CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser. No. 12/710,167, filed Feb. 22, 2010, which is a continuation of U.S. patent application Ser. No. 11/344,404, filed Jan. 30, 2006, now abandoned, which is a continuation-in-part of U.S. patent application Ser. No. 11/015,196, filed Dec. 16, 2004, now U.S. Pat. No. 7,786,133, which claims priority to U.S. Provisional Patent Application No. 60/530,122, filed Dec. 16, 2003, all four applications of which are incorporated herein by reference in their entireties.
FIELD OF THE INVENTION
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This invention provides chemically modified small molecules and related methods that possess certain advantages over small molecules lacking the chemical modification. The chemically modified small molecules described herein relate to and/or have application(s) in the fields of drug discovery, pharmacotherapy, physiology, organic chemistry, polymer chemistry, and others.
BACKGROUND OF THE INVENTION
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The use of proteins as active agents has expanded in recent years due to several factors: improved techniques for identifying, isolating, purifying and/or recombinantly producing proteins; increased understanding of the roles of proteins in vivo due to the emergence of proteonomics; and improved formulations, delivery vehicles and approaches for chemically modifying proteins to enhance their pharmacokinetic or phamacodynamic properties. With respect to improved approaches for chemically modifying proteins, covalent attachment of a polymer such as poly(ethylene glycol) or PEG to a protein has been used to improve the circulating half-life, decrease immunogenicity, and/or reduce proteolytic degradation. This approach of covalently attaching PEG to a protein or other active agent is commonly referred to as PEGylation. Proteins for injection that are modified by covalent attachment of PEGs are typically modified by attachment of relatively high molecular weight PEG polymers that often range from about 5,000 to about 40,000 Daltons.
While modification of relatively large proteins for the purpose of improving their pharmaceutical utility is perhaps one of the most common applications of PEGylation, PEGylation has also been used, albeit to a limited degree, to improve the bioavailability and ease of formulation of small molecule drugs having poor aqueous solubilities. For instance, water-soluble polymers such as PEG have been covalently attached to artilinic acid to improve its aqueous solubility. See, for example, U.S. Pat. No. 6,461,603. Similarly, PEG has been covalently attached to triazine-based compounds such as trimelamol to improve their solubility in water and enhance their chemical stability. See, for example, International Patent Publication WO 02/043772. Covalent attachment of PEG to bisindolyl maleimides has been employed to improve poor bioavailability of such compounds due to low aqueous solubility. See, for example, International Patent Publication WO 03/037384. PEG chains attached to small molecule drugs for the purpose of increasing their aqueous solubility are typically of sizes ranging from about 500 Daltons to about 5000 Daltons, depending upon the molecular weight of the small molecule drug.
Active agents can be dosed by any of a number of administration routes including injection, oral, inhalation, nasal, and transdermal. One of the most preferred routes of administration, due to its ease, is oral administration. Oral administration, most common for small molecule drugs (i.e., non-protein-based drugs), is convenient and often results in greater patient compliance when compared to other routes of administration. Unfortunately, many small molecule drugs possess properties (e.g., low oral bioavailability) that render oral administration impractical. Often, the properties of small molecule drugs that are required for dissolution and selective diffusion through various biological membranes directly conflict with the properties required for optimal target affinity and administration. The primary biological membranes that restrict entrance of small molecule drugs into certain organs or tissues are membranes associated with certain physiological barriers, e.g., the blood-brain barrier, the blood-placental barrier, and the blood-testes barrier.
The blood-brain barrier protects the brain from most toxicants. Specialized cells called astrocytes possess many small branches, which form a barrier between the capillary endothelium and the neurons of the brain. Lipids in the astrocyte cell walls and very tight junctions between adjacent endothelial cells limit the passage of water-soluble molecules. Although the blood-brain barrier does allow for the passage of essential nutrients, the barrier is effective at eliminating the passage of some foreign substances and can decrease the rate at which other substances cross into brain tissue.
The placental barrier protects the developing and sensitive fetus from many toxicants that may be present in the maternal circulation. This barrier consists of several cell layers between the maternal and fetal circulatory vessels in the placenta. Lipids in the cell membranes limit the diffusion of water-soluble toxicants. Other substances such as nutrients, gases, and wastes of the developing fetus can, however, pass through the placental barrier. As in the case of the blood-brain barrier, the placental barrier is not totally impenetrable but effectively slows down the diffusion of many toxicants from the mother to the fetus in the art.
