Characterization and Optimization of AMG 517
Supersaturatable Self-Emulsifying Drug Delivery
System (S-SEDDS) for Improved Oral Absorption
PING GAO,1 ANNA AKRAMI,2 FRANCISCO ALVAREZ,1 JACK HU,1 LAN LI,1 CHANDRA MA,1 SEKHAR SURAPANENI2
1
Department of Pharmaceutics, Small Molecule Pharmaceutics, Amgen Inc., One Amgen Center Drive, Thousand Oaks,
California 91320
2
Pharmacokinetics and Drug Metabolism, Amgen Inc., One Amgen Center Drive, Thousand Oaks, California 91320
Received 9 October 2007; revised 29 January 2008; accepted 9 April 2008
Published online 9 June 2008 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jps.21451
ABSTRACT: Supersaturatable self-emulsifying drug delivery systems (S-SEDDS) were
explored to improve the oral absorption of AMG 517, a poorly water-soluble drug
candidate. In vitro characterizations indicate the level of Tween 80 in the formulation
dictates the initial degree of supersaturation of AMG 517, and, therefore, its precipita-
tion kinetics. The presence of a small amount of cellulosic polymer (e.g., HPMC)
effectively sustained a metastable supersaturated state by retarding precipitation
kinetics. Precipitates from the S-SEDDS formulations (with HPMC) from in vitro test
media were identified as amorphous AMG 517 while crystalline AMG 517 precipitates
were found when either HPMC was absent or PVP was present in the formulation.
In vivo pharmacokinetic study in Cynomolgus monkeys reveals that the S-SEDDS
formulation showed 30% higher mean Cmax and comparable exposure (AUC) of
AMG 517 as compared to an aqueous suspension at a dose of 12.5 mg. The rapid
absorption characteristics of AMG 517 from the S-SEDDS formulation as evidenced by
high Cmax and short Tmax are attributed to a high free drug concentration in vivo,
implying a supersaturated state. This case demonstrates that S-SEDDS technology is an
effective approach for improving the rate and extent of absorption of poorly soluble
drugs. ß 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:516
528, 2009
Keywords: Absorption; Bioavailability; In vitro models; Precipitation; Supersatura-
tion; Microemulsion; Oral drug delivery; Polymers; Pharmacokinetics
INTRODUCTION The system is intended to generate and maintain
a meta-stable supersaturated state in vivo by
The supersaturatable self-emulsifying drug deliv- preventing or minimizing the precipitation of the
ery system (S-SEDDS) represents a new formula- drug through use of a PPI. S-SEDDS formulations
tion technology and is designed to contain a have been demonstrated to effectively improve
reduced amount of a surfactant and a water- both the rate and extent of the oral absorption of
soluble polymeric precipitation inhibitor (PPI). poorly water-soluble drugs.1 6 In particular, the
oral exposure of paclitaxel, an extremely poorly
soluble drug, in rats was significantly enhanced
Ping Gao s present address is Abbott Laboratories, 100 via the S-SEDDS approach as compared to the
Abbott Park Road, Abbott Park, IL 60064.
SEDDS formulation.1 This study clearly demon-
Correspondence to: Ping Gao (Telephone: [phone];
strates that the conventional SEDDS approach is
Fax: [phone]; E-mail: [e-mail])
designed to completely solubilize a drug through
Journal of Pharmaceutical Sciences, Vol. 98, 516 528 (2009)
ß 2008 Wiley-Liss, Inc. and the American Pharmacists Association either microemulsion (i.e., Taxol) or emulsion and
516 JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 2, FEBRUARY 2009
SUPERSATURATABLE, SELF-EMULSIFYING DRUG DELIVERY SYSTEM 517
this does not necessarily lead to improvement of kinetics of the drug by observing the particle size
oral absorption of poorly water-soluble drugs. In distribution (PSD) using focused beam reflectance
contrast, the supersaturatable SEDDS formula- measurement (FBRM).
