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The prosperity of the biotherapeutics market reflects the feasibility and effectiveness of therapeutic antibodies for the treatment of cancers, inflammatory disorders, and refractory infections. As drawbacks emerge in clinical trials and practice, such as impeded binding, reduced effector functions, and frequent adverse reactions, modifications of therapeutic antibodies are unprecedently burgeoning in research and development (R&D). These modifications include: ① modified glycosylation; ② fragment of crystallizable domain (Fc) amino acid alterations; ③ cross-isotype or cross-subclass exchanges; ④ antibody–drug conjugates (ADCs); ⑤ single chain of variable region fragment (scFv) for chimeric antigen receptor T (CAR-T) cells; and ⑥ bispecific antibodies (bsAbs) in order to promote binding affinity, half-life in circulation, effectiveness toward target cells and, ultimately, to achieve overall improved efficacy. While many achievements have been made around the world in the past decades, China has been playing an active role in this realm, with its great demand for biotherapeutics with R&D potential. This review recapitulates the international progress that has been achieved with modified therapeutic antibodies, and then focuses on that of China in an independent section.

CD147, a member of the immunoglobulin superfamily (IgSF), plays fundamental roles in intercellular interactions in numerous pathological and physiological processes. Importantly, our previous studies have demonstrated that HAb18G/CD147 is a novel hepatocellular carcinoma (HCC)-associated antigen, and HAb18G/CD147 stimulates adjacent fibroblasts and HCC cells to produce elevated levels of several matrix metalloproteinases, facilitating invasion and metastasis of HCC cells. In addition, HAb18G/CD147 has also been shown to be a novel universal cancer biomarker for diagnosis and prognostic assessment of a wide range of cancers. However, the structural basis underlying the multifunctional character of CD147 remains unresolved. We report here the crystal structure of the extracellular portion of HAb18G/CD147 at 2.8A resolution. The structure comprises an N-terminal IgC2 domain and a C-terminal IgI domain, which are connected by a 5-residue flexible linker. This unique C2-I domain organization is distinct from those of other IgSF members. Four homophilic dimers exist in the crystal and adopt C2-C2 and C2-I dimerization rather than V-V dimerization commonly found in other IgSF members. This type of homophilic association thus presents a novel model for homophilic interaction between C2 domains of IgSF members. Moreover, the crystal structure of HAb18G/CD147 provides a good structural explanation for the established multifunction of CD147 mediated by homo/hetero-oligomerizations and should represent a general architecture of other CD147 family members.

Purpose: HAb18G/CD147 is a hepatocellular carcinoma (HCC)-associated antigen. We developed iodine ( 131 I) metuximab injection (Licartin), a novel 131 I-labeled HAb18G/CD147-specific monoclonal antibody F(ab') 2 fragment, and evaluated its safety, pharmacokinetics, and clinical efficacy on HCC in Phase I/II trials. Methods and Materials: In a Phase I trial, 28 patients were randomly assigned to receive the injection in 9.25-, 18.5-, 27.75-, or 37-MBq/kg doses by hepatic artery infusion. In a multicenter Phase II trial, 106 patients received the injection (27.75 MBq/kg) on Day 1 of a 28-day cycle. Response rate and survival rate were the endpoints. Results: No life-threatening toxic effects were found. The safe dosage was 27.75 MBq/kg. The blood clearance fitted a biphasic model, and its half-life was 90.56–63.93 h. In the Phase II trial, the injection was found to be targeted and concentrated to tumor tissues. Of the 73 patients completing two cycles, 6 (8.22%) had a partial response, 14 (19.18%) minor response, and 43 (58.90%) stable disease. The 21-month survival rate was 44.54%. The survival rate of progression-free patients was significantly higher than that of patients with progressive disease after either one or two cycles ( p p = 0.0019). Conclusion: Iodine ( 131 I) metuximab injection is safe and active for HCC patients.