Subassembly for a drug delivery device and corresponding assembly method - Patents.com

Abstract

A subassembly for a drug delivery device (10), the subassembly comprising a housing (30) and a rear cap (50) coaxially disposed within the housing (30), the housing (30) being tubular and extending axially along a longitudinal axis (12) from a proximal end to a distal end, the housing (30) comprising an inner surface (34) and an outer surface (32), the inner surface (34) of the housing (30) facing distally. The housing (30) includes a first surface (36) facing in a proximal direction and a second surface (38) facing in a distal direction, the second surface (38) being closer to the distal end of the housing (30) than the first surface (36), the rear cap (50) extends along the longitudinal axis (12) from the proximal end to the distal end, the rear cap (50) includes a flexible arm (52) having a proximally facing first surface (54), and the rear cap (50) includes a flexible arm (52) having a proximally facing first surface (54). and a second surface (55) facing in a proximal direction, the second surface (55) of the rear cap (50) being closer to the distal end of the rear cap (50) than the first surface (54) of the rear cap (50), an axial distance (L1) between the first surface (36) of the housing (30) and the second surface (38) of the housing (30) being less than the axial distance (L2) between the first surface (54) of the rear cap (50) and the second surface (55) of the rear cap (50), such that when the rear cap (50) is inserted into the distal end of the housing (30) during assembly, the first surface (54) of the rear cap (50) engages the first surface (36) of the housing (30), thereby bending the flexible arm (52) before the second surface (55) of the rear cap (50) engages the second surface (38) of the housing (30).

Description

[Technical field]

[0001] The present invention relates to a subassembly for a medication delivery device, and in particular to a subassembly comprising a housing and a rear cap. [Background technology]

[0002] Patent applications WO 2016 / 169748 and WO 02021 / 204499 show a drug delivery device comprising a rear cap and a housing. The applicant recognises that further improvements can be made to the design of the rear cap and the housing. Summary of the Invention

[0003] Reference should now be made to the appended claims.

[0004] In this disclosure, when the term "distal direction" is used, it refers to the direction away from the dose delivery site during use of the drug delivery device. When the term "distal part / end" is used, it refers to the part / end of the delivery device, or the part / end of a member thereof, that is located the furthest from the dose delivery site during use of the drug delivery device. Correspondingly, when the term "proximal direction" is used, it refers to the direction towards the dose delivery site during use of the drug delivery device. When the term "proximal part / end" is used, it refers to the part / end of the delivery device, or the part / end of a member thereof, that is located the closest from the dose delivery site during use of the drug delivery device.

[0005] Additionally, the terms "longitudinal," "longitudinally," "axially," and "axial" refer to a direction extending along a device or component thereof from a proximal end to a distal end, typically in the direction of the greatest extension of the device and / or component.

[0006] Similarly, the terms "transverse," "transversal," and "transversally" refer to a direction generally perpendicular to the longitudinal direction.

[0007] One aspect relates to a subassembly for a medication delivery device, the subassembly comprising: a housing; and a rear cap coaxially disposed within the housing, the housing being tubular and extending axially along a longitudinal axis from a proximal end to a distal end, the housing comprising an inner surface and an outer surface, the inner surface of the housing comprising a first distally facing surface and a second distally facing surface, the second surface being closer to the distal end of the housing than the first surface, the rear cap extending along the longitudinal axis from the proximal end to the distal end, the rear cap comprising a flexible arm, the flexible arm having a first proximally facing surface and a second distally facing surface, the second surface being closer to the distal end of the housing than the first surface, and the rear cap has a second surface facing in a proximal direction, the second surface of the rear cap being closer to the distal end of the rear cap than the first surface of the rear cap, and an axial distance between the first surface of the housing and the second surface of the housing is less than an axial distance between the first surface of the rear cap and the second surface of the rear cap, such that when the rear cap is inserted into the distal end of the housing during assembly, the first surface of the rear cap engages the first surface of the housing, thereby bending the flexible arm before the second surface of the rear cap engages the second surface of the housing. This structure allows the transportation lock to be maintained even after the rear cap has begun to be inserted into the housing, since the flexible arm can maintain the transportation lock longer than existing designs. This structure allows for a design in which the period during which the power pack is unlocked during assembly is reduced or eliminated.

[0008] Optionally, the subassembly comprises a power pack, the power pack comprising a rear cap, the subassembly configured such that bending of a flexible arm of the rear cap during insertion of the rear cap into the housing unlocks the power pack.

