Rallybio Announces Preliminary Multiple Dose Data from the Completed Phase 1 Safety and Pharmacokinetics Study for RLYB212, an Anti-HPA-1a Monoclonal Antibody for the Prevention of Fetal and Neonatal Alloimmune Thrombocytopenia

Rallybio Corporation (Nasdaq: RLYB) today announced preliminary data from the completed multiple dose cohort of the Phase 1 safety and pharmacokinetics (PK) study for RLYB212, an anti-HPA-1a monoclonal antibody for the prevention of fetal and neonatal alloimmune thrombocytopenia.

The Phase 1 multiple dose cohort for RLYB212 was initiated in the first quarter of 2023 to evaluate the safety and PK of subcutaneous (SC) RLYB212 based on repeat dosing over 12 weeks. Eight HPA-1a negative subjects participated in the multiple dose cohort; 6 subjects received RLYB212 every 2 weeks and 2 received placebo every 2 weeks.

The preliminary data demonstrated that multiple dose PK were consistent both within and between subjects. The preliminary data and the Company’s clinical pharmacology modeling predictions support a once monthly dosing regimen for the planned Phase 2 study. Consistent with previously reported data, RLYB212 was observed to be generally well-tolerated with no reports of injection site reactions or serious adverse events.

Rallybio also announced today that the RLYB212 toxicology package to support the planned Phase 2 and Phase 3 studies, including the maternal fetal toxicology program, is complete.

“These data support our belief in the potential use of subcutaneous RLYB212 as a prophylactic therapeutic for the prevention of HPA-1a alloimmunization and FNAIT,” commented Róisín Armstrong, Ph.D., Rallybio’s RLYB212 Program Lead. “We are pleased that the RLYB212 toxicology package is complete, including the maternal fetal toxicology program. The program, which involved a novel animal model, is a key step for Phase 2 and Phase 3 clinical studies in pregnant women. We are now focused on initiating the Phase 2 dose confirmation study in pregnant women at higher risk of FNAIT in the second half of 2024. We thank all of our collaborators and particularly, the Fraunhofer Institute for Translational Medicine and Pharmacology and the German Red Cross, for their support and partnership to complete the Phase 1 study.”

Rallybio expects to submit both the RLYB212 clinical pharmacology model and the Phase 2 dosing approach, including supportive clinical and nonclinical data, to a peer reviewed journal in 2024.

About RLYB212 Phase 1 Safety and PK Study

Rallybio’s Phase 1 study is a single-blind, placebo-controlled study that investigated the safety and PK of SC RLYB212 in HPA-1a negative healthy participants. The study included two cohorts: a previously completed single dose cohort and a multiple dose cohort. In the multiple dose cohort, subjects received SC RLYB212 or placebo every 2 weeks for 12 weeks.