Novel High Affinity VEGF Analogs For Targeted Imaging of Thyroid Cancer

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DESCRIPTION (provided by applicant): Thyroid cancer of follicular origin is the most common malignancy of endocrine tissues, disproportionally affecting women, and is one of the few cancers greatly increasing in incidence & prevalence for unknown reasons not solely attributable to improved diagnosis. Most patients require lifelong diagnostic surveillance with radioiodine imaging to detect residual & recurrent tumor requiring subsequent therapy with 131I. One of the PIs co-invented & co-developed Genzyme's recombinant human TSH (Thyrogen), currently approved for enhancing diagnostic imaging with radioiodine and for stimulation of the thyroid cancer serum marker, thyroglobulin (TG). However there is currently no optimal method to image the greatly increasing number of more aggressive cancers causing major morbidity and mortality, detected by increased serum Tg, but which have lost the ability to concentrate radioiodine because of decreased expression of the Na/I symporter. Nor is there any diagnostic method to predict which tumors may respond to increasingly important anti-angiogenic therapy for these usually highly angiogenic tumors. The two PIs have invented completely novel, patented methods to design and produce much higher affinity and longer acting analogs of VEGF which can be used in novel, targeted imaging of such tumors to the VEGFR2 receptor in both the stromal vascular endothelium and in tumor epithelium, as supported by extensive and compelling preliminary data. Two approaches of targeted imaging will be compared: a direct optimized 99mTcm labeling method of such soluble VEGF analogs and another method using novel pegylated & VEGF analog targeted "stealth" nanoparticles which can selectively transverse the highly fenestrated, leaky tumor vessels of angiogenic tumor vessels but not normal vessels. In Phase 1 of this SBIR fast track the PIs will: (1) Develop higher affinity and longer acting hVEGF analogs by lysine and arginine scanning mutagenesis of selected loops in both poles of the dimeric ligand without and with introduction of a novel neoglycosylation site adding two complex, sialylated carbohydrate chains; assessing binding of each analog to VEGFR2 and bioactivity in the stimulation of human vascular endothelial cell (HUVEC) proliferation; produce and purify 5-10 mg amounts of the final 3 glycosylated and optimally sialylated analogs in CHO cells in roller bottles; (2) Develop novel pegylated polymeric "stealth" nanoparticles targeted by covalently coupled high affinity VEGF ligand and labeled with coupled radionuclides to high specific activity; (3) Assess in vitro binding and internalization of as wellas in vivo pharmacokinetic properties of VEGF analogs directly coupled to 99mTc or 125I compared to VEGF analog-targeted labeled nanoparticles. In Phase 2 the PIs will: (1) Produce and purify large amounts (50-200 mg) of the final 2 selected VEGF analog targeting candidates in a large mammalian cell bioreactor; (2) Greatly extend Phase 1 in vivo and ex vivo imaging results by further optimizing imaging sensitivity and specificity; (3) Perform parallel quantitativ organ uptake studies with labeled VEGF analogs; (4) Make the final selection of the specific analog, radionuclide and direct labeling versus indirect nanoparticle labeling method to bring forward for commercialization based on multiple criteria. These completely novel methods for earlier detection & localization of the increasing numbers of aggressive thyroid cancers should lead to earlier and more personalized therapy predicting which patients will most benefit from increasingly important but potentially toxic anti-angiogenic therapy.