Selective FGFR Research Articles

Infigratinib in upper tract urothelial carcinoma vs urothelial carcinoma of the bladder and association with comprehensive genomic profiling/cell-free DNA results.

4510 Background: Infigratinib (BGJ398) is a potent and selective FGFR1–3 inhibitor with significant activity in patients (pts) with advanced or metastatic urothelial carcinoma (mUC) bearing FGFR3 alterations [Pal et al 2018]. Given the distinct biologic characteristics of upper tract UC (UTUC) and urothelial carcinoma of the bladder (UCB), we sought to determine if infigratinib had varying activity in these settings. Methods: Eligible pts had mUC with activating FGFR3 mutations/fusions and prior platinum-based chemotherapy, unless contraindicated. Pts received infigratinib 125 mg orally daily (3 wks on/1 wk off). Overall response rate (ORR: CR+PR) and disease control rate (DCR; CR+PR+SD) were characterized in UCB and UTUC pts. Comprehensive genomic profiling was performed on FFPE tissues in a CLIA-certified lab (Foundation Medicine; Cambridge, MA). Blood was collected for cell-free (cf)DNA analysis using a 600-gene panel on an Illumina HiSeq 2500 sequencer. Results: 67 pts were enrolled; the majority (70.1%) had received ≥2 prior antineoplastic therapies. ORR was 25.4% and DCR was 64.2%. In the 8 pts with UTUC, 1 CR and 3 PRs were observed (ORR 50%); the remainder had a best response of SD (DCR 100%). UTUC pts were predominantly 2nd line (62.5%), with only 2 (25%) showing response to previous treatment. In pts with UCB, 13 PRs were observed (ORR 22%), and 22 pts had a best response of SD (DCR 59.3%). Notable differences in genomic alterations between cohorts included a higher frequency of FGFR3-TACC3 fusions (12.5% vs 5.8%) and FGFR3 R248C mutations (50% vs 11.5%), and a lower frequency of FGFR3 S249C mutations (25% vs 59.6%) in UTUC vs UCB. Consistent with previous reports [Sfakianos et al 2016], UTUC pts had a differential frequency of alterations in HRAS, CDKN2B and ARID1A. Sufficient cfDNA yield was obtained in UTUC and UCB pts and a comprehensive comparison of these data will be presented. Conclusions: Differences in cumulative genomic profile were observed between UCB and UTUC in this FGFR3-restricted experience, underscoring the distinct biology of these diseases. Results with infigratinib in UTUC support a planned phase III adjuvant study predominantly in this population. Clinical trial information: NCT01004224.

A phase I study of H3B-6527 in hepatocellular carcinoma (HCC) or intrahepatic cholangiocarcinoma (ICC) patients (pts).

4095 Background: FGF19 overexpression is hypothesized to hyperactivate FGFR4 and its downstream signaling pathway leading to enhanced tumor growth in HCC/ICC. Targeting FGFR4 may have therapeutic benefit in HCC/ICC with altered FGF19 signaling. A phase 1 study (NCT02834780) was initiated to assess H3B-6527, an investigational highly selective covalent FGFR4 inhibitor. Methods: Adult pts with advanced HCC or ICC, ECOG PS 0-1, well compensated liver function, and who progressed after at least one prior therapy, were administered H3B-6527 orally QD (once daily) on a 21-day cycle following a 3+3 design. Patients in the dose escalation phase were treated regardless of FGF19 status. Adverse events (AEs), pharmacokinetics (PK), and pharmacodynamics (PD) were assessed. Response was determined by RECIST 1.1 or modified RECIST every 6 weeks. Results: As of 06-Jan-2019, 37 pts have been treated with H3B-6527 at doses of 300 to 1400 mg QD (23 pts in escalation; 14 in expansion). In dose escalation, a total of 17 patients with HCC, Child-Pugh A received prior systemic therapy including 100% with prior TKI and 35% with prior IO. 12% had hepatitis B virus and 47% had hepatitis C virus. H3B-6527 plasma levels increased with dose from 300 to 1000 mg QD and plateaued. H3B-6527 was rapidly absorbed with a tmax of ~2-3 h and showed a terminal half-life of ~4-5 h, following administration of 1000 mg (fasted). No dose-limiting toxicities or ≥ Grade 3 treatment-related AEs (TRAE) have been observed in escalation. Most common TRAEs (≥ 10%) were diarrhea, nausea, and vomiting. Based on safety, PK, and PD, 1000 mg QD was the recommended phase 2 dose. Durable stable disease and partial responses (PR) have been observed on the once daily fasted schedule; 2 of 17 pts with HCC achieved PRs and an additional 7 with stable disease were on treatment for ≥ 5 months. Conclusions: H3B-6527 is well tolerated and demonstrates early signs of clinical activity. Dose expansion on QD schedule and exploration of BID (twice daily) schedule is ongoing. Clinical trial information: NCT02834780.

