A Study to Evaluate the Safety, Tolerability, Pharmacokinetics, Efficacy and Indications of RP903

Inclusion Criteria:

• Agreement to provide fresh or archived tumor tissue sample within 3 years

• Ia (dose escalation phase and dose expansion phase):patients with pathologicallyconfirmed advanced Malignant solid tumour who have experienced Treatment failure,are unable to tolerate standard treatment, or have no standard treatment

• Ib: Patients with advanced malignant solid tumours who have PIK3CA activatingmutations, experience treatment failure, are intolerant to standard treatment, orhave no standard treatment

• Phase Ia: Solid tumour, not limited to specific types; dose expansion phase willprioritize cervix carcinoma, endometrial cancer, ovarian cancer, and breast cancer.

• Phase Ib:Cervix carcinoma (Expanded Cohort 1)：Having received first-line (includingPlatinum-based chemotherapy ± bevacizumab) or second-line treatment and havingdisease progression during or after treatment; (recurrence during or within 12months after neoadjuvant or adjuvant treatment in previous treatment will beregarded as one treatment line)

• Phase Ib:Endometrial cancer (extension cohort 2)：Progression during or afterfirst-line (including platinum) or second-line treatment of advanced or metastaticdisease; (recurrence during or within 12 months after neoadjuvant or adjuvanttreatment in previous treatment will be considered as one treatment line)；Sarcomatype not included

• Ovarian cancer (expanded cohort 3) (PIK3CA mutation)：

• Ovarian cancer, fallopian tube cancer, or primary peritoneal carcinoma who haveexperienced treatment failure or are intolerant to at least one line of cytotoxictherapy ± PARP inhibitor; (recurrence during or within 12 months after neoadjuvantor adjuvant therapy will be considered one line of therapy)

• Pathological types include high-grade serous carcinoma, clear cell carcinoma, orEndometrioid carcinoma

• Breast cancer (extension cohort 4) (PIK3CA mutation)：

• Advanced, recurrent and metastatic breast cancer;

• Prior systemic treatment in at least 1 line and no more than 3 lines (patients whohave relapsed during or within 12 months after completion of neoadjuvant/adjuvantendocrine therapy will be considered as one line of endocrine therapy)

• At least one measurable lesion as per RECIST v1.1 (except the dose-escalation phaseof monotherapy)

• Eastern Cooperative Oncology Group (ECOG) performance status score: 0-1

• Adequate hematologic and organ function

Exclusion Criteria:

• Patients with known allergy to any component of RP903

• Previously treated with PI3K, mTOR or AKT inhibitors

• Systemic anti-tumor therapy within 4 weeks prior to the first dose

• Presence of leptomeningeal or meningeal metastasis, or presence of signs ofcarcinomatous Meningitis

• Metastases to bone marrow

• Child-Pugh grade B or C

• Active hepatitis B or C

• History of type I Diabetes mellitus，gestational diabetes or uncontrolled type IIDiabetes mellitus