Polyclonal Human Anti-MERS Coronavirus Antibody: Possible Future Role in Therapy

Administration of antibodies has been an effective approach to treat and prevent selected infections including Middle East Respiratory Syndrome coronavirus (MERS Co-V), but quantities of antibodies from human volunteers are limited. An alternative approach is use of hyperimmune plasma of transchromosomic cattle. After immunization with MERS Co-V S protein nanoparticles, cattle produce potent, antigen-specific, human polyclonal immunoglobulin G (IgG) in large quantities.

Investigators now report results of a first-in-human, phase 1, placebo-controlled trial of anti-MERS Co-V polyclonal IgG antibody, designated SAB-301. Researchers randomized 38 healthy adults to receive placebo or 1 of 6 SAB-301 infusion doses ranging from 1 mg/kg to 50 mg/kg. Participants were followed for 90 days postinfusion.

Pharmacokinetic studies confirmed that the terminal elimination half-life was approximately 28 days (except in 1 mg/kg recipients), similar to clearance of other antibodies in humans. No participant developed new antidrug antibodies postinfusion. Antibody titers on days 21 and 42 suggested viral neutralization activity exceeding usual duration of MERS Co-V infections. The only serious adverse event was a suicide attempt by a participant with an unacknowledged history of depression who received the highest dose. Most adverse events occurred in similar proportions in placebo and antibody groups, except low serum bicarbonate in three antibody recipients versus in no placebo recipients.