Zelebrudomide

Zelebrudomide is an orally bioavailable chimeric targeting molecule (CTM) and targeted degrader of Bruton's tyrosine kinase (BTK), with potential immunomodulatory drug (IMiD) and antineoplastic activities. Zelebrudomide is comprised of a cereblon (CRBN)-binding moiety conjugated, via a linker, to a BTK-binding moiety. Upon administration, zelebrudomide targets and binds to BTK with its BTK-targeting moiety. Upon binding, the CRBN-binding moiety recruits CRBN, a component of the CRL4-CRBN E3 ubiquitin ligase complex. This catalyzes ubiquitination and proteasome-mediated degradation of BTK, and prevents the activation of the B-cell antigen receptor (BCR) signaling pathway. This prevents both B-cell activation and BTK-mediated activation of downstream survival pathways. This leads to an inhibition of the growth of malignant B-cells that overexpress BTK. In addition, zelebrudomide catalyzes the degradation of CRBN neosubstrates Aiolos (IKZF3) and Ikaros (IKZF1), two transcription factors regulating T-cell function. This modulates the activity of the immune system and increases the activation of T-lymphocytes, thereby increasing T-cell-mediated anti-tumor effects. BTK, a member of the src-related BTK/Tec family of cytoplasmic tyrosine kinases, is overexpressed in B-cell malignancies; it plays an important role in B-lymphocyte development, activation, signaling, proliferation and survival. CRBN, the substrate recognition component of the CRL4-CRBN E3 ubiquitin ligase complex, plays a key role in the ubiquitination of certain proteins. Compared to BTK inhibitors, zelebrudomide may overcome tumor resistance associated with BTK inhibitor-induced resistance mutations.