tion is designed to achieve a significantly higher
free drug concentration by overcoming its equili-
brium solubility limit and thus, enable a rapid and EXPERIMENTAL PROCEDURES
more complete absorption. Careful manipulation
of the meta-stable supersaturate state by control- Materials
ling the amount of drug solubilized in microemul-
AMG 517 was internally synthesized at Amgen.
sion and retarding the precipitation kinetic (i.e., to
Polyethylene glycol (PEG) 400, Povidone (PVP,
avoid system crash) with PPI is considered to be
-12PF and -K30), Cremophor EL, and Pluronic
essential in this approach.1 6 The previous pub-
F108 were obtained from BASF. Tween 80 was
lications in exploring the S-SEDDS approach
obtained from Croda. Capmul MCM was obtained
revealed these fundamental concepts and also
from Abitec. Multiple grades of hydroxypropyl
meaningful in vitro tests for evaluation and
methylcellulose (HPMC) were obtained from Dow
optimization.
Chemical Company. Hydroxypropyl methylcellu-
AMG 517 (MW ź 430, structure shown in Fig. 1)
lose acetate succinate (HPMCAS) was obtained
is a potent and selective VR1 antagonist that was
from Shin-Etsu Co. All polymer powders were
being developed for the treatment of acute and
used as received without treatment. An aqueous
chronic pain.7 AMG 517 has a pKa of 1.8 (free base)
suspension vehicle, OraPlus1, was obtained from
and this is not suitable for salt formation. This
Paddock. Hard fill gelatin capsules of size 1 were
drug candidate possesses a high hydrophobicity
obtained from Capsugel. Buffer agents were
(c Log P ź 5.1) and extremely low intrinsic water
obtained from Sigma.
solubility ( 0.05 mg/mL). AMG 517-sorbic acid co-
crystal was identified to possess a substantially
higher solubility and was utilized in preclinical AMG 517 Solubility in Excipients
and clinical evaluations.7 However, low and
Equilibrium solubility of AMG 517 in individual
highly variable in vivo exposures of AMG 517
excipients was estimated by visual observation
were observed from a variety of formulation
described below. A known amount of AMG 517
approaches in preclinical evaluations.
was added into the known quantity of excipients
Therefore, the objective to this work was to
(liquid) in a vial and capped. The vial was put on a
explore the S-SEDDS formulation approach with
rotator and kept rotating at a low speed ( 30 RPM)
AMG 517 in order to improve its oral absorption.
at room temperature for 48 h. If the solution
Prototype S-SEDDS formulations were developed
appeared clear (drug completely dissolved) an
and characterized with respect to the key for-
additional known amount of AMG 517 was added
mulation variables including the concentration of
for another round observation, until the solution
Tween 80 (surfactant), the type of polymer as
appeared slightly turbid (slightly over the equili-
precipitation inhibitor (e.g., PVP, HPMC), the
brium solubility limit). If instead a large amount
molecular weight of a polymer, and the concen-
drug remained undissolved, a known amount of
tration of the polymer. In vitro test methods were
excipient was added for another round of observa-
designed and applied to characterize the perfor-
tion. Solubility of AMG 517 in each excipient was
mance of the prototype S-SEDDS formulations
usually determined after few rounds when the
upon mixing with water. These methods were: (a),
solution appeared just slightly turbid.
determination of apparent drug concentration
time profile and the duration of the supersatu-
rated state, and (b), determination of precipitation
S-SEDDS Formulation Preparation
S-SEDDS formulations with AMG 517 were pre-
pared by placing the drug in a vial and adding the
appropriate amount of solvent (PEG 400) and
surfactant (Tween 80). The vial was then capped,
placed into a water bath at 50 608C and shaken
gently until all of the drug material was completely
Figure 1. Chemical structure of AMG 517. dissolved. After cooling the vial to the room
DOI 10.1002/jps JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 2, FEBRUARY 2009
518 GAO ET AL.
temperature, Capmul MCM was added into the
mixture and the vial was shaken gently to obtain a
clear, uniform solution. For formulations including
a PPI, polymer powder (i.e., HPMC, HPMCAS,
PVP, etc.) was added into the solution and the
vial was vortexed vigorously for 60 s to obtain a
uniform suspension. All formulations were stored
under room temperature before use.