[0009] Optionally, the subassembly is configured such that when the first surface of the rear cap engages the first surface of the housing, the flexible arm bends perpendicular to the longitudinal axis.

[0010] Optionally, the power pack comprises a rotor, and bending the flexible arm disengages a rotation lock between the rear cap and the rotor.

[0011] Optionally, the subassembly comprises a drug delivery member guard, the rotor comprising a groove, the drug delivery member guard comprising a protrusion configured to engage the groove and thereby rotationally lock the rotor.

[0012] Optionally, the inner surface of the housing comprises a first portion at a first distance from the longitudinal axis, a second portion at a second distance from the longitudinal axis, and an intermediate portion extending from the first portion to the second portion, the intermediate portion comprising the first surface. Optionally, the second surface of the housing is at a distal end of the second portion.

[0013] Optionally, when in an unflexed state, the flexible arm is closer to the longitudinal axis than the second portion of the inner surface of the housing.

[0014] Optionally, at least one of the first surface of the rear cap and the first surface of the housing is angled relative to the longitudinal axis. Optionally, the first surface of the housing is angled toward the longitudinal axis. Optionally, the second surface of the housing and / or the second surface of the rear cap extends perpendicular to the longitudinal axis. Optionally, the second surface of the housing is at a distal end of the housing.

[0015] An aspect relates to a drug delivery device comprising a subassembly according to any one of the preceding claims.Optionally, the drug delivery device is an automatic injection device.

[0016] One aspect relates to a kit of parts comprising any of the housings as described above and any of the rear caps as described above.

[0017] One aspect is a method of assembling a subassembly of a drug delivery device, the method comprising, in the following order: providing any housing as described above and any rear cap as described above, partially inserting the rear cap into a distal end of the housing, and pushing the rear cap proximally relative to the housing such that a first surface of the rear cap engages a first surface of the housing before a second surface of the rear cap engages a second surface of the housing, thereby bending the flexible arms. Optionally, the subassembly comprises a drug delivery member guard and a power pack, the power pack comprising a rear cap and a rotor, and a rotational lock between the rear cap and the rotor is released only after a rotational lock between the rotor and the drug delivery member guard is achieved.

[0018] In general, all terms used in the claims should be interpreted according to their ordinary meaning in the art, unless expressly specified otherwise herein. All references to elements, devices, members, components, means, etc. should be openly interpreted as referring to at least one instance of the element, device, member, component, means, etc., unless expressly specified otherwise. [Brief description of the drawings]

[0019] Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0020] [Figure 1] FIG. 2 is a partial perspective side view of a distal portion of the automatic injection device during assembly. [Diagram 2] 2 is a side cross-sectional view of the automatic injection device of FIG. 1 at the same assembly point as FIG. 1. [Diagram 3] FIG. 2 is a perspective view of a portion of the automatic injection device of FIG. 1. [Figure 4]2 shows a side cross-sectional view of the automatic injection device of FIG. 1 during assembly. [Diagram 5] 2 shows a cross-sectional side view of the assembled automatic injection device of FIG. 1. [Figure 6] 2 is a perspective view of the power pack, needle guard, and housing components of the automatic injection device of FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] FIG. 1 shows a portion of an automatic injection device 10 during assembly. The automatic injection device extends in an axial direction 13 along an axis 12. The automatic injection device includes a subassembly comprising a housing 30 and a rear cap 50. The rear cap 50 is coaxially disposed within the housing. The housing 30 is tubular and extends axially along a longitudinal axis from a proximal end to a distal end, the housing 30 comprising an outer surface 32 and an inner surface 34. In this example, the inner surface 34 comprises a first portion 35 at a first distance from the longitudinal axis, a second portion 37 at a second distance from the longitudinal axis, and an intermediate portion 36 (the first surface of the housing) extending from the first portion to the second portion. The second portion 37 is closer to the distal end of the tube than the first portion 35. The intermediate portion 36 comprises the first surface of the housing, which also comprises a second surface 38. Both the first surface of the housing and the second surface of the housing face the distal end of the tube.

[0022] The rear cap 50 extends from a proximal end to a distal end, the rear cap comprising a flexible arm 52. The flexible arm 52 comprises a first surface 54 that faces toward the proximal end of the rear cap 50. The rear cap 50 includes a second surface 55 that faces toward the proximal end of the rear cap. The second surface 55 of the rear cap 50 is closer to the distal end of the rear cap than the first surface 54 of the rear cap.

