Summary
This study is looking at a medicine called zolbetuximab for people with cancer in the stomach, or the area where the food pipe (oesophagus) joins the stomach, called the gastro-oesophageal junction (GEJ).
Some stomach and GEJ cancers have a protein on their surface called Claudin 18.2. Zolbetuximab is designed to attach to this protein and help the body’s immune system find and attack the cancer cells. People in this study must have cancer that is Claudin 18.2-positive and HER2-negative (meaning the cancer does not have the HER2 protein).
This study will give more information about how well zolbetuximab works when given with an immunotherapy medicine called pembrolizumab and chemotherapy.
Who can take part
Adults may join if they have:
- Locally advanced, unresectable, or metastatic stomach or GEJ cancer
- A tumour that is Claudin 18.2-positive, HER2-negative and has the PD-L1 protein
- Possibly some previous cancer treatment is allowed – speak with your doctor about this.
People cannot join if they:
- Need medicines that weaken the immune system
- Have blockages or bleeding in the stomach or gut
- Have specific uncontrollable cancers such as untreated cancers in the nervous system
- Have certain heart conditions or infections
Study treatments
Participants will be randomly assigned (by chance) to receive one of these combinations:
- Zolbetuximab + pembrolizumab + chemotherapy, or
- Placebo + pembrolizumab + chemotherapy
Neither the participants or the study doctors will know who is getting zolbetuximab or placebo.
How treatment is given
Medicines are given through a vein (IV infusion) on a schedule of 6-week cycles. Zolbetuximab or placebo will be given every 2 or 3 weeks.
Chemotherapy will either be:
- CAPOX: Oxaliplatin infusion every 3 weeks, Capecitabine tablets twice daily for 14 days at the start and again mid-cycle. After 8 cycles, only capecitabine will continue.
- Or mFOLFOX6: An infusion every 2 weeks. After 12 cycles, only folinic acid and fluorouracil continue.
Pembrolizumab is given every 3 or 6 weeks, depending on the dose schedule). People may receive pembrolizumab for up to 2 years.
Participants will stay in the study until their cancer gets worse, side effects become too difficult, or they need another cancer treatment.
Study visits and follow up
During the study, people will visit the clinic regularly for treatment and health checks. Doctors will monitor for any side effects and scans will be done to check how the cancer is responding. If the cancer gets worse, participants may be asked for another tumour sample (optional).
After stopping treatment, clinic visits will continue for health checks with scans every 9-12 weeks and phone check-ins every 3 months. The number of visits and tests may vary depending on each person’s health and how long they stay on treatment.