A phase 1 study of oral ASP5878, a selective small-molecule inhibitor of fibroblast growth factor receptors 1-4, as a single dose and multiple doses in patients with solid malignancies

Ocular toxicities of fibroblast growth factor receptor inhibitors: A review

Fibroblast growth factor receptor (FGFR) inhibitors are an emerging class of small molecule targeted cancer drugs with promising therapeutic possibilities for a wide variety of malignancies. While ocular adverse events from FGFR inhibitors are reported in clinical trials, subsequent case studies continue to reveal new toxicities. Disease pathology affecting multiple parts of the eye has been reported, but the ocular surface and the retina are the most commonly encountered areas affected by FGFR inhibitors, manifesting as dry eye and FGFR inhibitor-associated retinopathy, respectively. Corneal thinning and melt is a rare but serious and potentially vision-threatening complication of FGFR inhibitor toxicity. Similarities between toxicities observed from other targeted cancer therapy drugs and FGFR inhibitors may help us understand underlying pathophysiological changes. The management of these adverse events requires close ophthalmologic follow-up and may require discontinuation of the offending agents in some cases.

Current scenario of pyrazole hybrids with in vivo therapeutic potential against cancers

Chemotherapeutics occupy a pivotal role in the medication of different types of cancers, but the prevalence and mortality rates of cancer remain high. The drug resistance and low specificity of current available chemotherapeutics are the main barriers for the effective cancer chemotherapy, evoking an immediate need for the development of novel anticancer agents. Pyrazole is a highly versatile five-membered heterocycle with two adjacent nitrogen atoms and possesses remarkable therapeutic effects and robust pharmacological potency. The pyrazole derivatives especially pyrazole hybrids have demonstrated potent in vitro and in vivo efficacies against cancers through multiple mechanisms, inclusive of apoptosis induction, autophagy regulation, and cell cycle disruption. Moreover, several pyrazole hybrids such as crizotanib (pyrazole-pyridine hybrid), erdafitinib (pyrazole-quinoxaline hybrid) and ruxolitinib (pyrazole-pyrrolo [2,3-d]pyrimidine hybrid) have already been approved for the cancer therapy, revealing that pyrazole hybrids are useful scaffolds to develop novel anticancer agents. The purpose of this review is to summarize the current scenario of pyrazole hybrids with potential in vivo anticancer efficacy along with mechanisms of action, toxicity, and pharmacokinetics, covering papers published in recent 5 years (2018-present), to facilitate further rational exploitation of more effective candidates.

The FGF/FGFR signalling mediated anti-cancer drug resistance and therapeutic intervention

ABSTRACT Fibroblast Growth Factor (FGF) ligands and their receptors are crucial factors driving chemoresistance in several malignancies, challenging the efficacy of currently available anti-cancer drugs. The Fibroblast growth factor/receptor (FGF/FGFR) signalling malfunctions in tumor cells, resulting in a range of molecular pathways that may impact its drug effectiveness. Deregulation of cell signalling is critical since it can enhance tumor growth and metastasis. Overexpression and mutation of FGF/FGFR induce regulatory changes in the signalling pathways. Chromosomal translocation facilitating FGFR fusion production aggravates drug resistance. Apoptosis is inhibited by FGFR-activated signalling pathways, reducing multiple anti-cancer medications' destructive impacts. Angiogenesis and epithelial-mesenchymal transition (EMT) are facilitated by FGFRs-dependent signalling, which correlates with drug resistance and enhances metastasis. Further, lysosome-mediated drug sequestration is another prominent method of resistance. Inhibition of FGF/FGFR by following a plethora of therapeutic approaches such as covalent and multitarget inhibitors, ligand traps, monoclonal antibodies, recombinant FGFs, combination therapy, and targeting lysosomes and micro RNAs would be helpful. As a result, FGF/FGFR suppression treatment options are evolving nowadays. To increase positive impacts, the processes underpinning the FGF/FGFR axis' role in developing drug resistance need to be clarified, emphasizing the need for more studies to develop novel therapeutic options to address this significant problem. Communicated by Ramaswamy H. Sarma.

