ALK-positive NSCLC arises when a chromosomal rearrangement fuses the ALK kinase gene to a partner gene, most commonly EML4, producing a constitutively active signaling protein that drives uncontrolled proliferation. Since the first ALK inhibitor, crizotinib, entered the clinic, a succession of increasingly potent tyrosine kinase inhibitors (TKIs) has transformed outcomes for these patients. The latest generation agent, lorlatinib, demonstrated durable benefit in the phase III CROWN study. Yet resistance remains an inevitability for many patients. ALK’s kinase domain is a mutable target, and sequential treatment with TKIs selects for compound mutations that no drug approved to date can fully suppress. Patients who progress on available TKIs have limited options, a gap the authors identify as the central motivation for an orthogonal therapeutic approach.

Targeted protein degradation offers such an approach. Rather than blocking an enzyme’s active site, degraders eliminate the target protein altogether, harnessing the ubiquitin-proteasome system that cells use for routine protein turnover. Two broad strategies exist. Proteolysis-targeting chimeras, or PROTACs, are large bifunctional molecules that physically tether a target protein to an E3 ubiquitin ligase. Molecular glue degraders, by contrast, are typically smaller, more drug-like compounds that bind the E3 ligase substrate receptor and remodel its surface to recognize a neosubstrate. Their smaller size confers potential advantages in oral bioavailability and tissue penetration, but discovering glues for a chosen target has historically been a matter of luck rather than design, because the interaction is not obvious from sequence alone.

The Triana team found TRI-611 through a deliberate engineering effort. Using a time-resolved fluorescence resonance energy transfer screen that reports when ALK and cereblon (CRBN), the substrate adaptor of the CRL4 ubiquitin ligase complex, are brought into proximity, the researchers identified an initial hit compound and then optimized it for potency, selectivity and drug-like properties. Structural and biophysical work, including cryo-electron microscopy of the ternary complex, revealed that TRI-611 operates through a distinctive mechanism. The glue promotes contact between the ALK kinase domain and CRBN through a degron interface positioned distal to the kinase active site. This arrangement matters for two reasons: the drug does not need to compete with ATP at a mutation-prone catalytic pocket, and its binding surface tolerates mutations that disable orthosteric inhibitors.

That structural feature translates directly into resistance coverage. In engineered cell lines and patient-derived models, TRI-611 degraded not only wild-type EML4-ALK but also versions carrying clinically important TKI-resistance mutations, including the gatekeeper mutation L1196M and the solvent-front mutation G1202R, individually and in combination. Biochemical assays demonstrated that the drug supported ubiquitin transfer onto the mutant kinase domain by the CRBN-containing ligase complex, and degradation potency correlated tightly with anti-proliferative activity across a panel of resistant lines. Proteomic profiling after TRI-611 treatment showed a remarkably clean footprint: among thousands of quantified proteins, ALK fusion proteins were selectively depleted, with minimal effects on known CRBN neosubstrates or other kinases. In an era when glue degraders are often criticized for promiscuous neosubstrate recruitment, that selectivity is a notable technical achievement.

The pharmacology was engineered with the brain in mind. ALK-positive NSCLC has a notorious tendency to metastasize to the central nervous system, and the blood-brain barrier excludes many otherwise effective drugs, making brain metastases a frequent site of progression. Guided by central nervous system multiparameter optimization principles, the team tuned the compound’s permeability and efflux properties. In mice, TRI-611 achieved brain-to-plasma exposure ratios comparable to lorlatinib, a benchmark for brain penetration, and unbound brain concentrations exceeded the levels needed for target degradation. Once-daily oral dosing produced regressions of subcutaneous xenografts derived from both cell lines and patients, including the DFCI-669 model and the MGH953-7 patient-derived model, the latter harboring TKI-resistance mutations. Critically, intracranial xenograft models, including one driven by the doubly resistant L1196M/G1202R mutant, also responded, with luminescence-based tumor measurements showing marked shrinkage in treated animals.

Perhaps the most clinically provocative finding concerns combination therapy. Because TRI-611 binds the kinase domain at a surface remote from the ATP pocket, it does not interfere with orthosteric TKIs, and the two modalities can be used together. In vitro, the combination of TRI-611 with alectinib or lorlatinib produced greater-than-additive killing of ALK-dependent cells, quantified by Bliss synergy analysis. In vivo, pairing the degrader with lorlatinib yielded synergistic and durable tumor regressions in subcutaneous and intracranial models, outperforming either agent alone. The logic is compelling: the TKI suppresses signaling immediately while the glue removes the protein irreversibly, and degrading the target may suppress the evolutionary escape routes that kinase inhibition alone leaves open. The combination also addresses a second resistance mechanism, MET amplification, which can bypass ALK entirely; pairing TRI-611 with a MET inhibitor such as capmatinib restored growth control in MET-overexpressing models.

The study is thorough on the mechanistic details that regulators and clinicians will want. Degradation required the proteasome, as shown by rescue experiments with bortezomib, and was enhanced by CRBN overexpression, confirming the ligase dependence of the effect. Treated tumors showed loss of phosphorylated STAT3, a downstream readout of ALK signaling, within hours of dosing, linking pharmacokinetics to pharmacodynamics. Structural biology pinned the molecular determinants: mutation of a key ALK residue in the degron interface, D1389W, abolished both degradation and the compound’s anti-proliferative effect, demonstrating that the observed binding mode is causally responsible for the biology. Cryo-EM maps and a deposited crystal structure provide a template that other groups can mine for the emerging rules of glue-induced neosubstrate recognition.

Caveats remain, as they always do at the preclinical-to-clinical boundary. The efficacy data come from xenograft and cell-line models rather than patients, and the long-term consequences of chronically eliminating ALK, which has physiological roles outside cancer, will need careful toxicological evaluation. The authors note that their work was conducted by employees of Triana Biomedicines, with a patent covering TRI-611 filed by the company, and the compound’s clinical profile will ultimately be decided in human trials. Still, the bar this molecule clears is high: potent, selective, orally bioavailable, brain-penetrant degradation of a validated oncogenic driver, active against the resistance mutations that defeat today’s best drugs, and compatible with rational combinations. If the clinical experience mirrors the preclinical one, TRI-611 could mark the moment molecular glue degraders graduated from the lab bench to a front-line role against gene-fusion-driven cancers, and the strategy of degrading rather than inhibiting oncogenic kinases may rapidly expand beyond ALK.

Subject of Research: A selective, brain-penetrant molecular glue degrader of ALK fusion proteins for ALK-positive non-small-cell lung cancer

Article Title: TRI-611, a selective, brain-penetrant molecular glue degrader of ALK

Article References: Conery, A. R., La, D. S., Alekseyenko, A. A., Marcoux, D., Bart, A. G., Harlow, M. L., Arsenault, P. R., Cantone, N. R., Casaubon, R. L., Constan, A., Kamadurai, H. B., Medikonda, A. P., Nunes, D. E., Szeto, H., Wigle, T. J., Yu, M., Zagulyaeva, A., Zarate, C. M., Highfield, L., … Palombella, V. J. (2026). TRI-611, a selective, brain-penetrant molecular glue degrader of ALK. Nature. https://doi.org/10.1038/s41586-026-10998-3

Image Credits: AI Generated

DOI: 10.1038/s41586-026-10998-3

Keywords: ALK, TRI-611, molecular glue degrader, non-small-cell lung cancer, targeted protein degradation, cereblon, EML4-ALK, TKI resistance, brain penetration, lorlatinib, oncogenic fusion, drug discovery