Improved Inhibition of Tumor Growth by Diabody-Drug Conjugates via Half-Life Extension

Abstract

Despite some clinical success with antibody-drug conjugates (ADCs) in patients with solid tumors and hematological malignancies, improvements in ADC design are still desirable due to the narrow therapeutic window of these compounds. Tumor-targeting antibody fragments have distinct advantages over monoclonal antibodies, including more rapid tumor accumulation and enhanced penetration, but are subject to rapid clearance. Half-life extension technologies such as PEGylation and albumin-binding domains (ABDs) have been widely used to improve the pharmacokinetics of many different types of biologics. PEGylation improves pharmacokinetics by increasing hydrodynamic size to reduce renal clearance, whereas ABDs extend half-life via FcRn-mediated recycling. In this study, we used an anti-oncofetal antigen 5T4 diabody conjugated with a highly potent cytotoxic pyrrolobenzodiazepine (PBD) warhead to assess and compare the effects of PEGylation and albumin binding on the in vivo efficacy of antibody fragment drug conjugates. Conjugation of 2× PEG20K to a diabody improved half-life from 40 min to 33 h, and an ABD-diabody fusion protein exhibited a half-life of 45 h in mice. In a xenograft model of breast cancer MDA-MB-436, the ABD-diabody-PBD showed greater tumor growth suppression and better tolerability than either PEG-diabody-PBD or diabody-PBD. These results suggest that the mechanism of half-life extension is an important consideration for designing cytotoxic antitumor agents.

A Ligand‐Directed Nitrophenol Carbonate for Transient in situ Bioconjugation and Drug Delivery

“…Bioconjugates are an alluring therapeutic modality that, relative to small molecules, suffer drawbacks in production including high cost, poor batch reproducibility, and poor shelf life; all of which hinder the development of bioconjugates as drugs [1] . Despite these challenges, antibody drug conjugates such as brentuximab vedotin and trastuzmab emtansine which have found clinical success and FDA approval (2011 and 2013 respectively) exemplify the benefits of bioconjugates including tissue specificity, [2] synergistic effects of the biomolecule and drug, [3,4] and increased biological half‐life [5] . These examples and benefits have pushed researchers to explore further methodologies in bioconjugate drug delivery.…”

Rapid Evaluation of Antibody Fragment Endocytosis for Antibody Fragment–Drug Conjugates

“…FDCs were developed as the next generation of ADCs to overcome antibody uptake in vivo [9,23,24,38]. Paradoxically, the recent development of FDCs has focused on improving PK via the re-attachment of a larger molecule (e.g., PEG or HSA), which diminishes the advantage of rapid tumor accumulation and the enhanced penetration of FDCs [11,39,40]. Thus, the identification and evaluation of antibodies possessing optimal rates and high levels of internalization are essential in the development of therapeutic ADCs and FDCs.…”

“…FDCs are modified to improve the pharmacokinetics (PK) profile because the standard route of administration is by intravenous injection. On the contrary, the extension of the half-life of FDCs by PEGylation [ 11 ] or fusion with other proteins, such as human serum albumin [ 12 ], leads to an increase in molecular size, which, in turn, reduces drug penetration into tumors. Thus, the efficient internalization of FDC for anti-tumor efficacy is as crucial as it is for ADCs, as demonstrated by the anti-Her2 scFv–HSA–DM1 conjugate [ 12 ].…”

First clinical study of a pegylated diabody 124I-labeled PEG-AVP0458 in patients with tumor-associated glycoprotein 72 positive cancers

“…One approach to improve the bioavailability of multimeric antibody fragments is through pegylation of surface lysine residues to increase the apparent molecular size of diabodies and avoid first-pass renal clearance, thus extending the half-life in circulation and theoretically increasing tumor uptake 21 - 23 . The AVP04 diabody used in this study is derived from the murine monoclonal antibody CC49, which has been evaluated in clinical trials targeting the tumor associated glycoprotein 72 antigen (TAG-72) 24 - 28 .…”