SPL Set ID: 72f31b09-4d7b-475c-b37a-9daf2ad80240

Chemical Characteristics The active ingredient in Lymphoseek, a radioactive diagnostic agent, is technetium Tc 99m tilmanocept. Technetium Tc 99m binds to the diethylenetriaminepentaacetic acid (DTPA) moieties of the tilmanocept molecule. • Chemically, technetium Tc 99m tilmanocept consists of technetium Tc 99m, dextran 3-[(2-aminoethyl)thio]propyl 17-carboxy-10,13,16-tris(carboxymethyl)-8-oxo-4-thia-7,10,13,16-tetraazaheptadec-1-yl 3-[[2-[[1-imino-2-(D-mannopyranosylthio)ethyl]amino]ethyl]thio]propyl ether complexes. • The molecular formula of technetium Tc 99m tilmanocept is [C 6 H 10 O 5 ] n .(C 19 H 28 N 4 O 9 S 99m Tc) b .(C 13 H 24 N 2 O 5 S 2 ) c .(C 5 H 11 NS) a . It contains 3-8 conjugated DTPA (diethylenetriaminepentaacetic acid) molecules (b); 12-20 conjugated mannose molecules (c) with 0-17 amine side chains (a) remaining free. • The calculated average molecular weight of tilmanocept ranges from 15,281 to 23,454 g/mol. • Technetium Tc 99m tilmanocept has the following structural formula: Lymphoseek is supplied as a kit which contains five vials, 250 mcg tilmanocept per vial. Each Lymphoseek vial contains the non-radioactive ingredients needed to produce technetium Tc 99m tilmanocept. The vial contains a sterile, non-pyrogenic, white to off-white lyophilized powder (under nitrogen) that consists of a mixture of 250 mcg tilmanocept, 20 mg trehalose dihydrate, 0.5 mg glycine, 0.5 mg sodium ascorbate, and 0.075 mg stannous chloride dihydrate. Sodium hydroxide and hydrochloric acid may be used to adjust the pH prior to lyophilization. The DILUENT for Lymphoseek contains 4.5 mL sterile buffered saline consisting of 0.04% (w/v) potassium phosphate, 0.11% (w/v) sodium phosphate (heptahydrate), 0.5% (w/v) sodium chloride, and 0.4% (w/v) phenol. Physical Characteristics Technetium Tc 99m decays by isomeric transition with a physical half-life of approximately 6 hours. The principal photon that is useful for detection and imaging studies is listed in Table 4 . Table 4. Principal Radiation Emission Data From: Kocher, D.C. Radioactive decay data tables. DOE/TIC-11026, 108 (1981). Radiation Mean % Disintegration Mean Energy (keV) Gamma-2 89.1 140.5 External Radiation The linear mass energy absorption attenuation coefficient for Tc 99m is 18.9 cm -1 . The first half-value layer is 0.037 cm of lead (Pb). The use of a 0.25 cm thick standard radiation lead shield will attenuate the radiation emitted by millicurie amounts of technetium Tc 99m by a factor of about 100. A range of values for the relative attenuation of the radiation of technetium Tc 99m that results with various thicknesses of lead shielding are displayed in Table 5 . Table 5. Radiation Attenuation by Lead Shielding Shield Thickness, cm of lead (Pb) Coefficient of Attenuation 0.037 0.5 0.12 10 -1 0.24 10 -2 0.36 10 -3 0.49 10 -4 To correct for physical decay of the radionuclide, the fractions that remain at selected intervals after the time of calibration are shown in Table 6 . Table 6. Physical Decay Chart; Tc 99m, Half-Life of approximately 6 Hours Hours Fraction Remaining 0 1 1 0.891 3 0.708 6 0.501 12 0.251 15 0.178 Structural Formula