In developing its anti-hepatitis B and anti-cytomegalovirus antibodies, Protein Design Labs Inc. has encountered efficacy and side effect issues that reveal the design challenges inherent in antibody development.

PDLI's Protovir anti-CMV antibody has shown limited efficacy in trials - a common problem usually related to the appropriateness of the antibody's target to the chosen disease indication. Meanwhile, the company's OST 577 anti-HBV antibody has exhibited side effects unusual to MAbs, specifically formation of immune complexes resulting in proteinuria and fever. PDLI believes the side effects are related to the nature of the viral disease.