title: Approach for Half-Life Extension of Small Antibody Fragments That Does Not Affect Tissue Uptake.
abstract: The utility of antigen-binding antibody fragments is often limited by their short half-lives. Half-life extension of such fragments is usually accomplished by attachment or binding to high-molecular-weight carriers that reduce the renal elimination rate. However, the higher hydrodynamic radius results in greater confinement in the vascular compartment and, thus, lower tissue distribution. We have developed a chemically controlled drug delivery system in which the drug is covalently attached to hydrogel microspheres by a self-cleaving β-eliminative linker; upon subcutaneous injection, the t1/2,βof the released drug acquires the t1/2of linker cleavage. In the present work, we compared the pharmacokinetics of an anti-TNFα scFv, the same scFv attached to 40 kDa PEG by a stable linker, and the scFv attached to hydrogel microspheres by a self-cleaving linker. We also developed a general approach for the selective attachment of β-eliminative linkers to the N-termini of proteins. In rats, the scFv had a t1/2,βof 4 h and a high volume of distribution at steady state (Vd,SS), suggesting extensive tissue distribution. The PEG-scFv conjugate had an increased t1/2,βof about 2 days but showed a reduced Vd,SSthat was similar to the plasma volume. In contrast, the tissue-penetrable scFv released from the hydrogel system had a t1/2,βof about 2 weeks. Thus, the cleavable microsphere-scFv conjugate releases its protein cargo with a prolonged half-life comparable to that of most full-length mAbs and in a form that has the high tissue distribution characteristic of smaller mAb fragments. Other antigen-binding antibody fragments should be amenable to the half-life extension approach described here.
authors.affiliation: ProLynx , 455 Mission Bay Blvd. South, Suite 145, San Francisco, California 94158, United States.
authors.forename: Eric L
authors.initials: EL
authors.lastname: Schneider
authors.affiliation: ProLynx , 455 Mission Bay Blvd. South, Suite 145, San Francisco, California 94158, United States.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Hearn
authors.affiliation: ProLynx , 455 Mission Bay Blvd. South, Suite 145, San Francisco, California 94158, United States.
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Pfaff
authors.affiliation: ProLynx , 455 Mission Bay Blvd. South, Suite 145, San Francisco, California 94158, United States.
authors.forename: Shaun D
authors.initials: SD
authors.lastname: Fontaine
authors.affiliation: ProLynx , 455 Mission Bay Blvd. South, Suite 145, San Francisco, California 94158, United States.
authors.forename: Ralph
authors.initials: R
authors.lastname: Reid
authors.affiliation: ProLynx , 455 Mission Bay Blvd. South, Suite 145, San Francisco, California 94158, United States.
authors.forename: Gary W
authors.initials: GW
authors.lastname: Ashley
authors.affiliation: Delenex Therapeutics AG , Wagistrasse 27, CH-8952 Schlieren, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Grabulovski
authors.affiliation: Delenex Therapeutics AG , Wagistrasse 27, CH-8952 Schlieren, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Strassberger
authors.affiliation: Delenex Therapeutics AG , Wagistrasse 27, CH-8952 Schlieren, Germany.
authors.forename: Lorenz
authors.initials: L
authors.lastname: Vogt
authors.affiliation: Delenex Therapeutics AG , Wagistrasse 27, CH-8952 Schlieren, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Jung
authors.affiliation: ProLynx , 455 Mission Bay Blvd. South, Suite 145, San Francisco, California 94158, United States.
authors.forename: Daniel V
authors.initials: DV
authors.lastname: Santi