Abstract
Background
Urothelial carcinoma (UC) is a common malignancy with poor prognosis in refractory or metastatic stages. While platinum-based chemotherapy and PD-1 inhibitors have improved outcomes for some, the benefits are limited. Disitamab Vedotin (RC48), an HER2-targeted antibody-drug conjugate, combined with PD-1 inhibitors, has shown promising antitumor activity in advanced UC. This study aims to evaluate the clinical efficacy and safety of RC48 combined with PD-1 inhibitors in previously treated UC patients using real-world data.
Methods
This single-center, retrospective real-world study included 29 patients with mUC who had received prior treatment and were treated with RC48 plus a PD-1 inhibitor between October 2021 and April 2025. Treatment efficacy was assessed according to the Response Evaluation Criteria in Solid Tumours (RECIST 1.1). Primary endpoints were progression-free survival (PFS) and overall survival (OS). Secondary endpoints included objective response rate (ORR) and disease control rate (DCR). Treatment-related adverse events (TRAEs) were recorded and graded according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. Subgroup analyses were conducted based on age, Eastern Cooperative Oncology Group (ECOG) performance status, tumor human epidermal growth factor receptor 2 (HER2) immunohistochemistry (IHC) status, number of metastatic sites, and programmed cell death ligand 1 (PD-L1) expression.
Results
Among 29 included patients, the median age was 67 years, and 69.0% were male. HER2 IHC showed 2+ expression in 51.7% of patients and 3+ expression in 20.7%. The vast majority of patients (93.1%) received ≥4 treatment cycles. The ORR was 34.5%, with a DCR of 96.6%. Disease progression occurred in only 1 patient (3.4%). Median PFS was 14.22 months. In an exploratory preliminary analysis with limited sample size, patients aged ≥65 years, ECOG performance status 0, and HER2 IHC 3+ numerically demonstrated longer PFS. The OS endpoint had not been reached at data cutoff; preliminary survival differences were observed in patients with ≤2 metastatic sites. Regarding safety, TRAEs occurred in 82.8% of patients, primarily peripheral neuropathy (48.28%), anemia (17.24%), and leukopenia (10.34%). Grade ≥3 TRAEs were reported in 6.9% of patients, with no treatment-related deaths recorded. Most adverse events were manageable through dose adjustments or supportive care.
Conclusions
This retrospective real-world study provides preliminary evidence that RC48 combined with PD-1 inhibitors may offer encouraging antitumor activity and a manageable safety profile in relapsed or refractory mUC, with a median PFS of 14.22 months and a high DCR observed in this cohort. Given the exploratory nature of this analysis and the study’s limitations, including the small sample size, single-center design, and lack of a control arm, these findings should be interpreted with caution. Larger prospective studies are warranted to validate these results.
Keywords: Antibody-drug conjugates (ADC), disitamab vedotin (RC48), immune checkpoint inhibitors (ICIs), human epidermal growth factor receptor 2 (HER2), urothelial carcinoma (UC)
Introduction
Urothelial carcinoma (UC) is a common malignancy of the urinary tract, ranking ninth in global cancer incidence, and can originate from the renal pelvis, ureter, or bladder (1). According to GLOBOCAN 2022 data (2), approximately 614,000 new bladder cancer cases and over 220,000 related deaths occurred worldwide, with a continuously rising incidence and mortality. Patients with locally advanced or metastatic UC (la/mUC) have particularly poor prognoses, underscoring the urgent need for innovative therapeutic options (3). Although platinum-based chemotherapy remains the standard first-line treatment, its clinical efficacy is constrained by limited response durability, drug resistance, and cumulative toxicity (4,5). These limitations highlight the importance of developing novel treatment strategies capable of achieving deeper and more sustained tumor control.
From a biological standpoint, human epidermal growth factor receptor 2 (HER2) alterations play a critical role in UC tumorigenesis and progression. Evidence from Chinese cohorts reports a relatively high prevalence of HER2 overexpression, particularly in upper urinary tract UC, where approximately one-third of patients exhibit HER2 positivity (3,6-8). This molecular characteristic supports the rationale for HER2-targeted therapies in selected UC populations. Disitamab vedotin (RC48), a domestically developed HER2-directed antibody-drug conjugate (ADC), delivers the cytotoxic payload monomethyl auristatin E (MMAE) with high precision. Through its bystander effect and potential to induce immunogenic cell death, RC48 not only exerts direct antitumor activity but may also remodel the tumor microenvironment. Previous clinical studies have demonstrated its significant efficacy and manageable safety in heavily pretreated HER2-positive mUC, establishing a foundation for combination therapeutic approaches (9-12). Concurrently, immune checkpoint inhibitors (ICIs) have shown significant clinical efficacy across multiple advanced solid tumors, including UC, and have been established as the standard second-line treatment for mUC (1). Notably, ADC-induced tumor antigen release and tumor microenvironment remodeling can synergize with programmed death-1/programmed cell death ligand 1 (PD-1/PD-L1) pathway inhibition, thereby providing a strong biological rationale and considerable therapeutic potential for the “HER2-ADC plus ICI” combination strategy.
In recent years, clinical outcomes of RC48 in combination with PD-1 inhibitors have been encouraging. One study reported an objective response rate (ORR) of 73.2%, a median progression-free survival (PFS) of 9.3 months, and a median overall survival (OS) of 33.1 months in patients with advanced or mUC treated with RC48 plus toripalimab, accompanied by a manageable safety profile (13). More recently, the RC48-C016 Phase III randomized trial further validated the superior survival benefits of this combination compared with chemotherapy in the first-line setting.
