- Data Support HPA-1a Negative Frequency of More than 2% in Nearly 200,000 Screened Pregnant Women -

- Among HPA-1a Negative Pregnant Women, Approximately 33% are at Higher Risk for Alloimmunization -

Rallybio Corporation (NASDAQ:RLYB), a clinical-stage biotechnology company committed to identifying and accelerating the development of life-transforming therapies for patients with severe and rare diseases, today announced the presentation of results from a fetal and neonatal alloimmune thrombocytopenia (FNAIT) systematic literature review and meta-analysis at the Academy of Managed Care Pharmacy (AMCP) 2024 Annual Meeting, which is taking place in New Orleans, LA. The results of this research found that, in a pooled analysis of 198,062 pregnant women, 2.2% were HPA-1a negative and 32.3% of these women were also HLA-DRB3*01:01 positive and therefore at ~25-fold higher risk for alloimmunization. These rates are consistent with Rallybio's current estimate of annual at-risk pregnancies and translate to tens of thousands of fetuses and newborns at risk each year for the potentially devastating consequences of FNAIT.

"We are pleased to establish a robust foundation of knowledge documenting the frequency of FNAIT risk as reported from a pooled analysis of peer-review literature, which is consistent with our current estimates," said Stephen Uden, M.D., Chief Executive Officer of Rallybio. "This information, in combination with data from our ongoing FNAIT natural history study, will enable us to create a shared understanding of the number of pregnant women and babies at higher risk of FNAIT annually, underscoring the importance of having an effective preventative therapeutic option."

Rallybio is developing RLYB212, a novel human monoclonal anti-HPA-1a antibody designed to prevent alloimmunization in pregnant women, thereby eliminating the risk of FNAIT and its potentially devastating consequences in their fetuses and newborns. Rallybio is on track to initiate a Phase 2 dose confirmation study for RLYB212 in pregnant women in the second half of 2024. The company is also conducting an ongoing FNAIT natural history study that will provide a contemporary dataset for HPA-1a alloimmunization frequency in a racially and ethnically diverse population, which is intended to support a future Phase 3 registration study for RLYB212. RLYB212 is the only investigational therapy currently reported to be in clinical development to address the needs of pregnant women at higher risk of FNAIT who have not alloimmunized.

The poster, titled "Fetal and Neonatal Alloimmune Thrombocytopenia: A Systematic Literature Review and Meta-analysis of Adverse Pregnancy-Related Outcomes to Support the Development of a Novel Prophylactic Therapeutic," was presented by Andrea V. Margulis of RTI Health Solutions. Specifically, the literature review found that, of 198,062 screened pregnant women, 2.2% (95% confidence interval [CI], 2.0%-2.5%) were HPA-1a negative; 32.3% (28.6%-36.1%) of HPA-1a–negative women were HLA-DRB3*01:01 positive and therefore at even higher risk for alloimmunization. Approximately 10% of HPA-1a–negative women were already alloimmunized to HPA-1a. The meta-analysis is based on 12 observational cohort studies from Europe, Canada, and Egypt published from 1985 through 2018. A link to the poster is available here.