Field of the Invention
[0001] This invention describes the new use of an agent selected from the group consisting
of anti-inflammatory agents, anti-thrombotic agents, anti-platelet agents, fibrinolytic
agents, lipid reducing agents, direct thrombin inhibitors, and glycoprotein IIb/IIIa
receptor inhibitors for the manufacture of a medicament for lowering the risk of a
future cardiovascular disorder associated with atherosclerotic disease in an individual,
characterised in that said individual has no signs or symptoms of disease, has been
identified as likely to benefit from treatment with the agent in a method comprising
comparing a level of c-reactive protein obtained from the individual to a predetermined
value, wherein the predetermined value is about 1¾ mg/l of blood or higher and the
level of c-reactive protein in comparison to said predetermined value is indicative
of whether the individual will benefit from treatment with said agent, but the individual
is otherwise without coronary risk factors.
Background of the Invention
[0002] Despite significant advices in therapy, cardiovascular disease remains the single
most common cause of morbidity and mortality in the developed world. Thus, prevention
of cardiovascular disorders such as myocardial infarction and stroke is an area of
major public health importance. Currently, several risk factors for future cardiovascular
disorders have been described and are in wide clinical use in the detection of individuals
at high risk. Such screening tests include evaluations of total and HDL cholesterol
levels. However, a large number of cardiovascular disorders occur in individuals with
apparently low to moderate risk profiles, and our ability to identify such patients
is limited. Moreover, accumulating data suggests that the beneficial effects of certain
preventive and therapeutic treatments for patients at risk for or known to have cardiovascular
disorders differs in magnitude among different patient groups. At this time, however,
data describing diagnostic tests to determine whether certain therapies can be expected
to be more or less effective are lacking.
[0003] Certain cardiovascular disorders, such as myocardial infarction and ischemic stroke,
are associated with atherosclerosis. The mechanism of atherosclerosis is not well
understood. While inflammation is hypothesized to play a role in the initiation and
progression of atherosclerosis. clinical data have not established whether inflammation
increases, or anti-inflammatory treatments decrease, the risk of cardiovascular disorders
associated with atherosclerosis.
[0004] C-reactive protein is a marker for underlying systemic inflammation. Elevated levels
of C-reactive protein have been described among patients with acute ischemia or myocardial
infarction, and predict episodes of recurrent ischemia among those hospitalized with
unstable angina. Further, plasma concentration of C-reactive protein is associated
with risk of myocardial infarction among unhealthy patients, such as those with symptomatic
angina pectoris. Plasma concentration of C-reactive protein also is associated with
fatal, but not nonfatal, coronary heart disease among smokers with multiple risk factors
for atherosclerosis. However, since levels of C-reactive protein increase following
acute ischemia and are directly related to cigarette consumption, it has been uncertain
whether statistical associations observed in these prior studies of acutely ill or
high-risk populations are causal, are due to short-term inflammatory changes or are
due to interrelations with other risk factors, in particular, smoking and hyperlipidemia.
Summary of the Invention
[0005] This invention relates to the use of an agent selected from the group consisting
of anti-inflammatory agents, anti-thrombotic agents, anti-platelet agents, fibrinolytic
agents, lipid reducing agents, direct thrombin inhibitors, and glycoprotein IIb/IIIa
receptor inhibitors for the manufacture of a medicament for lowering the risk of a
future cardiovascular disorder associated with atherosclerotic disease in an individual,
characterised in that said individual has no signs or symptoms of disease, has been
identified as likely to benefit from treatment with the agent in a method comprising
comparing a level of c-reactive protein obtained from the individual to a predetermined
value, wherein the predetermined value is about 1¾ mg/l of blood or higher and the
level of c-reactive protein in comparison to said predetermined value is indicative
of whether the individual will benefit from treatment with said agent, but the individual
is otherwise without coronary risk factors.
[0006] It has been discovered that elevated levels of C-reactive protein are predictive
of future cardiovascular disorders in individuals without other coronary risk factors.
For example elevated levels of C-reactive protein in apparently healthy, nonsmokers
without other coronary risk factors are predictive of an increased risk of myocardial
infarction. As another example, contrary to suggestions in the prior art, elevated
levels of C-reactive protein in otherwise healthy smokers without other coronary risk
factors are predictive of an increased risk of a nonfatal myocardial infarction. As
still another example, elevated levels of C-reactive protein in individuals without
other coronary risk factors are predictive of an increased likelihood of a future
stroke.
[0007] It has been discovered also that the likelihood that certain individuals will benefit
to a greater or a lesser extent from the use of certain therapeutic agents for reducing
the risk of a future cardiovascular disorder can be determined from the base-line
level of C-reactive protein in an individual without other coronary risk factors.
[0008] It further has been discovered that the predictive value of C-reactive protein is
independent of other predictors. Thus, the level of C-reactive protein does not simply
duplicate that which is measured when levels of cholesterol are measured.
[0009] Thus, the invention provides the use of an agent selected from the group consisting
of anti-inflammatory agents, anti-thrombotic agents, anti-platelet agents, fibrinolytic
agents, lipid reducing agents, direct thrombin inhibitors, and glycoprotein IIb/IIIa
receptor inhibitors for the manufacture of a medicament for lowering the risk of a
future cardiovascular disorder associated with atherosclerotic disease in an individual,
characterised in that said individual has no signs or symptoms of disease, has been
identified as likely to benefit from treatment with the agent in a method comprising
comparing a level of c-reactive protein obtained from the individual to a predetermined
value, wherein the predetermined value is about 1¾ mg/l of blood or higher and the
level of c-reactive protein in comparison to said predetermined value is indicative
of whether the individual will benefit from treatment with said agent, but the individual
is otherwise without coronary risk factors.
[0010] Preferred aspects of the invention are set out in dependent claims 2-7 below.
[0011] A preferred agent is aspirin. To practice the inventive use the level of C-reactive
protein in an individual without other coronary risk factors is obtained. This level
then is compared to a predetermined value, wherein the level of C-reactive protein
in comparison to the predetermined value is indicative of the likelihood that the
individual will benefit from treatment with the agent. The individual then can be
characterized in terms of the net benefit likely to be obtained by treatment with
the agent.
[0012] In preferred embodiments, the individual is apparently healthy. In certain embodiments,
the individual also is a nonsmoker.
[0013] The predetermined value of C-reactive protein is about 1 3/4 mg/l of blood. A preferred
predetermined value is about 2 mg/l of blood.
[0014] As mentioned above, the invention is particularly adapted to determining which individuals
will preferentially benefit from treatment with an agent for reducing the risk in
the individuals of a cardiovascular disorder such as a future stroke or a future myocardial
infarction, including nonfatal myocardial infarctions. It also permits selection of
candidate populations for clinical trials and for treatment with candidate drugs,
by identifying, for example, the individuals most likely to benefit from a new treatment
or from a known treatment with a high risk profile of adverse side effects. Thus,
the invention provides information for evaluating the likely net benefit of certain
treatments for candidate patients.
[0015] The invention also involves a use of anti-inflammatory therapies for the manufacture
of a medicament for treating subjects to prevent cardiovascular disorders. An anti-inflammatory
agent is administered to a subject who has an above-normal level of C-reactive protein,
but who is otherwise free of symptoms calling for an anti-inflammatory agent. The
anti-inflammatory agent is administered in an amount effective to lower the risk of
the subject developing a future cardiovascular disorder. The preferred subjects are
apparently healthy subjects free of current need for anti-inflammatory treatment,
such as free of symptoms of rheumatoid arthritis, chronic back pain, autoimmune diseases,
and the like, and without other coronary risk factors apart from C-reactive protein.
