Targeting the Fibroblast Growth Factor Receptor (FGFR) in Advanced Cholangiocarcinoma: Clinical Trial Progress and Future Considerations

CLDN18.2: a potential nanotherapeutic target for cholangiocarcinoma

Cholangiocarcinoma (CCA) is an extremely malignant and aggressive primary liver tumor that has become increasingly prevalent in recent years. Unfortunately, the prognosis for patients diagnosed with CCA remains exceptionally poor. Currently, the primary treatment options include surgery and chemotherapy. However, the effectiveness of postoperative chemotherapy is limited, characterized by a brief duration of remission and high rates of recurrence and metastasis, resulting in minimal survival benefits for patients. Therefore, there is an urgent need to develop new therapeutic strategies that are both safer and more effective. In recent years, as oncology research has progressed, Claudin 18.2 (CLDN18.2)-targeted therapy has emerged, showing promise for improving the survival of patients with CLDN18.2-positive cancers. Studies suggest that combining new agents targeting CLDN18.2 with standard cytotoxic therapies offers significant survival benefits in CLDN18.2-positive solid tumors, which is expected to provide a more effective treatment option for patients with advanced cholangiocarcinoma. While existing immune checkpoints or therapeutic targets have limitations, such as low positivity rates and minimal absolute improvement in patient survival time, drugs that target FGFR, IDH, and Her-2, along with antiangiogenic agents, have shown promise for patients with advanced malignancies affecting the bile ducts. Therefore, exploring these novel therapeutic strategies may yield new insights for precision treatment of cholangiocarcinoma in the future. This review aims to focus on the potential application of CLDN18.2 in treating solid tumors, particularly cholangiocarcinoma, to systematically summarize research progress related to this target and thoroughly examine its value in diagnosing, treating, and assessing the prognosis of cholangiocarcinoma.

Analysis of Two Oncological Drugs Futibatinib and Capivasertib via Ion-Pairing With Eosin Y as a Spectrofluorimetric and Spectrophotometric Probe

Using spectroscopy, two quick and sensitive analytical methods based on eosin Y ion pairing were developed and assessed in order to determine capivasertib and futibatinib with high selectivity and sensitivity. The quenching impact of futibatinib or capivasertib on the eosin Y's fluorescence at a pH 3.8 and 3.3 for futibatinib and capivasertib, respectively, in 0.1-M acetate buffer solution was observed using two spectrofluorometric techniques. These techniques are regarded as the original spectrofluorometric techniques for the assay of futibatinib and capivasertib. For futibatinib and capivasertib, the quenching effect on fluorescence was ranged from 100 to 1000 and 150 to 1500 ng mL-1, respectively. The absorbance of the generated ion-pair was measured using two different spectrophotometric methods at 550 nm in aqueous buffered solutions with pH values of 3.8 and 3.3 for futibatinib and capivasertib, respectively. In the concentration range of 1.0-10.0 and 2.0-10.0 μg mL-1, Beer's law was followed. The four approaches were applied to the analysis of dosage forms with a high percent recovery successfully, and they were assessed in compliance with ICH guidelines.

EIF3B stabilizes PCNA by counteracting SYVN1-mediated ubiquitination to serve as a promotor in cholangiocarcinoma

