Overview of the clinical use of erdafitinib as a treatment option for the metastatic urothelial carcinoma: where do we stand

Urothelial Bladder Cancer: Genomic Alterations in Fibroblast Growth Factor Receptor

BACKGROUND AND OBJECTIVE

Genomic alterations in fibroblast growth factor receptor (FGFR) genes have been linked to a reduced response to immune checkpoint inhibitors. Some of the immune microenvironment of urothelial bladder cancer (UBC) could be distorted because of the inhibition of interferon signaling pathways. We present a landscape of FGFR genomic alterations in distorted UBC to evaluate the immunogenomic mechanisms of resistance and response.

METHODS

There were 4035 UBCs that underwent hybrid, capture-based comprehensive genomic profiling. Tumor mutational burden was determined in up to 1.1 Mbp of sequenced DNA and microsatellite instability was determined in 114 loci. Programmed death ligand expression in tumor cells was assessed by immunohistochemistry (Dako 22C3).

RESULTS

The FGFR tyrosine kinases were altered in 894 (22%) UBCs. The highest frequency of alterations was in FGFR genomic alterations with FGFR3 at 17.4% followed by FGFR1 at 3.7% and FGFR2 at 1.1%. No FGFR4 genomic alterations were identified. The age and sex distribution were similar in all groups. Urothelial bladder cancers that featured FGFR3 genomic alterations were associated with lower driver genomic alterations/tumors. 14.7% of the FGFR3 genomic alterations were FGFR3 fusions. Other findings included a significantly higher frequency of ERBB2 amplification in FGFR1/2-altered UBCs compared with FGFR3-altered UBCs. Urothelial bladder cancers with FGFR3 genomic alterations also had the highest frequency of the activating mTOR pathway. FGFR3-altered UBCs also featured significantly higher frequencies of biomarkers associated with a lack of response to immune checkpoint inhibitors including a lower tumor mutational burden, lower programmed death-ligand 1 expression, and higher frequencies of genomic alterations in MDM2. Also linked to IO drug resistance, CDKN2A/B loss and MTAP loss were observed at a higher frequency in FGFR3-driven UBC.

CONCLUSIONS

An increased frequency of genomic alterations is observed in UBC FGFR. These have been linked to immune checkpoint inhibitor resistance. Clinical trials are needed to evaluate UBC FGFR-based biomarkers prognostic of an immune checkpoint inhibitor response. Only then can we successfully incorporate novel therapeutic strategies into the evolving landscape of UBC treatment.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Fibroblast Growth Factor Inhibitors for Treating Locally Advanced/Metastatic Bladder Urothelial Carcinomas via Dual Targeting of Tumor-Specific Oncogenic Signaling and the Tumor Immune Microenvironment

Locally advanced or metastatic urothelial bladder cancer (a/m UBC) is currently treated using platinum-based combination chemotherapy. Immune checkpoint inhibitors (ICIs) are the preferred second-line treatment options for cisplatin-eligible a/m UBC patients and as first-line options in cisplatin-ineligible settings. However, the response rates for ICI monotherapy are modest (~20%), which necessitates the exploration of alternative strategies. Dysregulated activation of fibroblast growth factor receptor (FGFR) signaling enhances tumor proliferation, survival, invasion, angiogenesis, and immune evasion. The recent U.S. Food and Drug Administration approval of erdafitinib and the emergence of other potent and selective FGFR inhibitors (FGFRis) have shifted the treatment paradigm for patients with a/m UBC harboring actionable FGFR2 or FGFR3 genomic alterations, who often have a minimal-to-modest response to ICIs. FGFRi-ICI combinations are therefore worth exploring, and their preliminary response rates and safety profiles are promising. In the present review, we summarize the impact of altered FGFR signaling on a/m UBC tumor evolution, the clinical development of FGFRis, the rationale for FGFRi-ICI combinations, current trials, and prospective research directions.

