The NECTAR study is a multicenter, open-label, randomized phase II clinical trial designed to evaluate a neoadjuvant treatment strategy in patients with localized upper tract urothelial carcinoma (UTUC).

In this study, eligible participants will be randomly assigned to receive either neoadjuvant treatment with toripalimab plus the investigational drug 9MW2821 followed by radical nephroureterectomy with or without lymph node dissection, or upfront radical nephroureterectomy with or without lymph node dissection as standard of care. The purpose of the study is to compare the pathologic response at the time of surgery between the two treatment approaches and to assess treatment safety.

Participants will be monitored throughout treatment and follow-up for treatment response, adverse events, and other clinical outcomes. The information obtained from this study may help improve future treatment strategies for patients with localized UTUC.

Inclusion Criteria:

• Adults aged 18 to 80 years, male or female.
• Histologically confirmed upper tract urothelial carcinoma (UTUC) involving the renal pelvis and/or ureter, with predominant (≥50%) urothelial histology.
• Treatment-naïve, non-metastatic disease (M0) with clinical stage T1-T3, as determined by imaging.
• Eligible for and willing to undergo radical nephroureterectomy with or without lymph node dissection.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
• Adequate hematologic, hepatic, renal, and cardiac function as defined by the protocol.
• Availability of tumor tissue for biomarker analyses.
• Ability to understand and willingness to sign a written informed consent document.

Exclusion Criteria:

• Prior systemic anti-tumor therapy for urothelial carcinoma, except for intravesical therapy for non-muscle-invasive disease.
• Prior treatment with a programmed cell death 1 (PD-1) inhibitor, programmed cell death ligand 1 or 2 (PD-L1/L2) inhibitor, cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitor, or antibody-drug conjugate.
• Evidence of metastatic disease (M1) or regional lymph node involvement of N2 or higher.
• Prior systemic anticancer therapy, including investigational agents, within 3 years prior to study enrollment.
• Prior radiotherapy to the bladder or upper urinary tract.
• Active autoimmune disease requiring systemic treatment.
• Active or uncontrolled infection, including known active hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV) infection, or active tuberculosis.
• Receipt of a live or live-attenuated vaccine within 30 days prior to the first dose of study treatment.
• History of allogeneic tissue or solid organ transplantation.
• Uncontrolled diabetes mellitus, defined as hemoglobin A1c ≥8%, or hemoglobin A1c ≥7% to <8% with associated diabetes-related symptoms.
• Clinically significant cardiovascular disease or thromboembolic events that, in the investigator's judgment, would increase study risk.
• Ongoing peripheral sensory or motor neuropathy of Grade 2 or higher.
• Known psychiatric disorder or substance abuse that would interfere with study participation or compliance.
• Pregnancy or breastfeeding.
• Any other condition that, in the investigator's judgment, would make the participant unsuitable for the study.

Individual participant data (IPD) sharing has not been determined at this time. Decisions regarding IPD sharing will be made in accordance with applicable regulations, institutional policies, and sponsor agreements.