Diagnostic efficacy of 68Ga-DOTAGA-Duramycin for detection of doxorubicin induced organ toxicity in Wistar rats

Introduction: Chemotherapeutic drugs are known to cause toxic effects to the non-target tissues. The current criteria to detect the toxicity rely on the clinical onset of symptoms which may start at a later stage when the damage is almost irreversible. Therefore, the development of a non-invasive approach to monitor the tissue damage may profoundly impact the prognosis. Apoptosis and necrosis are the pathologically proven manifestation of drug toxicities. Molecular imaging of apoptosis using duramycin, a cell death marker may become a promising approach. The current study presents the efficacy of ⁶⁸Ga-DOTAGA-Duramycin for assessing anthracycline induced organ toxicity in rats.

Methods: Duramycin was conjugated with DOTAGA and radiolabeled with ⁶⁸Ga in-house. The conjugation and radiochemical chemical purity were characterized by MALDI-TOF and radio-TLC, respectively. The animal model study was performed on a total of 38 female Wistar rats. A weekly dose of 2.5 mg/kg of doxorubicin was administered intravenously for six weeks. The rats were categorized into 6 groups: Control (saline), Group A (single dose), Group B (2 doses), Group C (3 doses), Group D (4 doses), and Group E (6 doses). After the last doxorubicin injection rats were randomly selected from each group at 24 h (n=17) and 10 days (n=21), for ⁶⁸Ga-Duramycin uptake analysis. The rats were sacrificed at 60 min post ⁶⁸Ga-DOTAGA-Duramycin (100 μCi) administration. The %ID/gm of tissue was calculated for the heart, liver, lungs, stomach, blood, and spleen. The H&E staining based histopathological analysis of organs was done by the pathologist blinded to the dose injected into the animals.

Results: Duramycin showed a coupled peak with DOTAGA at 2641 Da. The sterile formulation with radiochemical purity of >99% successfully passed the quality control tests for in-vivo administration. The animal assessed at 24 h post last doxorubicin treatment showed the highest tracer uptake in the liver of group B and spleen, kidney of group D. The rats assessed on the 10^th day showed maximum tracer uptake in liver and spleen of group D and E, respectively. The histopathological examination represented mild inflammation and congestion in the liver and kidney. No significant tissue damage was observed in the stomach, spleen, and lungs. Change in the uptake pattern of radiotracer in the myocardium of rats assessed at day 10 was consistent with histopathological findings. In the myocardium, marked intracellular vacuolization, lymphoblastic infiltration, and apoptosis were observed. The radiotracer showed the highest uptake in the atrium and histopathologically also the maximum tissue damage was observed in the atrium.

Conclusions: The uptake trend of ⁶⁸Ga-Duramycin in rat models demonstrates its use as a diagnostic marker for the assessment of doxorubicin induced organ toxicity. Also, the pattern of radiotracer uptake in the myocardium points to the importance of appropriate imaging time points to target the drug-induced apoptosis.

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