Baseline cfDNA characteristics and evolution of cfDNA profile during treatment with selective FGFR inhibitor TAS-120.

3056 Background: There is an increasing role for cfDNA in monitoring response and mechanisms of resistance. We performed cfDNA analysis in a subset of patients enrolled on a Phase I trial with an irreversible, selective FGFR1-4 inhibitor, TAS-120. Methods: 58 plasma samples from 17 patients (13 with cholangiocarcinoma) were analyzed on a 73-gene, next-generation sequencing panel. Selected patients(pts) had longitudinal samples. Results: At least one alteration was detected in 46 cfDNA samples, in 16 (94%) of 17 pts – a pt with GBM had no alterations detected. 14 pts had alterations in FGFR2/3 by genomic testing of archival tumor samples, comprising 20 total alterations (18 unique). 10 of 20 FGFR2/3 alterations were also detected by cfDNA testing: 4/5 SNVs, 1/2 amplifications, 5/13 fusions. Three pts had FGFR/FGF alterations not included (thus not detected) in the cfDNA panel: 2 with FGF ligand amplification, and one FGFR4 mutation. 6 pts (35%) had PR, 5 (29%) had SD and 6 (35%) PD as a best response to TAS-120. Four pts had prior FGFRi: 2 had a PR, 1 SD, and 1 PD on TAS-120. Baseline cfDNA mutations became undetectable during treatment in 4/6 pts with PR. 4 of 6 PD pts had other driver mutations at baseline including mutations in PIK3CA, KRAS, IDH1, BRCA2, or amplifications in PIK3CA, PDGFR. 9 pts with cfDNA available at progression after SD/PR: 3 had acquired FGFR2 mutations (one each of V564L, V564F, or N549K). Two also acquired alterations in other candidate resistance genes ( PTEN and MAP2K1). Another pt had low variant allele frequency (VAF) NRAS G12D and BRAF A694T pretreatment and had SD. At progression, cfDNA revealed an increase in NRAS VAF and mutations acquired in the MAPK pathway . One pt with prior FGFRi acquired FGFR2 V564I and V564K detected by cfDNA prior to initiation of TAS-120, and had a PR on TAS-120. There was a drop in FGFR2 V564I VAF with response that subsequently increased with progression. The patient also acquired a FGFR2 V564L mutation at progression. Conclusions: FGFR alterations can be detected by cfDNA. cfDNA may detect potential resistance mechanisms, including PI3K or MAPK pathway alterations and acquired FGFR2 mutations. Patients with gatekeeper mutations in cfDNA at baseline may still respond to TAS-120. Further study is needed to determine the impact of FGFR2 mutations and co-alterations on TAS-120 sensitivity.

Novel 7-formyl-naphthyridyl-ureas derivatives as potential selective FGFR4 inhibitors: Design, synthesis, and biological activity studies.

Total twenty-five 7-formyl-naphthyridyl-urea derivatives were designed, synthesized and evaluated for their inhibition of FGFR4 kinase and antitumor activity. The pharmacological data indicated that most of the tested compounds showed high selectivity towards FGFR4 kinase and could significantly inhibit FGFR4 and the tumor cells lines with the high expression of FGFR4. In particular, compounds 6f, 6g, 6h, 6l, 6m and 6s showed a good performance in pharmacokinetic tests. When tested in mice, the representative compound 6f was found to have good pharmacokinetic parameters, low toxicity, and better tumor inhibiting activity in vivo.

Expanding the Arsenal of FGFR Inhibitors: A Novel Chloroacetamide Derivative as a New Irreversible Agent With Anti-proliferative Activity Against FGFR1-Amplified Lung Cancer Cell Lines.

Fibroblast Growth Factor Receptors (FGFR1–4) have a critical role in the progression of several human cancers, including Squamous Non-Small-Cell Lung Cancer (SQCLC). Both non-selective and selective reversible FGFR inhibitors are under clinical investigation for the treatment of patients with tumors harboring FGFR alterations. Despite their potential efficacy, the clinical development of these drugs has encountered several challenges, including toxicity, and the appearance of drug resistance. Recent efforts have been directed at development of irreversible FGFR inhibitors, which have the potential to exert superior anti-proliferative activity in tumors carrying FGFR alterations. With this in mind, we synthetized, and investigated a set of novel inhibitors possessing a warhead potentially able to covalently bind a cysteine in the P-loop of FGFR. Among them, the chloroacetamide UPR1376 resulted able to irreversible inhibit FGFR1 phosphorylation in FGFR1 over-expressing cells generated from SQCLC SKMES-1 cells. In addition, this compound inhibited cell proliferation in FGFR1-amplified H1581 cells with a potency higher than the reversible inhibitor BGJ398 (infigratinib), while sparing FGFR1 low-expressing cells. The anti-proliferative effects of UPR1376 were demonstrated in both 2D and 3D systems and were associated with the inhibition of MAPK and AKT/mTOR signaling pathways. UPR1376 inhibited cell proliferation also in two BGJ398-resistant cell clones generated from H1581 by chronic exposure to BGJ398, although at concentrations higher than those effective in the parental cells, likely due to the persistent activation of the MAPK pathway associated to NRAS amplification. Combined blockade of FGFR1 and MAPK signaling, by UPR1376 and trametinib respectively, significantly enhanced the efficacy of UPR1376, providing a means of circumventing resistance to FGFR1 inhibition. Our findings suggest that the insertion of a chloroacetamide warhead on a suitable scaffold, as exemplified by UPR1376, is a valuable strategy to develop a novel generation of FGFR inhibitors for the treatment of SQCLC patients with FGFR alterations.

