Rallybio: Clinical proof-of-concept achieved in study for RLYB212 to stop FNAIT

Rallybio announced that clinical proof-of-concept has been achieved in a Phase 1b study for RLYB212, an anti-HPA-1a monoclonal antibody for the prevention of fetal and neonatal alloimmune thrombocytopenia, FNAIT. Results show that one week after a single subcutaneous dose, RLYB212 was able to rapidly and completely eliminate transfused, HPA-1a positive platelets in HPA-1a negative subjects. Additional findings from the study show: The reduction in mean platelet elimination half-life was greater than 90% in both RLYB212 dose groups compared to placebo and was dose related. The broad range of pharmacokinetic and pharmacodynamic data allows substantive modeling to inform dose selection for a future registrational study. RLYB212 was observed to be well-tolerated with no serious adverse events reported. The Company expects to report data from the Phase 1b clinical study of RLYB212 at a scientific conference in 2023. "Our FNAIT development program has consistently demonstrated the effectiveness of anti-HPA-1a antibodies to rapidly eliminate HPA-1a positive platelets from the circulation of HPA-1a negative subjects," commented Roisin Armstrong, Ph.D., Rallybio’s RLYB212 Program Lead. "We’ve also established in published nonclinical studies the association between rapid platelet elimination and prevention of HPA-1a alloimmunization, which can lead to negative and potentially life-threatening outcomes in FNAIT. Collectively, these data reinforce our belief on the potential for an anti-HPA-1a antibody to be a viable approach for preventing FNAIT and we look forward to continued advancement of the RLYB212 development program." Rallybio also announced that testing in the multi-dose cohort of its single-center Phase 1 trial in Europe began in the first quarter of 2023. This portion of the Phase 1 study will evaluate safety and pharmacokinetics of RLYB212 based on repeat dosing over 12 weeks in healthy male and female participants. The Company expects results from this cohort of subjects in the fourth quarter of 2023. Martin Mackay, Ph.D., Chief Executive Officer of Rallybio, stated, "We are very pleased with the progress of our RLYB212 program. Throughout the program, we have carefully laid the groundwork to advance a product candidate that we believe can have a significant impact on the lives of expectant mothers and neonates. RLYB212 exemplifies Rallybio’s enduring commitment to transforming the treatment of rare diseases with little to no therapeutic options." Given the favorable development profile of RLYB212 to date, the data generated to date for RLYB212, and the expected manufacturing and supply efficiencies for RLYB212, the Company also announced today that RLYB211, a plasma-derived polyclonal anti-HPA-1a antibody, will not be advanced further in clinical development.