Microparticle production process and apparatus

Abstract

Provided is an apparatus for producing solid polymeric microparticles, the apparatus comprising a plurality of liquid droplet generators for forming liquid droplets of a first liquid, and a nozzle for forming a jet of a second liquid, wherein the plurality of liquid droplet generators and the nozzle are arranged relative to each other such that, in use, liquid droplets from the plurality of liquid droplet generators pass through a gas into said jet of second liquid. Also provided is a process for producing solid microparticles, the process comprising: providing a first liquid comprising a solute and a solvent, the solute comprising a biocompatible polymer, the concentration of polymer in the first liquid being at least 10% w/v, ‘w’ being the weight of the polymer and ‘v’ being the volume of the solvent, providing a plurality of liquid droplet generators operable to generate liquid droplets, providing a jet of a second liquid, causing the plurality of liquid droplet generators to form liquid droplets of the first liquid, passing the liquid droplets through a gas to contact the jet of the second liquid so as to cause the solvent to exit the droplets, thus forming solid microparticles, the solubility of the solvent in the second liquid being at least 5 g of solvent per 100 ml of second liquid, the solvent being substantially miscible with the second liquid.

Claims

1. An apparatus for producing solid polymeric microparticles, the apparatus comprising: a plurality of liquid droplet generators for forming liquid droplets of a first liquid, wherein the plurality of liquid droplet generators comprise at least one piezoelectric component operable to generate droplets at a frequency of at least 1 kHz per droplet generator; and a nozzle for forming a jet of a second liquid, wherein the plurality of liquid droplet generators and the nozzle are arranged relative to each other such that, in use, liquid droplets from the plurality of liquid droplet generators pass through a gas into said jet of second liquid in a liquid droplet contact zone of said jet of second liquid, and wherein the jet of second liquid is not in contact with any wall or channel for at least the length of said liquid droplet contact zone.

2. The apparatus according to claim 1, wherein the plurality of liquid droplet generators are in the form of an inkjet printhead.

3. The apparatus according to claim 1, wherein the plurality of liquid droplet generators each comprise a droplet generator outlets and wherein the droplet generator outlets are in a line or an array.

4. The apparatus according to claim 3, wherein the line or array of droplet generator outlets is substantially parallel to the jet direction of said nozzle.

5. The apparatus according to claim 1, wherein the number of liquid droplet generator outlets is in the range 5 to 2500.

6. The apparatus according to claim 1, wherein the plurality of liquid droplet generators are operable to generate liquid droplets having an individual droplet volume in the range 1 to 100 pL.

7. The apparatus according to claim 1, further comprising a microparticle-receiving means for receiving solid microparticles dispersed in a jet of liquid.

8. The apparatus according to claim 1, further comprising means for generating flow of liquid through said nozzle.

9. The apparatus according to claim 8, wherein said means for generating flow comprises a regulated pressure system for producing a pulseless flow of liquid.

10. The apparatus according to claim 1, further comprising a camera for monitoring liquid droplets generated by said plurality of liquid droplet generators.

11. The apparatus according to claim 10, further comprising a light source for illuminating liquid droplets generated by said plurality of liquid droplet generators.

12. The apparatus according to claim 11, wherein said light source comprises an LED strobe electrically coordinated with the plurality of liquid droplet generators such that, in use, the camera is able to capture an image of liquid droplets ejected from the plurality of liquid droplet generators at a pre-determined time period after ejection of said liquid droplets.

13. The apparatus according to claim 12, wherein the LED strobe has an adjustable strobe delay, adjustable strobe intensity and/or adjustable pulse width settings, thereby allowing said pre-determined time period after ejection of said droplets to be adjusted.

14. The apparatus according to claim 1, further comprising at least one temperature regulator for controlling the temperature of liquid entering said plurality of liquid droplet generators and/or the temperature of liquid entering said nozzle.

15. The apparatus according to claim 14, wherein the at least one temperature regulator comprises a first chiller for controlling the temperature of the first liquid entering the plurality of liquid droplet generators in the range of 5° C. to 30° C.

16. The apparatus according to claim 14, wherein the at least one temperature regulator comprises a second chiller for controlling the temperature of the second liquid entering the nozzle in the range of 0° C. to 20° C.

17. The apparatus according to claim 1, wherein the plurality of liquid droplet generators are positioned relative to the nozzle such that the distance of travel of a liquid droplet from the outlet of a liquid droplet generator to the jet is in the range 2 to 10 mm.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows an illustration (not to scale) of the desolvation process by which solvent diffuses out of a liquid droplet in contact with the continuous phase thereby producing a solid microsphere.