For many orally administered drugs, permeation across certain biological membranes such as the blood-brain barrier or the blood-placental barrier is highly undesirable and can result in serious side-effects such as neurotoxicity, insomnia, headache, confusion, nightmares or teratogenicity. These side effects, when severe, can be sufficient to halt the development of drugs exhibiting such undesirable brain or placental uptake.
U.S. Published Application No. 2003/0161791 A1, published Aug. 28, 2003, discloses water-soluble polymer conjugates of retinoic acid. The conjugates are prepared by covalent attachment of a water-soluble polymer such as polyethylene glycol to a retinoid such as retinoic acid. The conjugates are useful for inhalation therapy of conditions of the respiratory tract.
Thus, there is a need for new methods for effectively delivering drugs, and in particular small molecule drugs, to a patient while simultaneously reducing the adverse and often toxic side-effects of small molecule drugs. Specifically, there is a need for improved methods for delivering drugs that possess an optimal balance of good oral bioavailability, bioactivity, and pharmacokinetic profile. The present invention meets this and other needs.
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OF THE INVENTION
The invention provides methods of modifying the rate of systemic absorption of a drug administered to a subject by a pulmonary route, the method comprising covalently conjugating a hydrophilic polymer to a drug, wherein the unconjugated drug has a half-life of elimination from the lung of less than about 180 minutes, to form a drug-polymer conjugate, wherein the drug-polymer conjugate has a net hydrophilic character and a weight average molecular weight of from about 50 to about 20,000 Daltons, and wherein the half-life of elimination from the lung of the drug-polymer conjugate is at least about 1.5-fold greater than the half-life of elimination from the lung of the unconjugated drug. In some embodiments, the half-life of elimination from the lung of the drug-polymer conjugate is at least about 2-fold, 4-fold, 10-fold, 20-fold, 50-fold, 100-fold, or 500-fold greater than the half-life of elimination from the lung of the unconjugated drug.
In some embodiments, the hydrophilic polymer comprises a polymer chosen from polyethylene glycols and polyethylene oxides. In some embodiments, the weight average molecular weight of the polymer is from about 1000 to about 3500 Daltons. In some embodiments, the drug has a molecular weight of less than about 1500.
The hydrophilic polymer may comprise a polyethylene glycol, including for example, linear polyethylene glycols, branched polyethylene glycols, forked polyethylene glycols, and dumbbell polyethylene glycols. In some embodiments, the hydrophilic polymer comprises a polymer from a polydisperse population. In some embodiments, the hydrophilic polymer is a polymer chosen from monodisperse, bimodal, trimodal, or tetramodal polymer populations.
The invention also provides methods of controlling the lung residence time of a drug pulmonarily administered, comprising covalently attaching to the drug a hydrophilic polymer molecule having a weight average molecular weight of from about 50 to about 4000 Daltons, to form a drug-polymer conjugate. The hydrophilic polymer may be polyethylene glycol. The weight average molecular weight of the hydrophilic polymer is, in some embodiments, from about 1000 to about 3500 Daltons. In some embodiments, the drug has a molecular weight of less than about 1500. In some embodiments, the drug-polymer conjugate exhibits a net hydrophilic character.
The invention also provides methods of controlling the rate of systemic absorption of a drug pulmonarily administered comprising covalently attaching to the drug a hydrophilic polymer molecule having a weight average molecular weight of from about 50 to about 4000 Daltons, to form a drug-polymer conjugate.
The invention also provides pharmaceutical compounds for pulmonary administration comprising a drug covalently attached to a hydrophilic polymer, wherein the pharmaceutical compound has a net hydrophilic character, and wherein the weight average molecular weight of the hydrophilic polymer is from about 50 to about 3500 Daltons. In some embodiments, the invention provides compositions comprising the pharmaceutical compound according to the invention, and at least one pharmaceutically acceptable excipient, In some embodiments, the pharmaceutical composition is in liquid form, and in some embodiments, in dry form. The invention also provides aerosols comprising the composition according to the invention. The invention also provides inhaler devices including the compositions of the invention. In some embodiments, the compositions comprise particles having a mass median aerodynamic diameter (MMAD) of less than about 10 microns, or less than about 5 microns. In some embodiments, the composition comprises a dry powder. In some embodiments, the inhalers of the invention are characterized by an emitted dose of at least about 30 percent, The invention also provides spray-dried compositions.