In Vitro Evaluation
Three in vitro test methods were applied for the
S-SEDDS formulation upon mixing with water as
described below.
Supersaturation Test
The apparent drug concentration time profile and
the duration of the supersaturated state were
Figure 2. Experimental set up for in situ determina-
determined. A simulated gastric fluid (SGF) con-
tion of the number and size of precipitated particles
taining 0.01 M HCl and 0.15 M NaCl (pH 2.0) was
with a FBRM probe in aqueous solution.
chosen as the in vitro medium. A Van Kel apparatus
(Model 7010, Van Kel Industries Inc. Chatham, NJ)
at room temperature ( 238C) and the stirring
was used. A total medium volume of 100 mL was
speed was held at 100 rpm.
added to a round bottom, 200 mL vessel equipped
with a Teflon mini-paddle. The solution was main-
Solid State Characterization by
tained at 37 0.58C and the stirring speed was held
X-Ray Powder Diffraction
at 100 rpm. Approximately 0.45 g of the SEDDS
and S-SEDDS formulations (with and without
X-ray powder diffraction (XRPD) profiles of the
HPMC) containing 12.5 mg AMG 517 was filled
precipitates collected after the in vitro tests from
into a size 1 hard gelatin capsule and placed in the
the S-SEDDS formulations were obtained to deter-
test medium. Apparent drug concentration time
mine their crystallinity. X-ray diffraction patterns
profiles were determined as follows: Solution
were obtained using a Phillips automated X-ray
samples ( 0.5 mL) were taken without volume
powder diffractometer, X Pert PRO (PANalytical,
replacement at 0.5, 1, 2 and 3 h and filtered through
Almelo, Netherlands). A Cu Ka X-ray tube
a 10-mm filter. The first 500 mL of filtrate was
(PW337310 LFF, 1.54 Å) was used with voltage
discarded before collecting 200 mLof the filtrate.
and current of 45 kV and 40 mA, respectively. The
100 mL of the collected filtrate was accurately
incident path was set with a 0.04 rad solar slit,
diluted with 1000 mL of 50% acetonitrile followed
15 mm fixed mask, 1/28 fixed anti-scatter slit, and a
by vortexing for about 30 s. A 10 mLvolume of the
1/48 fixed divergence slit. The diffracted beam path
diluted sample solution was then assayed by a
detected by the RTMS detector/X Cellerator, was
HPLC method for AMG 517 as described in Ref. 7.
set with a 0.04rad solar slit, 0.098 parallel plate
Experiments were conducted in duplicate.
collimator, and 0.02 mm nickel filter. Samples of
approximately 10 mg were prepared on the sample
Precipitation Kinetics with FBRM Instrument
holder and the stage rotated over the range of 2u
from 38 to 408. High resolution scans of about 6 h
A Lasentec FBRM S400 probe (Lasentec, Red-
were collected.
mond, WA) was used to determine the in situ
precipitation kinetics of AMG 517 by continuously
monitoring the particle size distribution (PSD). A In Vivo Pharmacokinetic Study in
round bottom, 250 mL vessel with three holes was Cynomolgus Monkeys
used as shown in Figure 2. A Teflon mini-paddle
Formulation Preparation
was put into the vessel through the central hole
and the S400 probe was inserted into the aqueous AMG 517 aqueous suspension was used as a
medium of 100 mL. The solution was maintained control formulation in the in vivo study. The
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 2, FEBRUARY 2009 DOI 10.1002/jps
SUPERSATURATABLE, SELF-EMULSIFYING DRUG DELIVERY SYSTEM 519
suspension vehicle was made by dissolving 20 g mobile phase B at a flow rate of 450 mL/min was
Pluronic F108 into 200 mL OraPlus1 suspension utilized, with a total run time of 4.0 min.
vehicle and stirring overnight at room tempera- A related molecule, AMG831664, was used as
ture. Then, 150 mg AMG 517 (micronized) was the internal standard. Plasma calibration curve
added into 150 g vehicle and mixed by the use of standards were prepared at concentrations of
a homogenizer probe for 3 min as the suspension 0.500, 1.00, 2.50, 5.00, 10.0, 25.0, 50.0, 100, 250,
appeared uniform. AMG 517 concentration in the 500 and 1000 ng AMG 517/mL Lithium hepar-
final suspension was approximately 1 mg/mL. inized male Cynomolgus Monkey plasma.