(2) FIG. 2 shows a schematic diagram of a piezoelectric droplet generator (printhead).

(3) FIG. 3 shows a schematic illustration of an apparatus embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) In describing the present invention, the following terms will be employed, and are intended to be defined as indicated below.

(5) Microparticles

(6) Microparticles in accordance with the present invention may be in the form of solid beads. As used herein in connection with microparticles or beads, solid is intended to encompass a gel. Microparticles as used herein specifically include any polymeric particle or bead of micron scale (typically from 1 μm up to 999 μm in diameter). The microparticles may be of substantially spherical geometry (also referred to herein as “microspheres”). In particular, the ratio of the longest dimension to the shortest dimension of the microparticle may be not more than 5, 4, 3, 2, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1, 1.05 or not more than 1.01.

(7) Jet

(8) As used herein, a “jet” is a coherent stream of fluid that is projected into a surrounding medium from a nozzle or aperture. In particular, a jet of second liquid (continuous phase) may be a coherent stream of the second liquid projected into a gas (typically air) from a nozzle. The jet may define a flow path, at least part of which is not in contact with any solid wall, conduit or channel. The jet may define a flow path (e.g. a line or arc) that intersects with the path or paths of liquid droplets dispensed from the plurality of droplet generators. For example, the jet may be a stream of the second liquid passing through air below the plurality of droplet generators, whereby liquid droplets dispensed from the droplet generators pass through the gas under the assistance of gravity into the stream of the second liquid and are carried by said stream of second liquid. Typically, surface tension of the second liquid contributes to the jet taking the form of coherent stream. In some cases, the jet has a substantially circular cross-section. However, other cross sectional shapes (e.g. flattened or oval-like) are specifically contemplated and may be provided, e.g., by means of particular nozzle shapes.

(9) Biocompatible Polymer

(10) The polymer is typically a biocompatible polymer. “Biocompatible” is typically taken to mean compatible with living cells, tissues, organs, or systems, and posing minimal or no risk of injury, toxicity, or rejection by the immune system. Examples of polymers which may be used are polylactides (with a variety of end groups), such as Purasorb PDL 02A, Purasorb PDL 02, Purasorb PDL 04, Purasorb PDL 04A, Purasorb PDL 05, Purasorb PDL 05A Purasorb PDL 20, Purasorb PDL 20A; polyglycolides (with a variety of end groups), such as Purasorb PG 20; polycaprolactones; polyanhydrides, and copolymers of lactic acid and glycolic acid (with a variety of end groups, L:G ratios and molecular weight can be included), such as Purasorb PDLG 5004, Purasorb PDLG 5002, Purasorb PDLG 7502, Purasorb PDLG 5004A, Purasorb PDLG 5002A, resomer RG755S, Resomer RG503, Resomer RG502, Resomer RG503H, Resomer RG502H, RG752, RG752H, or combinations thereof. In some cases, it is preferred that the solute is substantially insoluble in water (it is convenient to use water as the second liquid). If the second liquid comprises water, it is preferred that the solvent is a water-miscible organic solvent, such as dimethyl sulfoxide (DMSO), n-methyl pyrrolidone, hexafluoro-isopropanol, glycofurol, PEG200 and PEG400.

(11) The weight average molecular weight (MW) of the polymer may be from 4 to 700 kDaltons, particularly if the polymer comprises a poly (α-hydroxy) acid. If the polymer comprises a copolymer of lactic and glycolic acid (often called “PLGA”), said polymer may have a weight average molecular weight of from 4 to 120 kDaltons, preferably of from 4 to 15 kDaltons.

(12) If the polymer comprises a polylactide, said polymer may have a weight average molecular weight of from 4 to 700 kDaltons.

(13) The polymer may have an inherent viscosity of from 0.1-2 dl/g, particularly if the polymer comprises a poly (α-hydroxy) acid. If the polymer comprises a copolymer of lactic and glycolic acid (often called “PLGA”), said polymer may have. an inherent viscosity of from 0.1 to 1 dl/g, and optionally of from 0.14 to 0.22 dl/g. If the polymer comprises a polylactide, said polymer may have an inherent viscosity of from 0.1 to 2 dl/g, and optionally of from 0.15 to 0.25 dl/g. If the polymer comprises a polyglycolide, said polymer may have an inherent viscosity of from 0.1 to 2 dl/g, and optionally of from 1.0 to 1.6 dl/g. It is preferred that the first liquid comprises a target material which is desired to be encapsulated within the solid microparticles. However, it is specifically contemplated herein that the process of the present invention may, in certain cases, not include a target material. For example, the process may be used to produce placebo microparticles, e.g., for use as a negative control in an experiment or clinical trial.

