US20130143909A1 - Acid Salt Forms of Polymer-Drug Conjugates and Alkoxylation Methods - Google Patents

Acid Salt Forms of Polymer-Drug Conjugates and Alkoxylation Methods Download PDF

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US20130143909A1
US20130143909A1 US13/510,555 US201013510555A US2013143909A1 US 20130143909 A1 US20130143909 A1 US 20130143909A1 US 201013510555 A US201013510555 A US 201013510555A US 2013143909 A1 US2013143909 A1 US 2013143909A1
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polymer
salt
active agent
conjugate
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Anthony O. Chong
Seoju Lee
Bhalchandra V. Joshi
Brian Bray
Shaoyong Nie
Patrick L. Spence
Antoni Kozlowski
Samuel P. McManus
Sachin Tipnis
Greg Lavaty
David Swallow
John R. Handley
Anthony G. Schaefer
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Nektar Therapeutics
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Nektar Therapeutics
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Assigned to NEKTAR THERAPEUTICS reassignment NEKTAR THERAPEUTICS ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SWALLOW, DAVID, TIPNIS, SACHIN, LEE, SEOJU, MCMANUS, SAMUEL P., HANDLEY, JOHN R., SCHAEFER, ANTHONY G., BRAY, BRIAN, KOZLOWSKI, ANTONI, CHONG, ANTHONY O., JOSHI, BHALCHANDRA V., NIE, SHAOYONG, SPENCE, PATRICK L.
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    • A61K47/00—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient
    • A61K47/50—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates
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    • A61K47/60—Medicinal preparations characterised by the non-active ingredients used, e.g. carriers or inert additives; Targeting or modifying agents chemically bound to the active ingredient the non-active ingredient being chemically bound to the active ingredient, e.g. polymer-drug conjugates the non-active ingredient being a modifying agent the modifying agent being an organic macromolecular compound, e.g. an oligomeric, polymeric or dendrimeric molecule obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, e.g. polyureas or polyurethanes the organic macromolecular compound being a polyoxyalkylene oligomer, polymer or dendrimer, e.g. PEG, PPG, PEO or polyglycerol
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    • C08G65/32—Polymers modified by chemical after-treatment
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    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K31/00—Medicinal preparations containing organic active ingredients
    • A61K31/33—Heterocyclic compounds
    • A61K31/395—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins
    • A61K31/435—Heterocyclic compounds having nitrogen as a ring hetero atom, e.g. guanethidine or rifamycins having six-membered rings with one nitrogen as the only ring hetero atom
    • A61K31/47—Quinolines; Isoquinolines
    • A61K31/4738—Quinolines; Isoquinolines ortho- or peri-condensed with heterocyclic ring systems
    • A61K31/4745—Quinolines; Isoquinolines ortho- or peri-condensed with heterocyclic ring systems condensed with ring systems having nitrogen as a ring hetero atom, e.g. phenantrolines
    • A61K47/48215—
    • A—HUMAN NECESSITIES
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    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P1/00—Drugs for disorders of the alimentary tract or the digestive system
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61P11/00—Drugs for disorders of the respiratory system
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P15/00—Drugs for genital or sexual disorders; Contraceptives
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P35/00—Antineoplastic agents
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
    • C07C51/41—Preparation of salts of carboxylic acids
    • C07C51/412—Preparation of salts of carboxylic acids by conversion of the acids, their salts, esters or anhydrides with the same carboxylic acid part
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C53/00—Saturated compounds having only one carboxyl group bound to an acyclic carbon atom or hydrogen
    • C07C53/15—Saturated compounds having only one carboxyl group bound to an acyclic carbon atom or hydrogen containing halogen
    • C07C53/16—Halogenated acetic acids
    • C07C53/18—Halogenated acetic acids containing fluorine
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D491/00—Heterocyclic compounds containing in the condensed ring system both one or more rings having oxygen atoms as the only ring hetero atoms and one or more rings having nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D451/00 - C07D459/00, C07D463/00, C07D477/00 or C07D489/00
    • C07D491/22—Heterocyclic compounds containing in the condensed ring system both one or more rings having oxygen atoms as the only ring hetero atoms and one or more rings having nitrogen atoms as the only ring hetero atoms, not provided for by groups C07D451/00 - C07D459/00, C07D463/00, C07D477/00 or C07D489/00 in which the condensed system contains four or more hetero rings
    • C—CHEMISTRY; METALLURGY
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    • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
    • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
    • C08G65/32—Polymers modified by chemical after-treatment
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
    • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
    • C08G65/32—Polymers modified by chemical after-treatment
    • C08G65/329—Polymers modified by chemical after-treatment with organic compounds
    • C08G65/333—Polymers modified by chemical after-treatment with organic compounds containing nitrogen
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
    • C08G65/34—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from hydroxy compounds or their metallic derivatives
    • C08G65/48—Polymers modified by chemical after-treatment
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2203/00—Applications
    • C08L2203/02—Applications for biomedical use

Definitions

  • This disclosure relates generally to mixed acid salt compositions of water-soluble polymer-drug conjugates, pharmaceutical compositions thereof, and methods for preparing, formulating, administering and using such mixed acid salt compositions.
  • This disclosure also relates generally to alkoxylation methods for preparing alkoxylated polymeric materials from a previously isolated alkoxylated oligomer, as well as to compositions comprising the alkoxylated polymeric material, methods for using the alkoxylated polymeric material, and the like.
  • Covalent attachment of a water-soluble polymer can improve the water-solubility of an active agent as well as alter its pharmacological properties.
  • Certain exemplary polymer conjugates are described in U.S. Pat. No. 7,744,861, among others.
  • an active agent having acidic or basic functionalities can be reacted with a suitable base or acid and marketed in salt form. Over half of all active molecules are marketed as salts ( Polymorphism in the Pharmaceutical Industry , Hilfiker, R., ed., Wiley-VCH, 2006). Challenges with salt forms include finding an optimal salt, as well as controlling solid state behavior during processing.
  • Biopharmaceutical salts can be amorphous, crystalline, and exist as hydrates, solvents, various polymorphs, etc. Interestingly, rarely are salt forms, let alone mixed acid salt forms, of polymer conjugates used in drug formulations.
  • PEG poly(ethylene glycol)
  • active agent conjugates of water-soluble polymers waters Another challenge associated with preparing active agent conjugates of water-soluble polymers waters is the ability to prepare relatively pure water-soluble polymers in a consistent and reproducible method.
  • PEG poly(ethylene glycol)
  • active agents such as small molecules and proteins
  • an active agent is conjugated to a polymer of poly(ethylene glycol) or “PEG,” the conjugated active agent is conventionally referred to as having been “PEGylated.”
  • the conjugated version When compared to the safety and efficacy of the active agent in the unconjugated form, the conjugated version exhibits different, and often clinically beneficial, properties.
  • PEGylated active agents such as PEGASYS® PEGylated interferon alpha-2a (Hoffmann-La Roche, Nutley, N.J.), PEG-INTRON® PEGylated interferon alpha-2b (Schering Corp., Kenilworth, N.J.), and NEULASTA® PEG-filgrastim (Amgen Inc., Thousand Oaks, Calif.) demonstrates the degree to which PEGylation has the potential to improve one or more properties of an active agent.
  • a polymeric reagent is typically employed to allow for a relatively straightforward synthetic approach for conjugate synthesis.
  • a composition comprising a polymeric reagent with a composition comprising the active agent, it is possible—under the appropriate reaction conditions—to carry out a relatively convenient conjugate synthesis.
  • a composition comprising mixed salts of water soluble polymer-active agent conjugates, wherein the active agent in the conjugate has at least one amine or other basic nitrogen-containing group, and further wherein the amine or other basic nitrogen-containing group is either protonated or unprotonated (i.e., as the free base), where any given protonated amine or other basic nitrogen containing group is an acid addition salt of either a strong inorganic acid or a strong organic acid such as, for example, trifluoroacetic acid (TFA).
  • TFA trifluoroacetic acid
  • strong inorganic acids include hydrohalic acids (e.g., hydrochloric acid, hydrofluoric, hydroiodic, and hydrobromic), sulfuric acid, nitric acid, phosphoric acid, and nitrous acid.
  • hydrohalic acids e.g., hydrochloric acid, hydrofluoric, hydroiodic, and hydrobromic
  • sulfuric acid e.g., sulfuric acid, nitric acid, phosphoric acid, and nitrous acid.
  • the protonated form comprises an addition salt of a hydrohalic acid.
  • the protonated form comprises an addition salt of hydrochloric acid.
  • Examples of strong organic acids include organic acids having a pKa of less than about 2.00. Examples include trichloroacetic acid, dichloroacetic acid, as well as mixed haloacetic acids such as fluorodichloroacetic acid, fluorochloroacetic acid, chlorodifluoroacetic acid and the like.
  • the water soluble polymer is linear or multi-armed.
  • the water soluble polymer is a poly(alkylene glycol) such as polyethylene glycol) or a copolymer or terpolymer thereof.
  • the active agent is selected from a small molecule drug, a peptide, and a protein.
  • the active agent is a camptothecin.
  • the composition comprises a mixed salt of a water-soluble polymer-active agent conjugate corresponding to structure (I):
  • n is an integer ranging from 20 to about 600 (specific protonated amino nitrogen atoms and counterions not shown), and for each amine group within each irinotecan, each amino group is either protonated or unprotonated, where any given protonated amine group is an acid salt form of an inorganic acid or an organic acid such as trifluoroacetic acid.
  • the mole percent of active agent amino groups (or other basic nitrogen atoms) in the composition that are protonated as the TFA salt is greater than each of the mole percent of active agent amino groups in the composition that are protonated as an inorganic acid salt and the mole percent of active agent amino groups in the composition in free base form.
  • the mole percent of active agent amine groups (or other basic nitrogen atoms) in the composition that are protonated as the TFA salt is greater than the mole percent of active agent amine groups in the composition that are in free base (i.e., unprotonated) form.
  • composition of conjugates e.g., a composition of four-arm conjugates
  • at least 20 mole percent of active agent amine groups in the composition are protonated as the TFA salt.
  • composition of conjugates e.g., a composition of four-arm conjugates
  • at least 25 mole percent of active agent amine groups in the composition are protonated as the TFA salt.
  • composition of conjugates e.g., a composition of four-arm conjugates
  • about 20-45 mole percent of active agent amino groups in the composition are protonated as the TFA salt.
  • composition of conjugates e.g., a composition of four-arm conjugates
  • about 24-38 mole percent of active agent amino groups in the composition are protonated as the TFA salt.
  • composition of conjugates e.g., a composition of thur-arm conjugates
  • about 35-65 mole percent of active agent amino groups in the composition are protonated as the TFA salt.
  • composition of conjugates e.g., a composition of four-arm conjugates
  • about 30-65 mole percent of the active agent amino groups in the composition are protonated as an inorganic acid salt (such as the HCl salt).
  • composition of conjugates e.g., a composition of four-arm conjugates
  • about 32-60 mole percent of the active agent amino groups in the composition are protonated as an inorganic acid salt (such as the HCl salt).
  • composition of conjugates e.g., a composition of four-arm conjugates
  • about 35-57 mole percent of the active agent amino groups in the composition are protonated as an inorganic acid salt (such as the HCl salt).
  • composition of conjugates e.g., a composition of four-arm conjugates
  • about 25-40 mole percent of the active agent amino groups in the composition are protonated as an inorganic acid salt (such as the HCl salt), and about 5-35 mole percent of the active agent amino groups in the composition are non-protonated (i.e., as the free base).
  • composition of conjugates e.g., a composition of four-arm conjugates
  • about 32-60 mole percent of the active agent amino groups in the composition are protonated as an inorganic acid salt (such as the HCl salt), and about 5-35 mole percent of the active agent amino groups in the composition are non-protonated (i.e., as the free base).
