IMU-131 is a single peptide structure composed of 3 individual B-cell epitope peptide sequences selected from HER2/neu structure. Polyclonal antibodies against IMU-131 peptides bind three separate regions of the HER2 receptor and also to the dimerization loop of the HER2 receptor, preventing dimerization, which in turn inhibits intracellular signaling. This blockade of the HER2 signaling pathways is thought to be substantially greater than that with trastuzumab alone. Safety and immunogenicity of the 3 peptides have been shown in Phase 1a testing of an earlier formulation of IMU-131. The shelf stability of the Phase 1a vaccine was not optimal and hence the formulation was adjusted for IMU-131. The three B-cell epitope peptides (P4, P6 and P7) were combined in a specific order resulting in a single fusion peptide of 49 amino acids in length (P467). This new formulation of IMU-131 has extended stability and improved immunogenicity compared to the formulation used previously. The new vaccine IMU-131 produces a stronger and more rapid polyclonal antibody response and is efficient to manufacture compared with previous formulations. Based on these three known epitopes (P4, P6 and P7), the investigators developed a single peptide antigen (P467), which allows simplification of the manufacturing process.~It is hypothesized that administration of IMU-131 in addition to chemotherapy will prolong survival and may delay tumor progression and/or reduce tumor burden in patients with HER2/neu overexpressing gastric or gastroesophageal junction (GEJ) adenocarcinoma (otherwise known as Advanced Cancer of the Stomach (ASC)).~The Phase 1b study aims to determine the safety and tolerability of IMU-131 and identify the Recommended Phase 2 Dose (RP2D) of IMU-131 in combination with chemotherapy in HER2/neu overexpressing ACS to carry into the Phase 2 dose expansion study. The Phase 2 component will be submitted as an amendment and will be initiated following completion of Phase 1b. Phase 2 will be designed to further characterize the safety and to explore clinical activity of IMU-131 in combination with chemotherapy in HER2/neu overexpressing ACS.The Phase 2 study is a randomized, open label comparison of IMU-131 plus standard of care chemotherapy versus standard of care chemotherapy alone.
The Phase 1b study is an open-label, multicenter dose escalation study designed to assess the safety, tolerability, immunogenicity and recommended phase 2 dose (RP2D) of IMU-131. The RP2D will be evaluated in the dose expansion Phase 2 study. The Phase 2 study is a randomized, open label comparison of IMU-131 plus standard of care chemotherapy versus standard of care chemotherapy alone.