Approximately 0.45 g of the S-SEDDS formula- AMG 517 concentrations were determined in
tion containing 12.5 mg AMG 517 was filled into lithium heparinized male Cynomolgus Monkey
size 1 gelatin capsule. These capsules were sealed plasma samples by LC MS/MS using ion atmo-
manually with 25% gelatin-aqueous solution and spheric pressure chemical ionization (APCI) with
stored at room temperature before use. multiple reaction monitoring (MRM) in the
positive ion mode. Peak areas were integrated
PK Study Protocol by the Sciex program Analyst, Version 1.4.1,
residing on a Windows 2003 computer. Following
The pharmacokinetic study of AMG 517 was
peak area integration, the data was exported to
conducted in fasted male Cynomolgus monkeys
the software Watson1 (PROD) (version 7.0.0.01,
(n ź 6) in a crossover study design at Covance
InnaPhase Corp., Philadelphia, PA) where con-
(Wisconsin). The body weight of the monkeys
centrations were determined by a weighted (1/x2)
ranged from 3 to 4 kg; a fixed dose of AMG 517 of
linear regression of peak area ratios (peak area of
12.5 mg from either the aqueous suspension or the
AMG 517/peak area of AMG831664) versus the
S-SEDDS formulation was used.
theoretical concentrations of the plasma calibra-
AMG 517 aqueous suspension ( 12.5 mL) was
tion standards. Overall precision and accuracy for
administered to individual monkeys via oral
the calibration standards and QC samples were
gavage intubation, followed by a flush of approxi-
determined by Watson1 (PROD).
mately 10 mL of air to clear the gavage tube.
One capsule containing the S-SEDDS formulation
Pharmacokinetic Analysis
was administered orally to individual monkeys.
In each case, 15 mL water was provided to each Individual plasma concentration time data were
monkey as flush liquid after administration. analyzed by noncompartmental methods using
The wash-out time between each dosing phase WinNonlinTM v.4.1e Build 200408051632 (Phar-
of the study was 13 days. For each phase of the sight Corporation, Mountain View, CA). Nominal
study, approximately 1 mL of blood was collected sampling times were used in the pharmacokinetic
from each animal via the femoral vein into 3 mL analysis. The area under the concentration time
tubes containing lithium heparin anticoagulant at curve from time zero to infinity (AUC0 inf) was
pre-dose, and following oral dose administration calculated using the linear-log trapezoidal
at 0.5, 1, 2, 4, 8, 12, 24, 30, 48, 72, 96, 120, 192, 216, method. The maximum plasma concentration
and 240 h post-dose. Blood tubes were inverted (Cmax) observed and the time at which it was
10 15 times and stored on ice prior to centrifuga- observed (Tmax) were determined directly from the
tion (14000g for 2 min) to obtain plasma. Plasma individual plasma concentration time profiles.
(approximately 500 mL) was transferred to Relative bioavailability ( Frel) was calculated by
separate tubes and stored at 108C until analysis. comparing exposures from the S-SEDDS formula-
tion to the aqueous suspension formulation.
Bioanalytical Method for Pharmacokinetic Studies
Lithium heparinized male Cynomolgus Monkey
RESULTS AND DISCUSSION
plasma samples (50 mL) were extracted using
96-well liquid/liquid extraction (LLE) to isolate
Solubility of AMG 517 in Solvent,
the analyte and internal standard. Samples were
Surfactants and Lipids
separated by reversed-phase liquid chromatogra-
phy on a Thermo Electron Hypersil BDS C18, Solubility of AMG 517 in pharmaceutically
50 mm 2.1 mm (5 mm) analytical column. The acceptable excipients appropriate for SEDDS
mobile phase was 75:25 MeOH:10 mM Ammonium formulations is reported in Table 1. AMG 517
Acetate in Water (Mobile Phase B). An isocratic of shows a solubility of approximately 44 mg/g in
DOI 10.1002/jps JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 2, FEBRUARY 2009
