An elastin-affinity-targeted, conformation-specific anti-fibrillar-medin IgG1 (ETAMA) exploits the tunica media's ela...

IF a conformation-specific anti-fibrillar-medin monoclonal antibody (analogous to the clone C9 epitope profile described by Wagner et al., engineered as a full IgG1 with intact Fc for Fcγ receptor-mediated phagocytosis) is conjugated to a short elastin-affinity peptide (EAP; e.g., VVGSALMA or equivalent high-affinity elastin-binding sequence) to yield an Elastin-Targeted Anti-Medin Antibody (ETAMA) and administered intravenously (10–30 mg/kg, q2w × 12 weeks) to aged wild-type C57BL/6J mice (18–24 months, both sexes),

THEN quantifiable reductions in aortic medial medin aggregate burden (≥40% reduction in insoluble medin by ELISA and immunohistochemical fibril scoring), restoration of aortic compliance (measured by pulse wave velocity, PWV; ≥15% reduction vs. age-matched IgG control), and attenuation of downstream cerebrovascular medin co-pathology (reduced Aβ co-deposition in cerebral vessels) will be observed,

BECAUSE the following causal chain is supported by synthesized evidence:

1. Medin fibrils accumulate as protease-resistant, insoluble extracellular aggregates co-localizing with the internal elastic laminae of the aged aortic media, a compartment that is architecturally avascular, receives nutrients by diffusion, and is therefore largely inaccessible to circulating immune effectors and unmodified therapeutic antibodies — the central structural barrier to clearance (Medin aggregates in aged aorta are immunolocalized to extracellular deposits at elastic laminae and are absent in young or Mfge8-C2-KO tissue)[(https://doi.org/10.1073/pnas.2011133117/-/DCSupplemental.)].

2. The elastin-affinity peptide domain of ETAMA exploits the extraordinary elastin density of the tunica media — the aortic media is composed of ~50% dry-weight elastin and represents the dominant elastin reservoir in the mammalian body — causing preferential biodistribution and prolonged retention of the antibody conjugate at precisely the anatomical compartment where medin deposits reside, a cross-disciplinary approach borrowed from biomaterials elastin-targeted drug delivery (EBP-drug conjugate tissue accumulation) [SPECULATIVE — direct pharmacokinetic confirmation in aortic tissue is required].

3. The fibril-conformation-specific Fab arm of ETAMA binds exclusively to the cross-β sheet neo-epitopes of medin fibrils, which are cryptic within the native folded C2 discoidin domain of the physiological soluble MFG-E8 precursor, thereby sparing the efferocytosis-mediating function of full-length lactadherin; the fibrillar-specific epitope is structurally distinct from the native C2 domain and is exposed only upon proteolytic liberation and conformational shift of the medin fragment (Wagner et al., Nature, 2022; structural distinction between precursor and fibril discussed in evidence set) [(https://doi.org/10.1073/pnas.2011133117/-/DCSupplemental.)].

4. **Fc-region opsonization by the retained ETAMA recruits adventitial macrophages and vasa vasorum-associated m...

SENS category: GlycoSENS

Key references: • doi.org/10.1073/pnas.2011133117/-/DCSupplemental.