ASCO 2022: Preliminary Results of a Phase Ib/II Combination Study of RC48-ADC, a Novel Humanized Anti-HER2 Antibody-Drug Conjugate With Toripalimab, a Humanized IgG4 mAb Against PD-1 in Patients With Locally Advanced or Metastatic Urothelial Carcinoma

(UroToday.com) At the 2022 American Society of Clinical Oncology Annual Meeting held in Chicago and virtually, the poster discussion session focused on Kidney and Bladder cancers on Saturday evening included a presentation from Dr. Xinan Sheng on the role of combined treatment of advanced urothelial carcinoma (UC) using a combination of a HER-2 targeted antibody-drug conjugate and immunotherapy.

For patients with metastatic urothelial carcinoma (UC), platinum-based chemotherapy remains the first-line treatment of choice for patients who are eligible. Despite being the guideline recommended approach, most patients will have disease progression following platinum-based chemotherapy. Immunotherapy using single agent immune checkpoint inhibitors is a standard, guideline-recommended second line treatment. However, the anti-HER-2 antibody-drug conjugate RC48-ADC has shown promising data in HER2-positive and even negative patients in this setting. Therefore, the authors sought to assess if RC48-ADC combined with anti-PD-1 antibody may have a synergistic antitumor effect.

To do so, they performed an open-label, multicenter, phase 1b/II trial to evaluate the safety and activity of RC48 combined with the anti-PD-1 antibody toripalimab in metastatic UC (NCT04264936). Enrolled patients received RC48-ADC at 1.5 or 2 mg/kg, in combination with 3mg/kg toripalimab every two weeks in a dose-escalation and expansion cohort until confirmed disease progression, unacceptable toxicity, or voluntary withdrawal.

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The key primary endpoint was safety with additional secondary endpoints including efficacy and correlative studies using tumor tissue biomarkers.

With enrollment opening August 20, 2022 and a data cutoff of January 17, 2022, 41 patients with locally advanced or metastatic UC had been enrolled. The median age of this cohort was 66 (42-76) years and 19 were men. The majority of patients (61%) had not received prior systemic therapy and most had visceral metastases (54%) including liver metastases in 24%. Most patients (54%) had upper tract UC while the remainder had bladder cancer.

HER2 expression was positive (IHC 2+ or 3+) in 59% patients, and PD-L1 was positive (CPS ≥ 10) in 32%.

In terms of the primary safety endpoint, no dose-limiting toxicity was observed. The recommended dose was RC48-ADC 2mg/kg + toripalimab 3mg/kg every 2 weeks.

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With a median follow-up of 8.0 months, 36 patients had at least one tumor assessment and the best objective response rate (ORR) was 83.3%, with a confirmed ORR of 76.7% (95%CI: 57.7, 90.1), including 10% CR.

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The cORR was 82.4% among patients who had not previously received systemic therapy for metastatic UC. Further, confirmed objective response rates differed according to HER2 and PD-L1 status: cORR was 100% for patients with HER2 IHC (2+ or 3+) & PD-L1 (+); 92.3% for HER2 (2+ or 3+) & PD-L1 (-); 50% for HER2 (0 or 1+) & PD-L1 (+); and 50% HER2 (0 or 1+) & PD-L1 (-). DCR was 96.7% (95%CI: 82.8, 99.9).

The most common treatment-related AEs were ALT/AST increase (65.9%), peripheral sensory neuropathy (58.5%), appetite decrease (56.1%), asthenia (56.1%), hypertriglyceridemia (48.8%). Grade ≥3 TRAEs included γ-glutamyl transferase increase (12.2%), ALT/AST increase (7.3%), asthenia (7.3%), hypertriglyceridemia (4.9%), and neutropenia (4.9%). 9 pts had irAEs (22.0%, 7.3% ≥ G3), including immune-related pneumonitis, hepatitis, and myositis.

The authors therefore conclude that the anti-HER-2 ADC RC48-ADC, in combination with the anti-PD-1 antibody toripalimab, demonstrated promising efficacy in patients with metastatic UC and a manageable safety profile. These data form the basis for an ongoing randomized comparison of first-line RC48-ADC and toripalimab compared to standard of care platinum-based chemotherapy in patients with previously untreated locally advanced or metastatic UC.



Presented by: Xinan Sheng MD, ABFT, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Genitourinary Oncology, Beijing Cancer Hospital, Beijing, China

Written by: Christopher J.D. Wallis, University of Toronto, Twitter: @WallisCJD during the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting, Chicago, IL, Fri, June 3 – Mon, June 7, 2022.

 

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