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PIPELINE > TRIAL OVERVIEW

Trial Information
Molecule Overview
Pan-Mutant Selective PI3Kα Inhibitor
LY4064809 (STX-478)
pan-mutant selective PIKα

Vasan N, et al1; Engelman JA, et al2; Dirican E, et al3

Target

Phosphoinositide 3-kinase alpha (PI3Kα) molecules harboring activating PIK3CA mutations are oncogenic drivers found in approximately 40% of hormone receptor positive (HR+)/HER2-negative breast cancers and less commonly in other cancers.3,4  The most common mutations include H1047R in the kinase domain, and E545K and E542K in the helical domain.4,5 Alterations in the PI3K signaling pathway have been associated with endocrine therapy resistance in metastatic breast cancer.6 

Molecule
LY4064809 (STX-478) is a mutant-selective, allosteric PI3Kα inhibitor.  It has shown preclinical activity in PI3Kα kinase and helical domain mutant driven breast cancer models.7
Clinical Development

LY4064809 is being studied in patients with HR+ breast cancer and other solid tumors with PIK3CA mutations.8

References

  1. Vasan N, et al. Ann Oncol. 2019;30(Suppl_10):x3-x11.
  2. Engelman JA, et al. Nat Rev Genet. 2006;7(8):606-619. 
  3. Dirican E, et al. Tumor Biol. 2016;37(6):7033-7045.
  4. Martinez-Saez O, et al. Breast Cancer Res. 2020;22(1):45.
  5. Zhao L, Vogt PK. Proc Natl Acad Sci U S A. 2008;105(7):2652-2657.
  6. Tokunaga E, et al. Breast Cancer. 2006;13(2):137-144.
  7. Buckbinder L, et al. Cancer Discov. 2023;13(11):2432-2447. 
  8. First-in-Human Study of STX-478, a Mutant-Selective PI3Kα Inhibitor as Monotherapy and in Combination With Other Antineoplastic Agents in Participants With Advanced Solid Tumors. Clinicaltrials.gov Identifier: NCT05768139. Updated March 25, 2025. Accessed March 31, 2025. https://www.clinicaltrials.gov/study/NCT05768139
For information on trial enrollment, locations, and more, call 1-800-545-5979.
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