On September 15, 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 updated data from the ongoing Phase 1/2 SOLARA trial of BH-30643 in non-small cell lung cancer (NSCLC) patients with secondary epidermal growth factor receptor (EGFR) resistance mutations such as EGFR C797S. The data were highlighted in a mini-oral presentation at the International Association for the Study of Lung Cancer (IASLC) 2026 World Conference on Lung Cancer in Seoul, South Korea.
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BH-30643 is an investigational, novel, orally bioavailable, non-covalent, macrocyclic, brain active, mutant-selective, OMNI-EGFR inhibitor designed to overcome the limitations of currently approved EGFR inhibitors for the treatment of EGFR-mutant NSCLC. In patients with EGFR C797S-positive resistance to prior EGFR inhibitor treatment, with or without concurrent T790M, BH-30643 demonstrated a 45% objective response rate (ORR; 18/40) and an 88% disease control rate (DCR; 35/40). At the time of efficacy follow-up, 63% (25/40) of patients remained on treatment with a median follow-up of 6.9 months. BH-30643 also demonstrated a favorable safety profile with low rates of dose reduction or discontinuation due to treatment-related adverse events.
"C797S-driven resistance to third-generation EGFR inhibitors was first described over 10 years ago, yet patients whose tumors develop this mutation currently have no approved targeted treatment options," said Hidehito Horinouchi, M.D., Ph.D., National Cancer Center Hospital, Tokyo, and presenting author of the study. "The responses observed with BH-30643 in this heavily pretreated population, together with encouraging early evidence of durability, support the potential of BH-30643 to directly target this resistance mechanism. These results are particularly encouraging given the need for new precision treatment options that can extend the benefits of targeted therapy for patients with EGFR-mutant lung cancer."
"These updated results provide important clinical validation of the approach we took in intentionally designing BH-30643 to address on-target EGFR resistance, including C797S," said Geoff Oxnard, M.D., Chief Medical Officer of BlossomHill Therapeutics. "We are encouraged to see meaningful anti-tumor activity across a molecularly diverse group of patients with C797S-positive disease, including patients with concurrent T790M and those who have received multiple prior therapies, with a favorable safety profile. Together with the recent FDA Fast Track designation, these data strengthen our conviction in the potential of BH-30643 and support our plans to advance into a Phase 2 trial in patients with C797S-positive NSCLC in 2027."
Presentation highlights:
As of the May 12, 2026 data cutoff, with efficacy follow-up through August 10, 2026:
Encouraging anti-tumor activity was observed in patients with C797S-positive resistance. Among 40 patients with EGFR C797S-positive resistance to prior EGFR inhibitor treatment, with or without concurrent T790M, 18 patients achieved a confirmed (16) or ongoing unconfirmed (2) partial response, representing an ORR of 45% (95% CI: 29%-62%). The DCR was 88% (35/40), and 25 patients (63%) remained on treatment at the time of efficacy follow-up. Median follow-up was 6.9 months.
Activity was observed across a clinically heterogeneous, previously treated population. Patients had received a median of two prior lines of therapy; 98% had received prior osimertinib, 53% had received prior chemotherapy and/or an antibody-drug conjugate, and 53% had a history of brain metastases. 35% of patients had concurrent T790M.
BH-30643 demonstrated a favorable safety profile at expansion doses. Among 174 patients treated at doses of 40 mg, 50 mg and 60 mg twice daily, treatment-related dose reductions and discontinuations occurred in 9% and 3% of patients, respectively. EGFR wild-type-associated treatment-related adverse events were primarily Grade 1. The most common treatment-related adverse event was bilirubin elevation, which was generally asymptomatic and predominantly unconjugated, consistent with UGT1A1 inhibition by BH-30643.
Development of BH-30643 is continuing across multiple EGFR-mutant populations. Expansion cohorts are evaluating on-target resistance mutations, targeted therapy-naive patients and BH-30643 in combination with chemotherapy. BlossomHill plans to initiate a global Phase 2 study targeting EGFR C797S-positive NSCLC in Q1 2027.
The presentation is available on the company’s Posters & Presentations page here: View Source
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, SEP 15, 2026, View Source [SID1234670888])