FGFR3 activating mutations induce luminal-like papillary bladder tumor formation and favor a male gender bias.

Background FGFR3 mutations are among the most frequent genetic alterations in bladder cancer and are enriched in the luminal papillary subtype of muscle-invasive tumors (MIBC) and luminal-like classes 1 and 3 of non-MIBC. To study their oncogenic properties in vivo, we developed here a genetically engineered mouse (GEM) model expressing the most frequent FGFR3 mutation, FGFR3-S249C, in urothelial cells. Methods Bladder tumorigenesis was monitored in FGFR3-S249C mice. FGFR3 expression was assessed by RT-qPCR in the transgenic mice urothelium and in various human epithelia. Transcriptomic data were obtained from mouse bladder tumors and cross-species comparisons were performed. Sex bias in FGFR3-mutated tumors was evaluated in our GEM model and in the TCGA and UROMOL cohorts of patients including 408 MIBC and 419 NMIBC, respectively. The association of androgen receptor (AR) activity, based on the expression of its target genes, with FGFR3 mutations was examined in these two cohorts. The binding of AR to its response element and AR phosphorylation in FGFR3-dependent cell lines were evaluated. Results FGFR3-S249C expression in the urothelium of mice induced spontaneous low-grade papillary bladder tumors resembling the human counterpart at the histological and transcriptomic levels. Mutant-FGFR3 expression levels impacted tumor formation incidence in mice and mutant-FGFR3-driven human tumors were restricted to epithelia presenting high normal expression levels of FGFR3. The known bladder cancer male gender bias, also found in our model, was even higher in human FGFR3-mutated compared to wild-type tumors and associated with a higher AR regulon activity considering gender adjustment. AR phosphorylation and regulon activity were modulated by FGFR3 in FGFR3-dependent models. Conclusions Mutant-FGFR3 is an oncogene per se, inducing bladder tumorigenesis. Patients with early-stage bladder lesions could thus potentially benefit from FGFR3 targeting. Our results also reinforce the interest in elucidating the role of AR in bladder carcinogenesis, specifically in FGFR3-mutated driven tumors. Finally, our results suggest FGFR3 expression level in the epithelium as a determinant for the FGFR3-driven tumors tissue specificity.

Case Report: Anlotinib Combined With Sintilimab as Third-Line Treatment in a Metastatic Urothelial Bladder Carcinoma Patient With FGFR3 Mutation

We report on a case of metastatic urothelial bladder carcinoma (mUBC) treated with anlotinib combined with sintilimab. A 69-year-old male was diagnosed with non-muscle invasive bladder cancer (NMIBC). He received transurethral resection of bladder tumor (TURBT) and intravesical gemcitabine chemotherapy. After the patients’ cancer progressed to mUBC, cisplatin-based chemotherapy (gemcitabine combined with cisplatin, GC) was performed to this patient as first line therapy for four cycles. However, the disease progressed again within 6 months. Local radiotherapy was performed on the metastatic lesions, and after radiotherapy, the patient received anti-PD-1 antibody (sintilimab 200 mg, q3w)combined with Albumin-bound (Nab)-paclitaxel (100 mg, qw) as the second-line therapy, but the patient’s cancer was still observed to be progressing. Molecular characterization confirmed the presence of FGFR3 mutations in the patient. Anlotinib was recommended to this patient. After the patient was fully informed and he was aware of off-label use of the drug, then, Nab-paclitaxel was replaced by anlotinib (10 mg D1–14, q3w) and sintilimab infusions were maintained for every 3 weeks. Partial response (PR) was observed through imaging examinations and stable disease (SD) was observed for more than 11 months; the patient’s quality of life also improved. This case suggested that anlotinib combined with sintilimab may be a safe and effective choice in the treatment of mUBC in patients with FGFR3 mutations.

