[ 99m Tc]duramycin for cell death imaging: Impact of kit formulation, purification and species difference

Nucl Med Biol. 2018 Jan;56:1-9. doi: 10.1016/j.nucmedbio.2017.08.005. Epub 2017 Sep 14.

Abstract

Introduction: [99mTc]duramycin is a SPECT tracer for cell death imaging. We evaluated the impact of kit formulation, purification and species difference on the pharmacokinetic profile and cell death targeting properties of [99mTc]duramycin in order to define the optimal conditions for (pre-)clinical use.

Methods: Three kits were prepared (A: traditional formulation, B: containing 1/3 of ingredients, C: containing HYNIC-PEG12-duramycin). Following labeling, the kits were used without purification, or with SPE or HPLC purification. The pharmacokinetic profile was evaluated in mice and rats at 24 h post tracer injection (p.i.). Non-specific accumulation of [99mTc]duramcyin was studied by μSPECT imaging in chemotherapy treated COLO205 tumor bearing mice pre-treated with cold duramycin (0.01-50 μg). Cell death targeting ability of the kits displaying the best pharmacokinetic profile was compared in a treatment response study in COLO205 tumor bearing mice treated with conatumumab (anti-DR5 antibody).

Results: HPLC purification of kit prepared [99mTc]duramycin and reducing the amount of kit ingredients resulted in the best pharmacokinetic profile with low accumulation in liver, spleen and kidneys. The use of PEGylated [99mTc]duramycin required longer circulation times (> 4 h pi) to obtain good imaging characteristics. Pre-treatment with duramycin significantly decreased tracer uptake in chemotherapy treated tumors in a dose-dependent manner. A blocking dose of 50 μg significantly increased non-specific accumulation in liver and spleen. Non-specific accumulation of [99mTc]duramycin was however demonstrated to be species dependent. HPLC purified kit A (5.21±1.71 %ID/cc) and non-purified kit B (1.68±0.46 %ID/cc) demonstrated a significant increase in tumor uptake compared to baseline following conatumumab treatment.

Conclusions: To obtain [99mTc]duramycin with favorable imaging characteristics for cell death imaging in mice [99mTc]duramycin needs to be prepared with high specific activity by applying HPLC purification. The need for HPLC purification appears to be a species dependent phenomenon and might therefore not be required for clinical translation.

Keywords: Cell death; Kit formulation; SPECT; Treatment response; [(99m)Tc]duramycin.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / pharmacology*
  • Antineoplastic Agents, Immunological / pharmacology
  • Bacteriocins / chemistry
  • Bacteriocins / pharmacokinetics*
  • Cell Death*
  • Chemistry, Pharmaceutical*
  • Colorectal Neoplasms / diagnostic imaging
  • Colorectal Neoplasms / drug therapy
  • Colorectal Neoplasms / pathology*
  • Female
  • Mice
  • Mice, Nude
  • Organotechnetium Compounds / chemistry
  • Organotechnetium Compounds / pharmacokinetics*
  • Rats
  • Rats, Sprague-Dawley
  • Species Specificity
  • Tissue Distribution
  • Tomography, Emission-Computed, Single-Photon / methods

Substances

  • Antibodies, Monoclonal
  • Antineoplastic Agents, Immunological
  • Bacteriocins
  • Organotechnetium Compounds
  • technetium 99m HYNIC-duramycin
  • conatumumab