Radiopaque polymers

Abstract

A liquid composition comprising a polymer having pendant groups of the formula I: (I) Wherein X is either a bond or is a linking group having 1 to 8 carbons and optionally 1 to 4 heteroatoms selected from O, N and S; and n is 1 to 4. ##STR00001##

Claims

1. A liquid embolic composition suitable for therapeutic embolization, the composition comprising a polymer in solution in an organic solvent, the polymer comprising units of the formula 1: ##STR00006## wherein X is either a bond or is a linking group having 1 to 8 carbons and optionally 1 to 4 heteroatoms selected from O, N and S; wherein n is 1 to 4; wherein the polymer precipitates on contact with normal saline at 20? C.; wherein the precipitate has a radiodensity of at least 1000HU; and wherein the polymer is biodegradable.

2. A liquid embolic composition according to claim 1 wherein n is 1, 2 or 3.

3. A liquid embolic composition according to claim 1 wherein the polymer comprises units selected from ##STR00007##

4. A liquid embolic composition according to claim 1 where X is selected from a bond, (C.sub.1-4)alkylene, (C.sub.1-4)oxyalkylene and amino(C.sub.1-4)alkylene.

5. A liquid embolic composition according to claim 1 where X is a bond.

6. A liquid embolic composition according to claim 1 wherein the polymer comprises units of the formula 3 ##STR00008##

7. A liquid embolic composition according to claim 1 comprising the polymer and a water-miscible solvent.

8. A liquid embolic composition according to claim 7 comprising between 3% and 70% wt/wt of the polymer dissolved in the water-miscible solvent.

9. A liquid embolic composition according to claim 7 wherein the water-miscible solvent is a polar aprotic solvent.

10. A liquid embolic composition according to claim 7 wherein the water-miscible solvent is selected from dimethylsulphoxide, dimethylformamide, N, N-dimethylpropyleneurea, 1,3-dimethyl-2-imidazolidinone, glycerol, ethyl lactate, N-Methyl-2-pyrrolidone and 2-(Oxolan-2-ylmethoxy)ethanol.

11. A liquid embolic composition according to claim 1 wherein n is 2 or 3.

12. A liquid embolic composition according to claim 1 wherein the polymer comprises a polyvinyl alcohol copolymer.

13. A liquid embolic composition according to claim 1 wherein the polymer is non cross linked.

14. A liquid embolic composition according to claim 1 wherein the polymer comprises iodine in an amount of 10% or greater (w/w) based on a dried weight of the polymer.

Description

FIGURES

(1) FIG. 1 illustrates the release of DMSO measured by UV absorption at 231 nm, from a selection of liquid embolic formulations of the invention.

(2) FIG. 2 illustrates the change in Precipitation Fill Volume of Liquid Embolic samples

(3) FIG. 3 illustrates the relationship between solidification time and polymer concentration for low molecular weight polymers.

(4) FIG. 4 illustrates the effect of polymer concentration on fill volume.

(5) FIG. 5 shows typical particulate formation for score values of 1-5.

(6) FIG. 6 shows the set up used to observe precipitation under flow conditions. The arrow indicates the direction of initial precipitation.

(7) FIG. 7 is a graph showing the relationship between solidification time and reflux of the embolus in test conditions.

(8) FIG. 8 shows microCT images of precipitated liquid embolic polymers prepared with 0.10 (A) 0.15 (B) and 0.20 (C) eq. TIBA

(9) The invention will now be described further by way of the following non limiting examples with reference to the figures. These are provided for the purpose of illustration only and other examples falling within the scope of the claims will occur to those skilled in the art in the light of these. All references cited herein are incorporated by reference in their entirety. Any conflict between that reference and this application shall be governed by this application.

EXAMPLES

Example 1: General Liquid Embolic Synthesis Conditions

(10) To a pre-dried reactor under a nitrogen blanket was added PVA (typically 5-10 g) and anhydrous solvent (typically DMSO or NMP, 40 vol w.r.t. PVA mass) and catalyst (typically 2.2 vol w.r.t. PVA mass). The stirred suspension was heated to elevated temperature (ca 90? C.) to dissolve the PVA. When a homogeneous solution had been obtained, the mixture was cooled to the desired reaction temperature (typically 50-80? C.). 2,3,5 Triiodo benzaldehyde (TIBAtypically 0.1 to 0.6 eq w.r.t. PVA diol functionalities) was added. The reaction was then stirred under an N.sub.2 blanket and the reaction conversion was monitored by High Performance Liquid Chromatography (HPLC) for consumption of TIBA. At a pre-determined time (typically when consumption of the chemical substrate had ceased) an anti-solvent was added (typically, acetone, Dichloromethane (DCM), Acetonitrile (MeCN) or Methyl tert-butyl ether (TBME), ca 40 vol) dropwise from a dropping funnel. The supernatant fluid was removed by aspiration through a filter membrane and further reaction solvent (typically 40 vol) was charged and stirred until the solids had fully dissolved. This solvent washing stage was repeated up to 3 times. Then the solid was re-dissolved in reaction solvent, and precipitated by the slow addition of water (typically up to 100 vol). The resulting aggregated solid was removed from the supepatant and homogenised in a blender in water (Ca 11). The suspension was filtered and re-suspended in water (typically 100 vol) and slurried for up to 30 minutes and filtered. The water slurrying was repeated until pH neutral had been obtained, then the damp solids were slurried in acetone (100 vol, 30 mins stir, 2 repetitions), filtered and dried in a high vacuum oven at 30? C. for up to 24 h. Table 1 shows iodine content of liquid embolic preparations.

