The effects of zotuximab can begin to be felt a few days after the injection.

Zoltuximab (zolbetuximab-clzb) is an emerging targeted therapy drug, mainly used to treat CLDN18.2-positive gastric cancer and gastroesophageal junction adenocarcinoma. As a monoclonal antibody, it activates the immune system to attack tumors by specifically binding to the CLDN18.2 protein on the surface of tumor cells, thereby controlling tumor growth and reducing tumor volume. How quickly the effects of zotuximab are felt after injection depends not only on the pharmacological mechanism of action of the drug, but also on individual differences in patients, tumor burden, and treatment options.

Generally speaking, the effect of zotuximab is an anti-tumor treatment of immunomodulatory nature, and the effect is often not as immediate as that of chemotherapy. Clinical trial data show that patients began to experience objective tumor responses, including tumor shrinkage and symptom relief, after 2 to 3 cycles of zotuximab treatment (each cycle was generally 3 weeks). This means that approximately 6 to 9 weeks after the first injection, patients may first feel the actual effects of the treatment. At this time, changes in tumor volume can be observed through imaging examinations such as CT or MRI scans, and the patients themselves may also report improvements in symptoms, such as pain relief and increased physical strength.

It is worth noting that the therapeutic effect of zotuximab has a certain delay, mainly because its mechanism relies on the activation of the immune system and the immune-mediated killing of tumor cells. The immune system takes a certain amount of time to recognize and attack tumor cells. Therefore, during the initial treatment, the tumor may not shrink temporarily or even undergo pseudo-progression, that is, the tumor volume temporarily increases on imaging, but this does not mean that the treatment has failed. Physicians usually advise patients to adhere to treatment and observe subsequent changes in efficacy.

Reference materials:https://www.astellas.com/en/news/29401