  • a trifluoroacetic acid/hydrochloric acid mixed salt of a conjugate having the following structure:
  • n is an integer ranging from about 20 to about 500 (including about 40 to about 500) (noting that in the above structure, specific basic nitrogen atoms in protonated form and corresponding anions are not shown).
  • a portion of amino groups in conjugate encompassed by the structure immediately above are non-protonated.
  • Exemplary molar ratios of protonated and non-protonated forms as provided above and further herein apply to the foregoing conjugate.
  • a method for providing a mixed salt of a water-soluble polymer-active agent conjugate comprising the steps of: (i) deprotecting an inorganic acid salt of an amine-containing active agent in protected form by treatment with trifluoroacetic acid (TFA) or other organic acid deprotecting reagent to form a deprotected active agent acid salt, (ii) coupling the deprotected active agent acid salt of step (i) with a water-soluble polymer reagent in the presence of a base (e.g., trimethyl amine, triethyl amine, and dimethylamino-pyridine) to form a polymer-active agent conjugate, and (iii) recovering the polymer-active agent conjugate, where the recovered polymer-active agent conjugate is characterized by having active agent amino groups therein individually present in a form selected from the group consisting of free base form (non-protonated), inorganic acid salt form, and TFA or other organic
  • the method further comprises determining the relative molar amounts of inorganic acid and TFA in the deprotected acid salt formed in step (i).
  • the inorganic acid salt in step (i) is a hydrohalic acid salt such as a hydrochloric acid salt.
  • the amount of base in step (ii) ranges from 1.00-2.00 (moles TFA+moles acid). In one or more related embodiments, the amount of base in step (ii) ranges from 1.00 to 1.50 (moles TFA+moles inorganic acid), where the parenthesis indicates multiplication.
  • the amount of base in step (ii) ranges from 1.00 to 1.20 (moles TFA+moles inorganic acid). In one particular embodiment, the number of equivalents of base is 1.05 ((moles TFA+moles inorganic acid).
  • the water-soluble polymer reagent is an activated polyethylene glycol ester (i.e., a polyethylene glycol reagent having at least one activated ester group). In one or more embodiments of the invention, the water-soluble polymer reagent is a polyethylene glycol reagent having three or more polymer arms.
  • the active agent amine groups in the polymer-active agent conjugate are selected from the group consisting of secondary amine groups and tertiary amine groups. In one or more embodiments of the invention, the active agent amine groups are tertiary amino groups. In yet another embodiment, the polymer-active agent conjugate comprises a basic nitrogen atom that, as its corresponding conjugate acid, has a pK a in a range of about 10-11.5.
  • the active agent is selected from a small molecule, a peptide and a protein.
  • the active agent is a camptothecin.
  • Illustrative camptothecin molecules are selected from camptothecin, irinotecan, and 7-ethyl-10-hydroxy-camptothecin (SN-38).
  • Exemplary sites for covalent attachment to a water-soluble polymer include the 7-, 10-, and 20- ring positions of the camptothecin skeleton, among others.
  • a pharmaceutically acceptable composition comprising (i) a mixed salt according to any one or more of the embodiments described herein, and (ii) lactate buffer, optionally in lyophilized form.
  • the pharmaceutically acceptable composition is a sterile composition.
  • the pharmaceutically acceptable composition is optionally provided in a container (e.g., a vial), optionally containing the equivalent of a 100-mg dose of irinotecan in unconjugated form.
  • a method comprising administering a conjugate-containing composition described herein (where the active agent is an anti-cancer agent) to an individual suffering from one or more types of cancerous solid tumors, wherein the conjugate-containing composition is optionally dissolved in a solution of 5% w/w dextrose.
  • administration is effected via intravenous infusion.
  • a method for preparing a mixed salt of a water-soluble polymer-active agent conjugate comprising the steps of: (i) deprotecting t-Boc glycine-irinotecan by treatment with trifluoroacetic acid (TFA) to form deprotected glycine-irinotecan HCl/TFA mixed salt, (ii) coupling the deprotected glycine-irinotecan HCl/TFA mixed salt with 4-arm-pentaerythritolyl-polyethylene glycol-carboxymethyl succinimide in the presence of a base under conditions effective to form a conjugate, 4-arm-pentaerythritolyl-polyethylene glycol-carboxymethyl glycine-irinotecan (also referred to as pentaerythritolyl-4-arm-(PEG-1-methylene-2-oxo-vinylamino acetate
  • the method further comprises purifying the conjugate (e.g., comprising recrystallizing the conjugate to form a recrystallized conjugate).
  • a recrystallized product is provided, the recrystallized product being a mixed acid salt comprising active agent amino groups existing as a combination of free base, HCl, and TFA salt forms.
  • a method of treating a mammal suffering from cancer comprising administering a therapeutically effective amount of a mixed salt of a water soluble polymer-camptothecin conjugate comprising a camptothecin having amine or other basic nitrogen containing groups in both free base and in protonated form, where the each protonated form exists as an acid addition salt of either a strong inorganic acid and trifluoroacetic acid.
  • the mixed acid salt is administered to the mammal effective to produce a slowing or inhibition of solid tumor growth in the subject.
  • the cancerous solid tumor is selected from the group consisting of colorectal, ovarian, cervical, breast and non-small cell lung.
  • a mixed acid salt of an active agent conjugate as described herein is provided, wherein the active is an anti-cancer agent for the manufacture of a medicament for treating cancer.
  • a method comprising the step of alkoxylating in a suitable solvent a previously isolated alkoxylatable oligomer to form an alkoxylated polymeric product, wherein the previously isolated alkoxylatable oligomer has a known and defined weight-average molecular weight of greater than 300 Daltons (e.g., greater than 500 Daltons).
  • a composition comprising an alkoxylated polymeric product prepared by a method comprising the step of alkoxylating in a suitable solvent a previously isolated alkoxylatable oligomer to form an alkoxylated polymeric product, wherein the previously isolated alkoxylatable oligomer has a known and defined weight-average molecular weight of greater than 300 Daltons (e.g., greater than 500 Daltons).
  • a composition comprising an alkoxylated polymeric product having a purity of greater than 92 wt % and the total combined content of high molecular weight products and diols is less than 8 wt % (e.g., less than 2 wt %), as determined by, for example, gel filtration chromatography (GFC) analysis.
  • GFC gel filtration chromatography
  • the alkoxylated polymer product has the following structure:
  • n is an integer from 20 to 1000 (e.g., from 50 to 1000).
  • a method comprising the steps of (i) alkoxylating in a suitable solvent a previously isolated alkoxylatable oligomer to form an alkoxylated polymeric material, wherein the previously isolated alkoxylatable oligomer has a known and defined weight-average molecular weight of greater than 300 Daltons (e.g., greater than 500 Daltons), and (ii) optionally, further activating the alkoxylated polymeric product to provide an activated alkoxylated polymeric product that is useful as (among other things) a polymeric reagent for preparing polymer-drug conjugates.
  • a method comprising the step of activating an alkoxylated polymeric product obtained from and/or contained within a composition comprising an alkoxylated polymeric product having a purity of greater than 90% to thereby form an activated alkoxylated polymeric product that is useful as (among other things) a polymer reagent for preparing polymer-drug conjugates.
  • a method comprising the step of conjugating an activated alkoxylated polymeric product to an active agent, wherein the activated alkoxylated polymeric product was prepared by a method comprising the step of activating an alkoxylated polymeric product obtained from and/or contained within a composition comprising an alkoxylated polymeric product having a purity of greater than 90% to thereby form an activated alkoxylated polymeric product.
  • a mixed salt of a water-soluble polymer-active agent conjugate is provided, the conjugate having been prepared by coupling (under conjugation conditions) an amine-bearing active agent (e.g., a deprotected glycine-irinotecan) to a polymer reagent (e.g., a 4-arm pentaerythritolyl-poly(ethylene glycol)-carboxymethyl succinimide) in the presence of a base to form a conjugate, wherein the conjugate is in the form of a mixed salt conjugate (e.g., the conjugate possesses nitrogen atoms, each one of which will either be protonated or unprotonated, where any given protonated amino group is an acid salt possessing one of two different anions), and further wherein, optionally, the polymer reagent is prepared from an alkoxylation product prepared as described herein.
  • an amine-bearing active agent e.g., a deprotected glycine-
  • FIG. 1 is a graph illustrating the results of stress stability studies on three different samples of 4-arm-PEG-Gly-Irino-20K, each having a different composition with respect to relative amounts of trifluoroacetic acid and hydrochloride salts, as well as free base.
  • Samples tested included >99% HCl salt ( ⁇ 1% free base, triangles), 94% total salt (6% free base, squares), and 52% total salt (48% free base, circles).
  • the samples were stored at 25° C. and 60% relative humidity; the plot illustrates degradation of compound over time, as described in detail in Example 3.
  • FIG. 2 is a graph illustrating the increase in free irinotecan over time in samples of 4-arm-PEG-Gly-Irino-20K stored at 40° C. and 75% relative humidity, each having a different composition with respect to relative amounts of trifluoroacetic acid and hydrochloride salts, as well as free base. Samples tested correspond to product containing >99% HCl salt ( ⁇ 1% free base, squares) and product containing 86% total salts (14% free base, diamonds), as described in Example 3.
  • FIG. 3 is a graph illustrating the increase over time in small PEG species (PEG degradation products) in samples of 4-arm-PEG-Gly-Irinio-20K stored at 40° C.′ and 75% relative humidity, as described in detail in Example 3. Samples tested correspond to product containing >99% HCl salt ( ⁇ 1% free base, squares) and product containing 86% total salts (14% free base, diamonds).
  • FIG. 4 is a compilation of overlays of chromatograms exhibiting release of irinotecan via hydrolysis from mono- (DS-1), di- (DS-2), tri- (DS-3) and tetra-irinotecan substituted (DS-4) 4-arm-PEG-Gly-Irino-20K as described in detail in Example 5.
  • FIG. 5 is a graph illustrating the results of hydrolysis of various species of 4-arm-PEG-Gly-Irino-20K as described above in aqueous buffer at pH 8.4 in the presence of porcine carboxypeptidase B in comparison to hydrolysis kinetics modeling data as described in Example 5.
  • the hydrolysis of all species was assumed to be 1 st order kinetics.
  • the order reaction rate constant for disappearance of DS4 (0.36 hr ⁇ 1 ) was used to generate all curves.
  • FIG. 6 is a graph illustrating the hydrolysis of various species of 4-arm-PEG-Gly-Irino-20K as described above in human plasma in comparison to hydrolysis kinetics modeling data. Details are provided in Example 5.
  • the hydrolysis of all species was assumed to be 1 st order kinetics.
  • the 1 st order reaction rate constant for disappearance of DS 4 (0.26 hr ⁇ 1 ) was used to generate all curves.
  • FIG. 7 is a chromatogram following eel filtration chromatography of a material prepared a described in Example 8.
  • FIG. 8 is a chromatogram following gel filtration chromatography of a material prepared a described in Example 9.
  • a “functional group” is a group that may be used, under normal conditions of organic synthesis, to form a covalent linkage between the entity to which it is attached and another entity, which typically bears a further functional group.
  • the functional group generally includes multiple bond(s) and/or heteroatom(s). Preferred functional groups are described herein.
  • reactive 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).
  • 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 that may be protected include, by way of example, carboxylic acid groups, amino groups, hydroxyl groups, thiol groups, carbonyl groups and the like.
  • 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 in P. J. Kocienski, Protecting Groups , Third Ed., Thieme Chemistry, 2003, and references cited therein.
  • a functional group in “protected form” refers to a functional group bearing a protecting group.
  • the term “functional group” or any synonym thereof is meant to encompass protected forms thereof.
