FGFR Tyrosine Kinase Inhibitor Research Articles

7434 Modulation of FGFR-FGF2-FGF23 Signaling Partially Rescues Osteoarthritis in Hyp Mice Homolog of Human X- Linked Hypophosphatemia

Abstract Disclosure: M.M. Hurley: None. L. Xiao: None. Human with X-linked hypophosphatemia (XLH) and its Hyp mice homolog develop several phenotypic abnormalities due to phosphate wasting mediated by abnormal Fibroblast Growth Factor Receptor-1 (FGFR1) and Fibroblast Growth Factor 23 (FGF23) signaling. XLH and Hyp mice also develop severe osteoarthropathy (OA) whose etiology is not fully defined. We previously reported that Fibroblast growth factor 2 (FGF2) regulates FGF23, specifically, mice overexpressing the high molecular weight FGF2 isoforms (HMWFGF2) in osteoprogenitors phenocopy Hyp mice including development of OA that worsens with age. Since we also reported that Hyp mice overexpress HMWFGF2 isoforms in osteoblasts and osteocytes, we examined whether the knee OA phenotype in Hyp mice was associated with aberrant FGFR1, FGF2, FGF23 signaling in knee joint articular cartilage and subchondral bone and whether in vivo FGFR tyrosine kinase inhibitor BGJ398 would modulate the OA phenotype in knee joints of Hyp mice. Ten weeks-old Control and Hyp mice were treated with Vehicle or BGJ398 for 12 weeks. Safranin-O staining of knee articular cartilage for proteoglycan revealed decreased staining in Hyp vehicle-treated mice that was partially restored to the cartilage thickness of Control mice in the Hyp-BGJ398-treated group. Significantly increased degradative enzyme matrix metalloproteinase-13 (MMP-13) in Hyp vehicle-treated knee articular cartilage was significantly reduced by BGJ398. Immunostaining revealed significantly increased phosphorylated FGFR1, FGF2 and FGF23 in both articular cartilage and subchondral bone. While BGJ398 significantly reduced immunostaining for phosphoFGFR1 and FGF2 in both articular cartilage and subchondral bone, it significantly reduced FGF23 in subchondral bone but not in articular cartilage. Significantly increased phospho-ERK1/2 labeling in Hyp-vehicle treated articular cartilage was partially rescued by BGJ398. This study demonstrates that increased FGFR1/FGF2 signaling contributes to OA in Hyp mice that can be partially rescued by FGF receptor inhibitor via reduction in MAPK signaling. Presentation: 6/1/2024

LGG-19. SLIPPED CAPITAL FEMORAL EPIPHYSIS (SCFE): A RARE ADVERSE EVENT ASSOCIATED WITH FGFR TYROSINE KINASE INHIBITOR THERAPY IN A CHILD

Abstract BACKGROUND FGFR tyrosine kinase inhibitors (FGFR-TKIs) are being increasingly used off-label in children with hard-to-treat tumors harboring specific FGFR alterations. We report a case of Slipped Capital Femoral Epiphysis (SCFE), an on target skeletal toxicity of a pan-FGFR TKI inhibitor, erdafitinib. METHODS Data was extracted from chart review of the patient and literature search for the use of FGFR-TKIs in children and their side effects. RESULTS A 13-year-old boy was diagnosed to have a optic pathway/ hypothalamic glioma with signs of increased intracranial pressure and obstructive hydrocephalus requiring placement of ventriculo-peritoneal (VP) shunt. Sequencing of the tumor showed FGFR1-Tyrosine kinase domain internal tandem duplication (FGFR1-KD-ITD) and was negative for BRAF mutation/ fusion. Two weeks later, he was treated for a VP shunt infection (surgical revision and 6 weeks antibiotics). He developed hypothalamic obesity with rapid weight gain and BMI >30. After a four-month delay from the initial diagnosis, he was started on erdafitinib a pan-FGFR1-4 inhibitor, through a special access program. At 12 weeks of treatment, he developed persistent knee pain. X-ray of the hips showed slipped capital femoral epiphysis (SCFE) of the right hip. Erdafitinib was discontinued and he underwent surgery with in-situ pinning of the right hip and prophylactic pinning of the left hip. MRI at the time of stopping the medication showed a 30% decrease in the size of the tumor, which has remained stable at 6 months follow up. CONCLUSIONS Based on our experience and literature review of pediatric patients who are treated with pan-FGFR TKIs, we recommend: a) monitoring both rate of weight gain/ BMI for obesity and growth velocity while on therapy and b) update the drug toxicity profile of FGFR TKIs to include skeletal toxicities and inform parents/ patients of these toxicities at the time of consent for therapy.

Case report: Slipped capital femoral epiphysis: a rare adverse event associated with FGFR tyrosine kinase inhibitor therapy in a child

We report a case of slipped capital femoral epiphysis (SCFE), an on target skeletal toxicity of a pan-FGFR TKI inhibitor, erdafitinib. A 13-year-old boy was diagnosed to have an optic pathway/hypothalamic glioma with signs of increased intracranial pressure and obstructive hydrocephalus requiring placement of ventriculo-peritoneal (VP) shunt. Sequencing of the tumor showed FGFR1-tyrosine kinase domain internal tandem duplication (FGFR1-KD-ITD). He developed hypothalamic obesity with rapid weight gain and BMI >30. At 12 weeks of treatment with erdafitinib, he developed persistent knee pain. X-ray of the right hip showed SCFE. Erdafitinib was discontinued, and he underwent surgical pinning of the right hip. MRI at discontinuation of erdafitinib showed a 30% decrease in the size of the tumor, which has remained stable at 6 months follow-up. Our experience and literature review suggest that pediatric patients who are treated with pan-FGFR TKIs should be regularly monitored for skeletal side effects.