AB014. S3A-3. Precision medicine on the horizon for cholangiocarcinoma

: Cholangiocarcinoma (CCA) is a molecularly heterogenous group of tumors, and tumor genotyping efforts have uncovered multiple actionable targets in both intrahepatic and extrahepatic tumors. IDH1 mutations, FGFR2 fusions, and BRAF V600E mutations are among the most promising targets to date in CCA-specific clinical trials and cohorts, and multiple agents targeting these gene alterations are in development. For patients with IDH1 mutant advanced refractory CCA, a phase III trial of the IDH1 inhibitor AG120 versus placebo recently completed accrual, and the results are anticipated. In FGFR2 fusion positive disease, multiple phase II and III efforts are underway to evaluate the efficacy of selective oral FGFR small molecular inhibitors. In patients with BRAF V600E mutant CCA, the combination of dabrafenib and trametinib has shown promise in a basket trial with a CCA cohort. Additional agents are also under investigation to in patients with alterations in HER2, PIK3CA, MET, and CDKN2A and also in patients with mutations in DNA damage repair pathway or chromatin remodeling genes.

Quantification of FGFR4 inhibitor BLU-554 in mouse plasma and tissue homogenates using liquid chromatography-tandem mass spectrometry

BLU-554 is a potent, highly selective oral FGFR4 inhibitor. A bioanalytical assay for quantification of BLU-554 in mouse plasma and six tissue homogenates (brain, kidney, liver, lung, small intestine, and spleen) was developed and validated using liquid chromatography with tandem mass spectrometric detection and with erlotinib as internal standard. After protein precipitation with acetonitrile in a 96-well format and separation on an XBridge® Peptide BEH C18 column by gradient elution using 0.2% (v/v) ammonium hydroxide (in water) and methanol, analytes were ionized by positive electrospray and monitored in the selected reaction monitoring mode by triple quadrupole mass spectrometry. The assay was validated in a 1–1000 ng/ml concentration range using calibration in mouse plasma. Precisions (intra–day and inter–day) were in the range 2.8–10.1% and accuracies were in between 88.5 and 96.6% for all levels in all matrices. The assay was successfully applied for a pilot pharmacokinetic and tissue distribution study in wild-type mice.

ODM-203, a Selective Inhibitor of FGFR and VEGFR, Shows Strong Antitumor Activity, and Induces Antitumor Immunity.

Alterations in the gene encoding for the FGFR and upregulation of the VEGFR are found often in cancer, which correlate with disease progression and unfavorable survival. In addition, FGFR and VEGFR signaling synergistically promote tumor angiogenesis, and activation of FGFR signaling has been described as functional compensatory angiogenic signal following development of resistance to VEGFR inhibition. Several selective small-molecule FGFR kinase inhibitors are currently in clinical development. ODM-203 is a novel, selective, and equipotent inhibitor of the FGFR and VEGFR families. In this report we show that ODM-203 inhibits FGFR and VEGFR family kinases selectively and with equal potency in the low nanomolar range (IC50 6-35 nmol/L) in biochemical assays. In cellular assays, ODM-203 inhibits VEGFR-induced tube formation (IC50 33 nmol/L) with similar potency as it inhibits proliferation in FGFR-dependent cell lines (IC50 50-150 nmol/L). In vivo, ODM-203 shows strong antitumor activity in both FGFR-dependent xenograft models and in an angiogenic xenograft model at similar well-tolerated doses. In addition, ODM-203 inhibits metastatic tumor growth in a highly angiogenesis-dependent kidney capsule syngenic model. Interestingly, potent antitumor activity in the subcutaneous syngenic model correlated well with immune modulation in the tumor microenvironment as indicated by marked decrease in the expression of immune check points PD-1 and PD-L1 on CD8 T cells and NK cells, and increased activation of CD8 T cells. In summary, ODM-203 shows equipotent activity for both FGFR and VEGFR kinase families and antitumor activity in both FGFR and angigogenesis models.