[0016] These and other aspects of the invention will be described in more detail below in
connection with the detailed description of the invention.
Brief Description of Drawings
[0017]
Figure 1 is a graph demonstrating the relative risk of first myocardial infarction
in the study population according to baseline level of C-reactive protein. Data are
shown for all study subjects and/or non-smokers.
Figure 2 is a graph demonstrating relative risks (and 95 percent confidence interval)
of first myocardial infarction associated with each increasing quartile of baseline
C-reactive protein, according to year of study follow-up.
Figure 3 is a graph demonstrating relative risks of first myocardial infarction associated
with baseline levels of C-reactive protein, stratified by randomized assignment to
aspirin or placebo therapy. Analyses are limited to events occurring prior to unblinding
of the aspirin component of the Physicians' Health Study. The reduction in risk of
myocardial infarction associated with aspirin use was 13.9 percent in the first (lowest)
quartile of C-reactive protein, 33.4 percent in the second quartile, 46.3 percent
in the third quartile, and 55.7 percent in the fourth (highest) quartile.
Figure 4 is a graph demonstrating the distribution of levels of C-reactive protein
in the population studied in Example. 1.
Figure 5 is a graph demonstrating the normal bell curve distribution which occurs
when the C-reactive protein levels of Fig. 3 are log normalized.
Detailed Description of the Invention
[0018] The primary basis for this invention is evidence from the Physicians' Health Study,
a large scale, randomized, double-blind, placebo controlled trial of aspirin and beta-carotene
in the primary prevention of cardiovascular disease conducted among 22,000 apparently
healthy men. In that trial, baseline level of C reactive protein, a marker for underlying
systemic inflammation, was found to determine the future risk of myocardial infarction
and stroke, independent of a large series of lipid and non-lipid risk factors. Specifically,
individuals with the highest baseline levels of C-reactive protein were found to have
3 fold increases in risk of developing future myocardial infarction and 2 fold increases
in risk of developing future stroke, (Fig. 1).
[0019] In this trial, the predictive value of C-reactive protein was present for non-fatal
as well as fatal events, was stable over long periods of time, and was present for
non-smokers as well as smokers. Further, data from this trial indicate that the magnitude
of benefit that apparently healthy individuals can expect from prophylactic aspirin
is dependent in large part upon baseline level of C-reactive protein. In addition,
these data indicate that the benefit of other therapeutic agents used in the prevention
and treatment of atherosclerotic disorders may differ depending on the underlying
level of C-reactive protein.
[0020] The current invention in one aspect describes the use of C-reactive protein to predict
risk of cardiovascular disorders associated with atherosclerosis such as myocardial
infarction and stroke among individuals without current evidence of disease and without
other coronary risk factors. Thus, these data greatly extend prior observations regarding
the use of inflammatory markers such as C reactive protein to predict risk among already
identified high-risk populations (such as smokers) or among symptomatic ischemia patients
such as those with stable and unstable angina pectoris. Indeed, since levels of C
reactive protein and other acute phase reactants increase following acute ischemia
and are directly related to cigarette consumption, it has been uncertain whether statistical
associations observed in prior studies of acutely ill or high-risk populations are
casual or due to short-term inflammatory changes, or to interrelations with other
risk factors, in particular smoking and hyperlipidemia.
[0021] In marked contrast, data from the Physicians' Health Study indicate for the first
time the utility of inflammatory markers to predict risk among currently healthy and
otherwise low-risk individuals, to predict non-fatal as well as fatal events, to predict
risk among non-smokers, and to predict risk above and beyond that associated with
screening for total and HDL cholesterol. Data from the Physicians' Health Study also
indicate for the first time that the efficacy of interventions designed to reduce
risk of atherosclerotic events such as myocardial infarction and stroke differs in
magnitude based upon a measure of the extent of underlying systemic inflammation.
[0022] The invention will be better understood with reference to the following brief explanation
of terms.
[0023] "Cardiovascular disorders associated with atherosclerotic disease'' includes myocardial
infarction, stroke, angina pectoris and peripheral arteriovascular disease. Cardiovascular
disorders associated with atherosclerotic disease do not include venous thrombosis.
[0024] "Apparently healthy", as used herein, means individuals who have not previously had
an acute adverse cardiovascular event such as a myocardial infarction (i.e., individuals
who are not at an elevated risk of a second adverse cardiovascular event due to a
primary adverse cardiovascular event). Apparently healthy individuals also do not
otherwise exhibit symptoms of disease. In other words, such individuals, if examined
by a medical professional, would be characterized as healthy and free of symptoms
of disease.
[0025] "Nonsmoking", as used herein, means an individual who, at the time of the evaluation,
is not a smoker. This includes individuals who have never smoked as well as individuals
who in the past have smoked but presently no longer smoke.
[0026] Agents for reducing the risk of a cardiovascular disorder include those selected
from the group consisting of anti-inflammatory agents, anti-thrombotic agents, anti-platelet
agents, fibrinolytic agents, lipid reducing agents, direct thrombin inhibitors, and
glycoprotein II b/IIIa receptor inhibitors.
[0027] Anti-inflammatory agents include Alclofenac; Alclometasone Dipropionate; Algestone
Acetonide; Alpha Amylase; Amcinafal; Amcinafide; Amfenac Sodium; Amiprilose Hydrochloride;
Anakinra; Anirolac ; Anitrazafen; Apazone; Balsalazide Disodium; Bendazac; Benoxaprofen
; Benzydamine Hydrochloride; Bromelains; Broperamole; Budesonide; Carprofen; Cicloprofen;
Cintazone; Cliprofen; Clobetasol Propionate; Clobetasone Butyrate; Clopirac; Cloticasone
Propionate; Cormethasone Acetate; Cortodoxone; Deflazacort; Desonide; Desoximetasone;
Dexamethasone Dipropionate; Diclofenac Potassium; Diclofenac Sodium; Diflorasone Diacetate;
Diflumidone Sodium; Diflunisal ; Difluprednate; Diftalone; Dimethyl Sulfoxide; Drocinonide;
Endrysone; Enlimomab ; Enolicam Sodium ; Epirizole ; Etodolac; Etofenamate ; Felbinac;
Fenamole; Fenbufen; Fenclofenac; Fenclorac; Fendosal; Fenpipalone; Fentiazac; Flazalone;
Fluazacort; Flufenamic Acid; Flumizole; Flunisolide Acetate; Flunixin ; Flunixin Meglumine
; Fluocortin Butyl; Fluorometholone Acetate; Fluquazone; Flurbiprofen ; Fluretofen;
Fluticasone Propionate; Furaprofen; Furobufen; Halcinonide; Halobetasol Propionate;
Halopredone Acetate; Ibufenac ; Ibuprofen; Ibuprofen Aluminum; Ibuprofen Piconol;
Ilonidap; Indomethacin; Indomethacin Sodium; Indoprofen ; Indoxole ; Intrazole; Isoflupredone
Acetate; Isoxepac; Isoxicam; Ketoprofen; Lofemizole Hydrochloride ; Lornoxicam ; Loteprednol
Etabonate; Meclofenamate Sodium; Meclofenamic Acid; Meclorisone Dibutyrate; Mefenamic
Acid ; Mesalamine; Meseclazone; Methylprednisolone Suleptanate; Morniflumate; Nabumetone;
Naproxen ; Naproxen Sodium ; Naproxol ; Nimazone; Olsalazine Sodium; Orgotein ; Orpanoxin;
Oxaprozin; Oxyphenbutazone; Paranyline Hydrochloride; Pentosan Polysulfate Sodium;
Phenbutazone Sodium Glycerate; Pirfenidone ; Piroxicam; Piroxicam Cinnamate; Piroxicam
Olamine; Pirprofen; Prednazate; Prifelone; Prodolic Acid; Proquazone; Proxazole; Proxazole
Citrate ; Rimexolone; Romazarit; Salcolex ; Salnacedin; Salsalate ; Salycilates; Sanguinarium
Chloride ; Seclazone ; Sermetacin; Sudoxicam; Sulindac; Suprofen; Talmetacin; Talniflumate
; Talosalate ; Tebufelone ; Tenidap; Tenidap Sodium; Tenoxicam; Tesicam; Tesimide;
Tetrydamine; Tiopinac; Tixocortol Pivalate; Tolmetin; Tolmetin Sodium; Triclonide;
Triflumidate; Zidometacin; Glucocorticoids; Zomepirac Sodium.
