Trial Outcomes & Findings for Phase 2 Study on the Pharmacokinetics and Safety of RLYB212 in Pregnant Women at Higher Risk for HPA-1a Alloimmunization (NCT NCT06435845)
NCT ID: NCT06435845
Last Updated: 2026-03-06
Results Overview
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).
TERMINATED
PHASE2
1 participants
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
2026-03-06
Participant Flow
Participant milestones
| Measure |
RLYB212
RLYB212 Subcutaneous injection
|
|---|---|
|
Overall Study
STARTED
|
1
|
|
Overall Study
COMPLETED
|
1
|
|
Overall Study
NOT COMPLETED
|
0
|
Reasons for withdrawal
Withdrawal data not reported
Baseline Characteristics
Phase 2 Study on the Pharmacokinetics and Safety of RLYB212 in Pregnant Women at Higher Risk for HPA-1a Alloimmunization
Baseline characteristics by cohort
| Measure |
RLYB212
n=1 Participants
RLYB212 Subcutaneous injection
|
|---|---|
|
Age, Categorical
<=18 years
|
0 Participants
n=41 Participants
|
|
Age, Categorical
Between 18 and 65 years
|
1 Participants
n=41 Participants
|
|
Age, Categorical
>=65 years
|
0 Participants
n=41 Participants
|
|
Sex: Female, Male
Female
|
1 Participants
n=41 Participants
|
|
Sex: Female, Male
Male
|
0 Participants
n=41 Participants
|
|
Race (NIH/OMB)
American Indian or Alaska Native
|
0 Participants
n=41 Participants
|
|
Race (NIH/OMB)
Asian
|
0 Participants
n=41 Participants
|
|
Race (NIH/OMB)
Native Hawaiian or Other Pacific Islander
|
0 Participants
n=41 Participants
|
|
Race (NIH/OMB)
Black or African American
|
0 Participants
n=41 Participants
|
|
Race (NIH/OMB)
White
|
1 Participants
n=41 Participants
|
|
Race (NIH/OMB)
More than one race
|
0 Participants
n=41 Participants
|
|
Race (NIH/OMB)
Unknown or Not Reported
|
0 Participants
n=41 Participants
|
|
Ethnicity (NIH/OMB)
Hispanic or Latino
|
0 Participants
n=41 Participants
|
|
Ethnicity (NIH/OMB)
Not Hispanic or Latino
|
1 Participants
n=41 Participants
|
|
Ethnicity (NIH/OMB)
Unknown or Not Reported
|
0 Participants
n=41 Participants
|
PRIMARY outcome
Timeframe: 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 weekPopulation: This is reported as the number of participants that experienced as AE over the entire study duration. Enrollment in the study was terminated after enrolling one pregnant woman. Dosing with RLYB212 was stopped after the administration of two doses of the planned 7 due to the inability to measure drug concentrations in the blood samples. The participant was followed for safety assessments only starting at GW 24.
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).
Outcome measures
| Measure |
RLYB212
n=1 Participants
RLYB212 Subcutaneous injection
|
|---|---|
|
Number of Participants With Treatment Related Adverse Events as Defined by CTCAE 5.0
|
1 Participants
|
PRIMARY outcome
Timeframe: Approx. GW 16, 18, 20, 24, 26, 28, 30, 32, 34, 36, 38, at birth (~40), PP Week 4Population: Gestational weeks 16, 18, 20, and 24 PK concentrations are reported (0 = BLQ). Blood samples were not collected for GWs 26, 28, 30, 32, 34, 36, 38, at birth (\~40), PP Week 4. Enrollment in the study was terminated after enrolling one pregnant woman. Dosing with RLYB212 was stopped after the administration of two doses of the planned 7 due to the inability to measure drug concentrations in the blood samples. The participant was followed for safety assessments only starting at GW 24.
The PK profile of RLYB212 during pregnancy following repeat SC administration was evaluated. Results reported in concentration only.
Outcome measures
| Measure |
RLYB212
n=1 Participants
RLYB212 Subcutaneous injection
|
|---|---|
|
Maternal Exposure to RLYB212 as Measured in Serum
16 weeks Gestational Age
|
0 ng/mL
|
|
Maternal Exposure to RLYB212 as Measured in Serum
18 weeks Gestational Age
|
1.08363 ng/mL
|
|
Maternal Exposure to RLYB212 as Measured in Serum
20 weeks Gestational Age
|
0 ng/mL
|
|
Maternal Exposure to RLYB212 as Measured in Serum
24 weeks Gestational Age
|
0 ng/mL
|
SECONDARY outcome
Timeframe: At birth (~GW 40)Population: No data is reported for this outcome since the sample was inadvertently not collected from the single enrolled participant. Enrollment in the study was terminated after enrolling one pregnant woman. Dosing with RLYB212 was stopped after the administration of two doses of the planned 7 due to the inability to measure drug concentrations in the blood samples. The participant was followed for safety assessments only starting at gestational week 24.