Given the promising biological rationale and early clinical signals, real-world evidence is needed to determine how RC48 combined with PD-1 inhibitors performs in routine clinical practice. Therefore, the present study was conducted to evaluate this combination in a real-world population of patients with locally advanced or mUC. We present this article in accordance with the STROBE reporting checklist (available at https://tau.amegroups.com/article/view/10.21037/tau-2025-1-942/rc).
Methods
Study design and patient selection
This study was a single-center, retrospective real-world cohort study conducted at PLA General Hospital. Patients who received RC48 between October 2021 and April 2025 were screened. All clinical data, imaging results, and adverse event (AE) records were obtained from the electronic medical record (EMR) system. Follow-up assessments continued until July 10, 2025, which served as the final data cutoff. A total of 199 patients who had received RC48 during the study period were screened. Eligibility criteria were based on clinical indications for combination therapy with RC48 and a PD-1 inhibitor. Inclusion and exclusion criteria are shown in Figure 1. After screening, 29 patients met all criteria and were included in the final cohort. Loss-to-follow-up was managed through repeated EMR review and telephone contact; survival status was confirmed through outpatient visits, inpatient records, or direct patient/family communication. This study was conducted in accordance with the Declaration of Helsinki and its subsequent revisions. It has been reviewed and approved by the Medical Ethics Committee of the Chinese PLA General Hospital (Approval No. S2023-121-01). Given the retrospective nature of this study, the informed consent procedure was waived.
Figure 1.
Study flow chart. ECOG, Eastern Cooperative Oncology Group; PD-1, programmed death-1; RC48, disitamab vedotin.
Efficacy and safety assessments
This study adopted the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 as the efficacy assessment framework. The primary endpoints were PFS and OS. Secondary endpoints included ORR and disease control rate (DCR), with the best overall response recorded—classified as complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD). Tumor response was assessed every 6–8 weeks via CT or MRI according to RECIST v1.1 criteria. Imaging data were independently reviewed by two radiologists, with discrepancies resolved through consensus. PFS was defined as the time interval from the first use of the PD-1 inhibitor in combination with RC48 to radiographic disease progression or death from any cause. OS was defined as the time interval from the same starting point to death from any cause. All patients were followed up until July 10, 2025, or death, whichever occurred first. All assessment methods were consistent across patients to ensure comparability of measurements.
In addition to outcome variables, several predictor variables and potential confounders were prespecified based on clinical relevance. Predictor variables included HER2 immunohistochemistry (IHC) status, PD-L1 expression level, eastern cooperative oncology group (ECOG) performance status, number of metastatic sites, baseline tumor burden, age, sex, and prior systemic therapy history. These variables were selected based on their known or suspected association with treatment response or survival outcomes in mUC. As this study is retrospective, the original pathology reports did not detail the HER2 IHC antibody clones used. However, based on a review of relevant literature, we identified the following HER2 detection antibody clones commonly used in current clinical practice and previous studies: 4B5, CB11, and SP3. The IHC assessment criteria for HER2 are as follows: (I) IHC 0: no staining or <10% of invasive cancer cells show incomplete, faint cell membrane staining. (II) IHC 1+: ≥10% of invasive cancer cells show incomplete, faint cell membrane staining. (III) IHC 2+: (i) ≥10% of invasive cancer cells show weak-to-moderate intensity complete membrane staining; (ii) <10% of invasive cancer cells show strong and complete staining. (IV) IHC 3+: ≥10% of invasive cancer cells show strong, complete, and uniform membrane staining.
Potential confounders included age, ECOG performance status, metastatic disease burden, comorbidities, HER2 expression, and prior treatment history. These factors were evaluated as they may independently influence prognosis or alter treatment efficacy.
AEs assessment
The study’s safety monitoring protocol systematically tracked AEs reported by patients at baseline and during each subsequent visit or clinical assessment, as well as those leading to RC48 dose reduction, discontinuation, or interruption. Events were graded according to the Common Terminology Criteria for Adverse Events (CTCAE), version 5.0, a standardized system that facilitates the reporting, assessment, and comparison of AEs across studies and treatment regimens. This rigorous safety monitoring and reporting approach provides valuable insights into treatment tolerability and offers important evidence to inform patient management decisions.
Bias
This study rigorously controlled for bias through the following measures: To minimize selection bias, we prospectively enrolled all patients receiving RC48 treatment during the study period for screening. To minimize information and measurement bias, we implemented three primary strategies: first, two radiologists independently conducted imaging assessments. Second, standardized evaluation criteria were strictly enforced (RECIST v1.1 for efficacy assessment and CTCAE v5.0 for AE documentation). Finally, all subjects followed a uniform follow-up protocol.
Statistical analysis
Clinical and pathological characteristics were summarized using descriptive statistics. Categorical variables were presented as frequencies and percentages, whereas continuous variables were expressed as medians with ranges or means with standard deviations. Categorical variables were compared using the X2 test or Fisher’s exact test, as appropriate. Continuous variables were compared using the Student’s t-test or Mann-Whitney U test, depending on data distribution. Continuous variables were categorized using clinically relevant cutoffs, including age (<65 vs. ≥65 years), number of metastatic sites (≤2 vs. >2), and ECOG performance status (0 vs. 1), based on prior clinical evidence and their prognostic relevance in mUC. The selection of grouping thresholds was based on prior evidence and clinical relevance in prognostic assessment. Survival outcomes were estimated using the Kaplan–Meier method and compared using the log-rank test. Treatment response differences across patient subgroups were explored through subgroup analyses, specifically examining the associations of age, HER2 status, ECOG performance status, number of metastatic sites, and PD-L1 expression with treatment response and survival outcomes. Due to the limited sample size and the small number of outcome events, multivariable regression analyses were not performed to avoid model overfitting. Therefore, subgroup and univariable analyses were considered exploratory. Regarding missing data, due to the extremely low proportion of missing values and their classification as missing at random, no significant bias was observed in the primary outcomes. Therefore, the statistical analysis employed a complete-case approach. All statistical analyses were performed using SPSS software, version 29.0, and RStudio, version 4.5.1. A two-sided P value <0.05 was considered statistically significant.