[0028] Anti-thrombotic and/or fibrinolytic agents include Plasminogen (to plasmin via interactions
of prekallikrein, kininogens, Factors XII, XIIIa, plasminogen proactivator, and tissue
plasminogen activator[TPA]) Streptokinase; Urokinase: Anisoylated Plasminogen-Streptokinase
Activator Complex; Pro-Urokinase; (Pro-UK); rTPA (alteplase or activase; r denotes
recombinant); rPro-UK; Abbokinase; Eminase; Sreptase Anagrelide Hydrochloride; Bivalirudin;
Dalteparin Sodium; Danaparoid Sodium; Dazoxiben Hydrochloride; Efegatran Sulfate;
Enoxaparin Sodium; Ifetroban; Ifetroban Sodium; Tinzaparin Sodium; retaplase; Trifenagrel;
Warfarin; Dextrans.
[0029] Anti-platelet agents include Clopridogrel; Sulfinpyrazone; Aspirin; Dipyridamole;
Clofibrate; Pyridinol Carbamate; PGE; Glucagon; Antiserotonin drugs; Caffeine; Theophyllin
Pentoxifyllin; Ticlopidine; Anagrelide.
[0030] Lipid reducing agents include gemfibrozil, cholystyramine, colestipol, nicotinic
acid, probucol lovastatin, fluvastatin, simvastatin, atorvastatin, pravastatin, cirivastatin.
[0031] Direct thrombin inhibitors include hirudin, hirugen, hirulog, agatroban, PPACK, thrombin
aptamers.
[0032] Glycoprotein IIb/IIIa receptor Inhibitors are both antibodies and non-antibodies,
and include but are not limited to ReoPro (abcixamab), lamifiban, tirofiban.
[0033] One preferred agent is aspirin.
[0034] In practicing the methods of the present invention, it is required to obtain the
level of C-reactive protein in an individual without other coronary risk factors.
[0035] The level of C-reactive protein for the individual can be obtained by any art recognized
method. Typically, the level is determined by measuring the level of the marker in
a body fluid, for example, blood, lymph, saliva, urine and the like. The level can
be determined by ELISA, or immunoassays or other conventional techniques for determining
the presence of the marker. Conventional methods include sending samples of a patient's
body fluid to a commercial laboratory for measurement.
[0036] The invention also involves comparing the level of marker for the individual with
a predetermined value. The predetermined value can take a variety of forms. It can
be single cut-off value, such as a median or mean. It can be established based upon
comparative groups, such as where the risk in one defined group is double the risk
in another defined group. It can be a range, for example, where the tested population
is divided equally (or unequally) into groups, such as a low-risk group, a medium-risk
group and a high-risk group, or into quadrants, the lowest quadrant being individuals
with the lowest risk and the highest quadrant being individuals with the highest risk.
[0037] The predetermined value can depend upon the particular population selected. For example,
an apparently healthy, nonsmoker population (no detectable disease and no prior history
of a cardiovascular disorder) will have a different 'normal' range of markers of systemic
inflammation than will a smoking population. Accordingly, the predetermined values
selected may take into account the category in which an individual falls. Appropriate
ranges and categories can be selected with no more than routine experimentation by
those of ordinary skill in the art.
[0038] The preferred body fluid is blood. For C-reactive protein, one important cut-off
for a population of apparently healthy, nonsmokers is 1.75 mg/liter (median). Another
important cut-off for C-reactive protein is 2.0 mg/liter (highest quartile of risk).
In characterizing risk, numerous predetermined values can be established. In the preferred
embodiment employing C-reactive protein, the cut-off values described above, and in
greater detail in the example below, are surprisingly lower than those shown in the
prior art where C-reactive protein levels are studied in
unhealthy individuals or smokers.
[0039] There presently are commercial sources which produce reagents for assays for C-reactive
protein. These include, but are not limited to, Abbott Pharmaceuticals (Abbott Park,
Illinois), CalBiochem (San Diego, CA) and Behringwerke (Marburg, Germany). Commercial
sources for inflammatory cytokine and cellular adhesion molecule measurements, include,
but are not limited to, R&D Systems (Minneapolis, MN), Genzyme (Cambridge, MA) and
Immunotech (Westbrook, ME).
[0040] The assay for C-reactive protein is specific for, and has appropriate sensitivity
with respect to, predetermined values selected on the basis of the present invention.
The assay, therefore, would differ from those presently commercially available, by
including, for example, different cut-offs, different sensitivities at particular
cut-offs as well as instructions or other printed material for characterizing risk
based upon the outcome of the assay.
[0041] As discussed above the invention provides methods for evaluating the likelihood that
an individual will benefit from treatment with an agent for reducing risk of a future
cardiovascular disorder. This method has important implications for patient treatment
and also for clinical development of new therapeutics. Physicians select therapeutic
regimens for patient treatment based upon the expected net benefit to the patient.
The net benefit is derived from the risk to benefit ratio. The present invention permits
selection of individuals who are more likely to benefit by intervention, thereby aiding
the physician in selecting a therapeutic regimen. This might include using drugs with
a higher risk profile where the likelihood of expected benefit has increased. Likewise,
clinical investigators desire to select for clinical trials a population with a high
likelihood of obtaining a net benefit. The present invention can help clinical investigators
select such individuals. It is expected that clinical investigators now will use the
present invention for determining entry criteria for clinical trials.
[0042] In another surprising aspect of the invention, it has been discovered that C-reactive
protein has predictive value independent of other known predictors of future adverse
cardiovascular disorders. Thus, the present invention does not involve simply duplicating
a measurement that previously could be made using other predictors.
[0043] The invention also involves a use of anti-inflammatory therapies for the manufacture
of a medicament for treating subjects to prevent cardiovascular disorders. An anti-inflammatory
agent is administered to a subject who has an above-normal level of C-reactive protein,
but who is otherwise free of symptoms calling for an anti-inflammatory agent. The
anti-inflammatory agent is administered in an effective amount.