GZD824 overcomes FGFR1-V561F/M mutant resistance in vitro and in vivo

Abnormallyactivated FGFR1 has been validated as a therapeutic target for differentcancers. Although a variety of FGFR inhibitors have shown benefit in manyclinical patients with FGFR1 aberration, FGFR1 mutant resistance such as V561Mmutation, has been reported. To date however, no FGFR inhibitors have beenapproved to treat patients with FGFR mutant resistance. Herein, we report that GZD824, athird generation ABL inhibitor (Phase II, China), overcomes FGFR1‐V561F/M mutant resistance in vitro and in vivo. GZD824potently suppresses FGFR1/2/3 with an IC₅₀ value of 4.14 ± 0.96, 2.77 ± 0.082, and 8.10 ± 0.15 nmol/L. It effectively overcomes FGFR1‐V561F/M and other mutantresistance in Ba/F3 stable cells (IC₅₀:8.1–55.0 nM), and effectively inhibits the growth of Ba/F3‐FGFR1‐V561F/M mutantxenograft tumors in vivo (TGI=73.4%, 49.8% at20mg/kg, p.o, q2d). GZD824may be considered to be an effective drug to treat patients with FGFR1 abnormalactivation or mutant resistance in clinical trials.

2b or Not 2b: How Opposing FGF Receptor Splice Variants Are Blocking Progress in Precision Oncology

More than ten thousand peer-reviewed studies have assessed the role of fibroblast growth factors (FGFs) and their receptors (FGFRs) in cancer, but few patients have yet benefited from drugs targeting this molecular family. Strategizing how best to use FGFR-targeted drugs is complicated by multiple variables, including RNA splicing events that alter the affinity of ligands for FGFRs and hence change the outcomes of stromal-epithelial interactions. The effects of splicing are most relevant to FGFR2; expression of the FGFR2b splice isoform can restore apoptotic sensitivity to cancer cells, whereas switching to FGFR2c may drive tumor progression by triggering epithelial-mesenchymal transition. The differentiating and regulatory actions of wild-type FGFR2b contrast with the proliferative actions of FGFR1 and FGFR3, and may be converted to mitogenicity either by splice switching or by silencing of tumor suppressor genes such as CDH1 or PTEN. Exclusive use of small-molecule pan-FGFR inhibitors may thus cause nonselective blockade of FGFR2 isoforms with opposing actions, undermining the rationale of FGFR2 drug targeting. This splice-dependent ability of FGFR2 to switch between tumor-suppressing and -driving functions highlights an unmet oncologic need for isoform-specific drug targeting, e.g., by antibody inhibition of ligand-FGFR2c binding, as well as for more nuanced molecular pathology prediction of FGFR2 actions in different stromal-tumor contexts.

Focus on ROS1-Positive Non-Small Cell Lung Cancer (NSCLC): Crizotinib, Resistance Mechanisms and the Newer Generation of Targeted Therapies

Simple Summary

Genetic rearrangements of the ROS1 gene account for up to 2% of NSCLC patients who sometimes develop brain metastasis, resulting in poor prognosis. This review discusses the tyrosine kinase inhibitor crizotinib plus updates and preliminary results with the newer generation of tyrosine kinase inhibitors, which have been specifically conceived to overcome crizotinib resistance, including brigatinib, cabozantinib, ceritinib, entrectinib, lorlatinib and repotrectinib. After introducing each agent’s properties, we provide suggestions on the best approaches to identify resistance mechanisms at an early stage, and we speculate on the most appropriate second-line therapies for patients who reported disease progression following crizotinib administration.

Abstract

The treatment of patients affected by non-small cell lung cancer (NSCLC) has been revolutionised by the discovery of druggable mutations. ROS1 (c-ros oncogene) is one gene with druggable mutations in NSCLC. ROS1 is currently targeted by several specific tyrosine kinase inhibitors (TKIs), but only two of these, crizotinib and entrectinib, have received Food and Drug Administration (FDA) approval. Crizotinib is a low molecular weight, orally available TKI that inhibits ROS1, MET and ALK and is considered the gold standard first-line treatment with demonstrated significant activity for lung cancers harbouring ROS1 gene rearrangements. However, crizotinib resistance often occurs, making the treatment of ROS1-positive lung cancers more challenging. A great effort has been undertaken to identify a new generation or ROS1 inhibitors. In this review, we briefly introduce the biology and role of ROS1 in lung cancer and discuss the underlying acquired mechanisms of resistance to crizotinib and the promising new agents able to overcome resistance mechanisms and offer alternative efficient therapies.