Ontak-like human IL-2 fusion toxin

Area of Science:

• Biotechnology
• Oncology
• Immunotherapy

Background:

• Ontak® (diphtheria toxin-based fusion toxin) was approved for CD25+ cutaneous T-cell lymphoma (CTCL) but was discontinued due to production issues.
• Bacterial expression systems for recombinant toxins like Ontak® present purification challenges.

Purpose of the Study:

• To develop and evaluate novel monovalent and bivalent human IL-2 fusion toxins for CD25+ CTCL treatment.
• To assess the in vivo efficacy and potential of yeast-expressed IL-2 fusion toxins as an alternative to Ontak®.

Main Methods:

• Developed monovalent and bivalent human IL-2 fusion toxins using a diphtheria toxin-resistant Pichia Pastoris yeast expression system.
• Characterized in vitro efficacy using human CD25+ HUT102/6TG cells.
• Assessed in vivo efficacy in human CD25+ HUT102/6TG tumor-bearing NSG mouse models, including evaluation of residual tumor cell sensitivity.

Main Results:

• Both monovalent and bivalent IL-2 fusion toxins demonstrated potent in vitro efficacy, with the bivalent form being significantly more potent.
• In vivo studies showed that both toxin isoforms significantly prolonged survival in tumor-bearing mice in a dose-dependent manner.
• Residual tumor cells remained sensitive to continued treatment, indicating sustained therapeutic potential.

Conclusions:

• Yeast-expressed human IL-2 fusion toxins are effective in vivo against CD25+ CTCL models.
• These novel toxins represent a promising alternative to the clinically discontinued Ontak®, addressing previous production limitations.