In some embodiments of the invention, the hydrophilic polymer is covalently attached to the active ingredient molecule by a hydrolytically unstable linkage, which can be a linkage chosen from ester, thioester, and amide. In some embodiments, the hydrophilic polymer is covalently attached to the active ingredient by a hydrolytically stable linkage. In some embodiments, the hydrophilic polymer is polyethylene glycol, which may be chosen from linear polyethylene glycols, branched polyethylene glycols, forked polyethylene glycols, and dumbbell polyethylene glycols. The invention also provides unit dosage forms comprising the compositions according to the invention.
The invention also provides compounds according to the invention, wherein the weight average molecular weight of the hydrophilic polymer is from about 50 to about 3500 Daltons and wherein pulmonary administration of the compound results in a half-life of elimination from the lung that can be described by the equation, t1/2−el=12.84*(1−e−kMW), where k=0.000357, MW=molecular weight in Daltons, and t1/2=elimination half-life in hours. The invention also provides methods of treating a systemic disease comprising pulmonarily administering the compounds according to the invention.
These and other objects, aspects, embodiments and features of the invention will become more fully apparent when read in conjunction with the following detailed description.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a plot of plasma concentration versus time for 13-cis retinoic acid (“13-cis-RA”) and exemplary small PEG conjugates thereof (PEG3-13-cis retinamide, “PEG3-13-cis RA”; PEG5-13-cis retinamide, “PEG5-13-cis RA; PEG7-13-cis retinamide, “PEG7-13-cis RA; and PEGI1-13-cis retinamide, “PEG11-13-cis RA”) administered to Sprague Dawley rats as described in detail in Example 7.
FIG. 2 is a plot of plasma concentration versus time for 6-naloxol and exemplary small PEG conjugates thereof (3-mer, 5-mer, 7-mer) administered to Sprague Dawley rats as described in detail in Example 7.
FIG. 3 is a plot demonstrating the effect PEG chain length on the intestinal transport (as an indicator of oral bioavailability) of various PEG-13-cis-RA conjugates and 13-cis-RA in Sprague-Dawley rats.
FIG. 4 is a plot demonstrating the effect of covalent attachment of various sized PEG-mers on the blood-brain barrier transport of 13-cis-RA and various PEG-13-cis-RA conjugates.
FIG. 5 is a plot demonstrating the effect of covalent attachment of various sized PEG-mers on the intestinal transport (as an indicator of oral bioavailability) of naloxone and PEGn-Nal.
FIG. 6 is a plot showing the effect of covalent attachment of various sized PEG-mers on the blood-brain barrier transport of naloxone and PEGn-Nal.
FIG. 7 is a plot demonstrating the pharmacokinetics of naloxone and PEGn-Nal in rats following oral gavage.
FIG. 8 and FIG. 9 are plots demonstrating the effect of covalent attachment of various sized PEG-mers on the level of naloxone metabolites and PEGn-Nal metabolites.
FIG. 10 is mass spectrum of methoxy-PEG-350 obtained from a commercial source (Sigma-Aldrich). As can be seen from the analysis, although the reagent is sold as methoxy-PEG having a molecular weight of 350, the reagent is actually a mixture of nine distinct PEG oligomers, with the number of monomer subunits ranging from approximately 7 to approximately 15.
FIG. 11 diagrammatically shows the experimental strategy of Example 12.
FIG. 12 shows the elimination of PEG-FITC from BAL.
FIG. 13 shows the relationship between MW and Elimination half-life from BAL for a PEG-FITC conjugate.
FIG. 14 shows the uptake of PEG-FITC into BAL cells.
FIG. 15 shows the percentage dose of PEG-FITC that associates with the cellular fraction of BAL.
FIG. 16 shows the association of PEG-FITC with residual lung material.
FIG. 17 shows the concentration of PEG-FITC in serum.
