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Erdafitinib, an inhibitor of fibroblast growth factor receptor, was tested in previously treated patients with advanced urothelial cancer with FGFR alterations. The objective response rate was 40%, with treatment-related adverse events of grade 3 or higher reported in nearly half the patients.

Fibroblast growth factor receptors are growth factor receptor tyrosine kinases, exerting their roles in embryogenesis, tissue homeostasis, and development of breast cancer. Recent genetic studies have identified some subtypes of fibroblast growth factor receptors as strong genetic loci associated with breast cancer. In this article, we review the recent epidemiological findings and experiment results of fibroblast growth factor receptors in breast cancer. First, we summarized the structure and physiological function of fibroblast growth factor receptors in humans. Then, we discussed the common genetic variations in fibroblast growth factor receptors that affect breast cancer risk. In addition, we also introduced the potential roles of each fibroblast growth factor receptors isoform in breast cancer. Finally, we explored the potential therapeutics targeting fibroblast growth factor receptors for breast cancer. Based on the biological mechanisms of fibroblast growth factor receptors leading to the pathogenesis in breast cancer, targeting fibroblast growth factor receptors may provide new opportunities for breast cancer therapeutic strategies.

Background This Phase 1b/2 study assessed the efficacy in terms of objective response rate (ORR) of the FGFR1/2/3 kinase inhibitor derazantinib as monotherapy or in combination with atezolizumab in patients with metastatic urothelial cancer (mUC) and FGFR1-3 genetic aberrations (FGFR1-3GA). Methods This multicenter, open-label study comprised 5 substudies. In Substudies 1 and 5, patients with mUC with FGFR1–3GA received derazantinib monotherapy (300 mg QD in Substudy 1, 200 mg BID in Substudy 5). In Substudy 2, patients with any solid tumor received atezolizumab 1200 mg every 3 weeks plus derazantinib 200 or 300 mg QD. In Substudy 3, patients with mUC harboring FGFR1–3GA received derazantinib 200 mg BID plus atezolizumab 1200 mg every 3 weeks. In Substudy 4, patients with FGFR inhibitor-resistant mUC harboring FGFR1–3GA received derazantinib 300 mg QD monotherapy or derazantinib 300 mg QD plus atezolizumab 1200 mg every 3 weeks. Results The ORR for Substudies 1 and 5 combined was 4/49 (8.2%, 95% confidence interval = 2.3% to 19.6%), which was based on 4 partial responses. The ORR in Substudy 4 was 1/7 (14.3%, 95% confidence interval = 0.4% to 57.9%; 1 partial response for derazantinib 300 mg monotherapy, zero for derazantinib 300 mg plus atezolizumab 1200 mg). In Substudy 2, derazantinib 300 mg plus atezolizumab 1200 mg was identified as a recommended dose for Phase 2. Only 2 patients entered Substudy 3. Conclusions Derazantinib as monotherapy or in combination with atezolizumab was well-tolerated but did not show sufficient efficacy to warrant further development in mUC. Clinicaltrials.gov NCT04045613, EudraCT 2019-000359-15

