This report is based on public company disclosures, filings and announcements reviewed by GSN; figures are as stated by the company and have not been independently verified.

BlossomHill Therapeutics (Nasdaq: BLSM) is a clinical-stage biopharmaceutical company that applies a chemistry-based approach to design and develop small molecule medicines for the treatment of cancer. The company announced on September 15, 2026, that it presented updated data from its ongoing Phase 1/2 SOLARA trial at the International Association for the Study of Lung Cancer 2026 World Conference on Lung Cancer in Seoul, South Korea.

The data highlights the performance of BH-30643, an investigational, orally bioavailable, non-covalent, macrocyclic, brain-active, mutant-selective, OMNI-EGFR inhibitor. The drug is designed to overcome limitations of currently approved EGFR inhibitors for the treatment of EGFR-mutant non-small cell lung cancer. The specific focus of this presentation was on patients with secondary epidermal growth factor receptor resistance mutations, such as EGFR C797S.

According to the press release, the trial observed a 45 percent objective response rate and an 88 percent disease control rate in patients with EGFR C797S-positive resistance to prior EGFR inhibitors. This population includes patients with or without concurrent T790M mutations. The company noted that this is a difficult-to-treat group with no approved targeted therapies currently available. At the time of efficacy follow-up, 63 percent of the 40 patients in this cohort remained on treatment. The median follow-up period was 6.9 months.

The data cutoff for the efficacy analysis was May 12, 2026, with follow-up through August 10, 2026. Among the 40 patients with EGFR C797S-positive resistance, 18 achieved a confirmed or ongoing unconfirmed partial response. The company stated that the drug demonstrated a favorable safety profile with low rates of dose reduction or discontinuation due to treatment-related adverse events. Specifically, among 174 patients treated at expansion doses of 40 mg, 50 mg, and 60 mg twice daily, treatment-related dose reductions occurred in 9 percent of patients and discontinuations in 3 percent.

The patient population was heavily pretreated. Patients had received a median of two prior lines of therapy. Ninety-eight percent had received prior osimertinib, 53 percent had received prior chemotherapy or an antibody-drug conjugate, and 53 percent had a history of brain metastases. Thirty-five percent of patients had concurrent T790M.

Geoff Oxnard, M.D., Chief Medical Officer of BlossomHill Therapeutics, stated that the updated results provide important clinical validation of the approach taken in intentionally designing BH-30643 to address on-target EGFR resistance, including C797S. He added that the company is encouraged to see meaningful anti-tumor activity across a molecularly diverse group of patients. The company said these results, together with the recent FDA Fast Track designation, strengthen its conviction in the potential of the drug and support plans to advance into a Phase 2 trial in patients with C797S-positive NSCLC in 2027.

For investors, this data represents a critical validation step for a drug targeting a specific, high-unmet-need mutation in lung cancer. The objective response rate of 45 percent in a heavily pretreated population suggests significant biological activity. The transition from Phase 1 to Phase 2 in 2027 will be the next major catalyst for the company, potentially expanding the addressable market and providing clearer commercial timelines.

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