Note: Descriptions are shown in the official language in which they were submitted.
'110 94/21227 2156922 PCT/US94/02222
FLUOROCARBON EMULSIONS WITH REDUCED PULMONARY
GAS-TRAPPING PROPERTIES
Background or th~ Invention
The present invention relates to emulsions comprising
highly fluorinated or perfluorinated compounds. More
particularly, it relates to fluorocarbon emulsions exhibiting
reduced pulmonary gas-trapping properties.
Fluorocarbon emulsions find uses as therapeutic and
diagnostic agents. Most therapeutic uses of fluorocarbons are
related to the remarkable oxygen-carrying capacity of these
compounds. One commercial biomedical fluorocarbon emulsion,
Fluosol (Green Cross Corp., Osaka, Japan), is presently used
as an oxygen carrier to enhance oxygen delivery to the
myocardium during percutaneous transluminal coronary
is angioplasty (Fluosol, Summary Basis of Approval, Reference No.
OB-NDA86-0909, Dec. 1989). Fluorocarbon emulsions have also
been used in diagnostic applications such as imaging.
Radiopaque fluorocarbons such as perflubron (perfluorooctyl
bromide or C8F17Br) are particularly useful for this purpose.
Increased pulmonary residual volume (IPRV) has been
observed in association with the intravenous administration of
various perfluorocarbon emulsions in certain animal species.
While the direct correlation between IPRV and pulmonary
dysfunction has not been positively identified, dysfunction
(including reduced arterial P02, signs of respiratory
distress, and even lethality) has been observed on occasions
in certain sensitive animal species in which IPRV was later
identified.
IPRV occurs as a result of gas-trapping within the
pulmonary system, and prevents the normal deflation of lungs
when intrathoracic pressure is equalized to ambient pressure
such as during necropsy of an animal. It is believed that
gas-trapping occurs as a consequence of foam or bubble
formation in the lungs. It is noted that under normal
WO 94/21227 922
PCT/US94/02222
-2-
circumstances, bubbles or liquid bridges form and disappear
spontaneously within alveoli without a gas-trapping effect.
It is believed, however, that IPRV occurs when these bubbles
grow in the presence of fluorocarbon vapors, trapping larger
amounts ot air within the lung. As stated above, if bubble
formation continues, pulmonary dysfunction can result (in
certain animal species). IPRV depends on the vapor pressure
of the fluorocarbon component(s), with lower vapor pressure
fluorocarbons not exhibiting the phenomenon. Diminution of the
vapor pressure of the fluorocarbon component(s) also plays a
critical role in stabilizing the emulsion droplets against
Ostwald ripening, the key destabilizing mechanism at work in
small particle fluorocarbon emulsions. The prior art has
described fluorocarbon emulsion formulations designed to
inhibit Ostwald ripening. See, e.g. Davis et al., U.S. Patent
No. 4,859,363; Meinert, U.S. Patent No. 5,120,731; Kabalnov et
al., Kolloidn Zh., 48: 27-32 (1986). These formulations
contain a mixture of two fluorocarbon components, the
secondary fluorocarbon component having a significantly higher
molecular weight, and lower vapor pressure relative to the
primary fluorocarbon component.
Following intravenous administration, fluorocarbon
emulsion particles are taken up and temporarily retained by
cells of the reticuloendothelial system (RES). It is
desirable to minimize this retention time (all references to
organ half-life or organ retention which follow refer
specifically to retention in the RES organs, principally liver
and spleen). Unfortunately, when the prior art included
higher molecular weight fluorocarbons in fluorocarbon
emulsions, organ retention times were also increased
considerably. Organ retention times for most fluorocarbons
bear an exponential relationship to the molecular weight of
the fluorocarbon and are critically dependent on dose and
animal species. See J.G. Riess, Artificial Organs 8: 44, 49-
51 (1984); J.G. Riess, International Symposium on Blood
Substitutes, Bari, Italy: Jun. 19-20, 1987, Proceedings pp.
135-166.
2156922
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There is a need for perfluorocarbon emulsions that do not
exhibit, cr exhibit reduced pulmonary gas-trapping properties,
and alsc have a short organ retention time. Accordingly, this
invention provides fluorocarbon emulsions having these
characteristics.
Summary of the Invention
The present invention involves fluorocarbon emulsions
which unexnectedly exhibit both reduced pulmonary gas-trapping
properties, and a short RES organ retention time.
Thus, in accordance with the present invention, there is
provided a fluorocarbon emulsion which has the fo,~~~lewing
properties: (1) the fluorocarbon component(s) has (have) a
vapor pressure at 37 degrees celsius of less than 2.67 kPa (20
torr) , preferably less than 1.33 kPa (10 torr) , and mcst
preferably less than 1.07 kPa (8 torr), in order to preclude
pulmonary gas-trapping; and (2) the fluorocarbon component (s)
has (have) organ half-lives significantly less than would be
predicted for their molecular weight, preferably less than
about 6 weeks, and more preferably less than about 3 to 4
weeks.