The neonatal exposure to RLYB212 was to be measured by sampling and measuring the concentration of RLYB212 in a cord blood sample.
Outcome measures
| Measure |
RLYB212
RLYB212 Subcutaneous injection
|
|---|---|
|
Neonatal Exposure to RLYB212 as Measured in Cord Blood
|
0 Participants
|
SECONDARY outcome
Timeframe: At birth (~GW 40), Approx. PP Week 4The safety of RLYB212 in the HPA-1a positive neonate would be assessed by treatment related adverse events as defined by CTCAE v5.0
Outcome measures
| Measure |
RLYB212
n=1 Participants
RLYB212 Subcutaneous injection
|
|---|---|
|
Number of HPA-1a Positive Neonates With Treatment Related Adverse Events as Defined by CTCAE v5.0
|
1 participants
|
SECONDARY outcome
Timeframe: At birth (~GW 40)Population: The outcome for the one pregnancy is reported here. Enrollment in the study was terminated after enrolling one pregnant woman.
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.
Outcome measures
| Measure |
RLYB212
n=1 Participants
RLYB212 Subcutaneous injection
|
|---|---|
|
Pregnancy Outcomes: Incidence of Live Births, Spontaneous Abortions, Elective Abortions, Still Births or Premature Births
Live Birth
|
1 Participants
|
|
Pregnancy Outcomes: Incidence of Live Births, Spontaneous Abortions, Elective Abortions, Still Births or Premature Births
spontaneous abortion
|
0 Participants
|
|
Pregnancy Outcomes: Incidence of Live Births, Spontaneous Abortions, Elective Abortions, Still Births or Premature Births
elective abortion
|
0 Participants
|
|
Pregnancy Outcomes: Incidence of Live Births, Spontaneous Abortions, Elective Abortions, Still Births or Premature Births
still birth
|
0 Participants
|
|
Pregnancy Outcomes: Incidence of Live Births, Spontaneous Abortions, Elective Abortions, Still Births or Premature Births
premature birth
|
0 Participants
|
SECONDARY outcome
Timeframe: At birth (~GW 40)Population: No results are reported for the outcome as the sample was inadvertently not collected at the time of birth. Enrollment in the study was terminated after enrolling one pregnant woman.
The occurrence of neonatal thrombocytopenia following antenatal RLYB212 administration was assessed.
Outcome measures
| Measure |
RLYB212
RLYB212 Subcutaneous injection
|
|---|---|
|
Frequency of Neonatal Thrombocytopenia as Measured by Platelet Count Within 72 Hours of Delivery
|
0 Participants
|
SECONDARY outcome
Timeframe: Approx. PP Week 10Population: No blood sample was collected for this outcome. Enrollment in the study was terminated after enrolling one pregnant woman. Dosing with RLYB212 was stopped after the administration of two doses of the planned 7 due to the inability to measure drug concentrations in the blood samples. The participant was followed for safety assessments only starting at GW 24.
The occurrence of HPA-1a alloimmunization was to be assessed by looking for anti-HPA-1a alloantibodies in the woman's blood.
Outcome measures
| Measure |
RLYB212
RLYB212 Subcutaneous injection
|
|---|---|
|
Frequency of HPA-1a Alloimmunization as Measured by Anti-HPA-1a Alloantibodies
|
0 Participants
|
SECONDARY outcome
Timeframe: 4-6 weeks following deliveryPopulation: Results are provided for the single participants neonate only, no analyses were possible due to termination of the study.
