PARTICLE DELIVERY

[0001] In our earlier WO94/24263, we disclose a non-invasive drug delivery system involving the use of a needleless syringe which fires particles of a therapeutic agent in controlled doses into body tissue, e.g. through the intact skin, or delivers genetic material into living cells. The syringe described in the earlier application is constructed as an elongate tubular nozzle, a rupturable membrane initially closing the passage through the nozzle adjacent to the upstream end of the nozzle, particles of a therapeutic agent located adjacent to the membrane, and energising means for applying to the upstream side of the membrane a gaseous pressure sufficient to burst the membrane and produce through the nozzle a supersonic gas flow in which the particles are entrained.

[0002] As explained in the earlier specification, the particles of the therapeutic agent may be carrier particles coated, for example, with genetic material, or may be powdered drugs for all kinds of therapeutic use. similarly the earlier specification explains the parameters of particle size (preferably 10-40 m) density (preferably 0.5-2.0 g/cm³), and velocity (preferably 200-2500 m/sec), and momentum density (preferably 4-7 kg/sec/m), which have been found to be appropriate for adequate target penetration. These parameters are unchanged but we have now devised a modification of the particle delivery system.

[0003] According to the present invention, a needleless syringe comprises a body containing a lumen, an upstream end of which is, or is arranged to be, connected to a source of gaseous pressure which can suddenly be released into the lumen; the downstream end of the lumen terminating behind a bistable diaphragm which is movable between an inverted position in which it presents outwardly of the body a concavity for containing particles of a therapeutic agent, and an everted, outwardly convex, position; the arrangement being such that, in use, when gas under pressure is released into the lumen, the diaphragm will snap over from its inverted to its everted position and catapult the particles outwardly.

[0004] This new construction has an advantage that even when, as will be usual, a gaseous supersonic shockwave will be necessary to snap the diaphragm over from its inverted to its everted position, the diaphragm will contain the gas within the lumen so that no provision has to be made for dissipating and silencing any shockwave reflected from the target. Also the target tissue is not subjected to any possibility of harm from the high speed gas flow.

[0005] As disclosed in the earlier specification, the release of the pressurized gas may be achieved by building up pressure behind a rupturable membrane until the pressure difference across the membrane is sufficient to rupture the membrane and release the gas suddenly into the lumen. Alternatively the syringe may incorporate a reservoir of compressed gas having a valve which can be opened suddenly to release the gas into the lumen. In both cases, the velocity of the shockwave is increased if the gas is lighter than air, e.g. helium. This effect is enhanced if the lumen is also initially filled with a gas, which is lighter than air, e.g. helium.

[0006] In order to avoid loss of particles prior to delivery and to maintain sterility of the particles, the concavity is preferably covered by, for example, a retractable shield or a thin barrier film which is readily penetrated by the particles upon ejection.

[0007] The syringe may be constructed for the transdermal delivery of drugs into the body, in which case the lumen may be provided by the passageway through a tubular nozzle, the diaphragm being provided adjacent to the downstream end of the nozzle and facing substantially in the axial direction of the nozzle. Alternatively, the invention may be used in conjunction with a catheter, such as an arterial catheter, in which case the diaphragm may be provided in a sidewall of the catheter body so that upon eversion, the particles are propelled laterally from the body. This would find use in vascular proliferative diseases for delivering genetic material into the wall of the expanded stenotic blood vessel, to transform genetically the endothelial cells lining the wall of the blood vessel with the aim of preventing subsequent restenosis/re-occlusion of the blood vessel.

[0008] Moreover, the development of a catheter-based delivery system may find other uses, as for localised delivery of a combination of compounds (eg for chemotherapy) into specific internal organs and for the local organ-based hormone replacement. The catheter device would also be useful in the administration of drugs or DNA to accessible surfaces for medical purposes (eg for the treatment of tumours of mucosal surfaces, such as respiratory, gastrointestinal or genito-urinary tracts).

[0009] The invention is illustrated by way of example in the accompanying drawings.