FIGS. 18A and 18B show the total mass recovered in lung-derived fractions.
FIGS. 19A and 19B show the elimination of PEG-FITC from all combined lung compartments.
FIG. 20 shows in vitro permeability for Calu-3 cell studies.
FIG. 21 illustrates cell-based permeability plotted versus the in vivo absorption rate.
FIG. 22 shows the relationship between log P and PEG size for PEG-FITC conjugates.
FIG. 23 shows elimination from the lung for 2K PEG and 2K PEG-FITC.
FIG. 24 shows that increasing the dose of 2K PEG 10-fold does not significantly alter the elimination rate from the lung.
FIG. 25 shows the rate of disappearance from the lung of CIPRO and PEG-CIPRO conjugates.
FIG. 26 shows the rate in appearance of the plasma of CIPRO and PEG-CIPRO.
FIG. 27 shows the rate of appearance in the plasma of CIPRO.
FIG. 28 shows steroid-induced nuclear translocation assay of GR in CHO cells.
FIG. 29 shows the activation of Luciferase by TAA, PEG-3-TA, and PEG-7-TA.
FIG. 30 shows the time course activation of Luciferase by TAA.
FIG. 31 shows the difference in binding affinity between TA and the PEG-TA derivatives.
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OF THE INVENTION
It must be noted that, as used in this specification, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. In describing and claiming the present invention, the following terminology will be used in accordance with the definitions described below.
“Water soluble” as in a “water-soluble oligomer” indicates an oligomer that is at least 35% (by weight) soluble, preferably greater than 95% soluble, and more preferably greater than 99% soluble, in water at room temperature at physiological pH (about 7.2-7.6). Typically, an unfiltered aqueous preparation of a “water-soluble” oligomer transmits at least 75%, more preferably at least 95%, of the amount of light transmitted by the same solution after filtering. On a weight basis, a “water soluble” oligomer is preferably at least 35% (by weight) soluble in water, more preferably at least 50% (by weight) soluble in water, still more preferably at least 70% (by weight) soluble in water, and still more preferably at least 85% (by weight) soluble in water. It is most preferred, however, that the water-soluble oligomer is at least 95% (by weight) soluble in water or completely soluble in water.
The terms “monomer,” “monomeric subunit” and “monomeric unit” are used interchangeably herein and refer to one of the basic structural units of a polymer or oligomer. In the case of a homo-oligomer, this is defined as a structural repeating unit of the oligomer. In the case of a co-oligomer, a monomeric unit is more usefully defined as the residue of a monomer that was oligomerized to form the oligomer, since the structural repeating unit can include more than one type of monomeric unit. Preferred oligomers of the invention are homo-oligomers.
An “oligomer” is a molecule possessing from about 1 to about 30 monomers. The architecture of an oligomer can vary. Specific oligomers for use in the invention include those having a variety of geometries such as linear, branched, or forked, to be described in greater detail below. An oligomer is a type of polymer.
“PEG” or “polyethylene glycol,” as used herein, is meant to encompass any water-soluble poly(ethylene oxide). Unless otherwise indicated, a “PEG oligomer” or an oligoethylene glycol is one in which all of the monomer subunits are ethylene oxide subunits. Typically, substantially all, or all, monomeric subunits are ethylene oxide subunits, though the oligomer may contain distinct end capping moieties or functional groups, e.g. for conjugation. Typically, PEG oligomers for use in the present invention will comprise one of the two following structures: “—(CH2CH2O)n—” or “—(CH2CH2O)n−1CH2CH2—,” depending upon whether or not the terminal oxygen(s) has been displaced, e.g., during a synthetic transformation. As stated above, for the PEG oligomers of the invention, the variable (n) ranges from 1 to 30, and the terminal groups and architecture of the overall PEG can vary. When PEG further comprises a functional group, A, for linking to, e.g., a small molecule drug, the functional group when covalently attached to a PEG oligomer, does not result in formation of (i) an oxygen-oxygen bond (—O—O—, a peroxide linkage), or (ii) a nitrogen-oxygen bond (N—O, O—N).
