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Drug/cyclodextrin nanoparticles for
topical drug delivery to the posterior
segment of the eye
Thorsteinn Loftsson, Ph.D.
Faculty of Pharmaceutical Sciences
University of Iceland
[email protected]
September 20th 2016, 11:30-12:00
Cyclodextrins
Bacterial
digestion
But cyclodextrins are able to
form inclusion complexes:
Cyclodextrins are oligosaccharides and
share many of the physicochemical and
biological properties of the linear
oligosaccharides,
including
their
toxicological
and
pharmacokinetic
properties.
αCD
βCD
γCD
Cyclodextrins and their
derivatives
Usage in pharmaceutical products:
1. Solubilizers
2. Stabilizers (can increase both chemical and physical
stability)
3. Penetration enhancers
4. As nanoparticle building blocks
etc.
Can be found in about 40 marketed drug products.
Aggregation of cyclodextrin complexes
+
Transmission electron microscopic (TEM)
image of hydrocortisone/HPβCD aggregates.
Hydrocortisone flux through semipermeable cellophane membrane
with MWCO 15 kDa (8 complexes).
Cyclodextrin (CD) aggregation - some observations:
• The natural αCD, βCD and γCD do form aggregates by
themselves in pure aqueous CD solutions but the
aggregation is very low with much less than 1% of
dissolved CD present in the form of aggregates.
• Formation of drug/CD inclusion complexes increases
the aggregation, both in the case of the natural CDs
and in the case of the randomly substituted CD
derivatives.
• The diameter of the complex aggregates depends on
the drug/CD properties as well as the concentration of
drug/CD inclusion complexes, increasing with
increasing availability of drug/CD complexes.
• The degree of aggregation depends on the availability
of drug/CD complexes in the aqueous solution,
increasing with increasing availability of drug/CD
complexes.
• Addition of organic solvents such as ethanol that are
known to decrease the complexation will reduce the
aggregation. Also, heating of aqueous CD solutions will
result in decreased aggregation.
• In aqueous solutions drug/CD complex aggregates are
in dynamic equilibrium with un-aggregated (i.e., free)
complexes. Aggregates are constantly being formed
and dissembled.
• The complex aggregates are unstable and dissemble
up on media dilution (and filtration).
• Complexes of the natural αCD, βCD and γCD have
limited solubility in water and tend to precipitate in
aqueous solutions as solid drug/CD complex
aggregates. Their complexes are frequently less
soluble than the CDs themselves.
Topical drug delivery to the eye
I. Barriers to Ocular Drug Delivery:
 Aqueous drug solubility. Limited
solubility of lipophilic drugs in aqueous eye
drops and tear film.
 The short contact time. The normal tear
fluid is only about 8 µl and the average
tear secretion is 1.2 μl/min.
 The lipid membrane barrier. In general,
the passive drug permeation through the
lipid membrane barrier, i.e. cornea or
conjunctiva/sclera, is very slow.
II. Conventional eye drops:
The aqueous tear fluid.
About 50% is replaced
every 3 to 4 minutes.
Less than 5%
of the dose
permeates into
the eye.
III. Tasks to improve eye drop delivery:
 Increase aqueous solubility of lipophilic
molecules.
 Sustained high drug conc. in tear film.
 Enhanced drug partition into eye wall.
Most of the dose
is absorbed into the
systemic blood
circulation mainly
via the nasal cavity.
Nanoparticulate drug/γCD delivery system
The system consists of aqueous eye drops containing nanosuspension of drug/γCD complexes.
Microparticles, 50 to 90% of the drug is in small microparticles with diameter
of 1 to 10 μm. The dimeter depends on the preparation method and
excipients (e.g., polymers) used. The microparticle increase the drug contact
time from few minutes to several hours and provide for high and sustained
concentration of dissolved dexamethasone in the tear fluid. Water is about
85% of the eye drops.
Nanoparticles, 10 to 50% of the drug is present as drug/γCD nanoparticles
with diameter of 100 to 300 nm. The nanoparticles increase the contact time
with the mucus layer that results in enhanced drug delivery through the tear
film (i.e. the unstirred water layer) to the membrane surface.
Drug/γCD complexes enhance the aqueous drug solubility. In case of
dexamethasone the enhancement is 30-fold but it can be as high as couple
of hundred fold for very poorly soluble drugs. This increases the drug
concentration gradient over the membrane barrier and, consequently, drug
permeation into the eye.
+
The free drug permeates into the eye but the carrier, γCD, is metabolized to
maltose and glucose by α-amylase that can be found in the tear fluid and in
the GI tract.
