On October 22, 2026 BlossomHill Therapeutics, Inc. (Nasdaq: BLSM), a clinical-stage biopharmaceutical company applying an intentional, chemistry-based approach to design and develop innovative small molecule medicines for the treatment of cancer, reported a collaboration with Foundation Medicine, Inc. to develop a companion diagnostic assay (CDx) for the EGFR C797S resistance mutation. The collaboration will leverage the ongoing Phase 1/2 SOLARA clinical trial evaluating BH-30643 in the targeted treatment of epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) patients to validate the assay.
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EGFR C797S is the most common EGFR mutation driving resistance to osimertinib treatment in EGFR-mutant NSCLC. BH-30643 is a macrocyclic mutant-selective OMNI-EGFR inhibitor that has demonstrated clinical activity against a variety of EGFR mutations, in particular the C797S mutation that drives resistance to standard therapy. Understanding and targeting resistance mechanisms to existing EGFR inhibitors is an active area of clinical investigation and drug development. To this end, the collaboration will focus on validating a reliable diagnostic assay for the detection of EGFR C797S mutation to help guide BH-30643’s ongoing development.
"Our near-term development priority for BH-30643 is to address the unmet needs of EGFR-mutant NSCLC patients with known resistance mutations following progression on prior EGFR targeted therapy," said Geoff Oxnard, MD, Chief Medical Officer at BlossomHill. "Foundation Medicine is the most experienced developer of precision CDx assays and the ideal partner to help us characterize EGFR resistance and validate a CDx assay to support the development of our medicine."
About BH-30643
BH-30643 is an investigational, novel, orally bioavailable, non-covalent, macrocyclic, brain active, mutant-selective, OMNI-EGFR inhibitor for the treatment of EGFR-mutant NSCLC. BH-30643 was designed to overcome the limitations of currently approved EGFR inhibitors, which were discovered over a decade ago without the current, modern understanding of the structure and protein dynamics of mutant EGFRs. In preclinical studies, BH-30643 demonstrated potent inhibitory activity across diverse EGFR mutation categories — classical mutations, on-target resistance mutations such as C797S with or without T790M, atypical mutations and exon 20 insertions — while maintaining marked selectivity over wild-type EGFR. BH-30643 has received Fast Track designation and is being evaluated in SOLARA, a global Phase 1/2, first-in-human clinical trial spanning more than 40 sites in 10 countries. Ongoing dose expansion cohorts are enrolling in both TKI-pretreated and TKI-naive settings, including a C797S resistance cohort. For additional information on SOLARA, including a list of study sites and how to enroll, please visit clinicaltrials.gov (NCT06706076).
About the SOLARA Trial
The Phase 1/2 SOLARA clinical trial (NCT06706076) is a global, open label, multicenter study assessing the safety, tolerability, pharmacokinetics, pharmacodynamics and preliminary anti-tumor activity of BH-30643 in patients with epidermal growth factor receptor (EGFR) mutant non-small cell lung cancer (NSCLC). Phase 1 will determine the recommended Phase 2 dose (RP2D) of BH-30643 as a monotherapy and in combination with chemotherapy. Phase 2 is designed to evaluate the antitumor efficacy and safety in specified cohorts determined by mutation subtypes and/or treatment history at the RP2D, as well as the population pharmacokinetics.
(Press release, BlossomHill Therapeutics, OCT 22, 2026, https://www.globenewswire.com/news-release/2026/10/22/3386178/0/en/blossomhill-therapeutics-announces-collaboration-with-foundation-medicine-to-develop-first-companion-diagnostic-for-bh-30643-in-egfr-c797s-mutated-non-small-cell-lung-cancer.html [SID1234673694])