Abstract:
Disclosed herein is an injector device for delivering an implant, the device including a retracting element, a cannula needle, and a plunger. The device may comprise an latch that, when actuated by a user, causes the retracting element to move the cannula needle away from the delivery site, allowing the plunger to eject the implant into the site. The device may be configured for intraocular drug delivery.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/597,264, filed Feb. 10, 2012, the disclosure of which is incorporated herein by reference thereto. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The human eye is a highly evolved and complex sensory organ. Damage to any of its essential structures can result in impairment of vision. Treatments of various eye conditions and diseases often consist of applying doses of appropriate medications in aqueous suspension solutions or ointments. While such treatments are satisfactory for conditions that require only one or a few applications of the medicinal agents, certain conditions require more frequent doses and such treatments are inconvenient to patients. In contrast, ophthalmic medicinal agents in solid implant forms allow a high weight of drug per administered volume. This is particularly advantageous when a large amount of drug must be administered per dose or when the volume is constrained, as in intraocular injections. Additionally, the solid state also renders the compound less sensitive to solution-mediated chemical degradation. 
         [0003]    Direct injection into a sensitive and delicate structure like the eye has certain challenges and attendant difficulties. There are a number of procedures and devices that have been developed for the controlled injection of an implant into a tissue, such as an eye. However, improved procedures and devices would be beneficial. 
       SUMMARY OF THE INVENTION 
       [0004]    Disclosed herein is an injector device that delivers an implant into a tissue. In certain embodiments, the injector device is fitted with detachable protectors to secure the device during events such as handling and shipping. 
         [0005]    In the present disclosure, the term “proximal” is used to refer to that portion of an element closest to the physician using the device to inject an implant into an injection site. The term “distal” is used herein to refer to that portion of an element farthest from the physician&#39;s hand, and closest to the injection site, when the device is utilized to inject an implant. The term “transverse” is used herein to refer to a plane orthogonal to a longitudinal axis of the injector device. The term “injector” is broadly intended to comprise all types of dispensing apparatus that include a hollow shaft and a retracting element. The injector of the present disclosure is not restricted to medical use, and may be utilized for suitable non-medical applications, such as industrial or home usages. 
         [0006]    In a first aspect of this invention, the invention relates to an injector device including a syringe barrel defining a central axial cavity and a cannula needle defining a central axial cavity, both central axial cavities in communication. An implant to be delivered to a target tissue site is disposed in the central axial cavity of the cannula needle. A retracting element is coaxially coupled to the proximal end of the cannula needle, and is adapted to retract the cannula needle into the syringe barrel. A plunger is fixedly disposed in the central axial cavity of the syringe barrel. The plunger may be held in place within the syringe barrel by one or more anchor elements disposed near the proximal end of the plunger. When the cannula needle retracts via the retracting element, the plunger extends through the central axial cavity of the cannula needle and beyond the distal end of the syringe barrel, delivering the implant to the target tissue site. 
         [0007]    In another aspect of the invention, the injector device described above further includes a latch located on the exterior of the syringe barrel and coupled to the retracting element. When the latch is activated by a physician, the cannula needle retracts, delivering the implant to the target tissue site. The injector device may be equipped with a disengageable latch guard coupled to the latch to prevent activation of the latch while the latch guard is engaged. In some embodiments, the injector device is equipped with one or more protector elements, such as a disengageable block that obstructs the implant from exiting the distal end of the cannula needle during transportation and handling. In some embodiments, the block is a wire having a hook shape, and a first bell-shaped end of the wire caps the distal end of the cannula needle and a second end of the wire is secured to a portion of the injector device. 
         [0008]    A stop may be disposed on the cannula needle, the stop having a portion that extends beyond a cross section of the cannula needle. In some embodiments, the stop includes a tubular collar coaxially positioned with the cannula needle, and a positive cross-sectional area difference between the tubular collar and the needle prevents penetration of the cannula needle into a tissue beyond a pre-determined depth. 
         [0009]    In another aspect of the invention, the invention relates to a method of injecting an implant using an injector device by first providing an injector device as described herein, inserting the cannula needle of the injector device into a tissue, activating the latch to cause the retracting element to retract the cannula needle from around the implant, and removing the device from the tissue while leaving the implant in the tissue. Additionally, the method may include stopping the insertion of the cannula needle into the tissue when a surface of the tissue contacts a stop disposed on the cannula needle, the stop having a portion that extends beyond a cross section of the cannula needle. Prior to inserting the cannula needle of the injector device into a tissue, the method may include disengaging a block from the injector device, wherein the block obstructs the implant from exiting through the distal end of the cannula needle. This method may be used to inject an implant into eye tissue, e.g., through the sclera of an eye. The cannula needle may be a 25-gauge needle, and may have a beveled tip. In some embodiments, the longitudinal length of the implant is between 0.1 and 0.6 centimeters. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a perspective view of an injector device of the present invention. 