  • PEG poly(ethylene glycol)
  • PEGs for use in the present invention will comprise one of the two following structures: “—(CH 2 CH 2 O) n -” or “—(CH 2 CH 2 O) n-1 CH 2 CH 2 —,” depending upon whether or not the terminal oxygen(s) has been displaced, e.g., during a synthetic transformation.
  • the variable (n) ranges from 3 to about 3000, and the terminal groups and architecture of the overall PEG may vary.
  • a water-soluble polymer may bear one or more “end-capping group,” (in which case it can stated that the water-soluble polymer is “end-capped.”
  • exemplary end-capping groups are generally carbon- and hydrogen-containing groups, typically comprised of 1-20 carbon atoms and an oxygen atom that is covalently bonded to the group.
  • the group is typically alkoxy (e.g., methoxy, ethoxy and benzyloxy) and with respect to the carbon-containing group can optionally be saturated or unsaturated, as well as aryl, heteroaryl, cyclo, heterocyclo, and substituted forms of any of the foregoing.
  • the end-capping group can also comprise a detectable label.
  • a detectable label When the polymer has an end-capping group comprising a detectable label, the amount or location of the polymer and/or the moiety (e.g., active agent) to which the polymer is attached can be determined by using a suitable detector.
  • suitable detector include, without limitation, fluorescers, chemiluminescers, moieties used in enzyme labeling, colorimetric (e.g., dyes), metal ions, radioactive moieties, and the like.
  • Water-soluble in the context of a polymer of the invention or a “water-soluble polymer segment” is any segment or polymer that is at least 35% (by weight), preferably greater than 70% (by weight), and more preferably greater than 95% (by weight) soluble in water at room temperature. Typically, a water-soluble polymer or segment will transmit at least about 75%, more preferably at least about 95% of light, transmitted by the same solution after filtering.
  • activated when used in conjugation with a particular functional group, refers to a reactive functional group that reacts readily with an electrophile or nucleophile on another molecule. This is in contrast to those groups that require strong bases or highly impractical reaction conditions in order to react (i.e., a “nonreactive” or “inert” group).
  • Electrophile refers to an ion or atom or a neutral or ionic collection of atoms having an electrophilic center, i.e., a center that is electron seeking or capable of reacting with a nucleophile.
  • Nucleophile refers to an ion or atom or a neutral or ionic collection of atoms having a nucleophilic center, i.e., a center that is seeking an electrophilic center or capable of reacting with an electrophile.
  • protected or “protecting group” or “protective group” refer to the presence of a moiety (i.e., the protecting group) 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, if any.
  • Protecting groups known in the art can be found in Greene, T. W., et al., PROTECTIVE GROUPS IN ORGANIC SYNTHESIS, 3rd ed., John Wiley & Sons, New York, N.Y. (1999).
  • Molecular mass in the context of a water-soluble polymer such as PEG, refers to the weight average molecular weight of a polymer, typically determined by size exclusion chromatography, light scattering techniques, or intrinsic viscosity determination in an organic solvent like 1,2,4-trichlorobenzene.
  • spacer and “spacer moiety” are used herein to refer to an atom or a collection of atoms optionally used to link interconnecting moieties such as a terminus of a series of monomers and an electrophile.
  • the spacer moieties of the invention may be hydrolytically stable or may include a physiologically hydrolyzable or enzymatically degradable linkage.
  • a “hydrolyzable” 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.
  • Illustrative hydrolytically unstable linkages include carboxylate ester, phosphate ester, anhydrides, acetals, ketals, acyloxyalkyl ether, imines, orthoesters, peptides and oligonucleotides.
  • 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 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 allowing: carbon-carbon bonds (e.g., in aliphatic chains), ethers, amides, urethanes, and the like.
  • 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.
  • Multi-armed in reference to the geometry or overall structure of a polymer refers to polymer having 3 or more polymer-containing “arms” connected to a “core” molecule or structure.
  • a multi-armed polymer may possess 3 polymer arms, 4 polymer arms, 5 polymer arms, 6 polymer arms, 7 polymer arms, 8 polymer arms or more, depending upon its configuration and core structure.
  • One particular type of multi-armed polymer is a highly branched polymer referred to as a dendritic polymer or hyperbranched polymer having an initiator core of at least 3 branches, an interior branching multiplicity or 2 or greater, a generation of 2 or greater, and at least 25 surface groups within a single dendrimer molecule.
  • a dendrimer is considered to possess a structure distinct from that of a multi-armed polymer. That is to say, a multi-armed polymer as referred to herein explicitly excludes dendrimers. Additionally, a multi-armed polymer as provided herein possesses a non-crosslinked core.
  • a “dendrimer” or “hyperbranched polymer” is a globular, size monodisperse polymer in which all bonds emerge radially from a central focal point or core with a regular branching pattern and with repeat units that each contribute a branch point.
  • Dendrimers are typically although not necessarily formed using a nano-scale, multistep fabrication process. Each step results in a new “generation” that has two or more times the complexity of the previous generation. Dendrimers exhibit certain dendritic state properties such as core encapsulation, making them unique from other types of polymers.
  • Branch point refers to a bifurcation point comprising one or more atoms at which a polymer splits or branches from a linear structure into one or more additional polymer arms.
  • a multi-arm polymer may have one branch point or multiple branch points, so long as the branches are not regular repeats resulting in a dendrimer.
  • Alkyl refers to a hydrocarbon chain 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. Exemplary alkyl groups include methyl, ethyl, isopropyl, n-butyl, n-pentyl, 2-methyl-1-butyl, 3-pentyl, 3-methyl-3-pentyl, and the like.
  • “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 and ⁇ -butyl.
  • Cycloalkyl refers to a saturated cyclic hydrocarbon chain, including bridged, fused, or spiro cyclic compounds, preferably made up of 3 to about 12 carbon atoms, more preferably 3 to about 8.
  • Non-interfering substituents are those groups that, when present in a molecule, are typically non-reactive with other functional groups contained within the molecule.
  • substituted refers to a moiety (e.g., an alkyl group) substituted with one or more non-interfering substituents, such as, but not limited to: C 3 -C 8 cycloalkyl, e.g., cyclopropyl, cyclobutyl, and the like; halo, e.g., fluoro, chloro, bromo, and iodo; cyano; alkoxy, lower phenyl; substituted phenyl; and the like.
  • substituents may be in any orientation (i.e., ortho, meta or para).
  • Alkoxy refers to an —O—R group, wherein R is alkyl or substituted alkyl, preferably C 1 -C 20 alkyl (e.g., methoxy, ethoxy, propyloxy, etc.), preferably C 1 -C 7 .
  • alkenyl refers to branched and unbranched hydrocarbon groups of 1 to 15 atoms in length, containing at least one double bond, such as ethenyl (vinyl), 2-propen-1-yl(allyl), isopropenyl, 3-buten-1-yl, and the like.
  • alkynyl refers to branched and unbranched hydrocarbon groups of 2 to 15 atoms in length, containing at least one triple bond, such as ethynyl. 1-propynyl, 3-Butyn-1-yl, 1-octyn-1-yl, and so forth.
  • aryl means an aromatic group having up to 14 carbon atoms.
  • Aryl groups include phenyl, naphthyl, biphenyl, phenanthrecenyl, naphthacenyl, and the like.
  • Substituted phenyl and “substituted aryl” denote a phenyl group and aryl group, respectively, substituted with one, two, three, four, or five (e.g., 1-2,1-3, 1-4, or 1-5 substituents) chosen from halo (F, Cl, Br, I), hydroxyl, cyano, nitro, alkyl (e.g., C 1-6 alkyl), alkoxy (e.g., C 1-6 alkoxy), benzyloxy, carboxy, aryl, and so forth.
  • halo F, Cl, Br, I
  • hydroxyl e.g., C 1-6 alkyl
  • alkoxy e.g., C 1-6 alkoxy
  • benzyloxy carboxy, aryl, and so forth.
  • An inorganic acid is an acid that is absent carbon atoms.
  • examples include hydrohalic acids, nitric acid, sulfuric acid, phosphoric acid and the like.
  • Hydrofluoric acid means a hydrogen halide such as hydrofluoric acid (HF), hydrochloric acid (HCl), hydrobromic acid (HBr), and hydroiodic acid (HI).
  • Organic acid means any organic compound (i.e., having at least one carbon atom) possessing one or more carboxy groups (—COOH). Some specific examples include formic acid, lactic acid, benzoic acid, acetic acid, trifluoroacetic acid, dichloroacetic acid, trichloroacetic acid, mixed chlorofluoroacetic acids, citric acid, oxalic acid, and the like.
  • Active agent includes any agent, drug, compound, and the like which provides some pharmacologic, often beneficial, effect that can be demonstrated in-vivo or in vitro. As used herein, these terms further include any physiologically or pharmacologically active substance that produces a localized or systemic effect in a patient. As used herein, especially in reference to synthetic approaches described herein, a “active agent” is meant to encompass derivatized or linker modified versions thereof, such that upon administration in vivo, the parent “bioactive” molecule is released.
  • “Pharmaceutically acceptable excipient” and “pharmaceutically acceptable carrier” refer to an excipient that can be included in a composition comprising an active agent 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 an active agent present in a pharmaceutical preparation that is needed to provide a desired level of active agent and/or conjugate in the bloodstream or in a target tissue or site in the body. The precise amount will depend upon numerous factors, e.g., the particular active agent, the components and physical characteristics of the pharmaceutical preparation, intended patient population, and patient considerations, and can readily be determined by one skilled in the art, based upon the information provided herein and available in the relevant literature.
  • Multi-functional in the context of a polymer means a polymer having 3 or more functional groups, where the functional groups may be the same or different, and are typically present on the polymer termini. Multi-functional polymers will typically contain from about 3-100 functional groups, or from 3-50 functional groups, or from 3-25 functional groups, or from 3-15 functional groups, or from 3 to 10 functional groups, i.e., contains 3, 4, 5, 6, 7, 8, 9 or 10 functional groups.
  • “Difunctional” and “bifunctional” are used interchangeably herein and mean an entity such as a polymer having two functional groups contained therein, typically at the polymer termini. When the functional groups are the same, the entity is said to be homodifunctional or homobifunctional. When the functional groups are different, the entity is said to be heterodifunctional or heterobifunctional.
  • a basic or acidic reactant described herein includes neutral, charged, and any corresponding salt forms thereof.
  • subject refers to a vertebrate, preferably a mammal.
  • Mammals include, but are not limited to, murines, rodents, simians, humans, farm animals, sport animals and pets. Such subjects are typically suffering from or prone to a condition that can be prevented or treated by administration of a water-soluble polymer-active agent conjugate as described herein.
  • Treatment and “treating” of a particular condition include: (1) preventing such a condition, i.e., causing the condition not to develop, or to occur with less intensity or to a lesser degree in a subject that may be exposed to or predisposed to the condition but does not yet experience or display the condition, and (2) inhibiting the condition, i.e., arresting the development or reversing the condition.
  • a “small molecule” is an organic, inorganic, or organometallic compound typically having a molecular weight of less than about 1000, preferably less than about 800 daltons. Small molecules as referred to herein encompass oligopeptides and other biomolecules having a molecular weight of less than about 1000.
  • a “peptide” is a molecule composed of from about 13 to 50 or so amino acids.
  • An oligopeptide typically contains from about 2 to 12 amino acids.
  • partial mixed salt and “mixed salt” as used herein are used interchangeably, and, in the case of a polymer conjugate (and corresponding compositions comprising a plurality of such polymer conjugates), refer to a conjugates and compositions comprising one or more basic amino (or other basic nitrogen containing) groups, where (i) any given one of the basic amino groups in the conjugate or conjugate composition is either non-protonated or protonated and (ii) with respect to any given protonated basic amino group, the protonted basic amino group will have one of two different counterions.