Abstract PS17-09: An FGFR1/2 degrader overcomes antiestrogen resistance in ER+/FGFR1-amplified breast cancer

Abstract We previously reported that nuclear FGFR1 promotes antiestrogen resistance in ER+/FGFR1-amplified breast cancer. Nuclear FGFR1 activity was not affected by FGFR tyrosine kinase inhibitors (TKIs). Furthermore, pan-FGFR TKIs are not well tolerated. Therefore, new therapeutic strategies that inhibit nuclear FGFR1 while sparing FGFR3 and FGFR4 would be required to overcome antiestrogen resistance and limit toxicity. For this study, we used the proteolysis-targeting chimera (PROTAC) DGY-09-192, consisting of the FGFR TKI BCJ398 linked with a VHL recruiting ligand, to degrade FGFR1 and FGFR2. We aimed to determine whether selective degradation of FGFR1/2 overcomes endocrine resistance. Treatment with 50-100 nM DGY-09-192 strongly induced FGFR1 degradation and suppressed phosphorylation of FGFR1 and its downstream targets FRS2, AKT, and ERK1/2 in ER+/FGFR1-amplified CAMA1 and MDA-MB-134 breast cancer cells. FGFR1 degradation was evident within 4 h and lasted 48-96 h after drug washout. The proteasome inhibitor MG132 (10 µM) rescued both FGFR degradation and phosphorylation of downstream signaling molecules induced by DGY-09-192, confirming that FGFR1 degradation is dependent on ubiquitination and proteasomal degradation. At equivalent concentrations, DGY-09-192 suppressed phosphorylation of FGFR1 and its downstream targets more potently than BGJ398. Subcellular fractionation showed treatment with DGY-09-192 (100 nM) degraded FGFR1 in membrane, nuclear, and chromatin-bound fractions in both CAMA1 and MDA-MB-134 cells. Treatment of >CAMA1 cells with DGY-09-192 (>100 nM) downregulated nuclear FGFR1 target genes and canonical ERα target genes, such as CCND1, VEGFA, and CDK12 as measured by qRT-PCR whereas treatment with BGJ398 (100 nM) did not. Treatment with DGY-09-192 (500 nM) reversed resistance to the ER degrader fulvestrant in CAMA1 cells as measured by colony formation assays and using the Incucyte Live-Cell Analysis System. Each drug alone showed a modest effect on cell proliferation whereas the combination completed blocked cell growth (p < 0.0001). Finally, treatment of NOD scid gamma (NSG) mice with established ER+/FGFR1-amplified HCI-011 patient-derived xenografts with DGY-09-192 (40 mg/kg daily x2-6) induced FGFR1 degradation and blocked phosphorylation of downstream targets in the tumors. Studies using the combination of DGY-09-192 and fulvestrant in mice bearing established HCI-011 xenografts are in progress. We next investigated the effect of DGY-09-192 on cancer cells harboring FGFR1 and FGFR2 activating mutations. DGY-09-192 treatment induced FGFR2 degradation and blocked downstream signaling in MFE296 endometrial cancer and EFM-19 breast cancer cells that harbor the FGFR2N549K and FGFR2K659E hotspot mutations, respectively. In addition, DGY-09-192 strongly suppressed MFE296 cell proliferation. We are currently investigating whether DGY-09-192 blocks signaling and cell proliferation induced by the N546K and K656E hotspot FGFR1 mutations in ER+ breast cancer cells. Notably, a recent clinical study showed that tumors harboring these FGFR1 activating mutations are refractory to the pan-FGFR TKI pemigatinib. Conclusions: The FGFR1/2 PROTAC DGY-09-192 induced degradation of nuclear and membrane-bound FGFR1 and blocked FGFR1-induced signaling and nuclear activity in ER+/FGFR1-amplified breast cancer cells. The combination of DGY-09-192 and fulvestrant synergistically suppressed proliferation of these cells. Therefore, FGFR1 degradation represents a promising therapeutic strategy to block FGFR1 activity more completely and selectively in ER+ breast cancers harboring activating FGFR1 alterations. Citation Format: Yasuaki Uemoto, Chang-Ching Lin, Alberto Servetto, Bingnan Wang, Dan Ye, Fabiana Napolitano, Hima Milan Patel, Luigi Formisano, M Rosario Chica-Parrado, Emmanuel Bikorimana, Saurabh Mendiratta, Chuo Chen, Ariella Hanker, Carlos Arteaga. An FGFR1/2 degrader overcomes antiestrogen resistance in ER+/FGFR1-amplified breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS17-09.

Abstract B129: A bispecific antibody inhibits FGFR3 dimerization and is highly effective in FGFR3-driven tumor models