In one preferred embodiment, the emulsion comprises an
aqueous phase, an emulsifying agent, and a single low vapor
pressure, lipophilic fluorocarbon. It has been determined
that there are few fluorocarbons presently known which exhibit
the above stated characteristics. Several fluorocarbons which
appear suitable as a single lipophilic fluorocarbon component
to eliminate IPRV are listed in Table II, and include:
CF3 (CF2) BBr, (CF3) 2CF (CF2) 3CF (CF.,) CF2Br, F-octyl ethane and F-
bromoethers.
In another preferred embodiment, the fluorocarbon is a
mixture of two or more fluorocarbons (the "fluorocarbon
phase") The emulsion may contain a fluorocarbon composition
where the fluorocarbon phase comprises from about 50 o to about
99.9o w/w of a first fluorocarbon, and from about 0.1o to
about 501 w/w of a second fluorocarbon having a vapor pressure
less than the first fluorocarbon, and which includes at least
one lipophilic moiety. In parzicular, in the second
AMENDED SHEET
2156922
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fluorocarbon, the lipophilic moiety or moieties are
advantageouslv 3r, Cl, I, H, CHõ or a saturated or
unsaturated hydrocarbon chain of 2 or 3 carbon atoms. In one
preferred embodiment, the second fluorocarbon is an aliphatic
perfluorocarbon having the general formula CnFZn.,R or C.;FznR,,
wherein n is an integer from 9 to 12 and R is the lipophilic
moiety. In various preferred embodiments, the second
fluorocarbon is selected from the group consisting of
perf luorodecyl bromide, C,oF._CH=CH2 , or C, oF21CHzCH, , or -inear
or branched brominated perfluorinated alkyl ethers. Mosz
preferably, the second fluorocarbon comprises perfluorodecyl
bromide. It is desirable that each second fluorocarbon has a
molecular weight greater than about 550 Daltons. Pursuar.t to
an alternative definition of the second fluorocarbon, each
second fluorocarbon has a critical solution temperature in
hexane at least 10 C lower than that of a fully fluorinated
fluorocarbon having substantially the same molecular weich7-
(i.e., a molecular weight within 10, and preferably within 3,
4, or 5 daltons). In preferred emu,_sions, the discontinuous
fluorocarbon phase comprises from about 60 o to about 99 . 5% w/w
of the first fluorocarbon, and from about 0.5% to about 400
w/w of the second fluorocarbon; more preferably from about 60 0
to about 8 0 o w/w of the f i rst f luorocarbon, and from about 201
to about 40o w/w of the second fluorocarbon. The first
fluorocarbon component in these mixtures has a molecular
weight from about 460 to 550 Daltons, and has a half-life in
the organs of less than about 4 weeks, more preferab7 _y less
than about 2 or 3 weeks, and most preferably 7 days or less.
In particular, the fluorocarbon phase preferably comprises a
suitable mixture of perfluorooctyl bromide (PFOE, USA:'v
perflubron) and perfluorodecyl bromide (PFDB).
Focusing specifically on particular embodiments, one
aspect of the present invention is a fluorocarbon emulsion
exhibiting reduced pulmonary gas-trapping properties,
comprising an aqueous phase, an emulsifying agent, and a
liquid fluorocarbon phase having a vapor pressure of less than
about 2.67 kPa (20 torr) at 37 C, having an organ half-life of
AMENDED sHEET
2156922
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less than about 6 weeks, and having a lipophilic component,
the fluorocarbon phase comprising a mixture of at least two
fluorocarbons in a weight'ratio of from about 20:1 to about
i:20. Preferably, the fluorocarbon phase comprises a first
fluorocarbon having an organ half-life of less than about 4
weeks, and a second fluorocarbon having a vapor pressure less
than the first fluorocarbon. In one embodiment, the first
fluorocarbon has a molecular weight of about 460 te 550
Daltons, and the second fluorocarbon has a molecular weight of10 about 560 to
700 Daltons. In another embodiment, the
fluorocarbon phase has a vapor pressure at 37 C of less than
about 1.33 kPa (10 torr), preferably less than about 1.07 kP-=
( 8 tcrr ) .
In another embodiment, the invention is a fluorocarbon
emulsion exhibiting reduced pulmonary gas-trapping properties,
comprisi ng an aqueous phase, an emulsifier, and a fluorocarbon
phase including at least 10% weight by volume of F-decyl
bromide. In this emulsion, the fluorocarbon phase may
advantageously additionally comprise F-octyl bromide, and the
F-octyl bromide is preferably present in the fluorocarbor_
phase at about 45% to 800 or 90% weight per volume, and the F-
decyl bromide is present in the fluorocarbon phase at about i0
to 55% weight per volume.
Still another embodiment of the zresent invention is a
fluorocarbon emulsion exhibiting reduced pulmonary gas
trapping, comprising an aqueous phase, an emulsifier, and a
fluorocarbon phase consisting essentially of a single low
vapor pressure, lipophilic fluorocarbon having an organ half-
life of less than about 6 weeks, and a vapor pressure at 37 C
of less than 1.33 kPa (10 torr). Suitable fluorocarbons for
the fluorocarbon phase are F-octyl ethane and F-decyl ethane.
