A randomized, double-blind, placebo-controlled, study to assess the safety, tolerability, and PK of MTX-463 when administered via SC injection in healthy adult males.

This is a randomized, double-blind, placebo-controlled, study to assess the safety, tolerability, and PK of MTX-463 when administered via SC injection in healthy adult males. The study will consist of a single cohort comprising 8 healthy male participants, who on Day 1 will be randomly assigned to receive MTX-463 or matched placebo. Randomization will be in a 3:1 ratio such that 6 participants will receive MTX-463 and 2 will receive placebo. Participants randomized to MTX-463 will receive a dose of 250 mg of MTX-463.

Participants randomized to placebo will receive SC injections containing sodium chloride 0.9%. The injections will be given under the skin of the abdominal wall on Day 1. Blood will be drawn pre-dose on Day 1 for PK and antidrug antibodies (ADAs) and post-dose for PK at 6 and 24 hours. Participants will remain in the clinical research unit (CRU) for 24 hours after their injections, and then they will return for outpatient PK blood draws on Days 3 through 8, 15, and 22, with blood drawn for ADA assessment on Days 15 and 22. Each participant will undergo assessments at specified timepoints on Days 1 through 22 as detailed in Table 1. End-of-study procedures will be completed on Day 22 or upon early termination (ET). Local safety and tolerability at the injection site will be assessed at the time of the injections and for 24 hours afterward, and on Days 5, 8, 15 (±1 day), and 22 (±2 days) (EOS/ET).

Inclusion Criteria:

• Males aged 18 to 60 years, inclusive
• Able to understand the study and provide signed, written informed consent
• Able to read and understand the language of the informed consent form and other study-related materials
• Willing and able to complete all protocol-required study visits and procedures
• Male participants with female partners of childbearing potential must use condoms during the treatment and until 125 days after the dose of study drug.

Exclusion Criteria:

• Any history of clinically significant lung disease as determined by the Investigator
• Any other concurrent active medical condition determined clinically significant by the Investigator
• Any current skin conditions or rashes that involve the planned area of injection
• Body mass index (BMI) >30 kg/m2
• Use of any systemic immunosuppressant medications, medications to treat diabetes, antipsychotics, anticoagulants, or other medications within 90 days of Screening
• Cancer or a history of cancer or lymphoproliferative disorder within 5 years of Screening
• Current infection with hepatitis B, hepatitis C, or human immunodeficiency virus (HIV)
• Planning to contribute to pregnancy during the study and up to 125 days after the participant's dose of study drug
• History of severe depression, psychosis, or suicidal ideation, as determined by the Investigator, within 5 years of Screening
• Any clinically significant disease or laboratory abnormality detected at Screening that might interfere with a participant's ability to complete the study, on-study evaluations, or participant safety
• Known allergy to MTX-463 or any of its excipients, or a history of a prior allergic reaction to a monoclonal antibody therapeutic

Assigned male at birth