This is a study to assess the safety of increasing dose levels of bexmarilimab when combined with standard of care (SoC) in patients with myelodysplastic syndrome (MDS) or chronic myelomonocytic leukemia (CMML) or acute myeloid leukemia (AML); Phase 1 aims to identify the recommended phase 2 dose (RP2D) of bexmarilimab based on safety, tolerability and pharmacological activity; Phase 2 will investigate the preliminary efficacy of the combination treatment in selected indications from Phase 1.

This is a multicenter Phase 1/2 open-label, study to assess the safety, tolerability and preliminary efficacy of increasing doses of bexmarilimab (FP-1305) in patients with intermediate, high or very high-risk MDS, CMML with 10-19 % marrow blasts, CMML/MDS with failure to hypomethylating agent (HMA), or in patients with newly diagnosed AML non-fit for induction therapy or relapsed/refractory AML. The Phase 1 part of the study will identify a safe and tolerable bexmarilimab dose amongst four predefined dose levels using a bayesian optimal interval (BOIN) dose escalation design to identify the maximum tolerated dose (MTD) of bexmarilimab when administered in combination with SoC.

The Phase 2 of the study is an expansion phase to further evaluate the safety and preliminary efficacy of bexmarilimab treatment at RP2D combined with SoC and will follow a Simon's 2-stage design for each of the indications selected to continue forward from Phase 1. This design allows for the investigation of bexmarilimab activity and preliminary response assessments tailored to each indication and allows early stopping in case of futility using a minimum number of patients. Patients from Phase 1, with the selected indication to be investigated in Phase 2, that have been treated at RP2D may be counted towards the number of patients for Phase 2.

Both study phases consist of a screening period, a treatment period, an end of treatment (EoT) as safety follow-up and disease progression/survival follow-up.

Inclusion Criteria:

• Patient ≥ 18 years of age who presents with one of the following conditions:

  • Morphologically confirmed diagnosis of MDS with revised International Prognostic Scoring System (rIPSS) risk categories: intermediate, high and very high.
  • Morphologically confirmed diagnosis of CMML-2 with indication for azacitidine treatment.
  • CMML and MDS patient with response failure to HMA or therapy regimen including HMA.
  • Morphologically confirmed diagnosis of r/r AML following at least 1 line of prior therapies with indication for azacitidine treatment.
  • Morphologically confirmed diagnosis of AML in patients unfit for induction therapy with indication for azacitidine-venetoclax treatment.

• Leukocyte count < 20 x10^9/L (< 25 x10^9/L for newly diagnosed AML). Hydroxycarbamide use is permitted to meet this criterion in MDS and AML but not in CMML.

• Adequate renal function.

• Adequate liver function.

Exclusion Criteria:

• Patient with acute promyelocytic leukemia (APL) or myeloproliferative CMML as defined by leukocyte count > 13 x10^9/L.
• Eastern Cooperative Oncology Group (ECOG) performance status >2 (except newly diagnosed AML where ECOG 3 is allowed for patients < 75 years).
• Allogeneic transplantation less than 6 months prior screening.
• Patient with active auto-immune disorder (except type I diabetes, celiac disease, hypothyroidism requiring only hormone replacement, vitiligo, psoriasis, or alopecia).
• The patient requires systemic corticosteroid (≥10 mg/day prednisone or equivalent) or other immunosuppressive treatment.
• Less than 21 days since the last dose of intravenous anticancer chemotherapy or less than 14 days or five half-lives (whichever is shorter) from a small molecule targeted therapy or oral anticancer chemotherapy before the first study treatment.
• Any immunotherapy or investigational therapy within preceding 28 days from the first study treatment.
• Pregnant or lactating women.
• History of chronic ulcers or clinically relevant liver disease leading to Child Pugh Score C or higher.