Phase 2 Study on the Pharmacokinetics and Safety of RLYB212 in Pregnant Women at Higher Risk for HPA-1a Alloimmunization

A Phase 2, Multicenter, Open-label Study to Evaluate the Pharmacokinetics and Safety of RLYB212 in Pregnant Women at Higher Risk for HPA-1a Alloimmunization

The purpose of this Phase 2 study is to assess the pharmacokinetics (PK) and safety of RLYB212 in HPA-1b/b pregnant women at higher risk for HPA-1a alloimmunization and FNAIT.

Study Overview

• Status: Terminated
• Conditions: Fetal and Neonatal Alloimmune Thrombocytopenia
• Intervention / Treatment: Drug: Anti-(integrin beta-3) human monoclonal antibody

Detailed Description

This study is a single-arm, open-label, multicenter study of RLYB212 in HPA-1b/b pregnant participants at higher risk for the occurrence of HPA-1a alloimmunization and FNAIT. A laboratory testing paradigm will be applied at screening to identify women at higher risk for HPA-1a alloimmunization. Study IPA2202 is comprised of three phases: a two-part screening phase, an antenatal treatment phase, and a postpartum follow-up phase. Study duration for each participant is anticipated to be ~44 weeks, inclusive of the screening visits through the Week 10 postpartum visit.

• Study Type: Interventional
• Enrollment (Actual): 1
• Phase: Phase 2

Contacts and Locations

Study Locations

• Netherlands
  • South Holland
    • Leiden, South Holland, Netherlands, 2333
      • Leids Universitair Medisch Centrum
• Norway
  • Oslo County
    • Oslo, Oslo County, Norway, 0450
      • Oslo University Hospital- Ullevål
• Sweden
  • Stockholm County
    • Stockholm, Stockholm County, Sweden, 118 83
      • Södersjukhuset

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

Pregnant women who present at Gestational Week 6 or after and confirmed to be: HPA-1b/b (HPA-1a negative), HLA-DRB3*01:01 positive, Anti-HPA-1a alloantibody negative, Carrying an HPA-1a/b (HPA-1a positive) fetus

Exclusion Criteria:

• Prior history of HPA-1a related fetal and neonatal alloimmune thrombocytopenia
• Multiple pregnancy (more than 1 fetus)
• Prior history of platelet transfusion or other blood transfusions
• Known sensitivity and/or immediate hypersensitivity to any components of RLYB212 or its formulation
• Any co-morbid medical or obstetric condition(s), laboratory abnormality, concomitant treatment, or other reason that, in the investigator's opinion, could adversely affect the safety of the participant and/or fetus, impair the assessment of study results, or preclude compliance with the study

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: RLYB212; RLYB212 Subcutaneous injection	Drug: Anti-(integrin beta-3) human monoclonal antibody; human monoclonal anti-human platelet antigen (HPA)-1a immunoglobulin G antibody; Other Names: RLYB212

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of Participants With Treatment Related Adverse Events as Defined by CTCAE 5.0	Adverse Events will be collected throughout the study from the time of screening part 2 and beyond until the end of study visit (10 weeks postpartum for the maternal participant and 4-6 weeks of age for the neonate/infant). MedDRA version 27.0 or above will be used to code the AEs. All maternal AEs will be graded according to the National Cancer Institute of Common Terminology Criteria for AEs (CTCAE version 5.0 or higher) and Maternal and Fetal Adverse Event Terminology (MFAET version 1.0 or higher).	Approx. Gestational Week (GW) <16, 16, 18, 20, 24, 26, 28, 30, 32, 34, 36, 38; at birth (~40), Post Partum (PP) Week 4, 10 week
Maternal Exposure to RLYB212 as Measured in Serum	The PK profile of RLYB212 during pregnancy following repeat SC administration was evaluated. Results reported in concentration only.	Approx. GW 16, 18, 20, 24, 26, 28, 30, 32, 34, 36, 38, at birth (~40), PP Week 4

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Neonatal Exposure to RLYB212 as Measured in Cord Blood	The neonatal exposure to RLYB212 was to be measured by sampling and measuring the concentration of RLYB212 in a cord blood sample.	At birth (~GW 40)
Number of HPA-1a Positive Neonates With Treatment Related Adverse Events as Defined by CTCAE v5.0	The safety of RLYB212 in the HPA-1a positive neonate would be assessed by treatment related adverse events as defined by CTCAE v5.0	At birth (~GW 40), Approx. PP Week 4
Pregnancy Outcomes: Incidence of Live Births, Spontaneous Abortions, Elective Abortions, Still Births or Premature Births	The pregnancy and neonatal outcomes following antenatal RLYB212 administration was assessed by reporting incidence of live births, spontaneous abortions, elective abortions, still births or premature births.	At birth (~GW 40)
Frequency of Neonatal Thrombocytopenia as Measured by Platelet Count Within 72 Hours of Delivery	The occurrence of neonatal thrombocytopenia following antenatal RLYB212 administration was assessed.	At birth (~GW 40)
Frequency of HPA-1a Alloimmunization as Measured by Anti-HPA-1a Alloantibodies	The occurrence of HPA-1a alloimmunization was to be assessed by looking for anti-HPA-1a alloantibodies in the woman's blood.	Approx. PP Week 10
Neonatal Outcomes: General Health and Overall Status as Defined by Absolute Values and Percentiles	Neonate general health measured by Body Length (for age percentile) , Head Circumference (for age percentile), Weight for Height Percentile (for age percentile)	4-6 weeks following delivery
Participants That Test Positive for Anti-RLYB212 Antibodies as Measured in Their Serum	Participants that test positive for Anti-RLYB212 antibodies as measured in their serum. The immunogenicity of RLYB212 was assessed by testing serum samples for absence or presence of ADAs. The detection and characterization of ADA against RLYB212 will be performed using a validated assay method by or under the supervision of the Sponsor. The titer of confirmed positive samples will be reported as well as the presence of neutralizing antibodies. Other analyses may be performed to verify the stability of antibodies to RLYB212, and/or further characterize the immunogenicity of RLYB212.	16, 20, 24, 28, 32, 36, at birth (~40), PP Week 4

Collaborators and Investigators

• Sponsor: Rallybio

Study record dates

Study Major Dates

• Study Start (Actual): November 21, 2024
• Primary Completion (Actual): October 1, 2025
• Study Completion (Actual): October 1, 2025

Study Registration Dates

• First Submitted: May 21, 2024
• First Submitted That Met QC Criteria: May 24, 2024
• First Posted (Actual): May 30, 2024

Study Record Updates

• Last Update Posted (Actual): March 6, 2026
• Last Update Submitted That Met QC Criteria: March 3, 2026
• Last Verified: March 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Cytopenia; Infant, Newborn, Diseases; Hematologic Diseases; Blood Platelet Disorders; Thrombocytopenia; Congenital, Hereditary, and Neonatal Diseases and Abnormalities; Hemic and Lymphatic Diseases; Thrombocytopenia, Neonatal Alloimmune; Immunologic Factors; Physiological Effects of Drugs; Antibodies; Antibodies, Monoclonal
• Other Study ID Numbers: IPA2202; 2024-512651-20-00 (Ctis)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: Yes