Lung squamous cell carcinoma (LUSC), a subset of non-small cell lung cancer (NSCLC), accounts for about 30% of all lung cancers (LC) and exhibits a dismal response to current therapeutic protocols. Existed studies have indicated that aberrations in fibroblast growth factor receptors (FGFRs) play a pivotal role in the progression of LUSC, rendering them as attractive targets for therapeutic intervention in this cancer type. This study found that Erdafitinib (Erda), a novel pan-FGF receptor tyrosine kinase inhibitor (TKI), exerted a cytotoxic effect on LUSC cells. However, STAT3, the downstream target of FGFRs, remained still activated despite Erdafitinib treatment. Then, a STAT3 inhibitor, Stattic (Sta), was concurrently used with Erdafitinib, and the combined treatment demonstrated a synergistic efficacy in both in vitro and in vivo models of LUSC when compared to that of the treatment of the Erdafitinib or Stattic alone. Further molecular studies showed that such an effect of Erdafitinib and Stattic was associated with their concurrently inhibitory effect on FGFR1 and STAT3 signaling in LUSC cells. Therefore, the findings of this study indicated that the concurrent use of Erdafitinib and Stattic is a promising therapeutic approach for the treatment of FGFR1-positive LUSC.

FGFR3-TACC3 fusion-positive IDH-wild-type (IDH-WT) glioblastoma (GB) is a rare GB subtype occurring in approximately 3% of cases. It is clinical behavior and molecular profile is different from those of fusion-negative IDH-WT GBs. Evidence on the role of FGFR inhibitors in FGFR-altered gliomas is limited. We present the case of a patient with a FGFR3-TACC3 fusion-positive IDH-WT GB that at its second recurrence was treated with the FGFR inhibitor erdafitinib through a compassionate use program. Although no objective response was achieved, an overt deceleration in tumor growth was evidenced and the patient remained on treatment for 5.5 months.

In this review, we revisit the pivotal role of fibroblast growth factor receptor 3 (FGFR3) in bladder cancer (BLCA), underscoring its prevalence in both non-muscle-invasive and muscle-invasive forms of the disease. FGFR3 mutations in up to half of BLCAs play a well-established role in tumorigenesis, shaping distinct tumor initiation patterns and impacting the tumor microenvironment (TME). Emphasizing the importance of considering epithelial-mesenchymal transition profile and TME status, we revisit their relevance in predicting responses to immune checkpoint inhibitors in FGFR3-mutated BLCAs. This writing highlights the initially promising yet transient efficacy of the FGFR inhibitor Erdafitinib on FGFR3-mutated BLCA, stressing the pressing need to unravel resistance mechanisms and identify co-targets for future combinatorial studies. A thorough analysis of recent preclinical and clinical evidence reveals resistance mechanisms, including secondary mutations, epigenetic alterations in pathway effectors, phenotypic heterogeneity, and population-specific variations within FGFR3 mutational status. Lastly, we discuss the potential of combinatorial treatments and concepts like synthetic lethality for discovering more effective targeted therapies against FGFR3-mutated BLCA.

BACKGROUND: FGFR genomic aberrations occur in approximately 5-10% of human cancers. Erdafitinib has previously demonstrated efficacy and safety in FGFR-altered advanced solid tumors, such as gliomas, thoracic, gastrointestinal, gynecological, and other rare cancers. However, its efficacy and safety in Asian patients remain largely unknown. We conducted a multicenter, open-label, single-arm phase IIa study of erdafitinib to evaluate its efficacy in Asian patients with FGFR-altered advanced cholangiocarcinoma, non-small cell lung cancer (NSCLC), and esophageal cancer.
METHODS: Patients with pathologically/cytologically confirmed, advanced, or refractory tumors who met molecular and study eligibility criteria received oral erdafitinib 8 mg once daily with an option for pharmacodynamically guided up-titration to 9 mg on a 28-day cycle, except for four NSCLC patients who received erdafitinib 10 mg (7 days on/7 days off) as they were recruited before the protocol amendment. The primary endpoint was investigator-assessed objective response rate per RECIST v1.1. Secondary endpoints included progression-free survival, duration of response, disease control rate, overall survival, safety, and pharmacokinetics.
RESULTS: Thirty-five patients (cholangiocarcinoma: 22; NSCLC: 12; esophageal cancer: 1) were enrolled. At data cutoff (November 19, 2021), the objective response rate for patients with cholangiocarcinoma was 40.9% (95% CI, 20.7-63.6); the median progression-free survival was 5.6 months (95% CI, 3.6-12.7) and median overall survival was 40.2 months (95% CI, 12.4-not estimable). No patient with RET/FGFR-altered NSCLC achieved objective response and the disease control rate was 25.0% (95% CI, 5.5-57.2%), with three patients with stable disease. The single patient with esophageal cancer achieved partial response. All patients experienced treatment-emergent adverse events, and grade ≥ 3 treatment-emergent adverse events were reported in 22 (62.9%) patients. Hyperphosphatemia was the most frequently reported treatment-emergent adverse event (all-grade, 85.7%).
CONCLUSIONS: Erdafitinib demonstrated efficacy in a population of Asian patients in selected advanced solid tumors, particularly in those with advanced FGFR-altered cholangiocarcinoma. Treatment was tolerable with no new safety signals.
BACKGROUND: This trial is registered with ClinicalTrials.gov (NCT02699606); study registration (first posted): 04/03/2016.

