A DNA‑encoded library screen of 4.2 billion compounds yielded a candidate small molecule now called DELC2, the authors reported. Short and direct: the screen produced a brain‑penetrant modulator of CHI3L1. Investigators characterized DELC2 with orthogonal biophysical approaches; the report described crystallography and binding assays that localized ligand engagement to the protein’s glycan‑recognition groove. The paper frames CHI3L1—elevated in Alzheimer’s disease CSF—as a target implicated in glial dysfunction and neuroinflammation.
Crystallographic data in the manuscript showed DELC2 occupying an aromatic‑hydrophobic pocket within the CHI3L1 glycan‑recognition groove. The pocket centers on two tryptophans, Trp99 and Trp352, which the authors identified as key contact residues. The structural work provided a concrete binding model; investigators used biophysical corroboration to support the crystallographic coordinates. The source did not report additional medicinal chemistry optimization or specific affinity constants in the abstract, and those details would require consulting the full text or supplementary files.
DELC2 disrupted a functional interaction between CHI3L1 and the receptor for advanced glycation end products (RAGE), according to the study team. In cell‑based assays, the molecule suppressed CHI3L1‑induced inflammatory signaling cascades. The authors noted a reduction in Gal‑3–positive microglia in treated cultures and a restoration of amyloid‑β uptake that had been impaired by CHI3L1 exposure. Short sentence: DELC2 mimicked CHI3L1 immunodepletion. Longer analytical sentence: when the investigators reintroduced CHI3L1 (add‑back), the inflammatory signaling and defects in amyloid‑β handling returned, indicating the observed cellular phenotype depended on CHI3L1 activity rather than an off‑target culture effect.
The authors analyzed human cerebrospinal fluid and reported elevated CHI3L1 concentrations in Alzheimer’s disease samples. Data indicated a correlation between CSF CHI3L1 and markers of astrocytic NF‑κB activation. This human association was presented alongside the preclinical mechanistic work; however, the abstract did not provide numerical CSF values or statistical measures, and those specifics were not included in the abstract text.
Oral DELC2 delivered sustained unbound brain exposure in the 5xFAD transgenic mouse model, the investigators observed. Treated mice showed improved cognitive performance, the report stated. DELC2 treatment also reduced multiple amyloid‑β species and attenuated inflammatory gene programs in both astrocytes and microglia. The manuscript presents these effects as convergent evidence that pharmacologic modulation of CHI3L1 can modify disease‑relevant pathology in this model.
In parallel experiments, DELC2 phenocopied the effects of CHI3L1 immunodepletion in vitro and in vivo assays, the authors reported. Conversely, adding back CHI3L1 restored inflammatory signaling and the defects in amyloid‑β handling. These bidirectional manipulations strengthen the causal link between CHI3L1 activity and the measured glial dysfunction. The abstract did not list the specific experimental conditions, concentrations, or timelines used for immunodepletion or add‑back, so readers should consult the full manuscript for protocol details.
This report is a preprint and has not been peer reviewed, the authors explicitly stated. The abstract positions DELC2 as a chemical scaffold for CHI3L1‑directed therapy but does not report human dosing, safety, or clinical trial data. The authors did not provide clinical pharmacokinetic parameters or toxicology details in the abstract. Open questions remain in the manuscript: whether DELC2’s efficacy and safety translate beyond the 5xFAD model, how long‑term modulation of CHI3L1 will affect disease progression, and what regulatory path might be required to advance DELC2 or derived scaffolds into first‑in‑human studies. Readers should review the full paper and supplementary material for experimental methods, numeric results, and any additional limitations the authors documented.