FGFR3 Alterations Research Articles

IMG-14. DIAGNOSTIC UTILITY OF THE T2-FLAIR MISMATCH SIGN FOR DNETS AND ITS ASSOCIATION WITH FGFR1 ALTERATIONS

Abstract BACKGROUND The T2-FLAIR mismatch sign, hyperintense T2-weighted signals with corresponding hypointensity on FLAIR sequence, has emerged as a potential diagnostic tool for identifying specific brain tumor subtypes. We tested the diagnostic utility of the sign in dysembryoplastic neuroepithelial tumors (DNETs) with and without FGFR1 alterations. METHODS We evaluated the T2-FLAIR mismatch sign in a cohort of 43 patients with definitive or probable DNET. Low-grade glioma patients with definite non-DNET diagnoses were chosen as control (n=43). Receiver operative curve analysis was performed, and the corresponding odds ratios were calculated. RESULTS Of the 43 DNET cases, 35 were definite, and 8 were probable DNETs. FGFR1 alterations were confirmed in 9 definitive DNETs. The area under the curve (AUC) for diagnosing DNET with the T2-FLAIR mismatch sign was 0.884 (DeLong CI: 0.2, 0.95) (Accuracy: 0.88, 95% CI: 0.80, 0.94; Sensitivity: 0.84; Specificity: 0.95); for definite DNET it was 0.891 (DeLong CI: 0.82, 0.96) (Accuracy: 0.90, 95% CI: 0.81, 0.95; Sensitivity: 0.87; Specificity: 0.94); for probable DNET it was 0.852 (DeLong CI: 0.69, 1;) (Accuracy 0.92, 95% CI: 0.81, 0.98; Sensitivity: 0.84; Specificity: 0.75), and for DNET with FGFR1 alterations was 0.977 (DeLong CI: 0.95, 1) (Accuracy 0.96, 95% CI: 0.87, 1; Sensitivity: 1; Specificity: 0.81). The odds of having DNET (definite +probable) if the T2-FLAIR mismatch sign was positive was 81.96 (CI: 16.25, 852.48, P<0.001), and DNET with FGFR1 is 315.4 (CI: 312.3, 318.5, P<0.001). CONCLUSION The T2-FLAIR mismatch sign is a reliable radiological biomarker for DNET and strongly predicts FGFR1 alterations in these tumors.

LGG-34. THE LANDSCAPE OF GLIOMAS IN CHILDREN, ADOLESCENTS AND YOUNG ADULTS REVEALS INSIGHTS ON GLIOMAGENESIS: A CANADIAN ADOLESCENTS AND YOUNG ADULTS NEURO-ONCOLOGY NETWORK (CANON) STUDY

Abstract BACKGROUND Gliomas are a heterogenous and common cancer in children, adolescents and young adults (CAYA, ages 0-39 years). Little is known about the biologic and clinical implications of gliomas in AYA limiting our ability to appropriately manage these patients. METHODS We compiled a population-based cohort of patients with glioma aged 0-39 years diagnosed between 2000-2020, performed molecular characterization of the tumors and collected clinical data including therapy and long-term outcome. RESULTS A total of 1456 patients, including 873 AYA patients were included. A pathogenic molecular alteration was found in 98% of AYA samples available. Strikingly, pediatric-type mutations were found in 31% of AYA glioma of which 37% were BRAF V600E and 23% FGFR alterations. Important differences were observed between gliomas in children versus AYAs. First, hemispheric tumors were enriched in AYAs compared to midline tumors in children, especially for RAS/MAPK alterations. Second, increased incidence of high grade tumors in AYA compared to children were observed for BRAF V600E and FGFR mutations (p<0.0001). In contrast, if these alterations were identified in AYA and the tumor was low grade, outcome was improved for BRAF V600E and FGFR mutant tumors in AYAs compared to pediatrics (for BRAF V600E 5 year PFS 55.6% <10 years, 78.1% for 10-20 years and 87.1% for 10-20 years of age, p=0.0002). Third, a specific time window for transformation was observed for each alteration (BRAF, FGFR, IDH). This correlated with different methylation profiles and transcriptional patterns between early midline and late hemispheric tumors. Increased senescence signatures were observed in older patients with low grade RAS/MAPK driven tumors with superior outcome. CONCLUSIONS Different cell of origin and secondary mutations shape tumor behavior and lead to either transformation or senescence during gliomagenesis in CAYA. These can affect early interventions and tailored approaches for gliomas by age and molecular alteration.