520 GAO ET AL.
Table 1. AMG 517 Solubility in Liquid Excipients solid particles of various sizes. Further complicat-
Suitable for SEDDS Formulation
ing the analysis was the fact that the distribution
of AMG 517 among these states was dynamic and
Excipient Solubility (mg/g)
changed rapidly over time. Precipitation of AMG
517 was anticipated upon dilution of the SEDDS
PEG 400 44
Propylene glycol <5 formulation in the test medium due to an
Propylene carbonate 4
insufficient amount of surfactant used. While
Ethanol USP (95%) <5.6
the particle size of the precipitated solids grew
Triacetin 6.5
significantly during the course of the test,
Glycerine <1
accurate determination of the AMG 517 concen-
Transcutol 75
tration in solution at any given time was difficult if
Tween 80 31
not impossible, due to the difficulty in separating
Cremophor EL 35
the phases. For the purpose of screening
Capmul MCM 3
formulations, a 10 mm filter was used to process
Corn oil <1
solution samples prior to HPLC analysis in order
Ethyl oleate <5
to limit the presence of precipitated drug particles
Sesame oil <1
Oleic acid 12 of large size. Nevertheless, AMG 517 concentra-
Octanoic acid 11
tions determined were clearly a measure of the
combined concentration of drug present in various
states rather than a measure of the free drug
PEG 400 and 31 mg/g in Tween 80. Low solubility concentration in the test medium.1,2
(<1 mg/g) of AMG 517 was observed in lipids, A prototype SEDDS formulation containing
regardless of their type (e.g., mono-/di-/tri-glycerides) 20% Tween 80 and two related S-SEDDS for-
or the fatty acid chain length (e.g., C10 vs. C18). mulations (e.g., the same composition but with 5%
Based on the consideration of drug solubility either HPMC (E5) or PVP (12 PF)) were evaluated
in individual excipients and miscibility among by the supersaturation test. The apparent AMG
them, PEG 400 (solvent), Tween 80 (surfactant) 517 concentration time profiles from the three
and Capmul MCM (lipid) were chosen as the formulations in the SGF (pH 2.0) are shown in
ingredients for prototype AMG 517 SEDDS Figure 3. The theoretical concentration of AMG
formulation. 517 in the test medium was 0.125 mg/mL based on
the dilution factor of 100 (i.e., 12.5 mg AMG 517 in
100 mL medium). Upon mixing with the SGF, the
Characterization of SEDDS and
S-SEDDS Formulations
In Vitro Assessment of Supersaturated State
As the S-SEDDS formulation was designed to
yield a supersaturated state, it was desired to
have a meaningful in vitro test to assess the drug
concentration sustained in the supersaturated
state and estimate the degree of supersaturation
as a function of time. In this work, the in vitro
supersaturation test was designed to determine
the apparent drug concentration time profile and
the duration of the supersaturated state.
Accurate determination of the free drug con-
centration of AMG 517 in a supersaturated state
was analytically challenging, primarily due to the
non-sink condition employed and inevitable pre-
cipitation of AMG 517 resulting from the high
Figure 3. In vitro mean apparent AMG 517 concen-
degree of supersaturation. In the aqueous med-
tration time profiles observed from 20% (w/w) Tween
ium, the drug may coexist in three states: free
80 SEDDS formulation without PPI, or S-SEDDS for-
molecules in solution, solubilized molecules parti- mulation with 5% either PVP(12PF), or HPMC(E5).
tioned into the microemulsion, and precipitated Results were averaged from duplicate runs.
JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 2, FEBRUARY 2009 DOI 10.1002/jps
SUPERSATURATABLE, SELF-EMULSIFYING DRUG DELIVERY SYSTEM 521
SEDDS formulation (without polymer) initially
appeared as a microemulsion with a bluish
reflection. However, the solution developed clou-
diness within 20 min and visible white solid
precipitates of AMG 517 were observed. The
formation of AMG 517 precipitates in the test
medium suggested that the medium was in a super-
saturated state. As shown in Figure 3, the apparent
AMG 517 concentration from the SEDDS formu-
lation was initially about 0.12 mg/mL at t ź
10 min., and decreased rapidly to 0.01 mg/mL at
t ź 40 min and afterwards, accompanying pre-
cipitation of AMG 517. The apparent AMG 517
concentration in the test medium from the SEDDS
formulation over the 24-h course was estimated to
Figure 4. In vitro mean apparent AMG 517 concen-
be 0.005 mg/mL and this was considered as close
tration time profiles observed from 30% (w/w) Tween
to the   equilibrium solubility  in the medium.
80 SEDDS formulation without PPI, or S-SEDDS with
Therefore, the degree of supersaturation of AMG HPMC (E5) of 0.5, 2, 5, and 10%, respectively. Results
were averaged from duplicate runs and the stand devia-
517 from this test was initially estimated around
tion of AMG 517 concentration 0.010 mg/mL.
24 (e.g., 0.12/0.005 ź 24). Similarly, the apparent
concentration time profile from the S-SEDDS
formulation containing 5% PVP (12PF, low MW)
HP groups.8 The K type HPMC possesses about
is almost superimposed to that of the SEDDS
22% methyl group substitution while the E type
formulation (Fig. 3), indicating a lack of effect
possesses about 29% methyl group substitution.
from PVP in sustaining the apparent AMG 517
As the HP substitution in both E- and K-type
concentration.
HPMC polymers is almost constant (8 10%), the E
In contrast, the S-SEDDS formulation with
type HPMC is more hydrophobic than the K type
5% HPMC (E5, low MW) showed a consistently
HPMC. Both E and K series of HPMC have
higher apparent AMG 517 concentration time
different viscosity grades (corresponding to dif-
profile (also plotted in Fig. 3) as compared to the
ferent average molecular weight) available. From
same SEDDS formulation without polymer and
the nomenclature of HPMC polymers, the viscos-
the S-SEDDS formulation with 5% PVP (12PF).
ity grade and the average MW of these HPMC
The comparative study of these formulations
polymers follows the same rank order8:
of the same composition but only varying the
absence or presence of a polymer clearly indicates
E4M E50 > E5; K100 > K3; and E5 K3:
that the presence of a small amount of HPMC
(5%, w/w) can retard AMG 517 precipitation and
Figure 5 shows several apparent AMG 517
sustain a higher apparent concentration over
concentration time profiles obtained from the
approximately 60 min.
SEDDS formulations with a fixed 5% HPMC but
Further evaluations were directed to other
varying in the type (E vs. K) and the viscosity
prototype S-SEDDS formulations containing
grade. These results suggest the effectiveness of
30% Tween 80 with 0.5, 2.0, 5.0, and 10% (w/w)
HPMC as PPI following the rank order below:
HPMC (E5) in the formula. This was to evaluate
the influence of the amount of HPMC (E5) upon
E4M > E50 > E5 K100 > K3
the duration of the supersaturated state. As
plotted in Figure 4, the apparent AMG 517
concentration time profiles suggest that the The rank order estimated from the super-
presence of 0.5 5% HPMC (E5) appears suffi- saturation test suggests that the hydrophobic
ciently effective, yielding similar apparent AMG E-type HPMC performs better than the K-type
517 concentration time profiles while the pre- HPMC in sustaining a supersaturated state of
sence of 10% HPMC (E5) appears less effective. AMG 517. This trend also suggests HPMC with a
There are two types of HPMC polymers, K and E higher viscosity grade (i.e., a higher average MW),
series, commercially available. These two types of as seen in both E- and K-types, appears more
HPMC differ in the substitution of the methyl and effective in sustaining the supersaturated state.
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522 GAO ET AL.
In this work, the FRBM was utilized to obtain
real time measurements of both dimension and
number of AMG 517 precipitated particles. Each
S-SEDDS formulation was introduced as liquid
into a flask containing 100 mL test medium (e.g.,
water) with a stirring rate of 100 rpm. The PSD
profile observed, at any time, provided a direct
assessment of the precipitation kinetics of AMG
517 from the supersaturated state.
