685P - BL-M07D1, a HER2 antibody-drug conjugate in subjects with locally advanced or metastatic HER2 expressing breast cancer and other solid tumors

Background

BL-M07D1 is an anti-HER2 antibody drug conjugate (ADC). It consists of a humanized anti-HER2 antibody, a cathepsin B cleavable linker, and a novel topoisomerase I inhibitor (Ed-04).

Methods

This study included subjects with locally advanced or metastatic HER2 expressing (positive/low) breast cancer (BC) and other solid tumors. For dose escalation (D-ESC), BL-M07D1 is planned to be administered at doses of 1.0mg/kg D1D8 Q3W or 2.6, 3.2, 3.8, 4.4, 5.0, 5.6, 6.2 mg/kg D1 Q3W. A subset of subjects were enrolled in the dose-expansion phase (D-EXP) at D1 Q3W regimens.

Results

As of May 1^st, D-ESC has reached a dose of 5.0 mg/kg, with no observed dose limiting toxicities (DLTs).The maximum tolerated dose (MTD) was not reached. A total of 50 pts were treated with at least one dose, 19 pts in D-ESC and 31 in the D-EXP phase. The dose levels for expansion included 3.8, 4.4 and 5.0 mg/kg D1 Q3W. Among 50 pts,one received BL-M07D1 at 1.0 mg/kg on Day 1 and Day 8 every 3 weeks (D1D8 Q3W), while the remaining 49 subjects were treated with the drug on a Day 1 every 3 weeks (D1Q3W) schedule. The study enrolled 41 BC, 5 gastric cancer, 2 rectal cancer and 2 non-small cell lung cancer patients. The most common TRAEs (>10%, all grade /≥G3) were leukopenia (60%/13%), neutropenia (58%/21%), nausea (44%/0%), anemia (44%/0%), vomiting (25%/2%), lymphocyte count decreased (23%/8%), gamma-glutamyltransferase increased (21%/2%), asthenia (19%/0%), thrombocytopenia (19%/0%), decreased appetite (17%/0%), alopecia (17%/0%), aspartate aminotransferase increased (15%/0%). No ILD was observed. Twenty six subjects were evaluated for efficacy (i.e., at least one post-baseline tumor assessment). Updated efficacy and pharmacokinetic (PK) results will be presented at the conference. Table: 685P

Conclusions

BL-M07D1 demonstrated encouraging efficacy in heavily pretreated HER2 expressing cancers, especially in HER2-positive BC. The safety profile showed adequate safety and tolerability.

Clinical trial identification

NCT05461768.

Editorial acknowledgement

Legal entity responsible for the study

SystImmune Inc.

Funding

Sichuan Baili Pharmaceutical Co., Ltd.

Disclosure

S. Xiao: Financial Interests, Personal, Full or part-time Employment: Baili-Bio (Chengdu) Pharmaceutical Co., Ltd.; Financial Interests, Personal, Stocks/Shares: Baili-Bio (Chengdu) Pharmaceutical Co., Ltd. H. Wang: Financial Interests, Personal, Full or part-time Employment: Systimmune Inc. H. Zhu: Financial Interests, Institutional, Full or part-time Employment: Systimmune Inc. M.S. Olivo: Financial Interests, Institutional, Officer, I'm the CMO of the company: SystImmune; Financial Interests, Institutional, Stocks/Shares: SystImmune. Y. Zhu: Financial Interests, Personal, Full or part-time Employment: SystImmune Inc; Financial Interests, Personal, Ownership Interest: SystImmune Inc., Baili Pharmaceutical. All other authors have declared no conflicts of interest.