RLYB Ends Pregnancy-Related Rare Disease Program, Stock Tanks

Shares of Rallybio Corporation RLYB tanked 41.2% on April 8 after the company announced its decision to stop the development of RLYB212 for the prevention of fetal and neonatal alloimmune thrombocytopenia (FNAIT).

The company decided to stop the development of RLYB212 after pharmacokinetic (PK) data from a phase II study showed that treatment with the candidate failed to achieve predicted target concentrations of 6 ng/mL to 10, as well as the minimum target concentration required for efficacy of 3 ng/mL.

The phase II dose confirmation study evaluated the PK and safety of RLYB212 in pregnant women who are at higher risk for HPA-1a alloimmunization and FNAIT.

RLYB212, a novel human monoclonal anti-HPA-1a antibody, was being developed to prevent pregnant individuals from alloimmunizing, which curbs the risk of FNAIT and its potentially devastating consequences in their fetuses and newborns.

RLYB Price Performance

Year to date, shares of Rallybio have plunged 74% compared with the industry’s decline of 8.9%.

RLYB's Focus Now on Lead Program RLYB116

Following the setback related to RLYB212, the company is now focused on developing its lead candidate, RLYB116, a differentiated C5 inhibitor, for the treatment of complement-driven diseases.

Rallybio is planning to initiate dosing in a confirmatory pharmacokinetic/pharmacodynamic study on RLYB116 for treating complement-mediated diseases, including paroxysmal nocturnal hemoglobinuria (PNH), generalized myasthenia gravis (gMG) and antiphospholipid syndrome (APS), later in the second quarter of 2025.

The study is likely to show complete and sustained complement inhibition with improved tolerability of RLYB116.

Data from cohorts 1 and 2 of the study are expected in the third and fourth quarters of 2025, respectively.

Per management, complement-mediated diseases like PNH, APS and gMG represent a commercial opportunity of more than $6 billion.

RLYB's Zacks Rank & Other Stocks to Consider

Rallybio currently carries a Zacks Rank #2 (Buy).

Some other top-ranked stocks in the biotech sector are NuCana plc NCNA, Amicus Therapeutics, Inc. FOLD and ANI Pharmaceuticals, Inc. ANIP, each carrying a Zacks Rank #1 (Strong Buy) at present. You can see the complete list of today’s Zacks #1 Rank stocks here.

In the past 60 days, estimates for NuCana’s loss per share have narrowed from $11.26 to 5 cents for 2025. During the same time, loss per share estimates for 2026 have narrowed from $20.41 to 5 cents. Year to date, shares of NCNA have declined 39.1%.

NCNA’s earnings beat estimates in three of the trailing four quarters while missing the same on the remaining occasion, the average surprise being 52.48%.

In the past 60 days, estimates for Amicus’ earnings per share have increased from 43 cents to 52 cents for 2025. During the same time, earnings per share estimates have increased from 71 cents to 80 cents for 2026. Year to date, shares of FOLD have decreased 28.7%.

FOLD’s earnings beat estimates in three of the trailing four quarters while missing the same on the remaining occasion, the average surprise being 45.42%.

In the past 60 days, estimates for ANI Pharmaceuticals’ earnings per share have increased from $5.54 to $6.35 for 2025. During the same time, earnings per share estimates for 2026 have increased from $6.75 to $7.21. Year to date, shares of ANIP have rallied 14.1%.

ANIP’s earnings beat estimates in each of the trailing four quarters, the average surprise being 17.32%.

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This article originally published on Zacks Investment Research (zacks.com).

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