Participants (homozygous MFN2 [gene that provides instructions to produce the Mitofusin 2 protein] R707W) will be treated with Metreleptin, and effects on body composition, metabolic parameters and safety will be assessed over a 6 month intervention period. Additional safety will be assessed for 1 more year (up to 1.5 years total) in which adverse event data will be collected.

In 2024, the IRB granted an amendment that allowed for continued data collection, including adverse events, up to 5 years per participant.

Inclusion Criteria:

• Have the clinical diagnosis of MSL and being followed at University of Michigan (cohort to be studied in this proof-of-concept study is already available at Michigan).

• Willing and able to tolerate the study procedures.

• Willing and able to tolerate blood sampling.

• Having no condition that may impede successful data collection or interfere with testing parameters.

• <60 years of age.

• If female of childbearing potential:

  • Not breastfeeding.
  • Negative pregnancy test (human chorionic gonadotropin, beta subunit) at baseline.

• Can read, understand and sign approved informed consent form, communicate with study physician, and study team, and understand and comply with protocol requirements.

Exclusion Criteria:

• Presence of advanced liver disease (abnormal synthetic function, prothrombin time [PT], or albumin) in medical records
• Evidence of other etiologies of viral hepatitis in medical records
• Presence of active hematologic, bone marrow or other abnormalities that may increase risk of bleeding in medical records.
• Presence of HIV infection in medical records.
• Presence of End-stage renal disease (ESRD), active cancer, or >class 2 congestive heart failure based on medical history and physical examination.
• Active chronic infection (e.g., known chronic osteomyelitis or Tuberculosis [TB]). May have transient infections but must be free of active infection for two weeks prior to study visits.
• Unable to ambulate or tolerate trips to the University of Michigan Clinical Research Unit.
• Clinically relevant Coronary artery disease (CAD): history of stent or Coronary artery bypass graft surgery (CABG) with cardiologist confirmed angina.
• Presence of autoimmune disease.
• Hypersensitivity to metreleptin.
• General obesity not associated with congenital leptin deficiency.
• Any other condition that, in our opinion, may impede successful data collection.

24 weeks