LGG-48. CLINICAL CHARACTERIZATION OF FGFR-ALTERED, PEDIATRIC LOW-GRADE GLIOMAS

Abstract BACKGROUND Pediatric low-grade glioma (pLGG) is the most common central nervous system tumor of childhood. Most pLGGs are driven by BRAF alterations, but a subset harbor activating mutations or fusions of FGFR1/2/3. Significantly less is known about the biologic activity, clinical course, and response to targeted inhibition of these FGFR-altered gliomas (FGFR pLGG). We sought to define the epidemiologic characteristics, molecular signature, prognostic markers, and clinical course of patients with FGFR pLGG. METHODS We performed a multi-institution, retrospective chart review of pediatric neuro-oncology patients treated at two large, academic cancer centers from 2012 – 2023 with tumor molecular profiling demonstrating any FGFR alteration. RESULTS Sixteen eligible patients were identified; 9 (56%) were female and median age was 12 years of age (range 6 - 18 years). Reported histologies included pilocytic astrocytoma (4), rosette-forming glioneuronal tumor (3), low grade glial/glioneuronal tumor (3), low grade glioma NOS (2), intermediate grade astrocytoma (1), dysembryoblastic neuroepithelial tumor (2), and pilomyxoid astrocytoma (1). FGFR point mutations were seen in 10/16 (62.5%) patients followed by FGFR-TACC1 fusions in 4/16 (25%) patients and two patients with FGFR1 tandem duplication. Metastatic disease was noted at diagnosis in two patients and upfront gross total resection was achieved in four patients. The most common systemic therapy for the remaining patients was Vincristine and/or Carboplatin. All sixteen patients are alive at median follow up of 52 months (range 6 - 198 months). CONCLUSIONS FGFR pLGG represent a distinct subset of tumors with unique biologic properties and clinical activity. Additional studies are needed to investigate this unique patient population to appropriately adapt our therapeutic approach and improve patient outcomes.

Neoadjuvant PD-(L)1 blockade plus platinum-based chemotherapy for potentially resectable oncogene-positive non-small cell lung cancer

BackgroundWhether programmed cell death-1/ligand-1 (PD-1/PD-L1) blockade-based neoadjuvant treatment may benefit locally advanced oncogene-mutant non–small cell lung cancer (NSCLC) patients remains controversial. This retrospective study was designed to observe the efficacy and safety of neoadjuvant PD-1/PD-L1 blockade plus chemotherapy versus chemotherapy and corresponding tyrosine kinase inhibitors (TKIs) in patients with resectable oncogene-positive NSCLC.MethodsPatients with potential resectable NSCLC harbouring oncogene alterations who had received neoadjuvant treatment were retrospectively recruited, and an oncogene-negative cohort of patients who received neoadjuvant PD-(L)1 blockade-based neoadjuvant treatment was reviewed for comparison during the same period. The primary aim was to observe the treatment efficacy and event-free survival (EFS) of these agents. Safety profile, molecular target, and immunologic factor data, including PD-L1 expression and tumour mutational burden (TMB), were also obtained.ResultsA total of 46 patients were recruited. Thirty-one of them harboured oncogene alterations, including EGFR, KRAS, ERBB2, ROS1, MET, RET, ALK, and FGFR3 alterations. Among the oncogene-positive patients, 18 patients received neoadjuvant PD-(L)1 blockade immunotherapy plus chemotherapy (oncogene-positive IO group), 13 patients were treated with neoadjuvant chemotherapy and/or corresponding TKIs or TKIs alone (oncogene-positive chemo/TKIs group), and the other 15 patients were oncogene negative and received neoadjuvant PD-(L)1 blockade plus chemotherapy (oncogene-negative IO group). The pathological complete response (pCR) and major pathological response (MPR) rates were 22.2% (4 of 18) and 44.4% (8 of 18) in the oncogene-positive IO group, 0% (P = 0.120) and 23.1% (3 of 13) (P = 0.276) in the oncogene-positive chemo/TKIs group, and 46.7% (7 of 15) (P = 0.163) and 80.0% (12 of 15) (P = 0.072) in the oncogene-negative IO group, respectively. By the last follow-up, the median EFS time had not reached in the oncogene-positive IO group, and was 29.5 months in the oncogene-positive chemo/TKIs group and 38.4 months in the oncogene-negative IO group.ConclusionCompared with chemotherapy/TKIs treatment, neoadjuvant treatment with PD-(L)1 blockade plus platinum-based chemotherapy was associated with higher pCR/MPR rates in patients with partially resectable oncogene-mutant NSCLC, while the pCR/MPR rates were lower than their oncogene-negative counterparts treated with PD-(L)1 blockade-based treatment. Specifically, oncogene alteration types and other predictors of response to immunotherapy should be taken into account in clinical practice.

LGG-29. BEYOND MAPK SIGNALING - GENOME-SCALE CRISPR/CAS9 SCREENS REVEAL NEW TARGETS FOR TREATMENT OF KIAA1549::BRAF-DRIVEN PEDIATRIC LOW-GRADE GLIOMA

Abstract Since the KIAA1549::BRAF fusion was discovered as the most common driver of pediatric low-grade glioma (pLGG), it has been hypothesized that the fusion induces oncogenicity through BRAF activation as a result of KIAA1549 replacing the BRAF negative regulatory N-terminus. This led to the rapid translation of MAPK pathway inhibitors into the clinical setting. Despite most tumors exhibiting promising initial responses, some tumors are not sensitive and about half of responsive tumors grow back after treatment cessation. Therefore, strategies that result in sustained tumor responses are desperately needed. We have recently performed genome-scale CRISPR/Cas9 screens across isogenic neural stem cell models transduced to express pLGG-associated oncogenes (KIAA1549::BRAF, BRAFV600E, and multiple FGFR1 and MYB family alterations) to generate a dependency map of genetic vulnerabilities associated with expression of these oncogenes. We also included normal neural stem cells to allow identification of genetic dependencies specifically induced by the expression of each oncogene. Surprisingly, through these efforts, we have discovered KIAA1549::BRAF expressing cells to harbor striking and specific dependency on multiple members of an enzymatic complex that exerts its activity outside of the MAPK signaling axis*. Interestingly, this enzymatic complex has been described to modify only a few substrates, including KIAA1549, suggesting specificity. We have now validated this dependency across other isogenic models of KIAA1549::BRAF-expressing cells. Finally, our KIAA1549::BRAF-expressing models exhibit preferential sensitivity to a tool compound that targets our novel enzyme, suggesting novel therapeutic potential for KIAA1549::BRAF. These findings highlight a MAPK pathway-independent avenue for therapeutically targeting the most frequent genomic alterations in pediatric brain tumors. Consequently, we also propose that the fusion partner KIAA1549 is instrumental for the aberrant BRAF signaling driving pLGGs. (* we are currently in the process of working with our IP offices to ensure that we can disclose the names of the genes and proteins at the ISPNO meeting)