BACKGROUND: Growth acceleration during postnatal growth only occurs during puberty as a physiological event and during catch-up growth mediated by growth-promoting therapies in growth disorders. Here we report on novel observations of skeletal symptoms during treatment with erdafitinib, a tyrosine kinase inhibitor (TKI) prescribed on the basis of a compassionate-use program.
METHODS: Analysis of anthropometric, biochemical, clinical, and radiographic data of patients with CNS tumors who revealed an unanticipated growth spurt with initiation of therapy with erdafitinib was performed retrospectively.
RESULTS: Linear growth acceleration was independent of sex steroids and IGF1 levels, which is especially remarkable in the context of heavily pretreated pediatric neuro-oncology patients with severe growth impairment before initiation of therapy. Growth acceleration was accompanied by a distinct widening of the growth plate and enhanced metaphyseal mineralization shortly after the start of TKI therapy.
CONCLUSIONS: While targeted therapies including TKIs have become an essential part of adult cancer treatment, applications in children are still limited. Off-target effects specific to the pediatric population have been observed in various organ systems; however, knowledge about the effect of TKIs on the growing skeleton is scarce. Treatment with erdafitinib inhibits FGFR3-mediated effects and thus represents a very logical hypothetical framework of growth factor and sex steroid-independent growth acceleration.

Erdafitinib, an oral pan-FGFR inhibitor, is used in locally advanced or metastatic urothelial carcinoma for adults with FGFR3 genetic alterations and whose disease progressed following prior systemic therapy. This drug-drug interaction substudy evaluated the effect of erdafitinib on the pharmacokinetics of midazolam (cytochrome P450 3A4 substrate), and metformin (organic cation transporter 2 substrate). Twenty-five patients with advanced solid tumors harboring FGFR gene alterations received pretreatment with single doses of midazolam and metformin, followed by a daily dose of erdafitinib. Drug-drug interaction assessments were performed at erdafitinib steady state following coadministration of single doses of midazolam and metformin, respectively. Geometric mean ratios for maximum plasma concentration and area under the plasma concentration-time curve (AUC) from time 0 to the last measurable concentration, and AUC from time 0 to infinity were estimated using linear mixed-effects models (90% confidence interval within 80%-125% indicated no interaction). The 90% confidence intervals of geometric mean ratios for maximum plasma concentration, AUC from time 0 to the last measurable concentration, and AUC from time 0 to infinity of midazolam (86.3%, 88.5%, and 82.1%), 1-OH midazolam (99.8%, 97.4%, and 101.5%), and metformin (108.7%, 119.0%, and 113.9%) were either contained or slightly outside the 80%-125% interval and not considered clinically meaningful. Adverse events were consistent with the known erdafitinib safety profile; no new safety signals emerged. Thus, repeated dosing of erdafitinib had no clinically meaningful effect on the pharmacokinetics of midazolam or metformin.

BACKGROUND: In the THOR trial (NCT03390504) Cohort 1, erdafitinib demonstrated significantly prolonged overall survival (OS) (median 12.1 versus 7.8 months) and reduced risk of death by 36% (hazard ratio 0.64, P = 0.005) compared with chemotherapy in metastatic urothelial carcinoma (mUC) patients with FGFR alterations who progressed after ≥ 1 prior treatments, including anti-PD-(L)1. There have been no reports of the Japanese subgroup results yet.
METHODS: THOR Cohort 1 randomized patients to erdafitinib once daily or docetaxel/vinflunine once every 3 weeks. Primary endpoint was OS. Secondary endpoints included progression-free survival (PFS) and objective response rate (ORR). No specific statistical power was set for this Japanese subgroup analysis.
RESULTS: Of 266 patients randomized, 27 (14 erdafitinib; 13 chemotherapy) were Japanese. Baseline characteristics were generally similar between treatments and to the overall population, except for more males, lower body weight, and more upper tract primary tumors among Japanese patients. Compared with chemotherapy, erdafitinib showed improved OS (median 25.4 versus 12.4 months), PFS (median 8.4 versus 2.9 months) and ORR (57.1% versus 15.4%). Any grade treatment-related adverse events (AEs) occurred in all patients from both arms but Grade 3/4 AEs and AEs leading to discontinuation were lower in the erdafitinib arm. No new safety signals were observed in the Japanese subgroup.
CONCLUSIONS: In the Japanese subgroup, erdafitinib showed improved survival and response compared to chemotherapy, with no new safety concerns. These results support erdafitinib as a treatment option for Japanese mUC patients with FGFR alterations, and early FGFR testing after diagnosis of mUC should be considered.

