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

PURPOSE To evaluate the efficacy and safety of disitamab vedotin (DV, RC48-ADC), a novel humanized anti–human epidermal growth factor receptor 2 (HER2) antibody conjugated with monomethyl auristatin E, in patients with HER2-positive locally advanced or metastatic urothelial carcinoma (UC) refractory to standard or regular therapies. PATIENTS AND METHODS The data analyzed and reported are from two phase II, open-label, multicenter, single-arm studies (RC48-C005 and RC48-C009) in patients with HER2-positive (immunohistochemistry 3+ or 2+) locally advanced or metastatic UC who have progressed on at least one previous line of systemic chemotherapy. Patients received DV treatment (2 mg/kg IV infusion, once every 2 weeks). The primary end point was objective response rate (ORR) assessed by a blinded independent review committee (BIRC). Progression-free survival (PFS), overall survival (OS), and safety were also assessed. RESULTS One hundred and seven patients were enrolled in total. The overall confirmed ORR by BIRC was 50.5% (95% CI, 40.6 to 60.3). Consistent results were observed in prespecified subgroups including patients with liver metastasis and patients previously treated with anti–PD-1/L1 therapies. By the cutoff date of May 10, 2022, the median duration of response was 7.3 months (95% CI, 5.7 to 10.8). The median PFS and OS were 5.9 months (95% CI, 4.3 to 7.2) and 14.2 months (95% CI, 9.7 to 18.8), respectively. The most common treatment-related adverse events (TRAEs) were peripheral sensory neuropathy (68.2%), leukopenia (50.5%), AST increased (42.1%), and neutropenia (42.1%). Fifty-eight (54.2%) patients experienced grade ≥3 TRAEs, including peripheral sensory neuropathy (18.7%) and neutropenia (12.1%). CONCLUSION DV demonstrated a promising efficacy with a manageable safety profile in patients with HER2-positive locally advanced or metastatic UC who had progressed on at least one line of systemic chemotherapy.


INTRODUCTION
Locally advanced or metastatic urothelial carcinoma (UC) has a poor prognosis, with only about 5% of patients at stage IV (metastatic) surviving longer than 5 years. 1,2Platinumcontaining chemotherapy remains the first-line standard of care for advanced UC with the objective response rates (ORRs) of 44.6%-72% historically and the median overall survival (mOS) of 14.0-15.23][4] Recently, multiple immune checkpoint inhibitors, fibroblast growth factor receptor inhibitor (erdafitinib) and several antibody-drug conjugates (ADCs) including enfortumab vedotin (EV), sacituzumab govitecan (SG), and disitamab vedotin (DV, RC48), were approved in platinum-refractory settings in different regions of the world, 3,[5][6][7][8] and avelumab was approved as a maintenance treatment after at least disease control after first-line platinum-containing chemotherapy. 3,9 bladder cancer, human epidermal growth factor receptor 2 (HER2) overexpression generally correlated with tumor progression and poor prognosis, [10][11][12] but monoclonal antibodies and tyrosine kinase inhibitors targeting HER2 all failed to show clinical benefits in metastatic UC (mUC), [13][14][15] except that afatinib showed some promising results in patients with mUC-harbored HER2 or HER3 genomic alteration, 16,17 until the emergence of DV, a novel humanized anti-HER2 antibody conjugated with monomethyl auristatin E (MMAE) via a cleavable linker.The RC48-C005 trial (ClinicalTrials.govidentifier: NCT03507166) was initiated as a pivotal study, a phase II study to assess the efficacy and safety of DV in advanced UC that is HER2-positive (immunohistochemistry [IHC] 31 or 21).We observed an ORR of 51.2% and a progression-free survival (PFS) of 6.9 months in 43 patients.As recommended by the regulatory authority (National Medical Products Administration [NMPA]) in China, enrollment in the RC48-C005 trial was terminated and another similar study RC48-C009 trial (ClinicalTrials.govidentifier: NCT03809013) was conducted to go further to confirm the preliminary outcomes of the RC48-C005.Both studies showed promising efficacy and manageable safety in patients with mUC who had progressed on the previous systematic chemotherapy. 6,18In January 2022, DV was approved in China for platinum-refractory patients with metastatic UC on the basis of the RC48-C009 study.
We conducted two sequential studies to investigate the safety and efficacy of a new HER2-ADC in patients with HER2-positive chemotherapy-refractory urothelial cancer, and a combined analysis of the two studies with adaptive trial design endorsed by the regulatory authority in China (NMPA) was required to improve the estimation precision of both efficacy and safety.Here, we present the results of this combined analysis.recommended) once every 2 weeks until disease progression, intolerable toxicity, death, or withdrawal of consent.DV dose is based on calculations using bovine serum albumin (BSA)-based extinction coefficient (EC) implemented in China.Outside of China, DV dose calculation is based on DV-based EC, which is equivalent to 1.07 (BSA-based EC) 4 1.41 (DV-based EC) 3 BSA-based EC dose.Dose was modified and interrupted (up to 28 days) in case of treatment-related adverse events (TRAEs) until these events resolved to grade 0/1 or to baseline.Toxicity was managed with supportive care.Survival follow-up was performed for all patients every 12 weeks after the last treatment dose.
The clinical response was evaluated by a blinded independent review committee (BIRC) according to RECIST version 1.1 at baseline and every 6 weeks, irrespective of dose delays or interruptions, until documented disease progression or death.
All adverse events were monitored and graded according to the Common Terminology Criteria for Adverse Events version 4.03.Adverse events are described in preferred terms, as defined in the Medical Dictionary for Regulatory Activities (version 20.1).

