This is a Phase 1, Randomized, Single-blind, Placebo-controlled Study to Assess the Safety, Pharmacokinetics (PK), and Pharmacodynamics (PD) of BEAM-103 in Healthy Subjects

• BEAM-103 (Drug): • BEAM-103 is a monoclonal antibody administered as a single intravenous dose
• Placebo Comparator (Drug): • The matching placebo comparator is administered as a single intravenous dose

Primary outcomes

• To determine the safety and tolerability of single ascending doses of BEAM-103 [from enrollment to the end of study at 5 months]: Incidence of treatment-emergent AEs, serious AEs, severe AEs, AEs related to BEAM-103

Secondary outcomes

• Change in Free Stem Cell Factor (SCF) in Peripheral Blood Over Time [from the start of treatment to the end of study at 5 months]: Concentration of SCF in peripheral blood measured in nanograms per milliliter (mL)
• Change in Tryptase Level in Peripheral Blood Over Time [from the start of treatment to the end of study at 5 months]: Serum tryptase concentration measured in nanograms per milliliter (ng/mL)
• Change in Reticulocyte Count in Peripheral Blood Over Time [From enrollment to end of study at 5 months]: Absolute reticulocyte count measured in cells per microliter (cells/µL)
• Change in Neutrophil Count in Peripheral Blood Over Time [From enrollment to end of study at 5 months]: Absolute neutrophil count measured in cells per microliter (cells/µL)
• Maximum Observed Plasma Concentration (Cmax) [From enrollment to end of study at 5 months]: Cmax will be calculated as the highest observed plasma/blood/serum concentration following drug administration
• Area Under the Plasma Concentration-Time Curve to Last Quantifiable Concentration (AUClast) [From enrollment to end of study at 5 months]: AUClast will be calculated from time zero to the time of the last quantifiable concentration
• Area Under the Plasma Concentration-Time Curve to Infinity (AUC∞) [From enrollment to end of study at 5 months]: AUC∞ will be calculated as AUClast plus Clast divided by λz
• Terminal Elimination Half-Life (t½) [From enrollment to end of study at 5 months]: t½ will be estimated from the terminal elimination phase of the plasma concentration-time curve

Sex: All, ages: 18 Years to 55 Years, accepts healthy volunteers

Inclusion Criteria:

* Ages 18 to ≤55 years
* Body mass index (BMI) of 18.5 to 25 kg/m2
* Morning neutrophil count ≥2.6 × 109 cells/L for Black/African American subjects or ≥3.5 ×109 cells/L for Caucasian/Other subjects
* Baseline hemoglobin value of ≥14 g/dL for males and ≥12 g/dL for females
* Baseline platelet count of >150 × 109/L.
* Subjects must be in general good health without significant medical conditions (based on physical exam, electrocardiogram (ECG), and laboratory test results with no clinically significant deviations), per the investigator's assessment

Exclusion Criteria:

* Known hypersensitivity to any component of the investigational medicinal product (IMP).
* Participation in another clinical trial involving treatment with an investigational agent within 90 days of informed consent is prohibited.
* Positive serum pregnancy test or breastfeeding at screening (female participants).
* Live virus vaccination within 4 weeks prior to signing informed consent.
* Any severe or uncontrolled medical condition (eg. severe asthma or severe peanut allergy) that in the opinion of the investigator would put the subject at undue medical risk or impair the ability to interpret study results.