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.

Surgical Outcomes and Genomic Insights of Nonclear Cell Renal Cell Carcinoma With Synchronous and Metachronous Nodal Disease.

Oncological outcomes in patients with nonclear cell renal cell carcinoma (non-ccRCC) treated with surgery for locoregional nodal disease (ND) remain incompletely characterized. The objective was to investigate the characteristics and outcomes of non-ccRCC patients treated with lymph node dissection (LND) and salvage-LND (S-LND). A total of 1627 patients underwent nephrectomy for nonmetastatic non-ccRCC at Memorial Sloan Kettering Cancer Center between 2007 and 2023. Histology was grouped as papillary, chromophobe, unclassified, and rare subtypes. Retrospective evaluation identified 2.5% (n = 40) of patients with nodal disease at time of nephrectomy (synchronous-ND) and 1.1% (n = 18) with metachronous nodal disease limited to the retroperitoneum (metachronous-ND). Patients' demographics and tumor characteristics were recorded and evaluated by univariate and multivariate cox regression models. Recurrence-free survival (RFS) and overall survival (OS) were estimated by the Kaplan-Meier method. Patients who underwent tumor DNA sequencing during their clinical course were considered for genomic analysis. OS trended toward longer in metachronous-ND (51 vs 105 months; P = .2), though 23% of patients with synchronous-ND were recurrence-free at 45 months median follow-up. In multivariate analysis, rare histologies were associated with decreased OS (P = .030) and metachronous-ND with improved OS (P = .036). RFS and OS after S-LND was 15 and 96 months, respectively. Late onset of metachronous-ND/recurrence was associated with improved OS (P = .008). Genetic alterations in SETD2, TP53, B2M, and FGFR3 were exclusively seen in synchronous-ND, and tumor mutation burden (TMB) was also higher in patients with synchronous-ND (P = .016). Patients with metachronous-ND tend to have prolonged OS compared to synchronous-ND, but a substantial portion of patients with synchronous-ND still enter a durable disease-free state following LND. S-LND can likewise provide long-term survival, particularly in patients with longer time to metachronous nodal recurrence. Synchronous-ND was associated with SETD2, TP53, and NF2 alteration as well as higher TMB.

Impact of next generation sequencing in high grade glioma management.

e14031 Background: Recent advances in genomic profiling have improved our understanding of the molecular pathogenesis of high grade gliomas. Increased availability of high-throughput Next Generation Sequencing (NGS) allows the identification of genetic alterations which could direct personalized cancer treatments for HGG patients. Methods: All patients with high grade glioma (WHO Grade ≥3 glioma by 2016 or 2022 classification) in our institution, who underwent NGS testing between 2019-2023, were identified from a prospectively maintained electronic database. NGS results, from the Oncomine Precision Assay, a multi-gene panel which tests for 50 different mutations, were collated. Medical records were systematically reviewed to collect demographic, treatment and survival data. Alterations detected on NGS were characterized using the ESMO Scale for Clinical Actionability of Molecular Targets (ESCAT). Results: 53 patient samples underwent NGS testing (34 males [64%]; 19 females [36%]). Median age at diagnosis was 52 years (range: 20-72 years). Thirty patients (57%) had an ECOG PS 1 at first clinical review. 18 tumors (34%) were found to have MGMT promoter hypermethylation. 28 patients (53%) were found to have potentially actionable alterations according to the ESCAT scale; 19 (35%) EGFR mutations (ESCAT IIIA level evidence) were detected, 5 PIK3CA (9%) mutations (ESCAT IIIA), 3 FGFR3 (6%) alterations (ESCAT IIB), 2 patients with CDK 4 (4%) copy number gain (ESCAT IIIA), 2 PTPRZ1-MET (4%) fusions (ESCAT IIIA) and 1 BRAF V600E (2%) mutation (ESCAT IB). 4 patients were found to have multiple mutations on NGS. 1 sample had insufficient tissue for analysis. 2 patients (4%) were considered for targeted therapy based on NGS results (1 BRAF V600E mutation and 1 FGFR3 alteration) but both deteriorated in advance of commencing treatment. One patient received nivolumab for MSI-H recurrent GBM (ESCAT IIIB) but progressed within 3 months of commencing treatment. Conclusions: Despite advances in our understanding of the pathogenesis of these high grade gliomas and improved awareness of molecular targets, the delivery of targeted therapy to patients with HGG remains challenging. Rapid access to targeted therapy via compassionate access programmes and improved availability and access to clinical trials for patients with rare cancers and molecular alterations, is paramount.