Preferably, the fluorocarbon has an organ half-life of less
than 3 to 4 weeks. In a preferred embodiment, the
fluorocarbon has a vapor pressure at 37 C of less than 1.07
kPa (8 torr). In another embodiment, the invention is a
method of preparing a fluorocarbon emulsion for intravenous
administration to a patient, by forming an emulsion of an
AMENDED SHEET
215 6 9,22
-6-
aqueous phase, an emulsifier, and a first fluorocarbon in a
fluorocarbon phase wherein the vapor pressure of zhe
fluorocarbon phase is greater than about 1.07 k?a (8 torr) at
37 C, the improvement comprising reducin~ the pulmonary gas
trapping effect of the emulsion upon intravenous
administration' by providing in combination with the first
fluorocarbon in the fluorocarbon phase an effective amount of
a second fluorocarbon, wherein the addition of the second
fluorocarbon reduces the vapor pressure of the fluorocarbon
phase at 37 C to less than about 1.07 kPa (8 torr), wherein
the fluorocarbon phase has a melting point less than about
37 C and an organ retention half-life less than about 4 weeks.
As above, the second fluorocarbon preferably includes a
lipophilic moiety, and more preferably is a bromcfluorocarbon.
Finally, the invention includes a method for
administering a fluorocarbon emulsion to a mammal, wherein the
emulsion comprises an aaueous phase, an emulsifier, and a
first fluorocarbon in a fluorocarbon phase wherein the vapor
pressure of the fluoracarbon phase is greater than about i.07
kPa (8 torr) at 37 C, and wherein the improvement comprises
reducing the pulmonary gas trapping effect of the emulsion
upon intravenous administration by providing in combinatior_
with the first fluorocarbon in the fluorocarbon phase an
effective amount of a second fluorocarbon, wherein the
addition of the second fluorocarbon reduces the vapor pressure
of the fluorocarbon phase at 37 C to less than about 1.07 kPa
(8 torr), wherein the fluorocarbon phase has a melting point
less than about 37 C=and an organ retention half-life less
than about 4 weeks.
As noted, one of the criteria for the emulsions of this
invention is that the fluorocarbon component(s) exhibit a
short organ retention time. One low vapor pressure lipophilic
fluorocarbon, perfluorodecyl bromide, for example, has a RES
half life in vivo of approximately 23 days, while those of
nonlipophilic perfluorocarbons having about the same molecular
weight vary from about 60 to 300 days (See Table I/Figure
AMENDED SHEET
7 2156922
7). This distinction is critical; it spells the difference between
formulations
which are physiologically acceptable and those which are not. Note that none
of
the prior art low vapor pressure fluorocarbons are lipophilic; thus, none
share the
advantageous properties of the present invention. For example, with reference
to
Table I and Figure 3, the fluorocarbons of the present invention all have
critical
solution temperatures (CSTs) and projected organ retention times much lower
than those of the prior art fluorocarbons of Davis, et al., Kabalnov, and
Meinert.
Aside from the fluorocarbons of the present invention, conventional
fluorocarbons
exhibit a direct correlation between retention time in RES organs and
molecular
weight. Also, aside from the lipophilic fluorocarbons used in the present
invention,
the perfluorochemical structure has little effect on the strong retention
time/molecular weight relationship. Thus, the presence of heteroatoms or
cyclic
structure has little effect on organ retention time.
A particularly preferred emulsifier for use in the present invention is egg
yolk phospholipid, and preferred amounts of this emulsifier are 1% -10% w/v.
Also
preferred are the fluorinated surfactants.
According to an aspect of the invention, there is provided a fluorocarbon
emulsion exhibiting reduced pulmonary gas-trapping properties, comprising:
an aqueous phase;
an emulsifying agent; and
a liquid fluorocarbon phase having a vapor pressure of less than about
2.67 kPa (20 torr) at 37 C, having an organ half-life of less than about 6
weeks,
and having a lipophilic component, said fluorocarbon phase comprising a
mixture
of at least two fluorocarbons in a weight ratio of from about 20:1 to about
1:20.
According to another aspect of the present invention, there is provided a
fluorocarbon emulsion exhibiting reduced pulmonary gas-trapping properties,
comprising:
an aqueous phase;
an emulsifier; and
a fluorocarbon phase including at least 10% weight by volume of F-decyl
AL bromide.
CA 02156922 2005-12-01
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According to another aspect of the present
invention, there is provided a fluorocarbon emulsion
exhibiting reduced pulmonary gas trapping, comprising:
an aqueous phase;
an emulsifier; and
a fluorocarbon phase consisting essentially of a
single low vapor pressure; fluorocarbon phase having an
organ half-life of less than about 6 weeks, and a vapor
pressure at 37 C of less than 1.33 kPa (10 torr).
According to another aspect of the present
invention, there is provided a method of preparing a
fluorocarbon emulsion for intravenous administration to a
patient, by forming an emulsion of an aqueous phase, an
emulsifier, and a first fluorocarbon in a fluorocarbon
phase wherein the vapor pressure of the fluorocarbon
phase is greater than about 1.07 kPa (8 torr) at 37 C,
the improvement comprising:
reducing the pulmonary gas trapping effect of the
emulsion upon intravenous administration by providing in
combination with the first fluorocarbon in the
fluorocarbon phase an effective amount of a second
fluorocarbon, wherein the addition of the second
fluorocarbon reduces the vapor pressure of the
fluorocarbon phase at 37 C to less than about 1.07 kPa (8
torr), wherein the fluorocarbon phase has a melting point
less than about 37 C and an organ retention half-life
less than about 4 weeks.