Ocular toxicity of investigational anti-cancer drugs in early phase clinical trials

Ocular toxicities arising from anti-cancer drugs occur sporadically and are sometimes underestimated because they are not life-threatening. Reports focusing on ocular toxicities from cancer therapy are limited. We investigated the detailed progress of ocular toxicities of anti-cancer drugs including first-in-class ones. A retrospective review of medical records was conducted for patients who were involved in early phase clinical trials with scheduled ophthalmologic examinations according to their protocols between January 2014 and August 2021. Patients with ocular toxicity suspected to be related to the investigational drugs in the ophthalmic examination were investigated in detail. In total, 37 ocular toxicities related to investigational drugs occurred in 7.6% of patients (33/434). The median age of the 33 patients was 61 years (range, 33-76 years), and 20 were male. Causal drugs with a high incidence of ocular toxicities were HSP90 inhibitors and FGFR inhibitors. Retinopathy was most frequent, while conjunctivitis, dry eye, keratitis, keratopathy, and uveitis were also observed. Dim vision as a subjective finding was a unique adverse event. Most patients developed ocular toxicities even though their dose was below the drug's maximum tolerated dose. Except for one case, all ocular toxicities occurred bilaterally. About 60% (22/37) of ocular toxicity cases needed a temporary hold of the drug. All except for three cases fully recovered. This study reported the risks and timing of the onset of a variety of ocular toxicities of anti-cancer drugs, which were fundamentally controllable. (Trial registration number. Retrospectively registered).

Patient Selection Approaches in FGFR Inhibitor Trials-Many Paths to the Same End?

Inhibitors of fibroblast growth factor receptor (FGFR) signaling have been investigated in various human cancer diseases. Recently, the first compounds received FDA approval in biomarker-selected patient populations. Different approaches and technologies have been applied in clinical trials, ranging from protein (immunohistochemistry) to mRNA expression (e.g., RNA in situ hybridization) and to detection of various DNA alterations (e.g., copy number variations, mutations, gene fusions). We review, here, the advantages and limitations of the different technologies and discuss the importance of tissue and disease context in identifying the best predictive biomarker for FGFR targeting therapies.

Favorable Management of Repeated Serous Retinal Detachment with Continued Tumor Response in a Patient with Intrahepatic Cholangiocarcinoma During Treatment with Pemigatinib: A Case Report

Pemigatinib is a fibroblast growth factor receptor inhibitor (FGFRi) approved for the treatment of patients with previously treated biliary tract cancer with FGFR2 fusion. Although infrequent, ocular toxicity manifested as serous retinal detachment (SRD) has been observed and is regarded as a serious side effect. We herein report the case of a 54-year-old woman with unresectable cholangiocarcinoma-initiated pemigatinib after failure of gemcitabine plus S-1 (GS). Although the patient experienced repeated SRD after pemigatinib, dose interruption and dose reduction of pemigatinib from 13.5 mg to 9 mg, and from 9 mg to 4.5 mg led to complete recovery of SRD, and continued tumor shrinkage.

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.

Selective FGFR/FGF pathway inhibitors: inhibition strategies, clinical activities, resistance mutations, and future directions

Introduction: Fibroblast growth factor receptor (FGFR)/fibroblast growth factor (FGF) is a pathway characterized by recurring alterations in cancer. Its dysregulations enhance cancer cell proliferation, survival, migration and invasion, as well as angiogenesis and immune evasion.Areas covered: FGFR/FGF selective inhibitors belong to a broad class of drugs with some being approved for specific indications and others under investigation in ongoing phase I and II clinical trials. In this review, all available clinical data from trials on selective FGFR/FGF inhibitors as well as described resistance mutations and mechanisms are presented. FGFR/FGF pathway inhibitors are classified according to the mechanism they employ to dampen/suppress signaling and to the preferred FGFR binding mode when X-ray crystal structure is available.Expert opinion: Data presented suggests the general actionability of FGFR1,2,3 mutations and fusions across histologies, whereas FGFR1,2,3 amplifications alone are poor predictors of response to tyrosine kinase inhibitors. Overexpression on immunohistochemistry (IHC) of FGF19, the stimulatory ligand of FGFR4, can predict response to FGFR selective inhibitors in hepatocellular carcinoma. Whereas IHC overexpression of FGFR1,2,3 is not sufficient to predict benefit from FGFR inhibitors across solid tumors. FGFR1,2,3 mRNA overexpression can predict response even in absence of structural alteration. Data on resistance mutations suggests the need for new inhibitors to overcome gatekeeper mutations.

