This is an open-label, multicenter, Phase 1a/1b study evaluating the theranostic pair 64Cu-PD-32766 Injection (PD-32766D) and 225Ac-PD-32766 Injection (PD-32766T) in adult patients with relapsed or refractory Carbonic Anhydrase IX (CA9)-expressing clear cell renal cell carcinoma (ccRCC). The primary objective is to evaluate the safety and tolerability of PD-32766T, and to characterize its pharmacokinetics and preliminary antitumor activity.

Participants will first undergo imaging with PD-32766D to assess CA9 expression. Subjects with positive tumor uptake will be eligible to receive PD-32766T. In Phase 1a, PD-32766T will be administered in an escalating dose levels and schedule determined according to protocol and Safety Review Committee recommendations.

In Phase 1b, participants will receive PD-32766T at the recommended dose and schedule identified from Phase 1a to further evaluate safety, tolerability, and preliminary efficacy.

A total of up to 60 participants will be enrolled in the study.

Inclusion Criteria:

1. Male or female participants aged ≥18 years.

2. Participants with confirmed diagnosis of ccRCC will be included based on the following characteristics:

   • Histological confirmed locally advanced, unresectable, or metastatic ccRCC, after all available standard therapy.
   • Presence of evaluable disease by Response Evaluation Criteria In Solid Tumors (RECIST) guideline (defined by RECIST v1.1).

3. Presence of positive tumor uptake

4. Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 to 1.

5. The participant's with adequate organ function

6. Life expectancy of at least 12 weeks as assessed by the Investigator.

Exclusion Criteria:

1. Concurrent serious (as determined by the Investigator), uncontrolled medical conditions, or life-threatening or other significant comorbid conditions.
2. Any chemotherapy, radiotherapy, immunotherapy, major surgery, biologic, investigational or hormonal therapy for treatment of solid tumors within 28 days.
3. Participants who have not had resolution of clinically significant toxic effects of prior systemic cancer therapy, surgery, or radiotherapy.
4. Administration of a radiopharmaceutical with therapeutic intent within a period of 6 months.
5. Any previous CA9 targeting treatment.
6. Known hypersensitivity to the active substance or to any of the excipients of the PD-32766D and or T.
7. Clinically unstable CNS tumor at the time of screening.
8. History of bowel perforation or bowel infarction, history of active stomach or duodenum ulcer or fistula in the last 2 years, history of gastroesophageal reflux disease or enterocolitis Grade ≥3 according to NCI-CTCAE and/or known active gastrointestinal infection, any unresolved prior radiation-induced gastrointestinal injury.
9. Acute infection requiring IV antibiotics, antivirals, or antifungals within 14 days prior to the initiation of treatment (oral treatment are allowed).
10. Pregnant or breastfeeding women.
11. Known active infection with human immunodeficiency virus (HIV), hepatitis C virus (HCV), or hepatitis B virus (HBV).
12. Have been diagnosed with another primary malignancy.
13. Have significant, uncontrolled, or active cardiovascular disease
14. Bladder outflow obstruction or unmanageable urinary incontinence.
15. Inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis).
16. Any major surgery within 12 weeks before enrolment.
17. History of psychiatric illness or social situations likely to interfere with ability to comply with protocol required assessment or give informed consent.