Key Points Fibroblast growth factor (FGF) signalling controls a myriad of processes in embryonic development and in tissue homeostasis and metabolism in the adult. Recent structural studies have provided a glimpse of the complexity of molecular control that is in place to fine-tune this signalling system to enable it to produce specific signalling outputs in diverse biological contexts. The interaction of FGFs with heparan sulphate glycosaminoglycan chains of heparan sulphate proteoglycans in the pericellular and extracellular matrix defines their mode of action, that is, whether an FGF acts in a paracrine or endocrine fashion. It also determines the shape of gradient formed by a paracrine FGF ligand in the extracellular matrix, which in turn is a determinant of the biological response to that ligand. In addition to mechanisms common to all FGFs, such as the interaction with heparan sulphate, the biological activity of individual ligands or ligand subfamilies is regulated by mechanisms unique to these ligands: amino-terminal alternative splicing controls the activity of FGF8 subfamily ligands; homodimerization autoinhibits the activity of FGF9 subfamily ligands; and site-specific proteolytic cleavage inactivates the phosphaturic hormone FGF23. Alternative splicing in the extracellular immunoglobulin-like domain 3 (D3) of FGF receptor 1 (FGFR1), FGFR2 and FGFR3 primarily determines the ligand-binding specificity of these receptors. This splicing event is fundamental to the establishment of directional paracrine FGF signalling between the epithelium and the mesenchyme, which underlies the coordinated cellular processes that govern organ development. Klotho co-receptors convert FGFRs into specific receptors for endocrine FGFs by a dual mechanism; these co-receptors not only enhance the binding affinity of FGFRs for endocrine FGFs but concomitantly suppress the binding of paracrine FGFs to FGFRs. The finding that heparan sulphate is dispensable for signalling by endocrine FGFs implies that Klotho co-receptors also promote FGFR dimerization upon endocrine FGF binding, which is required for FGFR activation. The structural findings suggest that there may be no functional redundancy among FGF ligands, and genetic data support this conclusion. Hence, future studies should concentrate on identifying novel ligand-specific functions of FGF signalling. Structural data has provided insight into the molecular mechanisms that modulate fibroblast growth factor (FGF) signalling to generate distinct biological outputs in development, tissue homeostasis and metabolism. Mechanisms include alternative splicing of ligand and receptor, homodimerization and site-specific proteolytic cleavage of ligand, and interaction of ligand and receptor with heparan sulphate and Klotho co-receptors. Fibroblast growth factors (FGFs) mediate a broad range of functions in both the developing and adult organism. The accumulated wealth of structural information on the FGF signalling pathway has begun to unveil the underlying molecular mechanisms that modulate this system to generate a myriad of distinct biological outputs in development, tissue homeostasis and metabolism. At the ligand and receptor level, these mechanisms include alternative splicing of the ligand (FGF8 subfamily) and the receptor (FGFR1–FGFR3), ligand homodimerization (FGF9 subfamily), site-specific proteolytic cleavage of the ligand (FGF23), and interaction of the ligand and the receptor with heparan sulphate cofactor and Klotho co-receptor.

The human FGF receptors (FGFRs) play critical roles in various human cancers, and several FGFR inhibitors are currently under clinical investigation. Resistance usually results from selection for mutant kinases that are impervious to the action of the drug or from up-regulation of compensatory signaling pathways. Preclinical studies have demonstrated that resistance to FGFR inhibitors can be acquired through mutations in the FGFR gatekeeper residue, as clinically observed for FGFR4 in embryonal rhabdomyosarcoma and neuroendocrine breast carcinomas. Here we report on the use of a structure-based drug design to develop two selective, next-generation covalent FGFR inhibitors, the FGFR irreversible inhibitors 2 (FIIN-2) and 3 (FIIN-3). To our knowledge, FIIN-2 and FIIN-3 are the first inhibitors that can potently inhibit the proliferation of cells dependent upon the gatekeeper mutants of FGFR1 or FGFR2, which confer resistance to first-generation clinical FGFR inhibitors such as NVP-BGJ398 and AZD4547. Because of the conformational flexibility of the reactive acrylamide substituent, FIIN-3 has the unprecedented ability to inhibit both the EGF receptor (EGFR) and FGFR covalently by targeting two distinct cysteine residues. We report the cocrystal structure of FGFR4 with FIIN-2, which unexpectedly exhibits a “DFG-out” covalent binding mode. The structural basis for dual FGFR and EGFR targeting by FIIN3 also is illustrated by crystal structures of FIIN-3 bound with FGFR4 V550L and EGFR L858R. These results have important implications for the design of covalent FGFR inhibitors that can overcome clinical resistance and provide the first example, to our knowledge, of a kinase inhibitor that covalently targets cysteines located in different positions within the ATP-binding pocket. Significance Inhibitors of the FGF receptors (FGFRs) are currently under clinical investigation for the treatment of various cancers. All currently approved kinase inhibitors eventually are rendered useless by the emergence of drug-resistant tumors. We used structure-based drug design to develop the first, to our knowledge, selective, next-generation covalent FGFR inhibitors that can overcome the most common form of kinase inhibitor resistance, the mutation of the so-called “gatekeeper” residue located in the ATP-binding pocket. We also describe a novel kinase inhibitor design strategy that uses a single electrophile to target covalently cysteines that are located in different positions within the ATP-binding pocket. These results have important implications for the design of covalent FGFR inhibitors that can overcome clinical resistance.