HER2 Testing
These two studies targeted patients with HER2 expression by the IHC staining method.HER2-positive was defined as HER2 IHC 31 and 21.IHC scores were reviewed by an independent pathologist at the central laboratory.The detailed IHC methods and representative images of the HER2 IHC grading were previously described. 6Gene amplification of HER2 was also evaluated by fluorescence in situ hybridization (FISH).The staining scores and FISH status were assessed on the basis of the HER2 test guidelines for breast cancer. 19

End Points
The primary end point of the two studies was confirmed ORR assessed by BIRC.A confirmed response was defined as complete or partial response demonstrated via computed tomography or magnetic resonance imaging according to RECIST 1.1.The secondary end points included PFS, disease control rate (DCR), duration of response (DoR), OS, and safety.

Statistical Analysis
The statistical analysis methods of the two studies (RC48-C005 and RC48-C009) were consistent in design, and we maintained close communications and received endorsement from NMPA in China.The study designs including the statistical methods of both RC48-C005 and RC48-C009 are summarized in Appendix Tables A1 and A2 (online only), as well as their differences in the designs (refer to Appendix 1).
For each of the studies, the Clopper-Pearson exact binomial test 20 was conducted to compare the primary end point (ORR) with the prespecified historical control.The primary end point of ORR was met for each individual study.The same exact binomial tests were also used in pooled analysis for ORR, with the historical control rate and rationale as specified in the RC48-C005 trial.Taken the advantage of the pooled data, the estimates of efficacy and safety profiles are more robust and precise than individual ones.
In the RC48-C005 trial, a sample size of 60 allowed a 97% power and a one-sided a level of .025 to reject the null hypothesis with an expected 30% ORR of the investigational drug against an ORR of 10% in control and a dropout rate of 10%.Both ORRs (expected and control) were determined after consultation with NMPA on the basis of the reported range globally in 2016-2017 21 and expert experience.A total of 43 patients were enrolled and followed up in RC48-C005.The study was stopped early because of high efficacy observed in the prespecified interim analysis.A promising ORR of 66.7% and a DCR of 93.3% were observed from data of the first 30 patients.The early stopping of RC48-C005 was also agreed by NMPA.
In the RC48-C009 trial, the planned sample size of 60 patients allowed a 95% power and a one-sided a level of .025 to detect an ORR of 52% against a control ORR of 30% with a dropout rate of 10%.The ORR of 52% is estimated on the basis of partial follow-up data of RC48-005.The control ORR of 30% was determined after communication with NMPA and considered the highest ORR among existing treatment options 22,23 and the early readouts of the RC48-C005 study.
Two sensitivity analyses of median PFS (mPFS) were performed.The first sensitivity analysis censored patients at the date of last tumor assessment with documented nonprogression before the start of alternative treatments.The second one censored patients at the date of last tumor assessment with documented nonprogression before more than one missed visit.In addition, the median follow-up was calculated as the interval between the first DV treatment and the last known survival visit among patients censored for OS.
All statistical analyses were conducted using SAS 9.4 (SAS Institute Inc, Cary, NC).The full statistical analysis plan for each of the two studies is presented in Appendix 1.