(14) Target Material

(15) The target material (also known as the “payload”) may be incorporated in the first liquid as a particulate or may be dissolved. The target material may comprise a pharmaceutically active agent, or may be a precursor of a pharmaceutically active agent. In some cases, the target material comprises a pharmaceutically active agent, or precursor (e.g. prodrug) thereof, for treatment of a tumour, a central nervous system (CNS) condition, an ocular condition, an infection or an inflammatory condition. In some cases, the target material may comprise a peptide, a hormone therapeutic, a chemotherapeutic or an immunosuppressant. In certain cases, said target material comprises a plurality of nanoparticles (e.g. gold nanoparticles). When present, such nanoparticles may have a pharmaceutically active agent or a precursor thereof covalently or non-covalently bound thereto.

(16) Examples of pharmaceutically active agent include, for example, any agent that is suitable for parenteral delivery, including, without limitation, fertility drugs, hormone therapeutics, protein therapeutics, anti-infectives, antibiotics, antifungals, cancer drugs, pain-killers, vaccines, CNS drugs, and immunosupressants. Particular examples include octreotide or salt thereof (e.g. octreotide acetate) and ciclosporin A or a salt thereof.

(17) The delivery of drugs in polymer microparticles, especially by controlled release parenteral, intravitreal or intracranial delivery, has particular advantages in the case of drugs which, for example, have poor water-solubility, high toxicity, poor absorption characteristics, although the invention is not limited to use with such agents. The active agent may be, for example, a small molecular drug, or a more complex molecule such as a polymeric molecule. The pharmaceutically active agent may comprise a peptide agent. The term “peptide agent” includes poly(amino acids), often referred to generally as “peptides”, “oligopeptides”, “polypeptides” and “proteins”. The term also includes peptide agent analogues, derivatives, acylated derivatives, glycosylated derivatives, pegylated derivatives, fusion proteins and the like. Peptide agents which may be used in the method of the present invention include (but are not limited to) enzymes, cytokines, antibodies, vaccines, growth hormones and growth factors.

(18) The target material (especially in the case of a pharmaceutically active agent or a precursor thereof) may be provided in an amount of 2-60% w/w compared to the weight of the polymer, optionally from 5 to 40% w/w, further optionally from 5 to 30% w/w and more optionally from 5-15% w/w.

(19) If the target material comprises a peptide agent, the first liquid may comprise one or more tertiary structure alteration inhibitors. Examples of tertiary structure alteration inhibitors are: saccharides, compounds comprising saccharide moieties, polyols (such as glycol, mannitol, lactitol and sorbitol), solid or dissolved buffering agents (such as calcium carbonate and magnesium carbonate) and metal salts (such as CaCl.sub.2, MnCl.sub.2, NaCl and NiCl.sub.2). The first liquid may comprise up to 25% w/w tertiary structure alteration inhibitors, the weight percentage of the tertiary structure alteration inhibitor being calculated as a percentage of the weight of the polymer. For example, the first liquid may comprise from 0.1 to 10% w/w (optionally from 1 to 8% w/w and further optionally from 3 to 7% w/w) metal salt and 0.1 to 15% w/w (optionally from 0.5 to 6% w/w and further optionally from 1 to 4% w/w) polyol.

(20) Second Liquid

(21) The second liquid (also referred to herein as the “continuous phase”) may comprise any liquid in which the solute (typically a polymer) is substantially insoluble. Such a liquid is sometimes referred to as an “anti-solvent”. Suitable liquids may include, for example, water, methanol, ethanol, propanol (e.g. 1-propanol, 2-propanol), butanol (e.g. 1-butanol, 2-butanol or tert-butanol), pentanol, hexanol, heptanol, octanol and higher alcohols; diethyl ether, methyl tert butyl ether, dimethyl ether, dibutyl ether, simple hydrocarbons, including pentane, cyclopentane, hexane, cyclohexane, heptane, cycloheptane, octane, cyclooctane and higher hydrocarbons. If desired, a mixture of liquids may be used.