Cholangiocarcinoma, a prevalent hepatic malignancy, exhibits a progressively rising incidence. While Eukaryotic translation initiation factor 3 subunit B (EIF3B) has been implicated in the occurrence and development of various cancers, its specific roles in cholangiocarcinoma remain unexplored. Immunohistochemical (IHC) analysis was employed to detect EIF3B/PCNA expression in cholangiocarcinoma. Cells were manipulated using short hairpin RNA (shRNA)-mediated lentiviruses or overexpression plasmids. Statistical significance was assessed using the Student's t-test and one-way ANOVA, with P < 0.05 considered statistically significant. EIF3B exhibited robust expression in cholangiocarcinoma, demonstrating a significant correlation with the pathological grade of cholangiocarcinoma patients. Furthermore, modulation of EIF3B expression, either depletion or elevation, demonstrated the ability to inhibit or enhance cholangiocarcinoma cell survival and migration in vitro. Mechanistically, we identified Proliferating Cell Nuclear Antigen (PCNA) as a downstream gene of EIF3B, driving cholangiocarcinoma. EIF3B stabilized PCNA by inhibiting PCNA ubiquitination, a process mediated by E3 ligase SYVN1. Similar to EIF3B, PCNA levels were also abundant in cholangiocarcinoma, and knocking down PCNA impeded cholangiocarcinoma development. Intriguingly, silencing PCNA attenuated the promotion induced by EIF3B overexpression. Furthermore, the elevated P21 protein level in shEIF3B RBE cells was partially attenuated after UC2288 (P21 signaling pathway inhibitor) treatment. Our findings underscored the potential of EIF3B as a therapeutic target for cholangiocarcinoma. Unraveling its functions holds promise for the development of more specific and effective targeted therapy strategies.

Phase II Study of Erdafitinib in Patients With Tumors With FGFR Amplifications: Results From the NCI-MATCH ECOG-ACRIN Trial (EAY131) Subprotocol K1

PURPOSE

Despite fibroblast growth factor receptor (FGFR) inhibitors being approved in tumor types with select FGFR rearrangements or gene mutations, amplifications of FGFR represent the most common FGFR alteration across malignancies. Subprotocol K1 (EAY131-K1) of the National Cancer Institute-MATCH platform trial was designed to evaluate the antitumor efficacy of the oral FGFR1-4 inhibitor, erdafitinib, in patients with tumors harboring FGFR1-4 amplification.

METHODS

EAY131-K1 was an open-label, single-arm, phase II study with central confirmation of presence of FGFR1-4 amplification in tumors. Patients with urothelial carcinoma were excluded. Enrolled patients received oral erdafitinib at a starting dose of 8 mg once daily continuously with escalation to 9 mg once daily continuously, on the basis of predefined time point assessments of phosphate levels, until disease progression or intolerable toxicity. The primary end point was centrally assessed objective response rate (ORR), with key secondary end points being 6-month progression-free survival (PFS6), PFS, overall survival (OS), and safety.

RESULTS

Thirty-five patients were enrolled into this study with 18 included in the prespecified primary efficacy analysis. The median age of the 18 patients was 60 years, and 78% had received ≥3 previous lines of therapy. There were no confirmed responses to erdafitinib; however, five patients experienced stable disease (SD) as best response. One patient with an FGFR1-amplified breast cancer had a prolonged PFS >168 days (5.5 months). The median PFS was 1.7 months (90% CI, 1.1 to 1.8 months) and the median OS was 4.2 months (90% CI, 2.3 to 9.3 months). The estimated PFS6 rate was 13.8% (90% CI, 3.3 to 31.6). The majority of toxicities were grade 1 to 2 in nature, although there was one grade 5 treatment-related adverse event.

CONCLUSION

Erdafitinib did not meet its primary end point of efficacy as determined by ORR in treatment-refractory solid tumors harboring FGFR1-4 amplifications. Our findings support that rearrangements and gene mutations, but not amplifications, of FGFR remain the established FGFR alterations with approved indications for FGFR inhibition.

Sunset Yellow protects against oxidative damage and exhibits chemoprevention in chemically induced skin cancer model