An “end capping group” is generally anon-reactive carbon-containing group attached to a terminal oxygen of a PEG oligomer. For the purposes of the present invention, preferred are capping groups having relatively low molecular weights such as methyl or ethyl. The end-capping group can also comprise a detectable label. Such labels include, without limitation, fluorescers, chemiluminescers, moieties used in enzyme labeling, colorimetric labels (e.g., dyes), metal ions, and radioactive moieties.
“Branched”, in reference to the geometry or overall structure of an oligomer, refers to an oligomer having two or more polymer “arms” extending from a branch point.
“Forked” in reference to the geometry or overall structure of an oligomer, refers to an oligomer having two or more functional groups (typically through one or more atoms) extending from a branch point.
A “branch point” refers to a bifurcation point comprising one or more atoms at which an oligomer branches or forks from a linear structure into one or more additional arms.
The term “reactive” or “activated” refers to a functional group that reacts readily or at a practical rate under conventional conditions of organic synthesis. This is in contrast to those groups that either do not react or require strong catalysts or impractical reaction conditions in order to react (i.e., a “nonreactive” or “inert” group).
“Not readily reactive,” with reference to a functional group present on a molecule in a reaction mixture, indicates that the group remains largely intact under conditions effective to produce a desired reaction in the reaction mixture.
A “protecting group” is a moiety that prevents or blocks reaction of a particular chemically reactive functional group in a molecule under certain reaction conditions. The protecting group will vary depending upon the type of chemically reactive group being protected as well as the reaction conditions to be employed and the presence of additional reactive or protecting groups in the molecule. Functional groups which may be protected include, by way of example, carboxylic acid groups, amino groups, hydroxyl groups, thiol groups, carbonyl groups and the like. Representative protecting groups for carboxylic acids include esters (such as a p-methoxybenzyl ester), amides and hydrazides; for amino groups, carbamates (such as tert-butoxycarbonyl) and amides; for hydroxyl groups, ethers and esters; for thiol groups, thioethers and thioesters; for carbonyl groups, acetals and ketals; and the like. Such protecting groups are well-known to those skilled in the art and are described, for example, in T. W. Greene and G. M. Wuts, Protecting Groups in Organic Synthesis, Third Edition, Wiley, New York, 1999, and references cited therein.
A functional group in “protected form” refers to a functional group bearing a protecting group. As used herein, the term “functional group” or any synonym thereof is meant to encompass protected forms thereof.
A “physiologically cleavable” or “hydrolyzable” or “degradable” bond is a relatively labile bond that reacts with water (i.e., is hydrolyzed) under physiological conditions. The tendency of a bond to hydrolyze in water will depend not only on the general type of linkage connecting two central atoms but also on the substituents attached to these central atoms. Appropriate hydrolytically unstable or weak linkages include but are not limited to carboxylate ester, phosphate ester, anhydrides, acetals, ketals, acyloxyalkyl ether, imines, orthoesters, peptides, oligonucleotides, thioesters, thiolesters, and carbonates.
An “enzymatically degradable linkage” means a linkage that is subject to degradation by one or more enzymes.
A “hydrolytically stable” linkage or bond refers to a chemical bond, typically a covalent bond, that is substantially stable in water, that is to say, does not undergo hydrolysis under physiological conditions to any appreciable extent over an extended period of time. Examples of hydrolytically stable linkages include but are not limited to the following: carbon-carbon bonds (e.g., in aliphatic chains), ethers, amides, urethanes, amines, and the like. Generally, a hydrolytically stable linkage is one that exhibits a rate of hydrolysis of less than about 1-2% per day under physiological conditions. Hydrolysis rates of representative chemical bonds can be found in most standard chemistry textbooks.
“Substantially” or “essentially” means nearly totally or completely, for instance, 95% or greater, more preferably 97% or greater, still more preferably 98% or greater, even more preferably 99% or greater, yet still more preferably 99.9% or greater, with 99.99% or greater being most preferred of some given quantity.
