Safety, Pharmacokinetics, and Pharmacodynamics of MTX-101 in Healthy Adults and Patients

Inclusion Criteria: * Adults, age ≥ 18 and ≤ 65 years at the time of anticipated dosing (Day 1). * Healthy individuals without known current or chronic medical conditions, including no history of any autoimmune diseases, in the opinion of the Investigator. * Body mass index (BMI) ≥ 18 kg/m2 and ≤ 35 kg/m2 AND body weight ≥ 55 and ≤ 120 kg. * Negative Coronavirus Disease 2019 (COVID-19) test within 24 hours prior to each dose. * Persons of child-bearing potential must have a negative pregnancy test and either abstain from sex or use highly effective method(s) of birth control from Day 1 through the duration of the study. Exclusion Criteria: * Clinically significant findings in physical examination (PE), vital signs (blood pressure, heart rate, and body temperature), electrocardiogram (ECG), and safety laboratory parameters at Screening in the opinion of the Investigator. * Prior or concurrent malignancies. * Renal function calculated by the Chronic Kidney Disease-Epidemiology (CKD-EPI) equation with estimated glomerular filtration rate (eGFR) \< 90 mL/min/1.73 m2 or abnormal level of proteinuria detected by dipstick at the time of Screening. * Any disease or condition that, in the opinion of the Investigator, might significantly compromise the cardiovascular, hematological, renal, hepatic, pulmonary (including chronic asthma), endocrine (e.g., diabetes), central nervous, or gastrointestinal (including an ulcer) systems. * Receipt of an investigational drug within 28 days or 5 half-lives (whichever is longer) of the investigational drug(s) prior to Day 1. * Positive serology for human immunodeficiency virus (HIV) type 1 or 2, hepatitis (Hep) B surface antigen, or Hep C. * Positive test results for drug screen, including alcohol, at the time of Screening or on Day 1 prior to randomization. * Use of tobacco or nicotine-containing products more than the equivalent of 5 cigarettes/week within 30 days prior to (first) dosing. Participants must abstain from nicotine use while inpatient. * History of receiving a live vaccine within 1 month of Screening. * History of splenectomy. * History of COVID or influenza vaccine within 2 weeks prior to Screening. * Planning to receive any vaccinations during the study period. * History of recurrent infections of uncertain cause.