The purpose of this study is to study the safety and tolerability of intravenous (IV) and subcutaneous (SC) administration of REGN1154 in normal healthy subjects.

Inclusion Criteria:

1. Healthy men and women between the ages of 18 and 65; women must be postmenopausal or surgically sterile
2. Body mass index (BMI) between 18.0 and 30.0 kg/m2, inclusive
3. Willing, committed, and able to return for ALL clinic visits and complete all study-related procedures
4. Able to read or to understand the consent process, and willing to sign the informed consent form (ICF)

Exclusion Criteria:

Exclusion criteria include, but are not limited to the following:

1. Any illness or condition that would adversely affect the subject's participation in this study
2. Any clinically significant abnormalities observed during the screening visit
3. Use of certain medications taken before the screening visit
4. Onset of a new exercise routine or major change to a previous exercise routine within 4 weeks prior to screening visit
5. Hospitalization within 60 days of the screening visit
6. Any condition that would place the subject at risk, interfere with participation in the study
7. History of or positive human immunodeficiency virus (HIV) screen result at the screening visit
8. History of certain other conditions
9. Positive urine, drug or alcohol screen result at screening
10. Known sensitivity to any of the components of the investigational product formulation
11. Participation in any clinical research study evaluating another investigational drug or therapy within 30 days or at least 5 half-lives (whichever is longer), of the investigational drug prior to the screening visit
12. Live/attenuated vaccinations within 12 weeks of screening or during the study