Henlius：HLX3902 has received its clinical trial approval.
On June 17, the CDE official website announced that Henlius’ HLX3902 Injection has been approved for clinical trial in China, intended for the treatment of metastatic castration-resistant prostate cancer and other advanced solid tumors. According to the Insight database, HLX3902 is Henlius’ first trispecific antibody approved for clinical trial and the world’s first-in-class STEAP1×CD3×CD28 trispecific antibody to receive clinical trial clearance.
Prostate cancer typically presents as an “immune-cold” tumor—characterized by sparse T cell infiltration, low antigen presentation capacity, and an abundance of immunosuppressive factors—which limits the efficacy of immune checkpoint inhibitors such as PD-1 inhibitors. STEAP1 is highly expressed in over 85% of prostate tumors while being nearly absent in normal tissues, making it a highly specific therapeutic target. T cell engagers (TCEs) targeting STEAP1 can simultaneously bind CD3 on T cells and STEAP1 on tumors, redirecting T cells to kill tumor cells, and have demonstrated anti-tumor activity in various models. However, existing TCEs primarily rely on CD3-mediated primary activation signals, and T cells lacking co-stimulatory signals in the solid tumor microenvironment are prone to exhaustion, limiting sustained anti-tumor efficacy. The introduction of CD28 co-stimulatory signaling can enhance T cell persistence and functional maintenance through a “dual-signal” activation mechanism.
As a trispecific antibody, HLX3902 simultaneously activates CD3 and CD28 to enhance T cell killing of STEAP1-expressing tumor cells. By optimizing both the first (CD3) and second (CD28) T cell activation signals, it enhances T cell activation, proliferation, and survival, prolonging the duration of anti-tumor immune responses. This enables it to demonstrate excellent anti-tumor activity even in low T cell infiltration environments.
Preclinical studies have shown that HLX3902 induces target-dependent T cell activation and cytotoxicity, outperforming traditional CD3 bispecific TCEs at low effector-to-target cell ratios. Repeated antigen stimulation models indicate that its CD28 co-stimulatory signal enhances T cell activation, proliferation, and memory T cell expansion, thereby maintaining durable killing effects. In C4-2/hPBMC and abiraterone-resistant PDX/hPBMC in vivo models, HLX3902 demonstrated significantly enhanced anti-tumor activity, accompanied by increased T cell infiltration and functional improvement. Additionally, in cynomolgus monkey studies, HLX3902 exhibited good tolerability and a manageable safety profile.
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