ISB 1442

ISB 1442 has 2 Fab domains binding to distinct CD38 epitopes that do not compete functionally with daratumumab. Treatment with ISB 1442 was well tolerated at the dose levels evaluated. The observed clinical CRS events were moderate and potentially related to macrophage activation following ISB 1442 administration. Updated clinical, biomarker and PK data will be presented for this ongoing study.

Hence, an enhanced CD38 targeted therapy that unleashes the innate immune cell mediated tumor killing potential and overcomes daratumumab resistance mechanisms may present a unique opportunity to treat MM...Due to low-affinity binding to CD47, ISB 1442 engages CD47 efficiently only upon CD38 binding (avidity-induced binding), thereby reducing the potential for on-target, off-tumor effects, and it does not cause any detectable RBC depletion in vitro compared to magrolimab (Figure 2)...The study is currently open for enrollment. Clinicaltrials.gov identifier: NCT05427812.

Preclinical activity of ISB 1442 for the treatment of relapsed/refractory multiple myeloma (rrMM), including increased killing potency relative to daratumumab and magrolimab benchmarks as well as more favorable off tumor/on target specificity, was reported previously (Sammicheli et al. In summary, these data support the clinical development of 1442 in AML and T-ALL. Based on its unique design and multiple mechanisms of action, ISB 1442 is anticipated to have antitumor activity in AML and T-ALL patients in a single antibody relative to anti-CD38 or anti-CD47 monoclonal antibodies as well as their combination.

Aims ISB 1442 was developed for the treatment of hematologic malignancies that express CD38, including multiple myeloma (MM), acute myeloid leukemia (AML), and T-acute lymphoblastic leukemia (T-ALL), with the intention of overcoming mechanisms of resistance to CD38-targeted therapies such as daratumumab and isatuximab, and minimizing hemagglutination/hemolysis on red blood cell (RBC) observed with anti-CD47 monoclonal antibodies (mAb) such as magrolimab. Conclusion In summary, we report a novel approach for the treatment for CD38 positive hematologic malignancies by co-targeting CD38 and CD47 using a first in class multispecific antibody. Based on its unique design and multiple mechanisms of action, ISB 1442 is anticipated to enhance antitumor activity in patients relative to anti-CD38 mAbs by overcoming primary and acquired tumor escape mechanisms of resistance.

This approach is expected to induce minimal unintended effects on red blood cells (RBC) compared to anti-CD47 monoclonal antibody (mAb) magrolimab as it enables the CD47 binding only upon avidity induced CD38 crosslinking. In summary, we report a novel approach for the treatment for CD38+ cancers by co-targeting CD38 and CD47. Based on its unique design and multiple mechanisms of action, ISB 1442 is anticipated to enhance antitumor activity by overcoming known primary and acquired tumor escape mechanisms of resistance relative to daratumumab.