[0044] An effective amount is a dosage of the anti-inflammatory agent sufficient to provide
a medically desirable result. The effective amount will vary with the particular condition
being treated, the age and physical condition of the subject being treated, the severity
of the condition, the duration of the treatment, the nature of the concurrent therapy
(if any), the specific route of administration and the like factors within the knowledge
and expertise of the health practioner. For example, an effective amount can depend
upon the degree to which an individual has abnormally elevated levels of markers of
systemic information. It should be understood that the anti-inflammatory agents of
the invention are used to prevent cardiovascular disorders, that is, they are used
prophylactically in subjects at risk of developing a cardiovascular disorder. Thus,
an effective amount is that amount which can lower the risk of, slow or perhaps prevent
altogether the development of a cardiovascular disorder. When the agent is one that
binds to cellular adhesion molecules and inhibits the ability of white blood cells
to attach to such molecules, then the agent may be used prophylactically or may be
used in acute circumstances, for example, post-myocardial infarction or post-angioplasty.
It will be recognized when the agent is used in acute circumstances, it is used to
prevent one or more medically undesirable results that typically flow from such adverse
events. In the case of myocardial infarction, the agent can be used to limit injury
to the cardiovascular tissue which develops as a result of the myocardial infarction
and in the case of restinosis the agent can be used in amounts effective to inhibit,
prevent or slow the reoccurrence of blockage. In either case, it is an amount sufficient
to inhibit the infiltration of white blood cells and transmigration of white blood
cells into the damaged tissue, which white blood cells can result in further damage
and/or complications relating to the injury.
[0045] Generally, doses of active compounds would be from about 0.01 mg/kg per day to 1000
mg/kg per day. It is expected that doses ranging from 50-500 mg/kg will be suitable,
preferably orally and in one or several administrations per day. Lower doses will
result from other forms of administration, such as intravenous administration. In
the event that a response in a subject is insufficient at the initial doses applied,
higher doses (or effectively higher doses by a different, more localized delivery
route) may be employed to the extent that patient tolerance permits. Multiple doses
per day are contemplated to achieve appropriate systemic levels of compounds.
[0046] When administered, the pharmaceutical preparations of the invention are applied in
pharmaceutically-acceptable amounts and in pharmaceutically-acceptably compositions.
Such preparations may routinely contain salt, buffering agents, preservatives, compatible
carriers, and optionally other therapeutic agents. When used in medicine, the salts
should be pharmaceutically acceptable, but non-pharmaceutically acceptable salts may
conveniently be used to prepare pharmaceutically-acceptable salts thereof and are
not excluded from the scope of the invention. Such pharmacologically and pharmaceutically-acceptable
salts include, but are not limited to, those prepared from the following acids: hydrochloric,
hydrobromic, sulfuric, nitric, phosphoric, maleic, acetic, salicylic, citric, formic,
malonic, succinic, and the like. Also, pharmaceutically-acceptable salts can be prepared
as alkaline metal or alkaline earth salts, such as sodium, potassium or calcium salts.
[0047] The anti-inflammatory agents may be combined, optionally, with a pharmaceutically-acceptable
carrier. The term "pharmaceutically-acceptable carrier'' as used herein means one
or more compatible solid or liquid filler, diluents or encapsulating substances which
are suitable for administration into a human. The term "carrier" denotes an organic
or inorganic ingredient, natural or synthetic, with which the active ingredient is
combined to facilitate the application. The components of the pharmaceutical compositions
also are capable of being co-mingled with the molecules of the present invention,
and with each other, in a manner such that there is no interaction which would substantially
impair the desired pharmaceutical efficacy.
[0048] The pharmaceutical compositions may contain suitable buffering agents, including:
acetic acid in a salt; citric acid in a salt; boric acid in a salt; and phosphoric
acid in a salt.
[0049] The pharmaceutical compositions also may contain, optionally, suitable preservatives,
such as: benzalkonium chloride; chlorobutanol; parabens and thimerosal.
[0050] Compositions suitable for parenteral administration conveniently comprise a sterile
aqueous preparation of the anti-inflammatory agent, which is preferably isotonic with
the blood of the recipient. This aqueous preparation may be formulated according to
known methods using suitable dispersing or wetting agents and suspending agents. The
sterile injectable preparation also may be a sterile injectable solution or suspension
in a non-toxic parenterally-acceptable diluent or solvent, for example, as a solution
in 1,3-butane diol. Among the acceptable vehicles and solvents that may be employed
are water, Ringer's solution, and isotonic sodium chloride solution. In addition,
sterile, fixed oils are conventionally employed as a solvent or suspending medium.
For this purpose any bland fixed oil may be employed including synthetic mono- or
di-glycerides. In addition, fatty acids such as oleic acid may be used in the preparation
of injectables. Carrier formulation suitable for oral, subcutaneous, intravenous,
intramuscular, etc. administrations can be found in Remington's Pharmaceutical Sciences,
Mack Publishing Co., Easton, PA.
[0051] A variety of administration routes are available. The particular mode selected will
depend, of course, upon the particular drug selected, the severity of the condition
being treated and the dosage required for therapeutic efficacy. The methods of the
invention, generally speaking, may be practiced using any mode of administration that
is medically acceptable, meaning any mode that produces effective levels of the active
compounds without causing clinically unacceptable adverse effects. Such modes of administration
include oral, rectal, topical, nasal, interdermal, or parenteral routes. The term
"parenteral" includes subcutaneous, intravenous, intramuscular, or infusion. Intravenous
or intramuscular routes are not particularly suitable for long-term therapy and prophylaxis.
They could, however, be preferred in emergency situations. Oral administration will
be preferred for prophylactic treatment because of the convenience to the patient
as well as the dosing schedule.
[0052] The pharmaceutical compositions may conveniently be presented in unit dosage form
and may be prepared by any of the methods well-known in the art of pharmacy. All methods
include the step of bringing the anti-inflammatory agent into association with a carrier
which constitutes one or more accessory ingredients. In general, the compositions
are prepared by uniformly and intimately bringing the anti-inflammatory agent into
association with a liquid carrier, a finely divided solid carrier, or both, and then,
if necessary, shaping the product.
[0053] Compositions suitable for oral administration may be presented as discrete units,
such as capsules, tablets, lozenges, each containing a predetermined amount of the
anti-inflammatory agent. Other compositions include suspensions in aqueous liquids
or nonaqueous liquids such as a syrup, elixir or an emulsion.
[0054] Other delivery systems can include time-release, delayed release or sustained release
delivery systems. Such systems can avoid repeated administrations of the anti-inflammatory
agent, increasing convenience to the subject and the physician. Many types of release
delivery systems are available and known to those of ordinary skill in the art. They
include polymer base systems such as poly(lactide-glycolide), copolyoxalates, polycaprolactones,
polyesteramides, polyorthoesters, polyhydroxybutyric acid, and polyanhydrides. Microcapsules
of the foregoing polymers containing drugs are described in, for example, U.S. Patent
5,075,109. Delivery systems also include non-polymer systems that are: lipids including
sterols such as cholesterol, cholesterol esters and fatty acids or neutral fats such
as mono- di-and tri-glycerides; hydrogel release systems; sylastic systems; peptide
based systems; wax coatings; compressed tablets using conventional binders and excipients;
partially fused implants; and the like. Specific examples include, but are not limited
to: (a) erosional systems in which the anti-inflammatory agent is contained in a form
within a matrix such as those described in U.S. Patent Nos. 4,452,775, 4,667,014,
4,748,034 and 5,239,660 and (b) difusional systems in which an active component permeates
at a controlled rate from a polymer such as described in U.S. Patent Nos. 3,832,253,
and 3,854,480. In addition, pump-based hardware delivery systems can be used, some
of which are adapted for implantation.