(22) The second liquid preferably comprises water, optionally with one or more surface active agents, for example, alcohols, such as methanol, ethanol, propanol (e.g. 1-propanol, 2-propanol), butanol (e.g. 1-butanol, 2-butanol or tert-butanol), isopropyl alcohol, Polysorbate 20, Polysorbate 40, Polysorbate 60 and Polysorbate 80. Surface active agents, such as alcohols, reduce the surface tension of the second liquid receiving the droplets, which reduces the deformation of the droplets when they impact the second liquid,—thus decreasing the likelihood of non-spherical droplets forming. This is particularly important when the extraction of solvent from the droplet is rapid. If the second liquid comprises water and one or more surface active agents, the second liquid may comprise a surface active agent content of from 1 to 95% v/v, optionally from 1 to 30% v/v, optionally from 1 to 25% v/v, further optionally from 5% to 20% v/v and further more optionally from 10 to 20% v/v. The % volume of surface active agent is calculated relative to the volume of the second liquid.

(23) Printhead

(24) As used herein, “printhead” or “inkjet printhead” may be a component, typically employed in inkjet printing or inkjet material deposition, which comprises one or more chambers that act as reservoirs for a fluid to be ejected and at least two nozzles through which droplets of the fluid are ejected by virtue of force applied by a piezoelectric material operating in drop-on-demand mode. The nozzles of the inkjet printhead may be arranged in a regular pattern, such as a single row or an array having more than one row. The inkjet printhead may be a commercially available “off the shelf” inkjet printhead used “as is” or may be adapted for use in the microparticle generating methods of the present invention or may be custom made for use in the microparticle generating methods of the present invention. An example of a printhead for use in accordance with the present invention is the Konica Minolta 512LH print head, e.g. KM512LH-010532.

(25) The entire contents of WO2012/042274, WO 2012/042273 and WO 2013/014466 are expressly incorporated herein by reference for all purposes.

(26) The following is presented by way of example and is not to be construed as a limitation to the scope of the claims.

EXAMPLE

Example 1—Microsphere Generation

(27) The present invention aims to provide consistent and precise encapsulation of active drug compounds within polymer microspheres designed to release the drug into the body in a controlled manner over a prolonged period of time.

(28) The present example employs drop-on-demand inkjet technology to produce droplets in the picolitre (pL) range. The technology has been proven to produce discrete, repeatable droplets at frequencies of several kHz across multiple nozzles. Optimisation of the pressure pulse is achieved by adjusting the magnitude and duration of the electrical field supplied. The temperature at the nozzle plate can also be controlled in order to alter the viscosity of the fluid at the point of ejection.

(29) Droplet formation is tracked using an advanced viewing system (“JetXpert”) supplied by ImageXpert. The system includes a camera and LED strobe which is triggered each time a firing signal (5 Volt P-P Square Wave 50% duty cycle) is sent to the actuator of the droplet generator. The result is a static, monochromatic image of the ejected droplet at a pre-determined time period after ejection, which is refreshed over a pre-determined time allowing for monitoring of droplets potentially falling out of specification. This time period is known as the strobe delay and can be input to the software by a process operator. The delay is variable, and hence the entire droplet formation period is traceable. The system allows for viewing droplets “in motion” by assigning a Start value, End value and Step size via nanoseconds which in turn automatically starts increasing the strobe delay to follow the droplet formation and ejection path until the pre-set termination point.

(30) The viewing system can be calibrated to allow the user to ascertain important properties of the ejected droplets; namely velocity (metres per second), volume (pL), radius (μm) and its deviation from its original trajectory (values are provided via mean, standard deviation, minimum and maximum). These data can be automatically recorded in a spreadsheet to act as a batch record. Images and videos may also be taken when data is not being recorded

(31) The second fluid passes across the underside of the generator. The droplets are ejected into air, initially, before being captured by the horizontal cross flow of fluid (i.e. the jet), collecting all droplets from all nozzles in one stream.

(32) The flow beneath the droplet generator is laminar (i.e. the jet of second liquid defines a generally horizontal line or arc that passes under the droplet generator), as seen in FIG. 3. The present inventors have designed a nozzle containing an abrupt reduction to the circular cross-sectional area available for flow. This serves to increase the flow velocity in the region immediately below the generator, with the aim of ensuring ejected droplets do not coalesce. The velocity of the jet is such that droplets are immediately removed from the path of those behind them. Continuous, pulseless flow is provided by a regulated pressure system.