(11) TABLE-US-00001 TABLE 1 Prep. MW PVA Conditions Eq TIBA Conversion Isolated Yield % I.sub.2 (w/w) 1 9-10 kDa* DMSO, 0.01 eq 100% Water sol. N/A 60? C. 2 67 kDa** DMSO, 0.07 eq 100% 78.8% 27.9% 60? C. 3 67 kDa** DMSO, 0.06 eq ND 82.9% 18.0% 60? C. 4 67 kDa** DMSO, 0.03 eq ND 59.4% 12.0% 60? C. 5 67 kDa** DMSO, 0.4 eq 91% 80.7% 55.1% 60? C. 6 67 kDa** DMSO, 0.6 eq 76% 79.9 60.1% 60? C. 7 146-186 kDa*** DMSO, 0.1 eq 100% 84.7% 30.5% 65? C. 8 146-186 kDa*** DMSO, 0.25 eq 99.9% 92.9% 47.2 65? C. 9 146-186 kDa*** DMSO, 0.4 eq 99.4% 94.1% 55.8% 65? C. 10 85-124 kDa*** DMSO, 0.1 eq 100% 94.7% 28.8% 70? C. 11 85-124 kDa*** DMSO, 0.25 eq 100% 93.6% 46.2% 70? C. 12 85-124 kDa*** DMSO, 0.4 eq 100% 91.3% 55.4% 70? C. 13 85-124 kDa*** DMSO, 0.6 eq 99.9% 89.5% 62.0% 70? C. Eq. refers to the equivalents relative to free diol units on the PVA backbone. *= 80% hydrolysed **= 88% hydrolysed ***= 100% hydrolysed.

Example 2: Formulation of Iodinated PVA Liquid Embolic Prototypes

(12) Prototype formulations were prepared as follows: iodinated PVA prepared according to general example 1, was weighed into a 10 ml vial, to which was added the desired solvent (typically DMSO or NMP) such that the overall concentration was in the range 4-20% w/w with a total volume being less than 10 ml. The vial containing the suspension was then sealed and placed in a sonicator, and sonicated until complete dissolution had occurred (typically ca 4 hours). Table 1 provides example liquid embolic Formulations.

(13) TABLE-US-00002 TABLE 2 Example liquid embolic formulations. PVA PVA Concentration Sample Molecular TIBA in DMSO Number Weight Equivalent (w/w %) 1 67 kDa 0.25 8 2 67 kDa 0.25 20 3 67 kDa 0.20 20 4 67 kDa 0.40 4 5 67 kDa 0.40 8 6 67 kDa 0.40 12 7 67 kDa 0.40 16 8 67 kDa 0.60 4 9 67 kDa 0.60 8 10 67 kDa 0.60 12 11 67 kDa 0.60 16 12 85-124 kDa 0.10 8 13 85-124 kDa 0.25 8 14 85-124 kDa 0.40 8 15 85-124 kDa 0.60 8 16 146-186 kDa 0.10 4 17 146-186 kDa 0.10 8 18 146-186 kDa 0.25 4 19 146-186 kDa 0.25 8 20 146-186 kDa 0.40 4 21 146-186 kDa 0.40 8

Example 3 Precipitate Solidification

(14) Elution of the solvent (DMSO) from the liquid samples was used as a measure of the progress of solidification. Testing was performed in a Sotax USP II dissolution bath connected to a UV spectrophotometer. The dissolution bath was set to 37.5? C. and each vessel filled with 500 mL of phosphate buffered saline (PBS) with stirring at 50 rpm.

