r/r solid tumors for which no standard therapy is available or for whom standard therapy is considered unsuitable or intolerable.
• Male or non-pregnant, non-lactating female subjects age ≥18 years.
• ECOG Performance Status 0~1.
• Has at least 1 measurable lesion as defined by RECIST 1.1 criteria .
• Life expectancy of >3 months, in the opinion of the Investigator.
• Able to take oral medications and willing to record daily adherence to investigational product.
• Adequate hematologic parameters unless clearly due to the disease under study.
• Adequate renal and hepatic function
• Able to understand and willing to sign a written informed consent form.

Key Exclusion Criteria:

• History of another malignancy
• Known symptomatic brain metastases requiring >10 mg/day of prednisolone.
• Significant cardiovascular disease.
• Known active HBV, HCV, AIDS-related illness.
• Has received a live vaccine within 30 days.
• History of active autoimmune disorders, or ongoing immunosuppressive therapy or ongoing .
• Continuance of toxicities due to prior radiotherapy or chemotherapy agents that do not recover to < Grade 2.
• Receiving concurrent anti-cancer therapy, investigational product, strong inhibitors or inducers of cytochrome P450 3A (CYP3A) .
• Prior treatment with hematopoietic progenitor kinase 1 (HPK1) inhibitors.