A bispecific antibody-drug conjugate targeting CD7 and CD33 shows anti-tumor activity and improved tumor selectivity in an aggressive subtype of acute myeloid leukemia.

Acute myeloid leukemia (AML) is a heterogeneous malignancy with poor clinical outcome. Aberrant expression of CD7 in AML patients is linked to shorter overall survival and lack of response to standard of care therapy. CD33/CD7 co-expression on leukemic blasts occurs in approximately one-third of AML patients and is known to be absent in normal myeloid cells. We propose that CD33CD7 AML constitutes an aggressive subgroup characterized by poorer prognosis and enrichment in stem-cell associated gene signatures. To address the substantial unmet need in this patient cohort, we developed the antibody-drug conjugate BVX001, a CD33xCD7-targeted bispecific antibody-binding fragment linked to an auristatin payload. Importantly, BVX001 relies on simultaneous binding to CD33 and CD7 in through an 'AND-gated' design, for optimal delivery of its cytotoxic payload. Consequently, BVX001 did not affect healthy myeloid progenitors or T cells at concentrations at which its monospecific counterparts showed toxicity. BVX001 induced significant tumor regression in AML cell line and patient-derived xenografts and increased overall survival. Finally, BVX001 showed significant blast ablation and reduced leukemic stem cell frequency in AML patient samples with both high and low target co-expression. Together, our findings support BVX001 as a new and promising approach for the treatment of this aggressive CD33CD7 AML subtype, currently lacking targeted therapeutic options.