This study is a dose finding study to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of subcutaneous CBP-4888 in hospitalized participants with Preterm Preeclampsia receiving Standard of Care, Expectant Management. Eligible participants are between 26 +0/7 and 35 +6/7 weeks gestational age and clinically appropriate for inpatient expectant management. Eligible participants will receive standard of care expectant management for their pregnancy with the only study interventions being one subcutaneous dose of CBP-4888.

Participants will:

• receive a single subcutaneous injection dose of CBP-4888 and will be followed through delivery and for 42 days (+14 days) after delivery. Participants will be followed through 6 weeks post delivery.
• Infants will be evaluated immediately postpartum and then followed through 24 months of age with standard infant and pediatric assessments with phone calls made to parents.

An Open-Label, Dose Finding Study to Evaluate the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Subcutaneous CBP-4888 in Hospitalized Participants with Preterm Preeclampsia Receiving Standard of Care, Expectant Management. The study will follow a single ascending dose design, with up to 60 participants enrolled across 6 dose level groups. For each of the planned six dose levels, all 4 participants will receive a single SC injection dose of IP (CBP-4888) + standard of care (SOC)/Expectant Management + additional safety surveillance for the mother and neonate through delivery and for 42 days (+14 days) after delivery. Infants will be followed for up to 24 months.

Inclusion Criteria:

• Hospitalized with a hypertensive disorder of pregnancy (preeclampsia) defined by elevated blood pressure after 20 weeks gestation with proteinuria or, in the absence of proteinuria, with evidence of organ dysfunction (e.g., thrombocytopenia, renal insufficiency, or impaired liver function), and expected to remain hospitalized through delivery
• The subject has given written consent to participate in the study.
• Pregnant participants aged 18 to 45 years of age
• Gestational age at Day 1 between 26 weeks 0/7 days and 35 weeks 6/7 days
• Deemed clinically stable and suitable for expectant management for at least 72 hours post CBP-4888 administration
• The woman carries a singleton pregnancy
• Anticipate that hospitalization will continue through delivery

Exclusion Criteria:

• Placenta previa, abruption, accreta, or persistent unexplained vaginal bleeding.
• Fetal growth restriction (<3rd percentile, or <10th percentile with abnormal Doppler) or known major chromosomal/genetic abnormalities.
• Maternal conditions requiring immediate delivery (e.g., severe hypertension, eclampsia, non-reassuring fetal status, pulmonary edema).
• Known active maternal infections considered to potentially affect placental function.
• Significant maternal medical conditions (e.g., HELLP syndrome, advanced kidney disease, severe cardiac disease, uncontrolled neurological disorder, lupus with nephritis/cerebritis).
• Use of another investigational drug within 30 days prior to study entry.
• Any other condition that, in the investigator's judgment, poses risk to mother or fetus.