Fibroblast growth factor receptor (FGFR) gene alterations are relatively frequent in lung squamous cell carcinoma (LSCC) and are a potential targets for therapy with FGFR inhibitors. However, little is known regarding the clinicopathologic features associated with FGFR alterations. The angiokinase inhibitor nintedanib has shown promising activity in clinical trials for non‐small cell lung cancer. We have now applied next‐generation sequencing (NGS) to characterize FGFR alterations in LSCC patients as well as examined the antitumor activity of nintedanib in LSCC cell lines positive for FGFR1 copy number gain (CNG). The effects of nintedanib on the proliferation of and FGFR signaling in LSCC cell lines were examined in vitro, and its effects on tumor formation were examined in vivo. A total of 75 clinical LSCC specimens were screened for FGFR alterations by NGS. Nintedanib inhibited the proliferation of FGFR1 CNG‐positive LSCC cell lines in association with attenuation of the FGFR1–ERK signaling pathway in vitro and in vivo. FGFR1 CNG (10.7%), FGFR1 mutation (2.7%), FGFR2 mutation (2.7%), FGFR4 mutation (5.3%), and FGFR3 fusion (1.3%) were detected in LSCC specimens by NGS. Clinicopathologic features did not differ between LSCC patients positive or negative for FGFR alterations. However, among the 36 patients with disease recurrence after surgery, prognosis was significantly worse for those harboring FGFR alterations. Screening for FGFR alterations by NGS warrants further study as a means to identify patients with LSCC recurrence after surgery who might benefit from nintedanib therapy. The angiokinase inhibitor nintedanib is a potential targeted agent for lung squamous cell carcinoma (LSCC) positive for genetic alterations affecting FGFR genes. We screened 75 LSCC specimens for FGFR alterations by next‐generation sequencing and thereby identified various such genetic changes including copy number gain, mutations, and a fusion in 15 of the 75 (20.0%) cases. Among the patients with relapse after surgery, the presence of FGFR alterations was associated with a significantly shorter overall survival.

Fibroblast growth factor receptor (FGFR) 2 gene alterations are involved in the pathogenesis of cholangiocarcinoma. Pemigatinib is a selective, potent, oral inhibitor of FGFR1, 2, and 3. This study evaluated the safety and antitumour activity of pemigatinib in patients with previously treated, locally advanced or metastatic cholangiocarcinoma with and without FGFR2 fusions or rearrangements. In this multicentre, open-label, single-arm, multicohort, phase 2 study (FIGHT-202), patients aged 18 years or older with disease progression following at least one previous treatment and an Eastern Cooperative Oncology Group (ECOG) performance status of 0–2 recruited from 146 academic or community-based sites in the USA, Europe, the Middle East, and Asia were assigned to one of three cohorts: patients with FGFR2 fusions or rearrangements, patients with other FGF/FGFR alterations, or patients with no FGF/FGFR alterations. All enrolled patients received a starting dose of 13·5 mg oral pemigatinib once daily (21-day cycle; 2 weeks on, 1 week off) until disease progression, unacceptable toxicity, withdrawal of consent, or physician decision. The primary endpoint was the proportion of patients who achieved an objective response among those with FGFR2 fusions or rearrangements, assessed centrally in all patients who received at least one dose of pemigatinib. This study is registered with ClinicalTrials.gov, NCT02924376, and enrolment is completed. Between Jan 17, 2017, and March 22, 2019, 146 patients were enrolled: 107 with FGFR2 fusions or rearrangements, 20 with other FGF/FGFR alterations, 18 with no FGF/FGFR alterations, and one with an undetermined FGF/FGFR alteration. The median follow-up was 17·8 months (IQR 11·6–21·3). 38 (35·5% [95% CI 26·5–45·4]) patients with FGFR2 fusions or rearrangements achieved an objective response (three complete responses and 35 partial responses). Overall, hyperphosphataemia was the most common all-grade adverse event irrespective of cause (88 [60%] of 146 patients). 93 (64%) patients had a grade 3 or worse adverse event (irrespective of cause); the most frequent were hypophosphataemia (18 [12%]), arthralgia (nine [6%]), stomatitis (eight [5%]), hyponatraemia (eight [5%]), abdominal pain (seven [5%]), and fatigue (seven [5%]). 65 (45%) patients had serious adverse events; the most frequent were abdominal pain (seven [5%]), pyrexia (seven [5%]), cholangitis (five [3%]), and pleural effusion (five [3%]). Overall, 71 (49%) patients died during the study, most frequently because of disease progression (61 [42%]); no deaths were deemed to be treatment related. These data support the therapeutic potential of pemigatinib in previously treated patients with cholangiocarcinoma who have FGFR2 fusions or rearrangements. Incyte Corporation.