Results
Patient and treatment characteristics
This study enrolled 29 patients diagnosed with UC, who were treated with RC48 in combination with PD-1 inhibitors (Table 1). The median age of the cohort was 67 years (range: 36–83 years). Male patients represented 69.0% of the cohort, while less than half (41.4%) had a history of smoking. Regarding the ECOG performance status, the majority of patients had a score of 0 (65.5%), indicating overall good health. The bladder was the most common primary tumor site (51.7%), followed by the renal pelvis (27.6%) and ureter (20.7%). Pathological grading revealed high-grade tumors in 82.8% of cases, with 86.2% of patients at stage IV. Furthermore, 55.2% of patients had ≤2 metastatic sites, and 72.9% presented with lymph node metastasis. Metastases were observed in the lungs (37.9%), bones (17.2%), liver (17.2%), and brain (3.4%). Patients’ HER2 IHC status was categorized into three groups: IHC 3+, IHC 2+, and others (the “others” group includes patients classified as IHC 0 and IHC 1+). HER2 IHC results showed that 51.7% of patients were IHC 2+, and 20.7% were IHC 3+. According to standard evaluation protocols, IHC 2+ constitutes an indeterminate result, warranting further FISH testing to confirm HER2 gene amplification. However, as this retrospective real-world study was constrained by contemporary clinical testing capabilities and actual diagnostic workflows, no FISH results were obtained for any IHC 2+ cases in this cohort. Regarding prior treatment history, all patients in this study received RC48 in combination with PD-1 inhibitors as second-line or subsequent therapy. Prior to initiation of RC48 plus ICI therapy, patients had received a median of one prior line of systemic treatment. Among the 29 patients, 20 (69.0%) had previously received chemotherapy, and 12 (41.4%) had received ICI therapy. The most frequently used ICI in combination with RC48 was toripalimab (55.2%). As of the data analysis date, the median follow-up duration for all participants was 16.36 months. Individual follow-up durations ranged from 2.04 to 44.68 months.
Table 1. Patient characteristics at baseline.
| Patient characteristics | Outcome, N=29 |
|---|---|
| Sex | |
| Male | 20 (69.0) |
| Female | 9 (31.0) |
| Smoking | 12 (41.4) |
| Age (years) | |
| Median (range) | 67.0 (36.0–83.0) |
| ≤65 | 12 (41.4) |
| >65 | 17 (58.6) |
| ECOG | |
| 0 | 19 (65.5) |
| 1 | 10 (34.5) |
| Tumor location | |
| Bladder | 15 (51.7) |
| Renal pelvis | 8 (27.6) |
| Ureter | 6 (20.7) |
| Differentiation | |
| High grade | 24 (82.8) |
| Low grade | 5 (17.2) |
| Stage | |
| III | 4 (13.8) |
| IV | 25 (86.2) |
| HER2 status (IHC) | |
| IHC 2+ | 15 (51.7) |
| IHC 3+ | 6 (20.7) |
| Others | 8 (27.6) |
| PD-L1 | |
| Positive | 9 (31.0) |
| Negative | 11 (37.9) |
| Unknown | 9 (31.0) |
| No. of metastatic sites | |
| ≤2 | 16 (55.2) |
| >2 | 13 (44.8) |
| Metastatic sites | |
| Bone | 5 (17.2) |
| Liver | 5 (17.2) |
| Lung | 11 (37.9) |
| Brain | 1 (3.4) |
| Lymph nodes | 21 (72.9) |
| Previous therapies | |
| Chemotherapy | 20 (69.0) |
| ICIs | 12 (41.4) |
| Combination types of ICI | |
| Tislelizumab | 9 (31) |
| Toripalimab | 16 (55.2) |
| Pembrolizumab | 4 (13.8) |
Data are presented as n (%). ECOG, Eastern Cooperative Oncology Group; HER2, human epidermal growth factor receptor 2; IHC, immunohistochemistry; ICI, immune checkpoint inhibitor; PD-L1, programmed cell death ligand 1.
Efficacy
Among the enrolled patients, the majority (93.1%) received at least four cycles of RC48 plus ICI therapy. In addition, 62.1% received more than eight cycles, and two patients (6.9%) received over 20 cycles, both of whom remained on treatment at the time of analysis. The initial RC48 dose was 120 mg per kg in most patients (89.7%) (Figure 2). Following dual-agent combination therapy, efficacy was evaluated in all 29 patients: no CR were observed; 10 patients (34.5%) achieved PR, 18 (62.1%) had SD, and one patient (3.4%) experienced PD. The ORR and DCR were 34.5% and 96.6%, respectively, in the overall cohort. In the HER2-high expression cohort (IHC 2+/3+), the DCR reached 100%, irrespective of PD-L1 status. However, possibly due to the limited sample size, the ORR in HER2-high patients with PD-L1 positivity (33.3%) was comparable to that in PD-L1-negative patients (27.3%). Notably, the mPFS in the HER2-high cohort reached 14.2 months. In the HER2-low or -negative cohort (IHC 0/1+), only three PD-L1-positive patients were available for analysis; therefore, the response estimates in this subgroup (ORR and DCR 100%) should be interpreted with caution and are presented as descriptive, exploratory observations (Table 2, Figure 3). The median baseline total tumor diameter was 49 mm (range, 6.0–180.0 mm), and the best percentage change in the sum of diameters of all target lesions from baseline to analysis ranged from –74.7% to 88.0% (Figure 4).
