Foghorn Therapeutics Inc.

Poster Presentation Highlights

Title: Preclinical characterization of FHT-171, a first-in-class degrader targeting CREB-binding protein (CBP) in CBP-dependent solid tumors

FHT-171 is a selective CBP degrader with potential to treat CBP-dependent solid tumors showing:

•Strong anti-tumor activity as a monotherapy in PDX models of heavily pretreated ER+ breast cancer

•Favorable tolerability profile in preclinicalin vivo studies

•High selectivity and potent CBP degradation with clear on-target transcriptional effects by SAR, proteomics, and mechanistic analyses

•Mechanistic understanding of the utility of CBP degraders in ER+ breast cancer

Title: Preclinical evaluation of selective and potent EP300 degraders demonstrates robust antitumor activity and favorable tolerability in hematologic malignancies

Foghorn’s Selective EP300 degraders demonstrate promise for the treatment of hematological malignancies with preclinical data showing:

•Superior anti-tumor activity, including complete responses, compared to clinical benchmark dual CBP/EP300 inhibitor inobrodib

•Superior safety, by body weight loss and platelet counts, over dual degradation

•Tumor regression in a multiple myeloma xenograft model of acquired pomalidomide resistance

•Selective EP300 degradation as a novel and promising therapeutic strategy to treat multiple myeloma

Title: Identification of first-in-class selective ARID1B degraders

Selective ARID1B degraders represent a first-in-class approach to target prevalent ARID1A-mutant cancers by exploiting a synthetic lethal dependency. Preclinical data of this previously intractable target show:

•Successful identification of the first selective ARID1B binders

•Robust degradation via VHL and CRBN-based mechanisms

•Clear on-mechanism activity with downstream transcriptional modulation

The presentations and the posters will be accessible under the Science section of the Company’s website.