The company is dropping its former lead molecule in favor of another antibody, RLYB116, which is being developed for a variety of rare autoimmune disorders.
Rallybio is discontinuing the development of its former lead molecule in a rare autoimmune bleeding disorder. The biotech’s decision, announced Tuesday, comes after a disappointing pharmacokinetic readout from a Phase II trial.
RLYB212 is a human monoclonal antibody the company was developing to treat fetal and neonatal alloimmune thrombocytopenia (FNAIT), a rare bleeding disorder in which a mother’s immune system attacks a fetus or newborn’s platelets.
Rallybio’s data showed that the antibody was not reaching predicted target concentrations (6–10 ng/mL) or the minimum target concentration required for efficacy (3 ng/mL).
“Given that the results significantly deviated from the predicted range and the absence of empiric data to further inform dose adjustment, the risk/benefit no longer supports continued dosing, and we will discontinue RLYB212 development,” CEO Stephen Uden said in the statement.
The Connecticut-based company will continue development on another molecule, RLYB116, an antibody fusion protein that inhibits a protein in the complement pathway, a part of the body’s innate immune system. Rallybio is pushing RLYB116, currently in Phase I trials, for diseases resulting in rare disorders of the complement pathway, including paroxysmal nocturnal hemoglobinuria (PNH), antiphospholipid syndrome (APS) and generalized myasthenia gravis (gMG).
The discontinuation is a fork in the road for Rallybio. The company launched in 2018, backed by multiple funding rounds totaling nearly $250 million, to investigate new treatments for rare and ultrarare conditions. In addition to RLYB212’s discontinuation, molecules like RLYB211, another FNAIT-targeting molecule it had previously touted, no longer appears in the company’s published pipeline.
Other than RLYB116, the company’s pipeline is preclinical and includes a small molecule for hypophosphatasia, a rare and inherited metabolic bone disorder, discovered in a research partnership with Recursion, and an antibody for iron overload and anemias.
