Hennessy, Katie

566 Background: FGFR inhibitors (FGFRi) have an established role in treating FGFR2-altered (alt) cholangiocarcinoma (CCA). Tinengotinib, a novel FGFRi, has shown promising activity overcoming acquired resistance to prior FGFRi. We present biomarker analyses evaluating tinengotinib’s ability to overcome prior FGFRi resistance and to elucidate mechanism of resistance to tinengotinib. Methods: Eligible patients (pts) with advanced/metastatic CCA who had received ≥ 1 prior systemic chemotherapy were treated with tinengotinib 10 mg daily across 4 Cohorts: A1: FGFR2 fusion (fus) with primary progressive disease (PD) on prior FGFRi; A2: FGFR2 fus with PD after prior response to FGFRi; B: FGFR alt without FGFR2 fus; C: FGFR wild-type. Efficacy was assessed by RECIST v1.1. All pts underwent liquid biopsy for circulating tumor DNA (ctDNA) at baseline; additional timepoints include cycle 3 day 1 (C3D1), time of PD, and end of treatment (EOT). Samples were analyzed using FoundationOne Liquid panel. Results: 27 out of 55 enrolled pts had biomarker samples collected at baseline and C3D1. Among them, pts in A1 (n=10, 107 mutations (mut)), B (n=8, 90 mut) and C (n=5, 74 mut) showed a significant decrease in short variant allele frequencies (VAF) from baseline to C3D1 by a median relative VAF reduction of 100% (p<0.0001) for each of the three cohorts. Although a median relative VAF reduction of 33.3% was seen in A2 (n=4, 15 mut), this was not significant (p=0.6093) likely due to low baseline mutation burden. A ≥50% reduction in ctDNA was associated with improved progression free survival (p<0.0014). Additionally, 100% of median relative reductions in FGFR2 kinase domain (KD) mut were seen in A1 and B (p<0.0001, 95% CI 100-100% and p=0.0156, 95% CI 83.6-100%, respectively), with 92% and 57% clearance of initial FGFR2 KD mut by C3D1. In a subgroup of 10 pts with biomarker sampling at baseline and EOT, 3 pts in A1 with acquired resistance showed emergence of novel FGFR2 mut, loss of FGFR-sensitive mut and new mut in alternate pathways (e.g., AKT, EGFR, RAS/MAPK) while retaining the original FGFR2 fus. 1 pt from B developed resistance due to new FGFR2 rearrangements and FGFR2 mut. 4 FGFR wild-type pts from C developed resistance involving mut in TP53, KRAS, and other oncogenic drivers. Conclusions: These findings provide genomic evidence that tinengotinib may overcome resistance to prior FGFRi treatment in FGFR2 fus-positive CCA, as reflected by significantly reductions in ctDNA VAFs and frequent clearance of FGFR2 KD mutations. The emergence of resistance alterations including de novo FGFR2 mutations and bypass pathways activations indicates acquired resistance that may limit long-term benefit. These results support further investigation with expanded biomarker sampling to better characterize resistance evolution and guide therapy optimization in an ongoing Phase 3 trial. Clinical trial information: NCT04919642 .

608 Background: Tinengotinib, a spectrum-selective multi-kinase inhibitor with unique binding properties to FGFR , potently inhibited FGFR2 fusion/rearrangement and acquired resistant/gatekeeper mutations in pre-clinical models and exhibited antitumor activity in cholangiocarcinoma (CCA) patients (pts) in phase 1/2 trials. Here we present the overall survival (OS) data and biomarker correlative analysis from a phase 2 clinical trial of tinengotinib in CCA. Methods: Eligible pts with advanced/metastatic CCA who had received ≥ 1 prior systemic chemotherapy with ECOG PS 0-1 were treated with tinengotinib 10 mg QD across four Cohorts: A1: FGFR2 fusion(s) with primary progression on previous FGFR inhibitor ( FGFR i); A2: FGFR2 fusion(s) with progression after prior response to FGFR i; B: FGFR alteration(s) without FGFR2 fusion(s); C: FGFR wild-type. Efficacy was evaluated per RECIST v1.1 and safety was assessed by CTCAE v5.0. Genomic alterations in circulating tumor DNA (ctDNA) were assessed by Foundation Medicine NGS panel at baseline, C3D1 and EOT. Planned correlative analyses of response (PR+SD>6 months) and PFS in pt subgroups based on ctDNA mutational status were performed. Results: 55 eligible pts were enrolled (18 in A1, 11 in A2, 13 in B, 13 in C) with median age 61.0 [range 24-81] years, ECOG PS 0 in 50.9% pts, 56.4% female, and 60.0% with ≥ 3 lines of prior therapy. Among 42 pts with FGFR alterations, 78.4% had ≥ 1 prior FGFR i, and 97.6% had prior chemotherapy. Median follow up time was 8.6 months (0.4-30.5). The median OS (months) was 17.1 (95%CI 7.5-19.5) in A1; not reached (95%CI 9.6, -) in A2; 18.0 (95%CI 9.6, -) in A1+A2; not reached (95%CI 8.0, -) in B; 6.5 (95%CI 4.8-16.4) in C. The OS rate in A, B and C was 100%, 91.7% and 75% at month 3; 83.7%, 83.3% and 66.7% at month 6, and 65.8%, 55.6% and 23.8% at month 12. Partial response was observed in 26% (10/39) of evaluable FGFR-altered pts (A1+A2+B). The safety profile was consistent with previous reports. The most common any-grade treatment-related AEs were hypertension (63.6%) and diarrhea (47.3%). Baseline ctDNA results were available in 46 pts, 35 in cohorts A+B and 11 in C. A positive correlation was shown in MED12 mutation vs response (P=0.03476). BCOR and ARID1A mutation were found to be negatively associated with PFS (P=0.01366 and P=0.0437). Acquired/secondary mutations at baseline were observed in cohort A, including V564F/I (3/24 and 5/24) and N549K/H (5/24 and 5/24); favorable anti-tumor activity was noted despite these resistant mutations, consistent with preclinical data. Conclusions: Tinengotinib has shown promising anti-tumor efficacy in CCA pts with FGFR fusion after prior FGFR i and in those with primary FGFR mutations. An ongoing randomized phase III study will investigate tinengotinib vs. chemotherapy in FGFR inhibitor refractory CCA (NCT05948475). Clinical trial information: NCT04919642 .

