Lee, Keun‐Wook

380 Background: KRAS amplifications (amp) occur in ~2% of solid tumors, representing a high unmet need for effective targeted therapies. BI3706674 binds to GDP-bound KRAS and locks KRAS protein in an inactive form. In preclinical models, BI3706674 has shown potent inhibition of KRAS-amp tumors. Methods: This is a Phase Ia/b trial (NCT06056024) to explore the safety, pharmacokinetics (PK), pharmacodynamics (PD) and efficacy of BI 3706674 in patients (pts) with unresectable or metastatic KRAS wild type amp or KRAS G12V mutated (mut) solid tumors. The trial aimed to define the maximum tolerated dose (MTD). Pts (ECOG 0 -1) received BI 3706674 daily per os at 50 - 1200 mg doses. Dose escalation (DE) was guided by a Bayesian logistic regression model. This report focuses on KRAS wt amp pts from Phase Ia (DE). Results: As of 31 July 2025, 46 pts had received BI 3706674. Pts (n=15/46) with KRAS wt amp tumors had upper gastrointestinal tract (uGI) cancer [n=9: gastric (GAC;n=5), oesophageal (EAC; n=2), gastroesophageal junction (GEJC; n=2) cancers], Cholangiocarcinoma (n=1), colorectal (CRC; n=4), and ovarian (OC; n=1) cancers. Pts were treated at 200 mg (n=2), 400 mg (n=1), 800 mg (n=5), 1200 mg (n=7) doses; males: n=11; ECOG 1: n=10; median age - 62 years (range 38–83); median number of prior treatment lines was 3 (range 1-6). AEs were reported in 15 pts (100%), including 12 pts (80%) with treatment-related AEs (TRAE). High-grade AEs (Grade 3-5) were reported in 10 pts (66.7%), including 4 pts (26.7%) with TRAEs. SAEs were reported in 7 pts (46.7%), including 2 pts (13.3%) with TRAEs. The most-frequent AEs were mostly low-grade (Grade 1-2) diarrhoea (10 pts, 66.7%), nausea (10 pts, 66.7%), and vomiting (9 pts, 60.0%), often reported as TRAE. Two dose limiting toxicities were observed in 1200 mg group: nausea (Grade 3) and vomiting (Grade 3). MTD was not reached. BI 3706674 PK parameters followed the predicted non-linear PK model; dose dependent systemic exposure reached plateau at 800 mg. 12/15 pts with KRAS wt amp tumors, including 10/12 pts in 800 – 1200 mg groups, were efficacy evaluable; Disease control rate (DCR) was 58.3% (7/12 pts): 3/ 12 pts with partial response (PR), 4/12 had stable disease (SD), 5/12 pts - disease progression (PD). In 800 – 1200 mg groups 1 - OC, 2 – CRC pts achieved SD. PK/PD/efficacy correlation data is pending. Conclusions: BI 3706674 showed a tolerable safety profile and clinical efficacy in pts with KRAS amp tumors. Study results provide clinical proof of concept. KRAS wt amp is a druggable target and KRAS-targeting treatment is active in KRAS wt amp uGI cancer pts. Clinical trial information: NCT06056024 . Anticancer activity of BI 3706674 in efficacy evaluable pts with KRAS wt amp tumors. All pts, 200 – 1200 mg, N=12 Pts with uGI cancers,800 – 1200mg, N=7 ORR, n (%) 3* (25%) 3* (43%) SD, n (%) 4 (33.3%) 1 (14%) DCR, n (%) 7 (58.3%) 4 (57%) PD, n (%) 5 (41.7%) 3 (43%) *Tumor shrinkage: -60.3%, -34% and 34.3%.

