Effect of Size on Solid Tumor Disposition of Protein Therapeutics

Abstract

In this study, we evaluated the effect of size on tumor disposition of protein therapeutics, including the plasma and tumor pharmacokinetics (PK) of trastuzumab (∼150 kDa), FcRn-nonbinding trastuzumab (∼150 kDa), F(ab) 2 fragment of trastuzumab (∼100 kDa), Fab fragment of trastuzumab (∼50 kDa), and trastuzumab scFv (∼27 kDa) in both antigen (i.e., HER2)-overexpressing (N87) and antigennonexpressing (MDA-MB-468) tumor-bearing mice. The observed data were used to develop the maximum tumor uptake versus molecular weight and tumor-to-plasma area under the curve (AUC) ratio versus molecular weight relationships. Comparison of the PK of different sizes of FcRn nonbinding molecules in target-expressing tumor showed that ∼100 kDa is an optimal size to achieve maximum tumor uptake and ∼50 kDa is an optimal size to achieve maximum tumor-to-plasma exposure ratio of protein therapeutics. The PK data were also used to validate a systems PK model for tumor disposition of different-sized protein therapeutics. The PK model was able to predict a priori the PK of all five molecules in both tumor types reasonably well (within 2-to 3-fold). In addition, the model captured the bell-shaped relationships observed between maximum tumor uptake and molecular weight and between tumor-to-plasma AUC ratio and molecular weight. Our results provide an unprecedented insight into the effect of size and target engagement on the tumor PK of protein therapeutics. Our results also provide further validation of the tumor disposition model, which can be used to support discovery, development, and preclinical-to-clinical translation of different sizes of protein therapeutics. SIGNIFICANCE STATEMENT This article highlights the importance of molecular size and target engagement on the tumor disposition of protein therapeutics. Our results suggest that ∼100 kDa is an optimal size to achieve maximum tumor uptake and ∼50 kDa is an optimal size to achieve maximum tumor-to-plasma exposure ratio for non-FcRn-binding targeted protein therapeutics. We also demonstrate that a systems pharmacokinetics model developed to characterize tumor disposition of protein therapeutics can predict a priori the disposition of different-sized protein therapeutics in target-expressing and targetnonexpressing solid tumors.

Targeting cancer with antibody-drug conjugates: Promises and challenges

“…Classical ADCs include a full-length antibody molecule, which may present challenges for the uptake and permeability of some solid tumors. 116 To generate ADCs with improved uptake and penetration, several strategies in novel ADC design have pivoted toward the use of smaller formats of the antibody, including Fab-drug conjugates, scFvdrug conjugates, and diabody-drug conjugates. [117][118][119] However, these smaller formats may be associated with faster clearance compared to the full-length IgG.…”

“…[117][118][119] However, these smaller formats may be associated with faster clearance compared to the full-length IgG. 116 Although the theoretical potential for these smaller formats exists, much work is still needed to prove a clear benefit.…”

Pharmacokinetic and Drug Metabolism Properties of Novel Therapeutic Modalities

“…Looked at from a wholistic viewpoint, integrating the results of in vitro and in vivo biodistribution experiments will lead to a stronger translational understanding of new modalities but will also require advancements in many of our current modeling approaches. The article by Li et al (2019) defines a mathematical model for understanding PK-PD in a mouse tumor model with different antibody fragments. As such, it serves as a good example of a parameterized model that can help identify the required amount of drug needed at the site of action to achieve efficacy.…”

Impact of charge patches on tumor disposition and biodistribution of therapeutic antibodies

“…The site of action for most antibody therapeutics of solid tumors is the cellular surface, accessed from the interstitial space [7]. Several barriers need to be crossed to reach this compartment and distribute homogeneously (Figure 1a, [8,11]).…”

“…Also, diffusion-limited uptake routes, i.e. paracellular transcapillary transport in the leaky tumor vasculature [8,27] and surface transport [11], could be hampered by charge-dependent transient binding events. Transcellular extravasation has also been shown to be modulated by charge, through promotion of charge-mediated adsorptive transcytosis [28].…”