On its long slog toward FDA approval, teplizumab, a monoclonal antibody being developed for delaying or preventing type 1 diabetes, has stumbled over bioequivalency concerns.

Teplizumab’s healthy volunteer bridging study didn’t prove pharmacokinetic (PK) equivalence with the original Eli Lily-manufactured product used in pivotal trials, according to FDA’s Complete Response Letter (CRL), portions of which manufacturer Provention Bio has shared.

Originally a child of Eli Lily, teplizumab was abandoned after it failed to meet efficacy endpoints in a late-stage clinical trial in 2010. Provention acquired it from co-developer Macrogenics in 2018.

To move forward, the CRL noted, Provention “will need to establish [pharmacokinetic] comparability appropriately between the intended commercial product and the clinical trial product or provide other data that adequately justify why PK comparability is not necessary.”