TNG961 Is a Selective Oral HBS1L Molecular Glue Degrader for the Treatment of FOCAD-Deleted Cancers.

When tumor suppressor genes are lost through chromosomal deletion, the deletion of adjacent genes can generate therapeutic vulnerabilities. MTAP is frequently co-deleted with the chr9p21 tumor suppressor gene CDKN2A, creating a synthetic lethal dependency on protein arginine methyltransferase 5 (PRMT5). Telomeric to MTAP lies focadhesin (FOCAD), whose loss induces dependency on the HBS1-like translational GTPase (HBS1L)-protein pelota homolog (PELO) ribosome rescue complex for translational maintenance. FOCAD is deleted in ∼1 out of 3 MTAP-deleted cancers. We screened an immunomodulatory imide drug (IMiD)-focused diversity library and identified a weak hit that bound cereblon (CRBN), promoted HBS1L-CRBN-compound complex formation, and induced E3-ligase-dependent HBS1L ubiquitination and degradation. Guided by cryo-EM structures and proteome selectivity, we developed TNG961, a potent, selective HBS1L degrader that disrupts the HBS1L-PELO complex, inducing translational arrest, unfolded protein response activation, and growth inhibition in FOCAD-negative models. Oral administration of TNG961 regresses FOCAD-negative xenografts, including PRMT5 inhibitor-refractory models, establishing HBS1L degradation as a strategy to exploit FOCAD loss and supporting the clinical evaluation of TNG961 as a first-in-class precision oncology therapeutic. SIGNIFICANCE: FOCAD deletion, frequently co-occurring with MTAP/CDKN2A loss, creates a synthetic lethal dependency on the HBS1L-PELO ribosome rescue complex. TNG961, a first-in-class molecular glue degrader of HBS1L, enforces translational arrest and drives tumor regressions in FOCAD-negative models, including PRMT5 inhibitor-refractory tumors, establishing a novel precision oncology strategy for chromosome 9p21 co-deletion contexts.