Manganese-DCTA complex as highly-stable paramagnetic contrast agent for MRI studies

Manganese-DCTA complex as highly-stable paramagnetic contrast agent for MRI studies Poster No.: C-1150 Congress: ECR 2010 Type: Topic: Scientific Exhibit Contrast Media Authors: W. Y. Ussov, M. L. Belyanin, O. Y. Borodin, A. A. Churin, T. V. Dubskaya, V. D. Filimonov; Tomsk/RU Keywords: DOI: MEMRI, Mn-DCTA, Cyclomang 10.1594/ecr2010/C-1150 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. www.myesr.org Page 1 of 16

Purpose The toxicity of free Gadolinium remains among essential problems of further development as well as of clinical use of contrast media for the MRI, and could be solved by introduction of non-gadolinium-based agents only. The manganese-enhanced MRI (MEMRI) is in wide use in physiological studies but remains still in a couple of steps to go to approach a wide clinical use [1]. Employment of Manganese complexes of DTPA and DTPA-like complexons was suggested in the mid-80-s [2], when the first experiences with Gd-DTPA were presented [3]. Recently we have tested the toxicologic and diagnostic properties of Mn-DTPA complex and obtained every evidence for it's applicability as paramagnetic contrast suitable for routine MRI studies [4]. Nevertheless the increase in R1-relaxivity and low osmolality of Mn-based MRI contrast agents is necessary in order to obtain a real substitute of potentially toxic Gd-based contrast agents. Hencefore the preclinical evaluation of the 0.5 M solution of the Manganese(II) -trans-1,2- diaminocyclohexane- N,N,N',N'-tetraacetate (Mn-DCTA, Cyclomang) has been carried out in order to promote the Mangenese complexes' employment and to make the use of paramagnetic contrast agents for the MRI economically more available for daily clinical routines. Methods and Materials Phantom and in vivo animal studies. The toxicologic tests of the Mn(II)-DCTA were carried out in mouses, rats and rabbits. Liquid phantoms served for calculation of relxivities and for direct comparison of properties of the Mn(II)-DCTA to increase the intensity of T1-weighted SE-images with contrast properties of the Gd(III)-DTPA as well as of Mn-DTPA. Dogs with traumatic damages of intervertebral discs (n = 8) and with chest tumors (n=6) from routine veterinary patients were included to the study for quantification of diagnostic imaging abilities of the Mn(II)-DCTA. Tests in human subjects. Also five healthy volunteers were imaged in order to verify absence of toxic effects on basal ganglii (typical for free Manganese). Page 2 of 16

Later on the imaging abilities in human pathology were tested in six patients with glial tumors of the brain. In particular dynamic studies of uptake kinetics to the tumor were carried out as well as T1-weighted spin-echo and gradient-echo studies before and after injection of Mn-DCTA. The injection dose was in all cases normalized to the body weight, as 2 ml of 0,5M solution of Mn-DCTA per 10 kg of BW. The increase in brightness of the T1-weighted MRI scan induced by use of the Mn-DCTA was quantified using index of enhancement (IE) as ratio of signal intensities (SI) of T1- weighted images after injection of the paramagnetic to the SI of the precontrast scan: IE = (SI of T1-wMRI Mn-DCTA ) / (SI of T1-wMRI Precontrast ). Results Biophysical parameters and toxicologic tests of the Mn-DCTA. The biophysical constants of the Mn-DCTA are presented in the following Table. Stability constant, at ph=7,4 Relaxivity R 1, at B o =0,2T, Mn-DCTA Mn-DTPA Gd-DTPA 17.8 15.6 18.1 3,68 3,25 3,75 mmol -1 *s -1 Viscosity, mpa*s 2,97 ± 0,07 2,77 ± 0,07 2,90 ± 0,05 Osmolality, at 37 C, mosmol/ (Kg H 2 O) 1754 ± 21 1947 ± 34 1955 ± 15 Biophysical parameters of the Mn-DCTA, as compared to Mn-DTPA and Gd-DTPA Blood samples in rats when analyzed for the content of the free Manganese (II) have shown no release of Mn from the complex to the plasma. Page 3 of 16

