A Study of Nipocalimab in Reducing the Risk of Fetal and Neonatal Alloimmune Thrombocytopenia (FNAIT)

• Nipocalimab (Drug), also known as JNJ-80202135, JNJ-86507083: Nipocalimab will be administered intravenously.
• Placebo (Drug): Placebo will be administered intravenously.

Primary outcomes

• Fetus/Neonate with Outcome of Death or Adjudicated Severe Bleeding or Platelet Count Less Than (<) 30*10^9/L [Up to 1 week post birth]: Outcome of fetus/neonate death or adjudicated severe bleeding up to the first week post birth or platelet count <30*10\^9/L will be reported.

Secondary outcomes

• Neonate/Fetus With Adjudicated Bleeding [Up to 1 Week post birth]: Neonate/fetus With adjudicated bleeding will be reported.
• Platelet Count at Birth in a Neonate [At birth]: Platelet count at birth in a neonate will be reported.
• Neonate/Fetus with Outcome of Death [Up to 1 Week post birth]: Fetus/neonate with outcome of death will be reported.
• Platelet Count at Birth <10×10^9/L in a Neonate [At birth]: Platelet count at birth <10×10\^9/L in a neonate will be reported.
• Platelet Count at Birth <30×10^9/ L In a Neonate [At birth]: Platelet count at birth <30×10\^9/L in a neonate will be reported.
• Platelet Count at Birth <50×10^9/L In a Neonate [At birth]: Platelet count at birth <50×10\^9/L in a neonate will be reported.
• Platelet Count at Birth <150×10^9/L In a Neonate [At birth]: Platelet count at birth <150×10\^9/L in a neonate will be reported.
• Nadir Platelet Count of a Neonate Over the First Week Post Birth [Upto 1 Week post birth]: Nadir platelet count in a neonate will be reported.
• Neonate/Fetus Requiring Platelet Transfusion(s) [Up to 1 Week post birth]: Neonate(s) who require at least one platelet transfusion(s) will be reported.
• Number of Platelet Transfusion(s) in Neonate/Fetus [Up to 1 Week post birth]: Number of Platelet transfusion(s) per neonate will be reported.
• Number of Donor Exposures for Platelet Transfusion(s) in Neonate/Fetus [Up to 1 Week post birth]: Number of donor exposures for neonates who received platelet transfusion(s) will be reported.
• Neonate/Fetus With Adjudicated Severe Bleeding [Up to 1 week post birth]: Neonate/Fetus With adjudicated severe bleeding will be reported.
• Neonates With Postnatal Intravenous Immunoglobulin (IVIG) for The Treatment of Thrombocytopenia [Up to 1 Week post birth]: Neonates with IVIG for the treatment of thrombocytopenia will be reported.
• Maternal Participants With Treatment-Emergent Adverse Event (TEAE) [From randomization up to 24 weeks postpartum]: Maternal participants with a TEAE will be reported. An adverse event (AE) is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the intervention under study. TEAEs are defined as AEs with onset or worsening on or after date of first dose of study treatment.
• Maternal Participants With Serious Adverse Event (SAE) [From randomization up to 24 weeks postpartum]: Maternal participants with SAE will be reported. An adverse event (AE) is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the intervention under study. SAE is any untoward medical occurrence that at any dose that results in death, is life-threatening, requires inpatient hospitalization/prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect and is medically important.
• Maternal Participants With Adverse Event of Special Interest (AESI) [From randomization up to 24 weeks postpartum]: Maternal participants with an AESI will be reported. An adverse event (AE) is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the intervention under study. AESIs are considered as infections that are severe, hypoalbuminemia, deep vein thrombosis and/or pulmonary embolism, and clinically significant bleeding.
• Maternal Participants with TEAE Leading to Discontinuation of Study Intervention [Up to Week 104]: Maternal participants with TEAE leading to discontinuation of study intervention will be reported.
• Neonate/Infant with TEAE [Up to Week 104]: Neonatal/infant participants with a TEAE will be reported. An adverse event (AE) is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the intervention under study. TEAEs are defined as AEs with onset or worsening on or after date of first dose of study treatment.
• Neonate/Infant with SAE [Up to Week 104]: Neonatal/infant participants with SAE will be reported. An adverse event (AE) is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the intervention under study. An SAE is any untoward medical occurrence that at any dose that results in death, is life-threatening, requires inpatient hospitalization or prolongation of existing hospitalization, results in persistent or significant disability/incapacity, is a congenital anomaly/birth defect and is medically Important.
• Neonate/Infant with AESI [Up to Week 104]: Neonatal/infant participants with AESI will be reported. An adverse event (AE) is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the intervention under study. AESIs are considered as: In infants- clinically significant mortalities in fetus/neonates due to maternal infections, and hypogammaglobulinemia.
• Fetus/Neonate With TEAE of Bleeding [Up to Week 104]: Fetus/Neonate with TEAE of Bleeding will be reported. An adverse event (AE) is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the intervention under study. Treatment-emergent AEs are defined as AEs with onset or worsening on or after date of first dose of study treatment.
• Neonate With TEAE of Infection [Up to Week 104]: Neonate with TEAE of Infection will be reported. An AE is any untoward medical occurrence in a participant participating in a clinical study that does not necessarily have a causal relationship with the intervention under study. Treatment-emergent AEs are defined as AEs with onset or worsening on or after date of first dose of study treatment.
• Infant Development as Measured by Bayley Scales at Week 52 and Week 104 [At Week 52 and 104]: The Bayley Scales of Infant and Toddler Development include a set of individually administered developmental scales designed to measure current developmental functioning in infants and toddlers up to 42 months of age in the areas of cognition, language, motor skills, social-emotional, and adaptive behavior, with age adjusted for prematurity. The cognition, language, motor skills scales are directly administered to the infant, while social-emotional, and adaptive behavior scales are caregiver questionnaires. The scores are standardized using norm reference samples with representative demographics and age adjusted for prematurity.
• Maternal Participants With Antibodies to Nipocalimab Including Neutralizing Antibodies in Maternal Serum During Pregnancy and Postpartum [Up to Week 24]: Maternal participants with antibodies to nipocalimab including neutralizing antibodies in maternal serum during pregnancy and postpartum will be reported.