[0023] As described in more detail below, the axial distance L1 between the first surface of the housing and the second surface of the housing is less than the axial distance L2 between the first surface of the rear cap and the second surface of the rear cap (see FIG. 2 ) such that when the rear cap is inserted into the distal end of the housing during assembly, the first surface of the rear cap engages the first surface of the housing, thereby bending the flexible arm before the second surface of the rear cap engages the second surface of the housing.

[0024] During assembly, the rear cap 50 is inserted into the distal end of the housing 30 to a distal position relative to the housing 30, as shown in FIG. 4. In the distal position shown in FIG. 4, the first surface of the rear cap and the first surface of the housing are in contact with one another and the second surface of the rear cap and the second surface of the housing are spaced apart. The rear cap 50 is then pushed further in a proximal direction relative to the housing resulting in the proximal position shown in FIG. 5. In the proximal position shown in FIG. 5, the second surface of the rear cap and the second surface of the housing are in contact with one another. The first surface of the rear cap and the first surface of the housing are spaced apart.

[0025] The rear cap 50 is typically part of the power pack of the automatic injection device, and the housing is typically part of the front assembly of the automatic injection device. For context, various other parts of an exemplary power pack are shown in the figure, including a plunger rod 75, a drug delivery spring 76 for pushing the plunger rod proximally to release the drug, a guide rod 77 inside the spring 76, and a U-shaped bracket 78 for providing feedback (such as an end click) to indicate the progress of drug delivery. All of these features are optional and can be modified or removed depending on the power pack design. In this example, the spring 76 is used to provide the force required to release the drug, but another power source such as a battery or compressed gas can be used instead. Similarly, a drug delivery member guard (needle guard) 90 (typically part of the front assembly) and a rotor 80 (typically part of the power pack) are shown, which can be used to activate the automatic injection device, but these are also optional and can be replaced with an alternative mechanism, such as a button to activate the power source used for drug delivery.

[0026] The structure of the housing and rear cap allows for the provision of a transport lock (e.g., a rotation lock). The exact nature of the transport lock can vary, but an example is shown in the figures and briefly described. For a more detailed description of the structure of an exemplary power pack, see WO 2011 / 123024, which is incorporated herein by reference. In the example of the present application, the drug delivery spring 76 is stopped from pushing the plunger rod 75 proximally (thereby releasing the drug) by the second arm of the rear cap 50. The second arm is prevented from releasing the plunger rod 75 by the rotor 80. Once the rotor 80 has rotated, the second arm is no longer blocked by the rotor 80 and the second arm can move to release the plunger rod. The rotor 80 can be rotated by axial movement of the needle guard 90. To avoid premature unlocking of the power pack, it is beneficial that the rotor cannot be accidentally rotated prematurely into the unlocked position. As a result, it is beneficial to rotationally lock the rotor. This can, for example, allow the power pack to be transported in a locked state, which can reduce the risk of accidental activation during assembly.

[0027] For context, FIG. 6 shows an example of power pack components along with a drug delivery member shield and housing for a drug delivery device (in this case an automatic injection device, but the concepts described herein can be used for other drug delivery devices) that includes the subassembly described herein. Visible are the housing 30, rear cap 50, drug delivery spring 76, guide rod 77, U-shaped bracket 78 and rotor 80, as well as a needle guard 90. The needle guard 90 comprises a base 92 and two arms 94, each arm comprising an inward projection 95 that can engage a labyrinth 84 on the rotor 80. In the illustrated example, the housing 30 is the outer housing of the drug delivery device, but the housing may alternatively be internal to the drug delivery device rather than providing an outer housing. The particular shape of the rotor 80 (and thus of the recess 82 and labyrinth 84) can be varied depending, for example, on the shape of the flexible arms 52 and the shape of the needle guard 90. Similarly, the needle guard 90 (and thus the base 92, arms 94, and inward projections 95) may vary depending on, for example, the shape of the housing 30 and rotor 80. The needle guard 90 may have one, three, or more arms 94 rather than the two arms shown.

