SystImmune has dosed the first patient in its global Phase III clinical trial, BrenDeLL-Lung01, assessing BL-M14D1 combined with atezolizumab in those with previously untreated extensive-stage small cell lung cancer (ES-SCLC).

The randomised, multi-centre trial, which aims to enrol around 580 participants, will evaluate the BL-M14D1 regimen compared to standard treatment.

The primary endpoint of this study is progression-free survival as determined by a blinded independent central review.

BL-M14D1 is an investigational antibody-drug conjugate (ADC) that targets delta-like protein 3 (DLL3) present at high levels on small cell lung cancer and neuroendocrine tumour cells.

Built on SystImmune’s brengitecan platform, it is designed to selectively deliver a topoisomerase I inhibitor payload to DLL3-positive tumour cells.

The initiation of the Phase III programme follows positive clinical results from the Phase I trial BL-M14D1-101, presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting.

In that study, BL-M14D1 showed anti-tumour activity and a manageable safety profile in patients who had received multiple prior treatments for small cell lung cancer and other neuroendocrine carcinomas.

SystImmune chief medical officer Jonathan Cheng said: “The initiation of our global Phase III programme marks an important milestone for BL-M14D1 and reflects our commitment to bringing innovative treatment options to patients with small cell lung cancer.

“Despite recent advances, outcomes for patients with extensive-stage small cell lung cancer remain poor, and there continues to be a significant need for more effective therapies.

“We believe BL-M14D1 has the potential to improve outcomes for these patients, and we are excited to begin evaluating the programme in a registrational setting.”

SystImmune’s pipeline includes candidates for both solid tumour and blood cancers, with assets at various stages of clinical and preclinical development.