Bellmunt, Joaquim

4540 Background: Patients w/ locally advanced or metastatic urothelial carcinoma (UCC) have a poor prognosis. Prior to atezolizumab’s approval, there were no approved treatments (txs) for pts who progressed after chemotherapy. Even w/ immune checkpoint inhibitors, most pts require additional txs. FGFR3 is frequently overexpressed in UCC and 15-20% of pts w/ advanced disease have tumors w/ FGFR3 gene mutations or fusions. B-701 (formerly R3Mab) is a fully human monoclonal antibody against FGFR3 that blocks activation of the wildtype and genetically activated receptor. NCT02401542 is a phase (ph) 1b/2 study designed to evaluate the safety and efficacy of B-701 plus docetaxel (D) in advanced UCC pts. Methods: The study has a lead-in (n=20 pts) and a randomized ph (n=201). Eligible pts: Stage IV UCC, relapsed/refractory to 1 or 2 prior chemotherapy regimens not including taxanes with ECOG 0-1. Txs: B-701 at 25 mg/kg q3w (+ loading dose on C1D8) and D at 75 mg/m2 q3w. Efficacy assessed by RECIST 1.1. Primary obj: PFS and safety. Secondary obj: overall response rate (ORR); duration of response (DOR); disease control rate (DCR); overall survival (OS). Exploratory obj: association of FGFR3 status w/ efficacy and AEs. Results: As of 20 Jan 2017, 19 pts enrolled to lead-in ph w/median age 66 yrs, ECOG 1 58%, Hgb <10 gm/dL 5%, liver mets 26% and ≥ 2 prior regimens 63%. 17 evaluable for PFS/ORR. 5 pts w/ FGFR3 mut or TACC3-fus. Gr ≥3 AEs occurring in ≥2 pts: decreased neutrophils (26.3%), neutropenia (10.5%), decreased WBCs (10.5%). 2 pts had D dose reductions and 1 pt discontinued tx due to AE (disseminated intravascular coagulation). Conclusions: Preliminary results show that B-701 combines safely and effectively with D in UCC, with the combination being well tolerated and showing promising ORR and PFS in pts w/ FGFR3 mut/fus. The protocol has been amended to add Cohorts 2 (B-701+D) and 3 (B-701) (n=20 pts/cohort) for pts w/ FGFR3 mut/fus+ tumors only. Clinical trial information: NCT02401542. [Table: see text]

422 Background: There is significant variability in the response to VEGF-TT in mRCC with no validated predictive biomarkers. We hypothesized that whole exome analysis might identify markers of response and resistance to VEGF-TT in mRCC. Methods: mRCC patients who received first-line sunitinib or pazopanib and were in two extreme phenotypes of response were identified. Extreme responders (ER) were defined as PR or CR for ≥3 years (n=10) and primary refractory patients (PRP) were defined as PD within the first 3 months of therapy (n=10). WES was performed in pre-treatment specimens and established Broad Institute analytical pipelines were utilized to identify point mutations and copy number alterations across the exome. ER (n=4) and PRP (n=4) who were part of TCGA project for clear-cell RCC were included in this analysis. Nonsense, missense and indel mutations in established or novel RCC genes were investigated. Results: IMDC prognostic scores were not significantly different between the two groups. VHL mutations were observed at similar frequency in ER and PRP, overall 57%. Mutations in PBRM1 were identified in 7 ER (50%) vs. 1 PRP (7%) (p=0.03). In addition, mutations in TP53 were only found in PRP (p=0.09). No other gene had mutations that were associated with either response or primary refractory disease (Table). Conclusions: In this pilot study, PBRM1 mutations were associated with extreme response to VEGF-TT. However, this was exploratory, and multivariable analysis was not performed. Analysis of additional patient samples is ongoing to confirm or refute this association. If true it suggests that epigenetic effects of PBRM1 mutation may contribute to response to VEGF-TT in mRCC. [Table: see text]

Abstract Purpose: We examined the hypothesis that mutations in mTOR pathway genes are associated with response to rapalogs in metastatic renal cell carcinoma (mRCC). Experimental Design: We studied a cohort of mRCC patients who were treated with mTOR inhibitors with distinct clinical outcomes. Tumor DNA from 79 subjects was successfully analyzed for mutations using targeted next-generation sequencing of 560 cancer genes. Responders were defined as those with partial response (PR) by RECIST v1.0 or stable disease with any tumor shrinkage for 6 months or longer. Nonresponders were defined as those with disease progression during the first 3 months of therapy. Fisher exact test assessed the association between mutation status in mTOR pathway genes and treatment response. Results: Mutations in MTOR, TSC1, or TSC2 were more common in responders, 12 (28%) of 43, than nonresponders, 4 (11%) of 36 (P = 0.06). Mutations in TSC1 or TSC2 alone were also more common in responders, 9 (21%), than nonresponders, 2(6%), (P = 0.05). Furthermore, 5 (42%) of 12 subjects with PR had mutations in MTOR, TSC1, or TSC2 compared with 4 (11%) of 36 nonresponders (P = 0.03). Eight additional non-mTOR pathway genes were found to be mutated in at least 4 of 79 tumors (5%); none were associated positively with response. Conclusions: In this cohort of mRCC patients, mutations in MTOR, TSC1, or TSC2 were more common in patients who experienced clinical benefit from rapalogs than in those who progressed. However, a substantial fraction of responders (24 of 43, 56%) had no mTOR pathway mutation identified. Clin Cancer Res; 22(10); 2445–52. ©2016 AACR. See related commentary by Voss and Hsieh, p. 2320