Comprehensive functional evaluation of variants of fibroblast growth factor receptor genes in cancer

Various genetic alterations of the fibroblast growth factor receptor (FGFR) family have been detected across a wide range of cancers. However, inhibition of FGFR signaling by kinase inhibitors demonstrated limited clinical effectiveness. Herein, we evaluated the transforming activity and sensitivity of 160 nonsynonymous FGFR mutations and ten fusion genes to seven FGFR tyrosine kinase inhibitors (TKI) using the mixed-all-nominated-in-one (MANO) method, a high-throughput functional assay. The oncogenicity of 71 mutants was newly discovered in this study. The FGFR TKIs showed anti-proliferative activities against the wild-type FGFRs and their fusions, while several hotspot mutants were relatively resistant to those TKIs. The drug sensitivities assessed with the MANO method were well concordant with those evaluated using in vitro and in vivo assays. Comprehensive analysis of published FGFR structures revealed a possible mechanism through which oncogenic FGFR mutations reduce sensitivity to TKIs. It was further revealed that recurrent compound mutations within FGFRs affect the transforming potential and TKI-sensitivity of corresponding kinases. In conclusion, our study suggests the importance of selecting suitable inhibitors against individual FGFR variants. Moreover, it reveals the necessity to develop next-generation FGFR inhibitors, which are effective against all oncogenic FGFR variants.

Fibroblast Growth Factor Receptor (FGFR) Signaling in GIST and Soft Tissue Sarcomas

Sarcomas are a heterogeneous group of rare malignancies originating from mesenchymal tissues with limited therapeutic options. Recently, alterations in components of the fibroblast growth factor receptor (FGFR) signaling pathway have been identified in a range of different sarcoma subtypes, most notably gastrointestinal stromal tumors, rhabdomyosarcomas, and liposarcomas. These alterations include genetic events such as translocations, mutations, and amplifications as well as transcriptional overexpression. Targeting FGFR has therefore been proposed as a novel potential therapeutic approach, also in light of the clinical activity shown by multi-target tyrosine kinase inhibitors in specific subtypes of sarcomas. Despite promising preclinical evidence, thus far, clinical trials have enrolled very few sarcoma patients and the efficacy of selective FGFR inhibitors appears relatively low. Here, we review the known alterations of the FGFR pathway in sarcoma patients as well as the preclinical and clinical evidence for the use of FGFR inhibitors in these diseases. Finally, we discuss the possible reasons behind the current clinical data and highlight the need for biomarker stratification to select patients more likely to benefit from FGFR targeted therapies.

Advantages and Disadvantages of Different Treatment Methods in Achondroplasia: A Review

Achondroplasia (ACH) is a disease caused by a missense mutation in the FGFR3 (fibroblast growth factor receptor 3) gene, which is the most common cause of short stature in humans. The treatment of ACH is necessary and urgent because untreated achondroplasia has many complications, both orthopedic and neurological, which ultimately lead to disability. This review presents the current and potential pharmacological treatments for achondroplasia, highlighting the advantages and disadvantages of all the drugs that have been demonstrated in human and animal studies in different stages of clinical trials. The article includes the potential impacts of drugs on achondroplasia symptoms other than short stature, including their effects on spinal canal stenosis, the narrowing of the foramen magnum and the proportionality of body structure. Addressing these effects could significantly improve the quality of life of patients, possibly reducing the frequency and necessity of hospitalization and painful surgical procedures, which are currently the only therapeutic options used. The criteria for a good drug for achondroplasia are best met by recombinant human growth hormone at present and will potentially be met by vosoritide in the future, while the rest of the drugs are in the early stages of clinical trials.

Inhibition of FGF-FGFR and VEGF-VEGFR signalling in cancer treatment

The sites of targeted therapy are limited and need to be expanded. The FGF‐FGFR signalling plays pivotal roles in the oncogenic process, and FGF/FGFR inhibitors are a promising method to treat FGFR‐altered tumours. The VEGF‐VEGFR signalling is the most crucial pathway to induce angiogenesis, and inhibiting this cascade has already got success in treating tumours. While both their efficacy and antitumour spectrum are limited, combining FGF/FGFR inhibitors with VEGF/VEGFR inhibitors are an excellent way to optimize the curative effect and expand the antitumour range because their combination can target both tumour cells and the tumour microenvironment. In addition, biomarkers need to be developed to predict the efficacy, and combination with immune checkpoint inhibitors is a promising direction in the future. The article will discuss the FGF‐FGFR signalling pathway, the VEGF‐VEGFR signalling pathway, the rationale of combining these two signalling pathways and recent small‐molecule FGFR/VEGFR inhibitors based on clinical trials.

