QL1706 (Iparomlimab/Tuvonralimab): A Comprehensive Analysis of a Novel Bifunctional PD-1/CTLA-4 MabPair Immunotherapy

Executive Summary

QL1706 is a first-in-class, investigational bifunctional antibody product developed by Qilu Pharmaceutical Co., Ltd., representing a significant innovation in the field of cancer immunotherapy. Identified by the DrugBank ID DB17562 and the development code PSB205, QL1706 is not a single bispecific antibody but rather a co-formulated mixture of two distinct monoclonal antibodies: Tuvonralimab, an anti-Programmed Death-1 (PD-1) IgG4 antibody, and Iparomlimab, an anti-Cytotoxic T-Lymphocyte-Associated Protein 4 (CTLA-4) IgG1 antibody. This unique composition is achieved through the proprietary MabPair™ technology platform, which enables the production of both antibodies from a single cell line at a fixed ratio, ensuring consistent delivery and synergistic action.

The core therapeutic rationale of QL1706 is to harness the proven synergistic anti-tumor efficacy of dual PD-1 and CTLA-4 blockade while mitigating the significant immune-related toxicities that have limited the use of conventional combination therapies. This is achieved through sophisticated bioengineering of the Iparomlimab (anti-CTLA-4) component to possess a shorter elimination half-life compared to the Tuvonralimab (anti-PD-1) component. This design provides a potent initial "pulse" of CTLA-4 inhibition to prime a broad T-cell response, followed by sustained PD-1 inhibition to maintain the activity of these T-cells within the tumor microenvironment, thereby uncoupling efficacy from cumulative toxicity.