Matrix Rings
In Vitro Design and Drug Delivery of Combination Dapivirine (DPV) and Contraceptive Hormone Ethylene Vinyl Acetate (EVA) Vaginal Ring Prototypes Holt JDS1, Derrick T1, Brimer A,1 Loxley A2, Brett Braker2, Matthew Bigert2, Michael Grieco,2 Frank B2, Devlin B1. 1International Partnership for Microbicides, Silver Spring, MD, USA 2Particle Sciences , Inc., Bethlehem, PA USA
Dapivirine is currently formulated in a silicone matrix ring for Phase III clinical trials as a vaginal microbicide. The characteristics of existing EVA formulated rings can inform a DPV and hormone combination ring. This work describes the design and in vitro release testing of EVA vaginal ring prototypes containing DPV and contraceptive hormones.
Methods
In vitro Release and Release Targets EVA rings were placed in 250mL of 25mM Sodium Acetate buffer containing 2% Solutol HS at pH 4.2 for daily release determinations. Rings were stored in this media for 24 hours in a shaker at 37°C and 60 rpm. Release rate targets for Day 60 were based on the in vitro release of relevant components from IPM’s Dapivirine Ring 004, 25mg (≥ 100µg/day) and Nuvaring® (Etonogestrel (ETO) ≥ 120µg/day, Ethinyl Estradiol (EE) ≥ 15µg/day). The two Levonorgestrel (LNG) targets were determined through a review of the literature and intended pharmacokinetic goals ≥35 and 70µg/day. Ring Production Rings were manufactured using standard techniques at Particle Sciences, Inc. with a target cross-sectional diameter of 4mm, overall diameter of 54mm, a 1-3 Newton 10mm bending force and a Shore D hardness of approximately 30 (guided by Nuvaring® characteristics). Active ingredients were mixed into molten polymer (28% vinyl acetate in EVA) and then cooled prior to cryogenic polymer grinding.
Results
Results
Matrix Rings
Core-Sheath Rings
Matrix ring prototypes were produced containing DPV and ETO, EE or LNG. All prototypes met the physical characteristic requirements and release testing was performed over 60 days (Figure 1 & Table 2). Matrix ring prototypes released dapivirine and all hormones with first order kinetics, however, the Day 1 bursts for ETO and LNG were higher (> 1000µg) than desired. Rings loaded with 25 mg DPV released drug at target rates on Day 60 and the Day 1 burst was within accepted limits.
Table 2. Release rates from Matrix Rings Active Dapivirine
Levonorgestrel
Ethinyl Estradiol
Matrix Rings: Ground polymer and actives were injection moulded at 118°C and 120psi.
The effect of drug load and sheath thickness (Table 1) was investigated and prototype rings were stored at 25°C/60% RH and 40°C/75% RH for 3 months to determine the stability of the rings (data not shown).
Table 1. Target Core Sheath Prototypes Manufactured Sheath thickness 100 150 200 150 150
Dapivirine Load (mg in core) 45 45 45 60 30
Levonorgestrel Load (mg in core) 21 21 21 30 10
Day 1 (µg/day) 944 1,700 2,500 630 1,115 1,263 1,323 150 590 550 3,850
Day 30 (µg/day) 68.2 120 190 36 59 67 N/A 7.9 36.5 37.5 223
Day 60 (µg/day) 36.2 66 109 10 22 37 N/A 3 15 10.5 83
Figure 1. Release rates from Matrix Rings
Core-sheath designs had a blunted initial release compared to the matrix rings but the anticipated zero order kinetics was not achieved with a loaded core and blank sheath. DPV-loaded sheaths (not shown here) further increased the overall DPV release across 60 days but only the lower LNG target (35µg/day) was achieved with any configuration. Furthermore, stability storage of samples containing LNG indicated a need for refrigerated conditions to prevent migration of LNG to the ring surface and transfer to the packaging.