           [0011]      FIG. 2  depicts a series of longitudinal cross-sectional views of injector device configurations, wherein  FIG. 2A  depicts an injector device equipped with a set of disengageable protectors coupled thereto,  FIG. 2B  depicts an injector device in an extended configuration with an implant disposed therein, and  FIG. 2C  depicts an injector device in a retracted configuration after delivering the implant to a tissue site. 
           [0012]      FIG. 3  is a perspective view of a syringe barrel of the injector device of  FIG. 2 . 
           [0013]      FIG. 4  is a perspective view of a latch of the injector device of  FIG. 2 . 
           [0014]      FIG. 5  is a perspective view of a retracting element of the injector device of  FIG. 2 . 
           [0015]      FIG. 6  depicts two disengageable block configurations, wherein  FIG. 6A  is a perspective view of a disengageable blocking wire and  FIG. 6B  is a perspective view of a disengageable blocking cap. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The device and method described herein provide an injector device capable of delivering an implant into a tissue. In certain embodiments, the injector device is fitted with disengageable protectors to secure the device during events such as handling and shipping. It will be understood by one of ordinary skill in the art that the device and method described herein can be adapted and modified for other suitable applications and that such other additions and modifications will not depart from the scope hereof. 
         [0017]      FIG. 1  is a perspective view of an injector device of the present invention. The injector comprises a syringe barrel  2  with a central axial cavity  4 . The central axial cavity  4  may have a circular transverse cross-sectional shape, as shown in the current embodiment, although the cross-sectional shape may be square, triangular, polygonal, or any other suitable shape. Coaxially aligned with the syringe barrel  2  are a cannula needle assembly  3 , including a needle hub collar  6  and a cannula needle  8 , and a tubular stop  10  disposed around the cannula needle  8 . A hook-shaped disengageable block  12  has a first end  14  positioned to cap the distal end of cannula needle  8  and a second end  16  anchored to the needle hub collar  6 . A latch  18  is disposed in a slot in the syringe barrel  2 , and protrudes from the exterior of the syringe barrel  2 . A detachable guard  20  extends through a barrel guard aperture  21  in the syringe barrel  2  and into a latch guard aperture  23  ( FIG. 2 ) of the latch  18 . When the guard  20  is positioned within the barrel guard aperture  21  and the latch guard aperture  23 , the latch  18  is prevented from being depressed into the syringe barrel  2 . The exterior of the syringe barrel  2  includes a concave gripping portion  22  adapted to allow the injector device to be comfortably operated in a physician&#39;s hand. The concave gripping portion  22  may be integrally formed from the syringe barrel  2 , as shown, or may be mechanically, chemically or otherwise coupled to the syringe barrel  2 . Any of a variety of shapes may be selected for the concave gripping portion  22  to provide suitable finger placement during injector device handling. A number of anchor elements  24 ,  26  and  28  are mounted on the syringe barrel  2  and extend into the central axial cavity  4 . 
         [0018]      FIG. 2  depicts a series of longitudinal cross-sectional views of injector device configurations.  FIG. 2A  depicts an injector device in an extended configuration, additionally equipped with a set of disengageable protectors coupled thereto, including disengageable block  12  and shield  30 . Shield  30  is a detachable cap that seats securely on the syringe barrel  2  of the injector device to prevent any damage to the cannula needle assembly  3 . The latch  18  is received in a latch slot  36  of the syringe barrel  2 .  FIGS. 3 and 4  are perspective views of the syringe barrel  2  and the latch  18 , respectively. A latch axle (not shown) extends from pivot apertures  5  ( FIG. 3 ) in the syringe barrel  2  and fully or partially through a latch pivot aperture  42  ( FIG. 2A ) so that the latch  18  can pivot about the latch pivot aperture  42 . When the latch  18  is properly disposed in the latch slot  36 , a latch tab  7  ( FIG. 4 ) of the latch  18  is positioned in a complementarily-shaped latch tab notch  9  ( FIG. 3 ) in the syringe barrel  2 . A latch spring  38  ( FIG. 2A ) is mounted in the latch slot  36  between the syringe barrel  2  and the latch  18 . The latch spring  38  is a helical compression spring, with a height of preferably 0.05″-0.15″, and a spring constant of preferably approximately 9 lbs/in. The latch spring  38  may be made of stainless steel or any other suitable spring material. 