The result is increased ocular bioavailability from less than 5% to about
50% and decreased systemic drug delivery (5-fold decrease in case of dexamethasone).
γ-Cyclodextrin and its derivatives are basically the
only
cyclodextrins
metabolized
by
human
α-amylase (found in the tear fluid, saliva, etc.).
Michaelis–Menten parameters of the γ-cyclodextrin, 2-hydroxypropyl-γcyclodextrin and sulfobutylether γ-cyclodextrin degradation by porcine
pancreatic α-amylase.
Vmax (mM/min)
γCD
17.01
KM (mM)
0.54
Vmax/KM (min-1)
31.5
t½
1.3 s
HPγCD
0.07
88
8.0∙10-4
14.4 h
SBEγCD
0.57
134
4.3∙10-3
2.7 h
Lumholdt, L.R., Holm, R., Jorgensen, E.B., Larsen, K.L., In vitro investigations of α-amylase mediated
hydrolysis of cyclodextrins in the presence of ibuprofen, flurbiprofen, or benzo[a]pyrene. Carbohydrate
Research 362, 56-61 (2012).
Lumholdt, L., Pipkin, J.D., Antle, V., Reaction between α-amylase and CAPTISOL® and other SBEcyclodextrins (poster presentation), 4th European Conference on Cyclodextrins, October 6th-9th, 2015, Lille,
France.
Drug Delivery Mechanism (on the eye surface)
Tear fluid
Microparticle
Mucus (unstirred water layer)
Nanoparticle
Single complex
+
Unbound
drug molecule
Glucose
Maltose
Washed down into the lacrimal duct to
be further metabolized in the GI tract.
Lipophilic membrane
Inner layers
Advantages over “normal” nanoparticles
Normal Nanoparticles (NP):
 Limited increase in aqueous solubility
of lipophilic drug molecules.
 Sustained low concentration of
dissolved drug in tear film.
 Do not increased drug concentration
gradient or result in only limited
increase.
Solubilizing Nanoparticles (SNP):
 Increase aqueous solubility of
lipophilic drug molecules.
 Give sustained high concentration of
dissolved drug in tear film.
 Increase drug concentration gradient
 enhanced drug permeation into
the eye.
Dorzolamide
O
H3C
S
H
O
O
H3C
S
SO2NH2
H
pKa = 6.4
NHCH2CH3
H+
Molecular weight
Melting point
Calculated logP(octanol/water)
Solubility in water at 25°C
O
S
O
H3C
S
H
SO2NH2
H
NHCH2CH3
Dorzolamide
324.4 Da
283-285°C
pKa = 8.5
O
S
S
SO2NH -
H
H
NHCH2CH3
Dorzolamide hydrochloride
359.9 Da
264°C
1.7 (at pH 7.4)
6.7 mg/ml (at pH 7.4)
P. Jansook, E. Stefánsson, M. Thorsteinsdóttir, B. B. Sigurdsson, S.
S. Kristjánsdóttir, J. F. Bas, H. H. Sigurdsson, T. Loftsson,
„Cyclodextrin solubilization of carbonic anhydrase inhibitor drugs:
formulation of dorzolamide eye drop microparticle suspension”, Eur.
J. Pharm. Biopharm. 76, 208-214 (2010).
Dorzolamide concentration (g/ml) in aqueous humor after
topical administration to rabbits (mean  SD; n=6-8)
Aqueous humor
14-fold (0-24h)
SEM image of the
dorzolamide eye
drop
3% dorzolamide eye drop formulation containing 18% w/v CD
(○); and Trusopt(●) that contains 2% dorzolamide in soln.
Dorzolamide/γCD eye drops in humans (mean  SD; n=7)
DorzSNP once per day
Trusopt® three times
per day
B. S. Gudmundsdottir, D. Petursdottir, G. M. Asgrimsdottir, M. S. Gottfredsdottir, S. H.
Hardarson, G. Jóhannesson, S. V. Kurkov, P. Jansook, T. Loftsson, E. Stefansson:
γ-Cyclodextrin nanoparticle eye drops with dorzolamide. Effect on intraocular pressure in
man, J. Ocul. Pharmacol. Ther. 30, 35-41 (2014).
Dexamethasone
Molecular weight
Melting point
Calculated logP(octanol/water)
Solubility in water at 25°C
H-bond acceptors
H-bond donors
392.5 Da
262-264°C
2.03
35 µg/ml
5
3
Concentration of dexamethasone in the tear film after
topical application of 1 drop
Rabbits
Humans
DexSNP
DexSNP
Maxidex®
Maxidex®
● Maxidex® (dexamethasone alcoholic suspension 1 mg/ml)
○ aqueous dexamethasone/γCD nanoparticle eye drop suspension (15 mg/ml)
Dexamethasone/γCD Nanosuspension
Clinical trials of the DexSNP eye drops
Diabetic macular edema (DME): Swelling of the retina in
diabetes mellitus due to leaking of fluid from blood vessels
within the retina.
Uveitis is inflammation of the uvea, that is the pigmented layer
between the inner retina and the outer fibrous layer composed
of the sclera and cornea.
Both DME and uveitis phase II studies show promising clinical
effect.
The trials in DME demonstrate very good efficacy of the eye
drops and the results are comparable to intravitreal injected
drugs.
A. Ohira, K. Hara, G. Jóhannesson, M. Tanito, G.M. Ásgrímsdóttir, S.H. Lund, T. Loftsson, E.
Stefánsson, Topical dexamethasone γ-cyclodextrin nanoparticle eye drops increase visual
acuity and decrease macular thickness in diabetic macular oedema. Acta Ophthalmol. 93,
610-615 (2015).
S. Shulman, G. Jóhannesson, E. Stefánsson, A. Loewenstein, A. Rosenblatt, Z. Habot-Wilner,
Topical dexamethasone-cyclodextrin nanoparticle eye drops for non-infectious Uveitic macular
oedema and vitritis – a pilot study. Acta Ophthalmol. 93, 411-415 (2015).
S. Krag, A. Hessellund, Topical dexamethasone-cyclodextrin microparticle eye drops for
uveitic macular oedema. Acta Ophthalmol. 92(8), e689-90 (2014).
M. Tanito, K. Hara, Y. Takai, Y. Matsuoka, N. Nishimura, P. Jansook, T. Loftsson, E.
Stefánsson, A. Ohira, Topical dexamethasone-cyclodextrin nanoparticle eye drops improve
visual acuity and reduce retinal thickness in diabetic macular edema, Invest. Ophthalmol. Vis.
Sci. 52, 7944-7948 (2011).
DexNP | Clinical Trials DME*
DexNP compares favourably with current standard of care
Macular thickness on OCT
50
12
10
8
6
4
2
0
0
-2
•
1
2
3
4
5
6
7
Months
8
9 10 11 12
Mean change in CRT from baseline
Mean change in BCVA letter score from baseline
Visual acuity
0
0
1
2
3
4
5
6
7
8
9 10 11 12
-50
-100
-150
-200
-250
Months
Short term data for DexNP compares favorably with ranibizumab (Lucentis), both in terms of
vision (BCVA) and central retinal thickness (CRT).
BCVA: Best Corrected Visual Acuity; OCT: Optical Coherence Tomography
*Ohira et al. 2015; Tanito et al 2011; Massin et al. 2010 (RESOLVE); Mitchell et al 2011 (RESTORE)
DexNP| Clinical Trials DME
Change in BCVA
- Comparing different clinical trials
(mean improvement)
Time point
(months)
eye drops
5.5 – 7.5
1-2
Ozurdex®
implant
0.4 – 4.1
39
Iluvien®
implant
3.7 – 5.2
24
Lucentis®
intravitreal inj.
7.9
24
Eylea®
intravitreal inj.
9.4 – 11.1
24
ETDRS letters
Non-invasive
DexSNP
Invasive
Laser
2.5
BCVA: Best Corrected Visual Acuity; ETDRS: Early Treatment Diabetic Retinopathy Study
Unstable self-assembled nanoparticles. Fall apart upon
dilution and even during filtration. Same toxicologic profile
as γ-cyclodextrin itself.
Targeted drug delivery. Behaves similar to nanoparticles
and liposomes.
Increased drug contact time with the eye surface. The
eye drops provide sustained release over several hours
compared to a few minutes with conventional eye drops.
Increases concentration of dissolved drug in the tear
fluid. Gives higher drug concentration gradient.
The carrier, γ-cyclodextrin, is metabolized in the tear
fluid.
About 10-fold increase in drug bioavailability. The eye
drops deliver 30-50% of the drug into the eye compared to
3-5% for conventional eye drops.
22
Thank you
From left: Thorsteinn Loftsson, André Rodrigues Sá Couto (PhD student from Portugal),
Alexey Ryzhakov (Postdoc from Russia), Blanca Lorenzo Veiga (PhD student from Spain),
Chutimon Muankaew (PhD student from Thailand), Pitsiree Praphanwittaya (PhD student
from Thailand), Phennapha Saokham (PhD student from Thailand), Zoltán Fülöp (Oculis
Scientist from Hungary), Sunna Jóhannesdóttir (PhD student from Iceland), and Agnieszka
Popielec (PhD student from Poland).