Abstract P3-14-23: Affitoxin — A Potent Therapeutic Agent for Treatment of HER2- Overexpressing Tumors
| Autor: | Rafal Zielinski, Monika Kuban, Ilya G. Lyakhov, Jacek Capala, Moinuddin Hassan, K Shafer-Weaver |
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| Rok vydání: | 2010 |
| Předmět: | |
| Zdroj: | Cancer Research. 70:P3-14 |
| ISSN: | 1538-7445 0008-5472 |
| DOI: | 10.1158/0008-5472.sabcs10-p3-14-23 |
| Popis: | Introduction: Cancers overexpressing HER2 gene are usually described as more aggressive and are associated with poor prognosis. Although introduction of trastuzumab, a HER2-specific humanized antibody, significantly improved the outcome, there are still number of patients who do not respond or acquire resistance to HER2-targeted therapy. We have previously described the construction, expression, and in vitro characterization of Affitoxin, a recombinant protein combining HER2- specific Affibody and modified Pseudomonas exotoxin A (PE 38) that blocks protein synthesis by ADP ribosylation of eEF-2 (Zielinski et al. 2009). In this report we present in vivo data. Materials and Methods. Recombinant Affitoxins were expressed and purified from the soluble fraction of E.coli. HER2 specificity was confirmed in vitro by measurement of the residual ATP level in N87 cells treated with Affitoxin and “Non-specific” toxin. containing “off-target” instead of HER2 - Affibodies. Acute toxicity and immunogenicity studies were performed in female Balb/c mice. Affitoxin clearance rate was determined by ELISA and residual serum toxicity. Biodistribution in subcutaneous BT474 tumors model was determined by NIR optical imaging. In vivo efficacy of the drug was verified in subcutaneous (BT474, SKOV3) and intraperitoneal (SKOV3-luc-D3) tumor models. Results. In this work we have confirmed that HER2-specific Affitoxin is a potent agent eliminating HER2-overexpressing cells in vitro at low picomolar concentration range, while non-specific toxin-containing offtarget Affitoxin is four orders of magnitude less efficient. Acute toxicity studies showed that Affitoxin is well tolerated by mice with LD50 = 0.572±0.051 mg/kg. Injection of six doses every third day neither lead to significant weigh loss of the animal nor induced severe liver problems. Pharmacokinetic data indicated fast clearance of Affitoxin from the circulation with half-life shorter than 10 min. Using human tumor xenograft models, we have shown that Affitoxin accumulates in HER2- overexpressing BT474 tumors, leading not only to reduction of growth rate but also permanent shrinkage of relatively large ( Immunogenicity studies indicated that Affitoxin is less immunogenic than toxin containing antibody fragments fused to PE38 (HA22). Conclusions. Affitoxin is a novel recombinant protein, using high affinity Affibody molecules to target HER2 receptors. Our in vitro and in vivo data strongly suggest that Affitoxin might be an attractive alternative or complement for existing HER2 targeted therapies Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-14-23. |
| Databáze: | OpenAIRE |
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