Neonate general health measured by Body Length (for age percentile) , Head Circumference (for age percentile), Weight for Height Percentile (for age percentile)
Outcome measures
| Measure |
RLYB212
n=1 Participants
RLYB212 Subcutaneous injection
|
|---|---|
|
Neonatal Outcomes: General Health and Overall Status as Defined by Absolute Values and Percentiles
Head Circumference
|
97.5 Percentile
|
|
Neonatal Outcomes: General Health and Overall Status as Defined by Absolute Values and Percentiles
Body Length
|
90 Percentile
|
|
Neonatal Outcomes: General Health and Overall Status as Defined by Absolute Values and Percentiles
Weight for Height
|
97.5 Percentile
|
SECONDARY outcome
Timeframe: 16, 20, 24, 28, 32, 36, at birth (~40), PP Week 4Population: Participants that test positive at gestational weeks 16, 20, 24, and at birth are reported. Blood samples were not collected for GWs 28, 32, 36, and PP Week 4. Enrollment in the study was terminated after enrolling one pregnant woman. Dosing with RLYB212 was stopped after the administration of two doses of the planned 7 due to the inability to measure drug concentrations in the blood samples. The participant was followed for safety with unnecessary blood draws stopped.
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.
Outcome measures
| Measure |
RLYB212
n=1 Participants
RLYB212 Subcutaneous injection
|
|---|---|
|
Participants That Test Positive for Anti-RLYB212 Antibodies as Measured in Their Serum
16 weeks Gestational Age
|
0 Participants
|
|
Participants That Test Positive for Anti-RLYB212 Antibodies as Measured in Their Serum
20 weeks Gestational Age
|
0 Participants
|
|
Participants That Test Positive for Anti-RLYB212 Antibodies as Measured in Their Serum
24 weeks Gestational Age
|
0 Participants
|
|
Participants That Test Positive for Anti-RLYB212 Antibodies as Measured in Their Serum
At time of birth
|
0 Participants
|
Adverse Events
RLYB212
Infant of Woman Treated With RLYB212
Serious adverse events
Adverse event data not reported
Other adverse events
| Measure |
RLYB212
n=1 participants at risk
RLYB212 Subcutaneous injection
|
Infant of Woman Treated With RLYB212
n=1 participants at risk
Infant of woman treated with RLYB212
|
|---|---|---|
|
Infections and infestations
Influenza
|
100.0%
1/1 • Until end of study (up to 10 weeks postpartum)
AEs will be spontaneously reported by the participant in response to general questions of how they are feeling. Specific new AEs will not be solicited, although follow -up questions about prior AEs should be asked if not volunteered spontaneously by the participant.
|
0.00%
0/1 • Until end of study (up to 10 weeks postpartum)
AEs will be spontaneously reported by the participant in response to general questions of how they are feeling. Specific new AEs will not be solicited, although follow -up questions about prior AEs should be asked if not volunteered spontaneously by the participant.
|
|
Skin and subcutaneous tissue disorders
RASH IN LOWER EXTREMITIES
|
100.0%
1/1 • Until end of study (up to 10 weeks postpartum)
AEs will be spontaneously reported by the participant in response to general questions of how they are feeling. Specific new AEs will not be solicited, although follow -up questions about prior AEs should be asked if not volunteered spontaneously by the participant.
|
0.00%
0/1 • Until end of study (up to 10 weeks postpartum)
AEs will be spontaneously reported by the participant in response to general questions of how they are feeling. Specific new AEs will not be solicited, although follow -up questions about prior AEs should be asked if not volunteered spontaneously by the participant.
|
|
Infections and infestations
GENITAL HERPES REACTIVATION
|
100.0%
1/1 • Until end of study (up to 10 weeks postpartum)
AEs will be spontaneously reported by the participant in response to general questions of how they are feeling. Specific new AEs will not be solicited, although follow -up questions about prior AEs should be asked if not volunteered spontaneously by the participant.
|
0.00%
0/1 • Until end of study (up to 10 weeks postpartum)
AEs will be spontaneously reported by the participant in response to general questions of how they are feeling. Specific new AEs will not be solicited, although follow -up questions about prior AEs should be asked if not volunteered spontaneously by the participant.
|
|
Investigations
CARDIAC MURMUR GRAD 2-3
|
0.00%
0/1 • Until end of study (up to 10 weeks postpartum)
AEs will be spontaneously reported by the participant in response to general questions of how they are feeling. Specific new AEs will not be solicited, although follow -up questions about prior AEs should be asked if not volunteered spontaneously by the participant.
|
100.0%
1/1 • Until end of study (up to 10 weeks postpartum)
AEs will be spontaneously reported by the participant in response to general questions of how they are feeling. Specific new AEs will not be solicited, although follow -up questions about prior AEs should be asked if not volunteered spontaneously by the participant.
|
Additional Information
Results disclosure agreements
- Principal investigator is a sponsor employee
- Publication restrictions are in place