DTPA prodrugs, compositions thereof, and methods of using the same

1. A polymorph of 6,9-bis(carboxymethyl)-3-(2-ethoxy-2-oxoethyl)-11-oxo-12-oxa-3,6,9-triazatetradecan-1-oic acid characterized by a powder x-ray diffraction pattern substantially the same as that shown in FIG. 6A and/or a powder x-ray diffraction pattern having peaks at about 7.6, 12.4, 13.5, 14.0, 15.3, 18.1, 18.7, 18.8, 21.0, 22.5, 23.4, 24.5, 28.7, and 35.7±0.2 degrees 2 theta,

wherein the polymorph has a melting point in a range from about 110° C. to about 121° C.

2. The polymorph of claim 1 , wherein the melting point is measured using differential scanning calorimetry over a range of about 25°C to about 320° C with a heating rate of about 10.00° C/min.

3. A process of preparing the polymorph of 6,9-bis(carboxymethyl)-3-(2-ethoxy-2-oxoethyl)-11-oxo-12-oxa-3,6,9-triazatetradecan-1-oic acid of claim 1 , comprising

(a) combining DTPA bis-anhydride, ethanol, and pyridine to form a reaction mixture;

(b) stirring the reaction mixture under nitrogen for about 24 hours;

(c) adding the reaction mixture to dichloromethane to form a dichloromethane solution;

(d) cooling the dichloromethane solution to a temperature of about −20° C. to form a precipitate of a polymorph of 6,9-bis(carboxymethyl)-3-(2-ethoxy-2-oxoethyl)-11-oxo-12-oxa-3,6,9-triazatetradecan-1-oic acid;

(e) filtering the dichloromethane solution to obtain the precipitate;

(f) optionally washing the precipitate with dichloromethane during the filtering step; and

(g) optionally drying the precipitate, thereby obtaining the polymorph.

4. A method of treating a subject to remove a radioactive element from the subject comprising:

administering a therapeutically effective amount of the polymorph of claim 1 to a subject, thereby removing the radioactive element from the subject.

5. The method of claim 4 , wherein the administering step delivers to the subject from about 1 mg to about 2,000 mg of the polymorph per kilogram of the subject's total body weight.

6. The method of claim 4 , wherein the administering step is prior to the subject's exposure to a radioactive element.

7. The method of claim 6 , wherein the administering step is carried out to prevent incorporation of a radioactive element into the subject's tissues, organs, bones, or any combination thereof.

8. The method of claim 4 , wherein the administering step is after the subject's exposure to a radioactive element.

9. The method of claim 4 , wherein the radioactive element comprises an isotope of plutonium (Pu), americium (Am), curium (Cm), or any combination thereof.

10. The method of claim 4 , wherein the subject is a mammal.