Daily digest — 2026-09-13

The real headline isn't the molecule, it's the RT-loop degron. G-loop CRBN neosubstrates have basically been the only playbook since the IMiD era, so a structurally distinct degron sitting in VAV1's SH3-2 domain is a genuine expansion of the addressable degradable proteome, not just one more target on the pile. The phenyl-glutarimide warhead itself is bog-standard IMiD-adjacent chemistry — nothing novel there; the real innovation is in the target-engagement biology, not the medchem. VAV1's hematopoietic-restricted expression is a nice built-in selectivity advantage most degrader programs would kill for. On the FEP/AI ternary angle: cooperativity scores tracking potency across one series is promising, but it's one dataset — I'd want to see it prospectively rank blind analogs before I trust it over empirical SAR.

Glycosyltransferases have a reputation for being nearly undruggable — shallow, solvent-exposed active sites built to grip a UDP-sugar donor and a growing acceptor chain, not a cozy pocket for a small molecule. So any inhibitor reaching nanomolar here deserves a second look. 60 analogs to go from micromolar to nanomolar on one scaffold is a lean, efficient campaign — a couple of hot spots optimized, not a fishing expedition. The 6-methoxyquinoline-4-carboxamide is flat and stackable, which reads like it's wedging into a groove near the sugar-binding cleft rather than mimicking the full UDP-GlcA donor. My real worry is the B3GAT family — B3GAT1/2/3 share a fold, and no selectivity data has been shown yet. First-in-class glycosyltransferase inhibitors are still rare in oncology, so this is a genuine new tool, but 'first-in-class' this early just means untested against the paralogs that matter.

This mechanism is what caught my eye: if cytotoxicity in JK-4b traced to deep induced-fit distortion in the classical pocket, moving the pharmacophore to a shallower, more solvent-exposed sub-pocket is a clean way to keep the RT H-bond network while shedding the strain that drives off-target hits. Retained potency against resistant variants is the real tell — K103N/Y181C-type mutations cluster in the classical pocket, so if 9n still works, its binding mode isn't leaning on that contact set, which also argues the toxicity really was off-target, not a right-target dose-limiting problem. Practically, a solvent-facing channel is easier SAR real estate — more room to tune logP/solubility without wrecking the core pharmacophore, so this reads generalizable, not a one-off rescue. Prefer this over the usual toxicity fixes (metabolite masking, prodrugging) — it's addressing binding geometry, not just downstream liability.

GLP-1R's orthosteric pocket is deep and peptide-shaped — basically undruggable at drug-like MW/logP, so all four of these (danuglipron, lotiglipron, DA-302168S, orforglipron) work through allosteric or biased engagement rather than mimicking the peptide directly. That's the clever workaround, but it means potency, selectivity, and clean signaling bias have to be re-optimized empirically each time instead of inherited from orthosteric geometry. GI tolerability tracking with off-target signaling bias is still the recurring failure mode — lotiglipron's discontinuation is the cautionary tale here. No convergent scaffold yet: four programs, four distinct chemotypes, still bespoke SAR rather than a template anyone can reuse. Orforglipron's approval is proof-of-concept, not a formula. Expect the same peptide-to-oral-small-molecule chase to hit GIP and glucagon receptor programs next.

If I'd been designing against the trough alone, I'd have built a static pharmacophore off one co-crystal pose and wondered why my analogs kept losing potency in ways the model couldn't explain — that's the D2 loop talking. A cryptic, conformation-dependent element next to your primary pocket means the 'druggable groove' you're staring at in PyMOL isn't the whole binding event; you need ensemble docking or short MD runs to even see the states worth targeting, not another round of rigid-receptor SBDD. This is the same lesson from Bcl-2/Mcl-1 and MDM2-p53 campaigns — flexible loops or helices near a defined hot spot often carry the selectivity, not the anchor pocket. No new chemical matter here, but it's a real prompt to revisit our PfAMA1 series with loop-aware ensembles before writing off SAR gaps as noise.

On-DNA chemistry is where good click reactions go to die — CuAAC needs copper that chews up your barcode, most coupling chemistry leaves truncation side-products you chase off HPLC for weeks. SuFEx actually respects the constraints: no metal, no coupling reagent, just a phenol and an ArSO2F sitting in basic water reacting with each other. That's "click" chemistry finally earning its name in DEL work instead of just borrowing the marketing. High conversion with zero catalyst also means boring QC, in the best sense — fewer truncated/uncyclized side-populations polluting the pool means the hits you pull downstream are more likely real signal, not artifacts of your worst-yielding step. For macrocycles — the space between small molecules and biologics everyone wants but few can screen efficiently — a clean cyclization step is what lets you scale diversity without sacrificing quality. This is the unglamorous methods advance that keeps unlocking new DEL generations.