Figure 2.
Swimming plot showing the RC48 dosage and dose adjustments during treatment, the treatment cycles, and treatment status. RC48, disitamab vedotin.
Table 2. Tumor response with measurable lesions.
| Response | Patients (n=29) | IHC (2+/3+), PD-L1 (+) (n=6) | IHC (2+/3+), PD-L1 (–) (n=11) | IHC (0/1+), PD-L1 (+) (n=3) | IHC (0/1+), PD-L1 (–) (n=0) |
|---|---|---|---|---|---|
| Best response | |||||
| CR | 0 | 0 | 0 | 0 | 0 |
| PR | 10 (34.5) | 2 (33.3) | 3 (27.3) | 3 (100) | 0 |
| SD | 18 (62.1) | 4 (66.7) | 8 (72.7) | 0 | 0 |
| PD | 1 (3.4) | 0 | 0 | 0 | 0 |
| Objective response rate | 10 (34.5) | 2 (33.3) | 3 (27.3) | 3 (100) | NA |
| Disease control rate | 28 (96.6) | 6 (100) | 11 (100) | 3 (100) | NA |
| mPFS (months) | 14.22 | NA | 14.22 | NA | NA |
| mOS (months) | NA | NA | NA | NA | NA |
Data are presented as n (%). CR, complete response; IHC, immunohistochemistry; mPFS, median PFS; mOS, median OS; NA, not available; OS, overall survival; PD-L1, programmed cell death ligand 1; PD, progressive disease; PFS, progression-free survival; PR, partial response; SD, stable disease.
Figure 3.
Sankey diagram illustrating the relationship between HER2 expression levels, PD-L1 status, and best clinical response in patients with metastatic urothelial carcinoma treated with RC48 plus PD-1 inhibitors. ECOG, Eastern Cooperative Oncology Group; HER2, human epidermal growth factor receptor 2; IHC, immunohistochemistry; PD-1, programmed death-1; PD-L1, programmed cell death ligand 1; PR, partial response; RC48, disitamab vedotin; SD, stable disease.
Figure 4.
Cancer response waterfall plot. PD, progressive disease; PR, partial response; SD, stable disease.
In the overall cohort, the mPFS was 14.22 months (Figure 5A). Exploratory subgroup analyses suggest that PFS may differ among patients with distinct clinical characteristics. However, due to small sample sizes and insufficient event numbers, these findings represent preliminary results and require validation in larger-scale studies (Table 3). When stratified by age, patients aged ≤65 years had an mPFS of 7.26 months, whereas the median could not be estimated in patients aged >65 years due to insufficient events; this difference was statistically significant (P=0.045, Figure 5B). ECOG performance status significantly affected prognosis: mPFS was 14.22 months in patients with ECOG 0, whereas it was reduced to 7.26 months in those with ECOG 1 (P=0.03, Figure 5C). Analysis of HER2 status demonstrated that patients with IHC 3+ had an mPFS of 14.22 months, which was significantly longer than the 4.66 months observed in the “others” group (P=0.045, Figure 5D). The median PFS could not be estimated for patients with IHC 2+ due to the limited sample size.
Figure 5.
Kaplan-Meier curves of PFS. (A) Overall PFS Kaplan-Meier curve; (B) patients aged ≤65 and >65 years; (C) patients with ECOG =0 and ECOG =1; (D) patients with different HER2 IHC expression statuses. ECOG, Eastern Cooperative Oncology Group; HER2, human epidermal growth factor receptor 2; IHC, immunohistochemistry; mPFS, median PFS; NA, not available; PFS, progression-free survival.
Table 3. Subgroup analyses of PFS and OS.
| Variable | PFS | OS | |||
|---|---|---|---|---|---|
| mPFS, months | P value | mOS, months | P value | ||
| Age (years) | 0.045* | 0.03* | |||
| ≤65 | 7.26 | 20.3 | |||
| >65 | NA | NA | |||
| Gender | 0.90 | 0.48 | |||
| Male | NA | NA | |||
| Female | 14.22 | NA | |||
| ECOG | 0.03* | 0.19 | |||
| 0 | 14.22 | NA | |||
| 1 | 7.26 | NA | |||
| TNM stage | 0.38 | 0.40 | |||
| III | NA | NA | |||
| IV | 14.22 | NA | |||
| HER2 status (IHC) | 0.045* | 0.09 | |||
| IHC 2+ | NA | NA | |||
| IHC 3+ | 14.22 | NA | |||
| Others | 4.66 | NA | |||
| Tumor location | 0.82 | 0.03* | |||
| Bladder | 14.22 | NA | |||
| Renal pelvis | 8.48 | NA | |||
| Ureter | NA | NA | |||
| No. of metastatic sites | 0.37 | 0.03* | |||
| ≤2 | NA | NA | |||
| >2 | 14.22 | 20.3 | |||
| Metastatic sites | 0.97 | 0.23 | |||
| Lymph node metastasis only | 14.22 | NA | |||
| Visceral metastasis | NA | NA | |||
| Previous chemotherapy | 0.96 | 0.13 | |||
| With | NA | NA | |||
| Without | 14.22 | NA | |||
| Previous immunotherapy | 0.06 | 0.19 | |||
| With | 14.22 | 20.3 | |||
| Without | 8.48 | NA | |||
*, P<0.05, statistically significant. ECOG, Eastern Cooperative Oncology Group; HER2, human epidermal growth factor receptor 2; IHC, immunohistochemistry; mOS, median OS; mPFS, median PFS; NA, not available; OS, overall survival; PFS, progression-free survival; TNM, tumor node metastasis.