Evaluation of FGFR inhibitor ASP5878 as a drug candidate for achondroplasia

Achondroplasia is caused by gain-of-function mutations in FGFR3 gene and leads to short-limb dwarfism. A stabilized analogue of C-type natriuretic peptide (CNP) is known to elongate bone by interacting with FGFR3 signals and thus is a promising drug candidate. However, it needs daily administration by percutaneous injection. FGFR inhibitor compounds are other drug candidates for achondroplasia because they directly fix the mutant protein malfunction. Although FGFR inhibitors elongate the bone of model mice, their adverse effects are not well studied. In this study, we found that a new FGFR inhibitor, ASP5878, which was originally developed as an anti-cancer drug, elongated the bone of achondroplasia model male mice at the dose of 300 μg/kg, which confers an AUC of 275 ng·h/ml in juvenile mice. Although ASP5878 was less effective in bone elongation than a CNP analogue, it is advantageous in that ASP5878 can be administered orally. The AUC at which minimal adverse effects were observed (very slight atrophy of the corneal epithelium) was 459 ng·h/ml in juvenile rats. The positive discrepancy between AUCs that brought efficacy and minimal adverse effect suggests the applicability of ASP5878 to achondroplasia in the clinical setting. We also analyzed effects of ASP5878 in a patient-specific induced pluripotent stem cell (iPSC) model for achondroplasia and found the effects on patient chondrocyte equivalents. Nevertheless, cautious consideration is needed when referring to safety data obtained from its application to adult patients with cancer in clinical tests.

Clinical complexity of utilizing FGFR inhibitors in cancer therapeutics

INTRODUCTION

Fibroblast growth factor receptors (FGFR 1-4) are a highly conserved family of receptor tyrosine kinases, involved in several physiological processes. Genetic aberrations of FGFRs and their ligands, fibroblast growth factors (FGFs) are involved in several pathological processes including cancer. The FGF-FGFR axis has emerged as a treatment target in oncology. Because these aberrations drive cancer progression, the development of FGFR targeted therapies have been accelerated.

AREAS COVERED

In this comprehensive review, we evaluate molecular pathology and targeted therapies to FGFRs. We reviewed the evidence for safety and efficacy from preclinical and clinical studies (phase I-III) of FGFR targeted therapies. We also discuss potential challenges in bringing these targeted therapies from bench to bedside and the potential opportunities.

EXPERT OPINION

Despite the challenges of the clinical development of FGFR targeted therapies, two FGFR small-molecule inhibitors, namely Erdafitinib and Pemigatinib, are FDA approved for urothelial cancer and cholangiocarcinoma, respectively. Understanding and detection of FGFR genomic aberrations, protein overexpression and the development of isoform-specific inhibitors are factors in the clinical success of these therapies. An enhanced understanding of patient selection based on a gene signatures or biomarkers is key to success of FGFR targeted therapies.

Functions of FGFR2 corrupted by translocations in intrahepatic cholangiocarcinoma

Cholangiocarcinoma, originating from the biliary duct, represents a subset of liver cancer. With about 8000 new cases of cholangiocarcinoma diagnosed annually in the U.S., these fall into three categories: intrahepatic, peri-hilar, and extrahepatic cholangiocarcinoma. Arising from the epithelium of the bile duct, intrahepatic cholangiocarcinoma (ICC) is a universally fatal malignancy with very few treatment options. The poor prognosis and lack of molecular targeted therapies highlights ICC as a critical unmet medical need. With advances in sequencing technology, numerous chromosomal translocations have been discovered as drivers in cancer initiation and progression. Particularly in ICC, chromosomal translocations involving Fibroblast Growth Factor Receptor 2 (FGFR2) have been frequently identified, resulting in the creation of oncogenic fusion proteins. At the N-terminus, these fusion proteins share a nearly-identical FGFR2 moiety retaining an intact kinase domain and, at the C-terminus, a dimerization/oligomerization domain provided by different partner genes, including: Periphilin 1 (PPHLN1), Bicaudal family RNA binding protein 1 (BICC1), Adenosylhomocysteinase Like 1 (AHCYL1), and Transforming Acidic Coiled-Coil Containing Protein 3 (TACC3). A number of pre-clinical and clinical trials have shown the effectiveness of FGFR inhibitors in treating FGFR2 fusion-positive ICC patients. However, the efficacy of these inhibitors may be short-lived due to acquired resistance. In this review, we provide an overview of FGFR2 fusions, comparing their structures and mechanism of dimerization, examining the importance of FGFR2 as a partner gene, as well as highlighting the significance of alternative splicing of FGFR2 in these fusion proteins. In addition, we discuss various therapeutic options and their associated potencies in targeting these translocation-induced ICCs.