Clinical Development of FGFR3 Inhibitors for the Treatment of Urothelial Cancer

FGFR Inhibitors in Urothelial Cancer: From Scientific Rationale to Clinical Development

In the past decade, the treatment of metastatic urothelial cancer (mUC), including bladder cancer (BC), has transformed significantly with the introduction of diverse therapies, such as immune checkpoint inhibitors, targeted therapies, and antibody-drug conjugates. This change is partly due to advancements in genomic understanding, particularly next-generation sequencing, which has identified numerous mutations in UC. Among these therapies, erdafitinib, a pan-fibroblast growth factor receptor (FGFR) inhibitor for specific FGFR2 and FGFR3 alterations, is the only targeted therapy approved till now. In 2019, erdafitinib became pivotal for the treatment of mUC, particularly in patients with specific FGFR alterations. Recent studies have highlighted the benefits of combining erdafitinib with immunotherapy, thereby broadening the treatment options. Ongoing investigations exist on its use in non-muscle-invasive BC and in combination with drugs such as enfortumab vedotin in mUC. Other FGFR-targeted agents are under development; however, overcoming FGFR resistance and ensuring the safety of combination therapies remain major hurdles. FGFR3 mutations are particularly prevalent in BC, a heterogeneous form of UC, and account for a considerable proportion of new cancer diagnoses annually. Approximately half of these cancers have FGFR3 mutations, with gene rearrangements being a common feature. These FGFR3 genomic alterations often occur independently of mutations in other BC oncogenes, such as TP53 and RB1. This review emphasizes the importance of FGFR inhibition in UC and the optimization of its use in clinical practice. Moreover, it underscores the ongoing efforts to evaluate combination strategies and early treatment testing to enhance the effectiveness of targeted therapies for UC.

Predictive and Prognostic Biomarkers and Tumor Antigens for Targeted Therapy in Urothelial Carcinoma

Urothelial carcinoma (UC) is the fourth most prevalent cancer amongst males worldwide. While patients with non-muscle-invasive disease have a favorable prognosis, 25% of UC patients present with locally advanced disease which is associated with a 10-15% 5-year survival rate and poor overall prognosis. Muscle-invasive bladder cancer (MIBC) is associated with about 50% 5 year survival when treated by radical cystectomy or trimodality therapy; stage IV disease is associated with 10-15% 5 year survival. Current therapeutic modalities for MIBC include neoadjuvant chemotherapy, surgery and/or chemoradiation, although patients with relapsed or refractory disease have a poor prognosis. However, the rapid success of immuno-oncology in various hematologic and solid malignancies offers new targets with tremendous therapeutic potential in UC. Historically, there were no predictive biomarkers to guide the clinical management and treatment of UC, and biomarker development was an unmet need. However, recent and ongoing clinical trials have identified several promising tumor biomarkers that have the potential to serve as predictive or prognostic tools in UC. This review provides a comprehensive summary of emerging biomarkers and molecular tumor targets including programmed death ligand 1 (PD-L1), epidermal growth factor receptor (EGFR), human epidermal growth factor receptor 2 (HER2), fibroblast growth factor receptor (FGFR), DNA damage response and repair (DDR) mutations, poly (ADP-ribose) polymerase (PARP) expression and circulating tumor DNA (ctDNA), as well as their clinical utility in UC. We also evaluate recent advancements in precision oncology in UC, while illustrating limiting factors and challenges related to the clinical application of these biomarkers in clinical practice.

[Precision oncology options in urological cancers]

Advancements in the molecular genetic understanding of urological tumors have enabled the identification of numerous new therapeutic targets. Based on routinely applicable tumor sequencing, individual treatment decisions have been introduced in the context of precision oncology. This work provides an overview of the latest targeted tumor therapies in the treatment of prostate cancer, urothelial carcinoma, and renal cell carcinoma. Current studies on the administration of FGFR-inhibitors ("fibroblast growth factor receptor") in metastatic urothelial carcinoma show a high tumor response in patients with selected FGFR alterations. PARP-inhibitors ("Poly-[ADP-Ribose-]Polymerase") are routinely used in the treatment of metastatic prostate cancer. Patients with a BRCA mutation ("BReast CAncer gene") show high radiological response rates. Moreover, we discuss the latest results of the combination of PARP inhibitors with novel androgen receptor pathway inhibitors. In metastatic prostate cancer, there are numerous ongoing studies evaluating the promising drug targets PI3K/AKT/mTOR ("Phosphatidylinositol-3-Kinase")/AKT/mTOR ("mammalian target of rapamycine") and VEGF signaling pathways ("vascular endothelial growth factor"). A HIF-2a inhibitor ("hypoxia inducible factor") offers a promising new therapeutic option for metastatic renal cell carcinoma. Overall, molecular diagnostics to determine the right therapy for the right patient subgroup at the right time is important for uro-oncological precision medicine.

