Preclinical characterization of a potent and selective Werner helicase (WRN) inhibitor with activity in low-TA repeat microsatellite instability-high (MSI-H) cancers
Presenter: Pablo Hollstein, PhD Session: Novel Antitumor Agents 3 Time: 4/22/2026 9:00:00 AM → 4/22/2026 12:00:00 PM
Authors
Pablo E. Hollstein 1 , Daniel A. Aiello 1 , Anne Y. Saiki 1 , Keegan S. Cooke 1 , Petia Mitchell 1 , Xiang Yi 2 , Ishwar N. Kohale 3 , Matthew J. Rardin 3 , John Rodgers 4 , Mauro Poggio 5 , Chun Su 6 , Sigurgeir Ólafsson 7 , Doruk Beyter 7 , Jennifer A. Roth 8 , Nuria A. Tamayo 9 , Kevin L. Greenman 9 , Andrew J. Holland 1 , Paul E. Hughes 1 1 Oncology Research, Amgen, Inc., Thousand Oaks, CA, 2 LD&TPD, Amgen, Inc., South San Francisco, CA, 3 Discovery Proteomics, Amgen, Inc., South San Francisco, CA, 4 PKDM-BA, Amgen, Inc., South San Francisco, CA, 5 Precision Medicine, Amgen, Inc., South San Francisco, CA, 6 Automation, Research data systems, Informatics & AI (ARIA), Amgen, Inc., South San Francisco, CA, 7 Amgen deCODE Genetics, Amgen, Inc., Reykjavik, Iceland, 8 Broad Institute, Cambridge, MA, 9 Small Molecule Therapeutic Discovery, Amgen, Inc., Thousand Oaks, CA
Abstract
Werner syndrome helicase (WRN), a member of the RecQ family of DNA helicases, is a synthetic-lethal dependency in DNA mismatch repair-deficient cancers that exhibit high microsatellite instability (MSI-H). Here, we characterize Compound 1, a potent and selective small molecule WRN inhibitor. Compound 1 binds within an allosteric pocket in the helicase domain of WRN and forms an irreversible covalent interaction with cysteine 727 (C727), a residue not conserved in other RecQ helicases. In vitro , Compound 1 potently inhibited WRN’s helicase activity and was confirmed to be a highly selective covalent inhibitor of WRN C727 by mass spectrometry-based cysteine profiling in human MSI-H cancer cells. Consequently, Compound 1 potently impacted the viability of a broad panel of MSI-H cell lines, including colorectal SW48 and RKO (IC50 = In vivo , Compound 1 treatment resulted in a dose-dependent modulation of PD biomarkers, which correlated with strong anti-tumor efficacy in SW48, RKO, and TOV-21G MSI-H cell line-derived xenograft (CDX) models. Covalent engagement of WRN by Compound 1 was measurable in tumor tissue and in peripheral blood monocytes. The exposure and target occupancy of Compound 1 required for efficacy strongly correlated with the expansion of repetitive thymine-adenine (TA) nucleotide DNA microsatellites. These repeats form non-canonical secondary structures that interfere with DNA replication in MSI-H cells and require unwinding by WRN. Long-read DNA sequencing confirmed that the extent of TA-repeat expansion was associated with Compound 1 activity in MSI-H CDX models. An analysis of primary MSI-H tumor cohorts revealed that the majority of patient tumor samples exhibited TA-repeat expansions within the range of Compound 1 efficacy observed in cell-based models. Importantly, dosing of Compound 1 was sufficient to elicit tumor regression in low-TA repeat CDX MSI-H models (RKO, TOV-21G), which have proven to be refractory to WRN inhibitors advanced previously. Together, these data demonstrate that covalent inhibition of WRN by Compound 1 is an effective strategy to selectively kill MSI-H tumor cells with expanded TA repeats.
Disclosure
P. E. Hollstein, Amgen, Inc. Employment, Stock. D. A. Aiello, Amgen, Inc. Employment, Stock. A. Y. Saiki, Amgen, Inc. Employment, Stock. K. S. Cooke, Amgen, Inc. Employment, Stock. P. Mitchell, Amgen, Inc. Employment, Stock. X. Yi, Amgen, Inc. Employment, Stock. I. N. Kohale, Amgen, Inc. Employment, Stock. M. J. Rardin, Amgen, Inc. Employment, Stock. J. Rodgers, Amgen, Inc. Employment, Stock. M. Poggio, Amgen, Inc. Employment, Stock. C. Su, Amgen, Inc. Employment, Stock. S. Ólafsson, Amgen, Inc. Employment, Stock. D. Beyter, Amgen, Inc. Employment, Stock. J. A. Roth, None. N. A. Tamayo, Amgen Employment, Stock. K. L. Greenman, Amgen, Inc. Employment, Stock. A. J. Holland, Amgen, Inc. Employment, Stock. P. E. Hughes, Amgen, Inc. Employment, Stock.
Cited in
Control: 5327 · Presentation Id: 8850 · Meeting 21436