Efficacy and safety of erdafitinib in pediatric patients with advanced solid tumors and FGFR alterations in the phase 2 RAGNAR trial.

10002 Background: Erdafitinib is an oral selective pan-fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitor approved in the US for adult patients (pts) with locally advanced or metastatic urothelial carcinoma with susceptible FGFR3 genetic alterations, as determined by an FDA-approved companion diagnostic test, whose disease has progressed on or after ≥1 line of prior systemic therapy. Primary analysis of the RAGNAR study Broad Panel Cohort demonstrated tumor agnostic efficacy in pts with solid tumors harboring predefined FGFR mutations or fusions (Pant 2023). Here we report on Final Analysis of efficacy and safety results from the Pediatric Cohort of the RAGNAR study. Methods: Pediatric pts ≥6 years with advanced solid tumors and any FGFR mutation, fusion, or tandem duplication received oral erdafitinib. Starting doses were 8 mg, 5 mg, and 3 mg daily for ages > 15 years, 12 to < 15 years, and 6 to < 12 years, respectively, in 21-day cycles with possible individualized up-titration based on serum phosphate and adverse events (AEs). The primary endpoint was objective response rate (ORR) (Response Evaluation Criteria in Solid Tumors [RECIST] 1.1 or Response Assessment in Neuro-Oncology [RANO]) by independent review committee (IRC). Secondary endpoints included ORR by investigator, duration of response (DOR), disease control rate (DCR), clinical benefit rate (CBR), progression-free survival (PFS), and overall survival (OS). Results: 11 pts (median age 13 years; range, 6-16; 64% female) received erdafitinib. Median follow-up was 9.7 months at data cutoff. Histologies included low-grade glioma (LGG-6 pts); high-grade glioma (HGG-3 pts); soft tissue sarcoma (1 pt), and temporal neurocytoma (TNEURO-1 pt). 7, 1, and 3 pts had FGFR1, FGFR2, and FGFR3 alterations, respectively. 6, 4, and 1 pts had FGFR fusions, mutations, and tandem duplication, respectively. Pts had a median of 1 prior line of systemic treatment; 6 (55%) had prior radiotherapy. At data cutoff, 1 of 3 pts (33%) with HGG and an FGFR1-TACC1 fusion achieved a partial response based on investigator assessment with a response duration of 19.8 months. Investigator-assessed objective responses were not observed in the other tumor types. DCR and CBR were 100% in pts with LGG and 67% in pts with HGG. Most common treatment-emergent adverse events (TEAEs) included hyperphosphatemia (64%), diarrhea (64%), pain in extremity (45%), alanine transaminase increased (36%), nausea (36%), and onycholysis (27%). No central serous retinopathy events occurred; related serious adverse events (SAEs) occurred in 4 (36%) pts, including 1 SAE of epiphysiolysis; there were no related TEAEs leading to death. Conclusions: In this small pediatric population comprising primarily refractory HGG and LGG with any FGFR alteration, erdafitinib demonstrated limited objective responses but promising disease control with acceptable safety. Clinical trial information: NCT04083976 .

Retroperitoneal leiomyosarcoma; Demographics, clinicopathological, survival analysis, role of adjuvant radiation and genomic analysis.

e23327 Background: Retroperitoneal leiomyosarcoma (RPL) is an exceedingly rare malignancy and is the second most common subtype of leiomyosarcomas. Most of the information concerning this rare disease is limited to case studies and few literature studies. The study's objectives were to assess the demographics, pathological factors, survival outcomes, genomic landscape and potential for targeted therapy. Methods: Data of retroperitoneal leiomyosarcoma were obtained from the Surveillance, Epidemiology, and End Results (SEER) database, with cases diagnosed between 2000 and 2020 used for this study and the Cancer Genome Atlas containing sequencing information for 27 cases of RPL. Results: A total of 1406 cases were extracted with mean age of diagnosis of 62.1 years. Of these, RPL had a higher incidence in women (71.5%), more cases affected Whites (58.7%). Histologically, in patients with known grading, most patients’ i.e. 62.35% were grade 3, G3 (poorly differentiated). Nearly all (99.9%) patients presented with a tumor size ≥4.1 cm. Local lymph nodes metastasis were positive in 76.0% of cases when lymph node status was reported. In known cases of distant metastases, the most common site was liver (8.9%). The main treatment modality was surgery only (26.7%, hazard ratio, HR 1.17, p-value < 0.001), followed by the standard of care (surgery and radiation) (18.4%, HR 1.03, p-value < 0.001), and radiation only (18.4%). Five-year overall survival was 40% and 5-year cause-specific survival was 64%. The highest 5-year survival was observed in patients undergoing surgery and radiation (57%), and in combination therapy (chemotherapy, surgery, and radiation) the 5-year survival was 39%. Genetic analysis found the most common mutations included TP53 (51.9%), RB1 (25.9%), and ATRX (14.8%). When accounting for deep deletions and rearrangements, total frequency of the alterations was higher such that TP53 (63.0%), RB1 (51.9%), and ATRX (18.5%). Potentially actionable alterations were rare but included activating alterations in FGFR1, PIK3CA and ESR1, as well as deep deletions of BRCA1. Conclusions: Retroperitoneal leiomyosarcoma is a very rare tumor where surgery and radiation has been the conventional therapy. Our study indicates there are genetic alterations in the majority of retroperitoneal leiomyosarcoma. To further understand the pathogenesis and survival factors, patients with RPL should be enrolled into national and international registries.