[0055] Use of a long-term sustained release implant may be particularly suitable for treatment
of chronic conditions. Long-term release, are used herein, means that the implant
is constructed and arranged to delivery therapeutic levels of the active ingredient
for at least 30 days, and preferably 60 days. Long-term sustained release implants
are well-known to those of ordinary skill in the art and include some of the release
systems described above.
EXAMPLE
Study Organization
[0056] The Physicians' Health Study is a randomized, double-blind, placebo controlled, 2
x 2 factorial trial of aspirin and beta-carotene in the primary prevention of cardiovascular
disease and cancer.
Subject recruitment
[0057] A total of 22,071 US male physicians aged 40 to 84 years in 1982 with no history
of myocardial infarction, stroke, transient ischemic attack, or cancer were assigned
to one of four treatment groups: 325 mg aspirin on alternate days (Bufferin, provided
by Bristol-Myers), 50 mg of beta-carotene on alternate days (Lurotin, provided by
BASF Corporation), both, or neither. The aspirin component of the PHS was terminated
early on January 25, 1988 primarily due to a statistically extreme 44 percent reduction
in risk of first infarction in the aspirin group.
1 The beta-carotene component continued to scheduled termination on December 31, 1995.
2
[0058] Before randomization, between August 1982 and December 1984, potentially eligible
participants were asked to provide baseline blood samples during a 16 week run-in
period with all subjects given active aspirin. Blood collection kits including EDTA
vacutainer tubes were sent to participants with instructions for taking blood. Participants
were asked to have their blood drawn into the EDTA tubes, centrifuge the tubes, and
return the plasma (accompanied by a provided cold pack) by overnight courier. Upon
return, specimens were alliquotted and stored at -80°C. Of 22,071 participants in
the PHS, 14,916 (68 percent) provided baseline plasma samples. Over the 14 year period
of the trial, no specimen has inadvertently thawed during storage.
Endpoint Confirmation and Selection of Controls
[0059] Hospital records (and for fatal events, death certificates and necropsy reports)
were requested for all reported cases of myocardial infarction, stroke, and venous
thrombosis. Records were reviewed by a committee of physicians using standardized
criteria to confirm or refute reported events. Endpoints reviewers were blinded to
treatment assignment.
[0060] Reported myocardial infarction was confirmed if the event met World Health Organization
criteria of symptoms plus either elevated enzymes or characteristic electrocardiographic
changes. Silent myocardial infarctions were not included since they could not be dated
accurately. Deaths due to coronary disease were confirmed based on autopsy reports,
symptoms, circumstances of death, and prior history of coronary disease. Reported
stroke was confirmed based on medical records showing neurological deficit of sudden
or rapid onset persisting for more than 24 hours or until death. Strokes were classified
as ischemic or hemorrhagic. Computed tomography was available for more than 95 percent
of confirmed strokes. Reported deep venous thrombosis was confirmed by documentation
of a positive venography study or a positive ultrasound study; deep venous thrombosis
documented only by impedance plethysmography or Doppler examination without ultrasound
were not confirmed. Reported pulmonary embolism was confirmed by positive angiogram
or completed ventilation-perfusion scan demonstrating at least two segmental perfusion
defects with normal ventilation.
[0061] Each participant who provided an adequate baseline plasma sample and had a confirmed
myocardial infarction, stroke, or venous thrombosis after randomization was matched
to one control. Controls were participating physicians who provided baseline plasma
samples and reported no cardiovascular disease at the time the case reported his event.
Controls were randomly selected from study participants who met the matching criteria
of age (+/- one year), smoking habit (current, past, or never), and time since randomization
(six month intervals). Using these methods, we evaluated 543 cases and 543 controls
in this prospective nested case-control design.
Collection of Plasma Samples and Laboratory Analysis
[0062] For each case and control, plasma collected and stored at baseline was thawed and
assayed for C-reactive protein employing enzyme linked immunoabsorbant assays (ELISA)
based upon purified protein and polyclonal anti-protein antibodies (Calbiochem).
3 In brief, antibodies are used to coat microtiter plate wells, and biotinylated C-reactive
protein plus patient plasma is diluted 1:700 in assay buffer (phosphate-buffered saline
with 0.1 percent Tween-20, and 1 percent bovine serum albumin). After competition,
excess is washed off and the amount of biotinylated protein estimated by the addition
of avidin-peroxidase (Vectastain, Vector Laboratories, Burlingame, CA). Purified proteins
are then used as standards, with the protein concentrations as determined by the manufacturer.
The C-reactive protein assay was standardized using the 1st International Reference
Standard of the World Health Organization and has sensitivity to 0.08 ug/microliter
with standard reference range between 0.5 and 2.5 mg/liter. Methods used to measure
total and HDL cholesterol, triglyceride, lipoprotein(a), total plasma homocysteine,
fibrinogen, D-dimer, and endogenous tissue-type plasminogen activator (tPA) antigen
have been described elsewhere.
4-8
[0063] Blood specimens were analyzed in blinded pairs with the position of the case varied
at random within pairs to reduce the possibility of systematic bias and decrease interassay
variability. The mean coefficient of variation for C-reactive protein across assay
runs was 4.2 percent.
Statistical analysis
[0064] Means or proportions for baseline risk factors were calculated for cases and controls.
The significance of any difference in means was tested using the Student's t-test
and the significance of any differences in proportions tested using the Chi square
statistic. Because C-reactive protein levels are skewed, median levels were computed
and the significance of any differences in median values between cases and controls
assessed using Wilcoxon's Rank Sum Test. Geometric mean C-reactive protein levels
were also computed after log transformation which resulted in near normal distribution.
Tests for trends were used to assess any relationship of increasing levels of C-reactive
protein with risks of future vascular disease after dividing the sample into quartiles
defined by the distribution of the control values. Adjusted estimates were obtained
using conditional logistic regression models accounting for the matching variables
and controlling for randomized treatment assignment, body mass index, diabetes, history
of hypertension, and a parental history of coronary artery disease. Similar models
were employed to adjust for measured baseline levels of total and HDL cholesterol,
triglyceride, lipoprotein(a), tPA antigen, fibrinogen, D-dimer, and homocysteine.
To evaluate whether aspirin affected these relationships, analyses were repeated for
all myocardial infarction events occurring on or before January 25, 1988, the date
of termination of randomized aspirin assignment. All P values were two-tailed and
confidence intervals calculated at the 95 percent level.
Results
[0065] Table 1 shows baseline characteristics of study participants. As expected, those
who subsequently developed myocardial infarction were more likely than those who remained
free of vascular disease to have a history of hypertension, hyperlipidemia, or a parental
history of coronary artery disease. Similarly, those who subsequently developed stroke
were more likely to be hypertensive. Due to the matching, age and smoking were similar
in cases and controls.