The concentration of the surfactant, Tween 80,
in the S-SEDDS formulation is considered to be a
critical formulation variable since its amount
dictates the initial degree of solubilization of AMG
517 upon mixing the formulation with water and,
Figure 5. In vitro mean apparent AMG 517 concen-
therefore, the supersaturated state.1 3 In order to
tration time profiles observed from 30% (w/w) Tween
determine the influence of the concentration of
80 S-SEDDS formulations with 5% HPMC of -K3, K100,
Tween 80 upon AMG 517 precipitation kinetics, a
-E5, -E50, and -E4M, respectively. Results were aver-
series of SEDDS formulations containing Tween
aged from duplicate runs and the stand deviation of
80 varying from 10, 20, 30 to 40% (w/w) were
AMG 517 concentration 0.010 mg/mL.
characterized. (The compositions of these SEDDS
and corresponding S-SEDDS formulations are
reported in Table 2.) All PSD profiles observed
In Vitro Characterization of AMG 517 Precipitation
from these SEDDS formulations (without PPI) at
with FBRM Technology
t ź 60 min. are shown in Figure 6A for comparison.
In order to characterize a precipitation process, The significant variation of the peak counts/s.
a fast and reliable estimation of the formation, in these PSD profiles accompanying variation of
growth, aggregation and attrition of particles Tween 80 concentration reveals that it indeed
in the system is crucial. FBRM is a desirable dictates AMG 517 precipitation kinetics. For
measurement technology that conducts in situ instance, the SEDDS formula containing 10%
particle characterization. Its detection principle is Tween 80 exhibited a PSD peak of 720 counts/s
discussed in details in scientific literature.9 10 around 10 mm (Fig. 6A). Increasing Tween 80
FBRM measures a chord length (and its distribu- concentration to 20%, the PSD profile shows the
tion) of the particles. In this work, the chord same distribution but a significantly lower peak
length is treated and reported as the particle size. value of 380 counts/s. Further increasing Tween
In particular, we were interested in determining 80 concentrations to either 30 or 40%, the shape of
the effect of PPI regarding its type and concen- the PSD profiles was not affected and lower peak
tration upon AMG 517 precipitation kinetics in a values (e.g., 220 240 counts/s) were observed.
comparative manner. It is worth noting that as There was no improvement of the peak counts/s.
a result of the inherit limitation, FBRM probe when Tween 80 concentration was increased from
shows a poor detection to particles of less than 30% to 40%, suggesting an optimal concentration
1 mm and typically detects particle size within of Tween 80 around 30%. The FBRM results agree
1 and 1000 mm. with the apparent AMG 517 concentration time
Table 2. Composition of Prototype SEDDS and S-SEDDS Formulations of AMG 517 Examined by In Vitro Tests in
this Work
Ingredient Function Quantity (mg/g)
AMG 517 API 30 30 30 30
PEG 400 Solvent 780 680 580 480
Tween 80 Surfactant 100 200 300 400
Capmul MCM Lipid 90 90 90 90
HPMC (E5)a Precipitation inhibitor 0 or 50 0 or 50 0 or 50 0 or 50
a
When polymer was used, it was suspended in the solution.
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SUPERSATURATABLE, SELF-EMULSIFYING DRUG DELIVERY SYSTEM 523
Figure 6. Mean PSD profiles observed at t ź 60 min. from (A) SEDDS formulations
(without PPI) containing 10%, 20%, 30% and 40% (w/w) Tween 80, respectively;
(B) SEDDS formulations containing 30% Tween 80 with and without 5% HPMC(E5);
(C) S-SEDDS formulations with 5% HPMC of -E5, -E50, -E4M, -K3, -K100, or 5% PVP
of -12PF and -K30 or 5% HPMCAS, and (D) same data plotted in (C) but with a more
sensitive Y scale.