A successful collaboration between academia, biotech and pharma led to discovery of erdafitinib, a selective FGFR inhibitor recently approved by the FDA

The winners of the Malcolm Campbell Memorial Prize for 2019 discuss the discovery of erdafitinib.

Targeting of FGF-Signaling Re-Sensitizes Gastrointestinal Stromal Tumors (GIST) to Imatinib In Vitro and In Vivo.

Dysregulation of the fibroblast growth factor (FGF)/fibroblast growth factor receptor (FGFR) signaling pathway is frequently observed in multiple human malignancies, and thus, therapeutic strategies targeting FGFs and FGFRs in human cancer are being extensively explored. We observed the activation of the FGF/FGFR-signaling pathway in imatinib (IM)-resistant gastrointestinal stromal tumor (GIST) cells. Furthermore, we found that the activation of FGFR signaling has a significant impact on IM resistance in GISTs in vitro. Next, we tested the efficacy of BGJ398, a potent and selective FGFR1–3 inhibitor, in xenograft models of GISTs exhibiting secondary IM resistance due to receptor-tyrosine kinase (RTK) switch (loss of c-KIT/gain of FGFR2a). Five to eight-week-old female nu/nu mice were subcutaneously inoculated into the flank areas with GIST T-1R cells. Mice were randomized as control (untreated), IM, BGJ398, or a combination and treated orally for 12 days. IM had a moderate effect on tumor size, thus revealing GIST resistance to IM. Similarly, a minor regression in tumor size was observed in BGJ398-treated mice. Strikingly, a 90% decrease in tumor size was observed in mice treated with a combination of IM and BGJ398. Treatment with BGJ398 and IM also induced major histopathologic changes according to a previously defined histopathologic response score and resulted in massive myxoid degeneration. This was associated with increased intratumoral apoptosis as detected by immunohistochemical staining for cleaved caspase-3 on day 5 of the treatment. Furthermore, treatment with BGJ398 and IM significantly reduced the proliferative activity of tumor cells as measured by positivity for Ki-67 staining. In conclusion, inhibition of FGFR signaling substantially inhibited the growth of IM-resistant GISTs in vitro and showed potent antitumor activity in an IM-resistant GIST model via the inhibition of proliferation, tumor growth, and the induction of apoptosis, thereby suggesting that patients with advanced and metastatic GISTs exhibiting IM resistance might benefit from therapeutic inhibition of FGFR signaling.

Acquired JHDM1D-BRAF Fusion Confers Resistance to FGFR Inhibition in FGFR2-Amplified Gastric Cancer.

FGFR2 gene is frequently amplified in gastric cancer. Recently, targeting FGFR2 has drawn attention as a form of gastric cancer therapy, and FGFR-selective inhibitors have shown promising efficacy in clinical studies. Because overcoming acquired resistance is a common problem with molecular targeting drugs, we investigated a resistant mechanism of FGFR inhibitors using the gastric cancer cell line SNU-16, which harbors FGFR2 amplification. We established single-cell clones of FGFR inhibitor-resistant SNU-16 (AZD-R) by continuous exposure to AZD4547, a selective FGFR inhibitor. To screen the genetic alterations acquired in AZD-R, we ran a comparative genomic hybridization assay and found an amplification of Chr7q34 region. The chromosomal breakpoints were located between the 12th and the 13th exon of jumonji C domain containing histone demethylase 1 homolog D (JHDM1D) and between the 3rd and the 4th exon of BRAF We sequenced cDNA of the AZD-R clones and found fusion kinase JHDM1D-BRAF, which has previously been identified in primary ovarian cancer. Because JHDM1D-BRAF fusion lacks a RAS-binding domain, the dimerization of JHDM1D-BRAF was enhanced. A cell growth inhibition assay using MEK inhibitors and RAF-dimer inhibitors indicated the dependence of AZD-R clones for growth on the MAPK pathway. Our data provide a clinical rationale for using a MEK or RAF dimer inhibitor to treat FGFR2-amplified gastric cancer patients who have acquired resistance through the JHDN1D-BRAF fusion. Mol Cancer Ther; 17(10); 2217-25. ©2018 AACR.

