Targeted protein degradation

F2Pmp warheads are notoriously charged and permeability-poor, so seeing real plasma exposure after IP dosing of a CRBN degrader built on one is the actual win here — event-driven pharmacology bailing out a classically undruggable phosphotyrosine mimetic. Also curious whether ternary-complex formation buys any PTP1B/TCPTP discrimination beyond what the near-identical catalytic sites let the warhead alone achieve.

Smarter to go after 'undruggable' mutant NRAS through the kinase that stabilizes it than to keep chasing the mutant protein directly, and a degrader — not a catalytic inhibitor — is what finally buys the CK1 paralog selectivity this target class has chronically lacked. Compound 8u reads like a real template, not just a tool compound to prove the hypothesis.

CK1δ/α/ε selectivity is the real fight here — those kinase domains are similar enough that classic ATP-competitive chemistry rarely holds up cleanly; if they're threading that needle with a degrader, ternary-complex geometry, not just binary affinity, is probably doing the selectivity work, which is the whole pitch for going bifunctional over yet another inhibitor. Smart use of event-driven pharmacology to reach something genuinely undruggable — NRAS has no covalent handle like G12C, so knocking down an upstream stabilizer is a legitimate end-run, not a gimmick. Still want to see the actual chemotype and E3 handle before getting excited — 'synthesized series, iterative SAR' tells me nothing about scaffold novelty or synthetic cost, and degrading a kinase with this many substrates makes me nervous about toxicity beyond the CK1α story. If selectivity and PK hold up in vivo, this is a template worth stealing for other 'stabilizer' targets propping up undruggable oncoproteins.

A degradation route that bypasses CRBN/VHL entirely is worth my attention regardless of target — CMA recruitment sidesteps the ubiquitin-proteasome toolbox, so it should be orthogonal to the resistance mechanisms (neosubstrate mutation, E3 downregulation) that kill PROTAC leads in the clinic. PD-L1 is the result I'd chase: pulling a membrane protein through chaperone-mediated autophagy via LAMP2A translocation is something UPS-based PROTACs structurally can't do. My skepticism sits with the Hsc70 arm — KFERQ-motif engagement is promiscuous by design, so selectivity and off-target chaperone-client disruption need real scrutiny before I trust the SAR. B-2's in vivo PK and clean BRD4 knockdown at least de-risks synthesis/linker chemistry enough to treat this as a platform, not just a proof of concept.

D4 clearing both the oral bioavailability and blood-brain-barrier bars is the real headline here, more than the VHL-EGFR chemistry itself — most VHL degraders are 800-1000 Da PEG-linked bricks, gorgeous in a dish, DOA as an oral CNS drug. That's the developability wall this class has been stuck at. C4's profile reads more like a conventional IV PROTAC: subnanomolar antiproliferative potency and regression at low twice-weekly doses is a solid therapeutic index, but the reduced dosing schedule signals they're still managing catalytic turnover and clearance, not solving it outright. Degrading Del19/L858R instead of inhibiting them sidesteps the secondary-mutation resistance that keeps eroding osimertinib responses. If selectivity holds against WT EGFR in vivo, this is a real next-gen chemotype for NSCLC, not just a mechanistic proof-of-concept.

Finally, a DAC that isn't just "ADC with a cooler payload" — swapping a cytotoxin for a VHL-PROTAC means efficacy doesn't hinge on brute-force poisoning of every internalized antibody; you get catalytic, event-driven target destruction instead. Smart target choice: COX-2 isn't the oncogenic driver, it's stromal plumbing. Cutting EV secretion to defuse tumor-fibroblast crosstalk instead of chasing EGFR resistance mutations directly is a genuinely different SAR logic than the usual "degrade the driver" playbook. Chemistry-wise, nothing exotic — indomethacin-COX-2 ligand, VHL peptide, cathepsin B-cleavable linker, defined-DAR bioorthogonal attachment. That's the point: boringly tractable, which is exactly what a translatable conjugation platform should look like. Real question is whether COX-2/EV silencing holds up in a fibroblast-rich, resistant tumor, not just a clean xenograft — but as a proof that microenvironment-directed degradation is maturing past a concept, this is convincing.