(33) Logic would suggest that the optimal way of avoiding coalescence would be to provide a wide flow channel at 90° to the generator's nozzle plate. However, through experimentation, the present inventors have found that precipitation is virtually instant and that firing directly along the line of the nozzle plate leads to a significant reduction in the consumption of the continuous phase, which in turn reduces cost and waste from the process.

(34) The continuous phase nozzle is mounted on a bespoke bracket designed by the present inventors which attaches to the a custom aspect-ready framework to which is in turn attached the JetXpert peripherals. Directly opposite the nozzle on the other side of the droplet generator is a receiving elbow to capture the stream which now contains solidified spheres.

(35) Both process fluids' temperatures are controlled by programmable chilling systems. The anti-solvent is chilled in-line upstream of the anti-solvent nozzle. At their point of contact, the continuous phase is 3-9° C. The dispersed phase is held at approximately 16° C. in order to maintain the stability of the drug-loaded formulation, but also to avoid freezing when agitated through priming and vacuum changes.

(36) The above-described method of microparticle generation was found to produce a larger number of microparticles per unit time and a relatively lower volume of anti-solvent was required per microparticle produced when compared with the single droplet generator nozzle per channel method described in WO2012/042273 and WO2012/042274. For example, when an inkjet printhead having 512 liquid droplet generator outlets is employed with a firing rate of 2000 to 6000 Hz, the number of microparticles produced is in the range 1024000 to 3072000 microparticles per second. The above-described method therefore provides greater potential for industrial-scale production and increased efficiency. The liquid stream containing the formed solid microparticles has a greater density of microparticles such that there is lower level of waste of the continuous phase for a given quantity of microparticles produced. Nevertheless, the microparticles produced were found to exhibit excellent uniformity, i.e. they were highly monodisperse.

Example 2—Octreotide-Loaded Microparticles

(37) A particular example of the process of microparticle production described above in Example 1 is the production of octreotide-loaded microspheres (Q-Octreotide™) now described.

(38) Octreotide (also known by the brand name Sandostatin®, Novartis Pharmaceuticals) is an octapeptide that mimics somatostatin pharmacologically. Octreotide has the following chemical structure:

(39) ##STR00001##

(40) Octreotide is used for the treatment of growth hormone producing tumours (acromegaly and gigantism), pituitary tumours that secrete thyroid stimulating hormone (thyrotropinoma), diarrhoea and flushing episodes associated with carcinoid syndrome, and diarrhoea in people with vasoactive intestinal peptide-secreting tumours (VIPomas).

(41) Materials

(42) TABLE-US-00001 Material Use Supplier Anhydrous Solvent for PLGA and octreotide Sigma DMSO acetate Resomer Rate controlling excipient Evonik RG752H Poly(D,L-lactide-co-glycolide) acid terminated, lactide:glycolide 75:25 Octreotide Active PolyPeptide acetate Inc Ultrapure Equipment rinsing, antisolvent, wash Lab water water solutions, lyophilisation media system Tert-Butanol Antisolvent VWR D-Mannitol Wash media and freeze dry excipient Sigma PBS Wash media Sigma CMC Freeze dry excipient Sigma Tween20 Freeze dry excipient Sigma

(43) TABLE-US-00002 Equipment Comments PiezoArray Konica Minolta KM512LH-010532 printhead, Printhead new, cleaned as for leachables and extractables. Pre-flushed with DMSO prior to batch start
Methodology

(44) A master formulation is made up:

(45) Resomer RG752H

(46) Octreotide acetate

(47) DMSO

(48) The active solution is maintained at 12-16° C.

(49) Antisolvent

(50) 15% w/w tertiary butanol.

(51) Dispensing droplets

(52) KM512LH head was run with frequency set to 4 kHz.

(53) Antisolvent flow

(54) 125 mL/min, 2-8° C.

(55) The octreotide-loaded microspheres were collected using a bead harvester (see WO2013/014466), washed, freeze-dried and terminally sterilized (e.g. using gamma ray or E-beam sterilization).

(56) The octreotide-loaded microspheres were determined to be monodisperse and suitable for sustained release pharmaceutical use.

(57) All references cited herein are incorporated herein by reference in their entirety and for all purposes to the same extent as if each individual publication or patent or patent application was specifically and individually indicated to be incorporated by reference in its entirety.

(58) The specific embodiments described herein are offered by way of example, not by way of limitation. Any sub-titles herein are included for convenience only, and are not to be construed as limiting the disclosure in any way.