Abstract Background: The receptor tyrosine kinase (RTK) FGFR3 is frequently mutated in bladder cancer (~15-20% in muscle invasive bladder cancer, MIBC) and is a validated therapeutic target. Oncogenic alterations in FGFR3 include point mutations in the extracellular domain (S249C, R248C, G372C, Y375C) and gene fusions that place an oligomerization domain from a fusion partner at the FGFR3 C-terminus (e.g., FGFR3-TACC3). Although pan-FGFR tyrosine kinase inhibitors (TKI) have demonstrated clinical efficacy, toxicity and acquired resistance limit the benefit of these agents. While antibody-based therapy can offer superior selectivity compared to TKIs, conventional ligand-blocking antibodies are usually ineffective inhibitors of constitutively active RTKs. Further, the existence of multiple oncogenic variants of FGFR3 presents an additional challenge for antibody-mediated blockade. Results: We generated a tetravalent bispecific FGFR3xFGFR3 antibody that potently inhibits both FGFR3 point mutants and fusions with better efficacy than the conventional antibodies that we produced and a clinical-stage comparator antibody. Mechanistically, our bispecific antibody binds FGFR3 through two different epitopes located in immunoglobulin-like domains D1 and D2/3 respectively. It potently blocks the dimerization of FGFR3 S249C, the most common oncogenic variant, inhibiting receptor phosphorylation and downstream signaling. Additionally, our bispecific antibody inhibits the function of FGFR3 gatekeeper mutations (V557M/L) that are resistant to TKIs. In FGFR3-driven tumor models, our antibody is highly effective, providing efficacy similar to that of the FDA-approved TKI erdafitinib. Conclusion: We have characterized the properties of a tetravalent bispecific FGFR3xFGFR3 antibody that shows strong anti-tumor activity in models driven by FGFR3 S249C as well as by FGFR3-TACC3 fusion, outperforming a conventional antibody that was previously in clinical development. The activity of the bispecific antibody is superior to the mixture of the two parental antibodies and results from strong inhibition of FGFR3 dimerization. Our bispecific antibody provides a novel approach to achieve selective and potent inhibition of multiple oncogenic variants of FGFR3 in bladder cancer, including FGFR3 variants that are resistant to FGFR TKIs. Citation Format: Yan Yang, Naga Suhasini Avvaru, Zaoli Jiang, Nina Liu, Michael Rosconi, Bojie Zhang, Yinyin Li, Erica Ullman, John Chia-Yang Lin, Yang Shen, Christopher Daly. A bispecific antibody inhibits FGFR3 dimerization and is highly effective in FGFR3-driven tumor models [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr B129.

FGFR3 alterations in bladder cancer stimulate serine synthesis to induce immune-inert macrophages that suppress T-cell recruitment and activation.

Fibroblast growth factor receptor 3 (FGFR3) alterations are common in patients with bladder cancer (BCa). While the FGFR tyrosine kinase inhibitor erdafitinib has been approved as a targeted therapy for FGFR3-altered (aFGFR3) BCa patients, the response rate remains suboptimal, prompting development of strategies to improve treatment response. Here, we observed an immune-desert tumor microenvironment (TME) phenotype in human aFGFR3 BCa and demonstrated that mutant FGFR3 indirectly induces a "cold" TME in mouse BCa models. Single-cell RNA sequencing (scRNA-seq) revealed the central role of macrophages in inducing the cold TME of aFGFR3 tumors. Macrophages in aFGFR3 tumors exhibited reduced T cell recruitment and antigen presentation capabilities. Increased serine synthesis in BCa cells that was induced by mutant FGFR3 activated the PI3K/Akt pathway in macrophages, shifting them to an immune-inert phenotype. Targeting PI3K in aFGFR3 tumors with duvelisib achieved promising efficacy by reversing the macrophage phenotype, and combination therapy with duvelisib and erdafitinib demonstrated increased antitumor activity. Overall, these findings reveal the critical role of enhanced serine synthesis efflux from cancer cells with mutant FGFR3 in shifting macrophages to an immune-inert phenotype. Reversing the macrophage phenotype holds promise for enhancing erdafitinib efficacy.

Targeting FGFRs by pemigatinib induces G1 phase cell cycle arrest, cellular stress and upregulation of tumor suppressor microRNAs

BackgroundFibroblast growth factor receptor (FGFR) gene family alterations are found in several cancers, indicating their importance as potential therapeutic targets. The FGFR-tyrosine kinase inhibitor (TKI) pemigatinib has been introduced in the treatment of advanced cholangiocarcinoma and more recently for relapsed or refractory myeloid/lymphoid neoplasms with FGFR2 and FGFR1 rearrangements, respectively. Several clinical trials are currently investigating the possible combination of pemigatinib with immunotherapy.In this study, we analyzed the biological and molecular effects of pemigatinib on different cancer cell models (lung, bladder, and gastric), which are currently objective of clinical trial investigations.MethodsNCI-H1581 lung, KATO III gastric and RT-112 bladder cancer cell lines were evaluated for FGFR expression by qRT-PCR and Western blot. Cell lines were treated with Pem and then characterized for cell proliferation, apoptosis, production of intracellular reactive oxygen species (ROS), and induction of senescence. The expression of microRNAs with tumor suppressor functions was analyzed by qRT-PCR, while modulation of the proteins coded by their target genes was evaluated by Western blot and mRNA. Descriptive statistics was used to analyze the various data and student’s t test to compare the analysis of two groups.ResultsPemigatinib exposure triggered distinct signaling pathways and reduced the proliferative ability of all cancer cells, inducing G1 phase cell cycle arrest and strong intracellular stress resulting in ROS production, senescence and apoptosis. Pemigatinib treatment also caused the upregulation of microRNAs (miR-133b, miR-139, miR-186, miR-195) with tumor suppressor functions, along with the downregulation of validated protein targets with oncogenic roles (c-Myc, c-MET, CDK6, EGFR).ConclusionsThese results contribute to clarifying the biological effects and molecular mechanisms mediated by the anti-FGFR TKI pemigatinib in distinct tumor settings and support its exploitation for combined therapies.

