Zolbetuximab + mFOLFOX6 as first-line (1L) treatment for patients (pts) withclaudin-18.2+ (CLDN18.2+) / HER2− locally advanced (LA) unresectable or metastatic gastric or gastroesophageal junction (mG/GEJ) adenocarcinoma: Primary results from phase 3 SPOTLIGHT study

LBA292

Background: 1L treatment for pts with HER2−, mG/GEJ adenocarcinoma is typically chemotherapy and immunotherapy; an unmet need still exists. CLDN18.2 is expressed in normal gastric mucosa cells and retained in mG/GEJ tumor cells. In the FAST study, zolbetuximab, which targets CLDN18.2, prolonged survival of pts with LA unresectable or mG/GEJ adenocarcinoma when combined with chemotherapy. SPOTLIGHT (NCT03504397) is a phase 3 global, double-blind study comparing zolbetuximab + folinic acid, 5-FU, and oxaliplatin (mFOLFOX6) vs placebo + mFOLFOX6 as 1L treatment for pts with CLDN18.2+/ HER2−, LA unresectable or mG/GEJ adenocarcinoma. Methods: Previously untreated pts with CLDN18.2+ (moderate-to-strong membrane staining in ≥75% tumor cells by IHC)/HER2− LA unresectable or mG/GEJ adenocarcinoma were randomized 1:1 to zolbetuximab IV 800 mg/m2 (cycle [C] 1, day [D] 1) followed by 600 mg/m2 (C1D22, and every 3 weeks in later cycles) + mFOLFOX6 IV (D1, 15, 29) for four 42-day cycles vs placebo + mFOLFOX6; pts without PD continued for >4 cycles with zolbetuximab or placebo, + folinic acid and 5-FU at investigator’s discretion until PD or discontinuation criteria were met. The primary endpoint (EP) was PFS per RECIST v1.1 by IRC. Secondary EPs included OS, ORR, and safety. Differences in efficacy between treatment arms were tested by stratified log rank tests; OS was tested if PFS was significant. Results: Among 2735 pts screened, 565 pts were randomized 1:1 to zolbetuximab + mFOLFOX6 (N = 283) or placebo + mFOLFOX6 (N = 282). PFS was statistically significantly improved with zolbetuximab + mFOLFOX6 (median 10.61 vs 8.67 mo, HR 0.751, P=0.0066; Table). OS was also significantly improved (median 18.23 vs 15.54 mo, HR 0.750, P=0.0053, < 0.0135 as boundary; Table). ORR was similar between treatment arms. Most common TEAEs with zolbetuximab + mFOLFOX6 were nausea (82.4% vs 60.8% in zolbetuximab vs placebo arms), vomiting (67.4% vs 35.6%), and decreased appetite (47.0% vs 33.5%); the incidences of serious TEAEs were similar between both arms (44.8% vs 43.5%). Conclusions: Targeting CLDN18.2 with 1L zolbetuximab combined with mFOLFOX6 statistically significantly prolonged PFS and OS in pts with CLDN18.2+/ HER2−, LA unresectable or mG/GEJ adenocarcinoma. TEAEs were consistent with previous studies. Zolbetuximab + mFOLFOX6 may be a new option for these pts. Funding source: This study was funded by Astellas Pharma Inc. Medical writing support, conducted in accordance with Good Publication Practice (GPP 2022) and the International Committee of Medical Journal Editors (ICMJE) guidelines, was provided by Ann Ferguson, PhD, of Oxford PharmaGenesis Inc., Newtown, PA, USA, and funded by Astellas Pharma Inc. Clinical trial information: NCT03504397 . [Table: see text]

Zolbetuximab plus gemcitabine and nab-paclitaxel (GN) in first-line treatment of claudin 18.2–positive metastatic pancreatic cancer (mPC): Phase 2, open-label, randomized study

TPS782

Background: GN is a first-line treatment option for patients (pts) with mPC. Poor prognosis and low 5-year survival rate ( < 5%) with mPC highlight the need for new therapeutics. Claudin 18.2 (CLDN18.2), a tight junction protein expressed exclusively on normal gastric epithelial cells, is maintained during malignant transformation in gastric cancers and is frequently expressed in some carcinomas from organs that do not normally express it, such as pancreatic cancer. Zolbetuximab, a chimeric IgG1 monoclonal antibody, binds to CLDN18.2 and mediates tumor cell death through antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity. This phase 2 study (NCT03816163) will assess safety and efficacy of GN alone or with zolbetuximab in CLDN18.2-positive mPC. Methods: The study was expanded to enroll approximately 369 pts with histologically confirmed mPC and high CLDN18.2 expression (moderate-to-strong IHC staining intensity in ≥75% of tumor cells). The study included a safety lead-in that enrolled 3-12 pts to assess safety/tolerability of zolbetuximab (n = 3 at 1,000 mg/m2 on Cycle 1 Day 1 then 600 mg/m2 Q2W, then expand/de-escalate using a 3+3 design) plus GN. Dose-limiting toxicities (DLTs, defined as a specified zolbetuximab-related toxicity that occurs during DLT assessment period) will be assessed after Cycle 1 (28 days). Based on the recommended phase 2 dose (RP2D), confirmed during the safety lead-in, approximately 357 pts will be randomized 2:1 to zolbetuximab Q2W on Days 1 and 15 plus GN on Days 1, 8, and 15 of each cycle (Arm 1), or GN alone on Days 1, 8, and 15 of each cycle (Arm 2). Randomization will be stratified by ECOG performance status (0 or 1) and liver metastasis (yes or no). At sites in Japan, DLTs (assessed from Cycle 1 Day 1 to Cycle 2 Day 1) will be evaluated in ≤6 pts randomized to the RP2D in Arm 1. Pts will undergo imaging (CT/MRI) at baseline and Q8W until investigator-assessed disease progression (RECIST v1.1) or the start of another systemic anticancer treatment, whichever comes earlier. In addition to confirming the RP2D during the safety lead-in, primary objectives are to assess whether treatment with zolbetuximab plus GN, versus GN alone, improves overall survival (randomization phase) and to establish the safety/tolerability profile of zolbetuximab plus GN (across the study). Secondary endpoints include progression-free survival, objective response rate, disease control rate, duration of response, pharmacokinetics, and health-related quality of life (per protocol amendment). Descriptive statistics will be used for continuous endpoints and frequency and percentage for categorical endpoints. Original protocol enrollment completion was in October 2021. Under the expanded protocol amendment, 95 of ~140 sites in North America, Latin America, Europe, and Asia Pacific were activated. Clinical trial information: NCT03816163 .