Preselection of Lung Cancer Cases Using FGFR1 mRNA and Gene Copy Number for Treatment With Ponatinib

IntroductionPreclinically, high epidermal growth factor receptor 1 (FGFR1) messenger RNA (FGFR1-MRNA) and FGFR1 amplification (FGFR1-AMP) predicted sensitivity to fibroblast growth factor receptor inhibitors in non–small-cell lung cancer and small-cell lung cancer cell lines. KRAS mutations did not preclude sensitivity. Patients and MethodsMetastatic EGFR- and ALK-negative lung cancers were screened for FGFR1-MRNA by in-situ hybridization (ISH) and FGFR1-AMP by silver in-situ hybridization (SISH). Patients with positive findings were offered ponatinib, a multi–kinase inhibitor of FGFR1-4. Differences in overall survival (OS) between cohorts were assessed by the log-rank test. Association of FGFR1 positivity with clinicopathologic features were assessed by Fisher exact test and Kruskal-Wallis rank sum test. ResultsA total of 171 cases were prescreened: 9 (7.3%) of 123 SISH+; 53 (42.1%) of 126 ISH+; and 6 cases concordantly positive for SISH and ISH. SISH+ cases had fewer coincident KRAS mutations (P = .03) than SISH− cases, and ISH+ cases had worse OS (P = .020) than ISH− cases. Data distributions suggested a distinct higher positivity cut point for FGFR1 ISH (≥ 20%), occurring in 29 (23%) of 126 cases, was associated with small-cell lung cancer histology (P = .022), soft tissue metastases (P = .050) and shorter OS (P = .031). Four patients received ponatinib on study: All ISH+ by the initial cut point, 2 of 4 by higher cut point, 1 of 4 SISH+. Tolerability was poor. The best response for the 2 higher ISH cases was stable disease and progressive disease for the 2 lower ISH cases. ConclusionElevated FGFR1-MRNA is more common than FGFR1-AMP and associated with worse OS. Higher FGFR1 mRNA expression may be associated with a specific phenotype and is worthy of further exploration. Ponatinib's poor tolerance suggests further fibroblast growth factor receptor exploration in ISH+ cases should utilize more selective FGFR1 inhibitors.

The therapeutic targeting of the FGFR1/Src/NF-κB signaling axis inhibits pancreatic ductal adenocarcinoma stemness and oncogenicity.

The aberrant activation of the FGFR signaling is detected in many solid tumors, including pancreatic ductal adenocarcinoma (PDAC), suggesting it as a potential therapeutic target. In this study, we investigated the antitumor and anti-metastasis efficacy of the selective FGFR1 inhibitor, PD173074 in PDAC. We used immunohistochemical and in situ hybridization analyses to demonstrate a strong correlation between FGFR1 amplification and/or expression and disease progression in PDAC patients. We showed that ALDHhigh (ALDH+) pancreatic cancer cells exhibited stem cell-like phenotype and expressed higher levels of FGFR1, Src, NF-κB, alongside stemness markers like Oct4 and Sox2, compared to their ALDHlow/null (ALDH-) counterparts, suggesting the preferential activation of the FGFR1/Src/NF-κB signaling axis in pancreatic cancer stem cells (panCSCs). Furthermore, treatment of the ALDHhigh/ FGFR1-rich pancreatic cancer cell lines with PD173074, a selective FGFR1 inhibitor, revealed that PD173074 inhibited the proliferation and self-renewal of the panCSCs, and induced their apoptosis by activating caspase-3 and cleaving Poly-ADP ribose Polymerase (PARP). The anti-CSCs effect of PD173074 was associated with decreased expression of Oct4, Sox-2, Nanog, and c-Myc, as well as suppression of XIAP, Bcl2, and survivin expression, dose-dependently. Additionally, activation of cMet, Src, ERK 1/2 and NFκB (p65) was also inhibited by PD173074. Also, of clinical relevance, the disruption of the FGFR1/Src/NF-κB signaling axis positively correlated with poor clinical prognosis among the PDAC patients. We concluded that PD173074 suppresses the tumorigenesis and CSCs-like phenotype of PDAC cells, highlighting its therapeutic efficacy and providing support for its potential use as a therapeutic option for the 'difficult-to-treat', 'quick-to-relapse' PDAC patients. Schematic abstract showing how PD173074 inhibits PDAC growth through selective targeting of FGFR1, suppression of cancer stemness, disruption of the FGFR1/Src/NF-κB signaling axis and activation of the cell death signaling pathway.

Synergistic anti-angiogenic treatment effects by dual FGFR1 and VEGFR1 inhibition in FGFR1-amplified breast cancer

FGFR1 amplification has been found in 15% of patients with breast cancer and has been postulated as a promising marker to predict response against FGFR inhibitors. However, early phase clinical trials of selective FGFR inhibitors demonstrated only limited efficacy in FGFR1-amplified breast cancer patients. We found that BGJ398, an FGFR inhibitor, effectively inhibited phosphorylation of FGFR1 and MEK/ERK signaling in FGFR1-amplified breast cancer without affecting tumor cell proliferation. However, FGFR1 knockout inhibited tumor angiogenesis in vivo. We unraveled that FGFR1 regulates the secretion of the proangiogenic vascular endothelial growth factor (VEGF) in a MAPK-dependent manner. We further found that FGF-FGFR1 signaling induces an autocrine activation of VEGF-VEGFR1 pathway that again amplifies VEGF secretion via VEGF-VEGFR1-AKT signaling. Targeting both VEGFR1 and FGFR1 resulted in synergistic anti-angiogenic treatment effects in vivo. We thus postulate synergistic treatment effects in FGFR1/VEGFR1-positive breast cancer patients by dual targeting of FGFR and VEGFR.