According to a further aspect of the present
invention, there is provided use of a first fluorocarbon
in combination with an effective amount of a second
fluorocarbon to reduce the pulmonary gas trapping effect
of a fluorocarbon emulsion in a mammal, wherein the
emulsion comprises an aqueous phase, an emulsifier, the
first fluorocarbon in a fluorocarbon phase wherein the
vapour pressure of the fluorocarbon phase is greater than
about 1.07 kPa (8 torr) at 37 C, and the effective amount
of the second fluorocarbon wherein the second
CA 02156922 2005-12-01
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fluorocarbon reduces the vapour pressure of the
fluorocarbon phase at 37 C to less than about 1.07 kPa (8
torr), wherein the fluorocarbon phase has a melting point
less than about 37 C and an organ retention half-life
less than about 4 weeks.
According to a yet further aspect of the present
invention, there is provided a medicament for use in
reducing the pulmonary gas trapping effect of a
fluorocarbon emulsion comprising an aqueous phase, an
emulsifier, and a first fluorocarbon in a fluorocarbon
phase, wherein the vapor pressure of said fluorocarbon
phase is greater than about 1.07 kPa (8 torr) at 37 C,
the improvement comprising:
an effective amount of a second fluorocarbon in
combination with said first fluorocarbon, wherein the
second fluorocarbon reduces the vapor pressure of the
fluorocarbon phase at 37 C to less than about 1.07 kPa (8
torr), wherein the fluorocarbon phase has a melting point
less than about 37 C and an organ retention half-life
less than about 4 weeks.
Brief Description of the Drawings
FIG. 1 is a graph which illustrates the increase in
lung volume which occurs in rats as a result of pulmonary
gas trapping following intravenous administration at a
dose of 5.4 g PFC/kg. The formulations tested are
concentrated (90% w/v) fluorocarbon emulsions stabilized
by 4% egg yolk phospholipid. The conversion factor for
torr to kPa is 1 torr = 0.13329 kPa.
FIG. 2 is a graph which illustrates the increase in
lung volume which occurs in rabbits as a result of
pulmonary gas trapping following intravenous
administration at a dose of 5.4 g PFC/kg. The
formulations tested are concentrated (90% w/v)
fluorocarbon emulsions stabilized by 4% egg yolk
phospholipid.
2156922
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FIG. 3 represents a plot of fluorocarbon molecular weight
(g/mol) versus critical solution temperature in hexane ( K)
for various fluorocarbons including the prior art emul-,--ion
stabilizers proposed :y Davis, Meinert, and Kabalnov.
F IG. 4 is a plot illustrating the organ half -life in days
vs. molecular weight of various fluorocarbons in g/mol. I'he
plot includes a lower molecular weight cutoff which is rela--ed
to the formation of gas emboli for fluorocarbons with vapor
pressures greater than 2.67 kPa (20 torr). The plot also
includes an upper molecular weight cutoff which is related tlo
compounds having organ retention times of less than 4 weeks.
FIG. 5 is a plot illustrating the oraan half-life in days
vs. molecular weight cf various fluorocarbons in g/mol. The
plot includes a lower molecular weight cutoff of 520 g/mol to
take into account pulmonary gas trapping (i.e. limit to less
than 1.07 kPa (8 torr)).
FIG. 6 is a graph of fluorocarbon vapor pressure in tcrr
at 37 degrees celsius for various mole fractions in mix-:ures
of perfiucrooctyl bromide (PFOB) and perfluorodecyl hromide
(PFDB).
FIG. 7 is a table listing various properties of
fluorocarbons.
Descrintion of the Preferred Embodiments
I. Introduction
The fluorocarbon emulsions of the present invention
comprise two phases: a continuous aqueous phase and a
discontinuous fluorocarbon phase. Osmotic agents and buffers,
generally, are also included in the continuous phase to
maintain .osmolality and pH to promote physiological
acceptability.
The discontinuous phase of modern fluorocarbon emulsions
for therapeutic use generally comprises from 20% w/v to up to
125% w/v of a fluorocarbon or a highly fluorinated compound
(hereinafter referred as a "fluorocarbon" or a
"perfluorocarbon"). As used herein, the expression "weight
per volume" or "w/v" will mean grams per 100 cubic centimeters
or milliliters.
AMENDED SHEET
2156922
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The present invention provides a fluorocarbon emulsion
which exhibits reduced pulmonary gas-trapping properties, and
which has a short organ retention time.
In the first instance, in order to reduce pulmonary gas-
trapping, it is desired that the fluorocarbon emulsion include
a fluorocarbon, or mixture thereof, which has a vapor pressure
of less than 2.67 kPa (20 torr) , and most prererably less than
1.07 kPa (B torr).
Further, in order to prevent long body retention time, iz-
is desired that the single fluorocarbon be lipophilic.
Alternatively, as stated above, the emulsion may comprise a
mixture of fluorocarbons in which a second fluorocarbon is
added to a first, the second fiuorocarbon having a relatively
higher molecular weighz~ and lower vapor pressure, and includes
in its molecular structure a lipophilic moiezy. In such form,
emulsions of the present invention will exhibit reduced IPRV.