158 Background: PIK3CA mutations are common in CRC and may be a negative prognostic factor. INAVO is a potent and selective PI3Kα inhibitor that also promotes mut p110α degradation. BEV and CETUX are standard treatment (tx) components for RAS mut and RAS -wildtype (wt) mCRC, respectively. The Phase I/Ib INTRINSIC open-label umbrella study (NCT04929223) evaluates targeted therapies in biomarker-selected mCRC subpopulations. We report INAVO + BEV and INAVO + CETUX results. Methods: Patients (pts) with PIK3CA mut, RAS mut mCRC received INAVO (9 mg oral once daily) + BEV (intravenous [IV] 15 mg/kg every 3 weeks). Pts with PIK3CA mut, RAS wt mCRC received INAVO + CETUX (IV 400 mg/m 2 then 250 mg/m 2 weekly thereafter). Primary endpoint: confirmed objective response rate (cORR). Secondary endpoints included disease control rate (DCR), duration of response (DoR), and safety. Progression-free survival (PFS) and overall survival (OS) were exploratory. Results: At the clinical cut-off dates, 16 pts were enrolled in the BEV arm; 35, in the CETUX arm. Most had ≥2 metastatic sites at enrollment (n = 16 [100%] and 30 [85.8%], respectively) and ≥2 prior lines of metastatic therapy (16 [100%] and 28 [80.0%]). In the BEV arm, 3 pts (18.8%) had no prior BEV. In the CETUX arm, 25 pts (71.4%) had no prior CETUX; 17 (48.6%) had prior anti-EGFR therapy. All pts in the BEV arm and 34 in the CETUX arm were evaluated for efficacy and safety. Median follow-up was 9.4 months (mo; interquartile range: 5.5–14.4) and 12.6 mo (8.9–16.6), respectively. Efficacy is shown in the Table. All pts had adverse events (AEs); 15 (93.8%) and 34 (100%), respectively, had tx-related AEs (TRAEs); 5 (31.2%) and 12 (35.3%), grade 3–4 TRAEs; 2 (12.5%) and 11 (32.4%), serious AEs. One grade 5 AE (infusion-related reaction) occurred (CETUX arm). Dose reduction/interruption due to AEs occurred in 12 (75.0%) and 27 (79.4%) pts; tx withdrawal due to AEs, in 0 and 4 (11.8%) pts, respectively. Hyperglycemia was the most common AE, TRAE, and AE leading to dose reduction/interruption in both cohorts. Hypertension was observed more frequently with BEV; dermatitis acneiform and dry skin, with CETUX. Conclusions: INAVO + BEV and INAVO + CETUX showed encouraging efficacy in pts with PIK3CA mut mCRC, with no new or unexpected safety signals. Clinical trial information: NCT04929223 . INAVO + BEV(n = 16) INAVO + CETUX(n = 34) cORR, all PR, n (%) 1 (6.3) 7 (20.6)* SD, n (%) 10 (62.5) 17 (50.0) Progressive disease, n (%) 3 (18.8) 9 (26.5) Missing/NE, n (%) 2 (12.5) 1 (2.9) mDoR, mo (90% CI) 7.7 (NE) 4.4 (4.2–5.3) DCR, n (%) 11 (68.8) 15 (44.1) mPFS, mo (90% CI) 4.2 (2.8–6.8) 3.5 (2.8–4.4) mOS, mo (90% CI) 11.0 (8.5–14.5) 12.8 (10.7–13.8) CI, confidence interval; m, median; NE, not evaluable; PR, partial response; SD, stable disease. *3 pts with PRs received prior anti-EGFR therapy; 1 had a best prior response of SD (last dose 233 days before study tx) and 2 had best prior responses of PRs (last doses 134 and 171 days before study tx).

