Effect of ethnicity and chemotherapy (mFOLFOX6) on zolbetuximab pharmacokinetics in patients with claudin 18.2-positive locally advanced or metastatic gastric or gastroesophageal junction adenocarcinoma (G/GEJ).

Abstract

e16078 Background: Zolbetuximab is a chimeric IgG1 monoclonal antibody that targets Claudin 18.2 (CLDN18.2), a tight junction protein that is normally confined to gastric mucosa but is retained in G/GEJ. A phase 2 (NCT01630083, FAST) trial demonstrated significantly prolonged survival with zolbetuximab + EOX (epirubicin, oxaliplatin, capecitabine) vs EOX in G/GEJ. Two global phase 3 studies are ongoing, comparing zolbetuximab + chemotherapy vs chemotherapy as first-line treatment in CLDN18.2-positive G/GEJ. This study assessed the influence of ethnic differences and chemotherapy on the pharmacokinetics (PK) of zolbetuximab in patients (pts) with G/GEJ and the potential effect of zolbetuximab on chemotherapy PK. Methods: In the Japanese phase 1 and global phase 2 studies, adult pts with CLDN18.2-postitive G/GEJ received zolbetuximab 800 mg/m2 IV on Cycle 1 Day 1 (Cycle 1 Day 3 in Cohort 2 of phase 2) then 600 mg/m2 Q3W. Phase 1 and Cohort 1A of the phase 2 study assessed zolbetuximab monotherapy in 21-day cycles. Cohort 2 of the phase 2 study assessed zolbetuximab + mFOLFOX (5-FU, folinic acid, oxaliplatin; 4 cycles) in 42-day cycles (Q2W from Cycle 1 Day 1). Blood samples for zolbetuximab PK following single and multiple doses, and for chemotherapy (5-FU and oxaliplatin) PK alone or with zolbetuximab were collected. Maximum serum drug concentration (Cmax) and area under the concentration-time curve from 0-21 days (AUC0-21) were assessed. Potential ethnic differences in zolbetuximab exposures across Japanese, other Asian (Korean and Taiwanese), and Western pts, and the potential drug-drug interaction between zolbetuximab and chemotherapy were evaluated. Results: Zolbetuximab concentration profiles and PK parameters were generally comparable across Japanese, other Asian, and Western populations (Table). Zolbetuximab PK properties were similar between monotherapy and combination therapy cohorts (Table). Chemotherapy PK was comparable with and without zolbetuximab. Conclusions: The analyses suggest no apparent ethnic differences in zolbetuximab PK across Japanese/Asian and Western pts and no PK interactions between zolbetuximab and mFOLFOX6. These results support the use of zolbetuximab and mFOLFOX without the need for dose adjustment in global phase 3 trials. Clinical trial information: NCT03505320, NCT03528629. [Table: see text]