99mTc-EC-Annexin V

**99mTc-EC-Annexin V** is a radiolabeled imaging agent designed for SPECT (single-photon emission computed tomography) to detect apoptosis in vivo. It consists of annexin V conjugated to EC (ethylene dicysteine) as a chelator for the gamma-emitting isotope technetium-99m (99mTc), enabling high specific activity labeling with radiochemical purity near 100%. Annexin V binds with high affinity to phosphatidylserine exposed on the outer membrane of apoptotic cells, allowing non-invasive quantification of tumor apoptosis. Developed using standard coupling techniques, it has been tested in preclinical tumor-bearing rat models and a clinical study of 10 patients with primary invasive breast cancer (stage II-III), where 9/10 showed detectable tumor uptake with mean tumor-to-non-tumor (T/N) ratios of 2.1 (higher post-induction chemotherapy at 2.6 vs. 1.5 pre-treatment), correlating with treatment response. Dosimetry estimates indicate an effective dose of ~6.8-7.9 mSv for 925-1073 MBq, primarily to liver (8.65-10.03 mSv), supporting clinical feasibility as a biomarker for baseline apoptosis, therapy efficacy prediction, and prognosis in oncology.[1][2][4][6]

Other names

99mTc EC-annexin