Abstract LB-272: Discovery and characterization of a novel FGFR4 Inhibitor for the treatment of hepatocellular carcinoma

Abstract Introduction: Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related deaths worldwide and has one of the fastest growing incidence among cancers. Aberrant FGF19-FGFR4 signaling occurs in 10-30% of HCC patients and drives tumor development and progression. Pan-FGFR inhibitors are associated with hyperphosphatemia in clinic due to inhibition of FGFR1. Therefore, selectively targeting FGFR4 may render a safer treatment approach with improved clinical benefits. Using advanced computation-aided structural analysis and medicinal chemistry design, we have discovered a novel and highly selective small molecular FGFR4 inhibitor, ABSK-011, demonstrating robust anti-tumor activity in hepatocellular carcinoma models. Method: ABSK-011 was evaluated in biochemical Caliper assay and Celltiter-Glo assay for its inhibition on FGFR4 enzymatic and cellular activities. Its selectivity against other FGFR family members was analyzed through related biochemical, cellular, and KinomeScan profiling assays. The pharmacokinetics (PK) profile of ABSK-011 was characterized across various species of animals including mouse, rat and dog. Efficacy studies were conducted in two HCC xenograft models, and preliminary toxicity profile was also evaluated. Results: ABSK-011 inhibits FGFR4 with IC50 < 10 nM in biochemical assay and exhibits at least 50 fold selectivity against other FGFR kinases. The strong selectivity arises from the ability of ABSK-011 to irreversibly modify Cys552, a residue within the active site of FGFR4 that is not conserved among other FGFR kinases. ABSK-011 also shows greater than 800-fold selectivity against other RTK members. In HCC cells with autocrine production of FGF19, ABSK-011 inhibits the auto-phosphorylation of FGFR4 and blocks signal transduction from FGFR4 to downstream pathway activation. HCC cell lines harboring amplification and overexpression of FGF19 are uniquely sensitive to growth inhibition by ABSK-011 (EC50 < 50 nM) compared with cancer cell lines with FGFR1 dependence (EC50 > 2000 nM), confirming selectivity for FGFR4 over FGFR1. In vivo PK study demonstrated high exposure and superior DMPK profile of ABSK-011 in mouse, rat and dog. In preclinical in vivo studies, oral administration of ABSK-011 strongly inhibits the growth and induces regressions of subcutaneous xenograft tumors dependent upon FGFR4 activity. Suppression of tumor growth is dose dependent and well correlated with pharmacodynamic inhibition of FGFR4 signaling. Safety studies showed that ABSK-011 has no inhibition on CYP family members, hERG, etc. Conclusion: ABSK-011, presented here by Abbisko Therapeutics, is a highly potent, selective, and oral-available small molecular FGFR4 inhibitor. Its superior profile supports fast-track preclinical development. Citation Format: Zhui Chen. Discovery and characterization of a novel FGFR4 Inhibitor for the treatment of hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-272.

Abstract 2589: Novel predictor of FGFR1 inhibition efficacy in non-small cell lung cancer

Abstract Fibroblast growth factor receptor (FGFR)1 has been associated with tumorigenesis in a variety of tumors, including lung cancer. FGFR1 amplification is detected in up to 20% of lung squamous cell carcinomas, and was initially related to tumorigenesis and to response to FGFR inhibitors in preclinical models of this pathology. These data encouraged the establishment of FGFR1 amplification as the main eligibility criterion for inclusion of patients in FGFR inhibitors clinical trials. However, the use of FGFR inhibitors in FGFR1-amplified tumors has shown limited success, with only 5-10% of selected patients showing partial response, suggesting that this genomic aberration may not be a good predictive biomarker for the efficacy of these inhibitors. In this work, we provide in vitro and in vivo data showing that the oncogenic effects of FGFR1 expression depend on the expression of the adhesion molecule N-cadherin in non-small cell lung cancer (NSCLC). In line with these results, FGFR1 expression correlates with poorer prognosis only in tumors with high N-cadherin levels in two independent NSCLC patient cohorts. We observed that high FGFR1 expression alone is not sufficient to predict FGFR inhibition efficacy in lung cancer cell lines and patient-derived xenografts, with only high FGFR1- and high N-cadherin-expressing models responding to selective FGFR inhibitors. Altogether, our data show that the determination of the expression of FGFR1 alone is not sufficient to predict FGFR inhibition efficacy. The co-determination of N-cadherin expression may optimize patient selection for this therapeutic strategy. Citation Format: Álvaro Quintanal-Villalonga, Irene Ferrer, Ángela Marrugal, Laura Ojeda-Márquez, Jon Zugazagoita, Laura García-Redondo, Fernando López-Ríos, Luis Montuenga, Sonia Molina-Pinelo, Sonia Molina-Pinelo, Amancio Carnero, Luis Paz-Ares. Novel predictor of FGFR1 inhibition efficacy in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2589.