[0028] In the illustrated example, the power pack lock is provided by a combination of the flexible arm 52 and a recess 82 in the rotor into which the flexible arm 52 extends (see FIG. 3). Specifically, a portion of the flexible arm extends into the rotor recess 82 (in the illustrated example, it is an axially extending protrusion of the flexible arm at the proximal end of the flexible arm that extends into the recess 82, but this may alternatively be a different portion of the flexible arm and may be spaced from the proximal end of the flexible arm). When the power pack including the rear cap and rotor is inserted into the housing (i.e., moving the components from the position of FIG. 1 to the position of FIG. 4), the power pack lock remains in place. Only when the flexible arm 52 is pushed inward, as shown in FIG. 5, is the power pack lock (the engagement between the flexible arm 52 and the recess 82) unlocked. By this point, the needle guard 90 and rotor 80 are engaged (specifically, labyrinth 84 and inward projection 95) so that by the time the power pack lock is released, a portion of the arm 94 of the needle guard 90 (specifically, inward projection 95) engages a groove on the rotor (the groove is part of labyrinth 84) restricting the rotor from rotating relative to the needle guard and therefore also relative to the housing, as the needle guard is rotationally locked relative to the housing. This can reduce (in this case, eliminate) the time during this assembly step when the power pack is unlocked. With this design, there is never a point at which the rotor is free to move relative to the rear cap, as it is restricted from rotation by the power pack lock (flexible arm 52 and recess 82) or by the needle guard 90.

[0029] As noted above, this particular power pack structure is not required and can be modified. For example, a button mechanism can be provided as an activation mechanism for the drug delivery device, similar to or instead of the needle guard and rotor combination described above, or a different power source (e.g., compressed gas or battery) can be provided. In each of these cases, the housing and rear cap combination as described herein can be used to limit or completely eliminate the time spent during assembly during which the power pack can be activated by providing an arm 52 that is moved aside only when the rear cap is at least partially inside the housing, in order to unlock the power pack later in the assembly process.

[0030] In the illustrated example, the flexible arm is pushed towards the axis by interaction between a first surface of the rear cap and a first surface of the housing. Alternatively, the flexible arm may be pushed in a different direction, for example, circumferentially or axially. In general, the flexible arm only needs to be moved relative to another part of the rear cap (and thus relative to another part of the power pack, such as the rotor in the illustrated example) to remove the power pack lock, and the structure of the lock is modified accordingly. Thus, in the illustrated example, the lock is between the flexible arm of the rear cap and the rotor, but the lock may alternatively be between the rear cap and another component of the power pack, particularly in power packs that do not include a rotor.

[0031] In the illustrated example, the flexible arm, when in an unflexed state, is closer to the axis than the second portion of the inner surface of the housing, and although this is not required (as the second surface 38 can push the flexible arm 52 partially inward to reach the position of FIG. 4), it can minimize the force required to place the rear cap in the position shown in FIG. 4 (where the flexible arm and the first surface of the housing are in contact).

[0032] In the illustrated example, the housing is cylindrical with a circular cross section, although different shapes can be used. In the illustrated example, the first portion 35, the intermediate portion 36, and the second portion 37 are described as part of the inner surface 34 of the housing 30. In this example, the first portion 35 and the second portion 37 are cylindrical, and the intermediate portion 36 is frusto-conical. This can be beneficial as the provision of rotational symmetry means that rotational alignment of the power pack (specifically the rear cap) and the housing during assembly is not required to disengage the power pack lock. Alternatively, the first portion 35, the intermediate portion 36, and / or the second portion 37 can extend only part of the way around the axis. A plurality of the first portion 35, the intermediate portion 36, and / or the second portion 37 can be provided, for example two of each, aligned with the two flexible arms 52 in the illustrated example. Optionally, first portion 35 and second portion 37 are cylindrical, and although surfaces of different shapes could be used instead, cylindrical surfaces may have the advantage of efficiently minimizing volume usage.

[0033] Generally, the intermediate portion 36 provides a surface facing in a distal direction, which allows the flexible arm to be deflected during assembly. In practice, the intermediate portion 36 is angled toward the surface, the angle being the angle of the intermediate portion 36 with respect to the axis 12 when viewed in a longitudinal cross section (e.g., as shown in FIG. 2). The angle may be, for example, between 15 and 90 degrees, more specifically between 30 and 75 degrees. If a 90 degree angle (i.e., perpendicular to the axis 12) is used, the corresponding surface of the flexible arm must be angled with respect to the axis 12. For angled surfaces (i.e., not 90 degrees), the surface of the intermediate portion 36 faces both distally and toward the axis. Generally, the surface of the intermediate portion 36 is not parallel to the axis 12. Optionally, the angle of the intermediate portion 36 and the angle of the surface 54 of the flexible arm 52 are the same.

