Fibroblast Growth Factor (FGF) Receptor/FGF Inhibitors: Novel Targets and Strategies for Optimization of Response of Solid Tumors

Clinical research in small genomically stratified patient populations

The paradigm of early drug development in cancer is shifting from 'histology-oriented' to 'molecularly oriented' clinical trials. This change can be attributed to the vast amount of tumour biology knowledge generated by large international research initiatives such as The Cancer Genome Atlas (TCGA) and the use of next generation sequencing (NGS) techniques developed in recent years. However, targeting infrequent molecular alterations entails a series of special challenges. The optimal molecular profiling method, the lack of standardised biological thresholds, inter- and intra-tumor heterogeneity, availability of enough tumour material, correct clinical trials design, attrition rate, logistics or costs are only some of the issues that need to be taken into consideration in clinical research in small genomically stratified patient populations. This article examines the most relevant challenges inherent to clinical research in these populations. Moreover, perspectives from the Academia point of view are reviewed as well as initiatives to be taken in forthcoming years.

FGFR2 mutations are associated with poor outcomes in endometrioid endometrial cancer: An NRG Oncology/Gynecologic Oncology Group study

PURPOSE

Activating FGFR2 mutations have been identified in ~10% of endometrioid endometrial cancers (ECs). We have previously reported that mutations in FGFR2 are associated with shorter disease free survival (DFS) in stage I/II EC patients. Here we sought to validate the prognostic importance of FGFR2 mutations in a large, multi-institutional patient cohort.

METHODS

Tumors were collected as part of the GOG 210 clinical trial "Molecular Staging of Endometrial Cancer" where samples underwent rigorous pathological review and had more than three years of detailed clinical follow-up. DNA was extracted and four exons encompassing the FGFR2 mutation hotspots were amplified and sequenced.

RESULTS

Mutations were identified in 144 of the 973 endometrioid ECs, of which 125 were classified as known activating mutations and were included in the statistical analyses. Consistent with FGFR2 having an association with more aggressive disease, FGFR2 mutations were more common in patients initially diagnosed with stage III/IV EC (29/170;17%) versus stage I/II EC (96/803; 12%; p=0.07, Chi-square test). Additionally, incidence of progression (progressed, recurred or died from disease) was significantly more prevalent (32/125, 26%) among patients with FGFR2 mutation versus wild type (120/848, 14%; p<0.001, Chi-square test). Using Cox regression analysis adjusting for known prognostic factors, patients with FGFR2 mutation had significantly (p<0.025) shorter progression-free survival (PFS; HR 1.903; 95% CI 1.177-3.076) and endometrial cancer specific survival (ECS; HR 2.013; 95% CI 1.096-3.696).

CONCLUSION

In summary, our findings suggest that clinical trials testing the efficacy of FGFR inhibitors in the adjuvant setting to prevent recurrence and death are warranted.

Investigational drugs targeting fibroblast growth factor receptor in the treatment of non-small cell lung cancer

INTRODUCTION

Fibroblast growth factor receptor (FGFR) due to its central role in regulating cell survival, is a promising target for cancer therapeutics. Dysregulation of the FGFR pathway has been observed in several malignancies, including non-small cell lung cancer (NSCLC) particularly in patients with squamous histology. Areas covered: The aim of this article is to review the most relevant findings of clinical trials investigating drugs targeting FGFR pathway: such as FGFR tyrosine kinase inhibitors (TKIs), FGFR monoclonal antibodies and FGF ligand traps in NSCLC patients. Expert opinion: At present, clinical activity of drugs targeting FGFR in NSCLC is disappointing. Further studies are needed in order to better identify patients who might benefit from these drugs and to clarify the mechanisms of resistance to these compounds.

Biological therapies in nonsmall cell lung cancer

Biological therapies have improved survival outcomes of advanced-stage nonsmall cell lung cancer (NSCLC). Genotype-directed therapies have changed treatment paradigms of patients with EGFR-mutant and ALK/ROS1-rearranged lung adenocarcinomas, and the list of druggable targets with demonstrated clinical actionability (BRAF, MET, RET, NTRK1 and HER2) continues to expand. Furthermore, we have incrementally understood the mechanisms of cancer immune evasion and foresee ways to effectively circumvent them, particularly at the immune checkpoint level. Drugs targeting the tumour immune-evasive PD-1 pathway have demonstrated remarkable treatment benefits in this disease, with a non-negligible fraction of patients potentially receiving long-term survival benefits. Herein, we briefly discuss the role of various medical disciplines in the management of advanced-stage NSCLC and review the most relevant biological therapies for this disease, with particular emphasis in genotype-directed therapies and immune checkpoint inhibitors.