The median mOS had not yet been reached in the overall cohort (Figure 6A). Subgroup analysis showed that mOS had not yet been reached in patients aged >65 years, whereas it was 20.3 months in those aged ≤65 years (P=0.03, Figure 6B). The number of metastatic sites was significantly associated with prognosis: mOS had not yet been reached in patients with ≤2 metastatic sites, whereas it was 20.3 months in those with >2 metastatic sites (P=0.03, Figure 6C). Analysis by primary tumor site indicated that the median PFS had not yet been reached for patients with bladder, renal pelvis, or ureteral tumors. However, differences between sites were statistically significant (P=0.04, Figure 6D), with patients with ureteral tumors showing earlier curve decline. But this comparison should also be interpreted cautiously, as it is based on a small sample size and remains exploratory.
Figure 6.
Kaplan-Meier curve for OS. (A) Overall OS Kaplan-Meier curve; (B) patients aged ≤65 and >65 years; (C) patients with ≤2 and >2 metastatic sites; (D) patients with different tumor location. mOS, median OS; NA, not available; OS, overall survival.
Furthermore, to provide a more intuitive illustration of the efficacy of RC48 in combination with PD-1 inhibitors, we present two representative cases:
❖ Case 1: a 64-year-old male with recurrent bladder cancer and lung metastases. He received RC48 in combination with pembrolizumab starting in July 2024 and completed 13 cycles. Imaging assessment after four cycles demonstrated a marked reduction in lung metastases (Figure 7), with a final response of PR and a PFS of 7 months.
❖ Case 2: a 58-year-old male with recurrent bladder cancer and liver metastases diagnosed in August 2022. He received RC48 in combination with toripalimab beginning in January 2024 and completed eight cycles. Imaging review after four cycles demonstrated a substantial reduction in liver metastases (Figure 8), with an objective response of PR and a PFS of 4 months.
Figure 7.
Chest CT of a patient with lung metastases treated to PR. Red arrows: pulmonary lesions. CT, computer tomography; PFS, progression-free survival; PR, partial response; RC48, disitamab vedotin.
Figure 8.
Abdominal CT in a patient with liver metastases treated to PR. Red arrows: liver metastases. CT, computer tomography; PFS, progression-free survival; PR, partial response; RC48, disitamab vedotin.
These representative cases highlight the antitumor activity of the combination regimen in patients who had received multiple prior lines of therapy, consistent with the objective responses and survival benefits observed in the overall cohort.
Safety
In this study (Table 4), 24 patients experienced treatment-related adverse events (TRAEs). The most common AE was peripheral neuropathy, reported in 14 patients (48.28%), all of which were grade ≤3. Other common AEs included anemia (17.24%), leukopenia (10.34%), and rash (10.34%). Additional AEs with lower incidence rates (≤6.9%) included pruritus, elevated alanine aminotransferase/aspartate aminotransferase (ALT/AST), neutropenia, thrombocytopenia, vomiting, nausea, insomnia, elevated creatinine, acute kidney injury, interstitial pneumonia, pleural effusion, immune-mediated myositis, and immune-mediated cystitis. Grade ≥3 AEs occurred at lower frequencies, primarily including rash (3.45%), pruritus (3.45%), elevated ALT/AST (6.9%), neutropenia (3.45%), elevated creatinine (3.45%), and immune-mediated myositis (3.45%). No treatment-related deaths were observed. In addition, four patients required RC48 dose reductions due to peripheral neuropathy (hand-foot numbness). One patient temporarily discontinued RC48 in combination with ICI therapy due to hand-foot numbness, but later resumed the original treatment regimen after disease progression.
Table 4. Summary of treatment-related adverse events.
| Adverse events | Any events, No. (%) | Grade ≥3, No. (%) |
|---|---|---|
| Peripheral neuropathy | 14 (48.28) | 0 (0) |
| Anemic | 5 (17.24) | 0 (0) |
| Leukopenia | 3 (10.34) | 0 (0) |
| Rash | 3 (10.34) | 1 (3.45) |
| Pruritus | 2 (6.90) | 1 (3.45) |
| ALT/AST increased | 2 (6.90) | 2 (6.90) |
| Neutropenia | 1 (3.45) | 1 (3.45) |
| Thrombocytopenia | 1 (3.45) | 0 (0) |
| Vomiting | 1 (3.45) | 0 (0) |
| Nausea | 1 (3.45) | 0 (0) |
| Insomnia | 1 (3.45) | 0 (0) |
| Blood creatinine increased | 1 (3.45) | 1 (3.45) |
| Acute kidney injury | 1 (3.45) | 0 (0) |
| Interstitial pneumonia | 1 (3.45) | 0 (0) |
| Pleural effusion | 1 (3.45) | 0 (0) |
| Immune-mediated myositis | 1 (3.45) | 1 (3.45) |
| Immunological cystitis | 1 (3.45) | 0 (0) |
ALT, alanine aminotransferase; AST, aspartate aminotransferase.
Discussion
Currently, there are four ADC drugs globally that have demonstrated clear efficacy in treating UC, primarily targeting specific markers such as Nectin-4, HER2, and TROP-2. Among these, three drugs have been approved for indications related to UC. Due to their differing targets, these drugs exhibit variations in practical application, including differences in overall efficacy, suitable patient populations, and safety profiles. However, similar to most cytotoxic drugs, the duration of objective response or clinical benefit from ADCs as monotherapy remains limited due to the emergence of resistance mechanisms.