RESULTS
In the combined analysis, 304 patients were screened and 107 were enrolled from 17 sites (Fig 1).The RC48-C005 trial was conducted on December 28, 2017, and the RC48-C009 trial was conducted on December 19, 2018.The last few patients of RC48-C005 and RC48-C009 were enrolled on November 28, 2018, and September 4, 2020, respectively.The data cutoff date for RC48-C005 is May 6, 2020, whereas the data cutoff date for RC48-C009 is May 10, 2022, which was also the cutoff date of survival follow-up in this combined analysis.
The 107 patients enrolled in the two trials included 80 males (74.8%), with a median age of 63.0 years (range, 40-79).About half of the patients had a primary tumor from the bladder (51.4%), and the others had upper tract UC (UTUC; renal pelvis, 26.2%; ureter, 28.2%).All the patients had metastatic disease.Most of the patients (97 patients, 90.7%) had visceral metastasis, including 48 patients (44.9%) of liver metastasis.Before starting the DV treatment, most patients (69 patients, 64.5%) had received more than one previous systematic treatment and 27 patients (25.2%) had received PD-1/PD-L1 inhibitor treatment.On the basis of the central laboratory test results, the number of patients confirmed with HER2 IHC 21 and 31 was 67 (62.6%) and 40 (37.4%),respectively.Five were tested as FISH1 and 53 were tested as FISH-in the patients with IHC HER2 21, whereas the FISH status of the other nine patients with IHC HER2 21 was unknown.The baseline characteristics of the two pooled studies' populations are listed in Table 1.
As assessed by the BIRC (Table 2), 54 patients (50.5%; 95% CI, 40.6 to 60.3) had confirmed objective responses according to RECIST 1.1, including two (1.9%) complete responders and 52 (48.6%) partial responders (PR).In addition, 34 patients (31.8%) experienced stable disease (SD) as the best response.The decrease in target lesions from baseline was observed in 88 (82.2%) of these patients (Fig 2A).The DCR was 82.2% (95% CI, 73.7 to 89.0; Table 2).The median DoR was 7.3 months (95% CI, 5.7 to 10.8; Table 2 Subgroup analyses (Fig 2C) indicated that the ORR was 50.0% in the 38 patients with only one previous line of chemotherapy and 50.7% in the 69 patients with two or more lines of treatment.Among 48 patients with liver metastasis, the confirmed ORR was 52.1%.Among the 27 patients who have received previous PD-1/PD-L1 inhibitors, the confirmed ORR was 55.6%.The ORR in patients with UTUC or bladder UC was both 50.0%.The ORR was numerically higher for patients with higher HER2 expression (defined as either HER2 IHC 21 and FISH-positive or IHC 31; ORR, 62.2%) than patients with lower HER2 expression (defined as HER2 IHC 21 and FISH-negative; ORR, 39.6%).Of the nine patients with IHC 21 and unknown FISH results, five patients had partial response (ORR, 55.6%).However, no statistical significance was seen.