“Monodisperse” refers to an oligomer composition wherein substantially all of the oligomers in the composition have a well-defined, single (i.e., the same) molecular weight and defined number of monomers, as determined by chromatography or mass spectrometry. Monodisperse oligomer compositions are in one sense pure, that is, substantially having a single and definable number as a whole number) of monomers rather than a large distribution. A monodisperse oligomer composition of the invention possesses a MW/Mn value of 1.0005 or less, and more preferably, a MW/Mn value of 1.0000. By extension, a composition comprised of monodisperse conjugates means that substantially all oligomers of all conjugates in the composition have a single and definable number (as a whole number) of monomers rather than a large distribution and would possess a MW/Mn value of 1.0005 or less, and more preferably, a MW/Mn value of 1.0000 if the oligomer were not attached to the moiety derived from a small molecule drug. A composition comprised of monodisperse conjugates can, however, include one or more nonconjugate substances such as solvents, reagents, excipients, and so forth.
“Bimodal,” in reference to an oligomer composition, refers to an oligomer composition wherein substantially all oligomers in the composition have one of two definable and different numbers (as whole numbers) of monomers rather than a large distribution, and whose distribution of molecular weights, when plotted as a number fraction versus molecular weight, appears as two separate identifiable peaks. Preferably, for a bimodal oligomer composition as described herein, each peak is symmetric about its mean, although the size of the two peaks may differ. Ideally, the polydispersity index of each peak in the bimodal distribution, Mw/Mn, is 1.01 or less, more preferably 1.001 or less, and even more preferably 1.0005 or less, and most preferably a MW/Mn value of 1.0000. By extension, a composition comprised of bimodal conjugates means that substantially all oligomers of all conjugates in the composition have one of two definable and different numbers (as whole numbers) of monomers rather than a large distribution and would possess a MW/Mn value of 1.01 or less, more preferably 1.001 or less and even more preferably 1.0005 or less, and most preferably a MW/Mn value of 1.0000 if the oligomer were not attached to the moiety derived from a small molecule drug. A composition comprised of bimodal conjugates can, however, include one or more nonconjugated substances such as solvents, reagents, excipients, and so forth.
“Polydisperse” in reference to a polymer, refers to a composition having a polymer present in a distribution of molecular weights. The distribution generally will be a normal distribution, i.e., one that has a higher concentration of polymers with molecular weights near the mean, with a decrease in frequency as the difference from the mean molecular weight increases. The distribution may be a Gaussian distribution.
A “drug” is broadly used herein to refer to an organic, inorganic, or organometallic compound typically having a molecular weight of less than about 1500. Drugs of the invention encompass oligopeptides and other biomolecules having a molecular weight of less than about 1500. Peptide drugs of the invention have a molecular weight of less than about 1500 Daltons. It will be understood that the term “drug” refers to any drug in its active form, any prodrug, and any active ingredient. “Drug” as used herein includes any agent, compound, composition of matter or mixture which provides some pharmacologic, often beneficial, effect that can be demonstrated in vivo or in vitro. This includes foods, food supplements, nutrients, nutriceuticals, drugs, vaccines, antibodies, vitamins, and other beneficial agents. As used herein, these terms further include any physiologically or pharmacologically active substance that produces a localized or systemic effect in a patient. “Small molecule,” “small molecule drug,” and “drug” are used interchangeably herein.
The terms “moiety derived from a small molecule drug” and “small molecule drug moiety” are used interchangeably herein to refer to the portion or residue of the parent small molecule drug up to the covalent linkage resulting from covalent attachment of the drug (or an activated or chemically modified form thereof) to an oligomer of the invention.
A “biological membrane” is any membrane, typically made from specialized cells or tissues, that serves as a barrier to at least some xenobiotics or otherwise undesirable materials. As used herein a “biological membrane” includes those membranes that are associated with physiological protective barriers including, for example: the blood-brain barrier; the blood-cerebrospinal fluid barrier; the blood-placental barrier; the blood-milk barrier; the blood-testes barrier; and mucosal barriers including the vaginal mucosa, urethral mucosa, anal mucosa, buccal mucosa, sublingual mucosa, rectal mucosa, and so forth). Unless the context clearly dictates otherwise, the term “biological membrane” does not include those membranes associated with the middle gastro-intestinal tract (e.g., stomach and small intestines).
A “biological membrane crossing rate,” as used herein, provides a measure of a compound\'s ability to cross a biological barrier, such as the blood-brain barrier (“BBB”). A variety of methods can be used to assess transport of a molecule across any given biological membrane. Methods to assess the biological membrane crossing rate associated with any given biological barrier (e.g., the blood-cerebrospinal fluid barrier, the blood-placental barrier, the blood-milk barrier, the intestinal barrier, and so forth), are known, described herein and/or in the relevant literature, and/or can be determined by one of ordinary skill in the art.