A phase 2 study of HMPL-453, a selective FGFR tyrosine kinase inhibitor (TKI), in patients with previously treated advanced cholangiocarcinoma containing FGFR2 fusions.

e16118 Background: Patients (pts) with advanced cholangiocarcinoma (CCA) who progressed on or after 1L chemotherapy have few treatment options. FGFR2 fusions or rearrangements occur in 10–16% of pts in global and 6.14% in Chinese pts with intrahepatic cholangiocarcinoma (iCCA), and may predict tumor susceptibility to FGFR inhibitors. HMPL-453 is a novel, selective tyrosine kinase inhibitor against FGFR1, 2, and 3. Here, we report results from an open-label, multi-cohort, single-arm phase 2 study (NCT04353375). Methods: Pts with histologically or cytologically confirmed locally advanced or metastatic iCCA with FGFR2 fusions who were treated at least one previous line of systemic therapy were eligible and included in this analysis. They received 21-day cycles of HMPL-453 orally with 150 mg (QD, cohort 1) or 300 mg (QD, 2w on/1w off, cohort 2) until disease progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR) per RECIST 1.1. Results: At data cutoff (Sep 21, 2022), a total of 25 iCCA pts (12 in cohort 1, 13 in cohort 2) were enrolled and treated with HMPL-453. Median age was 51 yrs (range 28-76) and 12 (48%) were male. All pts had received ≥1 prior treatment line and 21 (84%) had received previous gemcitabine-based chemotherapy. The median follow-up duration was 12 months (mos) and 4.1 mos for cohort 1 and cohort 2, respectively. Of 22 evaluable pts (12 in cohort 1 and 10 in cohort 2) who had at least one post-baseline tumor assessment, the best overall response by investigator assessment was confirmed partial response in seven (31.8%) pts and stable disease in an additional 12 pts (54.5%), resulting in a disease control rate (DCR) of 86.4%. Specifically, in cohort 2 the confirmed ORR was 50% (95% CI, 18.7%–81.3%) and DCR was 90% (95% CI, 55.5%–99.7%). Duration of response was not reached in either cohort. Median progression-free survival was 5.7 (95% CI, 2.6, NR) mos in cohort 1 and not yet mature in cohort 2. Of all pts, 23 (92%) experienced ≥1 treatment-related adverse events (TRAEs). The most common TRAEs (any grade) were diarrhea (56%), dry mouth (44%), and blood phosphorus increased (44%). The common Gr ≥3 TRAEs (≥5% pts) were decreased neutrophil count (8%), nail toxicity (8%) and palmar-plantar erythrodysesthesia syndrome (8%). Compared to cohort 1, pts in cohort 2 experienced a lower incidence of Gr ≥3 TRAEs (23.1% vs 58.3%), less dose interruption/reduction (32.0% vs 41.7%) and less treatment discontinuation (0.0% vs 16.7%) due to TRAE. Based on the better safety profile and preliminary efficacy, 300mg, QD, 2w on/1w off was chosen as the recommended phase 2 dose (RP2D). Conclusions: HMPL-453 showed promising efficacy, particularly in RP2D regimen (300 mg, QD, 2w on/1w off) and acceptable toxicity in pts with previously-treated advanced iCCA and FGFR fusions. These results warrant further study in pts with advanced iCCA. Clinical trial information: NCT04353375 .

Abstract 3918: Kinase domain duplications of FGFR1 and MET are potential therapeutic targets

Abstract Background: Kinase domain duplication (KDD) is recently recognized as an oncogenic driver. Therapeutic potential has been established in EGFR-KDDs in non-small cell lung cancer, and our group recently showed resistance mechanism in lung cancers harboring EGFR-KDDs treated with EGFR tyrosine kinase inhibitors (TKIs). However, the frequency and oncogenic role of KDDs in other receptor tyrosine kinases has been elusive. Methods: To investigate the frequency of KDDs in advanced cancer patients, we developed in-house algorithm to detect KDDs in high-depth panel sequencing dataset and evaluated its performance using large-scale panel sequencing data from Seoul National University Hospital (SNUH). In short, the algorithm collects reads with soft clips from a modified GATK best practice pipeline for clinical NGS data processing. The collected reads are then grouped according to their matched position and insert size, and evidences of each group (number of splitting and spanning reads) are collected to yield a set of initial candidates. Finally, the initial candidates were manually inspected after quality control by removing false-positive candidates, such as non-target genes or consistent findings. Then, we established cell lines transfected with KDDs of FGFR1 and MET to validate oncogenic role of identified KDDs in the cohort. Using these transformed cell lines, we investigated carcinogenicity with cell viability assay, immunoblot assay and colony formation assay. FGFR TKIs and MET TKIs were used to uncover the possibility of therapeutic targets in the KDDs. Results: Using the in-house algorithm, we identified FGFR1-KDDs from brain tumors (n=4), EGFR-KDDs from lung (n=1) and brain (n=2) tumors, and MET-KDD from a lung tumor (n=1) in a total of 3,932 cancer samples, with 0.2% frequency. All three kinds of KDDs contained full-length of kinase domains of each gene. Ba/F3 cells transfected with the FGFR1-KDD constructs proliferated well without IL-3 (1239- and 1019-fold higer than wild-type FGFR1), while wild-type FGFR1 Ba/F3 cells did not. This growth potential was diminished by FGFR TKIs BGJ398 (IC50, 0.063 ± 0.065nM), PD173074 (IC50, 1.498 ± 1.021nM), and ponatinib (IC50, 5.69 ± 3.05nM). Reduced expressions of downstream pathway proteins including phospho-FGFR1, phospho-Akt, and phospho-Erk were confirmed by immunoblot assays. NIH-3T3 cells transfected with MET-KDD construct also showed growth advantage compared to wild-type MET NIH-3T3 cells. Capmatinib, a MET TKI, inhibited colony formation of MET-KDD NIH-3T3 cells with reduced phospho-MET expression. Conclusion: In this study, we validated newly developed KDD-detection computational methods using targeted DNA sequencing data. Using this algorithm, we found 0.2% of KDDs in 3,932 cancer samples, including EGFR, FGFR1, and MET. In addition to EGFR-KDDs, our study reveals that both FGFR1- and MET-KDD can be oncogenic and therapeutic targets in brain and lung cancer patients. Citation Format: Chaelin Lee, Sungyoung Lee, Hongseok Yun, Jeonghwan Youk, Tae Min Kim, Soyeon Kim, Bhumsuk Keam, Miso Kim, Dong-Wan Kim. Kinase domain duplications of FGFR1 and MET are potential therapeutic targets. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3918.