Abstract 899: Phosphorylated mTOR by signaling through EphB3 confers resistance to a selective FGFR inhibitor in SNU-16 gastric cancer cells

Abstract Because about 10% of gastric cancers show amplification of FGFR2, inhibition of FGFR2 activation has been regarded as one of therapeutic targets. AZD4547, a selective inhibitor of the FGFR1-3 tyrosine kinases, was developed to inhibit FGFR signaling; however, its efficacy is limited by emergency of the acquired resistance. We tried to clarify a resistance mechanism against the FGFR inhibitor. The cell line resistant against AZD4547 was established using SNU-16 (SNU16R), an FGFR2-amplified gastric cancer cell line, by culturing with increasing concentration of AZD4547. The expression levels of FGFR or phosphorylated FGFR (pFGFR), EphB3 and downstream signaling molecules, proteins involved in epithelial-mesenchymal transition (EMT) and apoptosis, were determined by Western blot. Cell viability was measured with EZ-Cytox kit reagent (DoGen, Seoul, Korea). Relative level of tyrosine phosphorylation of receptor tyrosine kinases (RTKs) was evaluated with Proteome ProfilerTM array by human phosphor-RTK kit (R&D Systems). Apoptosis was determined by Annexin V-FITC apoptosis detection kit (BioBud, Seoul, Korea). Cell cycle assay was performed using Beckman Coulter flow cytometer and WinMDI for determination of cell numbers in G1, S, G2/M phases. Here we show the following: 1) establishment of a gastric cancer cell line (SNU16) resistant to AZD4547 (SNU16R); 2) expression of EphB3 receptor in SNU16R and induction of apoptosis and cell cycle arrest as well as inhibition of cell proliferation and suppressed expression of EMT markers under the treatment EphB3 inhibitor in SNU16R; 3) demonstration of mTOR as a downstream signaling cascade molecule of EphB3 by showing increased expression of phosphorylated (p-) mTOR and its downstream molecules in SNU16R and suppressed expression of p-mTOR by the EphB3 inhibitor. Cell cycle arrest, inhibition of cell proliferation and suppressed expression of p-mTOR under treatment with everolimus were also shown. We concluded that phosphorylation of mTOR through activation of EphB3 receptor is one of the mechanisms that confer resistance to AZD 4547, a selective FGFR inhibitor, in gastric cancer cells. Citation Format: Suk-young Lee, YooJin Na, YoonA Jung, JungLim Kim, Sang Cheul Oh, Dae-Hee Lee. Phosphorylated mTOR by signaling through EphB3 confers resistance to a selective FGFR inhibitor in SNU-16 gastric cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 899.

Abstract 4780: A novel, potent and selective FGFR4 inhibitor, HM81422 in hepatocellular carcinoma with FGFR4-driven pathway activation

Abstract Introduction: Hepatocellular carcinoma (HCC) is the sixth most prevalent cancer and the second most frequent cause of cancer-related death, however, treatment options are very limited. In recent studies, aberrant signaling through FGFR4 and its ligand, FGF19 have been identified as the oncogenic driver in a subset of HCCs and reported to be associated with poor prognosis. About 30% of HCC patients have altered FGF19/FGFR4 pathway signaling, therefore, the treatment with FGFR4 inhibitor may produce benefit. Materials and Method: Using the structure-based design, we have generated a novel, potent and selective FGFR4 inhibitor, HM81422 with irreversible-covalent binding mode, and evaluated its anti-tumor activity in a variety of HCC cell lines, HCC cell line xenografts and orthotopic grafts. Results: Biochemical selectivity assays demonstrated that HM81422 is highly selective towards FGFR4 compared to other FGFR isotypes as well as a panel of several kinases. The treatment of HM81422 to FGF19 amplified and overexpressed HCC cell lines led to suppression of FGF19/FGFR4 signaling pathway and concomitant reduction in cell viability in dose-dependent manner. Oral administration of HM81422 to mice bearing FGF19 altered HCC cells showed dose-dependent pharmacokinetics, pharmacodynamic modulation of FGFR4 signaling and antitumor efficacy in xenograft models. And HM81422 demonstrated inhibition of tumor growth in an orthotopic liver xenograft model of FGF19 altered HCC in nude mice. Conclusion: In conclusion, the treatment of HCC patients with a potent and selective FGFR4 inhibitor, HM81422, can be an attractive approach targeting approximately 30% of HCC patients by inhibiting altered FGF19-mediated signaling cascade. Further preclinical studies with HM81422 will be performed and reported soon. Citation Format: JaeHo Lee, Hyunjeong Kang, Kyounghwa Koo, Youngeun Ha, Sun Young Lim, Joo-Yun Byun, Hyunkyung Yu, Taehun Song, Moonsub Lee, Seung Hyun Jung, Taewoo Kim, Hyojeong Bang, Eunyoung Kim, Jahoon Kang, Ho Jeong Lee, YoungHoon Kim, YoungGil Ahn, KweeHyun Suh, Sun-Jin Kim. A novel, potent and selective FGFR4 inhibitor, HM81422 in hepatocellular carcinoma with FGFR4-driven pathway activation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4780.