A monovalent degrader that's neither a classic PROTAC nor a molecular glue — that's the interesting bit. "Molecular crowbar" reads like marketing, but mechanistically it sounds like ligand-induced conformational destabilization exposing a degron: closer to hydrophobic-tag logic than E3-recruitment chemistry, no linker or ternary-complex engineering required. Chemically elegant, if it holds up. The real draw is that omaveloxolone's safety and PK are already banked — repurposing means skipping a decade of tox work if this translates. But my triage instinct says this is serendipitous polypharmacology, not designed SAR; the Nrf2 pharmacophore was never built for STING's pocket. It's also secondary-sourced with no primary structural data yet — I'd want a co-crystal or HDX-MS confirming direct engagement before trusting the crowbar story over generic proteostasis stress.

cMYC is the target every med chemist has scars from — decades of "undruggable" transcription-factor programs that went nowhere, so any credible new handle gets attention. What's genuinely useful here isn't the RIBOTAC concept itself but the linker SAR: length and rigidity dominating degradation efficiency is exactly the PROTAC linkerology lesson replaying in RNA-target space, and it's reassuring that the same design intuition transfers. That said, don't lose sight of the tractability problem — these are still bifunctional, comfortably-beyond-Ro5 molecules with the synthetic and PK baggage PROTACs never fully shook off. And the data are cell-based potency, not in vivo proof of concept; going from "degrades cMYC mRNA in a dish" to "a dosable, selective drug" is still the hard part nobody's solved for this target.

Three degron classes, one receptor — that's the headline for degrader hunters tired of CRBN/VHL. The Kelch channel reading C-terminal Arg is the most druggable-looking piece: Kelch domains (think KEAP1) have a track record of taking small, polar ligands into narrow grooves, so a compact peptidomimetic anchor there feels plausible. The acetyl-N-degron tunnel is murkier — adaptor-dependent, no small molecule has touched an acetyl-N-degron pocket yet, so that's fragment-screening territory, not a near-term glue. Biggest catch: MKLN1 self-dimerizes through the same discoidin-Kelch interface, meaning any exploiting ligand has to outcompete an endogenous, high-avidity PPI — selectivity and target engagement won't be trivial. Pure structural biology here, no chemical matter yet, but a legitimate new hub to diversify the E3 ligase toolbox beyond the same two receptors everyone's already crowded into.

The caged VHL ligand is the clever bit — redox-triggered decaging means the warhead sits as a prodrug until it hits oxidative-stress tissue, which could finally address the peripheral-toxicity problem that's dogged systemic PROTAC dosing. I want the counter-screen though: how much decaging leaks in non-lesion CNS tissue over chronic dosing, and does 'activated DAPK1' selectivity hold in human proteoform or is that mouse-conformer-specific? The macrocyclic peptide-small molecule hybrid is a brutal synthesis — SPPS, macrocyclization, PROTAC conjugation, yield bleeding at every step — this is proof-of-concept, not a scalable series. Exploiting age-upregulated transcytosis instead of fixed RMT receptors (transferrin, insulin) is the real advance over TfR-shuttle degraders; the open question is whether that route is druggable across disease stages, not just aged models.

WBP4 is a spliceosome scaffold with no ligandable pocket — this isn't a kinase-with-a-degron-tail story, it's proof CRBN can be steered onto a genuinely undruggable surface via a G-loop contact. That binding hypothesis is worth stealing for other scaffold targets sitting in my own tractability triage pile. The selectivity data is the real flex: clean proteome-wide profile AND minimal splicing perturbation, exactly where glues usually get you in trouble (neosubstrate promiscuity, cryptic RBM39-style splicing hits). Getting both together is rare. wTAG might matter more than the degrader itself — a 41-residue portable degron with no hook effect is a cleaner dTAG-class tool, and I'd rather have that in my assay toolbox than another single-target lead.

A canonical G-loop-mediated ternary complex — reassuring, not exotic: this is the same validated CRBN surface, not a new liability profile to characterize from scratch. The compact ~41-residue degron is the real tell for tractability — that's a defined element, not a diffuse IDR, so SAR here should be rational rather than lucky. Nanomolar potency with reported high proteome-wide selectivity is the headline number, though for a spliceosome-associated protein I'd want orthogonal splicing/transcriptomic data before fully trusting "minimal downstream effects." The piece I'd actually chase into my own work is wTAG: a monovalent, hook-effect-free degron tag beats dTAG-style bifunctional systems for clean dose-response in target-validation studies, regardless of whether WBP4 itself ever becomes a drug target.

