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

NCT06435845 | Terminated Phase 2 Results DMC FDA Drug

• 2 other identifiers: IPA22022024-512651-20-00
• Study Type: interventional
• Target: 1
• Locations: 3 countries
• Sites: 3

Brief Summary

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.

Conditions

Fetal and Neonatal Alloimmune Thrombocytopenia

Outcome Measures

Primary Outcomes (2)

• 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 Outcomes (7)

• Neonatal Exposure to RLYB212 as Measured in Cord Blood

  At birth (~GW 40)

• Number of HPA-1a Positive Neonates With 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

  At birth (~GW 40)

• Frequency of Neonatal Thrombocytopenia as Measured by Platelet Count Within 72 Hours of Delivery

  At birth (~GW 40)

• Frequency of HPA-1a Alloimmunization as Measured by Anti-HPA-1a Alloantibodies

  Approx. PP Week 10

Study Arms (1)

RLYB212

EXPERIMENTAL

RLYB212 Subcutaneous injection

Drug: Anti-(integrin beta-3) human monoclonal antibody

Interventions

Anti-(integrin beta-3) human monoclonal antibody DRUG

human monoclonal anti-human platelet antigen (HPA)-1a immunoglobulin G antibody

Also known as: RLYB212

RLYB212

Eligibility Criteria

• Age: 18 Years - 45 Years
• Gender Eligibility Details: Pregnant women
• Healthy Volunteers: No
• Age Groups: Adult (18-64)

You may qualify if:

• 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

You may not qualify if:

• 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

Sponsors & Collaborators

• Rallybio: lead

Study Sites (3)

Leids Universitair Medisch Centrum

Leiden, South Holland, 2333, Netherlands

Location

Oslo University Hospital- Ullevål

Oslo, Oslo County, 0450, Norway

Location

Södersjukhuset

Stockholm, Stockholm County, 118 83, Sweden

Location

MeSH Terms

Conditions

Thrombocytopenia, Neonatal Alloimmune

Condition Hierarchy (Ancestors)

Thrombocytopenia; Blood Platelet Disorders; Hematologic Diseases; Hemic and Lymphatic Diseases; Cytopenia; Infant, Newborn, Diseases; Congenital, Hereditary, and Neonatal Diseases and Abnormalities

Limitations and Caveats

This study was terminated early by the sponsor due to insufficient drug exposure to achieve the intended therapeutic effect. Only one participant (pregnant woman) was enrolled in the study prior to the sponsor's decision to terminate. This participant successfully delivered one neonate. Given the premature study termination and enrollment of a single mother-infant pair, the planned statistical analyses were not performed.

Results Point of Contact

• Title: Head of Development Operations
• Organization: Rallybio IPA, LLC

clinicaltrials@rallybio.com

+1 203-859-3820

Publication Agreements

• PI is Sponsor Employee: No
• Restrictive Agreement: No

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: NA
• Masking: NONE
• Purpose: PREVENTION
• Intervention Model: SINGLE GROUP
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: May 21, 2024
• First Posted: May 30, 2024
• Study Start: November 21, 2024
• Primary Completion: October 1, 2025
• Study Completion: October 1, 2025
• Last Updated: March 6, 2026
• Results First Posted: March 6, 2026

Record last verified: 2026-03

Data Sharing

• IPD Sharing: Will not share

Locations

SE (1); NO (1); NL (1)