Bile Acid Sequestration by Cholestyramine Mitigates FGFR4 Inhibition-Induced ALT Elevation.

The FGF19- fibroblast growth factor receptor (FGFR4)-βKlotho (KLB) pathway plays an important role in the regulation of bile acid (BA) homeostasis. Aberrant activation of this pathway has been described in the development and progression of a subset of liver cancers including hepatocellular carcinoma, establishing FGFR4 as an attractive therapeutic target for such solid tumors. FGF401 is a highly selective FGFR4 kinase inhibitor being developed for hepatocellular carcinoma, currently in phase I/II clinical studies. In preclinical studies in mice and dogs, oral administration of FGF401 led to induction of Cyp7a1, elevation of its peripheral marker 7alpha-hydroxy-4-cholesten-3-one, increased BA pool size, decreased serum cholesterol and diarrhea in dogs. FGF401 was also associated with increases of serum aminotransferases, primarily alanine aminotransferase (ALT), in the absence of any observable adverse histopathological findings in the liver, or in any other organs. We hypothesized that the increase in ALT could be secondary to increased BAs and conducted an investigative study in dogs with FGF401 and coadministration of the BA sequestrant cholestyramine (CHO). CHO prevented and reversed FGF401-related increases in ALT in dogs in parallel to its ability to reduce BAs in the circulation. Correlation analysis showed that FGF401-mediated increases in ALT strongly correlated with increases in taurolithocholic acid and taurodeoxycholic acid, the major secondary BAs in dog plasma, indicating a mechanistic link between ALT elevation and changes in BA pool hydrophobicity. Thus, CHO may offer the potential to mitigate elevations in serum aminotransferases in human subjects that are caused by targeted FGFR4 inhibition and elevated intracellular BA levels.

Safety and efficacy of the selective FGFR inhibitor debio 1347 in phase I study patients with FGFR genomically activated advanced biliary tract cancer (BTC).

447 Background: BTC are aggressive tumors with limited treatment options and poor overall survival. Aberrant FGFR signaling has been implicated in BTC carcinogenesis. Debio 1347 is an orally available selective FGFRi with potent antitumor effect in preclinical model bearing FGFR alterations. Debio 1347 showed encouraging preliminary clinical activity and manageable treatment-emergent adverse events (TEAE) in its first-in-human (FIH) ph1 study (NCT1948297) dose-escalating part. Here we report only results from the BTC pts of this study. Methods: This FIH study enrolled pts with advanced solid malignancies harboring defined activating alterations of FGFR 1, 2, or 3: amplifications (amp), mutations (mut) and translocations (trans). Pharmacokinetics (PK) and pharmacodynamics were serially evaluated in blood, skin and/or tumor tissue. A confirmatory post-hoc analysis was performed centrally for all available biopsies. Results: Eight pts, six with intrahepatic cholangiocarcinoma (iCCA) and two with gallbladder cancer (GBC), were treated with Debio 1347 at doses between 60 and 150 mg orally daily in 28-day cycles. Among the iCCA pts, one had an FGFR2mut, one had an FGFR2 activating deletion (del), and one had an FGFR3mut; the other three had FGFR2trans. One of the two GBC pts had an FGFR3trans, the other one an FGFR2mut. All pts had prior systemic therapy (mostly 2 or 3 lines). The most common TEAEs were hyperphosphatemia (8/8), nail changes (5/8), nausea (5/8), dry mouth (4/8) and stomatitis (3/8). No grade ≥ 3 related TEAE were reported except grade 3 hyperphosphatemia (4/8). PK was comparable to that in pts with other solid malignancies.A partial response lasting up to 48 weeks was observed in an iCCA pt (FGFR2 del exon 5); three additional iCCA pts (FGFR2trans: ROCK1; KIAA1217; DDX21) and one GBC pt (FGFR3-TACC3 trans) had target lesions regression < 30% and stayed on trial between 24 – 37 weeks. Overall disease control was 62.5%. Conclusions: These results suggest that BTC pts with genomic events leading to activation of FGFR2/3 may benefit from treatment with Debio 1347. Further study is ongoing in the expansion cohort of this trial. Clinical trial information: NCT1948297.