American Association for Cancer Research
00085472can191236-sup-220875_2_supp_5624137_pl1k0f.xlsx (58.63 kB)

Supplementary Data from Targeting BCR-ABL1 in Chronic Myeloid Leukemia by PROTAC-Mediated Targeted Protein Degradation

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posted on 2023-03-31, 02:24 authored by George M. Burslem, Anna Reister Schultz, Daniel P. Bondeson, Christopher A. Eide, Samantha L. Savage Stevens, Brian J. Druker, Craig M. Crews

Table S1 - Reverse phase protein array data for K562 cells treated with GMB-475 or GMB-651.


Leukemia and Lymphoma Society





Although the use of ATP-competitive tyrosine kinase inhibitors of oncoprotein BCR-ABL1 has enabled durable responses in patients with chronic myeloid leukemia (CML), issues of drug resistance and residual leukemic stem cells remain. To test whether the degradation of BCR-ABL1 kinase could offer improved response, we developed a series of proteolysis-targeting chimera (PROTAC) that allosterically target BCR-ABL1 protein and recruit the E3 ligase Von Hippel-Lindau, resulting in ubiquitination and subsequent degradation of the oncogenic fusion protein. In both human CML K562 cells and murine Ba/F3 cells expressing BCR-ABL1, lead compound GMB-475 induced rapid proteasomal degradation and inhibition of downstream biomarkers, such as STAT5, and showed increased sensitivity compared with diastereomeric controls lacking degradation activity. Notably, GMB-475 inhibited the proliferation of certain clinically relevant BCR-ABL1 kinase domain point mutants and further sensitized Ba/F3 BCR-ABL1 cells to inhibition by imatinib, while demonstrating no toxicity toward Ba/F3 parental cells. Reverse phase protein array analysis suggested additional differences in levels of phosphorylated SHP2, GAB2, and SHC associated with BCR-ABL1 degradation. Importantly, GMB-475 reduced viability and increased apoptosis in primary CML CD34+ cells, with no effect on healthy CD34+ cells at identical concentrations. GMB-475 degraded BCR-ABL1 and reduced cell viability in primary CML stem cells. Together, these findings suggest that combined BCR-ABL1 kinase inhibition and protein degradation may represent a strategy to address BCR-ABL1–dependent drug resistance, and warrant further investigation into the eradication of persistent leukemic stem cells, which rely on neither the presence nor the activity of the BCR-ABL1 protein for survival. Small-molecule–induced degradation of BCR-ABL1 in CML provides an advantage over inhibition and provides insights into CML stem cell biology.

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