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March 31, 2023

Rallybio drug performs in clinical trial as treatment for newborn immune disorder

Photo | Contributed Rallybio co-founder and CEO Martin Mackay (left) and Dr. Steve Uden, co-Founder and COO.

New Haven’s Rallybio has announced that its drug candidate RLYB212 showed strong results in a proof-of-concept study as a treatment for a rare immune disorder in fetuses and newborns.

The company reported earlier this month that clinical proof-of-concept has been achieved in a Phase 1b study for the drug candidate, an anti-HPA-1a monoclonal antibody used in the prevention of fetal and neonatal alloimmune thrombocytopenia (FNAIT). 

After a single dose in healthy patients, RLYB212 was able to rapidly and completely eliminate transfused, HPA-1a positive platelets in HPA-1a negative subjects. HPA-1a positive platelets can trigger an immune response in fetuses and newborns and cause FNAIT, which can be life-threatening.

Róisín Armstrong, Rallybio’s RLYB212 program lead, said, “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 it had launched a multi-dose Phase 1 trial in Europe in the first quarter of this year to evaluate the safety and effectiveness of RLYB212. Results are expected later this year. 

The company said it would focus its efforts going forward on RLYB212, halting development of candidate RLYB211, a plasma-derived polyclonal anti-HPA-1a antibody.

Rallybio went public in July 2021, and planned to raise an additional $50 million through an offering of 5 million shares at $6 per share in November.

In December, Rallybio announced a partnership with Canada-based AbCellera to create an “antibody discovery engine” to help develop new drugs.

Contact Liese Klein at

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