Erdafitinib Monotherapy or in Combination With Cetrelimab in Muscle-invasive Bladder Cancer Patients With Fibroblast Growth Factor Receptor (FGFR ) Gene Alterations

The aim of the study is to assess the antitumor activity measured as ypT0 rate, defined as no evidence of residual disease based on pathological review of the surgical specimen (pCR) and tumour downstaging (\<ypT2). Patients must have a MIBC (cT2-T4a N0/N1 M0) who harbour selected FGFR alterations stated in the protocol and are either ineligible for or refuse cisplatin-based neoadjuvant chemotherapy, as defined by consensus criteria (see 6.1 Inclusion criteria).

Once it is confirmed that the subjects fulfil the eligibility criteria and have signed the informed consent form, they will receive erdafitinib alone (cohort 1) or erdafitinib in combination with cetrelimab (cohort 2).

Patients will receive neoadjuvant treatment with erdafitinib alone (cohort 1) or erdafitinib plus cetrelimab (cohort 2) before proceeding to Radical Cystectomy (RC) (to be performed within 2 - 6 weeks after the last study drug treatment)

Cohort 1: patients will receive erdafitinib Cohort 2: patients will receive erdafitinib in combination with cetrelimab intravenously (IV)

Radiological assessment: A Computed Tomography /Magnetic Resonance Imaging and/or Positron Emission Tomography (per standard local imaging practices) will be scheduled as follow:

* Basal assessment: during screening period (no more than 28 days before Cycle1, Day 1(C1D1) * Response assessment: At the end of treatment period allowing time for imaging review in advance of Radical cystectomy (RC). * Follow-up assessment: an image evaluation must be done at first follow-up visit and thereafter, it will be schedule according to local standards and as clinically indicated.

A local pathological assessment will be done on specimens obtained during RC (for co-primary endpoints). Thereafter, during the follow-up period, pathological assessments will be scheduled according to local standards and as clinically indicated.

Patients with disease progression during the treatment phase will be discontinued from the study and will receive their treatment according to the investigator's judgment and monitored to evaluate Overal Survival .

• Rate of pathological downstaging (pDS) [Срок оценки: During treatment (27 months)]
• Event-free Survival rate. [Срок оценки: During follow-up period (36 months)]
• Overall Survival [Срок оценки: During follow-up period (36 months)]
• Overall Response Rate [Срок оценки: During treatment (27 months)]
• Adverse events. [Срок оценки: During treatment (27 months) and follow-up period (36 months)]
• Rate of delay of surgery [Срок оценки: During treatment (27 months) and follow-up period (36 months)]