Targeted Therapy With PI3K and FGFR Inhibitors on Human Papillomavirus Positive and Negative Tonsillar and Base of Tongue Cancer Lines With and Without Corresponding Mutations

ObjectivesHuman papillomavirus positive (HPV+) tonsillar and base of tongue squamous cell carcinoma (TSCC/BOTSCC), the major subsites of oropharyngeal squamous cell carcinoma (OPSCC) have favorable outcome, but upon relapse, outcome is poor and new therapies needed. Since, phosphatidyl-inositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) and fibroblast-growth-factor-receptor-3 (FGFR3) mutations often occur in such tumors, here, we tested targeted therapy directed to such genes in TSCC/BOTSCC cell lines. We also combined the two types of inhibitors with each other, and cisplatin or docetaxel that are used clinically.MethodsThe HPV+ CU-OP-2, -3, -20, UPCI-SCC-154, and HPV- CU-OP-17 and UT-SCC-60A cell lines were first tested for common PIK3CA/FGFR3 mutations by competitive-allele-specific TaqMan-PCR. They were then treated with the food and drug administration (FDA) approved drugs, alpelisib (BYL719) and erdafitinib (JNJ-42756493) alone and in combination with cisplatin or docetaxel. Viability, proliferation, apoptosis and cytotoxicity responses were thereafter followed by WST-1 assays and the IncuCyte S3 Live® Cell Analysis System.ResultsHPV+ CU-OP-2 had a pS249C-FGFR3, and like CU-OP-20, a pE545K-PIK3CA mutation, while no other lines had such mutations. Irrespectively, dose dependent responses to all PI3K/FGFR inhibitors were obtained, and upon combining the inhibitors, positive effects were observed. Cisplatin and docetaxel also induced dose dependent responses, and upon combination with the inhibitors, both positive and neutral effects were found.ConclusionsThe data suggest that FDA approved drugs alpelisib and erdafitinib efficiently inhibit TSCC/BOTSCC cell line growth, especially when combined irrespective of presence of corresponding mutations and should be further explored, for use upon recurrent disease.

Enfortumab vedotin in FGFR3-mutated advanced urothelial carcinoma.

458 Background: Enfortumab vedotin (EV) and, for those with FGFR3 mutations (FGFR3+), erdafitinib, are established therapeutic options for refractory advanced urothelial carcinoma. However, optimal sequencing of these agents remains undefined. Here, we report our experience of EV monotherapy with focus on patients (pts) with FGFR3 alterations. Methods: Pts who were treated with EV were identified. Clinical data and outcomes were extracted. Tumor genomic profiles by the MSK-IMPACT assay as part of standard of care were reviewed for FGFR3 and other commonly altered gene mutations and tumor mutation burden (TMB). Progression-free (PFS) and overall survival (OS) were measured from start of EV therapy and compared with unadjusted log-rank test. Results: 89 patients received EV on completed monotherapy studies (n = 37) or as standard of care. Median age was 62 years (IQR: 62 – 78), 71% were male (n = 63), 28% had liver metastases. Distribution per Bellmunt score (0 – 3) was: 12%, 42%, 37% and 9%. For the entire population, PFS and OS were 5.2 and 11.4 months, respectively, with response rate of 52% among 75 evaluable patients. MSK-IMPACT was available for 80 patients. Overall genomic profile was similar to TCGA cohort except for fewer DNA damage response/repair gene alterations – 15% (ERCC2: 2; ATM: 4, BRCA1: 2, BRCA2: 3, RAD51C: 1) and FGFR3+ rate of 33%. Median TMB was 8.9/Mb (IQR: 5.2 – 13.3). Of the 26 FGFR3+ pts, 8 and 1 received an FGFR3 inhibitor (FGFR3i) before and after EV, respectively. 17 pts have not been exposed to FGFR3i; 13 of whom have progressed on EV and 9 died. Compared to FGFR3- pts, FGFR3+ pts with no prior FGFRi had significantly shorter median PFS on EV (2.5 vs. 6.8 months; HR 0.33 [0.14 – 0.80] p < .01) and trend towards shorter median OS (4.9 vs. 14.6 months; HR 0.42 [0.16 – 1.08] p > .05). PFS on EV among FGFR3+ pts with prior FGFR3i exposure was 6.7 months, similar to FGFR3- pts (HR 0.77 [0.30 – 1.96] p = .6). Response rates for FGFR3+ with and without prior FGFRi, and FGFR3- pts on EV were 4/7 (50%), 5/13 (38%) and 29/48 (60%). Conclusions: In this retrospective study, FGFR+ patients who receive EV first appear to have shorter PFS and lower ORR than those who have received prior FGFRi. Prospective studies on the sequence of EV and FGFR3i in FGFR3+ pts are warranted.