The LD 50 in rats was over 17 ml/kg, essentially close and slightly over to that one of Gd(III)-DTPA and also to Mn-DTPA, as seen in the herefollowing Table. Mn-DCTA, Mn-DTPA, Gd-DTPA, LD 50, ml/kg BW, single i/v injection 0,5M solution 0,5M solution 17.1 14,1 16,9 LD 50 in Mn-DCTA vs Gd-DTPA and Mn-DTPA 0,5M solution The blood samples data in rats as well as all morphologic data from hystologic tests remained unchanged during two-weeks-long follow-up after single injection of Mn-DCTA in a dose as high as 10 ml of 0,5M Mn-DCTA per 10 Kg of BW. In-vivo imaging in dogs. The increase in intensity of the T1-weighted images induced by addition of the Mn(II)- DCTA did not differ significantly from the values obtained with Magnevist. Mn(II)-DCTA delivered prominent enhancement of normal kidneys in dogs and human volunteers as well as of damaged areas in dogs studies due to spinal trauma. Fig.: Case of Mn-DCTA enhanced MRI study in a dog with traumatic damage of intervertebral disc. Inflammatory posttraumatic responce of epidural tissue is evidenton the contrast enhance T-1 weighted sagittal SE MRI scan Page 4 of 16

References: W. Y. Ussov; Lab. of Tomography, Institute of Cardiology, Tomsk, RUSSIAN FEDERATION Page 5 of 16

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Fig.: Imaging of the uptake of Mn-DCTA to the primary lung tumor and it's metastases in a dog (male rotweiler, nine years old, 35 Kg BW). Axial T1-weighted axial slices of the chest, TR = 420 ms, TE = 17 ms, slices 5mm thick, no ECG-gating. The right column presents the initial nonenhanced slices, the slices after paramagnetic enhancement with 6 ml of the 0,5M Mn-DCTA are in the left column. Slices were placed below bifurcation of the trachea (a and b), at the mid of the left ventricle (c and d) and at the top af the diaphragm (e and f). There is a significant increase in intensity of the T1-weighted MRI scans over peripheral (1) and central (2) regiones of the tumor of the right lung, as well as over metastases to paratracheal lymph nodes (3), chest wall with rib involvement (4) paraaortal lymph nodes (5), and also over parietal pleura on the left side (6), with local carcinomatous pleuritis (the area is depicted with the thin ellipse) References: W. Y. Ussov; Lab. of Tomography, Institute of Cardiology, Tomsk, RUSSIAN FEDERATION In-vivo imaging in human volunteers. In healthy human volunteers the only organ which demonstrated prominent uptake of Mn- DCTA was the kidney, whereas no parenchymal uptake of this agent was seen anywhere else. Fig.: Typical feature of Mn-DCTA uptake to the kidney in a healthy human subject when employing the T1-weighted SE MRI. The right scan was acquired before and the left one in three minutes after the injection of 10 ml of 0,5M Mn- DCTA per 75 Kg of BW. Obvious enhancement of kidney parenchyma due to glomerular filtration of Mn-DCTA is seen. Page 7 of 16

References: W. Y. Ussov; Lab. of Tomography, Institute of Cardiology, Tomsk, RUSSIAN FEDERATION In-vivo imaging in patients with glial brain tumors. Fig.: Sequence of T1-weighted axial MRI scans acquired every 30 secs after i/v injection of Mn-DCTA to a patient with glioblastoma multiforme of the left hemisphere. Early enhancement of the tumor is seen at the first minute of study approaching the maximum at the third minute. References: W. Y. Ussov; Lab. of Tomography, Institute of Cardiology, Tomsk, RUSSIAN FEDERATION Page 8 of 16

Fig.: Time plot of the signal intensities of T1-weighted axial MRI images in the course of five minutes long dynamic uptake study after injection of Mn-DCTA to the lady with glial tumor (glioblastoma multiforme). The dynamic images are presented before. References: W. Y. Ussov; Lab. of Tomography, Institute of Cardiology, Tomsk, RUSSIAN FEDERATION Page 9 of 16