Skin cancer and other skin-related inflammatory pathologies are rising due to heightened exposure to environmental pollutants and carcinogens. In this context, natural products and repurposed compounds hold promise as novel therapeutic and preventive agents. Strengthening the skin's antioxidant defense mechanisms is pivotal in neutralizing reactive oxygen species (ROS) and mitigating oxidative stress. Sunset Yellow (SY) exhibits immunomodulatory characteristics, evidenced by its capacity to partially inhibit the secretion of proinflammatory cytokines, regulate immune cell populations, and modulate the activation of lymphocytes. This study aimed to investigate the antioxidant and anti-genotoxic properties of SY using in-silico, in vitro, and physiochemical test systems, and to further explore its potential role in 7,12-dimethylbenz(a) anthracene (DMBA)/ 12-o-tetradecanoylphorbol-13-acetate (TPA)-induced two-stage skin carcinogenesis. In vitro experiments showed that pre-treatment of SY significantly enhanced the cell viability of HaCaT cells when exposed to tertiary-Butyl Hydrogen Peroxide (tBHP). This increase was accompanied by reduced ROS levels, restoration of mitochondrial membrane potential, and notable reduction in DNA damage in (SY + tBHP) treated cells. Mechanistic investigations using DPPH chemical antioxidant activity test and potentiometric titrations confirmed SY's antioxidant properties, with a standard reduction potential (E o ) of 0.211 V. Remarkably, evaluating the effect of topical application of SY in DMBA/TPA-induced two-step skin carcinogenesis model revealed dose-dependent decreases in tumor latency, incidence, yield, and burden over 21-weeks. Furthermore, computational analysis and experimental validations identified GSK3β, KEAP1 and EGFR as putative molecular targets of SY. Collectively, our findings reveal that SY enhances cellular antioxidant defenses, exhibits anti-genotoxic effects, and functions as a promising chemopreventive agent.

A comprehensive overview of selective and novel fibroblast growth factor receptor inhibitors as a potential anticancer modality

The arrival of comprehensive genome sequencing has accelerated the understanding of genetically aberrant advanced cancers and target identification for possible cancer treatment. Fibroblast growth factor receptor (FGFR) gene alterations are frequent findings in various rare and advanced cancers refractive to mainstay chemo-therapy or surgical interventions. Several FGFR inhibitors have been developed for addressing these genetically altered FGFR-harboring malignancies, and some have performed well in clinical trials. In contrast, others are still being investigated in different phases of clinical trials. FDA has approved four anticancer agents such as erdafitinib, pemigatinib, infigratinib, and futibatinib, for clinical use in oncogenic FGFR-driven malignancies. These include cholangiocarcinoma, urothelial carcinoma, and myeloid/lymphoid malignancies. Pemigatinib is the only FGFR inhibitor globally approved (USA, EU, and Japan) and available as a targeted therapy for two types of cancer, including FGFR2 fusion or other rearrangements harboring cholangiocarcinoma and relapsed/refractory myeloid/lymphoid neoplasms with FGFR1 rearrangements. Myeloid/lymphoid neoplasm is the latest area of application added to the therapeutic armamentarium of FGFR inhibitors. Furthermore, futibatinib is the first-in-class covalent or irreversible pan-FGFR inhibitor that has received FDA approval for locally advanced or metastatic intrahepatic cholangiocarcinoma harboring FGFR2 gene aberrations. This review highlights the current clinical progress concerning the safety and efficacy of all the approved FGFR-TKIs (tyrosine kinase inhibitors) and their ongoing investigations in clinical trials for other oncogenic FGFR-driven malignancies.

Insight Into the Role of Alkaloids in the Different Signalling Pathways of Cholangiocarcinoma

Throughout the biliary tree, a variety of cells give rise to cholangiocarcinomas, a broad group of malignancies. The fact that these tumours are silent and asymptomatic, especially in their early stages, seriously impairs the effectiveness of available therapeutic options and contributes to their poor prognosis. Over the past few years, increased efforts have been made to identify the aetiology and signalling pathways of these tumours and to create more potent therapies. Since alkaloids are more potent and effective against cholangiocarcinoma cell lines, they have gained importance in the treatment of cholangiocarcinoma. In cell lines with cholangiocarcinoma, they promote apoptosis. and restrict the spread of cells, departure, and development. This review highlights the recent developments in the study of CCA, primarily concentrating on the regulation of the signalling pathway and revealing alkaloids demonstrating strong anti-cholangiocarcinoma efficacy, providing researchers with a rapid approach for the future development of powerful and efficient pharmaceutical compounds.

