A Phase I Study of PRS-343 Immunotherapy for HER2-Positive Cancers, including Esophageal and Gastric Cancers


Full Title

PRS-343-PCS_04_16: A Phase 1, Open-Label, Dose Escalation Study of PRS-343 in Patients with HER2-Positive Advanced or Metastatic Solid Tumors


About one in four esophageal and stomach (gastric) cancers have a protein called HER2, which fuels cancer growth. The standard treatment for these patients is a HER2-targeting drug called trastuzumab, combined with chemotherapy. But if the cancer stops responding to this treatment, there is no other effective therapy.

The purpose of this study is to evaluate the safety and determine the best dose of investigational PRS-343 immunotherapy for patients with advanced HER2-positive esophageal and stomach cancers that have continued to grow despite prior anti-HER2 treatment. PRS-343 is a protein that targets HER2 and an immune receptor called CD137. PRS-343 encourages CD137-containing immune cells to group together and connect with HER2-containing tumor cells. This connection may allow CD137 to stimulate the immune system to attack the HER2-positive cancer cells.

In addition to esophageal and stomach cancers, patients with other HER2-containing tumors are also eligible, including those with colorectal, biliary, breast, and bladder cancers.

PRS-343 is given intravenously (by vein).


To be eligible for this study, patients must meet several criteria, including but not limited to the following:

  • Patients must have inoperable or metastatic HER2-positive esophageal or stomach cancer that came back or continued to grow despite another anti-HER2 treatment.
  • Patients may also have other HER2-positive cancers, including colorectal, biliary, breast, and bladder cancers; breast cancers must have grown despite standard anti-HER2 treatment.
  • At least 3 weeks must pass since the completion of prior therapies (4 weeks since the last dose of trastuzumab or ado-trastuzumab emtansine) and entry into the study.
  • Patients must be physically well enough that they are fully ambulatory, capable of all self care, and are capable of all but physically strenuous activities. As an example, patients must be well enough that they would be able to carry out office work or light housework.
  • This study is for patients age 18 and older.

For more information about this study and to inquire about eligibility, please contact Dr. Geoffrey Ku at 646-888-4588.