         [0019]      FIG. 2B  also depicts an injector device in an extended configuration, but without the disengageable protectors illustrated in  FIG. 2A . In the configuration of  FIGS. 2A and 2B , a channel catch  40  of the latch  18  extends into the central axial cavity  4  of the syringe barrel  2  and is seated in a channel  34  of a retracting element  32 . The retracting element  32  extends longitudinally within the central axial cavity  4 , and is surrounded by a refractor spring  44  along a portion of its length near its proximal end. The proximal end of the retractor spring  44  abuts the contoured proximal end of the retracting element  32 , and the distal end of the refractor spring  44  abuts a shoulder  47  of the inner peripheral surface of the syringe barrel  2 . Thus, the retractor spring  44  is prevented from sliding distally within the central axial cavity  4  when the injector device is in the extended configuration depicted in  FIGS. 2A and 2B . The refractor spring  44  is a helical compression spring, with a height of preferably 0.25″-0.5″, and a spring constant of preferably approximately 1 lbs/in. The retractor spring  44  may be made of stainless steel or any other suitable spring material. 
         [0020]    The refracting element  32  defines a central axial cavity  33 . For example, in the embodiment depicted in  FIG. 5 , the refracting element  32  is a hollow cylindrical rod, preferably made of polycarbonate or another such material, with a central axial cavity  33  and machined contours (such as the channel  34 ), whose shape allows it to fit securely within the central axial cavity  4  of the syringe barrel  2 . The distal end  35  of the retracting element  32  includes an inner portion  37  and an outer portion  39 , configured to coaxially couple to the needle hub collar  6  at the proximal end of the cannula needle assembly  3 . Those of ordinary skill in the art will recognize that a variety of other or additional coupling mechanisms may be used to securely engage the cannula needle assembly  3  to the retracting element  32 , such as chemical bonding. In alternative embodiments, the cannula needle assembly  3  may be integrally formed with the retracting element  32 . 
         [0021]    The cannula needle assembly  3  includes a cannula needle  8  that defines a central axial cavity. The cannula needle  8  may be formed from, for example, between about 18- and 30-gauge tubing (e.g., a 25-gauge needle). The cannula needle  8  may have a beveled tip at its distal end disposed at a pre-determined angular relation to the longitudinal axis of the needle&#39;s central axial cavity. Although the cannula needle  8  preferably has a straight longitudinal profile, other suitable longitudinal needle shapes may be used. The needle  8  may be made of any suitably rigid material such as metal or metal alloys; for example, stainless steel or the like. An implant  45  is adapted to fit in the central axial cavity of the cannula needle  8  from its distal end as depicted in  FIG. 2B . The implant  45  may be of any solid composition, e.g., for releasing a drug or other agent. 
         [0022]    Disposed between the distal end of the needle hub collar  6  and the cannula needle  8  is a stop  10 . A positive transverse cross-sectional area difference between the stop  10  and the cannula needle  8  prevents the needle  8  from penetrating a tissue beyond its longitudinal length that extends longitudinally from the stop  10  to the distal end of the cannula needle  8 . This longitudinal length is defined as a penetration depth of the needle  8 . The stop  10  may be integrally formed with the cannula needle assembly  3  or, in another embodiment, securely coupled to the cannula needle assembly  3 . In the present embodiment, the stop  10  comprises a tubular collar or ring coaxially situated between the distal end of the needle hub collar  6  and the distal end of the cannula needle  8 . Those of skill in the art will recognize that there are a variety of stop configurations suitable for controlling the penetration depth of the cannula needle  8 . A number of exemplary stop configurations are described in Nazarro et al., U.S. Patent Application Publication No. 2008/0071246, incorporated by reference herein in its entirety. In some embodiments, calibration lines may be optionally provided on the cannula needle  8  to visually indicate one or more target penetration depths. 
         [0023]    The injector device also includes a plunger  46  disposed in the central axial cavity  4  defined by the syringe barrel  2 . The plunger  46  includes a plunger base  48 , having a distal end  50  and a proximal end  52 . The plunger&#39;s transverse cross-sectional shape may vary as long as it fits into the central axial cavity  33  of the retracting element  32 . An end-piece  54  at the proximal end  52  may be integrally formed with or securely coupled to the plunger  46 . The end-piece  54  is anchored to the syringe barrel  2  by anchor elements  24 ,  26  and  28 . As illustrated in  FIG. 2 , the end-piece  54  has a “T” shape in profile view, and the three anchoring elements  24 ,  26  and  28  are disposed within the central axial cavity  4  so as to secure the end-piece  54  at a fixed location and prevent the end-piece  54  from moving longitudinally within the syringe barrel  2 . In different embodiments, the shape of the end-piece  54  and the arrangement of one or more anchoring elements may vary as long as the plunger  46  is secured within the syringe barrel  2 . The plunger  46  is preferably positioned to not extend beyond the proximal end of the injector device when the device is in an extended configuration. 