  • partial mixed salt refers to the feature where not all amino groups in the compound or composition are protonated—hence the composition being a “partial” salt, while “mixed” refers to the feature of multiple counterions).
  • a mixed salt as provided herein encompasses hydrates, solvates, amorphous forms, crystalline forms, polymorphs, isomers, and the like.
  • An amine (or other basic nitrogen) group that is in “free base” form is one where the amine group, i.e., a primary, secondary, or tertiary amine, possesses a free electron pair.
  • the amine is neutral, i.e., is uncharged.
  • an amine group that is in “protonated form” exists as a protonated amine, so that the amino group is positively charged.
  • an amine group that is protonated can also be in the form of an acid addition salt resulting from reaction of the amine with an acid such as an inorganic acid or an organic acid.
  • the “mole percent” of an active agent's amino groups refers to the fraction or percentage of amino groups in an active agent molecule contained in a polymer conjugate that are in one particular form or another, where the total mole percent of amino groups in the conjugate is 100 percent.
  • psi pounds per square inch
  • a water-soluble polymer and active agent conjugate is provided, wherein the conjugate is in the form of a mixed salt.
  • conjugates represent novel solid state forms and are based at least in part on the discovery that, in spite of treatment with base in their formation, conjugates precipitate as mixed salts.
  • conjugates can reliably and reproducibly be produced as a mixed salts—where any given basic nitrogen atom within the conjugate (and within the active agent component of the conjugate) is present in one of a variety of forms.
  • the conjugates provided herein possess active agent basic nitrogen atoms, e.g., amino groups, each one of which will either be protonated or unprotonated, where any given protonated amino group is an acid salt possessing one of two different anions.
  • active agent basic nitrogen atoms e.g., amino groups, each one of which will either be protonated or unprotonated, where any given protonated amino group is an acid salt possessing one of two different anions.
  • the mixed salt form of the conjugate has several unexpected and advantageous characteristics (i.e., greater stability against degradation of the polymer backbone, greater hydrolytic stability, etc.,) when compared to the corresponding free base or single acid salt forms of the conjugate.
  • a method comprising the step of alkoxylating in a suitable solvent a previously isolated alkoxylatable oligomer to form an alkoxylated polymeric product, wherein the previously isolated alkoxylatable oligomer has a known and defined weight-average molecular weight of greater than 300 Daltons (e.g., greater than 500 Daltons).
  • the alkoxylation methods provided herein result in polymeric products that are superior (e.g., in terms of consistency and purity) than polymeric products prepared by previously known methods.
  • a polymer formed by the present alkoxylation methods may advantageously be used to prepare a mixed acid salt as described herein.
  • compositions of Conjugates Prepared from Polymer Reagents Prepared from Polymeric Products Using the Alkoxylation Methods:
  • a mixed salt of a water-soluble polymer-active agent conjugate wherein the conjugate is prepared by coupling (under conjugation conditions) an amine-bearing active agent (e.g., a deprotected glycine-irinotecan) to a polymer reagent (e.g., 4-arm pentaerythritolyl-poly(ethylene glycol)-carboxymethyl succinimide) in the presence of a base to form a conjugate, wherein the conjugate is a mixed salt conjugate (e.g., the conjugate possesses nitrogen atoms, each one of which will either be protonated or unprotonated, where any given protonated amino group is an acid salt possessing one of two different anions), and further wherein, optionally, the polymer reagent is prepared from a alkoxylation product prepared as described herein.
  • an amine-bearing active agent e.g., a deprotected glycine-irinotecan
  • Water-soluble polymer-active agent conjugates include a water-soluble polymer.
  • a water-soluble polymer (again, in the form of a polymer reagent bearing, e.g., an activated ester) can be coupled to an active agent possessing one or more basic amine groups (or other basic nitrogen atoms), i.e., an amine having a pK from about 7.5 to about 11.5 (determined after conjugation).
  • an active agent possessing one or more basic amine groups (or other basic nitrogen atoms), i.e., an amine having a pK from about 7.5 to about 11.5 (determined after conjugation).
  • the water-soluble polymer component of the conjugate is typically a water-soluble and non-peptidic polymer.
  • Representative polymers include poly(alkylene glycol), poly(olefinic alcohol), poly(vinylpyrrolidone), poly(hydroxyalkylmethacrylamide), poly(hydroxyalkylmethacrylate), poly(saccharide), poly( ⁇ -hydroxy acid), poly(acrylic acid), poly(vinyl alcohol), polyphosphazene, polyoxazoline, poly(N-acryloylmorpholine), or copolymers or terpolymers thereof.
  • One particular water-soluble polymer is polyethylene glycol or PEG comprising the repeat unit (CH 2 CH 2 O) n —, where n ranges from about 3 to about 2700 or even greater, or preferably from about 25 to about 1300.
  • the weight average molecular weight of the water-soluble polymer in the partial mixed acid salt ranges from about 100 daltons to about 150,000 daltons.
  • Illustrative overall molecular weights for the conjugate may range from about 800 to about 80,000 daltons, or from about 900 to about 70,000 daltons.
  • Additional representative molecular weight ranges are from about 1,000 to about 40,000 daltons, or from about 5,000 to about 30,000 daltons, or from about 7500 daltons to about 25,000 daltons, or even from about 20,000 to about 80,000 daltons for higher molecular weight embodiments of the instant partial mixed salts.
  • the water-soluble polymer can be in any of a number of geometries or forms, including linear, branched, forked. In exemplary embodiments, the polymer is often linear or multi-armed. Water-soluble polymers can be obtained commercially as simply the water-soluble polymer. In addition, water-soluble polymers can be conveniently obtained in an activated form as a polymer reagent (which optionally may be coupled to an active agent without further modification or activation). Descriptions of water-soluble polymers and polymer reagents can be found in Nektar Advanced PEGylation Catalog, 2005-2006, “Polyethylene Glycol and Derivatives for Advanced PEGylation” and are available for purchase from NOF Corporation and JenKem Technology USA, among others.
  • An exemplary branched polymer having two polymer arms in a branched pattern is the following, often referred to as PEG-2 or mPEG-2:
  • variable corresponds to an integer and represents the number of monomer subunits within the repeating monomeric structure of the polymer.
  • multi-arm water-soluble polymer reagents having for example 3, 4, 5, 6 or 8 polymer arms, each optimally bearing a functional group.
  • a multi-arm polymer reagent may possess any of a number of cores (e.g., a polyol core) from which the polymer arms emanate.
  • Exemplary polyol cores include glycerol, glycerol dimer (3,3′-oxydipropane-1,2-diol) trimethylolpropane, sugars (such as sorbitol or pentaerythritol, pentaerythritol dimer), and glycerol oligomers, such as hexaglycerol or 3-(2-hydroxy-3-(2-hydroxyethoxy)propoxy)propane-1,2-diol, and other glycerol condensation products.
  • the cores and the polymer arms emanating therefrom can be of the following formulae:
  • the water soluble polymer is a 4-arm polymer as shown above, where n may range from about 20 to about 500, or from about 40 to about 500.
  • each polymer arm typically has a molecular weight corresponding to one of the following: 200, 250, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 3000, 4000, 5000, 6000, 7000, 7500, 8000, 9000, 10000, 12,000, 15000, 17,500, 18,000, 19,000, 20,000 Daltons or greater.
  • Overall molecular weights for the multi-armed polymer configurations described herein generally correspond to one of the following: 800, 1000, 1200, 1600, 2000, 2400, 2800, 3200, 3600, 4000, 5000, 6000, 8000, 10,000, 12,000, 15,000, 16,000, 20,000, 24,000, 25,000, 28,000, 30,000, 32,000, 36,000, 40,000, 45,000, 48,000, 50,000, 60,000, 80,000 or 100,000 or greater.
  • the water-soluble polymer e.g., PEG
  • the linker may contain any number of atoms. Generally speaking, the linker has an atom length satisfying one or more of the following ranges: from about 1 atom to about 50 atoms; from about 1 atom to about 25 atoms; from about 3 atoms to about 12 atoms; from about 6 atoms to about 12 atoms; and from about 8 atoms to about 12 atoms.
  • atom chain length only atoms contributing to the overall distance are considered.
  • a linker having the structure, —CH 2 —C(O)—NH—CH 2 CH 2 O—CH 2 CH 2 O—C(O)—O— is considered to have a chain length of 11 atoms, since substituents are not considered to contribute significantly to the length of the linker.
  • Illustrative linkers include bifunctional compounds such as amino acids (e.g., alanine, glycine, isoleucine, leucine, phenylalanine, methionine, serine, cysteine, sarcosine, valine, lysine, and the like).
  • the amino acid may be a naturally-occurring amino acid or a non-naturally occurring amino acid.
  • Suitable linkers also include oligopeptides.
  • each of the PEG arms illustrated above further comprises a carboxy methyl group, —CH 2 —C(O)O—, covalently attached to the terminal oxygen atom.
  • water-soluble polymers that have utility in (for example) preparing conjugates with active agents (as well as salt and mixed salt forms thereof) can be obtained commercially.
  • methods for preparing water-soluble polymers which methods distinguish over previously described methods for preparing water-soluble polymers—are provided that are particularly suited for preparing conjugates with active agents (as well as salt and mixed salt forms thereof).
  • a method comprising the step of alkoxylating in a suitable solvent a previously isolated alkoxylatable oligomer to form an alkoxylated polymeric product, wherein the previously isolated alkoxylatable oligomer has a known and defined weight-average molecular weight of greater than 300 Daltons (e.g., greater than 500 Daltons).
  • the alkoxylating step is carried out using alkoxylation conditions, such that the sequential addition of monomers is effected through repeated reactions of an oxirane compound.
  • the alkoxylatable oligomer initially has one or more hydroxyl functional groups, one or more of these hydroxyl groups in the alkoxylatable oligomer will be converted into a reactive alkoxide by reaction with a strong base.
  • an oxirane compound reacts with an alkoxylatable functional group (e.g., a reactive alkoxide), thereby not only adding to the reactive alkoxide, but doing so in a way that also terminates in another reactive alkoxide.
  • repeated reactions of an oxirane compound at the reactive alkoxide terminus of the previously added and reacted oxirane compound effectively produces a polymer chain.
  • each of the one or more alkoxylatable functional groups is preferably hydroxyl
  • other groups such as amines, thiols and the hydroxyl group of a carboxylic acid can serve as an acceptable alkoxylatable functional group.
  • addition at the alpha carbon atoms of these groups can serve as an acceptable alkoxylatable functional group.
  • the oxirane compound contains an oxirane group and has the following formula:
  • R 1 is selected from the group consisting of H and alkyl (preferably lower alkyl when alkyl);
  • R 2 is selected from the group consisting of H and alkyl (preferably lower alkyl when alkyl);
  • R 3 is selected from the group consisting of H and alkyl (preferably lower alkyl when alkyl);
  • R 4 is selected from the group consisting of H and alkyl (preferably lower alkyl when alkyl).
  • each of R 1 , R 2 , R 3 and R 4 is H, and it is preferred that only one of R 1 , R 2 , R 3 and R 4 is alkyl (e.g., methyl and ethyl) and the remaining substituents are H.
  • exemplary oxirane compounds are ethylene oxide, propylene oxide and 1,2-butylene oxide. The amount of oxirane compound added to result in optimal alkoxylation conditions depends upon a number of factors, including the amount of starting alkoxylatable oligomer, the desired size of the resulting alkoxylated polymeric material and the number of alkoxylatable functional groups on the alkoxylatable oligomer.
  • the alkoxylation conditions include the presence of a strong base.
  • the purpose of the strong base is to deprotonate each acidic hydrogen (e.g., the hydrogen of a hydroxyl group) present in the alkoxylatable oligomer and form an alkoxide ionic species (or an ionic species for non-hydroxyl alkoxylatable functional groups).
