Serplulimab is a recombinant humanized monoclonal antibody targeting programmed cell death protein 1 (PD-1). It belongs to the IgG4-kappa antibody class and is designed to block the interaction between PD-1 and its ligands PD-L1 and PD-L2, thereby restoring T-cell activity against tumor cells. FDA GSRS identifies Serplulimab as a humanized IgG4-kappa antibody produced in Chinese hamster ovary (CHO) cells.
Serplulimab is also known by the development code HLX-10 and is the active substance in HETRONIFLY. The European Union authorized HETRONIFLY in 2025 for specified oncology indications.
Serplulimab is a full-length recombinant monoclonal antibody composed of two heavy chains and two kappa light chains. The EMA describes each heavy chain as containing 443 amino acids and each light chain as containing 214 amino acids. Its molecular weight without N-linked glycosylation is approximately 144 kDa.
Key identity information:
As a biological drug substance, Serplulimab cannot be characterized using the same conventional framework used for synthetic small-molecule APIs. Its quality depends on molecular identity, higher-order structure, purity, aggregation, charge variants, glycosylation, protein concentration, biological activity and process-related impurities.
WHO's recommended INN record defines Serplulimab as a humanized immunoglobulin G4-kappa anti-PD-1 monoclonal antibody, produced in CHO cells.
PD-1 is an inhibitory receptor expressed on T cells. Binding of PD-L1 or PD-L2 to PD-1 suppresses T-cell activity. Serplulimab binds PD-1 and prevents these ligand interactions, helping restore T-cell immune activity against malignant cells.
Serplulimab is an oncology immunotherapy used in combination regimens for selected cancers.
The current EU authorization includes:
Serplulimab API requires a biologics-specific analytical control strategy. Typical characterization and release testing may include:
Numerical acceptance limits should be taken from the approved drug-substance specification or validated manufacturer specification rather than applying small-molecule API limits.
Serplulimab is manufactured as a recombinant monoclonal antibody using CHO cells. FDA GSRS and EMA documentation identify CHO cells as the production system.
Manufacturing involves controlled cell culture, harvesting, purification, viral clearance, concentration/formulation and extensive characterization to ensure consistent antibody identity, purity and biological activity.
Serplulimab is a proteinaceous biological substance rather than a conventional crystalline chemical API. The EMA describes the finished medicinal product as a colourless to slightly yellow, clear to slightly opalescent solution.
The EU-authorized finished product is supplied as a 10 mg/mL concentrate for solution for infusion, with a 10 mL vial containing 100 mg serplulimab.
The authorized HETRONIFLY finished product is supplied in a Type I clear glass vial containing 10 mL of 10 mg/mL concentrate, equivalent to 100 mg serplulimab. It is stored at 2°C–8°C, must not be frozen, and should be protected from light in the original package.
These finished-product conditions should not automatically be represented as the API drug-substance stability specification.
A commercial Serplulimab API documentation package may include:
Serplulimab requires specialized biologics manufacturing capabilities because it is a recombinant anti-PD-1 monoclonal antibody. A suitable manufacturing program should incorporate controlled CHO-cell production, validated purification, viral clearance, structural characterization, potency testing and stringent impurity controls.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |