Solna, Sweden, June 13, 2025. Affibody’s licensee Rallybio Corporation (Rallybio) has announced the initiation of dosing in a Phase 1 confirmatory pharmacokinetic/pharmacodynamic (PK/PD) study evaluating RLYB116, an innovative, once-weekly, small volume, subcutaneously injected complement factor 5 (C5) inhibitor, based on the Affibody® platform.

Rallybio further announced that the initial indication focus for RLYB116 will be on two hematologic conditions with significant unmet need: immune platelet transfusion refractoriness (PTR) and refractory antiphospholipid syndrome (APS), which are potentially life-threatening conditions with no approved or effective therapeutic options.

The single-blind multiple ascending dose Phase 1 study of RLYB116 (NCT06797375) is designed to demonstrate complete and sustained complement inhibition with favorable tolerability in healthy volunteers. The study will evaluate a 4-week treatment duration that will include two cohorts of eight participants each, randomized 3 to 1 to receive either RLYB116 or placebo once weekly. Cohort 1 will evaluate dosing of 150 mg and Cohort 2 will evaluate dosing of up to 300 mg. The study includes a 10-week follow-up period after the conclusion of treatment.

About Rallybio's RLYB116

RLYB116 is an innovative, long-acting, subcutaneously injected inhibitor of complement factor 5 (C5), based on the Affibody® platform, in development for the treatment of patients with complement-mediated diseases.

The molecule was initially discovered by Affibody under a collaboration with Swedish Orphan Biovitrum AB (Sobi).

About Affibody® molecules

Affibody® molecules are a novel drug class of small therapeutic proteins with characteristics surpassing monoclonal antibodies (mAbs) and antibody fragments. The Company has created a large library consisting of more than ten billion Affibody® molecules, all with unique binding sites, from which binders to given targets are selected. Affibody® molecules are only 6 kDa in size.

They have demonstrated clinical utilities both as tumor-targeting moieties through their small size and as efficacious disease blocking agents in autoimmune indications by utilizing the inherent properties that allow multi-specific formats.

Disclaimer

This press release contains forward-looking statements. While Affibody consider the projections to be based on reasonable assumptions, these forward-looking statements may be called into question by several hazards and uncertainties, so that actual results may differ materially from those anticipated in such forward-looking statements.

Contacts (Affibody)

David Bejker, CEO, +46 706 454 948
Peter Zerhouni, CFO and CBO, +46 706 420 044

Contacts (Media)

Richard Hayhurst, 59° North Communications, richard.hayhurst@59north.bio, +44 (0) 7711 8215727

Attachments

Affibody’s licensee Rallybio Announces Initiation of Dosing with RLYB116 in Phase 1 Confirmatory PK/PD Study

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