Efficacy and safety of erdafitinib in adults with breast cancer and prespecified fibroblast growth factor receptor alterations in the phase 2 open-label, single-arm RAGNAR trial.

1088 Background: Erdafitinib is an oral selective pan-fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitor approved in the US for adult patients (pts) with locally advanced or metastatic urothelial carcinoma with susceptible FGFR3 genetic alterations, as determined by an FDA-approved companion diagnostic test, whose disease has progressed on or after ≥1 line of prior systemic therapy. The primary analysis results from the RAGNAR study demonstrated tumor agnostic efficacy in patients with advanced solid tumors with predefined FGFR alterations after failure of standard therapies (Pant 2023). Here, we report results on patients with breast cancer in the RAGNAR study. Methods: Patients with breast cancer and prespecified FGFR1-4 alterations (mutations or fusions) who had documented disease progression after exhausting standard therapies received oral erdafitinib 8 mg daily with optional up-titration until disease progression or intolerable toxicity. The primary end point was objective response rate by Independent Review Committee (IRC). Secondary endpoints include duration of response, disease control rate, progression-free survival, overall survival, and safety. Results: At data cutoff (median follow up, 30.3 months), 16 patients with breast cancer received erdafitinib. Median age was 54 y (range 37-74); all (100%) patients were female and had visceral metastases. Patients had a median of 5 prior lines of systemic therapies (range 2-12); one (6%) patient had responded to the last line of therapy. Ten (63%) patients had FGFR fusions, and 6 (38%) had FGFR mutations. Mutations of TP53 and PIK3CA were found in 6/16 patients. Objective response rate and disease control rate by IRC were 31% (95% CI 11-59) and 69% (95% CI 41-89); objective response rate and disease control rate by investigator were 38% (95% CI 15-65) and 69% (95% CI 41-89), respectively. Median time to onset of response was 1.4 months. Responses were observed in patients with both FGFR2 fusions and with FGFR2/3 mutations. Median duration of response, progression free survival, and overall survival were 6.9 months, 5.7 months, and 8.9 months, respectively. Common adverse events (AEs) included stomatitis (81%), diarrhea (69%), and hyperphosphatemia (69%), dry mouth (63%), and palmar-plantar erythrodysesthesia (44%). Six (38%) patients had serious AEs. No patients discontinued erdafitinib due to AEs. No treatment-related deaths were observed. Conclusions: Erdafitinib demonstrated clinically meaningful activity in heavily pretreated patients with breast cancer and prespecified FGFR alterations. Safety data were consistent with the erdafitinib safety profile. Clinical trial information: NCT04083976 .

A phase III randomized trial of eribulin (E) with gemcitabine (G) vs standard of care (SOC) for patients (pts) with metastatic urothelial carcinoma (mUC) refractory to or ineligible for PD/PDL1 antibody (Ab): SWOG S1937 updated design.

TPS4617 Background: UC is 2nd most common genitourinary cancer. Enfortumab vedotin (EV) + pembrolizumab became a SOC in 2023 in frontline mUC setting. In previously treated mUC setting, erdafitinib is approved for pts with FGFR alterations, while all pts have the option of sacituzumab govitecan (SG) with objective response rate (ORR) of 27% (N=113). A phase I/II CTEP study of eribulin (E) for mUC established the activity of E with ORR of 37.5% and a median progression free survival (PFS) of 4.1 months (mo) and median overall survival (OS) of 9.5 mo (N=150). A phase II CTEP study of gemcitabine-eribulin (GE) in cisplatin ineligible mUC showed ORR of 50%, median OS of 11.9 mo and median PFS of 5.3 mo (N=24). The most common Grade 3-4 toxicities included: neutropenia 63%, anemia and fatigue 29%. Pts with liver metastases benefited from therapy with 71% ORR (n=7) for GE vs 24% for E (n=49). This trial has now been amended to account for first-line treatment changes and to include SG as a control arm option. Methods: This is an updated phase III, randomized trial comparing GE vs. SOC (SG, docetaxel, paclitaxel, or G monotherapy). E is given at 1.4mg/m2 on day (D) 1 and 8 of a 21 D cycle and G is given at 1000 mg/m2 on D1 and D8. SOC follows approved dosing. There is no limit to the number/sequence of prior regimens. In brief, all pts must have: received systemic therapy with EV; received PD1/PDL1 Ab or be deemed ineligible for PD1/PDL1 Ab. The study seeks to find at least a 50% increase in the primary endpoint of OS (Hazard Ratio (HR) = 0.667). The secondary endpoints include ORR, and progression free survival (PFS). One-sided 0.05 type I error to account and 80% power to detect a 50% improvement in OS. We require 92 eligible pts in each arm for a total of 184. The amended and restructured study was approved in January of 2024. Funding: National Institutes of Health/National Cancer Institute grants U10CA180888, U10CA180819. Eribulin is provided by Eisai. Clinical trial information: NCT04579224 .

Efficacy and safety of erdafitinib in adults with NSCLC and prespecified fibroblast growth factor receptor alterations in the phase 2 open-label, single-arm RAGNAR trial.