Table 3. Average Daily Core Sheath Release Rates Drug Load (mg) Dapivirine 45 45 45 60 30
Average Daily Release (µg/day)
Sheath Thickness
Levonorgestrel 21 21 21 21 10
Dapivirine 41 29 22 29 38
100 169 223 143 149
Levonorgestrel 32 24 19 27 43
Figure 2: Daily Dapivirine and Levonorgestrel Release Rate: The Effect of Sheath Thickness 90
1800
140
1600 In vitro release rate (ug/day)
Core-sheath Rings: Ground polymer and actives were coextruded using a twinscrew coaxial extruder to produce a 4mm diameter product with various drug loads in the core and sheath. Linear polymer pieces were curved around and joined into rings using a hot weld. Cores contained 28% vinyl acetate in EVA and sheaths contained 9% vinyl acetate in EVA (per Nuvaring® specifications).
Etonorgestrel
Load (mg) 7.5 15 25 5 10 15 25 1 4.5 4 28
Ring prototypes with drug loaded cores and blank sheaths were produced containing dapivirine and levonorgestrel with the intention of moderating the Day 1 burst. All prototypes met the physical characteristic requirements and release testing was performed over 60 days (Figure 2 and Table 3).
1400
Levonorgestrel release (15mg)
1200
Dapivirine release (25 mg)
1000
Etonogestrel release (4mg)
800
Ethinyl Estradiol Release (1 mg)
600
Dapivirine release (45 mg) 100 um sheath Dapivirine release (45 mg) 169 um sheath Dapivirine release (45 mg) 223 um sheath
80 70 60 50 40 30 20 10 0
Levonorgestrel (21 mg) 100 um sheath
120
Levonorgestrel (21 mg) 169 um sheath 100
Levonorgestrel (21 mg) 223 um sheath
80 60 40 20 0
0
400
Daily Release rate (µg/day)
Background
Daily Release rate (µg/day)
356
20
Time (days)
40
60
0
20
Time (days)
40
Conclusions
200 0 0
10
20
30 Time (Days)
40
50
60
60
These studies demonstrate that EVA would be a suitable polymer for the dual delivery of dapivirine and LNG from a vaginal ring under refrigerated conditions. These conditions were deemed unsuitable for use in developing countries due to cost and therefore alternative polymers are being evaluated. HIV R4p Cape Town, SA October 27th to 31st, 2014
Dapivirine is currently formulated in a silicone matrix ring for Phase III clinical trials as a vaginal microbicide. The characteristics of existing EVA formulated rings can inform a DPV and hormone combination ring. This work describes the design and in vitro release testing of EVA vaginal ring prototypes containing DPV and contraceptive hormones.
Methods
In vitro Release and Release Targets EVA rings were placed in 250mL of 25mM Sodium Acetate buffer containing 2% Solutol HS at pH 4.2 for daily release determinations. Rings were stored in this media for 24 hours in a shaker at 37°C and 60 rpm. Release rate targets for Day 60 were based on the in vitro release of relevant components from IPM’s Dapivirine Ring 004, 25mg (≥ 100µg/day) and Nuvaring® (Etonogestrel (ETO) ≥ 120µg/day, Ethinyl Estradiol (EE) ≥ 15µg/day). The two Levonorgestrel (LNG) targets were determined through a review of the literature and intended pharmacokinetic goals ≥35 and 70µg/day. Ring Production Rings were manufactured using standard techniques at Particle Sciences, Inc. with a target cross-sectional diameter of 4mm, overall diameter of 54mm, a 1-3 Newton 10mm bending force and a Shore D hardness of approximately 30 (guided by Nuvaring® characteristics). Active ingredients were mixed into molten polymer (28% vinyl acetate in EVA) and then cooled prior to cryogenic polymer grinding.
Results
Results
Matrix Rings
Core-Sheath Rings
Matrix ring prototypes were produced containing DPV and ETO, EE or LNG. All prototypes met the physical characteristic requirements and release testing was performed over 60 days (Figure 1 & Table 2). Matrix ring prototypes released dapivirine and all hormones with first order kinetics, however, the Day 1 bursts for ETO and LNG were higher (> 1000µg) than desired. Rings loaded with 25 mg DPV released drug at target rates on Day 60 and the Day 1 burst was within accepted limits.