[0010] Figures how a syringe for transdermal delivery of particles of therapeutic agent. Thus as particularly shown in FIG. 1 the syringe has a cylindrical reservoir initially containing helium under a pressure of about 80 bar. This is screwed and sealed to a first tubular body portion 11 containing a rupture chamber 12. The body portion 11 is screwed and sealed to a second tubular body portion 13 containing a passageway 14. In turn the body portion 13 is screwed and sealed to a third tubular body portion 17 containing a passageway 18, and a tubular tip portion 19 is screwed to the bottom of the body portion 17.

[0011] With this construction the reservoir 10 can be stored separately and fitted to the rest of the syringe immediately prior to use. The body portions 11 and 13 are separable to allow the sandwiching between them of a rupturable membrane 20. The tip portion 19 is separable from the body portion 17 to allow the sandwiching between them of an invertible bistable diaphragm 21 which is shaped in the form of a dome from a stiff and strong, but resilient, material such as Mylar by thermoforming in a suitable jig. The body portions 13 and 17 are separable so that the parts 17, 19 and 21 can be provided as a disposable unit.

[0012] Particles of therapeutic agent will initially be provided in the concavity at the externally facing surface of the diaphragm 21. The particles may be attached by electrostatic forces, by their natural sticky nature, or by the evaporation of ethanol in which the particles have been suspended. Preferably, however, and for reasons of sterility, the diaphragm 21 is covered and sealed at its edge to a weak barrier film 22 to form a sealed capsule containing the particles 23, as shown in FIG. 3. The weak barrier film 22 may be cut or scored to assist rupture and reduce membrane fragmentation.

[0013] In use with the syringe assembled and with the lumen 14, 18 prefilled with helium at approximately atmospheric pressure, the tip is placed in proximity to, or in contact with, the skin to be treated and a plunger 24 is depressed to open a valve 25 and allow the helium to be discharged into the rupture chamber 12. This valve 25 may preferably be arranged such that the frontal area of the plunger is greater at the downstream exit to the cylindrical reservoir when compared with the upstream frontal area of the plunger, resulting in a self-opening (and quick-opening) valve. When the pressure in the chamber 12 has reached a sufficient value of, for example, about 23 bar, the membrane 20 bursts, releasing a shockwave which propagates through a lumen, i.e. a nozzle, formed by the passageways 14 and 18, and causes the diaphragm 21 suddenly to evert into a downwardly, outwardly convex, configuration. This propels the particles 23 rapidly forward out of the syringe with simultaneous rupture of the barrier film 22.

[0014] As suggested in FIG. 3, a short tubular spacer 26 may be provided to reduce the velocity of the particles before impact and to enable the particles to become more spread out in order to increase the target area of skin.

[0015] FIGS. 4 to 7 show the application of the invention to an arterial catheter for use in vascular proliferative disorders.

[0016] FIG. 5 shows the whole catheter, provided at its upstream end with a reservoir 10, valve 25, rupture chamber 12 and rupturable membrane 20, similar to those of the first example. The catheter may be a triple lumen catheter, one lumen for the usual guidewire, the second to carry gas to inflate a positional balloon 27 for urging a body 28 adjacent to the leading end (shown in FIG. 4) of the catheter against a wall of an artery 29, and the third for propagating a shockwave to the tip of the catheter.

[0017] At an opening 31 in a sidewall of the catheter body 28, there is provided a bistable diaphragm 32. In a position shown in FIG. 4 and in full lines in FIG. 6, the diaphragm presents a laterally outwardly facing concavity in which particles of therapeutic agent, such as particles 33, e.g. containing or consisting of DNA, are located. In order to avoid the particles being washed out of the concavity by means of the blood flow in the artery the cavity may initially be covered by a barrier film or by a retractable sleeve 35 as shown in FIG. 7.

[0018] The catheter is used analogously to the syringe of FIGS. 1 to 3. Thus release of helium from the reservoir 10 into the rupture chamber 12 eventually bursts the membrane 20 and causes a shockwave to be propagated along the lumen 30 causing the diaphragm 32 to evert suddenly to the dotted line position shown in FIG. 6 and hence to propel the particles 33 outwardly, after retraction of the sleeve 35 or through the barrier film, into the wall of the artery 29.

[0019] Contrary to what is shown in FIG. 6, it may be desirable for the diaphragm 32 to be within the peripheral envelope of the catheter body, not only when in its inverted position in order to avoid interference during insertion of the catheter, but also when in its everted position to avoid potentially damaging impact with the arterial wall.