CP-673451, a Selective Platelet-Derived Growth Factor Receptor Tyrosine Kinase Inhibitor, Induces Apoptosis in Opisthorchis viverrini-Associated Cholangiocarcinoma via Nrf2 Suppression and Enhanced ROS

Platelet-derived growth factors (PDGFs) and PDGF receptors (PDGFRs) play essential roles in promoting cholangiocarcinoma (CCA) cell survival by mediating paracrine crosstalk between tumor and cancer-associated fibroblasts (CAFs), indicating the potential of PDGFR as a target for CCA treatment. Clinical trials evaluating PDGFR inhibitors for CCA treatment have shown limited efficacy. Furthermore, little is known about the role of PDGF/PDGFR expression and the mechanism underlying PDGFR inhibitors in CCA related to Opisthorchis viverrini (OV). Therefore, we examined the effect of PDGFR inhibitors in OV-related CCA cells and investigated the molecular mechanism involved. We found that the PDGF and PDGFR mRNAs were overexpressed in CCA tissues compared to resection margins. Notably, PDGFR-α showed high expression in CCA cells, while PDGFR-β was predominantly expressed in CAFs. The selective inhibitor CP-673451 induced CCA cell death by suppressing the PI3K/Akt/Nrf2 pathway, leading to a decreased expression of Nrf2-targeted antioxidant genes. Consequently, this led to an increase in ROS levels and the promotion of CCA apoptosis. CP-673451 is a promising PDGFR-targeted drug for CCA and supports the further clinical investigation of CP-673451 for CCA treatment, particularly in the context of OV-related cases.

Pharmacovigilance Study of Infigratinib: A Safety Analysis of the FDA Adverse Event Reporting System

BACKGROUND

Infigratinib is a fibroblast growth factor receptor (FGFR)-specifc tyrosine kinase inhibitor indicated for the treatment of patients with previously treated, unresectable, locally advanced or metastatic cholangiocarcinoma. However, few studies have been conducted to evaluated the safety of infigratinib in the real world. In this study, we conducted a pharmacovigilance study to evaluate the adverse events (AEs) of infigratinib by using the Food and Drug Administration Adverse Event Reporting System (FAERS) database.

METHODS

OpenVigil 2.1 was employed to extract the FAERS database. Descriptive analysis was used to describe the characteristics of infigratinib-associated AE reports. Disproportionality analysis was performed by calculating the proportional reporting ratio (PRR), reporting odds ratios (ROR), and Bayesian analysis confidence propagation neural network (BCPNN) to detect positive signals.

RESULTS

Our findings revealed 149 AE reports, among which 36 significant signals were identified. These significant AE signals were mainly observed in gastrointestinal disorders (N = 26, ROR = 26.03, PRR = 8.44, information component [IC] = 3.08) and skin and subcutaneous tissue disorders (N = 21, ROR = 92.13, PRR = 40.41, IC = 5.34). Notably, dehydration and skin exfoliation were unexpected AEs, but had relatively high signal intensities (ROR = 29.75, PRR = 26.64, IC = 4.74; ROR = 50.61, PRR = 45.24, IC = 5.50, respectively) despite not being listed on the drug label. Furthermore, our analysis showed that infigratinib dose differed statistically between severe and non-severe reports (113.82 ± 16.13 mg vs 125 ± 0.00 mg, t = - 4.28; p < 0.001). However, there were no significant differences in sex, age, and types of AEs between the two groups (p  = 0.06, p  = 0.86, and p = 0.93, respectively).

CONCLUSIONS

These findings suggest that gastrointestinal and skin toxicities are the most common adverse reactions for infigratinib. It is important to recognize skin exfoliation and dehydration in clinical practice, as they are unexpected AEs. Additionally, our study indicates that infigratinib dose may correlate with an increased risk of AE severity, highlighting the need for dose adjustment of infigratinib when exposure to the drug is increased due to internal or external factors.

