Case report: The remarkable response of pembrolizumab combined with RC48 in the third-line treatment of metastatic urothelial carcinoma

BACKGROUND: Systemic chemotherapy has been the mainstay treatment for locally advanced or metastatic urothelial carcinoma (UC). In the past few years, novel immune checkpoint inhibitors (ICIs) and antibody-drug conjugates (ADCs) have improved the treatment of advanced UC. CASE PRESENTATION: Here, we report systemic therapy of a 68-year-old male diagnosed with HER2 positive (immunohistochemistry 3+), programmed cell death ligand 1(PD-L1) negative metastatic UC, and renal insufficiency. He had encountered numerous metastases and failed first-line platinum-based chemotherapy and second-line treatment with pembrolizumab and trastuzumab. During third-line treatment with RC48 (a HER2 targeting ADC) combined with pembrolizumab, he achieved a rapid partial response (PR) in the first evaluation and subsequent complete response (CR) on PET/CT and long-term progression-free survival (>12 months) at the last follow-up on 25 August 2022. There are no grade 3 or 4 adverse events or aggravations of renal insufficiency during the third-line therapy. DISCUSSION: RC48 combined with pembrolizumab demonstrated outstanding efficacy and safety in this HER2-positive metastatic UC patient. ADC combined with ICI is a promising anti-tumor strategy that deserves further exploration in advanced UC.