Table 1:
| Baseline Characteristics of Study Participants |
| |
Cardiovascular Disease During Follow-up |
|
|
| |
None
(N = 543) |
Any
(N = 543) |
MI
(N = 246) |
CVA
(N = 196) |
DVT/PE
(N = 101) |
| Age (yrs*) |
59+/-9.1 |
59+/-9.2 |
58+/-8.6 |
62+/-9.1 |
57+/-9.4 |
| Smoking Status (%) |
|
|
|
|
|
| Never |
44 |
44 |
45 |
42 |
50 |
| Past |
41 |
41 |
40 |
40 |
44 |
| Current |
15 |
15 |
15 |
18 |
6 |
| Diabetes (%) |
4 |
7 |
5 |
12 |
2 |
| Body Mass Index (kg/m2*) |
25+/-2.8 |
26+/-3.2 |
26+/-3.3 |
25 +/- 3.2 |
26+/-2.9 |
| History of high cholesterol (%) |
9 |
13 |
17 |
10 |
7 |
| History of Hypertension (%) |
16 |
29 |
27 |
35 |
20 |
| Parental history of coronary artery disease (%) |
10 |
13 |
17 |
11 |
8 |
| *values represent means +/- SD |
[0066] Geometric mean and median levels of baseline C-reactive protein were significantly
higher among those who subsequently developed any vascular event compared to those
who did not (P<0.001). The difference between cases and controls was greatest for
those who subsequently developed myocardial infarction (1.51 mg/liter vs 1.13 mg/liter,
P<0.001) although differences were also significant for stroke (P=0.03), particularly
those of ischemic etiology (P=0.02). In contrast, C-reactive protein levels were not
significantly increased among those who subsequently developed venous thrombosis (P=0.34)(Table
2).
Table 2:
| Baseline levels of C-reactive protein among study participants who remained free of
vascular disease during follow-up (controls) and among those who developed myocardial
infarction, stroke, or venous thrombosis (cases) |
| Baseline Level of C-Reactive Protein (mg/liter) |
| Cardiovascular Disease During Follow-up |
Geometric Mean |
p |
Median |
p |
| None (N = 543) |
1.10 |
-- |
1.13 |
-- |
| Any Vascular Event (N = 246) |
1.37 |
<0.001 |
1.40 |
<0.001 |
| Myocardial Infarction (N = 246) |
1.48 |
<0.001 |
1.51 |
<0.001 |
| Any Stroke (N = 196) |
1.30 |
0.03 |
1.36 |
0.03 |
| Ischemic Stroke (N = 154) |
1.36 |
0.01 |
1.38 |
0.02 |
| Venous Thrombosis (N = 101) |
1.24 |
0.22 |
1.26 |
0.34 |
[0067] Relative risks of developing first myocardial infarction increased significantly
with each increasing quartile of baseline C-reactive protein (P for trend across quartiles
<0.001) such that men in the highest quartile had risks of future myocardial infarction
almost 3 times greater than those in the lowest (relative risk = 2.9, 95 percent confidence
interval 1.8 to 4.6, P<0.001)(Table 3). Similarly, men with the highest baseline C-reactive
protein levels had twice the risk of developing future ischemic stroke (relative risk
= 1.9, 95 percent confidence interval 1.1 to 3.3, P = 0.02). No significant associations
were observed for venous thrombosis. Findings were similar in analyses limited to
non-fatal events.
Table 3:
| Relative risks of future myocardial infarction, stroke, and venous thrombosis according
to baseline levels of C-reactive protein. |
| Quartile of C-Reactive Protein (range, mg/liter) |
| |
1 (≤0.55) |
2 (0.56-1.14) |
3 (1.15-2.10) |
4 (≥2.11) |
p-trend |
| Myocardial Infarction (total cohort) |
|
|
|
|
|
| RR |
1.0 |
1.7 |
2.6 |
2.9 |
<0.001 |
| 95% Cl |
-- |
1.1 - 2.9 |
1.6-4.3 |
1.8 - 4.6 |
|
| P |
-- |
0.03 |
<0.001 |
<0.001 |
|
| Myocardial Infarction (non-smokers) |
|
|
|
|
|
| RR |
1.0 |
1.7 |
2.5 |
2.8 |
<0.001 |
| 95% CI |
-- |
1.0-2.8 |
1.5 - 4.1 |
1.7-4.7 |
|
| p |
-- |
0.06 |
<0.001 |
<0.001 |
|
| Ischemic Stroke |
|
|
|
|
|
| RR |
1.0 |
1.7 |
1.9 |
1.9 |
0.03 |
| 95% Cl |
-- |
0.9-2.9 |
1.1-3.2 |
1.1-3.3 |
|
| p |
-- |
0.07 |
0.02 |
0.02 |
|
| Venous Thrombosis |
|
|
|
|
|
| RR |
1.0 |
1.1 |
1.2 |
1.3 |
0.38 |
| 95% CI |
-- |
0.6-2.0 |
0.7-2.3 |
0.7-2.4 |
|
| p |
-- |
0.78 |
0.51 |
0.42 |
|
| 95% CI = 95 percent confidence interval |
[0068] To evaluate whether increased baseline levels of C-reactive protein were associated
with early rather than late thrombosis, we stratified the analysis of myocardial infarction
by years of follow-up. The relative risk of future myocardial infarction associated
with the highest quartile of C-reactive protein (as compared to the lowest quartile)
ranged between 2.4 for events occurring in the first two years of follow-up to 3.2
for events occurring 6 or more years into study follow-up (Table 4). Similarly, the
relative risk of future myocardial infarction associated with a one quartile change
in C-reactive protein was stable over long time periods (Figure 2).
Table 4.
| Relative risks of first myocardial infarction associated with the highest quartile
of baseline C-reactive protein compared to the lowest quartile, according to year
of study follow-up. |
| |
Follow-Up Time (years) |
| |
0-2 |
2-4 |
4-6 |
6+ |
| Total Cohort |
|
|
|
|
| RR |
2.4 |
2.9 |
2.8 |
3.2 |
| 95% Cl |
0.9-6.8 |
1.1-7.6 |
1.1-6.9 |
1.2-8.5 |
| p |
0.09 |
0.03 |
0.03 |
0.02 |
| Non-Smokers |
|
|
|
|
| RR |
2.8 |
2.9 |
2.7 |
2.9 |
| 95% Cl |
0.9-8.7 |
1.0-8.3 |
1.0-7.0 |
1.1-8.2 |
| p |
0.07 |
0.05 |
0.05 |
0.04 |
| 95 % Cl = 95 percent confidence interval |
[0069] Smokers had significantly higher median levels of C-reactive protein than non-smokers
(2.20 mg/liter vs 1.19 mg/liter, P < 0.001). Because of the match by smoking status,
we minimized the potential for confounding by smoking. However, to assess for effect
modification, we repeated analyses limiting the cohort to non-smokers. As also shown
in Table 3, the relative risks of future myocardial infarction among non-smokers significantly
increased with each increasing quartile of C-reactive protein (P-trend < 0.001). Similarly,
the long term effects of C-reactive protein on risk of myocardial infarction were
virtually identical among non-smokers (Table 4).
[0070] The relationship between C-reactive protein and myocardial infarction was not significantly
altered in analyses which adjusted for body mass index, diabetes, hypertension, a
family history of premature coronary artery disease, total cholesterol, HDL cholesterol,
triglycerides, lipoprotein(a), tPA antigen, D-dimer, fibrinogen, or homocysteine (Table
5).