(15) The elution of DMSO within the vessel was measured by UV at the wavelength of 231 nm over time (maximum of 2 hours), giving an indication of the rate at which a liquid embolic precipitate is solidifying. 1 ml of the liquid embolic sample was withdrawn using a 3 mL DMSO compatible syringe. This was added, dropwise into the dissolution vessels via the delivery port. At two minute intervals additional samples were added to the remaining Sotax USP II dissolution vessels. Once all samples had been added, the system was left to run for the total measurement run time. At the completion of the measurement run time, the system was stopped and the precipitate was retained for further analysis. The Solidification Time recorded was the point at which 90% of DMSO had been eluted from the precipitate. The percentage of the DMSO eluted from the liquid embolic was based upon the point where the curve had plateaued to remove the influence of the flushes of DMSO observed in samples which precipitate immediately on impact in the PBS (see FIG. 1).

(16) Tables 2a to 2c illustrate the precipitation times for liquid embolic preparations.

(17) TABLE-US-00003 TABLE 2a Precipitation times for low molecular weight preparations Radiopaque Polymer Group Concentration Solidification Sample (TIBA) in DMSO Time (>90%) Number Equivalent (%) (mm:ss) 1 0.25 8 01:37 2 0.25 20 05:13 3 0.20 20 05:35 4 0.40 4 00:17 5 0.40 8 03:42 6 0.40 12 05:13 7 0.40 16 06:07 8 0.60 4 00:22 9 0.60 8 03:59 10 0.60 12 05:42 11 0.60 16 05:42

(18) TABLE-US-00004 TABLE 2b Precipitation times for medium molecular weight preparations Radiopaque Polymer Group Concentration Solidification Sample (TIBA) in DMSO Time (>90%) Number Equivalent (%) (mm:ss) 12 0.10 8 00:22 13 0.25 8 06:50 14 0.40 8 09:21 15 0.60 8 05:24

(19) TABLE-US-00005 TABLE 2c Precipitation times for high molecular weight preparations. Radiopaque Polymer Group Concentration Solidification Sample (TIBA) in DMSO Time (>90%) Number Equivalent (%) (mm:ss) 16 0.10 4 00:22 17 0.10 8 Not Performed 18 0.25 4 00:22 19 0.25 8 09:00 20 0.40 4 00:22 21 0.40 8 05:24

(20) FIG. 3 Illustrates the relationship between solidification time and polymer concentration for low molecular weight polymers.

Example 4: Precipitation Fill Volume

(21) Precipitation fill volume provides a measurement of the percentage reduction in volume of liquid embolic samples after the samples precipitates in PBS and of how much solid precipitate is formed from a known liquid volume.

(22) 15 ml of PBS was added to a clean, dry medium sized glass petri dish (approximately 10 cm in diameter) and a known volume of the liquid embolic to be tested (ideally 0.5 ml) was deposited dropwise into the PBS solution and allowed to solidify for 10 minutes. Once the samples had solidified for 10 minutes, the precipitate was removed and air dried on a sheet of filter paper. Precipitate volume was then measured by displacement in PBS. FIG. 2 illustrates volume reduction values of the liquid embolic samples.

(23) Table 3 illustrates precipitation fill volume changes with polymer concentration. FIG. 4 illustrates the effect of polymer concentration on fill volume

(24) TABLE-US-00006 TABLE 3 Radiopaque Polymer Change Group Concentration in Fill Sample (TIBA) in DMSO Volume Number Equivalent (%) (%) 1 0.25 8 ?77 2 0.25 20 ?46 3 0.20 20 ?33 4 0.40 4 ?85 5 0.40 8 ?58 6 0.40 12 ?84 7 0.40 16 ?31 8 0.60 4 ?99 9 0.60 8 ?57 10 0.60 12 ?40 11 0.60 16 ?40

Example 5: Particulate Generation

(25) Particulate generation is a measure of the cohesiveness and stability of liquid embolic precipitates.

(26) A syringe without a needle was used to deposit 0.5 mL of liquid embolic preparation, dropwise, into 30?5 ml of PBS in a 50 mL Duran bottle. The syringe was positioned at a height of 12 cm from the surface of the PBS. The liquid embolic was allowed to solidify for 10 minutes.

(27) The Duran bottle was then capped and transferred to a plate shaker for 30 minutes at 240 rpm. The steps above were repeated with additional replicates of the liquid embolic sample to be tested and the plate shaker speed altered to 400 rpm and 640 rpm. The Duran bottles were removed from the plate shaker and samples allowed to settle. Visual inspection of the Duran bottles by eye was carried out to establish whether any large fragments of the precipitates had come away from the main precipitate during shaking and photographic images captured. Using a plastic pipette (with the tip cut off) an aliquot of solution from each Duran bottle was transferred to a Petri dish and assessed under light microscopy. Examples of particulates and fragments are shown in FIG. 3. The images obtained were assessed and given a score from 1-5 based on the amount of particulates generated and fragmentation observed. A score of 1 indicates a minimal degree of particulate generation and fragmentation while 5 indicates a high degree of particulate generation.