8515 Background: Erdafitinib is an oral selective pan-fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitor approved in the US for treatment of locally advanced or metastatic urothelial carcinoma in adults with susceptible FGFR3 alterations, as determined by FDA-approved companion diagnostic test, who have progressed during or after ≥1 line of prior systemic therapy. Primary analysis results from the RAGNAR study demonstrated tumor agnostic efficacy in patients with advanced solid tumors with predefined FGFR alterations after failure of standard therapies (Pant 2023). Here we report results on patients with non-small-cell lung cancer (NSCLC) in the RAGNAR study. Methods: Patients with advanced or metastatic squamous or non-squamous NSCLC with prespecified FGFR1-4 alterations (mutations/fusions) and with documented disease progression after exhausting standard therapies were included. Patients with other targetable alterations (eg, EGFR, ALK, ROS1) were excluded. Patients received oral erdafitinib until disease progression or intolerable toxicity. The primary end point was objective response rate by independent review committee. Secondary endpoints include duration of response, disease control rate, progression-free survival, overall survival, and safety. Results: At data cutoff (median survival follow-up of 23.7 months), 23 patients with NSCLC received erdafitinib. Median age was 63 years (range 50-79); 22 (96%) had metastases. Patients had a median of 2 prior lines of systemic therapies (range 1-7; 48% had 3+ prior lines); only 2 (9%) patients had responded to their prior line of therapy. Fourteen patients (61%) had squamous and 9 (39%) non-squamous histology; 13 patients (57%) had FGFRfusions and 10 (43%) had FGFR mutations. Three patients had CDKN2Aand 3 patients had PIK3CA co-alterations. Objective response rate by independent review committee was 26% (95% CI 10-48); disease control rate was 74% (95% CI 52-90). Median time to onset of response was 1.5 months. Responses were observed in 21% (3/14) of patients with squamous; 33% (3/9) with non-squamous histology, 29% (2/7) of patients with FGFR2, 25% (4/16) with FGFR3alterations, and in 20% (2/10) of patients with FGFR mutations and 31% (4/13) with fusions. Median duration of response, progression-free survival and overall survival were 4.6 months, 4.1 months, and 10.5 months, respectively. Most common adverse events (AEs) were diarrhea (65%), stomatitis (61%), dry mouth (44%), hyperphosphatemia (65%), dry skin (30%), and fatigue (22%); 6 (26%) had serious AEs; 2 (9%) discontinued erdafitinib due to AEs. No treatment-related deaths were observed. Conclusions: Erdafitinib demonstrated clinically meaningful activity in pre-treated patients with NSCLC and pre-specified FGFR alterations. Safety data were consistent with erdafitinib safety profile. Clinical trial information: NCT04083976 .

FGFR3 alterations (FGFRalt) in patients (pts) who develop locally advanced or metastatic urothelial cancer (mUC), and their association with tumor subtype and clinical outcomes in pts treated with erdafitinib (erda) vs. pembrolizumab (pembro).

4578 Background: Erda, an oral pan-fibroblast growth factor receptor (FGFR) tyrosine kinase inhibitor is approved to treat adult pts with locally advanced or mUC with susceptible FGFR3alt, whose disease progressed on or after at least one line of prior systemic therapy. In superficial and surgically resectable UC, FGFRalt has been shown to be highly associated with luminal subtype characterized by expression of luminal markers, low expression of basal markers and with immune cold / poor immune infiltration. In a randomized open-label phase III THOR study (Cohort 2), erda showed improvement in objective response and progression-free survival (PFS) compared to pembro, with no significant improvement in overall survival (OS). Exploration of subtypes in a large cohort of mUC pts has not been done and so a molecular analysis was undertaken to further understand the clinical findings. Methods: All available tumors from pts enrolled in Cohort 2 ( FGFRalt positive; N = 201) and a subset of FGFR wildtype (N = 116) were used to perform whole transcriptome RNA sequencing, where 152 and 84, respectively, passed quality control. The consensus single-sample classifier was applied to the RNAseq data to determine molecular subtypes. Tumor subtypes was correlated with treatment response to erda or pembro, PFS and OS. Results: Molecular classification of tumors identified a significant proportion of luminal-papillary (LumP) subtype in the tumors harboring FGFRalt compared to FGFR WT (78.3% vs. 36.9%, p < 0.001) vs. other subtypes: basal/squamous (Ba/Sq; 11.2% vs. 31.0%), stroma-rich (6.6% vs. 10.7%), neuroendocrine-like (0% vs. 2.4%), luminal-unstable (3.3% vs. 17.9%) and luminal-unspecified (0.7% vs. 1.2%), respectively. Consistently, FGFRalt type showed differential association with subtypes: 3.2% of fusions and 14.1% of mutations were detected in Ba/Sq subtype while 74.2% and 79.3%, respectively, were detected in LumP. Clinical outcomes evaluated within LumP subset showed a significant improvement in ORR of erda-treated vs. pembro-treated pts (41.7 vs. 19.7%; p = 0.01), which was consistent with the intent to treat (ITT) population (40.0% vs. 21.6%). Numerical improvement were observed in PFS in the LumP subtype between erda vs. pembro (5.5 vs 2.7 months) compared with the ITT population (4.4 vs 2.7). However, the benefit of erda over pembro in the LumP subtype did not translate to OS (10.9 vs. 12.9 months), similar to the ITT population (10.9 vs. 11.1 months). Conclusions: A significant overlap was identified between genomic selection of FGFRalt and the LumP subtype. Clinical outcomes based on transcriptomic analyses were consistent with those observed in the ITT population. These findings warrant further understanding of LumP tumors and association to treatment response. Clinical trial information: NCT03390504 .