[0034] Generally, the flexible arm has a surface 54 facing in a proximal direction. The surface of the flexible arm engages with the intermediate portion 36 during assembly. The surface of the flexible arm may be perpendicular to the axis 12 or may be at an angle to the axis. The angle may be, for example, between 15 and 90 degrees, more specifically between 30 and 75 degrees. If a 90 degree angle (i.e. perpendicular to the axis 12) is used, the corresponding surface of the intermediate portion 36 must be angled to the axis 12. With an angled surface (i.e. not 90 degrees), the surface of the flexible arm faces both distally and away from the axis. Generally, the surface of the flexible arm 52 is not parallel to the axis 12. The rear cap in the example shown has two flexible arms. Alternatively, one, three or more flexible arms 52 may be provided.

[0035] In examples where the flexible arm bends in a direction other than radial to the axis (e.g., circumferential to the axis) as in the illustrated example, the intermediate portion 36 and surface 54 of the flexible arm 52 may be angled accordingly and do not necessarily face toward / away from the axis.

[0036] In the illustrated example, the second surface 38 of the housing 30 and the second surface 55 of the rear cap 50 are both perpendicular to the axis. However, alternative angles of the second surface 38 of the housing 30 and the second surface 55 of the rear cap 50 are possible, as are the intermediate portion 36 and the first surface 54, and in addition, the second surface of the housing can face away from the axis 12 (and correspondingly, the second surface of the rear cap can face towards the axis 12). The second surface 38 of the housing 30 and the second surface 55 of the rear cap 50 are optional, but may be useful to establish a fixed axial position of the housing relative to the rear cap in the completed drug delivery device. The second surface 38 of the housing is at the distal end of the housing in the illustrated example, but may alternatively be axially spaced from the distal end of the housing.

[0037] The delivery devices described herein can be used for the treatment and / or prevention of one or more of many different types of disorders. Exemplary disorders include, but are not limited to, rheumatoid arthritis, inflammatory bowel disease (e.g., Crohn's disease and ulcerative colitis), hypercholesterolemia, diabetes (e.g., type 2 diabetes), psoriasis, migraines, multiple sclerosis, anemia, lupus, atopic dermatitis, asthma, nasal polyps, acute hypoglycemia, obesity, anaphylaxis, and allergies. Exemplary types of drugs that can be included in the delivery devices described herein include, but are not limited to, antibodies, proteins, fusion proteins, peptibodies, polypeptides, pegylated proteins, protein fragments, protein analogs, protein variants, protein precursors, and / or protein derivatives. Exemplary drugs that may be included in the delivery devices described herein include, but are not limited to, the following (with non-limiting examples of associated disorders in parentheses): etanercept (rheumatoid arthritis, inflammatory bowel disease (e.g., Crohn's disease and ulcerative colitis)), evolocumab (hypercholesterolemia), exenatide (type 2 diabetes), secukinumab (psoriasis), erenumab (migraines), alirocumab (rheumatoid arthritis), methotrexate (amethopterin) (rheumatoid arthritis), tocilizumab (rheumatoid arthritis), interferon (inflammatory bowel disease), vasodilator ... In addition, the therapeutic agents include, for example, pegylated interferon beta-1a (multiple sclerosis), sumatriptan (migraine), adalimumab (rheumatoid arthritis), darbepoetin alfa (anemia), belimumab (lupus), peginterferon beta-1a' (multiple sclerosis), sarilumab (rheumatoid arthritis), semaglutide (type 2 diabetes, obesity), dupilumab (atopic dermatitis, asthma, nasal polyps, allergies), glucagon (acute hypoglycemia), epinephrine (anaphylaxis), insulin (diabetes), atropine, and vedolizumab (inflammatory bowel disease (e.g., Crohn's disease and ulcerative colitis)). Pharmaceutical formulations, including, but not limited to, any of the drugs described herein, such as a pharmaceutical formulation comprising a drug listed herein (or a pharma- ceutically acceptable salt of the drug) and a pharma- ceutically acceptable carrier, are also contemplated for use in the delivery devices described herein.A pharmaceutical formulation containing a drug (or a pharma- ceutically acceptable salt of the drug) listed herein may contain one or more other active ingredients, or may be the only active ingredient present.

[0038] Various modifications to the described embodiments are possible and will occur to those skilled in the art without departing from the invention as defined by the scope of the claims that follow.