II. The Compositions
A. The Fluorocarbon
The characteristics of fluorocarbons suitable for use in
the present invention are discussed in more detail below.
Examzles of suitable fluorocarbons are provided.
1. The fluorocarbon which is to be administered in
emulsion form is chosen in order to prevent or reduce
pulmonary gas-trapping. It has previously been found thaz
intravascular administration of fluorocarbon emulsions having
vapor pressures of around 3.99 kPa (30 torr) cause gas/vapor
microbubble intravascular embolism. in order to prevent this
effect, it is desired that the fluorocarbon have, in the first
instance, a vapor pressure of less than about 2.67 kPa (20
torr).
Referring to Figures 1 and 2, the effect of vapor
pressure of the administered fluorocarbon upon pulmonary gas-
trapping (PGT) is illustrated in rats and rabbits. As is
clearly seen, there is an increase in PGT once the vapor
pressure of the fluorocarbon exceeds approximately 1.07 kPa (S
torr). At intermediate vapor pressure levels, such as 1.60-
AMENDED SHEET
ti15~9a~
-10- :
1.73 kPa (12-13 torr), it has been found that gas/vapcr
intravascular emboli does not occur, however, a larger degree
of increased pulmonary residual volume (IPRV) occurs. ?t is
therefore desired that any fluorocarbon used in such a
fluorocarbon emulsion have a vapor pressure of less than about
2.67 kPa (20 torr) and it is preferred that the vapor
pressure be less than 2.00, 1.86, or 1.73 kPa (15, 14, or 13
torr) , and more preferedly that the vapor pressure be less
than about 1. 6 0, 1.46 or 1.33 kPa (12 , 11, or 10 t orr ), and
most preferedly that the vapor pressure be less than 1.20,
1.06, or .931 kPa (9, 8, or 7 torr).
As stated abeve, however, vapor pressure as rela--ed to
IPRV is not the sole criteria for selecting the fluorocarbon.
In particular, it is desired that the fluorocarbon have _
short body retention time. Preferably, the half-life of the
fluorocarbon in organs is less than 6 weeks, and most
preferedly that the half-life is less than 3 to 4 weeks.
For single fluorocarbons, the fluorocarbon comzonent must
have a low vapor pressure and be lipophilic. Possible
alternatives include those listed in Table I and Figure 7,
although other low vapor pressure, lipophilic fluorocarbens
can be contemplated. Figures 4 and 5 illustrate the
relationship _between the molecular weight of various
fluorocarbons and their half life time in days.
For mixtures of fluorocarbons, the first fluorocarbon
may be selected from the list below. Such fluorocarbons must
have a molecular weight of less thar_ about 550 Daltons, and
include bis (F-alkyl) ethenes such as C,FoCH=CHC4F, (11 F-44E" ),
CF3CF9CH=CHC6F13 ("F-i36E" ), and cyclic fluorocarbons, such as
C1eFla (F-decalin, perfluorodecalin or FDC) ; F-adamantane (FA) ;
perfluoroindane; F-methyladamantane (FMA); F-1,3-
dimethyladamantane (FDMA); perfluoro-2,2,4,4-
tetramethylpentane; F-di- or F-tri-methylbicyclo(3,3,1]nonane
(nonane); C7 _12 perfluorinated amines, such as F-
tripropylamine, F-4-methyloctahydroquinolizine (FMOQ), F-N-
methyl-decahydroisoquinoline (FMIQ), F - n -
AMENDED SHEET
~15692~
-il-
methyldecahydroquinoline (FHQ), and F-N-cyclohexylpyrrolidine
( FCHP ) .
Other examples of appropriate first fluorocarbons include
brominated perfluorocarbons, such as perfluorooc*_yl bromide
(CBFI,Br, USAN perflubron), 1-bromopentadecafluoroheptane
(C,F,SBr) , and 1-bromotridecafluorohexane (CEF33Br, also known
as perfluorohexyl bromide or PFHB). Other brominated
fluorocarbons are disclosed in U.S. Patent Nos. 3,975,512 and
4,987,154 to Long.
Also contemplated are first fluorocarbons having other
nonfluorine substituents, such as I-chloro-
heptadecafluorooctane (C8FõCl, also referred to as
perfluorooctyl chloride or Pr~OC1); perfluorooctyl hydride, and
similar compounds having different numbers of carbon atoms.
Additional first fluorocarbons contemplated in accordance
with this invention include perfluoroalkylated ethers,
halogenated ethers (especially brominated ethers), or
polyethers, such as ( CF3 ) 2CFO ( CF2CF2 ) .,OCF ( CF3 ) ( CyF~ ) ,O .
Further, fluorocarbon-hydrocarbon compounds may be used, such
2 0 as, for example compounds having the general formula CnF~n_-
Cn, H2n, tl ; CrF2n_,OCn, H,n, _, ; or CnF2n iCH=CHCn, H2n. 1, wherein n and
n'
are the same or different and are from about 1 to about 10 (so
long as the compound is a liquid at room temperature). Such
compounds, for example, include CBFõC2H5 and CF.;CH=CHCGH,;.
