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Proc Natl Acad Sci U S A. 2019 Feb 19;116(8):3100-3105. doi: 10.1073/pnas.1815087116. Epub 2019 Feb 4.

Second-generation IL-2 receptor-targeted diphtheria fusion toxin exhibits antitumor activity and synergy with anti-PD-1 in melanoma.

Author information

1
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21231.
2
Bloomberg∼Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University School of Medicine, Baltimore, MD 21231.
3
Department of Oncology, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD 21231.
4
Department of Psychology, Northeastern University, Boston, MA 02115.
5
Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21231; john.murphy@jhmi.edu dpardol1@jhmi.edu wbishai1@jhmi.edu.
6
Bloomberg∼Kimmel Institute for Cancer Immunotherapy, Johns Hopkins University School of Medicine, Baltimore, MD 21231; john.murphy@jhmi.edu dpardol1@jhmi.edu wbishai1@jhmi.edu.

Abstract

Denileukin diftitox (DAB-IL-2, Ontak) is a diphtheria-toxin-based fusion protein that depletes CD25-positive cells including regulatory T cells and has been approved for the treatment of persistent or recurrent cutaneous T cell lymphoma. However, the clinical use of denileukin diftitox was limited by vascular leak toxicity and production issues related to drug aggregation and purity. We found that a single amino acid substitution (V6A) in a motif associated with vascular leak induction yields a fully active, second-generation biologic, s-DAB-IL-2(V6A), which elicits 50-fold less human umbilical vein endothelial cell monolayer permeation and is 3.7-fold less lethal to mice by LD50 analysis than s-DAB-IL-2. Additionally, to overcome aggregation problems, we developed a production method for the fusion toxin using Corynebacterium diphtheriae that secretes fully folded, biologically active, monomeric s-DAB-IL-2 into the culture medium. Using the poorly immunogenic mouse B16F10 melanoma model, we initiated treatment 7 days after tumor challenge and observed that, while both s-DAB-IL-2(V6A) and s-DAB-IL-2 are inhibitors of tumor growth, the capacity to treat with higher doses of s-DAB-IL-2(V6A) could provide a superior activity window. In a sequential dual-therapy study in tumors that have progressed for 10 days, both s-DAB-IL-2(V6A) and s-DAB-IL-2 given before checkpoint inhibition with anti-programmed cell death-1 (anti-PD-1) antibodies inhibited tumor growth, while either drug given as monotherapy had less effect. s-DAB-IL-2(V6A), a fully monomeric protein with reduced vascular leak, is a second-generation diphtheria-toxin-based fusion protein with promise as a cancer immunotherapeutic both alone and in conjunction with PD-1 blockade.

KEYWORDS:

Tregs; cancer immunotherapy; fusion toxin

PMID:
30718426
PMCID:
PMC6386727
DOI:
10.1073/pnas.1815087116
[Indexed for MEDLINE]
Free PMC Article

Conflict of interest statement

Conflict of interest statement: J.R.M., D.M.P., and W.R.B. hold positions in Sonoval, LLC, which holds rights to develop V6A.

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