Assessment of Gastrointestinal Blood Loss After Receiving Aspirin or Aspirin Plus Rivaroxaban, or Aspirin Plus REGN9933, or Aspirin Plus REGN7508 in Healthy Adult Participants

Key Inclusion Criteria: 1. Body mass index between 18.0 and 32.5 kg/m2 (inclusive) at the screening visit 2. Judged by the investigator to be in good health based on medical history, physical examination, vital sign measurements, and electrocardiograms (ECGs) performed at screening and/or prior to administration of initial dose of study treatment 3. Normal aPTT, normal PT, and normal platelet counts at screening period and at the day 1 visit as defined by the local laboratory 4. Hemoglobin values within the normal range, per local laboratory, at the screening and day 1 visits 5. Negative FOBT at Baseline (visit 2) and visit 3 as defined in the protocol Key Exclusion Criteria: 1. History of any major surgical procedure or clinically significant physical trauma in the last 6 months, in the opinion of the investigator, that may pose a risk to the participant by study participation 2. Whole blood donation within the previous 56 days or plasma donation within the previous 7 days prior to the screening visit 3. Hospitalized for any reason within 30 days of the screening visit 4. Estimated glomerular filtrate rate (eGFR) of \<60 mL/min/1.73m2 at screening as described in the protocol. 5. Current smoker or former smoker, including e-cigarettes, who stopped smoking within 12 months prior to the screening visit 6. History of illicit drug or alcohol abuse within the last 2 years prior to the day 1 visit 7. Use of any prescription and nonprescription medications or nutritional supplements from approximately 2 weeks or 5 half-lives, as described in protocol 8. Has elective surgery planned to occur prior to end of study (EOS) Note: Other Protocol Defined Inclusion/ Exclusion Criteria Apply