  • Preferred strong bases for use as part of the alkoxylation conditions are: alkali metals, such as metallic potassium, metallic sodium, and alkali metals mixtures such as sodium-potassium alloys; hydroxides, such as NaOH and KOH; and alkoxides (e.g., present following addition of an oxirane compound).
  • strong bases can be used and can be identified by one of ordinary skill in the art.
  • a given base can be used as a strong base herein if the strong base can form an alkoxide ionic species (or an ionic species for non-hydroxyl alkoxylatable functional groups) and also provide a cation that does not encumber the alkoxide ionic species so as to hinder (or effectively hinder through an impractically slow) reaction of the alkoxide ionic species with the oxirane molecule.
  • the strong base is present in a generally small and calculated amount, which amount can fall into one or more of the following ranges: from 0.001 to 10.0 weight percent based upon the weight of the total reaction mixture; and from 0.01 to about 6.0 weight percent based upon the weight of the total reaction mixture.
  • the alkoxylation conditions include a temperature suitable for alkoxylation to occur.
  • Exemplary temperatures that may be suitable for alkoxylation to occur include those falling into one or more of the following ranges: from 10° C. to 260° C.; from 20° C. to 240′′ C; from 30° C. to 220° C.; from C to 200° C.; from 50° C. to 200° C.; from 80° C. to 140° C.; and from 100° C. to 120° C.
  • the alkoxylation conditions include a pressure suitable for alkoxylation to occur.
  • Exemplary pressures that may be suitable for alkoxylation to occur include those falling into one or more of the following ranges: from 10 psi to 1000 psi; from 15 psi to 500 psi; from 20 psi to 250 psi; from 25 psi to 100 psi.
  • the alkoxylation pressure can be about atmospheric pressure at sea level (e.g., 14.696 pounds per square inch +/ ⁇ 10%).
  • the alkoxylation conditions include addition of the oxirane compound in liquid form. In some instances, the alkoxylation conditions include addition of the oxirane compound in vapor form.
  • the alkoxylation conditions can include the use of a suitable solvent.
  • a suitable solvent Optimally, the system in which the alkoxylation conditions occur will not include any component (including any solvent) that can be deprotonated (or remains substantially protonated under the conditions of pH, temperature, and so forth under which the alkoxylation conditions will occur).
  • Suitable solvents for alkoxylation include organic solvents selected from the group consisting of, tetrahydrofuran (THF), dimethylformamide (DMF), toluene, benzene, xylenes, mesitylene, tetrachloroethylene, anisole, dimethylacetamide, and mixtures of the foregoing.
  • the alkoxylation conditions when the alkoxylation conditions are conducted in the liquid phase, the alkoxylation conditions are conducted such that both the alkoxylatable oligomer and the desired alkoxylated polymeric material formed from alkoxylating the alkoxylatable oligomer not only have similar solubilities (and, preferably, substantially the same solubility) in the suitable solvent used, but are also both substantially soluble in the suitable solvent.
  • the alkoxylatable oligomer will be substantially soluble in the solvent used in the alkoxylation conditions and the resulting alkoxylated polymeric material also will be substantially soluble in the alkoxylation conditions.
  • this substantially same solubility of the alkoxylated oligomer and the alkoxylated polymeric material in a suitable solvent stands in contrast to the solubility of a precursor molecule (used, for example, in the preparation of the previously isolated alkoxylated oligomer) in the suitable solvent, wherein the precursor molecule can have a lower (and even substantially lower) solubility in the suitable solvent than the alkoxylated oligomer and/or the alkoxylated polymeric material.
  • the alkoxylated oligomer and the alkoxylated polymeric material will both have a pentaerthritol core and will both be substantially soluble in toluene, but pentaerthritol itself has limited solubility in toluene.
  • the solvent employed in the alkoxylation conditions is toluene.
  • the amount of toluene used for the reaction is greater than 25 wt % and less than 75 wt % of the reaction mixture, based on the weight of reaction mixture after complete addition of the oxirane compound.
  • One of ordinary skill in the art can calculate the starting amount of the solvent by taking into account the desired molecular weight of the polymer, the number of sites for which alkoxylation will take place, the weight of the alkoxylatable oligomer used, and so forth.
  • the amount of the toluene is measured so that the amount is sufficient for the alkoxylation conditions providing the desired alkoxylated polymeric material.
  • the alkoxylation conditions have substantially no water present.
  • the alkoxylation conditions have a water content of less than 100 ppm, more preferably 50 ppm, still more preferably 20 ppm, much more preferably less than 14 ppm, and even still more preferably less than 8 ppm.
  • the alkoxylation conditions take place in a suitable reaction vessel, typically a stainless steel reactor vessel.
  • the alkoxylatable oligomer and/or precursor molecule lacks an isocyanate group attached to a carbon bearing an alpha hydrogen is acceptable. In one or more embodiments, the previously prepared alkoxylatable oligomer and/or precursor molecule lacks an isocyanate group.
  • the alkoxylatable oligomer used in the new alkoxylation method must have at least one alkoxylatable functional group.
  • the alkoxylatable oligomer can have one, two, three, four, five, six, seven, eight or more alkoxylatable functional groups, with a preference for an alkoxylatable oligomer having from one to six alkoxylatable functional groups.
  • each alkoxylatable functional group within the alkoxylatable oligomer can be independently selected from the group consisting of hydroxyl, carboxylic acid, amine, thiol, aldehyde, ketone, and nitrile.
  • each alkoxylatable functional group is the same (e.g., each alkoxylatable functional group within the alkoxylatable oligomer is hydroxyl), although instances of different alkoxylatable functional groups within the same alkoxylatable oligomer are contemplated as well.
  • the alkoxylatable functional group is hydroxyl, it is preferred that the hydroxyl is a primary hydroxyl.
  • the alkoxylatable oligomer can take any of a number of possible geometries.
  • the alkoxylatable oligomer can be linear.
  • one terminus of the linear alkoxylatable oligomer is a relatively inert functional group (e.g., an end-capping group) and the other terminus is an alkoxylatable functional group (e.g., hydroxyl).
  • An exemplary alkoxylatable oligomer of this stnicture is methoxy-PEG-OH, or mPEG in brief, in which one terminus is the relatively inert methoxy group, while the other terminus is a hydroxyl group.
  • the structure of mPEG is given below.
  • n is an integer from 13 to 100.
  • alkoxylatable oligomer can take is a linear organic polymer bearing alkoxylatable functional groups (either the same or different) at each terminus.
  • alkoxylatable oligomer of this structure is alpha-, omega-dihydroxylpoly(ethylene glycol), or
  • n is an integer from 13 to 100
  • HO-PEG-OH where it is understood that the —PEG-symbol represents the following structural unit:
  • n is an integer from 13 to 100
  • alkoxylatable oligomer may have a “multi-armed” or branched structure.
  • one or more atoms in the alkoxylatable oligomer serves as a “branching point atom,” through which two, three, four or more (hut typically two, three or four) distinct sets of repeating monomers or “arms” are connected (either directly or through one or more atoms).
  • a “multi-arm” structure as used herein has three or more distinct arms, but can have as many as four, five, six, seven, eight, nine, or more arms, with 4- to 8-arm multi-arm structures preferred (such as a 4-arm structure, a 5-arm structure, a 6-arm structure, and an 8-arm structure).
  • n is from 1 to 50, e.g., from 10 to 50, (or otherwise defined such that the molecular weight of the structure is from 300 Daltons to 9,000 Daltons (e.g., from about 500 Daltons to 5,000 Daltons);
  • n is from 2 to 50, e.g., from 10 to 50 (or otherwise defined such that the molecular weight of the structure is from 300 Daltons to 9,000 Daltons (e.g., from about 500 Daltons to 5,000 Daltons);
  • n is from 2 to 35, e.g., from 8 to about 40 (or otherwise defined such that the molecular weight of the structure is from 750 Daltons to 9,500 Daltons (e.g., from 500 Daltons to 5,000 Daltons);
  • n 2 to 35, e.g., from 5 to 35, (or otherwise defined such that the molecular weight of the structure is from 1,000 Daltons to 13,000 Daltons (e.g., from 500 Daltons to 5,000 Daltons).
  • n is substantially the same.
  • all values of n for that alkoxylatable oligomer are within three standard deviations, more preferably within two standard deviations, and still more preferably within one standard deviation.
  • the alkoxylatable oligomer will have a known and defined weight-average molecular weight.
  • a weight-average molecular weight can only be known and defined for an alkoxylatable oligomer when the alkoxylatable oligomer is isolated from the synthetic milieu from which it was generated.
  • Exemplary weight-average molecular weights for the alkoxylatable oligomer will fall into one or more of the following ranges: greater than 300 Daltons; greater than 500 Daltons; from 300 Daltons to 15,000 Daltons; from 500 Daltons to 5,000 Daltons; from 300 Daltons to 10,000 Daltons; from 500 Daltons to 4,000 Daltons; from Daltons to 5,000 Daltons; from 500 Daltons to 3,000 Daltons; from 300 Daltons to 2,000 Daltons; from 500 Daltons to 2,000 Daltons; from 300 Daltons to 1,000 Daltons; from 500 Daltons to 1,000 Daltons; from 1,000 Daltons to 10,000 Daltons; from 1,000 Daltons to 5,000 Daltons; from 1,000 Daltons to 4,000 Daltons; from 1,000 Daltons to 3,000 Daltons; from 1,000 Daltons to 2,000 Daltons; from 1,500 Daltons to 15,000 Daltons; from 1,500 Daltons to 5,000 Daltons; from 1,500 Daltons to 10,000 Daltons; from 1,500 Daltons to 4,000 Daltons; from 1,500 Daltons to 3,000 Daltons; from 1,500 Daltons to 2,000 Daltons
  • the alkoxylatable oligomer is preferably previously isolated.
  • previously isolated is meant the alkoxylatable oligomer exists outside and separate from the synthetic milieu from which it was generated (most typically outside of the alkoxylating conditions used to prepare the alkoxylatable oligomer) and can optionally be stored for a relatively long period of time or optionally stored over a shorter time without substantially changing for subsequent use.
  • an alkoxylatable oligomer is previously isolated if, for example, it is housed in an inert environment.
  • a previously isolated alkoxylated oligomer can be housed in a container substantially lacking (e.g., less than 0.1 wt %) an oxirane compound.
  • a previously isolated alkoxylatable oligomer does not change its molecular weight more than 10% over the course of 15 days.
  • the concept of “previously isolated” stands in contrast to (for example) a situation where an ongoing and uninterrupted alkoxylation reaction is allowed to proceed from precursor molecule, into a structure that corresponds an alkoxylatable oligomer, to a structure that corresponds to an alkoxylated polymeric material; the concept of “previously isolated” requires that the alkoxylatable oligomer exists apart from the conditions from which it formed. Pursuant to the present invention, however, the previously isolated alkoxylatable oligomer will be subjected to an alkoxylation step once it is added to, as a separate step, alkoxylation conditions.
  • the alkoxylatable oligomer can be obtained via synthetic means.
  • the alkoxylatable oligomer is prepared by (a) alkoxylating a precursor molecule having a molecular weight of less than 300 Daltons (e.g., less than 500 Daltons) to form a reaction mixture comprising an alkoxylatable oligomer or prepolymer, and (b) isolating the alkoxylatable oligomer from the reaction mixture.
  • the step of alkoxylating the precursor molecule largely follows the conditions and requirements of the alkoxylating step previously discussed.
  • the step of isolating the alkoxylatable oligomer can be carried out using any art known step, but can include allowing all oxirane compound to be consumed in the reaction, actively performing a quenching step, separating the final reaction mixture through art-known approaches (including, for example, distilling off all volatile materials, removing solid reaction by-product by filtration or washing and applying chromatographic means).