FGFR blockade inhibits targeted therapy-tolerant persister in basal FGFR1- and FGF2-high cancers with driver oncogenes

Cancer cell resistance arises when tyrosine kinase inhibitor (TKI)-targeted therapies induce a drug-tolerant persister (DTP) state with growth via genetic aberrations, making DTP cells potential therapeutic targets. We screened an anti-cancer compound library and identified fibroblast growth factor receptor 1 (FGFR1) promoting alectinib-induced anaplastic lymphoma kinase (ALK) fusion-positive DTP cell's survival. FGFR1 signaling promoted DTP cell survival generated from basal FGFR1- and fibroblast growth factor 2 (FGF2)-high protein expressing cells, following alectinib treatment, which is blocked by FGFR inhibition. The hazard ratio for progression-free survival of ALK-TKIs increased in patients with ALK fusion-positive non-small cell lung cancer with FGFR1- and FGF2-high mRNA expression at baseline. The combination of FGFR and targeted TKIs enhanced cell growth inhibition and apoptosis induction in basal FGFR1- and FGF2-high protein expressing cells with ALK-rearranged and epidermal growth factor receptor (EGFR)-mutated NSCLC, human epidermal growth factor receptor 2 (HER2)-amplified breast cancer, or v-raf murine sarcoma viral oncogene homolog B1 (BRAF)-mutated melanoma by preventing compensatory extracellular signal-regulated kinase (ERK) reactivation. These results suggest that a targeted TKI-induced DTP state results from an oncogenic switch from activated oncogenic driver signaling to the FGFR1 pathway in basal FGFR1- and FGF2-high expressing cancers and initial dual blockade of FGFR and driver oncogenes based on FGFR1 and FGF2 expression levels at baseline is a potent treatment strategy to prevent acquired drug resistance to targeted TKIs through DTP cells regardless of types of driver oncogenes.

An Expert, Multidisciplinary Perspective on Best Practices in Biomarker Testing in Intrahepatic Cholangiocarcinoma

Intrahepatic cholangiocarcinoma (iCCA) is a rare and aggressive malignancy that arises from the intrahepatic biliary tree and is associated with a poor prognosis. Until recently, the treatment landscape of advanced/metastatic iCCA has been limited primarily to chemotherapy. In recent years, the advent of biomarker testing has identified actionable genetic alterations in 40%-50% of patients with iCCA, heralding an era of precision medicine for these patients. Biomarker testing using next-generation sequencing (NGS) has since become increasingly relevant in iCCA; however, several challenges and gaps in standard image-guided liver biopsy and processing have been identified. These include variability in tissue acquisition relating to the imaging modality used for biopsy guidance, the biopsy method used, number of passes, needle choice, specimen preparation methods, the desmoplastic nature of the tumor, as well as the lack of communication among the multidisciplinary team. Recognizing these challenges and the lack of evidence-based guidelines for biomarker testing in iCCA, a multidisciplinary team of experts including interventional oncologists, a gastroenterologist, medical oncologists, and pathologists suggest best practices for optimizing tissue collection and biomarker testing in iCCA.

Validated UPLC-MS/MS Method for Determination of Futibatinib and Its Pharmacokinetics in Beagle Dogs

