The preclinical study of 177Lu-DOTA-LTVSPWY as a potential therapeutic agent against HER2 overexpressed cancer.

BACKGROUND: Peptide receptor radionuclide therapy (PRRT) has evolved in cancer therapy and diagnosis. LTVSPWY, as a peptide, can target HER2 receptor; on the other hand, 177Lu emits ß- which is helpful for cancer therapy. The radiolabeling of LTVSPWY with 177Lu results in a therapeutic agent (177Lu-DOTA-LTVSPWY) capable of cancer treatment. METHODS: 177Lu-DOTA-LTVSPWY was prepared with high radiochemical purity (RCP). The stability was investigated in saline and human serum. The radiotracer affinity toward the SKOV-3 cell line with overexpression of the HER2 receptor was evaluated. Then the impact of the radiotracer on the colony formation of the SKOV-3 cell line was investigated with colony assay. Moreover, the biodistribution of this radiotracer in SKOV-3 xenograft tumor-bearing nude mice were also studied to determine the radiotracer accumulation in the tumor site. The mice were treated with 177Lu-DOTA-LTVSPWY and subjected to histopathological evaluation. RESULTS: The RCP of 177Lu-DOTA-LTVSPWY after radiolabeling and stability tests was more than 97.7%. The radiotracer displayed high affinity toward the SKOV-3 cell line (KD = 6.6 ± 3.2 nM). Treatment of the SKOV-3 cell line with the radiotracer reduces the SKOV-3 colony survival to less than 3% for 5 MBq of the radiotracer. Tumor-to-muscle (T/M) ratio is the highest at 48 h and 1 h post-injection (2.3 and 4.75, respectively). The histopathological study also confirms the cellular damage to the tumor tissue. CONCLUSIONS: 177Lu-DOTA-LTVSPWY can recognize HER2 receptors in vivo and in vitro; hence, it can serve as a therapeutic agent.

Molecular Imaging of HER2 Expression in Breast Cancer patients Using the [99mTc] Tc-Labeled Small Peptide.

PURPOSE: The accurate determination of human epidermal growth factor receptor 2 (HER2) status can predict response to treatment with HER2-targeted therapy for HER2-positive breast cancer patients. [99mTc]Tc-HYNIC-(Ser)3-LTVPWY ([99mTc]Tc-HYNIC-LY) is a small synthetic peptide molecule targeting of the HER2 receptor. This clinical study evaluated the pharmacokinetic, dosimetry, and efficacy of [99mTc]Tc-HYNIC-LY for determining the HER2 status in primary breast cancer patients. MATERIALS AND METHODS: In total, 24 women with suspected primary breast cancer received an intravenous injection of approximately 20 µg (∼740 MBq) of [99mTc]Tc-HYNIC-LY. In the first 3 patients, blood levels of radioactivity were analyzed for pharmacokinetic evaluation and planar gamma camera imaging was conducted at 30 min and 1, 2, 4, and 24 hour after injection for dosimetry assessment. In the last 21 patients, planar imaging was performed at the baseline, as well as 1, 2, 3, and 4 hour, followed by single-photon emission computed tomography (SPECT) imaging after 4 hour to evaluate the tumor-targeting potential in primary lesions. RESULTS: Injection of [99mTc]Tc-HYNIC-LY was safe and well tolerated. Fast blood clearance provided high-contrast HER2 imaging within 1 to 4 hour. The highest absorbed radiation dose was found for kidneys (6.78E-03 ± 2.62E-04 mSv/MBq), followed by the heart (3.73E-03 ± 1.98E-04 mSv/MBq). The [99mTc]Tc-HYNIC-LY peptide was able to detect HER2 status in primary tumors at an acceptable level. CONCLUSION: The findings of this study indicated that [99mTc]Tc-HYNIC-LY SPECT is safe and feasible for the identification of HER2-positive lesions in primary breast cancer patients, and may provide an accurate and non-invasive modality for guiding HER2 targeted therapy.

Preclinical pharmacokinetic, biodistribution, radiation dosimetry, and toxicity studies of 99mTc-HYNIC-(Ser)3-LTVPWY: A novel HER2-targeted peptide radiotracer.

Accurate assessment of the HER2 expression is an essential issue for predicting response to anti-HER2 therapy in breast cancer patients. The aim of this study was to evaluate 99mTc-HYNIC-(Ser)3-LTVPWY (99mTc-HYNIC-LY) peptide as a novel HER2-targeted radiolabeled peptide in healthy mice to examine the applicability of this imaging agent in a first-in-human clinical trial. To this end, pharmacokinetic and dosimetry studies were performed according to the ICH guideline M3 (R2) with 99mTc-HYNIC-LY. To estimate the radiation-absorbed doses in humans, the accumulated activity in each mouse organ was calculated based on biodistribution data. In addition, toxicology assessment was performed based on mortality events, body weights, and serum biochemical, hematological, and histopathological assays. The pharmacokinetic study showed rapid blood clearance. Based on the results of biodistribution study, the highest radioactivity was observed in the kidneys. The projected absorbed doses to the kidneys, liver, lungs, stomach, and spleen were obtained as 1.70E-02, 1.42E-02, 1.02E-02, 8.62E-03, and 8.34E-03 mSv/MBq, respectively. The results also revealed that serum biochemical and hematological parameters were in the normal range. No significant morphologic alterations were observed in the liver, kidneys, and spleen tissues. Consequently, the results were indicative of the suitability of 99mTc-HYNIC-LY peptide for advancement to a first-in-human clinical trial.