Prelude Announces Clinical Trial Collaboration and Supply Agreement with Lilly to Evaluate KAT6A Selective Degrader PRT13722 in Combination with Verzenio® and Inluriyo® in Patients with HR+/HER2- Breast Cancer

Combination cohorts are part of Prelude’s Phase 1 trial evaluating PRT13722 in patients with HR+/HER2- breast cancer, on track to initiate enrollment in the fourth quarter of 2026

The collaboration is underpinned by pre-clinical data that demonstrate monotherapy efficacy for PRT13722 and synergy with both CDK4/6 inhibitors and endocrine therapies across multiple HR+ breast cancer models

WILMINGTON, Del., Oct. 13, 2026 (GLOBE NEWSWIRE) -- Prelude Therapeutics Incorporated (Nasdaq: PRLD), a precision oncology company, today announced a clinical trial collaboration and supply agreement with Eli Lilly and Company (“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.

“This collaboration with Lilly enables us to evaluate the potential of PRT13722 in combinations with abemaciclib and imlunestrant in patients with HR+ breast cancer,” stated Sean Brusky, Chief Business & Strategy Officer of Prelude. “We are taking a highly differentiated approach to this clinically validated target. Our preclinical data demonstrate that selectively degrading KAT6A has the potential to improve upon the efficacy and hematologic toxicity seen with dual KAT6A/B inhibitors, thereby enabling combination approaches that could advance the standard of care in earlier lines of therapy. We are pleased to be partnering with Lilly, recognized global leaders in breast cancer, to generate these important data for patients.”

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.

About Prelude Therapeutics
Prelude Therapeutics is a leading precision oncology company developing innovative medicines in areas of high unmet need for cancer patients. Our pipeline features highly selective KAT6A degraders and JAK2V617F mutant selective inhibitors -- new approaches to clinically validated targets with transformative potential for patients. We are leveraging our expertise in targeted protein degradation to create and develop next generation degrader antibody conjugates (DACs) with novel payloads. We are on a mission to extend the promise of precision medicine to every cancer patient in need. For more information, visit preludetx.com.

Cautionary Note Regarding Forward-Looking Statements 
This press release contains forward-looking statements within the meaning of the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995, including, but not limited to, anticipated discovery, preclinical and clinical development activities for Prelude’s product candidates, the potential safety, efficacy, benefits and addressable market for Prelude’s product candidates, the expected timeline for clinical trial results for Prelude’s product candidates, and the sufficiency of Prelude’s cash runway. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. The words “believes,” “anticipates,” “estimates,” “plans,” “expects,” “intends,” “may,” “could,” “should,” “potential,” “likely,” “projects,” “continue,” “will,” “schedule,” and “would” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. These forward-looking statements are predictions based on the Company’s current expectations and projections about future events and various assumptions. Although Prelude believes that the expectations reflected in such forward-looking statements are reasonable, Prelude cannot guarantee future events, results, actions, levels of activity, performance or achievements, and the timing and results of biotechnology development and potential regulatory approval is inherently uncertain. Forward-looking statements are subject to risks and uncertainties that may cause Prelude's actual activities or results to differ significantly from those expressed in any forward-looking statement, including risks and uncertainties related to Prelude's ability to advance its product candidates, the receipt and timing of potential regulatory designations, approvals and commercialization of product candidates, clinical trial sites and our ability to enroll eligible patients, supply chain and manufacturing facilities, Prelude’s ability to maintain and recognize the benefits of certain designations received by product candidates, the timing and results of preclinical and clinical trials, Prelude's ability to fund development activities and achieve development goals, Prelude's ability to protect intellectual property, and other risks and uncertainties described under the heading "Risk Factors" in Prelude’s Annual Report on Form 10-K for the year ended December 31, 2025, its Quarterly Reports on Form 10-Q and other documents that Prelude files from time to time with the Securities and Exchange Commission. These forward-looking statements speak only as of the date of this press release, and Prelude undertakes no obligation to revise or update any forward-looking statements to reflect events or circumstances after the date hereof, except as may be required by law.

Investor Contact:
Robert A. Doody, Jr.
Senior Vice President, Investor Relations
Prelude Therapeutics Incorporated
484.639.7235
rdoody@preludetx.com