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Van Duijnhoven S.M.J.,HIGH-TECH | Rossin R.,HIGH-TECH | Rossin R.,Philips | Van Den Bosch S.M.,Philips | And 3 more authors.
Journal of Nuclear Medicine | Year: 2015

Radioimmunotherapy and nuclear imaging (immuno-PET/SPECT) of cancer with radiometal-labeled antibody fragments or peptides is hampered by low tumor-to-kidney ratios because of high renal radiometal retention. Therefore, we developed and evaluated a pretargeting strategy using click chemistry in vivo to reduce kidney uptake and avoid unwanted radiation toxicity. We focused on the bioorthogonal reaction between a trans-cyclooctene (TCO)-functionalized TAG72 targeting diabody, AVP04-07, and a low-molecular-weight radiolabeled tetrazine probe that was previously shown to have low kidney retention and relatively fast renal clearance. Methods: AVP04-07 diabodies were functionalized with TCO tags, and in vitro immunoreactivity toward bovine submaxillary mucin and tetrazine reactivity were assessed. Next, pretargeting biodistribution studies were performed in LS174T tumor-bearing mice with AVP04-07-TCO(n) (where n indicates the number of TCO groups per diabody) and radiolabeled tetrazine to optimize the TCO modification grade (0, 1.8, or 4.7 TCO groups per diabody) and the 177Lu-tetrazine dose (0.1, 1.0, or 10 Eq with respect to the diabody). Radiolabeled tetrazine was injected at 47 h after diabody injection, and mice were euthanized 3 h later. A pretargeting SPECT/CT study with 111Intetrazine was performed with the optimized conditions. Results: Immunoreactivity for native AVP04-07 was similar to that for TCO-functionalized AVP04-07, and the latter reacted efficiently with radiolabeled tetrazine in vitro. The combination of the pretargeting component AVP04-07 functionalized with 4.7 TCO groups and 1 Eq of 177Lu-tetrazine with respect to the diabody showed the most promising biodistribution. Specifically, high 177Lu-tetrazine tumor uptake (6.9 percentage injected dose/g) was observed with low renal retention, yielding a tumor-to-kidney ratio of 5.7. SPECT/CT imaging confirmed the predominant accumulation of radiolabeled tetrazine in the tumor and low nontumor retention. Conclusion: Pretargeting provides an alternative radioimmunotherapy and nuclear imaging strategy by overcoming the high renal retention of lowmolecular- weight radiometal tumor-homing agents through the separate administration of a tumor-homing agent and a radioactive probe with fast clearance. COPYRIGHT © 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

AVIPEP Pty Ltd | Date: 2010-12-23

The present invention provides an isolated protein comprising an immunoglobulin variable region comprising at least two cysteine residues positioned within framework region (FR) 2 and/or at least two cysteine residues positioned within framework region (FR3), wherein if at least two of the cysteine residues in FR2 and/or FR3 are not conjugated to a compound then an intra-framework disulphide bond is capable of forming between the cysteine residues. Preferably the protein comprises an immunoglobulin heavy chain variable region (V

Li L.,Beckman Research Institute | Turatti F.,Avipep Pty Ltd | Crow D.,Beckman Research Institute | Bading J.R.,Beckman Research Institute | And 11 more authors.
Journal of Nuclear Medicine | Year: 2010

Diabodies are noncovalent dimers of single-chain antibody fragments that retain the avidity of intact IgG but have more favorable blood clearance than intact IgG. Radiometals offer a wide range of half-lives and emissions for matching imaging and therapy requirements and provide facile labeling of chelate-antibody conjugates. However, because of their high retention and metabolism in the kidney, the use of radiometal-labeled diabodies can be problematic for both imaging and therapy. Methods: Having previously shown that111In-DOTA-polyethylene glycol (PEG)3400-anti-carcinoembryonic antigen diabody has less than half the kidney uptake and retention of non-PEGylated diabody and that the two have similarly high tumor uptake and retention, we synthesized a similar derivative for an antitumor-associated glycoprotein 72 diabody. We also reduced the molecular size of the polydispersed PEG3400 to monodispersed PEG27 and PEG12 (nominal masses of 1,321 and 617, respectively). We performed biodistributions of their DOTA conjugates radiolabeled with125I,111In, or64Cu in tumor-bearing athymic mice. Results: The addition of PEG3400 to the diabody reduced kidney uptake to a level (≈10 percentage injected dose/g) comparable to that obtained with radiometal-labeled intact IgG. The PEG27 and PEG12 diabody conjugates also demonstrated low kidney uptake without reduction of tumor uptake or tumor-to-blood ratios. When radiolabeled with64Cu, the DOTA-PEG12 and-PEG27 diabody conjugates gave highcontrast PET images of colon cancer xenografts in athymic mice. Conclusion: PEGylated diabodies may be a valuable platform for delivery of radionuclides and other agents to tumors. COPYRIGHT © 2010 by the Society of Nuclear Medicine, Inc.

Bremner J.B.,University of Wollongong | Wu Z.,University of Wollongong | Wu Z.,Avipep Pty Ltd
Australian Journal of Chemistry | Year: 2014

Concise synthetic routes to 2H-benzo[b]thieno[3,2-b][1,5]oxazocin-6(3H)- one, and the new benzo[b]thieno[3,2-b][1,5]oxazonin-7(2H)-one and 2H-benzo[b]thieno[3,2-b][1,5]oxazecin-8(3H)-one systems, have been developed based on intramolecular nucleophilic displacement in the key ring forming step. © 2014 CSIRO.

Powers G.A.,Avipep Pty Ltd | Hudson P.J.,Avipep Pty Ltd | Wheatcroft M.P.,Avipep Pty Ltd
Methods in Molecular Biology | Year: 2012

Multimeric antibody fragments, particularly dimers (diabodies), trimers (triabodies), and tetramers (tetrabodies) of single-chain Fv molecules (scFv), provide high avidity through multivalent binding to the target antigen. The combination of their smaller size and avid binding can provide desirable biological characteristics for tumor targeting applications in vivo; for example, diabodies can have greater tumor penetration and faster blood clearance rates compared to intact full-size antibodies (IgGs). The pharmacokinetic and biodistribution characteristics can further be optimized by the addition of specific thiolation sites for conjugation of PEG molecules to regulate molecular weight and reduce kidney uptake. Thiolation sites can also be used for precise loading of therapeutic payloads. This protocol describes our method for construction and bacterial production of soluble multimeric antibody scFv fragments, focusing on diabodies (scFv dimers). © 2012 Springer Science+Business Media, LLC.

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