Table 2. Release rates from Matrix Rings Active Dapivirine
Levonorgestrel
Ethinyl Estradiol
Matrix Rings: Ground polymer and actives were injection moulded at 118°C and 120psi.
The effect of drug load and sheath thickness (Table 1) was investigated and prototype rings were stored at 25°C/60% RH and 40°C/75% RH for 3 months to determine the stability of the rings (data not shown).
Table 1. Target Core Sheath Prototypes Manufactured Sheath thickness 100 150 200 150 150
Dapivirine Load (mg in core) 45 45 45 60 30
Levonorgestrel Load (mg in core) 21 21 21 30 10
Day 1 (µg/day) 944 1,700 2,500 630 1,115 1,263 1,323 150 590 550 3,850
Day 30 (µg/day) 68.2 120 190 36 59 67 N/A 7.9 36.5 37.5 223
Day 60 (µg/day) 36.2 66 109 10 22 37 N/A 3 15 10.5 83
Figure 1. Release rates from Matrix Rings
Core-sheath designs had a blunted initial release compared to the matrix rings but the anticipated zero order kinetics was not achieved with a loaded core and blank sheath. DPV-loaded sheaths (not shown here) further increased the overall DPV release across 60 days but only the lower LNG target (35µg/day) was achieved with any configuration. Furthermore, stability storage of samples containing LNG indicated a need for refrigerated conditions to prevent migration of LNG to the ring surface and transfer to the packaging.
Table 3. Average Daily Core Sheath Release Rates Drug Load (mg) Dapivirine 45 45 45 60 30
Average Daily Release (µg/day)
Sheath Thickness
Levonorgestrel 21 21 21 21 10
Dapivirine 41 29 22 29 38
100 169 223 143 149
Levonorgestrel 32 24 19 27 43
Figure 2: Daily Dapivirine and Levonorgestrel Release Rate: The Effect of Sheath Thickness 90
1800
140
1600 In vitro release rate (ug/day)
Core-sheath Rings: Ground polymer and actives were coextruded using a twinscrew coaxial extruder to produce a 4mm diameter product with various drug loads in the core and sheath. Linear polymer pieces were curved around and joined into rings using a hot weld. Cores contained 28% vinyl acetate in EVA and sheaths contained 9% vinyl acetate in EVA (per Nuvaring® specifications).
Etonorgestrel
Load (mg) 7.5 15 25 5 10 15 25 1 4.5 4 28
Ring prototypes with drug loaded cores and blank sheaths were produced containing dapivirine and levonorgestrel with the intention of moderating the Day 1 burst. All prototypes met the physical characteristic requirements and release testing was performed over 60 days (Figure 2 and Table 3).
1400
Levonorgestrel release (15mg)
1200
Dapivirine release (25 mg)
1000
Etonogestrel release (4mg)
800
Ethinyl Estradiol Release (1 mg)
600
Dapivirine release (45 mg) 100 um sheath Dapivirine release (45 mg) 169 um sheath Dapivirine release (45 mg) 223 um sheath
80 70 60 50 40 30 20 10 0
Levonorgestrel (21 mg) 100 um sheath
120
Levonorgestrel (21 mg) 169 um sheath 100
Levonorgestrel (21 mg) 223 um sheath
80 60 40 20 0
0
400
Daily Release rate (µg/day)
Background
Daily Release rate (µg/day)
356
20
Time (days)
40
60
0
20
Time (days)
40
Conclusions
200 0 0
10
20
30 Time (Days)
40
50
60
60
These studies demonstrate that EVA would be a suitable polymer for the dual delivery of dapivirine and LNG from a vaginal ring under refrigerated conditions. These conditions were deemed unsuitable for use in developing countries due to cost and therefore alternative polymers are being evaluated. HIV R4p Cape Town, SA October 27th to 31st, 2014