PD-L1 expression and FGFR-mutations among Danish patients diagnosed with metastatic urothelial carcinoma: A retrospective and descriptive study

Checkpoint inhibitors have changed the treatment landscape of advanced urothelial carcinoma (mUC), and recently, a fibroblast-growth-factor-receptor (FGFR) inhibitor has been introduced. This study aimed at estimating programmed death-ligand 1 (PD-L1) expression in primary tumors (PTs) and the PD-L1 expression concordance between PTs and paired metastases in 100 patients with UC managed in the real-world setting. Further, the aim was to investigate FGFR1-3 aberrations and the correlation between FGFR1-3 aberrations and PD-L1 expression. PD-L1 immunohistochemistry was performed on 100 formalin-fixed paraffin-embedded archival primary UC samples and 55 matched metastases using the 22C3 PD-L1 assay. PD-L1 expression was determined by the combined positive score, considered positive at ≥10. Targeted next-generation sequencing on the S5+/Prime System with the Oncomine Comprehensive Assay version 3 was used to detect FGFR1-3 aberrations in PTs. We found that 29 of 100 PTs had positive PD-L1 expression. The PD-L1 concordance rate was 71%. FGFR1-3 aberrations were observed in 18% of PTs, most frequently FGFR3 amplifications or mutations. We found no association between FGFR1-3 aberrations and PT PD-L1 expression (p = 0.379). Our data emphasize the need for further studies in predictive biomarkers.

Biological Significance and Targeting of the FGFR Axis in Cancer

The pleiotropic effects of fibroblast growth factors (FGFs), the widespread expression of all seven signalling FGF receptors (FGFRs) throughout the body, and the dramatic phenotypes shown by many FGF/R knockout mice, highlight the diversity, complexity and functional importance of FGFR signalling. The FGF/R axis is critical during normal tissue development, homeostasis and repair. Therefore, it is not surprising that substantial evidence also pinpoints the involvement of aberrant FGFR signalling in disease, including tumourigenesis. FGFR aberrations in cancer include mutations, gene fusions, and amplifications as well as corrupted autocrine/paracrine loops. Indeed, many clinical trials on cancer are focusing on targeting the FGF/FGFR axis, using selective FGFR inhibitors, nonselective FGFR tyrosine kinase inhibitors, ligand traps, and monoclonal antibodies and some have already been approved for the treatment of cancer patients. The heterogeneous tumour microenvironment and complexity of FGFR signalling may be some of the factors responsible for the resistance or poor response to therapy with FGFR axis-directed therapeutic agents. In the present review we will focus on the structure and function of FGF(R)s, their common irregularities in cancer and the therapeutic value of targeting their function in cancer.

Response to pazopanib-based combination regimen in a case of FGFR3 amplified gastric adenocarcinoma

Angiogenesis inhibitors (AGI) are not presently used for the treatment of gastric cancers. This report demonstrates that angiogenesis inhibitor can be safely and effectively used in combination with cytotoxic anti-cancer agents for treatment of Gastric cancers.

Fibroblast growth factor receptors across urothelial carcinoma landscape

PURPOSE OF REVIEW

Fibroblast growth factor receptor (FGFR) signalling, especially induced by FGFR3, is a crucial factor in the pathogenesis of urothelial carcinoma and was therefore extensively studied over the last decades. In this review, we summarize the most relevant findings of the past two years.

RECENT FINDINGS

Recent studies support the concept that FGFR3 mediates a pathway of urothelial carcinogenesis associated with low malignant potential. FGFR3 may represent a highly accurate biomarker for diagnosis and prediction of recurrence, progression or therapy response. The pan FGFR-inhibitor erdafitinib was recently approved for urothelial carcinoma, whereas several other FGFR-targeted drugs are currently undergoing clinical trials.

SUMMARY

Numerous recent studies focus on the role of FGFR3 in different urothelial carcinoma subtypes and its potential clinical application as noninvasive biomarker, as well as therapeutic target.

Targetable gene fusions and aberrations in genitourinary oncology

Gene fusions result from either structural chromosomal rearrangement or aberrations caused by splicing or transcriptional readthrough. The precise and distinctive presence of fusion genes in neoplastic tissues and their involvement in multiple pathways central to cancer development, growth and survival make them promising targets for personalized therapy. In genitourinary malignancies, rearrangements involving the E26 transformation-specific family of transcription factors have emerged as very frequent alterations in prostate cancer, especially the TMPRSS2-ERG fusion. In renal malignancies, Xp11 and t(6;11) translocations are hallmarks of a distinct pathological group of tumours described as microphthalmia-associated transcription factor family translocation-associated renal cell carcinomas. Novel druggable fusion events have been recognized in genitourinary malignancies, leading to the activation of several clinical trials. For instance, ALK-rearranged renal cell carcinomas have shown responses to alectinib and crizotinib. Erdafitinib has been tested for the treatment of FGFR-rearranged bladder cancer. Other anti-fibroblast growth factor receptor 3 (FGFR3) compounds are showing promising results in the treatment of bladder cancer, including infigratinib and pemigatinib, and all are currently in clinical trials.