Targeted HER2-ADC is currently one of the key therapeutic agents for HER2-positive UC. RC48 is a novel HER2-targeted ADC that primarily links MMAE to the antibody via a linker. It has previously been approved in China for treating patients with HER2-positive mUC who have experienced at least one prior platinum-based chemotherapy failure. Currently, vedotin has been approved in China for the late-line monotherapy treatment of advanced UC with HER2 overexpression (IHC 2+ or 3+), demonstrating exceptional efficacy (14). This drug features a uniquely designed molecular structure that, through its targeted mechanism of action, not only kills HER2-overexpressing tumor cells but also attacks neighboring tumor cells via a “bystander effect” (15). However, as with most cytotoxic drugs, the duration of objective response or clinical benefit from ADCs as monotherapy remains limited due to the emergence of resistance mechanisms (16,17). Despite high-level evidence-based proof confirming its efficacy and unique suitability for specific patient populations, we still observe limitations with vedicitinumab as a monotherapy. Consequently, combining ADCs with other anticancer drugs has become a significant direction in ADC drug development.
Previous studies have classified the tumor immune microenvironment into three distinct phenotypes based on T-cell infiltration and responsiveness to ICIs: immune-desert, immune-excluded, and immune-inflamed. The first two are collectively termed “cold tumors”, whereas the latter is referred to as a “hot tumor”. Cold tumors are characterized by sparse immune cell infiltration and resistance to immune penetration, whereas hot tumors exhibit abundant infiltration of anti-tumor immune cells, such as T lymphocytes (18,19). The fundamental distinction between cold and hot tumors lies in their responsiveness to immunotherapies, particularly PD-1 inhibitors. ICIs, exemplified by PD-1 inhibitors, block the interaction between PD-1 and PD-L1, thereby relieving tumor cell-mediated suppression of T cells and reactivating the immune system to recognize and eliminate tumor cells. Despite their promising potential, ICIs show limited efficacy against cold tumors because of the paucity of immune cells in the tumor microenvironment, ultimately leading to low response rates. Therefore, converting cold tumors into hot tumors has become a key strategy for overcoming these refractory cancers. Mechanistically, combining PD-1 inhibitors with ADCs exerts dual effects: first, the ICI relieves T-cell suppression; and second, the ADC, carrying a cytotoxic payload, directly kills tumor cells (20).
In the clinical gap where cisplatin-intolerant patients constitute 30–50% of all metastatic mUC cases, RC48 establishes a robust foundation for combination strategies with its breakthrough efficacy demonstrated in the second-line setting: a 51% ORR and mPFS of 6.9 months (10). Its unique MMAE payload induces immunogenic cell death, transiently releasing tumor antigens and reshaping the microenvironment to transform “cold tumors” into highly infiltrated “hot tumors”. Simultaneously introducing a PD-1 inhibitor blocks PD-1/PD-L1 signaling, reversing T-cell exhaustion and amplifying the bystander effect triggered by the ADC, achieving synergistic killing where “1+1>2”. Notably, the combination of ADCs and immunotherapy has achieved landmark progress in UC. For example, enfortumab vedotin (EV) targeting Nectin-4, in combination with pembrolizumab, has received FDA accelerated approval for first-line treatment of locally advanced or mUC in patients ineligible for cisplatin. This combination significantly improves response rates and delivers survival benefits, though it is associated with a characteristic toxicity profile including rash and peripheral neuropathy. In contrast, RC48 combined with PD-1 inhibitors is primarily indicated for HER2-expressing patients. Its safety profile is more closely associated with the MMAE payload, with overall manageable adverse reactions, offering an important complementary option for HER2-positive populations. From ADC monotherapy to combination immunotherapy, and from advanced-line to first-line treatment, vedicitinumab continues to achieve new breakthroughs in UC therapy. Interim data from the ongoing phase III RC48-C016 study demonstrate that this combination regimen as first-line therapy for HER2-positive mUC has met both primary endpoints of PFS and OS. Significant benefits were observed across both cisplatin-eligible and HER2-positive patient cohorts, with manageable adverse reactions. Particularly worthy of further discussion is the recent Phase III study data suggesting that RC48 combined with PD-1 inhibitors may offer superior survival benefits compared to traditional gemcitabine-platinum chemotherapy regimens in first-line treatment of HER2-positive mUC patients. This finding holds significant importance for those intolerant to cisplatin or with limited treatment options (21). Traditional gemcitabine-platinum regimens have long remained the standard first-line treatment for advanced UC, yet their efficacy has limited room for improvement, and some patients cannot tolerate them due to toxicity or comorbidities. Interim results from this phase III trial demonstrate that the combination of HER2-targeted antibody-drug conjugates with immunotherapy achieves dual improvements in PFS and OS in a phase III study. This strategy holds promise for reshaping the landscape of first-line treatment for mUC. Additionally, a global multicenter phase III clinical trial of RC48 in combination with pembrolizumab is currently underway. This trial aims to further validate the efficacy and safety of this regimen and advance its indication expansion on an international scale.
From the perspective of survival outcomes in second-line treatment, current standard therapeutic options for patients with mUC who have previously failed platinum-based chemotherapy and/or immunotherapy remain limited, with OS benefits also relatively constrained. In the KEYNOTE-045 study, pembrolizumab significantly prolonged OS compared to chemotherapy, with median OS of 10.3 months versus 7.4 months (HR 0.73) (22). As a representative study of ADC-based late-line therapy, the EV-301 trial demonstrated a clear OS advantage for EV over chemotherapy, with a median OS of 12.88 months versus 8.97 months in the chemotherapy group (23). For TROP-2-targeted ADCs, the TROPHY-U-01 cohort study (in patients progressing after prior platinum-based chemotherapy and immunotherapy) reported median survival-specific PFS and OS of 5.4 months and 10.9 months, respectively (24). These findings suggest that in the context of relatively limited late-line treatment options and suboptimal OS improvement, further enhancing response depth and prolonging survival through ADC and combination immunotherapy strategies in populations with clear targeting advantages (such as HER2-expressing patients) holds significant clinical importance.
