The Discovery and Characterization of Chemical Degraders of the Histone Methyltransferase NSD2

Epigenetics describes changes in chromosome and gene expression without alterations in the DNA sequence. Nuclear receptor-binding SET domain-containing 2 (NSD2) is a histone methyltransferase responsible for the formation of dimethylated lysine 36 on histone 3 (H3K36me2) – an epigenetic mark that is associated with chromatin regions of active transcription. For that, NSD2 plays a significant role in gene regulation. NSD2 dysregulation, caused by either a gain-of-function mutation (resulting in NSD2 hyperactivity) or a translocation (resulting in NSD2 overexpression), is associated with oncogenesis in blood cancers. However, there are only limited available effective and selective modulators of NSD2 activity. This thesis describes the development of the first-in-class NSD2 selective chemical degrader, UNC8153, which can reduce the cellular levels of NSD2 and the associated H3K36me2 mark. UNC8153 targets the non-catalytic PWWP1 domain of NSD2 and contains a simple primary alkylamine moiety that recruits a previously unexploited E3 ubiquitin ligase to confer neddylation-, ubiquitination- and proteosome-dependent degradation of NSD2. The degradation of NSD2 by UNC8153 results in reduced pathological phenotypes in multiple myeloma cells with dysregulated NSD2. Subsequent optimization of UNC8153 to UNC8732 by modifying its linker achieved five-times greater potency. UNC8732 facilitates targeted degradation of NSD2 in acute lymphoblastic leukemia cells harboring the NSD2 gain-of-function mutation, resulting in growth suppression, apoptosis, and reversal of drug resistance. Through a BioID-based proteomics approach, I shed light on the previously unknown mechanism of action by discovering a targeted protein degradation strategy involving the recruitment of the SCFFBXO22 E3 ubiquitin ligase complex. The primary amine of UNC8732 was shown to be metabolized to an aldehyde species, which engages cysteine 326 of FBXO22 covalently and reversibly to recruit the SCFFBXO22 complex. I also demonstrate that a previously reported alkyl amine-containing chemical degrader targeting XIAP similarly depends on the SCFFBXO22 complex, suggesting the broader applicability of this TPD strategy. Overall, this thesis describes the first chemical probe for modulating NSD2 activity, meeting the stringent criteria for potency, selectivity, and in-cell activity, as well as one of the first recruiters of FBXO22 E3 ubiquitin ligase. This marks significant achievements in NSD2-targeting therapeutics and targeted protein degradation.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.