The primary objective of the study is to evaluate the safety and tolerability of single doses of REGN9933 in healthy participants The secondary objectives of the study are to: * Evaluate the effects of single doses of REGN9933 on intrinsic/common pathway coagulation * Evaluate the effects of single doses of REGN9933 on extrinsic/common pathway coagulation * Characterize the drug concentration profiles and pharmacokinetic (PK) following single escalating doses of REGN9933 * Characterize the concentration profiles of total FXI following single escalating doses of REGN9933 * Assess the immunogenicity of single doses of REGN9933
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
QUADRUPLE
Enrollment
56
Administered intravenously (IV) or subcutaneous (SC) per the protocol
Placebo to match REGN9933 in same form; placebo administered IV or SC per the protocol
Regeneron Study Site
Edegem, Antwerp, Belgium
Incidence and severity of treatment emergent adverse events (TEAE)
Time frame: Until resolution of pharmacodynamic (PD) effects; approximately 36 days
Change from baseline in activated partial thromboplastin time (aPTT)
Time frame: Until resolution of PD effects; approximately 36 days
Change from baseline in prothrombin time (PT)
Time frame: Until resolution of PD effects; approximately 36 days
Concentration of REGN9933 in serum
Time frame: Until resolution of PD effects; approximately 36 days
Change from baseline in total Factor XI (FXI) concentrations
Time frame: Until resolution of PD effects; approximately 36 days
The incidence of antidrug antibodies (ADAs) to REGN9933 over time
Time frame: Until resolution of PD effects; approximately 36 days
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