A Study to Assess the Safety and Tolerability of Single Ascending Doses of REGN1033(SAR391786)

Inclusion Criteria:

1. Healthy males and postmenopausal or surgically sterile females

2. Body mass index (BMI) between 18 and 30 kg/m2 inclusive

3. Willing and able to return for all clinic visits and complete all study-related
procedures

4. Able to read and understand, and willing to sign the ICF

Exclusion Criteria:

1. Significant concomitant illness or history of significant illness such as, but not
limited to cardiac, renal, rheumatologic, neurologic, psychiatric, endocrine,
metabolic or lymphatic disease that would adversely affect the subject's
participation in this study

2. History of muscle neoplasms such as rhabdomyoma, rhabdomyosarcoma, leiomyoma,
leiomyosarcoma or uterine fibroid tumors

3. History of muscular dystrophy, myositis, and other primary diseases of skeletal
muscle

4. History of heart diseases including but not limited to coronary heart disease
with/without history of myocardial infarction, chronic or acute heart failure, or
cardiac arrhythmia, valvular heart disease or cardiac hypertrophy. Subjects taking
prophylactic aspirin are excluded from the study and should not discontinue taking
prophylactic aspirin to participate in the study

5. History of systemic hypertension or use of concomitant medications to treat
hypertension, or history of pulmonary hypertension

6. History of diabetes mellitus or gestational diabetes or use of concomitant
medications for treatment of these

7. Recent use of androgenic steroids

8. Unexplained creatine phosphokinase (CPK) levels >3X upper limit of normal.

9. Any medical or psychiatric condition which, in the opinion of the investigator, would
place the subject at risk, interfere with participation in the study or interfere
with the interpretation of the study results

10. Women of childbearing potential (not surgically sterile or amenorrheic for at least
twelve months if postmenopausal)

11. Onset of a new exercise routine or major change to a previous exercise or diet
routine within 4 weeks prior to screening. Subjects must be willing to maintain
his/her previous level of exercise for the duration of the study

12. Known history of seropositivity to human immunodeficiency virus (HIV) antibody;
hepatitis B surface antigen or hepatitis C antibody (HCV) associated with a positive
HCV RNA polymerase chain reaction at the screening visit

13. Positive urine drug test results during screening or history of drug or alcohol abuse
within a year prior to the screening visit

14. Any hospitalization within 60 days prior to the screening visit

15. 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

16. History of a hypersensitivity reaction to doxycycline or to other tetracycline drugs

17. Previous exposure to any biological therapeutic agent, excepting vaccines