Futibatinib, a highly selective, irreversible potent fibroblast growth factor receptor (FGFR) inhibitor, has been proved to be effective in clinical trials of intrahepatic cholangiocarcinoma (ICCA) patients. An ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method to determine the concentration of futibatinib in beagle dog plasma was developed and validated for the study of pharmacokinetics. After the plasma protein was removed by acetonitrile precipitation, futibatinib was detected and derazantinib was used as the internal standard (IS). Futibatinib and IS were separated in an UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm) with acetonitrile and 0.1% formic acid as the mobile phase, and the flow rate was 0.3 mL/min. Under the positive ion condition of an electrospray spray ion (ESI+) source, multireaction detection was used, and the ion pairs for futibatinib and IS were m/z 418.99 ⟶ 295.97 and 468.96 ⟶ 382.00, respectively. Futibatinib had a good linear relationship in the linear range of 0.5∼100 ng/mL; the lower limit of quantification (LLOQ) was 0.5 ng/mL. The RSDs of the intraday and interday precision were all less than 10.70%, and the RE value of accuracy was between −3.87% and 3.28%. The extraction recovery of futibatinib was more than 80%, and the matrix effect was around 100%, and futibatinib was found to be stable under four experimental conditions. The new optimized and validated UPLC-MS/MS method was an effective tool to determine the concentration of futibatinib in plasma and has been successfully applied to the pharmacokinetics of futibatinib in beagle dogs. This method would also be used to study drug-drug interaction (DDI).

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.

Updates in Biliary Tract Cancers

Biliary tract cancers (BTCs) are a heterogeneous group of malignancies arising from the epithelium of the biliary tree [...].

FDFT1/FGFR2 rearrangement: A newly identified anlotinib-sensitive FGFR2 variant in cholangiocarcinoma

According to previous reports,10-16% of patients with clinically advanced cholangiocarcinoma develop FGFR2 fusions or rearrangements. Treatment with FGFR2-specific inhibitors (tyrosine kinase inhibitors, TKIs) has proven effective for patients with cholangiocarcinoma. In this study, we report a case of advanced cholangiocarcinoma, in which the patient was unable to tolerate the adverse effects of standard first-line chemotherapy. Genetic testing suggested the presence of a novel variant resulting from FDFT1/FGFR2 rearrangement. Owing to poor accessibility and high price, only a limited number of patients with advanced cholangiocarcinoma have access to TKIs and precision targeted therapy in China. Anlotinib is a novel small-molecule multi-target TKI developed independently in China. It has a broad target spectrum, including FGFR, and can effectively inhibit tumor angiogenesis and tumor cell proliferation, thereby achieving an anti-tumor effect. Here, the patient was prescribed anlotinib. After treatment, the tumor size continued to shrink, and no significant adverse effects were reported. The finding suggested that anlotinib may be effective in patients with FDFT1/FGFR2 rearrangement and could serve as a novel treatment option for affected patients in future.

Advanced Bile Duct Cancers: A Focused Review on Current and Emerging Systemic Treatments

Cancers arising in the biliary tract are rare, with varied incidence depending on geographical location. As clinical presentation is typically vague with non-specific symptoms, a large proportion of patients present with unresectable or metastatic disease at diagnosis. When unresectable, the mainstay of treatment is cytotoxic chemotherapy; however, despite this, 5-year overall survival remains incredibly poor. Diagnostic molecular pathology, using next-generation sequencing, has identified a high prevalence of targetable alterations in bile duct cancers, which is transforming care. Substantial genomic heterogeneity has been identified depending on both the anatomical location and etiology of disease, with certain alterations enriched for subtypes. In addition, immune checkpoint inhibitors with anti-PD-1/PD-L1 antibodies in combination with chemotherapy are now poised to become the standard first-line treatment option in this disease. Here, we describe the established role of cytotoxic chemotherapy, targeted precision treatments and immunotherapy in what is a rapidly evolving treatment paradigm for advanced biliary tract cancer.

