Prelude Therapeutics Enters Clinical Trial Collaboration And Supply Agreement With Eli Lilly For Supply Of Its CDK4/6 Kinase Inhibitor, Abemaciclib And Its Oral Estrogen Receptor Antagonist Imlunestrant

The agreement supports the evaluation of Prelude’s clinical development candidate PRT13722, an oral KAT6A selective degrader, in combinations with abemaciclib and imlunestrant in a Phase 1 trial in patients with HR+/HER2- breast cancer.

The U.S. Food and Drug Administration (FDA) recently cleared the Company to proceed with the Phase 1 study under its Investigational New Drug (IND) Application for PRT13722. The Company expects to begin enrolling patients in the fourth quarter of 2026 beginning with monotherapy dose escalation and rapidly advancing to various combination cohorts.

At the American Association for Cancer Research (AACR) 2026 Annual Meeting in April of this year, Prelude presented preclinical data that demonstrated PRT13722, by selectively degrading KAT6A, drives more complete disruption of the KAT6A regulatory pathways than dual KAT6A/B inhibitors, resulting in more robust depth and breadth of efficacy across HR+/HER2- breast cancer models. Additionally, PRT13722 drove durable complete tumor regressions in HR+/HER2- CDX and PDX xenograft models (both endocrine therapy naive and experienced) at well tolerated doses, as a monotherapy. In combinations with endocrine therapy, CDK4/6 inhibitors and PI3K inhibitors, PRT13722 demonstrated synergy while maintaining monotherapy and combination activity across HR+ breast cancer models, including ESR1 mutated and acquired therapy-resistant cancer cells. PRT13722 also demonstrated preclinically an improved hematological safety profile compared to the KAT6A/B dual inhibitor prifetrastat, which may enable combinations with standard of care agents used in the frontline treatment of metastatic and early-stage HR+/HER2- breast cancer.

Prelude maintains full global development and commercial rights to PRT13722 as a wholly owned program.

Highly selective KAT6A oral degrader program

KAT6 is an emerging and clinically validated target in the treatment of HR+ breast cancer. Prelude discovered and is developing first-in-class, highly potent, highly selective and orally bioavailable KAT6A degraders. Prelude believes that selectively degrading KAT6A and sparing KAT6B has the potential for improved efficacy, tolerability and combinability with other agents relative to dual inhibitors of KAT6A/B.