PMON30 Low-dose Infigratinib, an Oral Selective Fibroblast Growth Factor Receptor Tyrosine Kinase Inhibitor, Demonstrates Activity in a Preclinical Model of Hypochondroplasia

Abstract Background Fibroblast growth factor receptor 3 (FGFR3) gain-of-function mutations play a crucial role in achondroplasia (ACH), thanatophoric dysplasia (TD), and hypochondroplasia (HCH). HCH is a less severe form of dwarfism than ACH, but similarly is caused by gain-of-function mutations in the FGFR3 gene. HCH is characterized by a disproportionate short stature and a growth deficit affecting both endochondral and intramembranous ossification. While multiple therapeutic strategies are being tested for ACH, currently there are no approved therapeutic options for individuals with HCH. We tested the hypothesis that the oral, selective FGFR tyrosine kinase inhibitor (TKI) infigratinib (BGJ398) could improve the HCH phenotype and improve endochondral and intramembranous ossification in a preclinical mouse model of HCH Fgfr3N534K/+. Methods The first Hch mouse model studied expresses the most frequent human mutation p.Asn540Lys (Fgfr3Asn534Lys/+), and exhibits a mild dwarfism and most of the hallmarks of the human pathology. Fgfr3N534K/+ mice received subcutaneous injections of infigratinib or vehicle control every 3 days (1 mg/kg) or daily (1 mg/kg) for 15 days (post-natal day [PND] 4–19) or 21 days (PND 3–24), respectively. Results Fgfr3N534K/+ mice treated with 1 mg/kg infigratinib every 3 days did not show obvious and significant modification of the dwarf phenotype. In contrast, Fgfr3N534K/+ mice treated with 1 mg/kg infigratinib daily for a total of 21 days showed a statistically significant increase in appendicular and axial skeletal measures. Length of the long bones was statistically significantly increased in Fgfr3N534K/+ mice compared with Fgfr3+/+ mice (tibia +3.18%, femur +3.16%, humerus +3.04%, ulna +2.94%, radius +3.01%). Treatment also modified the skull shape (skull width, skull height, nasal bone length and naso-occipital length), the length of the mandible and skull base, as demonstrated by measurement of the foramen magnum (foramen magnum length +3.72%). Infigratinib treatment modified the cartilage growth plate organization, in particular the hypertrophic chondrocyte area. Finally, the high activation of the MAP kinase pathway due to the HCH missense FGFR3 mutation was reduced by treatment, as revealed by the immunolabelling of phosphorylated Erk1/2 proteins. Conclusions Treatment with daily 1 mg/kg infigratinib improved the length and weight of Fgfr3N534K/+ mice and significantly modified the skull and the axial and appendicular skeleton. We demonstrated in Fgfr3N534K/+ mice that infigratinib is able to counteract the constitutive activation of FGFR3 due to the heterozygous N540K mutation localized in the tyrosine kinase 1 domain of the protein. These results provide a rationale for targeting FGFR3 with a specific TKI for the treatment of children with HCH. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

FGFR1 Antibody Validation and Characterization of FGFR1 Protein Expression in ER+ Breast Cancer.

Clinical trials in patients with ER+ breast cancer with or without FGFR pathway somatic alterations have shown limited clinical benefit from treatment with FGFR tyrosine kinase inhibitors alone or in combination with endocrine therapy. This is likely because of an inadequate predictive biomarker to select appropriate patients. In this study, we evaluated 4 anti-FGFR1 antibodies in breast cancer cell lines and patient-derived xenografts with FGFR1 amplification. We correlated D8E4 expression in 209 tumors from postmenopausal patients with stage I-III operable ER+ breast cancer with FGFR1 amplification status as determined by fluorescence in situ hybridization. FGFR1 amplification was identified in 10% of tumors (21/209), 80% of which exhibited membranous FGFR1 expression; however, only 50% of amplified cases showed strong, complete membranous staining (3+) based on established criteria to score HER2 by immunohistochemistry. These findings suggest the combined evaluation of FGFR1 status by immunohistochemistry and fluorescence in situ hybridization may need to be incorporated into the selection of patients for trials with FGFR inhibitors.

Deciphering Genetic Alterations of Taiwanese Patients with Pancreatic Adenocarcinoma through Targeted Sequencing.