         [0024]    The plunger  46  also includes a plunger rod  56 , having a proximal end coupled to a distal end of the plunger base  48 . The plunger rod  56  is positioned within the cannula needle  8  and adapted to eject the embedded implant  45  when the retracting element  32  retracts into the syringe barrel  2 . More particularly, the plunger  46  is configured such that the distal end of the plunger rod  56  is close to or beyond the distal end of the cannula needle  8  when the retracting element  32  has retracted into the syringe barrel  2  (as discussed below with reference to  FIG. 2C ). 
         [0025]    When the injector device is in the extended configuration illustrated in  FIG. 2B , the latch spring  38  is under compression and exerts an upward force on the distal end of latch  18 . Because the latch  18  is pivotally coupled to the syringe barrel  2  about the latch pivot aperture  42 , this upward force presses the channel catch  40  into the channel  34  of the refracting element  32 . At the same time, the refractor spring  44  is under compression, and applies a leftward force to the retracting element  32 . While the channel catch  40  is seated in the channel  34 , the retracting element cannot move with respect to the syringe barrel  2 . However, if the guard  20  ( FIG. 2 ) is removed, and a sufficient downward force is applied to the distal end of the latch  18  (e.g., at the tactile ridges  59  illustrated in  FIG. 4 ), the upward force exerted by the latch spring  38  is overcome. As a result, the channel catch  40  is disengaged from the channel  34  and the retracting element  32  is pulled leftward by the expansion of the retractor spring  44 . As the retracting element  32  moves leftward, the cannula needle assembly  3  retracts partially into the central axial cavity  4  of the syringe barrel  2 , as shown in  FIG. 2C . The plunger  46  remains in a fixed position relative to the syringe barrel  2  as the retracting element  32  and the cannula needle assembly  3  retract proximally, leaving the distal end of the plunger rod  56  and the implant  45  at the tissue site. 
         [0026]    The syringe barrel  2 , the concave gripping portion  22 , the plunger base  48 , the plunger rod  56 , the retracting element  32  and the latch  18  can be prepared from hard plastic, glass, stainless steel or other suitably durable materials that may be transparent, translucent, opaque, or non-opaque. All the aforementioned pieces may have the same or different material compositions. For example, the concave gripping portion  22  may or may not be made of the same material as the syringe barrel  2  and the plunger base  48  may or may not have the same material composition as the plunger rod  56 . The plunger rod  56  is made of a suitably rigid material, such as stainless steel or hard plastic, so that it can eject an implant  45  from the cannula needle  8  when the retracting element  32  retracts. The latch  18  and syringe barrel  2  are preferably made from ABS plastic. All the above pieces can be prepared from heat- or irradiation-stable materials for reuse or prepared as disposables for single-use applications. 
         [0027]    The plunger  46  assumes a shape that allows it to fit securely within the central axial cavity  33  of the retracting element  32 . In contrast to plungers utilized in syringes for the injection of liquid, the plunger  46  of the present invention does not need to form an air-tight seal with the inner peripheral surface of the retracting element  32 , and in fact, may define passages that permit the free movement of air during use. Similarly, the retracting element  32  need not form an air-tight seal with the inner peripheral surface of the syringe barrel  2 . 
         [0028]    In certain embodiments, a disengageable block  12 , which may be made of a suitably rigid material such as stainless steel, hard plastic, or the like, may be utilized to reversibly obstruct the implant  45  from exiting the cannula needle  8  from its distal end as shown in  FIG. 2A .  FIG. 6  depicts two disengageable block configurations, wherein  FIG. 6A  is a perspective view of a disengageable blocking wire  62  and  FIG. 6B  is a perspective view of a disengageable blocking cap  68 . The disengageable blocking wire  62  is a hook-shaped element with a first end  64  secured to a portion of the injector device and a second end  66  configured to penetrate the distal end of the cannula needle  8  when the blocking wire  62  is engaged with the injector device. The first end  64  is secured to the injector device by, e.g., a securing member, such as a tubular ring, disposed around a periphery of a portion of the injector device, such as around the needle hub collar  6 . The disengageable blocking cap  68  is also a hook-shaped element with a first end  70  secured to a portion of the injector device, but with a second end  72  configured in a bell or cone or similar shape to surround and protect the distal end of the cannula needle  8  when the blocking cap  68  is engaged with the injector device. The disengageable block may be made of any malleable material such as rubber, synthetic rubber, soft plastic, metal, or the like. Additional examples of disengageable blocks that may be used with the present invention are described in Nazarro et al., U.S. Patent Application Publication No. 2008/0071246, incorporated by reference herein in its entirety. 
