Rallybio Reveals FNAIT Risk Analysis in Diverse Populations

Rallybio Corporation, a clinical-stage biotechnology company focused on developing therapies for rare diseases, has unveiled findings from an extensive epidemiological study on the risk of fetal and neonatal alloimmune thrombocytopenia (FNAIT) across diverse ancestries. The study indicates that the prevalence of pregnancies at higher risk for FNAIT may be significantly higher than previously estimated, especially among non-Caucasian populations. This discovery has important implications for prenatal care and the potential market for Rallybio's treatment candidate, RLYB212.

The study analyzed extensive genomic datasets to evaluate the frequency of genetic markers associated with FNAIT risk in various ancestries. The findings confirmed that Caucasian populations have the highest proportion of women with genetic markers indicating a higher risk for FNAIT, specifically those who are HPA-1a negative and HLA-DRB3*01:01 positive. Additionally, the study provided the first substantial evidence of the presence of these genetic markers in non-Caucasian populations, significantly broadening the understanding of FNAIT risk globally.

The data suggests that the number of pregnancies at higher risk for FNAIT annually has been previously underestimated. In North America and major European countries, more than 30,000 pregnancies each year are now estimated to be at higher risk for FNAIT, marking a 40% increase from prior estimates. Rallybio plans to present the full details of this analysis at a scientific conference in the fourth quarter of 2024.

Stephen Uden, MD, Chief Executive Officer of Rallybio, emphasized the significance of these findings. He noted that this large-scale analysis provides new insights into the prevalence of FNAIT risk among diverse populations. Dr. Uden highlighted the importance of incorporating FNAIT risk screening into standard prenatal care, which could ensure prophylactic treatment for those at higher risk, should RLYB212 receive approval.

Based on the new data, Rallybio now projects that RLYB212 could represent a market opportunity exceeding $1.6 billion. The company partnered with HealthLumen, an expert in epidemiological modeling, to conduct this study. Genetic data were sourced from gnomAD v4, encompassing exome and genome sequences from approximately 810,000 individuals, and the US National Marrow Donor Registry, which includes data from about 2.7 million individuals.

The study's findings revealed that the highest risk of alloimmunization and FNAIT was among European Caucasian populations, aligning with existing literature. Hispanic White populations also showed a significant proportion of women at higher risk, while Hispanic Black and Non-Hispanic Black populations exhibited a moderate risk. The risk was lower among South Asian, East Asian, and Amerindigenous populations compared to European Caucasians.

Rallybio is developing RLYB212, a novel human monoclonal antibody targeting HPA-1a, to prevent alloimmunization in pregnant women, thereby mitigating the risk of FNAIT and its severe consequences for fetuses and newborns. The company plans to initiate a Phase 2 dose confirmation study for RLYB212 in the second half of 2024. Additionally, Rallybio is conducting a non-interventional natural history study of FNAIT to gather contemporary data on HPA-1a alloimmunization in racially and ethnically diverse populations. As of May 1, 2024, approximately 10,000 pregnant women have been screened in this ongoing study.

FNAIT is a rare but potentially life-threatening condition that can lead to severe bleeding in fetuses and newborns due to an immune incompatibility between the mother and the fetus. This incompatibility arises from differences in the HPA-1 platelet antigen. Currently, there is no approved therapy for preventing or treating FNAIT prenatally.

Rallybio, headquartered in New Haven, Connecticut, is committed to developing transformative therapies for severe and rare diseases. The company's pipeline includes RLYB212 and RLYB116, an inhibitor of complement component 5 (C5) for treating complement dysregulation disorders, among other preclinical programs.