Particularly preferred fluorocarbons for use as the firsl---
fluorocarbon include perfluoroamines, terminally substituted
linear aliphatic perfluorocarbons having the general
structure:
CF2n,1R,' wherein n is an integer from 6 to 8 and R
comprises a lipophilic moiety selected from the group of
Br, Cl, I, CH3, or a saturated or unsaturated hydrocarbon
of 2 or 3 carbon atoms,
bis (F-alkyl) ethenes having the general structure:
C,F2ny,-CH=CH-Cn.F2n',l, wherein the sum of n and n' equals
6 to 10, and
perfluoroethers having the general structure:
AMENDED SHEET
2156922
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CõF2n,, - O - Cn, F2n'f1, wherein the sum of n and n' equals 6 to
9.
In addition, fluorocarbons selected from the general
groups of perfluorocycloalkanes or perfluoroalkyl-
cycloalkanes, perfluoroalkyl saturated'neterocyclic compounds,
or perfluorotertiary amines may be suitably utilized as the
first fluorocarbon. See generally Schweighart, U.S. Patent
No. 4,866,096.
It will be appreciated that esters, thioethers, and other
variously modified mixed fluorocarbon-hvdrocarbon compounds,
including isomers, are also encompassed within the broad
definition of fluorocarbon materials suitable for use as the
first fluorocarbon of the present invention. Other suitable
mixtures of fluorocarbons are also contemolated.
Additional fluorocarbons not listed here, but having the
properties described in this disclosure that would lend
themselves to therapeutic applications, are also contemplated.
Such fluorocarbons may be commercially available or specially
prepared. As will be appreciated by one skilled in the art,
there exist a variety of methods for the preparation of
fluorocarbons that are well known in the art. See for
example, Schweighart, U.S. Patent No. 4,895,876.
The second fluorocarbon is preferably an aliphatic
fluorocarbon substituted with one or more lipophilic meieties
and having a higher molecular weight and lower vapor pressure
than the first fluorocarbon. Advantageously, the lipophilic
5 moiety is a terminal substitution on the fluorocarbon
molecule. Preferably, the molecular weight of the second
fluorocarbon is greater than about 540 Daltons. Constraints
on the upper limit of the molecular weight of the second
fluorocarbon will generally be related to its organ retention
10 time and its ability to be solubilized by the first
fluorocarbon. Usually, the second fluorocarbon has a
molecular weight less than about 700 Daltons.
Most preferred second fluorocarbons have boiling points
greater than about 150 C and water solubilities of less than
15 about 1X10"9 moles/liter.
AMENDED SHEET
2156922
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Of course, as will be appreciated by one skilled in the
art, many fluorocarbons substituted with different lipophilic
groups could be suitably used as the second fluorocarbon in
the present invention. Such fluorocarbons may include esters,
thioethers, and various fluorocarbon-hydrocarbon compounds,
including isomers. Mixtures of two or more fluorocarbons
satisfying the criteria set forth herein are also encompassed
within the broad definition of fluorocarbon materials suitable
for use as the second fluorocarbon of the present invention.
Fluorocarbons not listed here, but having the properties
described in this disclosure that would lend themselves to
therapeutic applications are additionally contemplated.
The lipophilic moietv is optimally selected from the
group consisting of Br, Cl, I, CH3, or a saturated or
unsaturated hydrocarbon of 2 or 3 carbon atoms. Consecuently,
preferred second fluorocarbons may be selected from the group
of terminally substituted perfluorocarbon halides as
represented by the general formula:
C;F2n_:.X or C,F2nX' wherein r: is 8 or greater,
preferably 10 to 12, and X is a halide selected
from the group consisting of Br, Cl, or I;
1-alkyl-perfluorocarbons or dialkylperflucrocarbons as
represented by the general formula:
CnF2ny,- (CH2) n,CH3 wherein n is 8 or greater,
preferably 10 to 12, and n' is 0 to 2;
i-alkenyl-perfluorocarbons as represented by the general
formula:
CnF2n,1-Cn,H12n,_1, , wherein n is 10 or more, preferably
10 to 12, and n' is either 2 or 3; or
brominated linear or branched perfluoroethers or polyethers
having the following general structure:
Br- (CnF2n,i-O-Cn,F2n-,1) , wherein n and n' are each at
least 2 and the sum of n and n' is greater than or
equal to E.
Most preferably, the second fluorocarbon of the present
invention is selected from the group consisting of linear or
branched brominated perfluorinated alkyl ethers,
AMENDED SHEET
2156922
-14-
perfluorodecyl bromide (CyoF,1Br); perfluorododecyl bromide
( C,2F,SBr ) ; i -perfluorodecylethene ( C10F z,CH=CH.) ; and
1-perfluorodecylethane ( C1OF,,CH~CH3 ); with perf luorodecyl
bromide particularly preferred.
In accordance with a first alternative definition,
whether cr not they satisfy the foregoing definitions,
fluorocarbons having critical solution temperatures (CSTs) vs
hexane more than 100C below the CST of a fluorocarbon having
substantially the same molecular weight (variations of up to
about 10 daltons being acceptable) are also suitable for use
in the present invention. A comparison between the CST and
molecular weight of a number of perfluorocarbons is presented
in Table I. Methodology for determining CST is presented in
Example 2.
