US-based biotech Rallybio is ending its RLYB212 programme for the prevention of fetal and neonatal alloimmune thrombocytopenia (FNAIT) following disappointing results from a Phase II trial.
FNAIT is a rare, pregnancy-related condition where a mother’s immune system attacks the baby’s platelets, leading to a low platelet count (thrombocytopenia) and potentially life-threatening bleeding complications.
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The biotech’s lead asset RLYB212 failed to show minimum efficacy signals and pharmacokinetic (PK) data or achieve predicted target concentrations in a Phase II trial (NCT06435845). As a result, the RLYB212 programme is being discontinued.
On the news, the company’s Nasdaq-listed stock dipped by 41% from $0.425 at close on 7 April to a close of $0.25 on 8 April. Globally, the stock markets have been dropping over the past week following the announcement of US tariffs from President Donald Trump.
Rallybio CEO Dr Stephen Uden said: “We are disappointed by the PK results of the RLYB212 Phase II trial. 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.”
The single-arm Phase II trial was designed to assess the PK and safety of RLYB212, a subcutaneous, human monoclonal anti-HPA-1a antibody, in pregnant women at higher risk for HPA-1a alloimmunisation and FNAIT. Secondary endpoints included the assessment of pregnancy and neonatal/infant outcomes and the occurrence of emergent HPA-1a alloimmunisation.
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By GlobalDataSecond-trimester PK results from patients demonstrated an inability for RLYB212 to achieve predicted target concentrations of 6ng/mL to 10ng/mL, as well as the minimum target concentration required for efficacy of 3ng/mL. The study also determined that dose adjustment is not feasible. Rallybio hypothesises that HPA-1a antigen expression on the placenta may be impacting plasma concentrations of RLYB212.
No further enrolment in the trial is planned and all screening of participants has been stopped. Safety follow-up of patients will continue, as specified in the clinical trial protocol.
Other pipeline products
Rallybio has one other therapy, RLYB-116, a once-weekly low-volume C5 inhibitor for the treatment of complement-driven diseases including myasthenia gravis (MG), in the clinic that it will now prioritise.
RLYB-116 is in a Phase I trial (ACTRN12621001571864), evaluating the therapy in health volunteers. In September 2023, preliminary data from the trial was announced, showing RLYB-116’s early promise.
If approved, GlobalData predicts sales of RLYB-116 will reach $1.23bn in 2030.
GlobalData is the parent company of Clinical Trials Arena.
The company also has several pre-clinical assets, including REV102 and RLYB332.
Dr Uden continued: “Rallybio remains steadfast in our mission to develop transformative therapies. We are focused on creating shareholder value by advancing our portfolio of potentially best-in-class assets for patients with rare diseases, which includes RLYB116 and REV102, an ENPP1 inhibitor for patients with hypophosphatasia, as well as RLYB332, a long-acting matriptase-2 antibody for diseases of iron overload.”
FNAIT market
There are no approved targeted therapies for FNAIT management. The condition is not routinely screened for during pregnancy and firstborn children with FNAIT are often only diagnosed postnatally.
In March 2024, Johnson & Johnson (J&J) was granted fast track designation by the US Food and Drug Administration (FDA) to investigate nipocalimab, an investigational monoclonal antibody that binds with high affinity block the neonatal Fc receptor (FcRn) and reduces levels of circulating immunoglobulin G (IgG) antibodies, in FNAIT. J&J is conducting two Phase III trials (NCT06449651 and NCT06533098) of the drug in pregnant patients at risk of FNAIT.
Nipocalimab was granted orphan drug designation by the FDA for FNAIT in December 2023. It is also being investigated in MG, erythroblastosis foetalis and acquired (autoimmune) haemolytic anaemia. If approved, GlobalData predicts a sales forecast for nipocalimab of $2.1bn in 2030.
