This is a single-arm pilot study of the feasibility and safety of metformin in patients with clonal cytopenia of undetermined significance (CCUS) or lower-risk myelodysplastic neoplasms (LR-MDS).

The research plan is divided into three work packages (WP):

WP0: Bone Marrow Adipose Tissue, Gut Microbiota, and Intestinal Permeability in CCUS and LR-MDS Patients.

The aim of WP0 is to investigate biological features which the investigators hypothesize to be of pathogenetic relevance for MDS progression and may be possible targets of metformin treatment. For this purpose, 20 elderly (≥60 years) healthy controls will be included for comparison to patients with CCUS or LR-MDS from WP1.

The primary objectives are to investigate 1) the abundance and properties of bone marrow adipose tissue (BMAT) and bone marrow (BM) adipocytes, and 2) the gut microbiota and intestinal permeability of patients with CCUS or LR-MDS compared to age-, sex- and body mass index (BMI)-matched healthy controls. Secondary objectives are to characterize DNA methylation and hydroxymethylation (5-mC and 5-hmC) patterns, and hormone and cytokine levels in BM plasma from healthy controls and patients with CCUS or LR-MDS.

WP1: Safety, feasibility, and mechanisms of action of metformin in patients with CCUS or LR-MDS.

In this WP up to 40 patients with CCUS or LR-MDS will receive metformin 2000 mg daily or their maximum tolerated dose (MTD) for 12 months. The aim of WP1 is to investigate safety of metformin and feasibility of the protocol in patients with CCUS or LR-MDS. Potential mechanisms of anti-leukemic action of metformin will also be explored in order to identify a suitable outcome measure and estimate standard deviation of the outcome measure. All in order to inform the design of a future phase 3 RCT of the efficacy of metformin in CCUS and LR-MDS patients. Endpoints of WP1 are specified in the corresponding section.

WP2: Safety and efficacy of metformin compared to placebo. The primary objective of WP2 is to compare safety and preliminary efficacy of metformin in patients with CCUS or LR-MDS to a cohort of patients with CCUS or LR-MDS receiving placebo in context of our EVI-2 randomized, controlled pilot study (NCT03999723).

Data and samples from approximately 50 historical controls will be included from the EVI-2 study in which participants were randomized to receive placebo or oral vitamin C supplement for 12 months.

Patients are eligible to be included in WP1 if they meet all of the following criteria:

Inclusion criteria:

• A diagnosis of:

  • LR-MDS according to the revised international prognostic scoring system (IPSS-R), i.e., very low- or low-risk disease (IPSS-R score ≤3) in addition to a bone marrow blast percentage <5 OR
  • CCUS defined as the presence of somatic mutation(s) or cytogenetic abnormality not diagnostic of MDS or any other malignancy in the context of persistent cytopenia (>6 months) with other common causes of cytopenia ruled out in the setting of bone marrow morphology that is not diagnostic of MDS or any other malignancy, and hematolytic conditions have been ruled out. Peripheral blood cytopenia is defined as hemoglobin (hgb) <11.3 g/dL (7 mmol/L) in women and hgb <12.9 g/dL (8 mmol/L) in men, platelet count <150 x 109/L, or neutrophil count <1.8 x 109/L

• Menopause, if being a female, defined as females >45 years of age who have experienced amenorrhea for minimum 12 months, without any other obvious pathological or physiological cause

• ≥18 years of age

• Written informed consent

• Willingness to comply with mandatory aspects of the protocol

• Ability to swallow pills

Exclusion criteria:

• Any prior treatment with metformin
• A diagnosis of diabetes mellitus
• Therapeutic radiation, immunosuppressive therapy (with the exception of corticosteroids), or chemotherapy within the past year
• Treatment with granulocyte colony-stimulating factor within the past 30 days
• Prior therapy with hypomethylating agents (i.e., azacitidine, decitabine)
• eGFR <45 mL/min
• Performance status according to the Eastern Cooperative Oncology Group >2
• Other active malignancy within the past five years
• Uncontrolled comorbidity including impaired hepatic function (total serum bilirubin >1.5 × upper limit of the normal range (ULN), serum alanine transaminase >3 × ULN), chronic hepatitis with decompensated cirrhosis, disabling psychiatric disease, severe neurologic disease, uncontrolled metabolic disease, or severe cardiac disease (NYHA class 3-4)

An eGFR calculation performed up to one month prior to inclusion may be used to assess renal function. If such an assessment is not available, it is performed at screening.

Healthy volunteers are eligible to be included in WP0 if they meet all of the following criteria:

Inclusion criteria:

• Healthy individuals matched on age, sex, and BMI, if possible, to individual patient participants in WP1
• Written informed consent
• Willingness to comply with mandatory aspects of the protocol

Exclusion criteria:

• Use of metformin within the past 3 years
• A diagnosis of diabetes mellitus, rheumatological disorders, autoimmune diseases or other inflammatory disorders, celiac disease, inflammatory bowel disease, or other gastrointestinal disorders or symptoms
• Treatment with immunosuppressive drugs (with the exception of corticosteroids) or chemotherapy within the past year or antibiotics within the past 6 months
• Any contraindications to MRS