Claims

1. A subassembly for a medication delivery device (10), the subassembly comprising a housing (30) and a rear cap (50) coaxially disposed within the housing (30); The housing (30) is tubular and extends axially along a longitudinal axis (12) from a proximal end to a distal end; the housing (30) having an inner surface (34) and an outer surface (32), the inner surface (34) of the housing (30) having a first surface (36) facing in the distal direction and a second surface (38) facing in the distal direction; the second surface (38) is closer to the distal end of the housing (30) than the first surface (36); the rear cap (50) extends from a proximal end to a distal end along the longitudinal axis (12), the rear cap (50) comprising a flexible arm (52), the flexible arm (52) comprising a first surface (54) facing in the proximal direction; the rear cap (50) has a second surface (55) facing in the proximal direction, the second surface (55) of the rear cap (50) being closer to the distal end of the rear cap (50) than the first surface (54) of the rear cap (50); the axial distance (L1) between the first surface (36) of the housing (30) and the second surface (38) of the housing (30) is less than the axial distance (L2) between the first surface (54) of the rear cap (50) and the second surface (55) of the rear cap (50), such that when the rear cap (50) is inserted into the distal end of the housing (30) during assembly, the first surface (54) of the rear cap (50) engages the first surface (36) of the housing (30), thereby bending the flexible arm (52) before the second surface (55) of the rear cap (50) engages the second surface (38) of the housing (30).

2. 2. The subassembly of claim 1, wherein the subassembly comprises a power pack, the power pack comprising the rear cap, and wherein the subassembly is configured such that bending of the flexible arm of the rear cap during insertion of the rear cap into the housing unlocks the power pack.

3. 3. The subassembly of claim 1 or 2, wherein the subassembly is configured such that the flexible arm (52) bends perpendicular to the longitudinal axis (12) when the first surface (54) of the rear cap (50) engages the first surface (36) of the housing (30).

4. 4. The subassembly of claim 2 or 3, wherein the power pack comprises a rotor (80), and bending the flexible arm (52) disengages a rotational lock between the rear cap (50) and the rotor (80).

5. 5. The subassembly of claim 4, wherein the subassembly comprises a drug delivery member guard (90), the rotor (80) comprises a groove (84), and the drug delivery member guard comprises a protrusion (95) configured to engage the groove (84) and thereby rotationally lock the rotor (50).

6. 6. The subassembly of claim 1, wherein the inner surface (34) of the housing (30) comprises a first portion (35) at a first distance from the longitudinal axis (12), a second portion (37) at a second distance from the longitudinal axis (12), and an intermediate portion extending from the first portion (35) to the second portion (37), the intermediate portion comprising the first surface (36), and the second surface (38) of the housing (30) at the distal end of the second portion (37).

7. The subassembly of claim 6, wherein when in an unflexed state, the flexible arm (52) is closer to the longitudinal axis (12) than the second portion (37) of the inner surface (34) of the housing (30).

8. 8. The subassembly of claim 1, wherein at least one of the first surface (54) of the rear cap (50) and the first surface (36) of the housing (30) are angled with respect to the longitudinal axis (12).

9. The subassembly of any one of claims 1 to 8, wherein the first surface (36) of the housing (30) is angled toward the longitudinal axis (12).

10. 10. The subassembly of claim 1, wherein the second surface (38) of the housing (30) and / or the second surface (55) of the rear cap (50) extend perpendicular to the longitudinal axis (12).

11. The subassembly of any one of claims 1 to 10, wherein the second surface (38) of the housing (30) is at the distal end of the housing (30).

12. A drug delivery device comprising a subassembly according to any one of claims 1 to 11.

13. A kit of parts comprising a housing (30) according to any one of claims 1 to 11 and a rear cap (50) according to any one of claims 1 to 11.

14. 1. A method of assembling a subassembly of a medication delivery device, said method comprising the steps of: Providing a housing (30) according to any one of claims 1 to 11 and a rear cap (50) according to any one of claims 1 to 11; partially inserting the rear cap (50) into the distal end of the housing (30); pushing the rear cap (50) in the proximal direction relative to the housing (30) such that the first surface (54) of the rear cap (50) engages the first surface (38) of the housing (30) before the second surface (55) of the rear cap (50) engages the second surface (38) of the housing (30), thereby bending the flexible arm (52); A method comprising:

15. 15. The method of claim 14, wherein the subassembly comprises a drug delivery member guard (90) and a power pack, the power pack comprising the rear cap (50) and a rotor (80), and wherein a rotational lock between the rear cap (50) and the rotor (80) is released only after a rotational lock between the rotor (50) and the drug delivery member guard (90) is achieved.

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