Zenocutuzumab is a recombinant, humanized, full-length IgG1 bispecific monoclonal antibody designed to simultaneously target human epidermal growth factor receptor 2 (HER2/ERBB2) and human epidermal growth factor receptor 3 (HER3/ERBB3). It was originally developed under the code MCLA-128 and is also known by the development designation MCLA128.
Zenocutuzumab is a biologic active pharmaceutical ingredient used in targeted oncology. The antibody contains two different Fab arms that recognize HER2 and HER3, enabling simultaneous interaction with both receptor targets. FDA describes zenocutuzumab-zbco as a low-fucose humanized full-length IgG1 bispecific HER2- and HER3-directed antibody produced in a Chinese hamster ovary (CHO) mammalian cell line using recombinant DNA technology. Its molecular weight is approximately 146 kDa.
The substance is identified by CAS Number 1969309-56-5 and FDA GSRS UNII AE72RB1W1X. The USAN statement identifies the molecular weight as approximately 145.90 kDa, while current analytical-product data report approximately 145.76 kDa. The small difference reflects the molecular characterization convention and product representation of this complex glycoprotein rather than a small-molecule molecular-weight calculation.
Zenocutuzumab was developed as MCLA-128 and subsequently received the nonproprietary name zenocutuzumab. The marketed U.S. product is BIZENGRI (zenocutuzumab-zbco).
The U.S. Food and Drug Administration granted accelerated approval to BIZENGRI on December 4, 2024, for adults with advanced, unresectable or metastatic non-small cell lung cancer (NSCLC) harboring an NRG1 gene fusion after progression on or after prior systemic therapy, and for adults with advanced, unresectable or metastatic pancreatic adenocarcinoma harboring an NRG1 gene fusion after progression on or after prior systemic therapy.
In May 2026, FDA expanded the approved use of zenocutuzumab-zbco to adults with advanced, unresectable or metastatic cholangiocarcinoma harboring an NRG1 gene fusion after progression on or after prior systemic therapy.
Zenocutuzumab is a HER2 × HER3 bispecific antibody. One binding arm recognizes HER2 while the other recognizes HER3. By engaging both receptors, zenocutuzumab interferes with HER2/HER3 receptor signaling and inhibits signaling associated with neuregulin 1 (NRG1).
FDA describes the mechanism as binding extracellular domains of HER2 and HER3, inhibiting HER2 dimerization and preventing NRG1 binding to HER3. The antibody can also recruit immune effector mechanisms through its IgG1 Fc region.
The dual-targeting approach is particularly relevant to tumors driven by NRG1 gene fusions, in which abnormal neuregulin signaling can promote HER3-dependent oncogenic signaling.
Zenocutuzumab is not a conventional low-molecular-weight API. It is a highly complex recombinant glycoprotein consisting of two antibody heavy-chain/light-chain units configured as a bispecific IgG1 molecule.
FDA characterizes the molecule as a low-fucose humanized IgG1. The USAN chemical identity describes separate anti-ERBB3 and anti-ERBB2 heavy-chain components associated with humanized kappa light chains and specifies multiple disulfide bridges and glycosylation information. The USAN molecular formula representation is C6479H9971N1725O2027S45 for the non-glycosylated representation, with an indicated molecular weight of approximately 145.90 kDa.
Because glycosylation and other post-translational characteristics contribute to the molecular heterogeneity of therapeutic antibodies, molecular weight is appropriately expressed in kilodaltons (kDa) rather than as a conventional small-molecule molecular weight.
Zenocutuzumab is produced using recombinant DNA technology in a Chinese hamster ovary (CHO) mammalian cell line. This production system supports expression of the complex antibody architecture and the required post-translational processing.
For biological API manufacturing, control of the production cell substrate, upstream processing, downstream purification, viral safety, aggregate levels, charge variants, glycosylation profile, host-cell proteins, residual DNA and other process-related impurities is critical.
Zenocutuzumab-zbco is used as a targeted biologic therapy for selected patients with NRG1 gene fusion-positive solid tumors.
