Black Diamond Therapeutics said that the dose escalation part of the Phase 1 clinical trial of BDTX-1535 in recurrent glioblastoma (GBM) patients showed promising clinical activity for the investigational candidate.

The Phase 1 trial is evaluating the drug candidate in GBM patients who revealed epidermal growth factor receptor (EGFR) alterations during their initial diagnosis.

The fourth generation BDTX-1535 is an oral, brain-penetrant, covalent EGFR inhibitor. It is currently in Phase 1 clinical study in patients with non-small cell lung cancer (NSCLC) or GBM.

In the dose escalation cohort, 27 patients with recurrent GBM received a range of doses spanning 15mg to 400mg once daily (QD).

Out of them, 22 were started at or escalated to a dose of 100mg QD or greater and reached at least one post baseline tumour assessment.

According to key results, three out of 22 evaluable patients received therapy for more than 10 months, one for more than six months, and five for more than four months.

In this population, the historical progression-free survival (PFS) was found between two to four months.

The longest-treated patient remained on BDTX-1535 at 100 mg QD for more than 15 months with prolonged disease stabilisation.

Additionally, eight individuals had stable disease (SD) and one patient had a confirmed partial response (PR) out of the 19 patients with detectable disease according to Response Assessment in Neuro-Oncology (RANO) criteria.

The PR patient had treatment at a dose of 200mg QD for more than four months.

Black Diamond Therapeutics chief medical officer Sergey Yurasov said: “We believe the ‘window of opportunity’ trial of BDTX-1535 will provide valuable information on both drug levels in the brain and clinical activity in second-line patients, and will inform potential next steps in our development programme.

“More than half of all newly diagnosed GBM patients express an altered form of EGFR, and preclinical data demonstrate BDTX-1535 potently inhibits this spectrum of alterations. Therefore, BDTX-1535 may be optimally suited to benefit first-line patients.”

BDTX-1535 dose escalation in GBM patients is now completed and dose expansion is continuing in NSCLC patients.

Black Diamond Therapeutics is also enrolling patients in a window of opportunity trial of BDTX-1535 in second-line patients with high-grade glioma.