Uveal melanoma (UM) is a rare yet lethal primary intraocular malignancy affecting adults. Analysis of data from The Cancer Genome Atlas (TCGA) database revealed that FGFR1 expression was increased in UM tumor tissues and was linked to aggressive behavior and a poor prognosis. This study assessed the anti-tumor effects of Erdafitinib, a selective pan-FGFR inhibitor, in both in vitro and in vivo UM models. Erdafitinib exhibited a robust anti-cancer activity in UM through inducing ferroptosis in the FGFR1-dependent manner. Transcriptomic data revealed that Erdafitinib mediated its anti-cancer effects via modulating the ferritinophagy/lysosome biogenesis. Subsequent research revealed that Erdafitinib exerted its effects by reducing the expression of FGFR1 and inhibiting the activity of mTORC1 in UM cells. Concurrently, it enhanced the dephosphorylation, nuclear translocation, and transcriptional activity of TFEB. The aggregation of TFEB in nucleus triggered FTH1-dependent ferritinophagy, leading to lysosomal activation and iron overload. Conversely, the overexpression of FGFR1 served to mitigate the effects of Erdafitinib on ferritinophagy, lysosome biogenesis, and the activation of the mTORC1/TFEB signaling pathway. In vivo experiments have convincingly shown that Erdafitinib markedly curtails tumor growth in an UM xenograft mouse model, an effect that is closely correlated with a decrease in FGFR1 expression levels. The present study is the first to demonstrate that Erdafitinib powerfully induces ferroptosis in UM by orchestrating the ferritinophagy and lysosome biogenesis via modulating the FGFR1/mTORC1/TFEB signaling. Consequently, Erdafitinib emerges as a strong candidate for clinical trial investigation, and FGFR1 emerges as a novel and promising therapeutic target in the treatment of UM.

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.

UNASSIGNED: A case of bilateral multifocal serous retinal detachments and dry eye complicated with unilateral peripheral ulcerative keratitis (PUK) during erdafitinib therapy is described.
UNASSIGNED: A 76-year-old male underwent a baseline examination two months after initiating 8 mg erdafitinib therapy (April 2023) due to metastatic urothelial carcinoma. Left subfoveal serous retinal detachment was observed initially but the treatment was resumed as he was asymptomatic. In May 2023, bilateral multifocal subretinal fluid pockets were identified, and the patient was still asymptomatic. However, in June 2023 he complained of bilateral redness and a stinging sensation in his right eye. Bilateral severe dry eye and right PUK were diagnosed. He was prescribed dexamethasone eye drops and sodium hyaluronate artificial tears for both eyes. One week later corneal staining decreased, and progression of PUK ceased. Erdafitinib therapy was discontinued in June 2023 due to the planned transurethral prostatectomy. By July 2023, after discontinuation of the drug and administration of the topical treatment, the dry eye improved and the PUK became inactive. There was also resolution of subretinal fluid pockets in the right eye and a reduction of subretinal fluid pockets in the left eye. After the reinitiation of erdafitinib therapy, serous retinal detachments recurred in both eyes in September 2023, but both corneas remained stable with topical low-dose dexamethasone, cyclosporine-A and artificial tear usage.
UNASSIGNED: Erdafitinib therapy may lead to concurrent anterior and posterior segment complications. Multidisciplinary monitoring is crucial for patients undergoing erdafitinib therapy to prevent possible visual disturbances.
CONCLUSIONS: Erdafitinib, a tyrosine kinase inhibitor of fibroblast growth factor receptors 1 to 4, is administered for the treatment of locally advanced, unresectable or metastatic urothelial carcinoma but however is fraught with several systemic and ocular side effects.Concurrent anterior and posterior segment ocular involvement could be encountered in patients undergoing erdafitinib therapy.Maintaining a high level of suspicion and closely monitoring for potential ocular complications through collaborative efforts is essential for all patients undergoing erdafitinib therapy.