Combination therapies involving checkpoint-inhibitors for treatment of urothelial carcinoma: a narrative review

The implementation of immune checkpoint-inhibitors (CPI) has significantly improved the prognosis of a subgroup of patients with urothelial bladder cancer (BC). Still, the majority of patients will progress or experience a recurrence on CPI monotherapy. The next generation of clinical trials is now testing combination therapy with CPI and other agents that target different oncogenic mechanisms in an effort to improve efficacy. The beneficial toxicity profile of CPI but also the approval of CPI combinations in other cancer sites justifies their investigation also in BC. Here we report on clinical trials in muscle-invasive, locally advanced and metastatic BC combining CPI with other therapies, with a focus on the latest results presented at ASCO GU 2020, ASCO 2020 and ESMO 2019 as well as Phase-III trials currently ongoing. Multiple phase I-III clinical trials are investigating the combination of a CPI with a second CPI, with chemotherapy, or with targeted therapies like fibroblast growth factor receptor (FGFR) inhibitors or Nectin-4 inhibitors in different disease states. The results of more than 10 phase-III trials in advanced BC are eagerly awaited. Preliminary data are contradictory, as some trials released promising interim results, while others reported failure to achieve the primary endpoints. Taken together, combining CPI with other therapies is a logical and potentially promising approach, but it is too early to draw conclusions on specific combinations. As combinatorial therapies markedly increase the level of complexity, bedside-to-bench studies are warranted to gain deeper insight of underlying biological mechanisms which can be used to optimize future trials.