PURPOSE To evaluate the efficacy and safety of tucatinib and trastuzumab in patients with previously treated human epidermal growth factor receptor 2–positive (HER2+) metastatic biliary tract cancer (mBTC). METHODS SGNTUC-019 (ClinicalTrials.gov identifier: NCT04579380 ) is an open-label phase II basket study evaluating the efficacy and safety of tucatinib and trastuzumab in patients with HER2-altered solid tumors. In the biliary tract cancer cohort, patients had previously treated HER2 overexpressing or amplified (HER2+) tumors (identified with local testing) with no prior HER2-directed therapy. The primary end point was confirmed objective response rate (cORR) per investigator assessment. Patients were treated on a 21-day cycle with tucatinib (300 mg orally twice daily) and trastuzumab (8 mg/kg intravenously followed by 6 mg/kg every 3 weeks). RESULTS Thirty patients were enrolled. As of data cutoff (January 30, 2023), the median duration of follow-up was 10.8 months. The cORR was 46.7% (90% CI, 30.8 to 63.0), with a disease control rate of 76.7% (90% CI, 60.6 to 88.5). The median duration of response and progression-free survival were 6.0 months (90% CI, 5.5 to 6.9) and 5.5 months (90% CI, 3.9 to 8.1), respectively. At data cutoff, 15 patients (50.0%) had died, and the estimated 12-month overall survival rate was 53.6% (90% CI, 36.8 to 67.8). The two most common treatment-emergent adverse events (TEAEs) were pyrexia (43.3%) and diarrhea (40.0%). Grade ≥3 TEAEs were reported in 18 patients (60.0%), with the most common being cholangitis, decreased appetite, and nausea (all 10.0%), which were generally not treatment related. TEAEs led to treatment regimen discontinuation in one patient, and there were no deaths due to TEAEs. CONCLUSION Tucatinib combined with trastuzumab had clinically significant antitumor activity and was well tolerated in patients with previously treated HER2+ mBTC.

4007 Background: Biliary tract cancer (BTC) is an aggressive malignancy with a poor prognosis, and current treatment options for advanced BTC are limited, with second-line therapy, FOLFOX and S-1 offering an objective response rate (ORR) of 5.0% and 7.5%, respectively. Up to 20% of BTCs overexpress human epidermal growth factor receptor 2 (HER2). Tucatinib (TUC) is a highly selective HER2-directed TKI approved for HER2-positive (HER2+) metastatic breast and colorectal cancer. Discussed here are the efficacy and safety results of TUC combined with Trastuzumab (Tras) in pts with previously treated HER2+ metastatic BTC. Methods: SGNTUC-019 (NCT04579380) is an open-label phase 2 basket study evaluating efficacy, safety, and tolerability of TUC and Tras in pts with HER2-altered solid tumors. Pts in the BTC cohort had been previously treated with and progressed after ≥1 line of systemic therapy for metastatic disease. Eligible pts had locally determined HER2+ (defined as HER2 overexpression determined by immunohistochemistry [IHC] 3+ or HER2 amplification determined by in situ hybridization assay or next-generation sequencing) metastatic BTC. Pts were treated on a 21-day cycle with TUC (300 mg orally twice a day) and Tras (8 mg/kg IV followed by 6 mg/kg every 3 wks). Disease status was determined based on RECIST v1.1 with assessments performed every 6 wks for 24 wks and every 12 wks thereafter. The primary endpoint is confirmed objective response rate (cORR) per investigator assessment. Secondary endpoints include overall survival (OS), disease control rate (DCR), duration of response (DOR), progression-free survival (PFS), and safety. Results: Thirty pts were enrolled in the BTC cohort as of data cutoff date of 30 Nov 2022. The median duration of follow-up was 8.3 months. cORR was 46.7% (90% CI, 30.8, 63.0), with 14 responses including 1 complete and 13 partial responses. Median DOR was 6.0 months (90% CI, 5.5, not estimable). DCR was 76.7% (n=23; 90% CI, 60.6, 88.5), and median PFS was 5.5 months (90% CI, 3.9, 8.1). At data cutoff, 13 (43.3%) patients had died, and the 12-months OS rate was 53.8% (90% CI, 35.2, 69.1%). Overall, the most common treatment-emergent adverse events (TEAEs) reported were pyrexia (43.3%) and diarrhea (40.0%). Grade ≥3 TEAEs were reported in 18 (60.0%) of 30 pts; however, only 6 (20.0%) and 2 (6.7%) of these pts had Grade ≥3 TEAEs related to TUC and Tras, respectively. Two (6.7%) pts discontinued TUC due to TEAEs, cholangitis and liver disorder. No deaths were due to TEAEs. Conclusions: The combination of TUC and Tras was well tolerated in pts with previously treated HER2+ metastatic BTC. The observed antitumor activity supports the combination of TUC and Tras as a future chemotherapy-free treatment option for this population with historically poor outcomes. Clinical trial information: NCT04579380 .