Abstract
There is a clinically unmet need for effective treatments for triple-negative breast cancer (TNBC), as it remains the most aggressive subtype of breast cancer. Herein, we demonstrate a promising strategy using a tumor-targeting alkylphosphocholine (NM600) for targeted radionuclide therapy of TNBC. Methods: NM600 was radiolabeled with 86Y for PET imaging and 177Lu for targeted radionuclide therapy. 86Y-NM600 PET imaging was performed on female BALB/C mice bearing syngeneic 4T07 (nonmetastatic) and 4T1 (metastatic) TNBC tumor grafts (n = 3–5). Quantitative data derived from a PET-image region-of-interest analysis, which was corroborated by ex vivo biodistribution, were used to estimate the dosimetry of 177Lu-NM600 treatments. Weight measurement, complete blood counts, and histopathology analysis were performed to determine 177Lu-NM600 toxicity in naïve BALB/C mice administered 9.25 or 18.5 MBq. Groups of mice bearing 4T07 or 4T1 grafts (n = 5–6) received excipient or 9.25 or 18.5 MBq of 177Lu-NM600 as a single or fractionated schedule, and tumor growth and overall survival were monitored. Results: Excellent tumor targeting and rapid normal-tissue clearance of 86Y-NM600 were noted in both 4T07 and 4T1 murine models. Ex vivo biodistribution corroborated the accuracy of the PET data and validated 86Y-NM600 as a surrogate for 177Lu-NM600. 177Lu-NM600 dosimetry showed absorbed doses of 2.04 ± 0.32 and 1.68 ± 0.06 Gy/MBq to 4T07 and 4T1 tumors, respectively, which were larger than those delivered to liver (1.28 ± 0.09 Gy/MBq) and to bone marrow (0.31 ± 0.05 Gy/MBq). The 177Lu-NM600 injected activities used for treatment were well tolerated and resulted in significant tumor growth inhibition and prolonged overall survival in both tested TNBC models. A complete response was attained in 60% of treated mice bearing 4T07 grafts. Conclusion: Overall, our results suggest that 177Lu-NM600 targeted radionuclide therapy has potential for TNBC and merits further exploration in a clinical setting.
Highlights
Breast cancer accounted for 30% of the almost 880,000 new cancer cases in 2018 in the United States [1]
We investigated the properties of NM600, an alkylphosphocholine analog with a desirable tumor selectivity and pharmacokinetic profile for targeted radionuclide therapy
The stability of 177Lu-NM600 in excipient and complete serum was studied by serial radio-high-performance liquid chromatography (HPLC) out to 192 h after incubation
Summary
Breast cancer accounted for 30% of the almost 880,000 new cancer cases in 2018 in the United States [1]. Lipid rafts, which play important roles in cancer cell proliferation, survival, and metastasis, are markedly overexpressed by malignant cells compared with normal cells, constituting a promising mechanism for cancer-targeted therapies [7,8,9,10,11] Leveraging such a nearly universal, receptor-independent targeting mechanism, we have developed several alkylphosphocholine analogs displaying selective tumor uptake and retention in a wide variety of cancer types, including breast cancer. In therapeutic studies using 177Lu-NM600, 4T07 and 4T1 murine cancers were used to investigate 2 clinically relevant TNBC phenotypes: locally aggressive and highly metastatic, respectively [14] In these models, treatment with 177LuNM600 afforded tumor control and extended overall survival while showing a favorable dosimetry and toxicity profile that merits further exploration of this agent in human subjects
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