Structure-based design of a dual-warhead covalent inhibitor of FGFR4

The fibroblast growth factor 19 (FGF19)/fibroblast growth factor receptor 4 (FGFR4) signaling pathways play critical roles in a variety of cancers, such as hepatocellular carcinoma (HCC). FGFR4 is recognized as a promising target to treat HCC. Currently, all FGFR covalent inhibitors target one of the two cysteines (Cys477 and Cys552). Here, we designed and synthesized a dual-warhead covalent FGFR4 inhibitor, CXF-009, targeting Cys477 and Cys552 of FGFR4. We report the cocrystal structure of FGFR4 with CXF-009, which exhibits a dual-warhead covalent binding mode. CXF-009 exhibited stronger selectivity for FGFR4 than FGFR1-3 and other kinases. CXF-009 can also potently inhibit the single cystine mutants, FGFR4(C477A) and FGFR4(C552A), of FGFR4. In summary, our study provides a dual-warhead covalent FGFR4 inhibitor that can covalently target two cysteines of FGFR4. CXF-009, to our knowledge, is the first reported inhibitor that forms dual-warhead covalent bonds with two cysteine residues in FGFR4. CXF-009 also has the potential to overcome drug induced resistant FGFR4 mutations and might serve as a lead compound for future anticancer drug discovery.

FGFR2::TACC2 fusion as a novel KIT-independent mechanism of targeted therapy failure in a multidrug-resistant gastrointestinal stromal tumor

Genetic alterations in FGF/FGFR pathway are infrequent in gastrointestinal stromal tumors (GIST), with rare cases of quadruple wildtype GISTs harboring FGFR1 gene fusions and mutations. Additionally, FGF/FGFR overexpression was shown to promote drug resistance to kinase inhibitors in GISTs. However, FGFR gene fusions have not been directly implicated as a mechanism of drug resistance in GISTs. Herein, we report a patient presenting with a primary small bowel spindle cell GIST and concurrent peritoneal and liver metastases displaying an imatinib-sensitive KIT exon 11 in-frame deletion. After an initial 9-month benefit to imatinib, the patient experienced intraabdominal peritoneal recurrence owing to secondary KIT exon 13 missense mutation and FGFR4 amplification. Despite several additional rounds of tyrosine kinase inhibitors (TKI), the patient's disease progressed after 2 years and presented with multiple peritoneal and liver metastases, including one pericolonic mass harboring secondary KIT exon 18 missense mutation, and a concurrent transverse colonic mass with a FGFR2::TACC2 fusion and AKT2 amplification. All tumors, including primary and recurrent masses, harbored an MGA c.7272 T > G (p.Y2424*) nonsense mutation and CDKN2A/CDKN2B/MTAP deletions. The transcolonic mass showed elevated mitotic count (18/10 HPF), as well as significant decrease in CD117 and DOG1 expression, in contrast to all the other resistant nodules that displayed diffuse and strong CD117 and DOG1 immunostaining. The FGFR2::TACC2 fusion resulted from a 742 kb intrachromosomal inversion at the chr10q26.3 locus, leading to a fusion between exons 1-17 of FGFR2 and exons 7-17 TACC2, which preserves the extracellular and protein tyrosine kinase domains of FGFR2. We present the first report of a multi-drug resistant GIST patient who developed an FGFR2 gene fusion as a secondary genetic event to the selective pressure of various TKIs. This case also highlights the heterogeneous escape mechanisms to targeted therapy across various tumor nodules, spanning from both KIT-dependent and KIT-independent off-target activation pathways.

Optimizing the Diagnosis and Biomarker Testing for Patients with Intrahepatic Cholangiocarcinoma: A Multidisciplinary Approach

Cholangiocarcinoma (CCA) is a heterogenous group of malignancies originating in the biliary tree, and associated with poor prognosis. Until recently, treatment options have been limited to surgical resection, liver-directed therapies, and chemotherapy. Identification of actionable genomic alterations with biomarker testing has revolutionized the treatment paradigm for these patients. However, several challenges exist to the seamless adoption of precision medicine in patients with CCA, relating to a lack of awareness of the importance of biomarker testing, hurdles in tissue acquisition, and ineffective collaboration among the multidisciplinary team (MDT). To identify gaps in standard practices and define best practices, multidisciplinary hepatobiliary teams from the University of California (UC) Davis and UC Irvine were convened; discussions of the meeting, including optimal approaches to tissue acquisition for diagnosis and biomarker testing, communication among academic and community healthcare teams, and physician education regarding biomarker testing, are summarized in this review.