  • the alkoxylatable oligomer can be obtained from commercial sources.
  • Exemplary commercial sources include NOF Corporation (Tokyo Japan) which provides alkoxylatable oligomers under the names SUNBRIGHT DKH® polyethylene glycol), SUNBRIGHT® GL glycerine, tri-poly(ethylene glycol) ether, SUNBRIGHT PTE® pentaerythritol, tetra-poly(ethylene glycol) ether, SUNBRIGHT® DG di-glycerine, tetra-poly(ethylene glycol) ether, and SUNBRIGHT HGEO® hexa-glycerine, octa-poly(ethylene glycol) ether.
  • Preferred alkoxylatable oligomers include those having the structures of SUNBRIGHT PTE®-2000 pentaerythritol, tetra-polyethylene glycol) ether (which has a weight-average molecular weight of about 2,000 Daltons) and SUNBRIGHT® DG-2000 di-glycerine, tetra-poly(ethylene glycol) ether (which has a weight-average molecular weight of about 2,000 Daltons).
  • Precursor molecules can be any small molecule (e.g., a molecular weight less than the weight-average molecular weight of the alkoxylatable oligomer) having one or more alkoxylatable functional groups.
  • Exemplary precursor molecules include polyols, which are small molecules (typically of a molecular weight of less than 300 Daltons, e.g., less than 500 Daltons) having a plurality of available hydroxyl groups.
  • the polyol serving as the precursor molecule will typically comprise 3 to about 25 hydroxyl groups, preferably about 3 to about 22 hydroxyl groups, most preferably about 4 to about 12 hydroxyl groups.
  • Preferred polyols include glycerol oligomers or polymers such as hexaglycerol, pentaerythritol and oligomers or polymers thereof (e.g., dipentaerythritol, tripentaerythritol, tetrapentaerythritol, and ethoxylated forms of pentaerythritol), and sugar-derived alcohols such as sorbitol, arabanitol, and mannitol. Also, many commercially available polyols, such as various isomers of inositol (i.e.
  • Exemplary preferred precursor molecules include those precursor molecules selected from the group consisting of glycerol, diglycerol, triglycerol, hexaglycerol, mannitol, sorbitol, pentaerythritol, dipentaerthitol, and tripentaerythritol.
  • neither the previously isolated alkoxylatable oligomer nor the alkoxylated polymeric product has an alkoxylatable functional group (e.g., hydroxyl group) of the precursor molecule.
  • the alkoxylated polymeric material prepared under the methods described herein will have a basic architecture corresponding to the structure of the alkoxylatable oligomer (i.e., a linear alkoxylatable oligomer results in a linear alkoxylated polymericmaterial, a four-armed alkoxylatable oligomer results in a four-armed alkoxylated polymer material, so forth).
  • the alkoxylated polymeric material will take any of a number of possible geometries, including linear, branched and multi-armed.
  • a branched alkoxylated polymeric material will have three or more distinct arms, but can have as many as four, five, six, seven, eight, nine, or more arms, with 4- to 8-arm branched structures preferred (such as a 4-arm branched structure, 5-arm branched structure, 6-arm branched structure, and 8-arm branched structure).
  • n satisfies one or more of the following ranges: from 10 to 1,000; from 10 to 500; from 10 to 250; from 50 to 1000; from 50 to 250; and from 50 to 120 (or otherwise defined such that the molecular weight of the structure is from 2,000 Daltons to 180,000 Daltons, e.g., from 2,000 Daltons to 120,000 Daltons);
  • n satisfies one or more of the following ranges: from 10 to 1,000; from 10 to 500; from 10 to 250; from 50 to 1,000; from 50 to 250; and from 50 to 120 (or otherwise defined such that the molecular weight of the structure is from 2,000 Daltons to 180,000 Daltons, e.g., from 2,000 Daltons to 120,000 Daltons);
  • n is satisfies one or more of the following ranges: from 10 to 750; from 40 to 750; from 50 to 250; and from 50 to 120 (or otherwise defined such that the molecular weight of the structure is from 3,000 Daltons to 200,000 Daltons, e.g., from 12,000 Daltons to 200,000 Daltons); and
  • n is satisfies one or more of the following ranges: from 10 to 600 and from 35 to 600 (or otherwise defined such that the molecular weight of the structure is from 4,000 Daltons to 215,000 Daltons, e.g., from 12,000 Daltons to 215,000 Daltons).
  • n is substantially the same.
  • all values of n for that alkoxylated polymeric material alkoxylatable oligomer or prepolymer are within three standard deviations, more preferably within two standard deviations, and still more preferably within one standard deviation.
  • the alkoxylated polymeric material will have a known and defined number-average molecular weight.
  • a number-average molecular weight can only be known and defined for material that is isolated from the synthetic milieu from which it was generated.
  • the total molecular weight of the alkoxylated polymeric product can be a molecular weight suited for the intended purpose. An acceptable molecular weight for any given purpose can be determined through trial and error via routine experimentation. Exemplary molecular weights for the alkoxylated polymeric product, will have a number-average molecular weight falling within one or more of the following ranges: from 2,000 Daltons to 215,000 Daltons; from 5,000 Daltons to 215,000 Daltons; from 5,000 Daltons to 150,000 Daltons; from 5,000 Daltons to 100,000 Daltons; from 5,000 Daltons to 80,000 Daltons; from 6,000 Daltons to 80,000 Daltons; from 7,500 Daltons to 80,000 Daltons; from 9,000 Daltons to 80,000 Daltons; from 10,000 Daltons to 80,000 Daltons; from 12,000 Daltons to 80,000 Daltons; from 15,000 Daltons to 80,000 Daltons; from 20,000 Daltons to 80,000 Daltons; from 25,000 Daltons to 80,000 Daltons; from 30,000 Daltons to 80,000 Daltons; from 40,000 Daltons to 80,000 Dal
  • an optional step can be carried out so as to further transform the alkoxylated polymeric material so that it bears a specific reactive group to form a polymeric reagent.
  • the alkoxylated polymeric material can be functionalized to include a reactive group (e.g., carboxylic acid, active ester, amine, thiol, maleimide, aldehyde, ketone, and so forth).
  • an optional step is carried out in a suitable solvent.
  • a suitable solvent One of ordinary skill in the art can determine whether any specific solvent is appropriate for any given reaction step.
  • the solvent is preferably a nonpolar solvent or a polar solvent.
  • nonpolar solvents include benzene, xylenes and toluene.
  • Exemplary polar solvents include, but are not limited to, dioxane, tetrahydrofuran (THF), t-butyl alcohol, DMSO (dimethyl sulfoxide), HMPA (hexamethylphosphoramide), DMF (dimethylformamide), DMA (dimethylacetamide), and NMP(N-methylpyrrolidinone).
  • compositions comprising the alkoxylated polymeric material which include not only any compositions comprising the alkoxylated polymeric material, but also compositions in which the alkoxylated polymeric material is further transformed into, for example, a polymer reagent, as well as compositions of conjugates formed from coupling such polymer reagents with an active agent.
  • a benefit of the method described herein is the ability to achieve high purity alkoxylated polymeric material-containing compositions.
  • compositions can be characterized as having: substantially low content of both high molecular weight impurities (e.g., polymer-containing species having a molecular weight greater than the molecular weight of the desired alkoxylated polymeric material) and low content of low molecular weight diol impurities (i.e., HO-PEG-OH), either impurity type (and preferably both impurity types) totaling less than 8 wt %, and more preferably less than 2 wt %.
  • high molecular weight impurities e.g., polymer-containing species having a molecular weight greater than the molecular weight of the desired alkoxylated polymeric material
  • low content of low molecular weight diol impurities i.e., HO-PEG-OH
  • impurity type and preferably both impurity types
  • compositions can also be characterized as having a purity of alkoxylated polymeric material (as well as compositions comprising polymer reagents formed from the alkoxylated polymeric material, and compositions of conjugates formed from conjugating such polymer reagents and an active agent) of greater than 92 wt %, of greater than 93 wt %, or greater than 94 wt %, of greater than 95 wt %, preferably of greater than 96 wt %, and more preferably greater than 97 wt %.
  • GPC gel permeation chromatography
  • GFC gel filtration chromatography
  • the alkoxylated polymeric material provided herein as well as those alkoxylated polymeric products that have been further modified to bear a specific reactive group are useful for conjugation to, for example, active agents.
  • Preferred groups of the biologically active agents suited for reaction with the polymeric reagents described herein are electrophilic and nucleophilic groups. Exemplary groups include primary amines, carboxylic acids, alcohols, thiols, hydrazines and hydrazides. Such groups suited to react with the polymeric reagents described herein are known to those of ordinary skill in the art.
  • the invention provides a method for making a conjugate comprising the step of contacting, under conjugation conditions, an active agent with a polymeric reagent described herein.
  • Suitable conjugation conditions are those conditions of time, temperature, pH, reagent concentration, reagent functional group(s), available functional groups on the active agent, solvent, and the like sufficient to effect conjugation between a polymeric reagent and an active agent.
  • the specific conditions depend upon, among other things, the active agent, the type of conjugation desired, the presence of other materials in the reaction mixture, and so forth. Sufficient conditions for effecting conjugation in any particular case can be determined by one of ordinary skill in the art upon a reading of the disclosure herein, reference to the relevant literature, and/or through routine experimentation.
  • the polymeric reagent contains an N-hydroxysuccinimide active ester (e.g., succinimidyl succinate, succinimidyl propionate, and succinimidyl butanoate), and the active agent contains an amine group
  • conjugation can be effected at a pH of from about 7.5 to about 9.5 at room temperature.
  • the polymer reagent contains a vinylsulfone reactive group or a maleimide group and the pharmacologically active agent contains a sulfhydryl group
  • conjugation can be effected at a pH of from about 7 to about 8.5 at room temperature.
  • conjugation can be effected by reductive amination wherein the primary amine of the pharmacologically active agent reacts with the aldehyde or ketone of the polymer.
  • reductive amination initially results in a conjugate wherein the pharmacologically active agent and polymer are linked via an imine bond.
  • a suitable reducing agent such as NaCNBH 3 reduces the imine to a secondary amine.
  • Exemplary conjugation conditions include carrying out the conjugation reaction at a pH of from about 4 to about 10, and at, for example, a pH of about 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, or 10.0.
  • the reaction is allowed to proceed from about 5 minutes to about 72 hours, preferably from about 30 minutes to about 48 hours, and more preferably from about 4 hours to about 24 hours.
  • the temperature under which conjugation can take place is typically, although not necessarily, in the range of from about 0° C. to about 40° C., and is often at room temperature or less.
  • the conjugation reactions are often carried out using a phosphate buffer solution, sodium acetate, or similar system.
  • an excess of the polymer reagent is typically combined with the active agent.
  • stoichiometic amounts of reactive groups on the polymer reagent to the reactive groups of the active agent are typically combined with four moles of active agent.
  • Exemplary ratios of reactive groups of polymer reagent to active agent include molar ratios of about 1:1 (reactive group of polymer reagent:active agent), 1:0.1, 1:0.5, 1:1.5, 1:2, 1:3, 1:4, 1:5, 1:6, 1:8, or 1:10.
  • the conjugation reaction is allowed to proceed until substantially no further conjugation occurs, which can generally be determined by monitoring the progress of the reaction over time.
  • reaction can be monitored by withdrawing aliquots from the reaction mixture at various time points and analyzing the reaction mixture by chromatographic methods. SDS-PAGE or MALDI-TOF mass spectrometry. NMR, IR, or any other suitable analytical method. Once a plateau is reached with respect to the amount of conjugate formed or the amount of unconjugated polymer reagent remaining, the reaction is assumed to be complete. Typically, the conjugation reaction takes anywhere from minutes to several hours (e.g., from 5 minutes to 24 hours or more).
