| 背景 | ICH5337 is a research-grade biosimilar of alextatug, supplied as an unconjugated, non-therapeutic analog of the originator antibody for research use only. Alextatug (proposed INN alextatugum) is a fully human IgG1-lambda monoclonal antibody directed against a tumor-restricted extracellular ribonucleoprotein (RNP) complex containing PABPC1 (poly(A)-binding protein cytoplasmic 1, UniProt P11940) bound to poly(A) RNA. This ichor.bio product reproduces the binding specificity of the originator so that investigators can study target engagement, neutralisation, and effector function in controlled in-vitro and functional settings without the cost or regulatory constraints of clinical material. It is not a clinical drug and is not intended for therapeutic or diagnostic use in humans. The material is manufactured to in-vivo research standards with low endotoxin (research grade below 1 EU/mg; ultra-low grade below 0.5 EU/mg) and is available in bulk milligram-to-gram quantities, making it suitable as a reference standard, positive control, or comparator in assays that characterise the target and its extracellular presentation. Because the target is human, this reagent is oriented toward functional and in-vitro applications rather than routine mouse dosing.
PABPC1 (polyadenylate-binding protein cytoplasmic 1; UniProt P11940, 636 aa) is a highly conserved RNA-binding protein that normally resides in the cytoplasm, where it binds the poly(A) tail of mRNAs through its RRM domains to regulate mRNA stability, translation initiation, and turnover. It is a central hub of post-transcriptional control and is frequently upregulated in cancers, where it has been linked to proliferation, metastasis, and poor prognosis. What makes alextatug's target unusual is that the antibody does not recognise free intracellular PABPC1: it binds a tumor-restricted extracellular ribonucleoprotein complex in which PABPC1 is presented bound to poly(A) RNA. This conformational, complex-dependent epitope is what confers tumor selectivity, since the assembled extracellular RNP is not present on normal tissue in the same form. |
|---|