A compound that “crosses the blood-brain barrier” in accordance with the invention is one that crosses the BBB at urate greater than that of atenolol using the methods as described herein.
A “reduced rate of metabolism” in reference to the present invention, refers to a measurable reduction in the rate of metabolism of a water-soluble oligomer-small molecule drug conjugate as compared to rate of metabolism of the small molecule drug not attached to the water-soluble oligomer (i.e., the small molecule drug itself) or a reference standard material. In the special case of “reduced first pass rate of metabolism,” the same “reduced rate of metabolism” is required except that the small molecule drug (or reference standard material) and the corresponding conjugate are administered orally. Orally administered drugs are absorbed from the gastro-intestinal tract into the portal circulation and must pass through the liver prior to reaching the systemic circulation. Because the liver is the primary site of drug metabolism or biotransformation, a substantial amount of drug can be metabolized before it ever reaches the systemic circulation. The degree of first pass metabolism, and thus, any reduction thereof, can be measured by a number of different approaches. For instance, animal blood samples can be collected at timed intervals and the plasma or serum analyzed by liquid chromatography/mass spectrometry for metabolite levels. Other techniques for measuring a “reduced rate of metabolism” associated with the first pass metabolism and other metabolic processes are known, described herein and/or in the relevant literature, and/or can be determined by one of ordinary skill in the art. Preferably, a conjugate of the invention can provide a reduced rate of metabolism reduction satisfying at least one of the following values: at least about 5%, at least about 10%, at least about 15%; least about 20%; at least about 25%; at least about 30%; at least about 40%; at least about 50%; at least about 60%; at least about 70%; at least about 80%; and at least about 90%.
A compound (such as a small molecule drug or conjugate thereof) that is “orally bioavailable” is one that possesses a bioavailability when administered orally of greater than 1%, and preferably greater than 10%, where a compound\'s bioavailability is the fraction of administered drug that reaches the systemic circulation in unmetabolized form.
“Alkyl” refers to a hydrocarbon chain, typically ranging from about 1 to 20 atoms in length. Such hydrocarbon chains are preferably but not necessarily saturated and may be branched or straight chain, although typically straight chain is preferred. Exemplary alkyl groups include methyl, ethyl, propyl, butyl, pentyl, 1-methylbutyl, 1-ethylpropyl, 3-methylpentyl, and the like. As used herein, “alkyl” includes cycloalkyl when three or more carbon atoms are referenced.
“Lower alkyl” refers to an alkyl group containing from 1 to 6 carbon atoms, and may be straight chain or branched, as exemplified by methyl, ethyl, n-butyl, i-butyl, t-butyl
“Non-interfering substituents” are those groups that, when present in a molecule, are typically non-reactive with other functional groups contained within the molecule.
“Alkoxy” refers to an —O—R group, wherein R is alkyl or substituted alkyl, preferably C1-C20 alkyl (e.g., methoxy, ethoxy, propyloxy, benzyl, etc.), preferably C1-C7.
“Electrophile” refers to an ion, atom, or an ionic or neutral collection of atoms having an electrophilic center, i.e., a center that is electron seeking, capable of reacting with a nucleophile.
“Nucleophile” refers to an ion or atom or an ionic or neutral collection of atoms having a nucleophilic center, i.e., a center that is seeking an electrophilic center, and capable of reacting with an electrophile.
“Pharmaceutically acceptable excipient” or “pharmaceutically acceptable carrier” refers to an excipient that can be included in the compositions of the invention and that causes no significant adverse toxicological effects to the patient.
“Pharmacologically effective amount,” “physiologically effective amount,” and “therapeutically effective amount” are used interchangeably herein to mean the amount of a water-soluble oligomer-small molecule drug conjugate present in a composition that is needed to provide a desired level of active agent and/or conjugate in the bloodstream or in the target tissue. The precise amount will depend upon numerous factors, e.g., the particular active agent, the components and physical characteristics of the composition, intended patient population, patient considerations, and the like, and can readily be determined by one skilled in the art, based upon the information provided herein and available in the relevant literature.