(28) Table 4 illustrates the particle generation scores for low molecular weight polymers.

(29) TABLE-US-00007 TABLE 4 Radiopaque Polymer Group Concentration Particle Sample (TIBA) in DMSO Generation Number Equivalent (%) Score 2 0.25 20 4 3 0.20 20 1 4 0.40 4 5 5 0.40 8 1 6 0.40 12 2 7 0.40 16 1 9 0.60 8 2 10 0.60 12 1 11 0.60 16 1

Example 6: Precipitation Under Flow Conditions

(30) A clear detachable tube was attached to a flow system through which PBS was pumped through the detachable tubing using a peristaltic pump to mimic blood flow conditions. A 2.4 Fr catheter was used to deliver the liquid embolic preparation into the detachable tube. As the liquid embolic left the catheter and came into contact with PBS, it precipitated inside the detachable tubing. The length of any precipitate was then measured from the end of the catheter tip. Flow rate and rate reduction were also recorded. The longest length of advancement was recorded. If reflux had occurred, its length was also recorded as the longest length of reflux (cm). The catheter was removed from the tubing of the precipitation testing equipment, and the ease of removal recorded.

(31) Table 5 records precipitation properties of liquid embolic preparations

(32) TABLE-US-00008 TABLE 5 Radio- Longest paque Polymer Total Length Flowrate Group Conc. in Injection of Re- Catheter Sample (TIBA) DMSO Volume Reflux duction With- Number Equivalent (%) (ml) (cm) (%) drawal 4 0.40 4 1.00 1.0 98 OK 5 0.40 8 0.60 1.5 98 OK 6 0.40 12 0.50 2.0 98 OK 7 0.40 16 0.65 3.0 99 OK 8 0.60 4 1.00 Plug could not be achieved 9 0.60 8 0.90 1.0 98 OK 10 0.60 12 0.65 8.0 99 Stuck 11 0.60 16 0.60 3.0 99 OK

Example 7: Measurement of Radiopacity

(33) In order to obtain radiopacity measurements for the material, 1 cm sections of the precipitated formulation from Example 6 were cut and embedded in warm 1% agarose gel (prepared with Sigma-Aldrich product code A9539). The samples were prepared in Nunc cryotube vials (Sigma-Aldrich product code V7634, 48 mm?12.5 mm) and scanned using Micro-CT using a Bruker Skyscan 1172 Micro-CT scanner at the RSSL Laboratories, Reading, Berkshire, UK, fitted with a tungsten anode. Each sample was analysed using the same instrument configuration with a tungsten anode operating at a voltage of 64 kV and a current of 155 ?A. An aluminium filter (500 ?m) was used.

(34) A summary of the acquisition parameters is given in Table 6.

(35) TABLE-US-00009 TABLE 6 Version 1.5 Software: SkyScan1172 Version 1.5 (build 14) NRecon version 1.6.9.6 CT Analyser version 1.13.1.1 Source Type: 10 Mp Hamamatsu 100/250 Camera Resolution 4000 ? 2096 (pixel): Camera Binning: 1 ? 1 Source Voltage 65 kV Source Current uA 153 Image Pixel Size (um): 3.96 Filter Al 0.5 mm Rotation Step (deg) 0.280 Output Format 8 bit BMP Dynamic Range 0.000-0.140 Smoothing 0 Beam Hardening 0 Post Alignment corrected Ring Artefacts 16

(36) Water (MilliQ?) blanks were scanned separately, prior to samples on the day of acquisition. Each sample was then analysed by X-Ray micro-computer. The samples may then be reconstructed using NRecon and calibrated against a volume of interest (VOI) of the purified water reference. A two part analysis method was used. Initially an interpolated region of interest is created coving the inner tube diameter to include the plug and any void structures then the image is segmented to isolate the polymer from the void structures. The radiodensity in HU was then calculated using the water standard acquired on the same day.

(37) Table 8 shows the radiodensity values for liquid embolic preparations from Example 1, Table 1, prepared as 8% w/w solutions in DMSO and having varying levels of TIBA to PVA ratios. FIG. 8 shows microCT scans of precipitated liquid embolic polymers prepared with 0.10 (A) 0.15 (B) and 0.20 (C) eq. TIBA.

(38) TABLE-US-00010 TABLE 8 Object Total Avg. Avg. grey Obj grey TIBA scale Avg. Vol. scale Avg. Eq. value HU (%) value HU 0.25 66.64 3028.19 33.32 38.07 1301.57 0.4 81.59 3651.16 44.54 51.7 1947.08 0.6 93.19 4312.8 44.94 60.4 2443.26