As global attention to real-world studies (RWS) continues to intensify, these studies systematically evaluate drug efficacy and safety in real-world populations based on routine clinical practice settings, providing a crucial complement to traditional randomized controlled trials (RCTs). This study, grounded in real-world evidence (RWE), reaffirms the clinical benefit of ADCs combined with PD-1 inhibitors in mUC. It further validates the efficacy and favorable tolerability of the combination regimen of RC48 with PD-1 inhibitors.
Results indicate that this combination regimen achieves high DCR (96.6%) even in patients with prior multi-line treatment history, with a PR of 34.5% and mPFS of 14.22 months, suggesting significant clinical benefit. Representative case studies further support its objective efficacy. Regarding safety, the most common AE was manageable peripheral neuropathy. The incidence of ≥ grade 3 AEs was low, and no treatment-related deaths were observed, indicating overall good tolerability.
Nevertheless, this study has certain limitations. First, the retrospective, single-center design inevitably introduces selection bias and information bias, and unmeasured confounders may affect interpretation of results. The small sample size also limits statistical power and the reliability of subgroup analyses. Second, the absence of a control group restricts direct comparisons between treatment strategies and causal inferences. Additionally, HER2 and PD-L1 status were based on routine clinical testing rather than centralized review, potentially introducing interpretation variability. Furthermore, given the study’s inclusion of primarily Chinese patients from a single center, caution is warranted regarding externalizability. Differences in patient characteristics, treatment accessibility, and testing practices across regions may affect the applicability of conclusions to broader populations, necessitating future validation through multicenter and international cohorts.
In summary, this study provides supportive real-world evidence for the combination of RC48 with PD-1 inhibitors in treating mUC. However, given its retrospective design, limited sample size, and exploratory nature, the findings should be interpreted as hypothesis-generating results, complementing existing RCTs and informing future prospective studies.
Conclusion
This real-world evidence study systematically evaluated the efficacy and safety of RC48 in combination with PD-1 inhibitors in patients with mUC. The results demonstrated that this combination regimen achieved a high DCR of 96.6%, even in patients with a history of multiple prior treatment lines, with a ORR of 34.5% and a mPFS of 14.22 months, indicating substantial clinical benefit. Representative cases further illustrated the objective efficacy, demonstrating significant tumor shrinkage. With respect to safety, the most common adverse event was manageable peripheral neuropathy, with a low incidence of grade ≥3 adverse events and no treatment-related deaths, indicating overall good tolerability of the combination regimen.
Overall, this study reaffirms the clinical value of RC48 in combination with PD-1 inhibitors for the treatment of mUC, demonstrating significant efficacy and manageable safety. These findings provide an important reference for subsequent prospective studies and clinical practice.
Supplementary
The article’s supplementary files as
Acknowledgments
We extend our gratitude to all patients, their families, and all collaborative group members involved in this trial.
Ethical Statement: This study was conducted in accordance with the Declaration of Helsinki and its subsequent revisions. It has been reviewed and approved by the Medical Ethics Committee of the Chinese PLA General Hospital (Approval No. S2023-121-01). Given the retrospective nature of this study, the informed consent procedure was waived.
Footnotes
Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://tau.amegroups.com/article/view/10.21037/tau-2025-1-942/rc
Funding: None.
Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tau.amegroups.com/article/view/10.21037/tau-2025-1-942/coif). The authors have no conflicts of interest to declare.
Data Sharing Statement
Available at https://tau.amegroups.com/article/view/10.21037/tau-2025-1-942/dss
References
- 1.Wang A, Chen M, Li D, et al. Disitamab Vedotin Alone or in Combination With Immune Checkpoint Inhibitors in Bladder-Sparing Treatment of Muscle-Invasive Bladder Cancer: A Real-World Study. Clin Genitourin Cancer 2024;22:102085 . 10.1016/j.clgc.2024.102085 [DOI] [PubMed] [Google Scholar]
- 2.Bray F, Laversanne M, Sung H, et al. Global cancer statistics 2022: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin 2024;74:229-63. 10.3322/caac.21834 [DOI] [PubMed] [Google Scholar]
- 3.Ciciriello F, Pezzicoli G, Biasi A, et al. HER2-Positive Urothelial Carcinoma: Current Evidence on Targeted Agents and Immunotherapy-Based Combinations. Target Oncol 2025;20:755-65. 10.1007/s11523-025-01165-1 [DOI] [PubMed] [Google Scholar]