Fig.: Typical T1-weighted SE-images of Mn-DCTA accumulation to the glial tumor. The tumor not well depicted on the nonenhanced T1-w axial scan is clearly imaged with Mn-DCTA injection T1-w image and even more clear with the subtraction scan, obtained as difference between post-contrast and pre-contrast slices, aligned by rigid registration algorythm each to other. References: W. Y. Ussov; Lab. of Tomography, Institute of Cardiology, Tomsk, RUSSIAN FEDERATION Images for this section: Page 10 of 16

Fig. 1: Sequence of T1-weighted axial MRI scans acquired every 30 secs after i/v injection of Mn-DCTA to a patient with glioblastoma multiforme of the left hemisphere. Early enhancement of the tumor is seen at the first minute of study approaching the maximum at the third minute. Fig. 2: Typical feature of Mn-DCTA uptake to the kidney in a healthy human subject when employing the T1-weighted SE MRI. The right scan was acquired before and the left one in three minutes after the injection of 10 ml of 0,5M Mn-DCTA per 75 Kg of BW. Obvious enhancement of kidney parenchyma due to glomerular filtration of Mn-DCTA is seen. Page 11 of 16

Fig. 3: Time plot of the signal intensities of T1-weighted axial MRI images in the course of five minutes long dynamic uptake study after injection of Mn-DCTA to the lady with glial tumor (glioblastoma multiforme). The dynamic images are presented before. Page 12 of 16

Fig. 4: Typical T1-weighted SE-images of Mn-DCTA accumulation to the glial tumor. The tumor not well depicted on the nonenhanced T1-w axial scan is clearly imaged with Mn- DCTA injection T1-w image and even more clear with the subtraction scan, obtained as difference between post-contrast and pre-contrast slices, aligned by rigid registration algorythm each to other. Fig. 5: Case of Mn-DCTA enhanced MRI study in a dog with traumatic damage of intervertebral disc. Inflammatory posttraumatic responce of epidural tissue is evidenton the contrast enhance T-1 weighted sagittal SE MRI scan Page 13 of 16

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Fig. 6: Imaging of the uptake of Mn-DCTA to the primary lung tumor and it's metastases in a dog (male rotweiler, nine years old, 35 Kg BW). Axial T1-weighted axial slices of the chest, TR = 420 ms, TE = 17 ms, slices 5mm thick, no ECG-gating. The right column presents the initial nonenhanced slices, the slices after paramagnetic enhancement with 6 ml of the 0,5M Mn-DCTA are in the left column. Slices were placed below bifurcation of the trachea (a and b), at the mid of the left ventricle (c and d) and at the top af the diaphragm (e and f). There is a significant increase in intensity of the T1-weighted MRI scans over peripheral (1) and central (2) regiones of the tumor of the right lung, as well as over metastases to paratracheal lymph nodes (3), chest wall with rib involvement (4) paraaortal lymph nodes (5), and also over parietal pleura on the left side (6), with local carcinomatous pleuritis (the area is depicted with the thin ellipse) Page 15 of 16

Conclusion We conclude the Mn(II)-DCTA can be suggested for employment as paramagnetic contrast agent in routine contrast-enhanced MRI studies and is worth clinical testing. References 1. Pautler R.G. Biological applications of manganese-enhanced magnetic resonance imaging. // Methods. Mol.Med. 2006; 124: 365-286 2. Marotti M., Schmiedl U., White D. et al.metal chelates as urographic contrast agents for magnetic resonance imaging. A comparative study.// Röfo.1987; 146(1): 89-93. 3. Carr D.H., Brown J., Bydder G.M. et al. Gadolinium-DTPA as a contrast agent in MPI: Initial clinical experience in 20 patients.// Am. J. Radiol. 1984; 143(2): 215-224. 4. Churin AA, Karpova GV, Fomina TI, Vetoshkina TV, Dubskaia TIu, Voronova OL, Filimonov VD, Belianin ML, Usov VIu. Preclinical toxicological evaluation of Pentamang and Mangascan.// Eksp Klin Farmakol. 2008 Jul- Aug;71(4):49-52. Personal Information Page 16 of 16