Pancreatic adenocarcinoma (PAC) is the 8th leading cause of cancer-related deaths in Taiwan, and its incidence is increasing. The development of PAC involves successive accumulation of multiple genetic alterations. Understanding the molecular pathogenesis and heterogeneity of PAC may facilitate personalized treatment for PAC and identify therapeutic agents. We performed tumor-only next-generation sequencing (NGS) with targeted panels to explore the molecular changes underlying PAC patients in Taiwan. The Ion Torrent Oncomine Comprehensive Panel (OCP) was used for PAC metastatic lesions, and more PAC samples were sequenced with the Ion AmpliSeq Cancer Hot Spot (CHP) v2 panel. Five formalin-fixed paraffin-embedded (FFPE) metastatic PAC specimens were successfully assayed with OCP, and KRAS was the most prevalent alteration, which might contraindicate the use of anti-EGFR therapy. One PAC patient harbored a FGFR2 p. C382R mutation, which might benefit from FGFR tyrosine kinase inhibitors. An additional 38 samples assayed with CHP v2 showed 100 hotspot variants, collapsing to 54 COSMID IDs. The most frequently mutated genes were TP53, KRAS, and PDGFRA (29, 23, 10 hotspot variants), impacting 11, 23, and 10 PAC patients. Highly pathogenic variants, including COSM22413 (PDGFRA, FATHMM predicted score: 0.88), COSM520, COSM521, and COSM518 (KRAS, FATHMM predicted score: 0.98), were reported. By using NGS with targeted panels, somatic mutations with therapeutic potential were identified. The combination of clinical and genetic information is useful for decision making and precise selection of targeted medicine.

Immunomodulation via FGFR inhibition augments FGFR1 targeting T-cell based antitumor immunotherapy for head and neck squamous cell carcinoma

ABSTRACT Fibroblast growth factor receptor 1 (FGFR1) is overexpressed in multiple types of solid tumors, including head and neck squamous cell carcinoma (HNSCC). Being associated with poor prognosis, FGFR1 is a potential therapeutic target for aggressive tumors. T cell-based cancer immunotherapy has played a central role in novel cancer treatments. However, the potential of antitumor immunotherapy targeting FGFR1 has not been investigated. Here, we showed that FGFR-tyrosine kinase inhibitors (TKIs) augmented antitumor effects of immune checkpoint inhibitors in an HNSCC mouse model and upregulated tumoral MHC class I and MHC class II expression in vivo and in vitro. This upregulation was associated with the mitogen-activated protein kinase signaling pathway, which is a crucial pathway for cancer development through FGFR signaling. Moreover, we identified an FGFR1-derived peptide epitope (FGFR1305-319) that could elicit antigen-reactive and multiple HLA-restricted CD4+ T cell responses. These T cells showed direct cytotoxicity against tumor cells that expressed FGFR1. Notably, FGFR-TKIs augmented antitumor effects of FGFR1-reactive T cells against human HNSCC cells. These results indicate that the combination of FGFR-TKIs with immunotherapy, such as an FGFR1-targeting peptide vaccine or immune checkpoint inhibitor, could be a novel and robust immunologic approach for treating patients with FGFR1-expressing cancer cells.

1308P Efficacy and safety of anti-PD-1 therapy plus anlotinib in previously treated advanced NSCLC

Nivolumab or pembrolizumab is the standard second-line treatment for patients (pts) with advanced NSCLC. Anlotinib is an oral VEGFR, FGFR, PDGFR and c-Kit tyrosine kinase inhibitor. The interaction between tumor immune microenvironment and angiogenesis has been well established. This study was designed to assess the benefit and optimal time of nivolumab or pembrolizumab plus anlotinib in previously treated advanced NSCLC.

Nuclear FGFR1 Regulates Gene Transcription and Promotes Antiestrogen Resistance in ER+ Breast Cancer.

FGFR1 overexpression has been associated with endocrine resistance in ER+ breast cancer. We found FGFR1 localized in the nucleus of breast cancer cells in primary tumors resistant to estrogen suppression. We investigated a role of nuclear FGFR1 on gene transcription and antiestrogen resistance. Tumors from patients treated with letrozole were subjected to Ki67 and FGFR1 IHC. MCF7 cells were transduced with FGFR1(SP-)(NLS) to promote nuclear FGFR1 overexpression. FGFR1 genomic activity in ER+/FGFR1-amplified breast cancer cells ± FOXA1 siRNA or ± the FGFR tyrosine kinase inhibitor (TKI) erdafitinib was examined by chromatin immunoprecipitation sequencing (ChIP-seq) and RNA sequencing (RNA-seq). The nuclear and chromatin-bound FGFR1 interactome was investigated by mass spectrometry (MS). High nuclear FGFR1 expression in ER+ primary tumors positively correlated with post-letrozole Ki67 values. Nuclear FGFR1 overexpression influenced gene transcription and promoted resistance to estrogen suppression and to fulvestrant in vivo. A gene expression signature induced by nuclear FGFR1 correlated with shorter survival in the METABRIC cohort of patients treated with antiestrogens. ChIP-Seq revealed FGFR1 occupancy at transcription start sites, overlapping with active transcription histone marks. MS analysis of the nuclear FGFR1 interactome identified phosphorylated RNA-Polymerase II and FOXA1, with FOXA1 RNAi impairing FGFR1 recruitment to chromatin. Treatment with erdafitinib did not impair nuclear FGFR1 translocation and genomic activity. These data suggest nuclear FGFR1 contributes to endocrine resistance by modulating gene transcription in ER+ breast cancer. Nuclear FGFR1 activity was unaffected by FGFR TKIs, thus supporting the development of treatment strategies to inhibit nuclear FGFR1 in ER+/FGFR1 overexpressing breast cancer.

A phase II open-label study in adult and adolescent patients (pts) with advanced solid tumors harboring fibroblast growth factor receptor (FGFR) gene alterations.