300P Prognostic and predictive role of FGFR2 and IDH1 targetable alterations in advanced biliary tract cancer (aBTC): Data from the Italian ANITA dataset

300P Prognostic and predictive role of FGFR2 and IDH1 targetable alterations in advanced biliary tract cancer (aBTC): Data from the Italian ANITA dataset

The combination of gemcitabine plus an anti-FGFR inhibitor can have a synergistic antitumor effect on FGF-activating cholangiocarcinoma

Anti-FGFR treatment for cholangiocarcinoma (CCA) with fibroblast growth factor receptor (FGFR) alteration is a promising treatment option. Since the antitumor mechanisms of anti-FGFR inhibitors and conventional cytotoxic drugs differ, synergistic effects can be possible. This study aimed to evaluate the efficacy of the combined administration of gemcitabine (GEM) and pemigatinib in CCA cells with FGFR2 alterations. To simulate the treatment for patients with 3 kinds of CCA, chemonaïve CCA with activation of the FGF pathway, chemo-resistant CCA with activation of the FGF pathway, and CCA without FGF pathway activation (as controls), we evaluated 3 different CCA cell lines, CCLP-1 (with a FGFR2 fusion mutation), CCLP-GR (GEM-resistant cells established from CCLP-1), and HuCCT1 (without FGFR mutations). There was no significant difference between CCLP-1 and HuCCT1 in GEM suspensibility (IC50 = 19.3, 22.6 mg/dl, p = 0.1187), and the drug sensitivity to pemigatinib did not differ between CCLP-1 and CCLP-GR (IC50 = 7.18,7.60 nM, p = 0.3089). Interestingly, only CCLP-1 showed a synergistic effect with combination therapy consisting of GEM plus pemigatinib in vitro and in vivo. In a comparison of the reaction to GEM exposure, only CCLP-1 cells showed an increase in the activation of downstream proteins in the FGF pathway, especially FRS2 and ERK. In association with this reaction, cell cycle and mitosis were increased with GEM exposure in CCLP-1, but HuCCT1/CCLP-GR did not show this reaction. Our results suggested that combination therapy with GEM plus pemigatinib is a promising treatment for chemonaïve patients with CCA with activation of the FGF pathway.

Abstract B014: FGFR inhibition upregulates Nectin-4 expression in FGFR3 altered urothelial carcinoma

Abstract Bladder urothelial carcinoma (UC) is a common malignancy and remains a significant cause of mortality; however, in recent years there have been substantial advances in the treatment of metastatic UC (mUC). This includes the approval of the antibody drug conjugate (ADC) enfortumab vedotin, which targets Nectin-4, and the fibroblast growth factor receptor (FGFR) inhibitor erdafitinib (in FGFR2/3 altered tumors). Despite the impressive efficacy of these agents, most patients will ultimately develop progressive disease, underlining the need for further therapeutic development. Previous work has demonstrated that NECTIN4 expression and FGFR3 alterations are enriched in luminal subtypes of UC and NECTIN4 expression is higher in FGFR altered tumors. We validate these findings in scRNAseq from primary tumors as well as bulk RNAseq from murine models. Given the positive correlation between NECTIN4 and FGFR3 alterations we hypothesized that FGFR3 inhibition would downregulate Nectin-4 expression. To our surprise we found in vitro treatment with erdafitinib in cell lines with FGFR3 fusion proteins (RT112, RT4, SW780) lead to an increase in Nectin-4 protein levels. Additionally, in vitro FGFR inhibition in the UMUC-14 cell line which harbors an FGFR3S249C hotspot mutation, upregulates Nectin-4 protein levels. To further investigate this phenomenon, we engineered the FGFR3 WT cell line, 5637 to overexpress FGFR3-TACC3 or FGFR3S249C. We saw that FGFR3-TACC3 and FGFR3S249C overexpression both down regulated Nectin-4 indicating that FGFR3 activity negatively regulates Nectin-4 expression. We have also investigated the association between FGFR inhibition and Nectin-4 expression in two in vivo models: (1) in a xenograft model using the RT112 line we found an overall increase in Nectin-4 expression in tumors treated with a 5-day course of erdafitinib; (2) in a UPFL1 (a cell line derived from a genetically engineered mouse with a S249C mutation) syngeneic model we also saw an increase in Nectin-4 expression after erdafitinib treatment. We have observed that the increase in Nectin-4 expression persists in vitro even after withdrawal of erdafitinib treatment, indicating that intermittent dosing of erdafitinib maybe be sufficient to prime a tumor for Nectin-4 targeted therapy. Lastly, preliminary in vitro investigation of the combination of erdafitinib and enfortumab vedotin in RT112 cells showed synergy, particularly with lower doses of both agents, providing further support of our hypothesis that FGFR3 inhibition may act to sensitize UC to Nectin-4 ADC therapy. A potential synergistic relationship is further supported by the recent results of the phase 1 trial investigating the combination of erdafitinib plus enfortumab vedotin in which the objective response rate was 100% (9/9 patients: 8 PRs & 1CR). Citation Format: Sean Clark-Garvey, Mi Zhou, Michael Sturdivant, Wolfgang Beckabir, Lucia Kim, E. Drew Toomer, Ian McCabe, Akihiro Hamada, Daniel Crona, Jeffrey S. Damrauer, William Y. Kim. FGFR inhibition upregulates Nectin-4 expression in FGFR3 altered urothelial carcinoma [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr B014.

