Prelude Therapeutics Teams Up With Lilly To Test Experimental Breast Cancer Drug In Phase 1 Trial

• Under the agreement, Lilly will supply abemaciclib, marketed as Verzenio, and Imlunestrant, marketed as Inluriyo.
• The Phase 1 trial will evaluate combinations of PRT13722, an oral KAT6A selective degrader, with these medicines in patients with hormone receptor-positive, HER2-negative (HR+/HER2-) breast cancer.
• The FDA cleared Prelude to proceed with the study under its Investigational New Drug (IND) application.

Prelude Therapeutics (PRLD) announced a clinical trial collaboration and supply agreement with Eli Lilly and Company (LLY) on Tuesday to evaluate its experimental breast cancer drug PRT13722 in combination with two Lilly medicines.

At the time of writing, PRLD shares were down more than 7%, while LLY shares traded 1.5% lower. The iShares Biotechnology ETF (IBB) declined over 1.5%.

What Does The Lilly Collaboration Involve?

Under the agreement, Lilly will supply Abemaciclib, marketed as Verzenio, and Imlunestrant, marketed as Inluriyo. The Phase 1 trial will evaluate combinations of PRT13722, an oral KAT6A selective degrader, with these medicines in patients with hormone receptor-positive, HER2-negative (HR+/HER2-) breast cancer.

The FDA cleared Prelude to proceed with the study under its Investigational New Drug (IND) application. The company expects enrollment to begin in the fourth quarter of 2026, starting with monotherapy dose escalation before advancing to combination cohorts.

Sean Brusky, Prelude’s chief business and strategy officer, said: “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.” He added that the approach could enable combination treatments that may advance the standard of care in earlier lines of therapy.

What Has Prelude Reported About PRT13722?

At the American Association for Cancer Research (AACR) 2026 Annual Meeting in April, Prelude presented preclinical data showing that PRT13722 produced durable complete tumor regressions as a monotherapy in HR+/HER2- breast cancer cell-line-derived and patient-derived xenograft models at well-tolerated doses.

The company also reported synergy when PRT13722 was combined with endocrine therapies, CDK4/6 inhibitors and PI3K inhibitors across HR+ breast cancer models, including ESR1-mutated and acquired therapy-resistant cancer cells.

Prelude said the candidate demonstrated an improved hematological safety profile compared with prifetrastat, a dual KAT6A/B inhibitor, in preclinical testing. 

How Retail Views PRLD, LLY

Retail sentiment for both PRLD and LLY on Stocktwits remained in ‘Bearish’ territory over the past 24 hours.

One Stocktwits user praised PRLD’s collaborations.

PRLD shares have risen more than 48% year to date, while LLY shares have gained more than 8% over the same period.

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