SUZHOU, China, March 14, 2024 /PRNewswire/ — Kintor Pharmaceutical Limited (“Kintor Pharma“, HKEX: 9939.HK), a clinical-stage biotechnology company developing innovative small molecule and biological therapeutics, announces that Kintor and its cooperative partner had published an article named MYC Induces CDK4/6 Inhibitors Resistance by Promoting pRB1 Degradation in a subsidiary journal of NatureNature Communications (Impact factor: 16.6). Nature Communications is one of the top journals in biology field and is classified as Q1 in several categories, representing a leading research level in the world. The study shows that target c-Myc molecular glue compound has great potential, which could provide more directions for overcoming resistance issues of CDK4/6 inhibitors in various tumor fields.

Issue:

This article analyzes the mechanism of c-Myc that induces CDK4/6 inhibitors resistance and introduces A80.2HCl, a promising molecular glue compound developed by Kintor Pharma, to enhance the therapeutic efficacy of CDK4/6 inhibitors.

Background:

CDK4 and CDK6 (CDK4/6) govern progression through the early G1 phases of the cell cycle, and they have shown profound effects against several solid tumors. CDK4/6 inhibitors (CDK4/6i) have been approved for the treatment of hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast cancer. However, their application to other tumor types and intrinsic resistance mechanisms are still unclear. Existing mechanism studies have shown that the loss of normal RB1 function is the most frequently observed change in cells resistant to CDK4/6i. MYC is one of the most widely investigated oncoproteins that regulates many cellular processes and contributes to tumorigenesis and therapeutic resistance in several different cancer types. This article analyzes the mechanism of MYC that induces CDK4/6 inhibitors resistance by promoting pRB1 degradation and introduces a c-Myc degrader A80.2HCl, a promising molecular glue compound developed by Kintor Pharma, to enhance the therapeutic effectiveness of CDK4/6 inhibitors.

Results:

  • High MYC expression drives resistance to CDK4/6i by masking pRB1
  • High MYC expression reduces pRB1 abundance via proteasomal degradation
  • The E3 ubiquitin ligase KLHL42 interacts with pRB1 and induces pRB1 proteasomal degradation
  • KLHL42 is a transcriptional target of MYC that mediates CDK4/6i resistance
  • Identification of A80.2HCl as a MYC-degrading molecule
  • A80.2HCl potentiates the therapeutic efficacy of CDK4/6 inhibitors

Conclusion:

  • High MYC expression drives resistance to CDK4/6i by directly activating the transcription of the E3 ubiquitin ligase KLHL42, which promotes pRB1 ubiquitination and degradation and thus leads to pRB1 protein deficiency
  • A molecule that degrades MYC, A80.2HCl, developed by Kintor Pharma, to abolish MYC when applied at nanomolar levels, rescues pRB1 protein activity, and diminishes MYC-dependent CDK4/6i resistance
  • The combination of CDK4/6i and MYC-degrading molecule A80.2HCl shows an additive effect on killing tumor cells both in vitro and in vivo

Full article

The full article is available in Nature Communications.
Download: https://www.nature.com/articles/s41467-024-45796-w