DISCUSSION
To our knowledge, the RC48-C005 study is the first phase II trial of evaluating HER2-targeting ADC (DV) in HER2 IHC 31 or 21 patients with mUC who have progressed on at least one previous line of chemotherapy, which demonstrated promising efficacy (ORR, 51.2%; mPFS, 6.9 months; mOS, 13.9 months) with a manageable safety profile.The combined analysis of RC48-C005 and RC48-C009 demonstrated the consistently promising efficacy of DV in HER2-positive, chemotherapy-refractory patients with mUC, with an overall ORR of 50.5%, a PFS of 5.9 months, and an OS of 14.2 months.The treatment effects were consistent in all key subgroups.
Asian patients with mUC carried a characteristic of a higher incidence rate of UTUC than the Western population, generally about 20%-36% in most Asian cohorts with mUC. 24,25ost of the mUC studies in the standard therapy failure settings observed a relatively better efficacy in lower tract UC (LTUC) than UTUC. 5,9,26In the current study, the ORRs of patients with both UTUC and LTUC were 50.0%(Fig 2C ) and the mPFS (5.3 months v 6.2 months) and mOS (14.9 months v 15.2 months) of UTUC were comparable with those of LTUC, which suggested that DV has comparable performance in patients with metastatic UTUC to LTUC.
As indicated in the current study, HER2-targeting DV achieved favorable outcomes in patients with HER2-positive advanced UC, with an ORR of 62.2% in the IHC21 and FISH1 or IHC31 patients.The phase III trial with a larger sample size with adequately represented HER2 expression subgroups could help to address this issue.In addition, we also observed a moderate ORR in IHC 21 and FISH-negative patients (39.6%).This provides a potential of DV treatment in patients with low or even negative HER2 expression.Accordingly, the RC48-C011 study (ClinicalTrials.govidentifier: NCT04073602) of DV in patients with HER2-negative (IHC 0 or 11) metastatic UC was developed and completed the enrollment.The preliminary result of the RC48-C011 study  showed certain antitumor activity of DV in HER2-negative metastatic UC with a confirmed ORR of 26.3%, a mPFS of 5.6 months, and a mOS of 16.4 months. 27 and SG targets for nectin-4 and trop-2 were approved for use in the unselected patient population.In comparison, DV previously required HER2-positive patients.emerging data from the RC48-C011 study, 27 HER2 screening might not be needed for DV in the future.Further clinical trials are warranted to test this hypothesis.In fact, except for the RC48-C011 trial, the RC48G001 trial (ClinicalTrials.govidentifier: NCT04879329) was also developed to test DV alone or in combination with pembrolizumab in HER2-positive or HER2-low patients with mUC, whereas the RC48-C014 trial (ClinicalTrials.govidentifier: NCT04264936) is ongoing to test the combination of DV with toripalimab, an anti-PD-1 inhibitor, in mUC without restriction of HER2 expression status.
Early progression on previous platinum-based chemotherapy and a shorter time between the initial time of platinum-based chemotherapy and subsequent therapy were considered to be associated with poor outcomes in mUC. 28In the current combined analyses, no differences in the ORRs (53.3% v 42.9% v 52.2%) and the mPFS (5.4 months v 6.2 months v 6.2 months) were observed when comparing patients with different median times from initiation of the previous chemotherapy to first DV treatment (<3 months v 3-6 months v >6 months).Hence, the influence of clinical response to previous chemotherapy on the subsequent DV treatment needs to be further explored in a future study on DV treatment.
6][7] As to those patients with mUC who had progressed on both chemotherapy and anti-PD-1/L1 therapy, the ORRs after the EV treatment ranged from 40.6% to 44.0%, with the mPFS from 5.6 months to 5.8 months and the mOS from 11.7 months to 12.9 months, as indicated in EV201 and EV301 studies. 5,26ohort 1 results from the TROPHY-U-01 study showed that the ORR of SG treatment in the same setting was 27%, with the mPFS and OS being 5.4 months and 10.9 months, respectively. 7ccording to the current study, DV demonstrated a comparable ORR (55.6%), mPFS (6.9 months), and mOS (19.1 months; Appendix Fig A3).Although the comparison among separate clinical trials could be problematic and challenging because of possible selection bias, confounding, and other factors, the efficacy data from the above trials suggested the promising role of DV in patients with mUC who progressed on both chemotherapy and anti-PD-1/L1 therapy.
Given that these ADCs achieved success in the chemotherapyrefractory settings in patients with mUC, the next step is to move forward the use of ADCs to the frontline treatment.Without exception, these ADCs moved forward to choose combination with the PD-1/L1 inhibitors.Both cohort A of the EV-103 trial 29 and cohort K of the EV-103 trial 30 used EV in combination with pembrolizumab as the first-line therapy to treat the cisplatin-ineligible patients with mUC and demonstrated the ORRs of 64.5%-73.3%.The median DoR of cohort A in the EV-103 trial was 25.6 months, whereas the median DoR of cohort K in the EV-103 trial was not reached with a median follow-up of 14.8 months.DV was also set to combine with toripalimab to treat the patients with mUC in the RC48-C014 trial (ClinicalTrials.govidentifier: NCT04264936), 31 and 73.9% of confirmed ORR in first-line therapy was achieved as their preliminary results indicated.These data support EV or DV plus PD-1 inhibitor as the firstline treatment in cisplatin-ineligible patients with mUC.On the basis of these data, the FDA granted accelerated approval to EV with pembrolizumab for cisplatin-ineligible patients with locally advanced or metastatic UC on April 3, 2023, 32 whereas a phase III EV-302 trial is ongoing to compare EV plus pembrolizumab versus cisplatin-containing chemotherapy in the first-line treatment of patients with cisplatin-eligible mUC (ClinicalTrials.govidentifier: NCT04223856).However, the TROPHY-U-01 trial of cohort 3 attempted to combine SG with pembrolizumab as second-line therapy in checkpoint inhibitor-naive patients with mUC who progressed after platinum-based chemotherapy, and after a median follow-up of 12.5 months, the ORR was 41% and the mPFS was 5.3 months, whereas the median time to response was 1.4 months and the median OS was 12.7 months. 33The role of SG plus pembrolizumab in first-line therapy needs to be explored further.
DV-induced toxicity was clinically manageable in the current combined analysis.The most common TRAEs included leukopenia, liver function injury, and peripheral sensory neuropathy.These AEs were considered to be mostly related to the toxicity of DV payload, MMAE.No grade 4 or 5 TRAEs were observed.When compared with the previous reports from the RC48-C005 study, the incidence rate of peripheral sensory neuropathy in this combined study was relatively lower (all grade, 68.2% v 74.5%; grade 3, 18.7% v 25.6%).Given the larger sample size and longer follow-up than the RC48-C005 study, this combined analysis could eventually reflect the real status of peripheral sensory neuropathy including its incidence rate and grade after the treatment of DV.
One of the limitations of this study is that the enrollment was exclusively in China, while its applicability to Western populations remains unknown.To explore the efficacy and safety of DV treatment in Western populations, an international, multicenter, multicohort, phase II study was developed (RC48G001 study; ClinicalTrials.govidentifier: NCT04879329), including sites from North America, Europe, Latin America, Asia-Pacific, and Israel.Because of the limitation of the nonrandomized trial including the possible selection biases and heterogeneity of mixing two trial populations, there is a need to evaluate the DV in a broader population of patients with metastatic UC and in phase III randomized trials.Further detailed biomarker studies on the basis of the DV treatment or related data of quality of life would help for the precise selection of benefited patients and acknowledge the patients' quality-oflife performance from DV treatment.
In conclusion, this combined analysis demonstrated a consistent efficacy of DV against chemotherapy-refractory mUC with a manageable safety profile.

