A Phase 1, Open-Label, Safety, Tolerability, and Efficacy Study of NC525 in Subjects with Advanced Myeloid Neoplasms

Abstract

Background With the exception of certain select subtypes, Acute Myeloid Leukemia (AML) remains incurable for a majority of patients with current therapies. Despite recent drug approvals targeting actionable molecular mutations and BCL-2, relapse remains inevitable for most patients with AML due to leukemia-initiating cells and progenitors {i.e., leukemic stem cells (LSCs)} which are resistant to conventional cytotoxic drugs. Novel agents that preferentially target LSCs to lessen or eliminate the risk for relapse while avoiding significant myelosuppression by sparing normal hematopoietic stem cells (HSCs), are highly sought-after anti-leukemia therapeutics. Leukocyte Associated Immunoglobulin-like Receptor 1 (LAIR-1) is an immune inhibitory receptor that is present on most immune cell subsets, including T cells, NK cells, monocytes, macrophages, dendritic cells, and granulocytes. LAIR-1, a surface leukocyte receptor containing two immune receptor tyrosine-based inhibitory motifs (ITIM), binds to endogenous collagen ligands and plays an important role in inducing an immunosuppressive microenvironment. In AML, the engagement of LAIR-1 inhibits intracellular downstream survival signals, leading to decreased GM-CSF-mediated survival and proliferation of AML blasts. LAIR-1 is expressed on AML blasts and LSCs regardless of FAB subtypes, cytogenetics or molecular mutations. Recent work demonstrates that myeloid leukemia cell lines, primary AML blasts, monoblasts and monocytes, and MDS-EB-2 blasts all express LAIR-1. Critically, while high expression of LAIR-1 is characteristic of LSCs, this receptor is minimally detectable on normal HSCs, making it an ideal anti-leukemic target. NC525 is a humanized immunoglobulin gamma 1, kappa (IgG1κ) monoclonal antibody that targets LAIR-1-expressing AML blasts and LSCs. Extensive IND-enabling preclinical studies have shown the following features of NC525: (i) Inhibition of colony formation of AML CD34+ bone marrow cells; (ii) sparing of colony formation and differentiation ability of healthy CD34+ HSCs; (iii) direct ex vivo killing of AML blasts without killing healthy leukocytes; (iv) suppression of AML in both MV4-11 and THP-1 CDX models; (v) restriction of MV4-11 in a humanized murine model, without depletion or suppression of human T cells; (vi) restriction of MV4-11 tumor growth in murine blood, spleen, and bone marrow; and (vii) reduction of AML disease burden in primary patient-derived AML xenograft (PDX) models. Finally, NC525 completely inhibits leukemia propagation in secondary transplant models, suggesting that NC525 is capable of eradicating LSCs. Furthermore, NC525 destroys leukemic cells by ligation-mediated apoptosis of leukemic blasts and stem cells without evidence of an immunomodulatory effect on other immune subsets. Methods This is an open-label, non-randomized, Phase 1 dose escalation study to determine the safety and tolerability of NC525 in adult patients with advanced myeloid neoplasms. This study will also assess the clinical benefit of NC525. Eligible patients must have relapsed or refractory AML, myelodysplastic syndrome (MDS), or chronic myelomonocytic leukemia (CMML) that has progressed after standard therapy. Participants will receive NC525 by intravenous infusion on Days 1 and 15 of each 28-day cycle. During Phase 1, the safety and tolerability of NC525 will be evaluated by exploring escalating dose levels of NC525. In addition, the pharmacologically active dose (PAD), defined as the dose that provides a maximal biologic effect, such as achieving a complete remission (CR), CR with partial hematological recovery (CRh) or CR with incomplete hematological recovery (CRi), and the maximum tolerated dose (MTD) of NC525 will be determined. Safety and tolerability will be further assessed through the expansion of a few dose levels to determine an optimal recommended Phase 2 Dose (RP2D) and administration schedule of NC525, based on the PK/PD profiles. Taken together, preclinical data suggest that targeting LAIR-1 in AML and other myeloid malignancies may be an effective therapy for these diseases with the advantage of specifically eradicating leukemic stem cells and sparing normal HSCs.