TPS480 Background: The pan- FGFR tyrosine kinase inhibitor erdafitinib is approved by the US Food and Drug Administration for adults with locally advanced or metastatic urothelial carcinoma and susceptible FGFR3/2 genetic alterations who have progressed during or after ≥ 1 line of prior platinum-containing chemotherapy. FGFR gene alterations are potential oncogenic drivers that have been reported in many solid tumors in adult and pediatric pts. Because of limited response to standard of care options in pts failing systemic therapy, there is strong rationale to assess the safety and efficacy of erdafitinib in adolescent and adult pts with advanced solid tumors and FGFR alterations. Methods: This phase 2, open-label study (RAGNAR/42756493CAN2002; NCT04083976) will include pts aged ≥ 12 years with histologically confirmed unresectable, locally advanced, or metastatic solid tumors (except urothelial tumors) harboring predefined FGFR mutations or fusions. Eligibility screening includes molecular screening for FGFR alterations by central or local next-generation sequencing assays, and other clinical criteria. Pts will enroll into either a broad panel cohort (BPC) of target FGFR alterations or an exploratory cohort (EC) for FGFR alterations that do not meet criteria for BPC. Approximately 280 pts (BPC, n = 240; EC, n = 40) will be enrolled. The primary efficacy end point is overall response rate (ORR) as assessed by the independent review committee. Secondary end points include investigator-assessed ORR, duration of response, disease control rate, progression-free survival, overall survival, safety, pharmacokinetics, and health-related quality of life. Safety assessments include adverse events, vital signs, electrocardiograms, physical examinations, laboratory tests, performance status assessment, growth assessments in adolescents, and ophthalmologic examination. As of December 2019, pts are being enrolled at ~158 sites in 15 countries. Results of this study will provide efficacy and safety data for erdafitinib across multiple solid tumors with FGFR alterations and evaluate the potential benefit of targeting the underlying altered biology of FGFR irrespective of tumor histology in adult and adolescent pts. Clinical trial information: NCT04083976.

A randomized phase II multi-institutional trial of anlotinib plus docetaxel versus docetaxel in EGFR-wild-type non-small cell lung cancer (NSCLC) patients after progression on first-line platinum-base chemotherapy: ALTER-L018.

e21703 Background: Anlotinib is an oral VEGFR, FGFR, PDGFR and c-Kit tyrosine kinase inhibitor, which can prolong both PFS and OS of refractory advanced NSCLC patients in phase III trial: ALTER0303. The combination of docetaxel and ramucirumab/nintedanib had been demonstrated activity in the second line therapy setting for NSCLC. We performed ALTER-L018 to assessed the safety and efficacy of anlotinib with docetaxel in EGFR-wild type refractory advanced NSCLC (NCT03624309). Methods: Patients (pts) with EGFR-wild type refractory advanced NSCLC, who failed to first-line platinum-based chemotherapy, were randomized to group A(anlotinib: 12mg QD from day 1 to 14 of a 21-day cycle +docetaxel: 75mg/m2 Q3W) and group B(docetaxel: 75mg/m2 Q3W). The primary end points is PFS, and secondary end points include OS, ORR, DCR and safety. Results: Between January and December 2019, 36 pts were enrolled at 10 institutions in Hunan China, with 31(15 in group A, 16 in group B) of these individuals being evaluable for treatment efficacy and safety. Pt characteristics(group A/ group B): median age: 55(39-70)/57(44-67); male: 73%/81%; non-squamous NSCLC: 86%/75%. Median PFS were 5.3 months (95%CI:2.76-7.85) in group A and 2.3 months (95%CI, 1.14-3.46) in group B (HR 0.42; 95% CI:0.16-1.13; p = 0.047); In group A and B, ORR and DCR were 26.67% versus 0%(p = 0.043), 60.00% versus 31.25%(p = 0.16), respectively. Among 31 pts, 89% of treatment-related AEs (TRAEs) were grade 1 or 2, and the most common TRAEs in group A were hand-foot syndrome, pruritus and insomnia of 13%(2/15) each; in group B were alopecia, constipation and anemia of 12%(1/16) each. Toxicities≥grade 3(TRAEs) included: neutropenia, leukopenia, diarrhea and hrombocytopenia, 6.6%(1/15) each in group A. There was 1 grade 5 AE in group A. Conclusions: This combination of anlotinib and docetaxel with significant difference PFS prolonging and manageable safety profile, is a viable option in relapsed NSCLC, should be considered following progression on platinum-based chemotherapy. It will be further explored in a randomized phase III trial. Clinical trial information: NCT03624309.

The efficacy and safety profile of anlotinib with etoposide plus cisplatin/carboplatin in treatment-naive extensive-stage small cell lung cancer(SCLC) patients: Results from a phase II single-arm trial.

9066 Background: Combination of etoposide and cisplatin/carboplatin is the most commonly used initial chemoptherapy regiment in extensive-stage small cell lung cancer. A meta-analysis released that, there is no significant difference was observed in Objective response rate(ORR), progression-free survival (PFS), or overall survival(OS) in patients(pts) receiving cisplatin-base versus carboplatin-based regimens. We performed a single-arm phase II trial to determine if maintain of single-agent anlotinib, an oral VEGFR, FGFR, PDGFR and c-Kit tyrosine kinase inhibitor, after 4-6 cycles of anlotinib + etoposide + cisplatin/carboplatin would improve PFS and ORR. Methods: SCLC pts (18~70 yrs, extensive-stage SCLC, no prior systematic chemo/ICI therapy) received anlotinib( 12mg QD from day 1 to 14 of a 21-day cycle) +etoposide( 100mg/m2, d1~3 of 21-day cycle)+ cisplatin( 75-80mg/m2,Q3W)/ carboplatin( AUC = 5~6,Q3W) for 4~6 cycles, and anlotinib maintenance. The dual-primary endpoint were PFS and ORR. Results: Between Oct.2018 to Dec.2019, 27 pts enrolled and included in the efficacy and safety analysis: age: median 62 (range:44-71); male 93%; cisplatin/ carboplatin/ both 11%/78%/11%; 37%(10/27) of pts required chemotherapy dose modification only, and the other 30% (8/27) of pts required anlotinib+ chemotherapy dose modification.The median PFS was 9.61 months ( 95%Cl:7.80-11.42). ORR was 77.78% (21/27), disease control rate (DCR) was 96.30% (26/27).Toxicities≥grade 3 included: neutropenia 22%, leukopenia 11%, hand-foot syndrome 15%, nausea 4%, mucositis 4%, edema 4%, anorexia 4%, xerostomia 4% and fatigue 4%; there were no grade 5 toxicities. Conclusions: Combined treatment with anlotinib plus etoposide and cisplatin/carboplatin for treatment-naive extensive-stage SCLC was well tolerated with promising PFS and ORR to date but showed no new risk for AEs. Based on these encouraging results, phase III trial of anlotinib plus etoposide and cisplatin/carboplatin for treatment-naive SCLC has been warranted.