  • the resulting product mixture is preferably, but not necessarily purified, to separate out excess active agent, strong base, condensing agents and reaction by-products and solvents.
  • the resulting conjugates can then be further characterized using analytical methods such as chromatographic methods, spectroscopic methods, MALDI, capillary electrophoresis, and/or gel electrophoresis.
  • analytical methods such as chromatographic methods, spectroscopic methods, MALDI, capillary electrophoresis, and/or gel electrophoresis.
  • the polymer-active agent conjugates can be purified to obtain/isolate different conjugated species.
  • exemplary active agents can be an active agent selected from the group consisting of a small molecule drug, an oligopeptide, a peptide, and a protein.
  • the active agent for use herein can include but are not limited to the following: adriamycin, ⁇ -aminobutyric acid (GABA), amiodarone, amitryptyline, azithrornycin, benzphetamine, bromopheniramine, cabinoxamine, calcitonin chlorambucil, chloroprocaine, chloroquine, chlorpheniramine, chlorpromazine, cinnarizine, clarthromycin, clomiphene, cyclobenzaprine, cyclopentolate, cyclophosphamide, dacarbazine, daunomycin, demeclocycline, dibucaine, dicyclomine, diethylproprion, diltiazem, dimenhydrinate, diphenhydramine, disopyramide, doxepin, doxycycline, doxylamine, dypyridame, EDTA, erythromycin, flurazepam,
  • active agents include those selected from the group consisting of acravistine, amoxapine, astemizole, atropine, azithromycin, benzapril, benztropine, beperiden, bupracaine, buprenorphine, buspirone, butorphanol, caffeine, camptothecin and molecules belonging to the camptothecin family, ceftriaxone, chlorpromazine, ciprofloxacin, cladarabine, clindastine, clindamycin, clofazamine, clozapine, cocaine, codeine, cyproheptadine, desipramine, dihydroergotamine, diphenidol, diphenoxylate, dipyridamole, docetaxel, doxapram, ergotamine, famciclovir, fentanyl, flavoxate, fludarabine, fluphenazine, fluvastin, ganciclovir, granisteron
  • Still further exemplary active agents include those selected from the group consisting of acetazolamide, acravistine, acyclovir, adenosine phosphate, allopurinal, alprazolam, amoxapine, aminone, apraclonidine, azatadine, aztreonam, bisacodyl, bleomycin, bromopheniramine, buspirone, butoconazole, camptothecin and molecules within the camptothecin family, carbinoxamine, cefamandole, cefazole, cefixime, cefmetazole, cefonicid, cefoperazone, cefotaxime, cefotetan, cefpodoxime, ceftriaxone, cephapirin, chloroquine, chlorpheniramine, cimetidine, cladarabine, clotrimazole, cloxacillin, didanosine, dipyridamole, doxazos
  • active agents include those belonging to the camptothecin family of molecules.
  • the active agent can possess the general structure:
  • R 1 , R 2 , R 3 , R 4 and R 5 are each independently selected from the group consisting of: hydrogen; halo; acyl; alkyl (e.g., C1-C6 alkyl); substituted alkyl; alkoxy (e.g., C1-C6 alkoxy); substituted alkoxy; alkenyl; alkynyl; cycloalkyl; hydroxyl; cyano; nitro; azido; amino; hydrazine; amino; substituted amino (e.g., monoalkylamino and dialkylamino); hydroxcarbonyl; alkoxycarbonyl; alkylcarbonyloxy; alkylcarbonylamino; carbamoyloxy; arylsulfonyloxy; alkylsulfonyloxy; —C(R 7 ) ⁇ N—(O) i —R 8 wherein R 7 is H, alkyl, alkenyl, cycloalkyl,
  • An exemplary active agent is irinotecan.
  • Another exemplary active agent is 7-ethyl-10-hydroxy-camptothecin (SN-38), the structure of which is shown below.
  • exemplary class of active agents include those belonging to the taxane family of molecules.
  • An exemplary active agent from this class of molecules is docetaxel where the H of the hydroxy at the 2′ hydroxyl group is involved in forming the preferred multi-armed polymer conjugate:
  • the polymer reagents described herein can be attached, either covalently or noncovalently, to a number of entities including films, chemical separation and purification surfaces, solid supports, metal surfaces such as gold, titanium, tantalum, niobium, aluminum, steel, and their oxides, silicon oxide, macromolecules (e.g., proteins, polypeptides, and so forth), and small molecules. Additionally, the polymer reagents can also be used in biochemical sensors, bioelectronic switches, and gates.
  • the polymer reagents can also be employed as carriers for peptide synthesis, for the preparation of polymer-coated surfaces and polymer grafts, to prepare polymer-ligand conjugates for affinity partitioning, to prepare cross-linked or non-cross-linked hydrogels, and to prepare polymer-cofactor adducts for bioreactors.
  • the conjugate can be provided as a pharmaceutical composition for veterinary and for human medical use.
  • a pharmaceutical compositions is prepared by combining the conjugate with one or more pharmaceutically acceptable excipients, and optionally any other therapeutic ingredients.
  • Exemplary pharmaceutically acceptable excipients without limitation, those selected from the group consisting of carbohydrates, inorganic salts, antimicrobial agents, antioxidants, surfactants, buffers, acids, bases, and combinations thereof.
  • a carbohydrate such as a sugar, a derivatized sugar such as an alditol, aldonic acid, an esterified sugar, and/or a sugar polymer may be present as an excipient.
  • Specific carbohydrate excipients include, for example: monosaccharides, such as fructose, maltose, galactose, glucose, D-mannose, sorbose, and the like; disaccharides, such as lactose, sucrose, trehalose, cellobiose, and the like; polysaccharides, such as raffinose, melezitose, maltodextrins, dextrans, starches, and the like; and alditols, such as mannitol, xylitol, maltitol, lactitol, xylitol, sorbitol (glucitol), pyranosyl sorbitol, myoinositol, and
  • the excipient can also include an inorganic salt or buffer such as citric acid, sodium chloride, potassium chloride, sodium sulfate, potassium nitrate, sodium phosphate monobasic, sodium phosphate dibasic, and combinations thereof.
  • an inorganic salt or buffer such as citric acid, sodium chloride, potassium chloride, sodium sulfate, potassium nitrate, sodium phosphate monobasic, sodium phosphate dibasic, and combinations thereof.
  • the composition can also include an antimicrobial agent for preventing or deterring microbial growth.
  • antimicrobial agents suitable for one or more embodiments of the present invention include benzalkonium chloride, benzethonium chloride, benzyl alcohol, cetylpyridinium chloride, chlorobutanol, phenol, phenylethyl alcohol, phenylmercuric nitrate, thimersol, and combinations thereof.
  • An antioxidant can be present in the composition as well. Antioxidants are used to prevent oxidation, thereby preventing the deterioration of the conjugate or other components of the preparation. Suitable antioxidants for use in one or more embodiments of the present invention include, for example, ascorbyl palmitate, butylated hydroxyanisole, butylated hydroxytoluene, hypophosphorous acid, monothioglycerol, propyl gallate, sodium bisulfate, sodium formaldehyde sulfoxylate, sodium metabisulfite, and combinations thereof.
  • a surfactant can be present as an excipient.
  • exemplary surfactants include: polysorbates, such as “Tween 20” and “Tween 80,” and pluronics such as F68 and F88 (both of which are available from BASF, Mount Olive, N.J.); sorbitan esters; lipids, such as phospholipids such as lecithin and other phosphatidylcholines, phosphatidylethanolamines (although preferably not in liposomal form), fatty acids and fatty esters; steroids, such as cholesterol; and chelating agents, such as EDTA, zinc and other such suitable cations.
  • Acids or bases can be present as an excipient in the composition.
  • acids that can be used include those acids selected from the group consisting of hydrochloric acid, acetic acid, phosphoric acid, citric acid, malic acid, lactic acid, formic acid, trichloroacetic acid, nitric acid, perchloric acid, phosphoric acid, sulfuric acid, fumaric acid, and combinations thereof.
  • Suitable bases include, without limitation, bases selected from the group consisting of sodium hydroxide, sodium acetate, ammonium hydroxide, potassium hydroxide, ammonium acetate, potassium acetate, sodium phosphate, potassium phosphate, sodium citrate, sodium formate, sodium sulfate, potassium sulfate, potassium fumerate, and combinations thereof.
  • the amount of the conjugate (i.e., the conjugate formed between the active agent and the polymeric reagent) in the composition will vary depending on a number of actors, but will optimally be a therapeutically effective dose when the composition is stored in a unit dose container (e.g., a vial).
  • a unit dose container e.g., a vial
  • the pharmaceutical preparation can be housed in a syringe.
  • a therapeutically effective dose can be determined experimentally by repeated administration of increasing amounts of the conjugate in order to determine which amount produces a clinically desired endpoint.
  • the amount of any individual excipient in the composition will vary depending on the activity of the excipient and particular needs of the composition.
  • the optimal amount of any individual excipient is determined through routine experimentation, i.e., by preparing compositions containing varying amounts of the excipient (ranging from low to high), examining the stability and other parameters, and then determining the range at which optimal performance is attained with no significant adverse effects.
  • the excipient will be present in the composition in an amount of about 1% to about 99% by weight, preferably from about 5% to about 98% by weight, more preferably from about 15 to about 95% by weight of the excipient, with concentrations less than 30% by weight most preferred.
  • compositions encompass all types of formulations and in particular those that are suited for injection, e.g., powders or lyophilates that can be reconstituted as well as liquids.
  • suitable diluents for reconstituting solid compositions prior to injection include bacteriostatic water for injection, dextrose 5% in water, phosphate-buffered saline, Ringer's solution, saline, sterile water, deionized water, and combinations thereof.
  • suitable diluents for reconstituting solid compositions prior to injection include bacteriostatic water for injection, dextrose 5% in water, phosphate-buffered saline, Ringer's solution, saline, sterile water, deionized water, and combinations thereof.
  • solutions and suspensions are envisioned.
  • compositions of one or more embodiments of the present invention are typically, although not necessarily, administered via injection and are therefore generally liquid solutions or suspensions immediately prior to administration.
  • the pharmaceutical preparation can also take other forms such as syrups, creams, ointments, tablets, powders, and the like.
  • Other modes of administration are also included, such as pulmonary, rectal, transdermal, transmucosal, oral, intrathecal, subcutaneous, intra-arterial, and so forth.
  • the invention also provides a method for administering a conjugate as provided herein to a patient suffering from a condition that is responsive to treatment with conjugate.
  • the method comprises administering to a patient, generally via injection, a therapeutically effective amount of the conjugate (preferably provided as part of a pharmaceutical composition).
  • the conjugates can be administered injected parenterally by intravenous injection.
  • suitable formulation types for parenteral administration include ready-for-injection solutions, dry powders for combination with a solvent prior to use, suspensions ready for injection, dry insoluble compositions for combination with a vehicle prior to use, and emulsions and liquid concentrates for dilution prior to administration, among others.
  • the method of administering may be used to treat any condition that can be remedied or prevented by administration of the conjugate.
  • the conjugate can be administered to the patient prior to, simultaneously with, or after administration of another active agent.
  • the actual dose to be administered will vary depending upon the age, weight, and general condition of the subject as well as the severity of the condition being treated, the judgment of the health care professional, and conjugate being administered.
  • Therapeutically effective amounts are known to those skilled in the art and/or are described in the pertinent reference texts and literature. Generally, a therapeutically effective amount will range from about 0.001 mg to 100 mg, preferably in doses from 0.01 mg/day to 75 mg/day, and more preferably in doses from 0.10 mg/day to 50 mg/clay.
  • a given dose can be periodically administered up until, for example, related symptoms lessen and/or are eliminated entirely.