Inhibition of the fibroblast growth factor receptor (FGFR) pathway: the current landscape and barriers to clinical application

The fibroblast growth factor/fibroblast growth factor receptor (FGF/FGFR) is a tyrosine kinase signaling pathway that has a fundamental role in many biologic processes including embryonic development, tissue regeneration, and angiogenesis. Increasing evidence indicates that this pathway plays a critical role in oncogenesis via gene amplification, activating mutations, or translocation in tumors of various histologies. With multiplex sequencing technology, the detection of FGFR aberrations has become more common and is tied to cancer cell proliferation, resistance to anticancer therapies, and neoangiogenesis. Inhibition of FGFR signaling appears promising in preclinical studies, suggesting a pathway of clinical interest in the development of targeted therapy. Phase I trials have demonstrated a manageable toxicity profile. Currently, there are multiple FGFR inhibitors under study with many non-selective (multi-kinase) inhibitors demonstrating limited clinical responses. As we progress from the first generation of non-selective drugs to the second generation of selective FGFR inhibitors, it is clear that FGFR aberrations do not behave uniformly across cancer types; thus, a deeper understanding of biomarker strategies is undoubtedly warranted. This review aims to consolidate data from recent clinical trials with a focus on selective FGFR inhibitors. As Phase II clinical trials emerge, concentration on patient selection as it pertains to predicting response to therapy, feasible methods for overcoming toxicity, and the likelihood of combination therapies should be utilized. We will also discuss qualities that may be desirable in future generations of FGFR inhibitors, with the hope that overcoming these current barriers will expedite the availability of this novel class of medications.

Unveiling changes in the landscape of patient populations in cancer early drug development

The introduction of new Molecularly Targeted Agents (MTA) has changed the landscape in Early Drug Development (EDD) over the last two decades, leading to an improvement in clinical trial design. Previous Phase 1 (Ph1) studies with cytotoxics focused on safety objectives, only recruiting heavily pre-treated cancer patients, have been left behind. In this review, we will illustrate the slow although unstoppable change that has increasingly been observed in those populations candidate to participate in EDD trials with the advent of MTA. As more evidence regarding oncogene addiction becomes available, molecular-biomarker driven selection has been implemented among Molecularly-Selected Population (MSP) studies. New Window-Of-Opportunity (WOO) and Phase 0 (Ph0) studies have been developed in order to assess whether a MTA produces the hypothetical proposed biological effect. The rising need of getting early pharmacokinetics and pharmacodynamics data has led to the conduction of Healthy Volunteer (HV) studies, in part favoured for the particular and different toxicity profile of these MTA. However, several challenges will need to be addressed in order to boost the implementation of these new clinical trial designs in the forthcoming years. Among the problems to overcome, we would highlight a better coordination effort between centers for ensuring adequate patient accrual among small patient populations and a deepening into the ethics implied in enrolling patients in studies with no therapeutic intent. However, these tribulations will be certainly compensated by the possibility of opening a new horizon of treatment for diseases with dismal prognosis.

Molecular profiling of biliary tract cancer: a target rich disease

Biliary tract cancers (BTCs) are relatively uncommon orphan tumors that have an aggressive disease course and a poor clinical outcome. Surgery is the only curative treatment, but most patients present with advanced disease and therefore have a limited survival. Gemcitabine and cisplatin based chemotherapy has been the only widely accepted standard systemic therapy regimen in these patients but these tumors can be chemoresistant, further complicating their management. In recent times, there has been considerable research in the genetics of BTC and with the advent of new, advanced technologies like next-generation sequencing (NGS) we are achieving a greater understanding of its disease biology. With the help of NGS, we have now been able to identify actionable mutations such as in the isocitrate dehydrogenase 1 (IDH1), FGFR2, BRAF and HER2/neu genes for targeted therapeutics and correlate the genetic variations with distinct clinical prognoses. This recent genetic information has the potential to make precision medicine a part of routine clinical practice for the management of BTC patients.

Emerging tyrosine kinase inhibitors for the treatment of metastatic colorectal cancer

INTRODUCTION

Colorectal cancer (CRC) is a leading cause of cancer death worldwide. Over the last decade, the addition of antibodies that block the epidermal growth factor receptor (EGFR) or angiogenesis to the classic chemotherapy backbone has improved overall survival in metastatic colorectal cancer (mCRC). However, the role of the other major targeted therapy, the tyrosine kinase inhibitors (TKIs), is not yet fully clarified.

AREAS COVERED

This review discusses key published and ongoing studies with TKIs in mCRC, the mechanisms of resistance to standard treatments that are potentially targetable with these small molecules, along with the role of biomarkers in therapeutic decision-making process.

EXPERT OPINION

The current effectiveness of TKIs is limited by two principal reasons, firstly the use of combination chemotherapy necessitates lower dose-density to manage the toxicity profile and secondly, development of these drugs has mainly been performed in molecularly unselected populations. mCRC is a heterogeneous and dynamic disease, and clinical trials with TKIs must be designed on the basis of specific molecular alterations targeted by these drugs. Success with this approach relies on identifying mutations at the time of progression, raising the importance of minimally-invasive monitoring tools. Liquid biopsies are a promising option, although this technique remains to be validated. Overall, this approach contributes to the move towards personalized and precision therapeutic strategies.

Regulation of Hepatic Stellate Cells and Fibrogenesis by Fibroblast Growth Factors

Fibroblast growth factors (FGFs) are a family of growth factors critically involved in developmental, physiological, and pathological processes, including embryogenesis, angiogenesis, wound healing, and endocrine functions. In the liver, several FGFs are produced basally by hepatocytes and hepatic stellate cells (HSCs). Upon insult to the liver, expression of FGFs in HSCs is greatly upregulated, stimulating hepatocyte regeneration and growth. Various FGF isoforms have also been shown to directly induce HSC proliferation and activation thereby enabling autocrine and paracrine regulation of HSC function. Regulation of HSCs by the endocrine FGFs, namely, FGF15/19 and FGF21, has also recently been identified. With the ability to modulate HSC proliferation and transdifferentiation, targeting FGF signaling pathways constitutes a promising new therapeutic strategy to treat hepatic fibrosis.