SUN-101 Support for a New Therapeutic Approach of Using a Low-Dose FGFR Tyrosine Kinase Inhibitor (Infigratinib) for Achondroplasia

Background: Achondroplasia (ACH) is the most common non-lethal skeletal dysplasia. Fibroblast growth factor receptor 3 (FGFR3) plays a crucial role in bone elongation, demonstrated by FGFR3 gain-of-function mutations in individuals with ACH and hypochondroplasia. Multiple therapeutic strategies have been considered for ACH, the most advanced is to employ an analog of C-type Natriuretic Peptide (CNP), which antagonizes the MAP kinase (MAPK) pathway. Here, we evaluated a therapeutic strategy that targets all pathways downstream of FGFR3 (e.g., STAT1), not just MAPK. We hypothesized that a very low dose of the oral selective FGFR1-3 tyrosine kinase inhibitor (TKI) infigratinib (BGJ398) would be able to improve defective bone elongation. We also hypothesized that infigratinib would have greater potency at lower concentrations in an ACH cell line than a CNP analog (e.g., vosoritide) given its effects on multiple downstream pathways. Methods: A mouse model (Fgfr3Y367C/+) mimicking ACH was treated with subcutaneous injections of infigratinib daily (0.2 or 0.5 mg/kg/day) or intermittently (1 mg/kg, every 3 days) for a treatment duration of 15 days (PND1-15). In vivo results were compared with vehicle-treated mutant mice. TAN 4-18-chondrocytes, a human chondrocyte line expressing a heterozygous Y373C FGFR3 mutation, were treated with multiple concentrations of infigratinib and vosoritide and MAPK levels were measured. Results: We observed a significant improvement of the upper (humerus +7%, ulna +11%) and lower (femur +11%, tibia +16%) limbs at 0.5 mg/kg/day, and improvement in the foramen magnum. The effect of infigratinib on bone elongation was reduced with a lower dose (0.2 mg/kg), confirming a dose-response relationship. With intermittent injections of infigratinib (1 mg/kg, every 3 days), gain of growth was significant for all the long bones (+7%) and the size of the foramen magnum was increased. Modification of the growth plate structure, displaying better organization, was also seen. In cell line data, compared with FGF18-treated TAN 4-18-chondrocytes, concentrations of 10-6M to 10-10M infigratinib led to statistically significant (p<0.05) improvements. With vosoritide treatment, a concentration of 10-4M led to statistically significant improvements compared with FGF18-treated chondrocytes (p<0.05), although this was not seen at 10-5M. Conclusions: Preclinical ACH mouse model data indicate that low, as well as intermittent, doses of infigratinib promote growth and can improve the foramen magnum. No apparent toxicity of infigratinib was observed, suggesting that TKI therapy has the potential to be a valuable and relevant option for children with ACH. Furthermore, cell line data indicate that infigratinib showed superior potency over a CNP analog, suggesting that inhibition of multiple FGFR3-related pathways vs MAPK inhibition alone may lead to increased efficacy.

Facts and New Hopes on Selective FGFR Inhibitors in Solid Tumors.

Precision oncology relies on the identification of molecular alterations, responsible for tumor initiation and growth, which are suitable targets of specific inhibitors. The development of FGFR inhibitors represents an edifying example of the rapid evolution in the field of targeted oncology, with 10 different FGFR tyrosine kinase inhibitors actually under clinical investigation. In parallel, the discovery of FGFR activating molecular alterations (mainly FGFR3 mutations and FGFR2 fusions) across many tumor types, especially urothelial carcinomas and intrahepatic cholangiocarcinomas, widens the selection of patients that might benefit from selective FGFR inhibitors. The ongoing concomitant clinical evaluation of selective FGFR inhibitors in molecularly selected solid tumors brings new hopes for patients with metastatic cancer, for tumors so far excluded from molecularly guided treatments. Matching molecularly selected tumors with selective FGFR inhibitors has indeed led to promising results in phase I and II trials, justifying their registration to be expected in a near future, such as the recent accelerated approval of erdafitinib granted by the FDA for urothelial cancer. Widening our knowledge of the activity, efficacy, and toxicities relative to the selective FGFR tyrosine kinase inhibitors under clinical investigation, according to the exact FGFR molecular alteration, will be crucial to determine the optimal therapeutic strategy for patients suffering from FGFR-driven tumors. Similarly, identifying with appropriate molecular diagnostic, every single tumor harboring targetable FGFR alterations will be of utmost importance to attain the best outcomes for patients with FGFR-driven cancer.