Specifically, it has been found that a mixture of F-octyl
bromide and F-decvl bromide satisfies the above stated
requirements. In particular, a fluorocarbon phase which
includes at least 10o wt/v of F-decyl bromide is pre=erred.
Most preferably, the fluorocar'oon phase includes F-octyl
bromide at about 45% to 800 or 90% wt/v, and the F-decyl
bromide is nresent in the fluorocarbon phase at about 10 to
551 wt/v.
AMENDED SHEET
2156922
-15-
TABLE I
Physical Properties of Minor Components Discussed in Literature
(Proposed Minor Components are listed in Boldface)
Name Formula MW(g/mol) b.p.(C) CSTH(C) tõ2
(days)
- ---- - -- - ----------- - ---- - ------------ - -
Davis, et al. (U.S. Patent No. 4,859,363)
F-perhydrofluorene Ci3F22 574 192-193 n.a. n.a.
F-perhydrophenanthrene C14F'4 624 215-216 48 n.a.
F-pe rhy d rofi u o ra nthen e C16F26 686 242-243 n.a. n.a.
Kabalnov, et al. (Kolloidin Zh. 48:27-32(1986))
F-N-methylcyclohexylpiperidine C.zFz,N 557 n.a. 40 60
Meinert (U.S. Patent No. 5,120,731); note these values are calculated, not
measured.
F-N-cyclohexylmorpholine C,oF18N0 492 n.a. 31 13
F-dimorpholinoethane C,0F20N202 560 164 38 24
F-dimorpholinopropane C.,FZ2N2Oz 610 182 45 50
F-dimorpholinopentane C13F26N2O2 710 215 60 280
F-dipiperidine C.oF,sNZ 452 145-150 36 24
F-dipiperidinomethane C.,F18N2 502 165-175 42 55
F-dipiperidinoethane C.2F2ON2 552 181-186 49 124
F-dipiperidinopropane C,3F,NZ 602 195-203 56 282
F-dipiperidinobutane C14F24N2 652 231-238 72 1460
Present Invention
F-decalin C,oF18 462 142 22 7
F-hexyl bromide C6F13Br 399 n.a. n.a. 2
F-octyl bromide CeFõBr 499 143 (-19)a 4
F-decyl bromide CJztBr 599 (198) (<0)a 23
F-bromopolyether CõF23O3Br 697 n. a. 32 30
a values for the critical solution temperature with hexane are estimated from
extrapolations linear plots of the
critical solution temperature vs. hydrocarbon chain length.
b the value of the boiling point of F-decyl bromide is estimated from
Hildebrand solution theory.
AMENDED SHEET
2156922
-16-
B. The Emulsifvina Aaent
The fluorocarbon emulsion also includes an emulsifying
agent. As used in this specification, an emulsifying agent
is any compound or composition t hat aids in the formation and
maintenance of the droplets cf the discontinuous phase bv
forming a layer at the interface between the discontinuous
and continuous phases. The emulsifying agent may comprise a
single compound or any combination of compounds, such as in
the case of co-surfactants.
In the present invention, preferred emulsifying agents
are selected from the group consisting of phospholipids,
nonionic surfactants, fluorinatea surfactants, w'rlich can be
neutral or anionic, and combinations of such emulsifying
agents.
Lecithin is a phospholipid that has frequently been used
as a fluorocarbon emulsifying agent, as is more fullv
described in U.S. Patent No. 4,865,836. Egg yolk
phospholipids have shown great promise as emulsifying agents
for fluorocarbons. See e.g., Long, U.S. Patent No.
4,987,154.
Other emulsifying agents may be used with good effect,
such as fluorinated surfactants, also known as
fluorosurfactants. Fluorosurfaczants that can provide stable
emulsions include triperfluoroalkylcholate;
perfluoroalkylcholestanol; perfluoroalkyloxymethylcholate;
C3F70(CFz)3C(=O)NH(CH2)3N(O) (CH3) 2 (XMO-10) ; and fluorinated
polyhydroxylated surfactants, such as, for example, those
discussed in "Design, Synthesis and Evaluation of
Fluorocarboas and Surfactants for In Vivo Applications New
Perfluoroalkylated Polyhydroxylated Surfactants" by J.G.
Riess, et al., Biomat. Artif. Cells Artif. Organs 16: 421-430
(1988).
The nonionic surfactants suitable for use in the present
invention include polyoxyethylene-polyoxypropylene
copolymers. An example of such class of compounds is
Pluronic, such as Pluronic F-68. Anionic surfactants,
particularly fatty acids (or their salts) having 12 to 24
AMENDED SHEET
2156922
-17-
carbon atoms, may also be used. One example of a suitable
anionic surfactant is oleic acid, or its salt, sodium oleate.
It will be appreciated that choice of a particular
emulsifying aaent is not central to the present inventior..
Indeed, virtually any emulsifying agent (including thcse
still to be developed) capable of facilitating formation cf
a fluorocarbon-in-water emulsion can form improved emulsions
when used in the present invention. The optimum emulsifying
agent or combination of emulsifying agents fcr a give:-.
application may be determined through empirical studies that
do not reauire undue experimentat-on. Consequently, one
practicing the art of the present invention shcu~-d choose the
emulsifying aaent or combination of emulsifying aaents for
such propert;_es as biocompatibility.