Table 5.
| Relative risks* of future myocardial infarction according to baseline levels of C-reactive
protein, adjusted for lipid and non-lipid variables. |
| Quartile of C-Reactive Protein (range, mg/liter) |
| Variable(s) Adjusted for: |
|
1
(≤0.55) |
2
(0.56-1.14) |
3
(1.15-2.10) |
4
(≥2.11) |
p-trend |
| Total and HDL Cholesterol |
|
|
|
|
|
|
| |
Adjusted RR |
1.0 |
1.8 |
2.2 |
2.3 |
0.002 |
| |
95% Cl |
-- |
1.0-3.1 |
1.3-3.7 |
1.4-3.9 |
|
| |
p |
-- |
0.05 |
0.004 |
0.002 |
|
| Triglyceride Level |
|
|
|
|
|
|
| |
Adjusted RR |
1.0 |
1.8 |
2.1 |
2.8 |
<0.001 |
| |
95% CI |
-- |
1.0-3.2 |
1.2-3.7 |
1.6-4.9 |
|
| |
p |
-- |
0.06 |
0.008 |
<0.001 |
|
| Lipoprotein(a) |
|
|
|
|
|
|
| |
Adjusted RR |
1.0 |
2.0 |
2.5 |
2.5 |
<0.001 |
| |
95% CI |
-- |
1.2-3.4 |
1.5-4.2 |
1.5-4.2 |
|
| |
p |
-- |
0.01 |
<0.001 |
<0.001 |
|
| tPA antigen level |
|
|
|
|
|
|
| |
Adjusted RR |
1.0 |
1.7 |
1.9 |
2.9 |
0.002 |
| |
95% CI |
-- |
0.9-3.4 |
1.0-3.6 |
1.5-5.6 |
|
| |
p |
-- |
0.13 |
0.06 |
0.002 |
|
| total plasma homocysteine level |
|
|
|
|
|
|
| |
Adjusted RR |
1.0 |
1.8 |
2.9 |
3.6 |
<0.001 |
| |
95%CI |
-- |
1.1-3.1 |
1.7-4.8 |
2.1-5.9 |
|
| |
p |
-- |
0.02 |
<0.001 |
<0.001 |
|
| D-dimer level |
|
|
|
|
|
|
| |
Adjusted RR |
1.0 |
2.2 |
2.4 |
2.7 |
0.001 |
| |
95% CI |
-- |
1.2-4.1 |
1.3-4.2 |
1.5-4.7 |
|
| |
p |
-- |
0.007 |
0.003 |
<0.001 |
|
| fibrinogen level |
|
|
|
|
|
|
| |
Adjusted RR |
1.0 |
2.2 |
2.2 |
2.9 |
0.01 |
| |
95% Cl |
- |
1.1-4.7 |
1.0-4.4 |
1.4-5.9 |
|
| |
p |
- |
0.04 |
0.04 |
0.005 |
|
| Body mass index (kg/m2), diabetes, history of hypertension, and family history of premature CAD |
|
|
|
|
|
|
| |
Adjusted RR |
1.0 |
1.5 |
2.4 |
2.6 |
<0.001 |
| |
95% Cl |
- |
0.9-2.5 |
1.5-4.0 |
1.6-4.4 |
|
| |
p |
- |
0.14 |
<0.001 |
<0.001 |
|
*All models further adjusted for randomized aspirin and beta-carotene assignment.
RR = relative risk, 95 % Cl = 95 percent confidence intervals |
[0071] To assess whether the beneficial effect of aspirin on myocardial infarction varied
according to baseline C-reactive protein level, we repeated these analyses for events
occurring prior to January 25, 1988, the date of termination of the randomized aspirin
treatment.
[0072] Risks of developing future myocardial infarction increased with each increasing quartile
of C-reactive protein for men randomly assigned to either aspirin or placebo, and
rates of myocardial infarction were lower in the aspirin group for all quartiles of
C-reactive protein (Figure 3). However, the magnitude of the beneficial effect of
aspirin on preventing myocardial infarction was directly related to baseline C-reactive
protein level. Specifically, randomized aspirin assignment was associated with a large
and statistically significant reduction in risk of myocardial infarction among men
with baseline C-reactive protein levels in the highest quartile (risk reduction =
55.7 percent, P = 0.02). However, among those with baseline C-reactive protein levels
in the lowest quartile, the reduction in risk associated with aspirin was far smaller
and no longer statistically significant (risk reduction = 13.9 percent, P = 0.77).
These effects were linear across quartiles such that the apparent benefit of aspirin
diminished in magnitude with each decreasing quartile of inflammatory risk (Figure
3). This finding remained essentially unchanged after further adjustment for other
coronary risk factors and the interaction between assignment to the aspirin group
and baseline C-reactive protein level (treated as a log transformed continuous variable)
was statistically significant (P= 0.048).
[0073] Data from the Physicians Health Study also indicate that measures of inflammation
such as C-RP predict the future risk of developing peripheral arterial disease, another
clinical manifestation of systemic atherosclerosis. For example, those with baseline
levels of C-RP in excess of 2.0 mg/liter had twice the risk of developing future peripheral
arterial disease as did those with lower levels. Moreover, in these data, the risks
of developing peripheral arterial disease severe enough to require surgical intervention
was increased fourfold for those with the highest baseline levels of C-RP.
[0074] To evaluate whether C-reactive protein might be a predictor of risk over and above
that associated with cholesterol levels, a series of stratified analyses were further
performed. In this regard, C-reactive protein was found to predict risk of future
myocardial infarction among those with low as well as high levels of total cholesterol,
and among those with low as well as high total cholesterol to HDL cholesterol ratios.
[0075] The actual C-reactive protein levels for the tested population are shown graphically
in Fig. 4. The log normalized C-reactive protein levels are shown in Fig. 5, which
demonstrates clearly the normal bell curve distribution in our population. The mean
C-reactive protein was 1.75 and the standard deviation was 2.2. The mean of the log
C-reactive protein was about .1 and the standard deviation was about 1. The relative
ability to produce future cardiovascular disorder of another marker of systemic inflammation,
soluble intracellular adhesion molecule (sICAM-1), also was evaluated. Table 6 shows
the relative risks (RR) of future myocardial infarction according to baseline levels
of s-ICAM-1. A statistically significant association was observed. The relationship
between s-ICAM and myocardial infarction also is not significantly altered in analysis
which adjusted for body mass index, diabetes, a family history of premature coronary
artery disease, hyperlipidemia, and a history of hypertension.
Table 6:
| Relative risks (RR) of future myocardial infarction according to baseline levels of
soluble intercellular adhesion molecule (slCAM-1) |
| |
Quartile of slCAM-1 (range, ng/liter) |
| |
1
(≤ 193) |
2
(193-224) |
3
(225-259) |
4
(>259) |
p-trend |
| Crude RR |
1.0 |
0.8 |
1.0 |
1.5 |
0.01 |
| Lipid Adjusted *RR |
1.0 |
0.7 |
0.9 |
1.5 |
0.01 |
| Fully Adjusted** RR |
1.0 |
1.1 |
1.0 |
1.9 |
0.01 |
| * Matched for smoking and age, controlled for total and HDL cholesterol |
** Matched for smoking and age, controlled for history of hypertension, hyperlipidemia,
body mass index, diabetes, and a family history of premature CAD
95% CI = 95 percent confidence interval |
Discussion
[0076] These prospective data indicate that baseline C-reactive protein level among apparently
healthy men predicts risk of first myocardial infarction and ischemic stroke. Further,
the risks of arterial thrombosis associated with C-reactive protein were stable over
long periods of time and were not modified by other factors including smoking, body
mass index, blood pressure, total and HDL cholesterol, triglyceride, lipoprotein(a),
tPA antigen, D-dimer, fibrinogen, or homocysteine. In contrast, the benefit of aspirin
in reducing risk of first myocardial infarction diminished significantly with decreasing
C-reactive protein level, an intriguing finding as this agent has anti-inflammatory
as well as anti-platelet properties. Finally, there was no significant association
for venous thromboembolism suggesting that the relationship of inflammation with vascular
risk may be limited to the arterial circulation. We also observed a significant association
between risk of future myocardial infarction and a second measure of systemic inflammation,
sICAM-1.