- 4.Bellmunt J, von der Maase H, Mead GM, et al. Randomized phase III study comparing paclitaxel/cisplatin/gemcitabine and gemcitabine/cisplatin in patients with locally advanced or metastatic urothelial cancer without prior systemic therapy: EORTC Intergroup Study 30987. J Clin Oncol 2012;30:1107-13. 10.1200/JCO.2011.38.6979 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.International Collaboration of Trialists. Medical Research Council Advanced Bladder Cancer Working Party (now the National Cancer Research Institute Bladder Cancer Clinical Studies Group); European Organisation for Research and Treatment of Cancer Genito-Urinary Tract Cancer Group; et al. International phase III trial assessing neoadjuvant cisplatin, methotrexate, and vinblastine chemotherapy for muscle-invasive bladder cancer: long-term results of the BA06 30894 trial. J Clin Oncol 2011;29:2171-7. 10.1200/JCO.2010.32.3139 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Nally E, Young M, Wells C, et al. Is HER2 the New NECTIN4 in Advanced Urothelial Cancer? Eur Urol Focus 2024;10:219-21. 10.1016/j.euf.2024.05.018 [DOI] [PubMed] [Google Scholar]
- 7.Raggi D, Crupi E, Pederzoli F, et al. HER2 and urothelial carcinoma: current understanding and future directions. Nat Rev Urol 2026;23:110-32. 10.1038/s41585-025-01075-x [DOI] [PubMed] [Google Scholar]
- 8.Ye J, Chen Z, Liao X, et al. HER2 expression in upper tract urothelial carcinoma and the relationship with clinicopathological characteristics-an analysis of 155 patients in Southwest China. World J Urol 2024;42:521 . 10.1007/s00345-024-05222-8 [DOI] [PubMed] [Google Scholar]
- 9.Gong JF, et al. Safety, pharmacokinetics and efficacy of RC48-ADC in a phase I study in patients with HER2-overexpression advanced solid cancer. J Clin Oncol 2018;36(15). doi: 10.1200/JCO.2020.38.4_suppl.334 [DOI] [Google Scholar]
- 10.Sheng X, Wang L, He Z, et al. Efficacy and Safety of Disitamab Vedotin in Patients With Human Epidermal Growth Factor Receptor 2-Positive Locally Advanced or Metastatic Urothelial Carcinoma: A Combined Analysis of Two Phase II Clinical Trials. J Clin Oncol 2024;42:1391-402. 10.1200/JCO.22.02912 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 11.Wang JY, et al. An open-label, dose-escalation phase I study to evaluate RC48-ADC, a novel antibody-drug conjugate, in patients with HER2-positive metastatic breast cancer. J Clin Oncol 2018;36(15). doi: 10.1200/JCO.2018.36.15_suppl.1030 [DOI] [Google Scholar]
- 12.Xu BH, et al. An open-label, multicenter, phase Ib study to evaluate RC48-ADC in patients with HER2-positive metastatic breast cancer. J Clin Oncol 2018;36(15). doi: 10.1200/JCO.2018.36.15_suppl.1028 [DOI] [Google Scholar]
- 13.Zhou L, Yang KW, Zhang S, et al. Disitamab vedotin plus toripalimab in patients with locally advanced or metastatic urothelial carcinoma (RC48-C014): a phase Ib/II dose-escalation and dose-expansion study. Ann Oncol 2025;36:331-9. 10.1016/j.annonc.2024.12.002 [DOI] [PubMed] [Google Scholar]
- 14.Wang D, Cao M, Zhang Y, et al. RC48-ADC monotherapy or in combination with immunotherapy for locally advanced or metastatic urothelial carcinoma with HER2 low and null expression: a multicenter, real-world, retrospective study. BMC Cancer 2025;25:812. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Tang M, Garg A, Bonate PL, et al. Clinical Pharmacology of the Antibody-Drug Conjugate Enfortumab Vedotin in Advanced Urothelial Carcinoma and Other Malignant Solid Tumors. Clin Pharmacokinet 2024;63:423-38. 10.1007/s40262-024-01369-0 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Collins DM, Bossenmaier B, Kollmorgen G, et al. Acquired Resistance to Antibody-Drug Conjugates. Cancers (Basel) 2019;11:394 . 10.3390/cancers11030394 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Li S, Zhao X, Fu K, et al. Resistance to antibody-drug conjugates: A review. Acta Pharm Sin B 2025;15:737-56. 10.1016/j.apsb.2024.12.036 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Tiwari A, Oravecz T, Dillon LA, et al. Towards a consensus definition of immune exclusion in cancer. Front Immunol 2023;14:1084887 . 10.3389/fimmu.2023.1084887 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Zheng S, Wang W, Shen L, et al. Tumor battlefield within inflamed, excluded or desert immune phenotypes: the mechanisms and strategies. Exp Hematol Oncol 2024;13:80 . 10.1186/s40164-024-00543-1 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Heiser RA, Cao AT, Zeng W, et al. Brentuximab Vedotin-Driven Microtubule Disruption Results in Endoplasmic Reticulum Stress Leading to Immunogenic Cell Death and Antitumor Immunity. Mol Cancer Ther 2024;23:68-83. 10.1158/1535-7163.MCT-23-0118 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Powles TB, Van der Heijden MS, Loriot Y, et al. Enfortumab vedotin plus pembrolizumab in untreated locally advanced or metastatic urothelial carcinoma: 2.5-year median follow-up of the phase III EV-302/KEYNOTE-A39 trial. Ann Oncol 2025;36:1212-9. 10.1016/j.annonc.2025.05.536 [DOI] [PubMed] [Google Scholar]
- 22.Bellmunt J, de Wit R, Vaughn DJ, et al. Pembrolizumab as Second-Line Therapy for Advanced Urothelial Carcinoma. N Engl J Med 2017;376:1015-26. 10.1056/NEJMoa1613683 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Rosenberg JE, Powles T, Sonpavde GP, et al. EV-301 long-term outcomes: 24-month findings from the phase III trial of enfortumab vedotin versus chemotherapy in patients with previously treated advanced urothelial carcinoma. Ann Oncol 2023;34:1047-54. 10.1016/j.annonc.2023.08.016 [DOI] [PubMed] [Google Scholar]
- 24.Loriot Y, Petrylak DP, Rezazadeh Kalebasty A, et al. TROPHY-U-01, a phase II open-label study of sacituzumab govitecan in patients with metastatic urothelial carcinoma progressing after platinum-based chemotherapy and checkpoint inhibitors: updated safety and efficacy outcomes. Ann Oncol 2024;35:392-401. 10.1016/j.annonc.2024.01.002 [DOI] [PubMed] [Google Scholar]