profiles of these SEDDS formulations observed shows a peak around 10 mm with 230 counts/
from the supersaturation test (data not shown). s. The PSD profiles shown in Figure 6C exhibit
The in situ PSD profiles from the S-SEDDS that incorporation of 5% PVP in the S-SEDDS
formulations indicate that incorporation of a formulation, either PVP (12PF, low MW) or PVP
small amount 2 5% HPMC (E5) effectively (K30, high MW), appears ineffective while
suppresses AMG 517 precipitation. This is clearly HPMCAS and HPMC (both E and K series) were
evidenced by the comparison of the PSD profiles highly effective. Figure 6D shows a close look of
between a pair of the SEDDS formulations the PSD profiles observed from S-SEDDS for-
containing 30% Tween 80 with and without mulations with 5% HPMC at different viscosity
HPMC (E5). As shown in Figure 6B, the S-SEDDS grades including -E5, -E50, -E4M, -K3, and -K100.
formulation with 5% HPMC (E5) shows a PSD The PSD data observed are in excellent agreement
profile with its peak shifting to a slightly smaller with the apparent AMG 517 concentration time
size of 7 mm and less than 10 counts/s at t ź 60 min. profiles (Fig. 5) from the same formulations. The
while the SEDDS formulation (without PPI) former test measures AMG 517 precipitation
DOI 10.1002/jps JOURNAL OF PHARMACEUTICAL SCIENCES, VOL. 98, NO. 2, FEBRUARY 2009
524 GAO ET AL.
kinetics by counting solid particles and its Table 3. Composition of the S-SEDDS Formulation of
distribution while the latter test provides a quan- AMG 517 for In Vitro PK Evaluation
titative estimation of the apparent drug concen-
Quantity
tration remaining in the test media. The two
Ingredient Function (mg/g)
in vitro characterizations for AMG 517 S-SEDDS
formulations are complementary to each other AMG 517 Drug 30
PEG 400 Solvent 560
and these observations with time-dependent
Tween 80 Surfactant 300
feature are in good agreement. These two in vitro
Capmul MCM Lipid 90
tests are proven appropriate tools for S-SEDDS
HPMC (E4M)a Precipitation inhibitor 20
formulation screening and optimization.
a
Suspended in the solution.
Characterization of Precipitated Solids
Precipitated solids were collected from the in vitro (without HPMC, composition reported in Table 3)
precipitation characterization and examined for were highly crystalline; the precipitate is con-
their crystallinity by XRPD. As shown in firmed to be the original crystalline form of AMG
Figure 7A, AMG 517 precipitates from the use 517 (starting material). In contrast, the precipi-
of a SEDDS formulation containing 30% Tween 80 tates collected from the S-SEDDS formulation
with 5% HPMC (E5) were completely amorphous
(Fig. 7A). We have examined the crystallinity
of precipitates from all prototype SEDDS and
S-SEDDS formulations varying Tween 80 con-
centration and the type of PPI. We found that
AMG 517 precipitates were exclusively amor-
phous when a cellulosic polymer (e.g., HPMC
or HPMCAS) was present in the formula. In
contrast, AMG 517 precipitates from the SEDDS
formulations with PVP (both 12PF and K30) were
always crystalline (Fig. 7B).
In Vivo PK Evaluation of S-SEDDS Formulation
An oral bioavailability study was conducted in
fasted Cynomolgus monkeys (n ź 6, crossover).
The AMG 517 S-SEDDS formulation was eval-
uated against the aqueous suspension (as control
reference) that was used in previous preclinical
evaluations.7 The composition of the S-SEDDS
formulation for the in vivo study is reported in
Table 3.
Figure 8 shows individual AMG 517 plasma-
concentration profiles in monkeys upon dosing of
the aqueous suspension and the S-SEDDS for-
mulation. The mean PK parameters (e.g., Cmax,
Tmax, AUC, and the CVs) of both formulations are
summarized in Table 4 for comparison. As both
formulations showed rapid absorption with a
short Tmax around 1 h, the S-SEDDS formulation
showed a significantly higher mean Cmax of 1346
Figure 7. XRPD spectra of precipitates isolated from
ng/mL as compared to that (1025 ng/mL) of the
the in vitro FBRM experiment with (A) S-SEDDS for-
aqueous suspen