Smart move folding the VHL ligand and linker into a bifunctional amino acid for direct SPPS incorporation — that sidesteps the PEGylation/conjugation bottleneck that makes cyclic peptide degraders such a pain to iterate on, and it turns linker SAR into a synthesis-cycle variable instead of a separate coupling step. The SICLOPPS-derived warhead is a nice proof that a cyclic peptide can grip a transcription-factor surface a small molecule can't easily touch, so on chemotype comparison this favors the peptide side. But the real flag for my own work is the hypoxia dropout: ternary complex still forms, HIF-1α still gets marked, degradation just can't keep up. That's not a binding problem I'd fix by optimizing the VHL warhead — it's a turnover-rate problem, and it says something uncomfortable about any PROTAC campaign against a target with fast resynthesis kinetics.

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.

Locking down the non-productive Kalirin-Rac1 complex rather than competing head-on for the nucleotide pocket is the smarter play — GTP/GDP affinity is sub-nanomolar, and pan-Rac1 nucleotide-pocket tools like NSC23766 have never been clean. It's the SOS1-KRAS playbook applied to Rho biology, not a new idea, but a good one to borrow. Selectivity across GEF-GTPase pairs is the actual prize, not a burden — Rho-family homology is brutal, so an interface-driven selectivity handle beats trying to differentiate active-site chemistry. What I'd interrogate: fragment merging from XChem hits into covalent leads has a high attrition rate, so two validated compounds (RS-009, MC-278) is a real result, not a given. Before calling these clean probes I want warhead kinetics and full-proteome ABPP, not just the GEF-GTPase panel.

TRI-611 recruiting cereblon to a distinct, non-canonical surface on ALK — rather than working off the usual IMiD-derived degron — is the real chemistry story here; if that ternary interface holds up, it's a fresh template for kinases that don't glue easily. Wiping out kinase-inhibitor-resistant fusion variants is the killer selling point: degradation doesn't care about the affinity losses that gatekeeper/compound mutations inflict on ATP-competitive binders, so a mutant that's dead to a TKI can still form a productive ternary complex. Getting CNS exposure out of a CRBN glue is the harder chemical win — these scaffolds usually sit well outside Ro5, so brain penetrance without sacrificing ternary complex cooperativity argues for real optimization, not luck. Selectivity over other CRBN neosubstrates plus the TKI-combo data suggest this could slot in alongside inhibitors rather than just after them.

The move that catches my eye: folding the CRBN ligand into the HDAC8 warhead's capping group instead of bolting on a full separate E3 unit plus linker. That's a direct attack on the MW/logP bloat that tanks oral exposure in most heterobifunctional degraders — not incremental linker trimming, a structural collapse of the whole ternary-complex scaffold. Going from YX862 to these analogs with better selectivity AND lower MW (rarely a package deal) says the capping vector is actively shaping the HDAC8–CRBN interface, not just shedding atoms. In vivo degradation data is the sanity check I always want before trusting a compact-PROTAC claim. I'd want SAR around that fused cap next — how much substituent tolerance before CRBN engagement drops off. Feels like a real template for smaller, more drug-like degraders, not just this target.

A single tert-butyl group turning thalidomide into a ZF8-selective glue is the kind of result that makes you go back and stare at your own IMiD SAR data — this is minimal medicinal chemistry, not a redesigned scaffold, and that's the exciting part. The real puzzle is why one finger out of eleven degron-competent copies wins. If the ternary-complex modeling holds up, this is a rare case where computation actually explains selectivity instead of rationalizing it after the fact. IMiD-class glues have a promiscuity problem — off-target zinc fingers are exactly how thalidomide's teratogenicity got explained via SALL4. A route to finger-specific engagement is the fix chemists have wanted since that story broke. I'd want a neosubstrate panel run immediately: does 5-tBu still hit SALL4/IKZF1/GSPT1, or did this substitution buy clean selectivity for free? That answer decides whether this is a platform or a one-off.