Current U.S. FDA-approved indications include:
The 2024 FDA approval was accelerated and the 2026 cholangiocarcinoma approval expanded the labeled use to another NRG1 fusion-positive tumor type.
The approved BIZENGRI drug product is supplied as a sterile, clear to slightly opalescent, colorless to slightly yellow, preservative-free intravenous infusion solution.
The FDA-approved presentation contains 375 mg of zenocutuzumab-zbco in 18.75 mL, corresponding to a concentration of 20 mg/mL. The formulation has a stated pH of 6.0. The formulation contains histidine, L-histidine hydrochloride monohydrate, polysorbate 20, trehalose and water for injection.
These values describe the approved finished drug product and should not automatically be treated as universal bulk drug-substance specifications.
Quality control for Zenocutuzumab requires a biologics-specific analytical strategy. Unlike conventional chemical APIs, identity and purity cannot be adequately established using only HPLC assay and loss-on-drying testing.
Suitable characterization and release-related analytical approaches can include:
The exact acceptance criteria are manufacturing-process and regulatory-filing specific.
Commercial research-grade Zenocutuzumab is reported by MedChemExpress at 99.9% purity, with a selected batch shown at 99.98% purity/assay. These values are useful as analytical-product references but should not be represented on a pharmaceutical API page as a universal FDA release limit.
For an SDP pharmaceutical API page, it is therefore more technically accurate to state the assay/purity requirement as Product-Specific Specification while optionally identifying 99.98% as a reported research-grade batch value in the product data.
Identification of Zenocutuzumab should rely on orthogonal biological and physicochemical methods rather than a single small-molecule identification test.
Peptide mapping can confirm the expected amino-acid sequence and structural identity. Mass spectrometry can support molecular characterization, while SDS-PAGE and chromatographic methods can provide additional confirmation of the expected antibody structure.
Functional identification may additionally use a validated HER2/HER3 binding or biological activity assay.
Aggregation is an important quality attribute for monoclonal and bispecific antibodies. High-molecular-weight species can be evaluated using size-exclusion chromatography.
SEC-HPLC is therefore an appropriate analytical technique for evaluating the monomeric antibody fraction and higher-molecular-weight species. The exact acceptance limit should be taken from the applicable drug-substance specification rather than assigning an unsupported universal numerical limit.
Low-molecular-weight fragments and other protein-related impurities may be evaluated using orthogonal electrophoretic and chromatographic techniques.
Zenocutuzumab's biological activity is related to its ability to bind HER2 and HER3 and interfere with NRG1-dependent signaling.
A suitable potency strategy can incorporate validated receptor-binding and/or cell-based functional assays that demonstrate the expected biological activity. For a commercial pharmaceutical drug substance, the approved potency assay and acceptance criteria are specific to the manufacturer's validated control strategy.
The approved BIZENGRI drug product is stored under refrigerated conditions. FDA's approval documentation states an 18-month dating period for the finished drug product when stored at 2°C to 8°C. The drug substance has separate stability and storage requirements defined in the approved manufacturing documentation.
For bulk Zenocutuzumab drug substance, storage should therefore follow the applicable validated manufacturer specification and certificate of analysis rather than automatically applying the finished-product storage condition.
Zenocutuzumab is a specialized recombinant bispecific monoclonal antibody API targeting HER2 and HER3. With an approximate molecular weight of 146 kDa, CHO-cell recombinant production and complex antibody architecture, its quality evaluation requires biologics-specific analytical controls.
For pharmaceutical manufacturers and biotechnology companies evaluating Zenocutuzumab, important quality attributes include molecular identity, protein concentration, purity, aggregates, charge variants, glycosylation, host-cell-derived impurities, residual DNA, endotoxin and biological potency.
Because Zenocutuzumab is a complex biological API, its pharmaceutical specification should be based on the applicable validated manufacturing process, analytical methods and regulatory requirements rather than conventional small-molecule API limits.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |