Comparison of AzaSite

1
Comparison of AzaSite and Azithromycin 1 for
Bacterial Conjunctivitis

• Christopher Crean1, Jason L. Vittitow1, Richard
  C. Zink1, Lori Richards1, Rozemarijn S.
  Verhoeven1, Kendall D. Powell2 and RK Brazzell1
• 1 Inspire Pharmaceuticals, Inc., Durham, NC
• 2 Enthalpy Analytical, Inc. Durham, NC

Research Sponsored by
2
Purpose

• To study the ocular distribution of 1
  azithromycin in an aqueous formulation and 1
  azithromycin in DuraSite (AzaSite).
• To compare the tissue distribution and
  pharmacokinetics of AzaSite after a single
  administration and after the approved seven-day
  course treatment.

3
Methods
This study was designed as a terminal sample
collection study in pigmented rabbits. At the
indicated times after drug administration, 40 µL
of PBS were applied to the ocular surface of
anesthetized animals and 20µL was collected for
estimation of tear drug concentrations. Ocular
tissues were removed in the following order
inferior and superior bulbar conjunctiva,
inferior and superior palpebral conjunctivas
followed by cornea and eyelids. Samples were
analyzed by LC/MS/MS.
Single administration
Sampling times 0, 0.083, 0.25, 0.5, 1, 2, 4, 8,
12, 24, 36, 48, 72, 96, 120 and 144 h
Multiple administration
Sampling times Days 1-6 Predose (0), 0.5, 1 h
Day 7 0, 0.083, 0.25,
0.5, 1, 2, 4, 8, 12, 24, 36, 48, 72, 96, 120 and
144 h
4
Results
The azithromycin conjunctiva and cornea tissue
concentrations are higher for the mucoadhesive
formulation.
Concentration of azithromycin (mean SE) in
conjunctiva and cornea is plotted on a log-linear
graph in nanograms of drug per gram of tissue
over time, where 1000 nanograms is equal to 1
microgram. The conjunctiva plotted in this graph
is an average plot of the four conjunctiva
quadrants. () The dotted line in the graph
represents the MIC50 of azithromycin for typical
bacterial pathogens.
5
Results
Seven days of treatment with azithromycin in
DuraSite increases the observed conjunctiva and
cornea tissue concentrations.
Concentration of azithromycin (mean SE) in
conjunctiva and cornea is plotted on a log-linear
graph in nanograms of drug per gram of tissue
over time, where 1000 nanograms is equal to 1
microgram. The conjunctiva plotted in this graph
is an average plot of the four conjunctiva
quadrants. () The dotted line in the graph
represents the MIC50 of azithromycin for typical
bacterial pathogens.
6
Results
The azithromycin conjunctiva tissue
concentrations reach a stable minimum
concentration by day 2.
Eye Drop Application
Concentration of azithromycin (mean SE) in
conjunctiva is plotted in nanograms of drug per
gram of tissue over time, where 1000 nanograms is
equal to 1 microgram. The conjunctiva plotted in
this graph is an average plot of the four
conjunctiva quadrants. Azithromycin reaches
steady state tissue levels by day 2 that are a
minimum of 15 fold higher than the typical
minimum inhibitory concentration (MIC50) level
for bacterial pathogens. Azithromycin is cleared
from conjunctiva with a 40 hour average half-life.
7
Results
The azithromycin cornea tissue concentrations
reach a stable minimum concentration by the end
of day 2.
Eye Drop Application
Concentration of azithromycin (mean SE) in
cornea is plotted in nanograms of drug per gram
of tissue over time, where 1000 nanograms is
equal to 1 microgram. Azithromycin reaches
steady state tissue levels by day 2 that are a
minimum of 30 fold higher than the typical
minimum inhibitory concentration (MIC50) level
for bacterial pathogens. Azithromycin is cleared
from cornea with a 43 hour average half-life.
8
Results
The azithromycin eye lid tissue concentrations
reach a stable minimum concentration by the start
of day 3.
Eye Drop Application
Concentration of azithromycin (mean SE) in eye
lids is plotted in nanograms of drug per gram of
tissue over time, where 1000 nanograms is equal
to 1 microgram. Azithromycin reaches steady
state tissue levels by day 2 that are a minimum
of 40 fold higher than the typical minimum
inhibitory concentration (MIC50) level for
bacterial pathogens. Azithromycin is cleared
from eye lids with a 125 hour average half-life.
9
Results
Azithromycin resides on the ocular surface at
higher levels and for a longer period of time
when formulated in DuraSite.
Eye Drop Application
Concentration of azithromycin (mean SE) in
tears is plotted in micrograms per milliliter.
10
Azithromycin Calculated Peak and Total
Concentration Levels
Total exposure is reported as meanSE area under
the curve (AUC) in hng/g for the tissues and
hng/mL for tear in log format for visual
purposes while peak concentration is reported in
meanSE ng/g for the tissues and ng/mL for tear.
The reported AUC values for the single dose
studies are from 0-144h while the multi dose AUC
values are after the last eye drop from 144-288h.
Peak concentrations (Cmax) are reported after the
initial eye drop from the single dose studies and
the last eye drop (9th) on Day 7 for the multi
dose study. Within a given tissue there was no
appreciable difference between the different
quadrants of conjunctiva or the inferior or
superior eye lids. The eye lids were not
analyzed during the single dose studies. All
tissues exhibit higher concentrations of
azithromycin in a mucoadhesive formulation and
after multiple administrations.
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Pharmacokinetic Parameters of Azithromycin
Treatment Group Tissue Type AUC0-t (hng/g)a Cmax (ng/g)a Tmax (h) T ½ (h) CL/F (g/h)a Vz/F (g)a
1 Azithromycin with DuraSite (AzaSite) Single Eye Drop Cornea 837,319 40,425 0.08 67 0.28 27.17
1 Azithromycin with DuraSite (AzaSite) Single Eye Drop Average Conjunctiva 737,717 108,356 0.08 63 0.39 33.83
1 Azithromycin with DuraSite (AzaSite) Single Eye Drop Tears 3,016,257 10,539,048 0.08 15 0.1 2.22
1 Azithromycin without DuraSite Single Eye Drop Cornea 196,486 8,775 0.08 91 0.90 118.31
1 Azithromycin without DuraSite Single Eye Drop Average Conjunctiva 79,227 9,547 0.875 48 4.09 272.66
1 Azithromycin without DuraSite Single Eye Drop Tears 154,750 893,482 0.08 37 193 102.11
1 Azithromycin with DuraSite (AzaSite) Multiple Eye Drops Cornea 16,402,463 252,000 1.0 43.3 0.015 0.935
1 Azithromycin with DuraSite (AzaSite) Multiple Eye Drops Averaged Conjunctiva 3,101,108 177,394 0.08 40 0.091 4.315
1 Azithromycin with DuraSite (AzaSite) Multiple Eye Drops Tears 392,021 1,217,500 0.08 78.7 0.754 85.6
1 Azithromycin with DuraSite (AzaSite) Multiple Eye Drops Average Eye Lids 8,146,912 180,300 0.25 125 0.014 4.74
a For tears and aqueous humor, units for Cmax
(ng/mL), AUC0-t (hng/mL), CL/F (mL/h) and Vz/F
(mL) were different
Noncompartmental pharmacokinetic parameters for
the different matrices were calculated with the
WinNonlin pharmacokinetic software from
Pharsight, Inc., utilizing the sparse sampling
option. The time course of analysis varied
depending on the treatment paradigm single
administration time period was from 0- 144 h,
while the multi-dose period was evaluated from
144-288 h post initial eye drop or 0-144 h after
the last eye drop.
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Conclusions

• Azithromycin differs pharmacokinetically from a
  number of antibiotics in its ability to achieve
  and maintain high tissue concentrations after a
  single and multiple eye drops and sustain the
  exposure within the tissue for some time after
  the last eye drop due to its extended half-life.
  
• Pharmacodynamically it differs from other
  macrolide antibiotics (e.g. erythromycin) in its
  ability to kill both gram positive and negative
  bacteria. Also, potential clinical
  effectiveness of azithromycin is further enhanced
  by its formulation within Durasite, which
  increases tissue exposure 5-18 fold over a
  non-mucoadhesive formulation.
• This data provides evidence that azithromycin
  administered from a mucoadhesive formulation has
  levels at steady state
• in conjunctiva at least 15-fold above the
  average MIC,
• in cornea at least 30-fold above the average
  MIC,
• in eye lids at least 40-fold above the average
  MIC.
• persists in all tissues analyzed 6 days after
  the last eye drop