         [0029]    The injector device described above can be prepared by any suitable method, and the various parts assembled in any suitable order. A preferred assembly method includes mounting the latch spring  38  within the latch slot  36  as shown in  FIG. 2 , and attaching the latch  18  to the syringe barrel  2  by placing the latch  18  into the latch slot  36  and engaging the latch axle in the latch pivot  42 . The latch spring  38  is seated in a notch of the latch  18  as shown in  FIG. 2 . Next, a retractor/spring subassembly is assembled by inserting the distal end of the retracting element  32  into the axial cavity of the retractor spring  44  and sliding the retractor spring  44  toward the proximal end of the retracting element  32 . The distal end of the retractor/spring subassembly is then inserted into the proximal end of the central axial cavity  4  of the syringe barrel  2 . A rightward force is applied to the proximal end of the retracting element  32  to compress the retractor spring  44  until the channel catch  40  of the latch  18  falls into the channel  34  of the retracting element  32 . In this position, the refracting element  32  is latched in place, and the latch guard  20  ( FIG. 1 ) is inserted into the barrel guard aperture  21  ( FIG. 1 ) until it extends through the latch guard aperture  23  in the latch  18  ( FIG. 2 ). With the latch guard  20  in place, the latch  18  cannot be accidentally actuated during the remaining assembly process. Next, the anchoring elements  26  and  28  are mounted within the central axial cavity  4 , and the distal end of the plunger  46  is inserted into the syringe barrel  2 . The plunger  46  is positioned between the anchoring elements  26  and  28 , and within the central axial cavity  33  of the retracting element  32 . The remaining anchoring element  24  is mounted to the syringe barrel  2 , locking the end-piece  54  of the plunger  46  in place within the central axial cavity  33 . Next, at the distal end of the injector device, the distal end of the plunger rod  56  is fitted into the proximal end of the cannula needle assembly  3  and guided into the cannula needle  8 . The cannula needle assembly  3  is then coupled to the retracting element  32  as shown in  FIG. 2 , followed by disposing the implant  45  in the cannula needle  8 . The stop  10  can be coupled to the cannula needle  8  after the cannula needle assembly  3  is coupled to the retracting element  32 , or as part of the cannula needle assembly process. Optionally, the above method may include fitting the protecting elements such as the disengageable block  12  and the shield  30 , optionally fitting one end of the hook-shaped block  12  to the distal end of the cannula needle  8  and securing a second end of the block  12  to the needle hub collar  6  of the cannula needle assembly  3 . 
         [0030]    The injector device may be employed by first removing the shield  30 , the block  12  and the latch guard  20  if they are present, inserting the cannula needle  8  into a tissue to a depth where the stop  10  contacts the surface of the tissue, then depressing the latch  18  into the syringe barrel  2  to cause the retracting element  32  to retract into the syringe barrel  2  and leave the implant  45  into the tissue site. 
         [0031]    In one embodiment of the injector device, the device is designed to deliver a drug to an eye  58  ( FIG. 2 ). In particular, the cannula needle  8  of the injector device is adapted to penetrate a sclera of the eye  58 . The cannula needle  8  may be a straight 25-gauge cannula needle and have, for example, a beveled tip at its distal end, e.g., disposed at an angle of about between 10 and 13 degrees, preferably about 11.5 degrees, in relation to the longitudinal axis of the needle&#39;s central axial cavity. The stop  10  of the depicted device comprises a tubular collar that is coaxially coupled to the cannula needle assembly  3 , wherein the cannula needle  8  is disposed and situated in such a manner that its penetration depth  507  is about 0.25 to 0.35 cm. The implant  45  may have a longitudinal length of about 0.1 to 0.9 cm. 
         [0032]    Thus, the invention generally provides an injector device with a retracting element for delivering an implant to a tissue site. The purpose of the above description and examples is to illustrate some non-limiting embodiments of the present invention. It will be apparent to those skilled in the art that various modifications and variations may be made to the device and method of the present invention without departing from the spirit or scope of the invention. All publications and patents cited herein are hereby incorporated by reference in their entirety.