434 Background: Tinengotinib is a spectrum-selective multi-kinase inhibitor with unique binding properties to FGFR, potently inhibited FGFR2 fusion/rearrangement and acquired resistant mutations in pre-clinical models and in phase I trials that included cholangiocarcinoma (CCA) patients (pts). Here we present the efficacy and safety of tinengotinib in a phase II clinical trial. Methods: Eligible pts with advanced/metastatic CCA who had received ≥ 1 prior systemic chemotherapy therapy and ECOG PS 0 or 1 were treated with tinengotinib 10 mg QD. Four cohorts included: Cohort A1: FGFR2 fusion(s) with primary progression on previous FGFR inhibitor ( FGFRi), A2: FGFR2 fusion(s) with progression after prior response to FGFRi (acquired resistance); B: non-fusion FGFR alteration(s): C: FGFR wild-type ( FGFRwt). Primary endpoint was objective response rate (ORR) per RECIST v1.1. CTCAE V5.0 was used for safety assessments. Results: As of 7Aug2023, 48 pts with CCA were enrolled, 13 in Cohort A1, 10 in A2, 12 in B, 13 in C. Median age 61.5 [range 25-81] years old, 41.7% male, 58.3% had ≥ 3 lines of prior therapy. ECOG PS 0 in 47.9% pts. Among 35 pts with FGFR alterations, 80.0% had ≥ 1 prior FGFRi therapy, and 97.1% had prior chemotherapy. Forty (40) pts were efficacy evaluable. In A1, 1 out of 11 pts (9.1%) achieved PR with tumor reduction of 31.8%. In A2, 3 out of 8 pts (37.5%) achieved PR with tumor reduction of 40.7%, 47.0% and 54.6%. In B, 3 out of 9 pts (33.3%) achieved PR with tumor reduction of 36.5%, 48.6%, and 60.6%. No PR was observed in C. Overall DCR was 94.7% (18/19) in FGFR2 fusion/rearrangement pts (A1+A2), 88.9% (8/9) in other FGFR alterations pts (B), and 75% (9/12) in FGFRwt pts (C). Median progression-free survival (mPFS) was 5.26 months (95%CI, 2.86-9.10) in A1+A2, 5.98 months (95%CI, 1.87-NA) in B and 3.84 months (95% CI, 1.84-4.80) in C. Among 48 treated pts, treatment-related AEs (TRAEs) occurred in 45 (93.8%) pts, 14 (29.2%) in G1-2, 29 (60.4%) in G3 and 2 (4.2%) in G4. The most common G3 TRAEs were hypertension in 12 (25%), palmar-plantar erythrodysesthesia syndrome in 3 (6.3%), diarrhea in 3 (6.3%) and stomatitis in 3 (6.3%). One subject had G4 increased TSH and G4 increased lipase, and another subject had G4 posterior reversible encephalopathy syndrome. No G5 TRAE was observed. Conclusions: Tinengotinib has promising clinical benefit for FGFR2 fusion CCA after prior FGFRi and for non-fusion FGFR alterations. Tinengotinib-related toxicities were manageable. An ongoing randomized, controlled phase III study will evaluate the clinical efficacy, safety, and pharmacodynamic effect of Tinengotinib vs Physicians’ choice in subjects with FGFR2-altered refractory/relapsed CCA after prior chemotherapy and FGFRi therapy. Clinical trial information: NCT04919642 .