Rallybio Corp (RLYB)

Rallybio Corporation is a clinical-stage biotechnology company, launched in January 2018, whose mission is to develop and commercialize therapies for patients with severe and rare diseases. Its team has experience in rare disease drug development and members were involved in the approval of more than 30 drugs, including Strensiq, Kanuma, Nulibry, Soliris and Ultomiris. The company has built a pipeline in maternal fetal health, complement dysregulation, hematology and metabolic disorders. Its strategy is to advance its lead programs alone or through partnerships, seek partnering or non-dilutive financing for some programs, move preclinical programs forward in a capital-efficient way, and pursue targeted business development.

The two most advanced programs are in clinical development. RLYB212 is a subcutaneous monoclonal anti-HPA-1a antibody for preventing fetal and neonatal alloimmune thrombocytopenia (FNAIT), for which no therapy is approved. It has completed a Phase 1 first-in-human trial and a Phase 1b proof-of-concept trial and is in a single-arm Phase 2 trial in pregnant women at higher risk across Europe, targeting eight participants. The company is also running an FNAIT natural history study that had screened more than 14,300 women as of January 31, 2025, and it expects the data to support a planned single-arm Phase 3 trial. RLYB116 is a subcutaneously administered C5 complement inhibitor, an Affibody molecule attached to an albumin binding domain, with potential in PNH, generalized myasthenia gravis and antiphospholipid syndrome. It has completed a Phase 1 trial in healthy participants, and the company plans to start a confirmatory PK/PD trial in the second quarter of 2025. Preclinical programs include RLYB332, a long-acting version of the Matriptase-2 inhibitor antibody RLYB331 (rights obtained in May 2022) for iron overload diseases such as polycythemia vera, beta thalassemia and some myelodysplastic syndromes. They also include ENPP1 inhibitors (REV101 and REV102) for hypophosphatasia, discovered through a 2019 AI drug discovery joint venture with Exscientia, now part of Recursion. A December 2022 collaboration with AbCellera aims to discover and develop antibody therapeutics for rare diseases, starting with rare metabolic diseases.

The company targets patients with rare diseases, estimated at 25 to 30 million people with as many as 7,000 conditions in the United States alone. For FNAIT, it estimates more than 30,000 pregnancies a year at higher risk in the United States, Canada, the UK, other major European countries and Australia, and a market opportunity for RLYB212 above $1.6 billion. Expectant mothers are not currently screened for FNAIT risk. Mothers identified as at risk after an affected birth may receive weekly IVIG with prednisone, which does not prevent alloimmunization. The company believes risk screening could be done as part of routine prenatal blood work.

The text gives limited operating detail. Rallybio develops its candidates through clinical trials, sites in Europe for the RLYB212 Phase 2 trial, and collaborations with Exscientia/Recursion and AbCellera. It also did manufacturing process enhancements to further purify the RLYB116 drug substance. The text does not identify its headquarters or suppliers.