[0077] Since blood samples were collected at baseline, we can exclude the possibility that
acute ischemia affected C-reactive protein levels. Further, the statistically significant
associations observed were present among non-smokers indicating that the effect of
C-reactive protein on vascular risk is not simply the result of cigarette consumption.
9,10 Thus, our prospective data relating baseline C-reactive protein level to future risks
of myocardial infarction and stroke among apparently healthy men greatly extends prior
observations from studies of acutely ill patients
12, patients with symptomatic coronary disease
11, or those at high risk due primarily to cigarette consumption.
9 Moreover, in these data, the effects of C-reactive protein were independent of a
large number of lipid and non-lipid risk factors.
[0078] The mechanisms by which C-reactive protein is related to atherothrombosis are uncertain.
Prior infection with
Chlamydia pnuemoniae. Heliobacter pylori, Herpes simplex virus, or cytomegalovirus may be a source of the chronic inflammation detected by
C-reactive protein.
13-19 It is also possible that C-reactive protein is a surrogate for interleukin-6
20, a cellular cytokine associated with macrophage and monocyte recruitment into atherosclerotic
plaque.
21 In addition, C-reactive protein can induce monocytes to express tissue-factor, a
membrane glycoprotein important in the initiation of coagulation.
22 Finally, it had been hypothesized that bronchial inflammation secondary to smoking
is responsible for associations seen in prior studies relating C-reactive protein
to vascular risk.
9 In this regard, our observation that the effect of C-reactive protein is present
among non-smokers makes bronchial inflammation a less likely mechanism. Further, the
finding that the effects of C-reactive protein are stable over long time periods suggests
that acute effects on clotting are unlikely.
[0079] Our data regarding the interrelation of C-reactive protein and aspirin merit careful
consideration. In the Physicians' Health Study, aspirin reduced risks of first myocardial
infarction by 44 percent.
1 The present findings indicate that the effect of aspirin on first myocardial infarction
was greatest among those with highest baseline C-reactive protein levels and that
the benefit diminished significantly in magnitude with decreasing concentration of
this inflammatory marker.
[0080] Some conclusions may be drawn. First, among apparently healthy men, baseline level
of inflammation as assessed by C-reactive protein predicts risk of first myocardial
infarction and ischemic stroke, independent of other risk factors. Second, baseline
C-reactive protein level is not associated with venous thrombosis, a vascular event
generally not associated with atherosclerosis. Third, C-reactive protein is not simply
a short term marker as previously demonstrated for patients with unstable angina
12, but also a long term marker of risk, even for events occurring after 6 or more years.
This observation suggests that the effects of inflammation are likely mediated through
a chronic process, and excludes the possibility that undetected acute illness at baseline
is responsible for observed effects. Fourth, these data suggest that assessment of
C-reactive protein can add to our ability to predict atherosclerotic risk, over and
above that defined by levels of total cholesterol and the total cholesterol to HDL
cholesterol ratio. Finally, the benefits of aspirin appear to be modified by underlying
inflammation.
1. Steering Committee of the Physicians' Health Study Research Group. Final report
of the aspirin component of the ongoing Physicians' Health Study. N Engl J Med 1989;321:129-35.
2. Hennekens CH, Buring JE, Manson JE, et al. Lack of effect of long-term supplementation
with beta carotene on the incidence of malignant neoplasms and cardiovascular disease.
N Engl J Med 1996;334:1145-9.
3. Macy EM, Hayes TE, Tracy RP. Variability in the measurement of C-reactive protein
in healthy adults: implications for reference interval and epidemiologic methods.
Clin Chem 1997; 43-52-58.
4. Stampfer MJ, Sacks FM, Salvini S, Willett WC, Hennekens CH. A prospective study
of cholesterol, apolipoproteins, and the risk of myocardial infarction. N Engl J Med
1991;325:373-81.
5. Ridker PM, Hennekens CH, Stampfer MJ. A prospective study of lipoprotein(a) and
the risk of myocardial infarction. JAMA 1993;270:2195-2199.
6. Ridker PM, Hennekens CH, Selhub J, Miletich JP, Malinow MR, Stampfer MJ. Interrelation
of hyperhomocyst(e)inemia, factor V Leiden, and risks of future venous thromboembolism.
Circulation 1997 (in press).
7. Ridker PM, Vaughan DE, Stampfer MJ, Manson JE, Hennekens CH. Endogenous tissue-type
plasminogen activator and risk of myocardial infarction. Lancet 1993; 341:1165-1168.
8. Ridker PM, Hennekens CH, Cerskus A, Stampfer MJ. Plasma concentration of cross-linked
fibrin degradation product (d-Dimer) and the risk of future myocardial infarction
among apparently healthy men. Circulation 1994;90:2236-2240.
9. Kuller LH, Tracy RP, Shaten J, Meilahn EN, for the MRFIT Research Group. Relationship
of C-reactive protein and coronary heart disease in the MRFIT nested case-control
study. Am J Epidimiology 1996;144:537-47.
10. Das I. Raised C-reactive protein levels in serum from smokers. Clinica Chimica
Acta 1985;153:9-13.
11. Thompson SG, Kienast J, Pyke SDM, Haverkate F, van de Loo JCW, for the European
Concerted Action on Thrombosis and Disabilities Angina Pectoris Study Group. Hemostatic
factors and the risk of myocardial infarction or sudden death in patients with angina
pectoris. N Engl J Med 1995;332:635-41.
12. Liuzzo G, Biasucci LM, Gallimore JR, et al. The prognostic value of C-reactive
protein and serum amyloid A protein in severe unstable angina. N Engl J Med 1994;331:417-24.
13. Buja LM. Does atherosclerosis have an infectious etiology? Circulation 1996; 94:872-873.
14. Grayston JT. Chlamydia in atherosclerosis. Circulation 1993;87:1408-1409.
15. Saikku P, Leinonen M, Tenkanen L, et al. Chronic chlamydia pneumoniae infection as a risk factor for coronary heart disease in the Helsinki Heart Study.
Ann Intern Med 1992; 116:273-278.
16. Thom DH, Grayston JT, Siscovick DS, Wang S-P, Weiss NS, Daling JR. Association
of prior infection with chlamydia pneumoniae and angiographically demonstrated coronary
artery disease. JAMA 1992;268:68-72.
17. Melnick JL, Adam E, DeBakey ME. Possible role of cytomegalovirus in atherogenesis.
JAMA 1990;263;2204-7.
18. Mendall MA, Goggin PM, Molineaux N, et al. Relation of helicobacter pylori infection and coronary heart disease. Br Heart J 1994;71;437-9.
19. Patel P, Mendall MA, Carrington D, et al. Association of helicobacter pylori and chlamydia pneumoniae infections with coronary heart disease and cardiovascular risk factors. Br Med J
1995;311:711-4.
20. Bataille R, Klein B. C-reactive protein levels as a direct indicator of interleukin-6
levels in humans in vivo. Arthritis and Rheumatism 1992;35:982-984.
21. Biasucci LM, Vitelli A, Liuzzo G, et al. Elevated levels of interleukin-6 in unstable
angina. Circulation 1996;94:874-877.
22. Cermak J, Key NS, Bach RR, et al. C-reactive protein induces human peripheral
blood monocytes to synthesize tissue factor. Blood 1993;82:513-20.