A First-in-Human Safety Trial of MTX-463

This is a randomized, double-blind, placebo-controlled, single ascending dose (SAD) and multiple ascending dose (MAD) study to assess the safety, tolerability, and PK of single and multiple ascending doses of MTX-463 administered in healthy adults.

SAD Portion

The SAD portion of the study will consist of 4 planned dosing cohorts each comprising 8 healthy participants. The starting dose will be 4 mg/kg (Cohort 1) with subsequent planned doses of 8 mg/kg (Cohort 2), 16 mg/kg (Cohort 3), and 30 mg/kg (Cohort 4). Planned doses may be adjusted in response to the data. Additional participants and/or additional dosing cohorts may be added as needed based on the data.

Within each cohort, participants will be randomly assigned to receive MTX-463 or matched placebo. The first 2 participants (sentinel participants) within each cohort will be randomized 1:1 to receive MTX-463 or placebo on Day 1. These participants will be monitored for 24 hours, and after review of the safety data from both participants and approval by the study Investigator and Sponsor's responsible medical officer (SRMO), the additional 6 participants will be randomized to study drug (n=5 MTX-463; n=1 placebo).

Each participant will undergo assessments at specified timepoints on Days 1 through 60. End-of-Study (EOS) procedures will be completed on Day 28 or upon early termination (ET). An End-of-Follow-up (EOF) assessment of PK and ADA will be completed on Day 60.

MAD Portion

The MAD portion of the study will consist of 3 planned dosing cohorts. Each cohort will comprise 8 healthy participants (n=6 MTX-463; n=2 placebo). The starting dose will be a 6.6 mg/kg loading dose and 4 mg/kg maintenance doses (Cohort 1) with subsequent planned doses of a 13 mg/kg loading dose and 8 mg/kg maintenance doses (Cohort 2), and a 27 mg/kg loading dose and 16 mg/kg maintenance doses (Cohort 3). Planned doses may be adjusted in response to the data. Additional participants and/or additional dosing cohorts may be added as needed based on the data.

On Day 1, participants will be randomized to receive either MTX-463 or matched placebo. The randomized participants will receive a single loading dose on Day 1 followed by 2 maintenance doses of study drug on Day 8 and Day 22. Participants will be housed inpatient from Day -1 through post-dose observation on Day 8 and from Day 21 through assessments on Day 29. All other visits will be conducted in the outpatient setting. Each participant will undergo assessments at specified timepoints on Days 1 through 82. End-of-study procedures will be completed on Day 50, or upon ET. An EOF assessment of PK and ADA will be completed on Day 82.