Search

Purpose: The aims of the study were to develop and evaluate a novel residualizing peptide for labeling internalizing antibodies with 124 I to support clinical development using immuno-positron emission tomography (PET). Methods: The anti-epidermal growth factor receptor antibody ch806 was radiolabeled directly or indirectly with isotopes and various residualizing peptides. Azido-derivatized radiolabeled peptides were conjugated to dibenzylcyclooctyne-derivatized ch806 antibody via click chemistry. The radiochemical purities, antigen-expressing U87MG.de2-7 human glioblastoma cell-binding properties, and targeting of xenografts at 72 hours post injection of all radioconjugates were compared. Biodistribution of 124 I-PEG 4 -tptddYddtpt-ch806 and immuno-PET imaging were evaluated in tumor-bearing mice. Results: Biodistribution studies using xenografts at 72 hours post injection showed that 131 I-PEG 4 -tptddYddtpt-ch806 tumor uptake was similar to 111 In-CHX-A″-DTPA-ch806. 125 I-PEG 4 -tptddyddtpt-ch806 showed a lower tumor uptake value but higher than directly labeled 125 I-ch806. 124 I-PEG 4 -tptddYddtpt-ch806 was produced at 23% labeling efficiency, 98% radiochemical purity, 25.9 MBq/mg specific activity, and 64% cell binding in the presence of antigen excess. Tumor uptake for 124 I-PEG 4 -tptddYddtpt-ch806 was similar to 111 In-CHX-A″-DTPA-ch806. High-resolution immuno-PET/magnetic resonance imaging of tumors showed good correlation with biodistribution data. Conclusions: The mixed d / l -enantiomeric peptide, d Thr- d Pro- d Thr- dA sp -dA sp-Tyr -dA sp -dA sp- d Thr- d Pro- d Thr, is suitable for radiolabeling antibodies with radiohalogens such as 124 I for high-resolution immuno-PET imaging of tumors and for evaluation in early-phase clinical trials.

The authors present the case studies of two patients whose malignant tumors were detected with a Tc-99m labeled antifibrin monoclonal antibody (DD-3B6/22), which is specific for cross-linked fibrin. The first case was a malignant fibrous histiocytoma involving the proximal aspect of the left thigh, whereas in the second case, the patient was receiving treatment for a squamous cell carcinoma of the right mainstem bronchus. The results highlight the potential of this anti-D-dimer radiopharmaceutical for noninvasive detection of malignant tumors.

Background: Death receptor 5 (DR5) is a member of the TNFR superfamily that initiates the extrinsic apoptotic pathway by activating caspases. CS-1008 is a humanised, monoclonal IgG1 agonistic antibody to human DR5 created by CDR grafting of the murine antibody TRA-8. The aim of this study was to investigate the impact of CS-1008 dose on biodistribution, quantitative tumor uptake and anti-tumor response in patients with mCRC. Methods: Pts with mCRC who had received at least 1 course of chemotherapy (CT) were treated with weekly IV CS-1008 infusions in 5 non-sequential cohorts (Co). Different loading doses were used on days 1 and 8 (Co 1: 0.2 and 6 mg/kg; Co 2: 1 and 6 mg/kg; Co 3: 2 and 6 mg/kg; Co 4: 4 and 4mg/kg; Co 5: 6 and 2 mg/kg), followed by a weekly CS-1008 dose of 2 mg/kg. Cycle 1 encompassed 7 wks of therapy (D1 and D36 doses trace-labeled with 111In); additional weekly CS-1008 was scheduled as 4-wk cycles. Primary endpoints were to determine (1) the influence of CS-1008 dose on initial biodistribution, pharmacokinetic (PK) and tumor uptake of 111In-CS-1008 following single infusion; (2) changes in biodistribution, PK and tumor uptake following sequential doses. Secondary endpoints were to determine (1) anti-tumor response; (2) changes in tumor metabolism; (3) serum apoptosis biomarkers and serum tumor response markers. Results: Nineteen pts with a median age of 64 years and 2-6 prior CT lines were enrolled as follows: Co 1, 2 pts; Co 2, 4 pts; Co 3, 5 pts; Co 4, 3 pts; and Co 5, 5 pts. Twelve pts showed tumor uptake of 111In-CS-1008, 3 at each of the 1, 2, 4 and 6 mg/kg D1 dose levels. 111In-CS-1008 uptake in tumor was variable: some pts showed no uptake, in others uptake was observed in all measurable lesions. Liver metastases showed poor uptake of CS-1008. No significant differences were observed in tumor uptake between D1 and D36, and no effect of dose on tumor uptake was seen. DR5 expression in archived samples did not correlate with 111In-CS-1008 uptake, nor with clinical outcome. 111In-CS-1008 biodistribution showed gradual blood pool clearance and no discernible abnormal uptake in normal tissue. CS-1008 PK was not affected by dose or repeated drug administration. At restaging, there were 8 SD, 1 PR and 10 PD. The duration of PR was 3.7 months (mos). The mean duration of SD was 4 mos (range, 2.6-6.7 mos). Among the group of pts who showed CS-1008 uptake in tumor, 58% had clinical benefit (SD or PR), compared with 28% of pts in the group with no tumor uptake. The lesions that showed CS-1008 uptake were less likely to progress even in pts with overall PD at restaging. Conclusions: 111In-CS-1008 uptake in tumor predicts SD or PR. Tumor DR5 expression, assessed by 111In-CS-1008 imaging, reveals real-time heterogeneous DR5 expression, both on a per pt and on a lesion by lesion basis, and appears to be a promising predictive imaging biomarker of clinical benefit in pts with mCRC receiving CS-1008. Citation Format: Marika Ciprotti, Niall C. Tebbutt, Fook T. Lee, Sze T. Lee, Dave C. McKee, Graeme J. O'Keefe, Sylvia J. Gong, Geoffrey Chong, Hui K. Gan, Wendie Hopkins, Bridget Chappell, Nancy Y. Guo, Fiona E. Smyth, Archie N. Tse, Mendel Jansen, Manabu Matsumura, Rira Watanabe, Robert A. Beckman, Jon Greenberg, Andrew M. Scott. A phase I imaging and pharmacodynamic trial of CS-1008 in patients (pts) with metastatic colorectal cancer (mCRC). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1174. doi:10.1158/1538-7445.AM2013-1174