C. The Continuous Phase
The continuous phase comprises an aqueous meaium.
Preferably, the medium is physiologically acceptable. For
instance, a preferred emulsion will have the ability tc
buffer and maintain pH, as well as provide an a~propriat=
osmolality. This typically has been achieved in the art
through the inclusion in the aqueous phase of one or more
conventional buffering and/or osmot--c agents, or an aaent
that combines these properties.
Additionally, one may supplement the continuous phase
with other agents or adjuvants for stabilizing or otherwise
increasing the beneficial aspects ef the emulsion. These
agents or adjuvants include: cholesterol, tocopherols,
and/or mixtures or combinations thereof.
D. Preoaration of.the Emulsion
Fluorocarbon emulsions according to the invention are
prepared by means of conventional emulsification procedures,
such as, for example, mechanical or ultrasonic emulsification
of an emulsion formulation in a Manton-Gaulin mixer cr
Microfluidizer (Microfluidics Corp., Newton, MA) as described
in Example 1.
The single fluorocarbon, or the first and second
fluorocarbons, are combined with the aqueous phase in the
AMENDED SHEET
21,5fi922
-1 s-
desired ratios, together with the surfactant. Usually, a
pre-emulsion mixture is prepared bv simple mixing or blending
of the various components. This pre-emulsion is then
emulsified in the desired emulsification.apparatus.
when a composition of fluorocarbons is used, the second
fluorocarbon can comprise from about 0.1o to 50% (w/w) of the
total amount of fluorocarbon; in preferred embodiments, the
second fluorocarbon comprises from about 0.5% to about 40%
(w/w) of the total amount of fluorocarbon, with the first
flucrocarbon comprising the remainder of the tetal
fluorocarbon. The combined fluorocarbon concentration in the
emulsion is preferably anywhere within the range of about 20%
to about 125% (w/v). In preferred emulsions, the total
perfluorocarbon concentration is from about 30%, 400, cr 50%
to about 701, 80%, 90%, or 100 0(w/v) . Emulsifiers are added
in concentrations of from about 0.1% to 10%, more preferably
lo or 2% to about 6% (w/v).
EXAMPLE I
Preoaration of Reference Emulsion
Comnosition of Reference Emulsion: Perflubron/Lecithin
( 90 /4 o w/v)
A reference emulsion containing 90 g PFOE, 4 g egg yolk
phospholipid (EYP) , and physiological levels of salts and
buffers was prepared by high pressure homogenization
according to the method of Long (U.S. Patent No. 4,987,154).
EXAMPLE 2
Measurement of Critical Solution Temperature (CST)
Critical solution temperature for fluorocarbon liquids
was measured in the following manner: Equivolume mixtures of
the test fluorocarbon and hydrocarbon (e.g., hexane) are
placed in a sealed vial and submerged in a temperature
controlled water bath. Samples are cooled until two distinct
phases are present. At this point, the temperature is
increased slowly. The lowest temperature at which the two
AMENDED SHEET
~1~6922
-19-
phases are comzletely miscible (i.e., a single liquid phase)
is defined as the CST.
For comparison purposes, all CST temperatures used in
this patent are reported versus hexane. It is often not
possible, however, to measure the CST for lipophilic
fluorocar~Dons versus hexane, since the CSTs for these
substances are very low. Thus, the CST for lipophilic
substances is often measured in longer chain length
hydrocarbons, and the value versus hexane is determined via
extrapolation of linear plots of CST vs. alkane chain length.
Further, several other second fluorocarbons are
considered similary acceptable. In particular, it appears
that perfluorobromoethers, perfluorooctylethane (PFOE),
perfluorononyl bromide, perfluorooctyl ethane, and cther
compounds selected from the group of alkyl-perfluoro-alkanes
(such as CeF_,C2H5 and C1oF21C2F5) either individually or in
mixtures, are believed suitable.
In any case, the second fluorocarbon is chosen such that
when mixed wich the first fluorocarbon in appropriate ratios,
it eliminates pulmonary gas trapping (i.e. the fluorocarbon
phase has a vapor pressure of less than 2.67 kPa (20 torr),
and preferably less than 1.07 kPa (8 torr), and has an organ
half-life of about 3 to 4 weeks. It is possible to derive
acceptable compositions through calculation of the vapor
pressure of the mixture of fluorocarbons with Raoult's law,
as was done in Figure 6, or by determ;ining the vapor pressure
empirically.
EXAMPLE 3
Effect of Vapor Pressure on IPRV
Figures 1 and 2 illustrate the effect of vapor pressure
on IPRV in rats and rabbits respectively. It is clear that at
vapor pressures less than about 1.07 kPa (8 torr) IPRV is
substantially reduced. Further, as illustrated in Figure 6,
mixtures of 60% w/v PFOB and 30% w/v PFDB obey Raoult's law
and have a vapor pressure of about 1.07 kPa (8 torr). These
mixtures are able to effectively decrease IPRV to levels
AMENDED SHEET
2t56922
-20-
observed for single fluorocarbons with vapor pressures of
about .013 kPa (0.1 torr).
Although the present invention has been di sclosed in the
context of certain preferred embodiments, it is intended that
the scope of the invention be measured by the claims that
follow, and not be limited to those preferred embodiments.
AMENDED SHEET