Sex: Female, ages: 18 Years to 45 Years

Inclusion Criteria:

* Pregnant and an estimated gestational age (GA; based on ultrasound dating) from Week 13 to 18 at randomization
* Has a history of greater than or equal to (>=) 1 prior pregnancy with fetal and neonatal alloimmune thrombocytopenia (FNAIT) (including neonatal platelet count less than (<) 150×10\^9/Liter) with none of them affected by fetal/neonatal intracranial hemorrhage (ICH) or severe hemorrhage based on a clinical review of the medical records
* Current pregnancy with presence of maternal anti- human platelet antigen (HPA)-1a alloantibody and positive fetal HPA-1a genotype as confirmed by cell-free fetal deoxyribonucleic acid (DNA) in maternal blood
* Health status considered stable by the investigator based on physical examination, medical history, vital signs, 12-lead Electrocardiogram (ECG), and clinical laboratory tests performed at screening
* For maternal participant and neonate/infant, willing to forego participation in another clinical study of an investigational therapy until the last follow-up visit

Exclusion Criteria:

* Currently pregnant with multiple gestations (twins or more)
* History of severe preeclampsia in a previous pregnancy
* History of myocardial infarction, unstable ischemic heart disease, or stroke
* Known allergies, hypersensitivity, or intolerance to nipocalimab or its excipients (refer to the Investigator Brochure (IB))
* Has any confirmed or suspected clinical immunodeficiency syndrome or has a family history of congenital or hereditary immunodeficiency unless confirmed absent in the participant

• Results publication: Baker P, Keshinro B, Stegmann B, Oey A, Shu C, Heerwegh D, Zaha R, Van Valkenburgh H. Plain Language Summary of Publication: Design of the Phase 3 FREESIA-1 and FREESIA-3 Trials of Nipocalimab in Fetal and Neonatal Alloimmune Thrombocytopenia. Am J Perinatol. 2026 Jul;43(9):1256-1263. doi: 10.1055/a-2761-1775. Epub 2025 Dec 29. PMID 41461173
• Results publication: Tiller H, Tiblad E, Baker P, Van Valkenburgh H, Heerwegh D, Keshinro B. Design of a Phase 3, Multicenter, Randomized, Placebo-Controlled, Double-Blind Study of Nipocalimab in Pregnancies at Risk for Fetal and Neonatal Alloimmune Thrombocytopenia. Am J Perinatol. 2026 Apr;43(5):648-656. doi: 10.1055/a-2666-5642. Epub 2025 Jul 28. PMID 40720970

• Janssen Research & Development, LLC Clinical Trial, Study director, Janssen Research & Development, LLC

NIH grants: 2023