First clinical study of a pegylated diabody 124I-labeled PEG-AVP0458 in patients with tumor-associated glycoprotein 72 positive cancers

Abstract

Through protein engineering and a novel pegylation strategy, a diabody specific to tumor-associated glycoprotein 72 (TAG-72) (PEG-AVP0458) has been created to optimize pharmacokinetics and bioavailability to tumor. We report the preclinical and clinical translation of PEG-AVP0458 to a first-in-human clinical trial of a diabody. Methods: Clinical translation followed characterization of PEG-AVP0458 drug product and preclinical biodistribution and imaging assessments of Iodine-124 trace labeled PEG-AVP0458 (¹²⁴I-PEG-AVP0458). The primary study objective of the first-in-human study was the safety of a single protein dose of 1.0 or 10 mg/m^{2 124}I-PEG-AVP0458 in patients with TAG-72 positive relapsed/ metastatic prostate or ovarian cancer. Secondary study objectives were evaluation of the biodistribution, tumor uptake, pharmacokinetics and immunogenicity. Patients were infused with a single-dose of ¹²⁴I labeled PEG-AVP0458 (3-5 mCi (111-185 MBq) for positron emission tomography (PET) imaging, performed sequentially over a one-week period. Safety, pharmacokinetics, biodistribution, and immunogenicity were assessed up to 28 days after infusion. Results: PEG-AVP0458 was radiolabeled with ¹²⁴I and shown to retain high TAG-72 affinity and excellent targeting of TAG-72 positive xenografts by biodistribution analysis and PET imaging. In the first-in-human trial, no adverse events or toxicity attributable to ¹²⁴I-PEG-AVP0458 were observed. Imaging was evaluable in 5 patients, with rapid and highly specific targeting of tumor and minimal normal organ uptake, leading to high tumor:blood ratios. Serum concentration values of ¹²⁴I-PEG-AVP0458 showed consistent values between patients, and there was no significant difference in T½α and T½β between dose levels with mean (± SD) results of T½α = 5.10 ± 4.58 hours, T½β = 46.19 ± 13.06 hours. Conclusions: These data demonstrates the safety and feasibility of using pegylated diabodies for selective tumor imaging and potential delivery of therapeutic payloads in cancer patients.

Keywords: PET imaging; TAG-72; biodistribution; first-in-human; pegylated diabody.

Figure 1

Schema of PEG-AVP0458, and preclinical ¹²⁴I- PEG-AVP0458 data. (A) diagrammatic representation of PEG-AVP0458, showing heavy chain (purple) with CDR residues (red), light chain (aqua) and CDR residues (dark blue), linking residues (light green), PEG (grey and red chains). (B) The biodistribution of ¹²⁴I-PEG-AVP0458, anti-TAG72 diabody over 6 days in LS174T xenografts and serum from BALB/c nude mice. Values are mean percent injected dose per gram (%ID/g) from groups of five mice; bars, SD. (C) Biodistribution Study. Representative images on Day 0 (4 hrs p.i.) Day 1, 3 and 6 of ¹²⁴I- PEG-AVP0458 biodistribution in BALB/c nude mice bearing LS174T colon carcinoma xenografts in the left flank (right side of each image). Image set from each day comprise coronal whole body PET (left panel) and surface-rendered CT (right panel). High specific tumor uptake of ¹²⁴I-PEG-AVP0458 is evident from Day 1 with normal tissue localisation corresponding to non-specific blood pool activity on Day 0 and anticipated thyroid uptake of ¹²⁴I evident.

Figure 2

Overview of first-in-human study. (A) Clinical study events pre- and post- ¹²⁴I-PEG-AVP0458 infusion denoting timing of acquisition of PET-CT images and collection of blood specimens. (B) Patient clinical demographics, and tumor lesion uptake and score. * Dose extravasated, not assessable (N/A); **Biopsy of liver lesion was TAG-72 -ve; true negative result.

Figure 3

Whole body biodistribution of ¹²⁴I-PEG-AVP0458 in Patient 3 (1 mg/m² dose level). Sequential whole-body PET images acquired over one week following a single ¹²⁴I-PEG-AVP0458 infusion showing gradual blood-pool clearance and no specific normal tissue uptake. Localisation of the diabody to sites of metastatic prostate cancer are evident from day 1 and an incidental TAG-72 positive colon tumor was also identified (arrow). Late visualization of the thyroid is likely to reflect free ¹²⁴I due to late de-iodination of the agent.

Figure 4

Whole Body Biodistribution of ¹²⁴I-PEG-AVP0458 (10mg/m² dose level). (A) Anterior Whole Body PET image on Day 5 in Patient 4. Transaxial images in (B) liver (Upper panel - CT, Middle panel - PET, Lower panel -merged PET/CT) showing excellent uptake of ¹²⁴I-PEG-AVP0458 in extensive liver metastases of prostate cancer. Whole body images include reference standard by right foot in field of view.

Figure 5

Whole body clearance of ¹²⁴I-PEG-AVP0458 in all patients. Whole body clearance was calculated from acquired PET image data from Day 0, Day 1, Day 2 or 3, Day 4 or 5, and Day 6 or 7 post-¹²⁴I-PEG-AVP0458 infusion imaging time points.