Durvalumab is a programmed death-ligand 1 (PD-L1) inhibitor with clinical activity in advanced urothelial cancer (AUC) 1 . AUC is characterized by several recurrent targetable genomic alterations 2 – 5 . This study ( NCT02546661 , BISCAY) combined durvalumab with relevant targeted therapies in biomarker-selected chemotherapy-refractory AUC populations including: (1) fibroblast growth factor receptor (FGFR) inhibitors in tumors with FGFR DNA alterations (FGFRm); (2) pharmacological inhibitor of the enzyme poly-ADP ribose polymerase (PARP) in tumors with and without DNA homologous recombination repair deficiency (HRRm); and (3) TORC1/2 inhibitors in tumors with DNA alteration to the mTOR/PI3K pathway 3 – 5 .This trial adopted a new, biomarker-driven, multiarm adaptive design. Safety, efficacy and relevant biomarkers were evaluated. Overall, 391 patients were screened of whom 135 were allocated to one of six study arms. Response rates (RRs) ranged 9–36% across the study arms, which did not meet efficacy criteria for further development. Overall survival (OS) and progression-free survival (PFS) were similar in the combination arms and durvalumab monotherapy arm. Biomarker analysis showed a correlation between circulating plasma-based DNA (ctDNA) and tissue for FGFRm. Sequential circulating tumor DNA analysis showed that changes to FGFRm correlated with clinical outcome. Our data support the clinical activity of FGFR inhibition and durvalumab monotherapy but do not show increased activity for any of the combinations. These findings question the targeted/immune therapy approach in AUC. The adaptive, biomarker-driven BISCAY trial evaluating durvalumab with targeted agents in patients with metastatic urothelial carcinoma based on tumor genomic alterations finds no added clinical benefit over durvalumab monotherapy.

Background: Breast cancer is one of the most common malignancies in women. Genome-wide association studies have identified FGFR2 as a breast cancer susceptibility gene. Common variation in other fibroblast growth factor (FGF) receptors might also modify risk. We tested this hypothesis by studying genotyped single-nucleotide polymorphisms (SNPs) and imputed SNPs in FGFR1, FGFR3, FGFR4 and FGFRL1 in the Breast Cancer Association Consortium. Methods: Data were combined from 49 studies, including 53 835 cases and 50 156 controls, of which 89 050 (46 450 cases and 42 600 controls) were of European ancestry, 12 893 (6269 cases and 6624 controls) of Asian and 2048 (1116 cases and 932 controls) of African ancestry. Associations with risk of breast cancer, overall and by disease sub-type, were assessed using unconditional logistic regression. Results: Little evidence of association with breast cancer risk was observed for SNPs in the FGF receptor genes. The strongest evidence in European women was for rs743682 in FGFR3 ; the estimated per-allele odds ratio was 1.05 (95% confidence interval=1.02–1.09, P= 0.0020), which is substantially lower than that observed for SNPs in FGFR2. Conclusion: Our results suggest that common variants in the other FGF receptors are not associated with risk of breast cancer to the degree observed for FGFR2 .

While fibroblast growth factor receptors (FGFRs) are involved in several biological pathways and FGFR inhibitors may be useful in the treatment of squamous non-small cell lung cancer (Sq-NSCLC), FGFR aberrations are not well characterized in Sq-NSCLC. We comprehensively evaluated FGFR expression, fusions, and variants in 40 fresh-frozen primary Sq-NSCLC (stage IA3–IV) samples and tumor-adjacent normal tissues using real-time PCR and next-generation sequencing (NGS). Protein expression of FGFR1–3 and amplification of FGFR1 were also analyzed. FGFR1 and FGFR4 median gene expression was significantly (p < 0.001) decreased in tumors compared with normal tissue. Increased FGFR3 expression enhanced the recurrence risk (hazard ratio 4.72, p = 0.029), while high FGFR4 expression was associated with lymph node metastasis (p = 0.036). Enhanced FGFR1 gene expression was correlated with FGFR1 protein overexpression (r = 0.75, p = 0.0003), but not with FGFR1 amplification. NGS revealed known pathogenic FGFR2,3 variants, an FGFR3::TACC3 fusion, and a novel TACC1::FGFR1 fusion together with FGFR1,2 variants of uncertain significance not previously reported in Sq-NSCLC. These findings expand our knowledge of the Sq-NSCLC molecular background and show that combining different methods increases the rate of FGFR aberrations detection, which may improve patient selection for FGFRi treatment.