EQUAL CONTRIBUTION
A.Z., X.S., and Jun G. contributed equally to this work.

PRIOR PRESENTATION
The results of this study had been presented at the 2022 ASCO Annual Meeting, poster discussion (abstract No. 4520).

SUPPORT
Supported by RemeGen, Ltd.This work was supported in part by the Natural Science Foundation of China (82172604).© 2023 by American Society of Clinical Oncology

FIG 1 .
FIG 1. Overall flowchart.a For the C005 study, two patients had two reasons for screening failure.For the C009 study, 12 patients had two reasons for screening failure.HER2, human epidermal growth factor receptor 2.

FIG 2 .
FIG 2. (A) Waterfall plot of the best percent change from baseline in the sum of the diameters of target lesions.Eighty-eight (82.2%) patients had a decrease in tumor size from baseline as assessed by the BIRC.(B) Swimmer plot of patients' responses from the start of treatment to PD assessed by the BIRC, death, or (continued on following page) FIG A3. (Continued).

Table 2 ;
Appendix Fig A2B).Subgroup analyses indicated that the mPFS and mOS had no significant difference across all subgroups, including the location of primary tumor, visceral metastases, previous chemotherapy, previous treatment of PD-1/PD-L1 inhibitors, and HER2 status (Appendix FigsA3A and A3B).The median treatment duration for RC48-ADC was 21.3 weeks (range, 2.0-143.4).The median dose intensity was 96.0% (range, 40.0%-100.0%).In this study, the median time to treatment discontinuation for treatment-related reasons is 154 days.Nineteen patients discontinued treatment owing to grade 2 (n 5 4) and grade 3 (n 5 15) TRAEs, in whom the

TABLE 1 .
Baseline Demographic and Clinical CharacteristicsAbbreviations: ECOG PS, Eastern Cooperative Oncology Group Performance Status; FISH, fluorescence in situ hybridization; HER2, human epidermal growth factor receptor 2; HGB, hemoglobin; IHC, immunohistochemistry; UC, urothelial carcinoma.aP values for comparison of sex, primary lesion, HER2 status, current extent of disease, metastasis sites, number of previous systemic therapies, previous therapies, and Bellmunt score are based on the chi-square test; P value for age comparison is based on the t test.The Bellmunt risk score categorizes patients into four risk groups by assigning a point for each of three risk factors; an ECOG PS of >0, a HGB level of <10 g/dL, and the presence of liver metastases.
b FISH testing was performed for all the patients with IHC 21. c Forty patients (37.4%) were classified as IHC 31, and five patients (4.7%) as IHC21 FISH1.dTheFISH testing results for nine patients are unknown.eJournal of Clinical Oncology ascopubs.org/journal/jco|Volume42, Issue 12 | 1395proportion of patients with PR and SD was 68.4%(13 of

TABLE 2 .
Tumor Responses as Assessed by the BIRC FIG 2. (Continued).withdrawal.Fifty-four patients (50.5%) were responders whose target lesion decreased by not <30%, and one patient (0.9%) and 53 patients (49.5%) were assessed as confirmed CR and PR, respectively.The best response of 34 patients (31.8%) was SD, and 19 patients had PD.(C) Forest plot of the ORRs in key subgroups.The subgroups were based on the baseline disease characteristics.The confirmed ORR was evaluated in the key prespecified subgroups per the BIRC.
Disclosures provided by the authors are available with this article at DOI https://doi.org/10.1200/JCO.22.02912.