Abstract A014: PIK3CA mutation might confer resistance to an FGFR inhibitor, erdafitinib, in urothelial cancer cells

Abstract Objective: Metastatic urothelial carcinoma (mUC) has a poor prognosis. In the United States, an FGFR inhibitor (erdafitinib) was approved for mUC patients with FGFR2/3 alterations. Significantly, FGFR3 mutations are associated with favorable outcomes in UC but might also be associated with less sensitivity to immune checkpoint inhibitors, especially in metastatic upper tract UC (mUTUC). Therefore, erdafitinib can be an optimal candidate for mUTUC with FGFR3 mutations before treatment with immune checkpoint inhibitors. However, the duration of response for erdafitinib is limited in many patients. Hence, this study aimed to elucidate the resistance mechanism of erdafitinib and develop a new treatment for mUC. Methods: UC cell lines with FGFR3 alterations were exposed to erdafitinib for an extended period to create resistant cell lines. We assessed genetic modifications in the resistant lines. We also investigated the susceptibility to specific therapeutic agents for cancer-associated gene mutations in vitro and in vivo. [Results] Whole exome sequencing demonstrated PIK3CA gene mutations in two resistant lines. Significantly, a PI3K inhibitor showed apoptosis in resistant cells in vitro. Moreover, alpelisib showed a statistically significant growth inhibitory effect on erdafitinib-resistant UC tumors in vivo compared to control or erdafitinib treatment. Conclusions: PIK3CA gene mutations may be one of the resistant mechanisms to erdafitinib and can also be targetable with a commercially available PI3K inhibitor in mUC. Citation Format: Seiji Arai, Tatsuhiro Sawada, Akira Ohtsu, Mai Onose, Yuta Maeno, Yoshitaka Sekine, Kazuhiro Suzuki. PIK3CA mutation might confer resistance to an FGFR inhibitor, erdafitinib, in urothelial cancer cells [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr A014.

State-of-the-art and trends in fibroblast growth factor receptor-directed therapies in gastro-intestinal malignancies.

This review is timely and relevant due to the increasing recognition of the significance of the fibroblast growth factor receptor (FGFR) family in cancer biology. Understanding the role of FGFRs and their dysregulation in various cancers is crucial for developing targeted therapies and improving patient outcomes. The review highlights the importance of the FGFR family in cellular processes such as growth, proliferation, and survival. It discusses how abnormalities in FGFR2, including overexpression, gene amplification, and other genetic alterations, contribute to cancer progression, particularly in gastro-intestinal cancers. The paper also emphasizes the promising results of FGFR-targeted therapies, especially tyrosine kinase inhibitors, in certain cancers such as cholangiocarcinoma and oesophagogastric cancers. The findings underscore the potential of FGFR-targeted therapies in treating cancers with FGFR dysregulation. However, the review also addresses the challenges associated with these therapies, including toxicities and mechanisms of resistance. Understanding these complexities is essential for optimizing the efficacy of FGFR-targeted treatments and improving patient outcomes in clinical practice and research efforts.

Pemigatinib in previously treated solid tumors with activating FGFR1–FGFR3 alterations: phase 2 FIGHT-207 basket trial

Fibroblast growth factor receptor (FGFR) alterations drive oncogenesis in multiple tumor types. Here we studied pemigatinib, a selective, potent, oral FGFR1–FGFR3 inhibitor, in the phase 2 FIGHT-207 basket study of FGFR-altered advanced solid tumors. Primary end points were objective response rate (ORR) in cohorts A (fusions/rearrangements, n = 49) and B (activating non-kinase domain mutations, n = 32). Secondary end points were progression-free survival, duration of response and overall survival in cohorts A and B, and safety. Exploratory end points included ORR of cohort C (kinase domain mutations, potentially pathogenic variants of unknown significance, n = 26) and analysis of co-alterations associated with resistance and response. ORRs for cohorts A, B and C were 26.5% (13/49), 9.4% (3/32) and 3.8% (1/26), respectively. Tumors with no approved FGFR inhibitors or those with alterations not previously confirmed to be sensitive to FGFR inhibition had objective responses. In cohorts A and B, the median progression-free survival was 4.5 and 3.7 months, median duration of response was 7.8 and 6.9 months and median overall survival was 17.5 and 11.4 months, respectively. Safety was consistent with previous reports. The most common any-grade treatment-emergent adverse events were hyperphosphatemia (84%) and stomatitis (53%). TP53 co-mutations were associated with lack of response and BAP1 alterations with higher response rates. FGFR1–FGFR3 gatekeeper and molecular brake mutations led to acquired resistance. New therapeutic areas for FGFR inhibition and drug failure mechanisms were identified across tumor types. ClinicalTrials.gov identifier: NCT03822117.