The distinctive features of our multi-specific antibody platform are biology function driven and structurally designed with enhanced flexibility and efficiency. The platform enables us to construct multi-specific antibodies quickly which facilitates the efficient production of multi-specific antibodies. Our multi-specific antibody platform enables us to develop antibodies simultaneously binding to different targets to achieve synergistic therapeutic functions. The major types of multi-specific antibody structure we are developing are set forth as below.

•T-cell engagers are designed to recruit T cells for the specific destruction of tumor cells. The unique designed multispecific antibody binds to tumor-associated antigens (TAAs) through two arms while simultaneously binding to the CD3 molecule with one arm, thereby increasing affinity for tumor cells and reducing off-target toxicity to T cells. However, the presence of scFv structures targeting TAAs in these multispecific antibodies often leads to aggregation, which is a significant challenge in the production process. To address this issue, we have optimized our platform using scFv stability enhancement techniques to improve the developability of these drugs.We have successfully developed two clinical-stage candidates using this platform: MBS303 (CD20/CD3) and MBS314 (GPRC5D/BCMA/CD3).

• Immune stimulation multi-specific antibody: In order to simultaneously bind to two different immune checkpoint targets, a 2:2 multi-specific antibody structure based on scFv tandem structure is designed. This type of multi-specific antibodies can be designed to enhance cross-linking, achieve efficacy synergies and increase enrichment towards tumor. We are currently developing a preclinical multi-specific antibody using this platform, We have also developed antibody cytokine fusion technology, by linking the mutated cytokine to the C terminal of PD-1 antagonist antibody. Based on the principle of cis-action, the fusion protein can select activated effector T cells. MBS309 (PD-1 antibody/IL2 fusion protein) is developed based on this technology. We have also applied scFv stability enhancement technology to improve drug developability.