  • the unit dosage of any given conjugate (again, preferably provided as part of a pharmaceutical preparation) can be administered in a variety of dosing schedules depending on the judgment of the clinician, needs of the patient, and so forth.
  • the specific dosing schedule will be known by those of ordinary skill in the art or can be determined experimentally using routine methods.
  • Exemplary dosing schedules include, without limitation, administration once daily, three times weekly, twice weekly, once weekly, twice monthly, once monthly, and any combination thereof. Once the clinical endpoint has been achieved, dosing of the composition is halted.
  • One advantage of administering certain conjugates described herein is that individual water-soluble polymer portions can be cleaved when a hydrolytically degradeable linkage is included between the residue of the active agent moiety and water-soluble polymer. Such a result is advantageous when clearance from the body is potentially a problem because of the polymer size. Optimally, cleavage of each water-soluble polymer portion is facilitated through the use of physiologically cleavable and/or enzymatically degradable linkages such as amide, carbonate or ester-containing linkages. In this way, clearance of the conjugate (via cleavage of individual water-soluble polymer portions) can be modulated by selecting the polymer molecular size and the type functional group that would provide the desired clearance properties.
  • One of ordinary skill in the art can determine the proper molecular size of the polymer as well as the cleavable functional group. For example, one of ordinary skill in the art, using routine experimentation, can determine a proper molecular size and cleavable functional group by first preparing a variety of polymer derivatives with different polymer weights and cleavable functional groups, and then obtaining the clearance profile (e.g., through periodic blood or urine sampling) by administering the polymer derivative to a patient and taking periodic blood and/or urine sampling. Once a series of clearance profiles have been obtained for each tested conjugate, a suitable conjugate can be identified.
  • the clearance profile e.g., through periodic blood or urine sampling
  • water-soluble polymer conjugates and compositions containing these conjugates may be provided as mixed salts.
  • the active agent is a small molecule drug, an oligopeptide, a peptide, or a protein, that, when conjugated to the water-soluble polymer, contains at least one basic nitrogen atom such as an amine group (e.g., an amine or other basic nitrogen containing group that is not conjugated to the water-soluble polymer).
  • the basic nitrogen atoms are each individually either protonated or unprotonated, where the protonated nitrogen atoms exist as acid salts of two different anions.
  • Active agents containing at least one amine group or basic nitrogen atom suitable for providing a mixed acid salt as described herein include but are not limited to the following: adriamycin, y-aminobutyric acid (GABA), amiodarone, amitryptyline, azithromycin, benzphetamine, bromopheniramine, cabinoxamine, calcitonin chlorambucil, chloroprocaine, chloroquine, chlorpheniramine, chlorpromazine, cinnarizine, clarthromycin, clomiphene, cyclobenzaprine, cyclopentolate, cyclophosphamide, dacarbazine, daunomycin, demeclocycline, dibucaine, dicyclomine, diethylproprion, diltiazem, dimenhydrinate, diphenhydramine, disopyramide, doxepin, doxycycline, doxylamine, dypyridame,
  • Additional active agents include those comprising one or more nitrogen-containing heterocycles such as acravistine, amoxapine, astemizole, atropine, azithromycin, benzapril, benztropine, beperiden, bupracaine, buprenorphine, buspirone, butorphanol, caffeine, camptothecin and molecules belonging to the camptothecin family, ceftriaxone, chlorpromazine, ciprofloxacin, cladarabine, clemastine, clindamycin, clofazamine, clozapine, cocaine, codeine, cyproheptadine, desipramine, dihydroergotamine, diphenidol, diphenoxylate, dipyridamole, doxapram, ergotamine, famciclovir, fentanyl, flavoxate, fludarabine, fluphenazine, fluvastin, ganciclovir, granisteron,
  • Additional active agents include those comprising an aromatic ring nitrogen such as acetazolamide, acravistine, acyclovir, adenosine phosphate, allopurinal, alprazolam, amoxapine, aminone, apraclonidine, azatadine, aztreonam, bisacodyl, bleomycin, bromopheniramine, buspirone, butoconazole, camptothecin and molecules within the camptothecin family, carbinoxamine, cefamandole, cefazole, cefixime, cefmetazole, cefonicid, cefoperazone, cefotaxime, cefotetan, cefpodoxime, ceftriaxone, cephapirin, chloroquine, chlorpheniramine, cimetidine, cladarabine, clotrimazole, cloxacillin, didanosine, dipyridamole, doxazosin
  • a preferred active agent is one belonging to the camptothecin family of molecules.
  • the active agent may possess the general structure:
  • R 1 -R 5 are each independently selected from the group consisting of hydrogen; halo; acyl; alkyl (e.g., C1-C6 alkyl); substituted alkyl; alkoxy (e.g., C1-C6 alkoxy); substituted alkoxy; alkenyl; alkynyl; cycloalkyl; hydroxyl; cyano; nitro; azido; amido; hydrazine; amino; substituted amino (e.g., monoalkylamino and dialkylamino); hydroxcarbonyl; alkoxycarbonyl; alkylcarbonyloxy; alkylcarbonylamino; carbamoyloxy; arylsulfonyloxy; alkylsulfonyloxy; —C(R 7 ) ⁇ N—(O) i —R 8 wherein R 7 is H, alkyl, alkenyl, cycloalkyl, or aryl, i is 0 or
  • the active agent is irinotecan (structure shown below).
  • the active agent is 7-ethyl-10-hydroxy-camptothecin (SN-38), a metabolite of irinotecan, whose structure is shown below.
  • Illustrative mixed salt conjugates of a water-soluble polymer and an active agent may possess any of a number of structural features as described above. That is to say, the conjugate may possess a linear structure, i.e., having one or two active agent molecules covalently attached to a linear water-soluble polymer, typically at each terminus of the linear water-soluble polymer. Alternatively, the conjugate may possess a forked, branched or multi-armed structure.
  • R(-Q-POLY 1 -X-D) q wherein R is an organic radical possessing from about 3 to about 150 carbon atoms, Q is a linker (preferably hydrolytically stable and may be —O—, —S—, —NH—C(O)— and —C(O)—NH—, POLY 1 is a water-soluble, non-peptidic polymer, X is spacer that comprises a hydrolyzable linkage, D is an active agent moiety, and q ranges from 3 to 25 (e.g., 3 to 10, such as any of 3, 4, 5, 6, 7, 8, 9 and 10).
  • R is an organic radical possessing from about 3 to about 150 carbon atoms
  • Q is a linker (preferably hydrolytically stable and may be —O—, —S—, —NH—C(O)— and —C(O)—NH—
  • POLY 1 is a water-soluble, non-peptidic polymer
  • X is spacer that comprises a hydrolyzable linkage
  • R(-Q-POLY 1 —CH 1 C(O)—NH—CH 2 —C(O)—O-D) q wherein: R is an organic radical possessing from 3 to 150 carbon atoms; Q is a linker, wherein R, when taken together with Q to form R(Q-) q , is a residue of a polyol or a polythiol after removal of “q” hydroxyl or thiol protons, respectively, to form a point of attachment for POLY 1 ;
  • POLY 1 is a water-soluble polymer selected from the group consisting of poly(alkylene glycol), poly(olefinic alcohol), poly(vinylpyrrolidone), poly(hydroxylalkyl-methacrylamide), poly(hydroxyalkyl-methacrylate), poly( ⁇ -hydroxy acid), poly(acrylic acid), poly(vinyl alcohol), polyphosphazene, polyoxazoline,
  • One illustrative multi-armed polymer conjugate structure corresponds to the following structure:
  • compositions comprising “4-arm-PEG-Gly-Irino” can be characterized as compositions comprising four-arm conjugates, wherein at least 90% of the four-arm conjugates in the composition:
  • the number of polymer arms will correspond to the number of active agent molecules covalently attached to the water-soluble polymer core. That is to say, in the case of a polymer reagent having a certain number of polymer arms (e.g., corresponding to the variable “q”), each having a reactive functional group (e.g., carboxy, activated ester such as succinimidyl ester, benzotriazolyl carbonate, and so forth) at its terminus, the optimized number of active agents (such as irinotecan) that can be covalently attached thereto in the corresponding conjugate is most desirably “q.” That is to say, the optimized conjugate is considered to have a drug loading value of 1.00(q) (or 100%).
  • q reactive functional group
  • the multi-armed polymer conjugate is characterized by a degree of drug loading of 0.90(q) (or 90%) or greater.
  • Preferred drug loadings satisfy one or more of the following: 0.92(q) or greater; 0.93(q) or greater; 0.94(q) or greater; 0.95(q) or greater: 0.96(q) or greater; 0.97(q) or greater; 0.98(q) or greater; and 0.99(q) or greater.
  • the drug loading for a multi-armed polymer conjugate is one hundred percent.
  • a composition comprising a multi-arm water soluble polymer conjugate mixed acid salt may comprise a mixture of molecular conjugates having one active agent attached to the polymer core, having two active agent molecules attached to the polymer core, having three active agents attached to the polymer core, and so on, up to and including a conjugate having “q” active agents attached to the polymer core.
  • the resulting composition will possess an overall drug loading value, averaged over the conjugate species contained in the composition.
  • the composition will comprise a majority, e.g., greater than 50%, but more preferably greater than 60%, still more preferably greater than 70%, still yet more preferably greater than 80%, and most preferably greater than 90%) of drug fully loaded polymer conjugates (i.e., having “q” active agent molecules for “q” arms, a single active agent molecule for each arm).
  • the idealized value of the number of covalently attached drug molecules per multi-armed polymer is four, and—with respect to describing the average in the context of a composition of such conjugates—there will be a value (i.e., percentage) of drug molecules loaded onto multi-armed polymer ranging from about 90% to about 100% of the idealized value. That is to say, the average number of drug molecules covalently attached to a given four-armed polymer (as part of a four-armed polymer composition) is typically 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, and 100% of the fully loaded value. This corresponds to an average number of D per multi-arm polymer conjugate ranging from about 3.60 to 4.0.
  • a multi-armed polymer conjugate composition e.g., where the number of polymer arms ranges from about 3 to about 8, e.g., greater than 50%, but more preferably greater than 60%, still more preferably greater than 70%, still yet more preferably greater than 80%, and most preferably greater than 90%
  • species present in the composition are those having either an idealized number of drug molecules attached to the polymer core (“q”) or those having a combination of (“q”) and (“q ⁇ 1”) drug molecules attached to the polymer core.
  • a multi-armed polymer conjugate such as described herein is prepared, where the resulting conjugate exhibits a high degree of substitution or drug loading in the context of the ranges provided above.
  • Illustrative conjugates thus prepared will generally have a drug loading value of at least 90%, and may typically possess drug loading values of greater than 91%, or greater than 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%, and in some cases, at 100% of the fully loaded value.
  • multi-armed polymer conjugates prepared from multi-arm polymeric starting materials that are prepared, e.g., in accordance with the alkoxylation methodology provided herein may exhibit higher drug substitution values, clue, at least in part, to the purity of the polymeric starting material.
  • 4-arm PEG-CM-SCM (e.g., having a molecular weight greater than about 10 kilodaltons) prepared from 4-arm PEG-OH prepared according to the alkoxylation method provided herein, may possess, on average, a higher level of purity with respect to the particular polymer species present in the 4-arm-PEG-CM-SCM reactant material than obtained with other commercially available 4-arm PEG-OH starting materials (e.g., having fewer low molecular weight polymer impurities).
  • the level of purity of a multi-arm PEG starting material can contribute to the purity of the final conjugate product in the event that non-desired polymer materials present in the polymeric starting material are “carried along” in subsequent transformation steps.
  • an active agent such as deprotected glycine-irinotecan
  • utilization of a polymeric starting material having a relatively high amount of polymeric impurities can impact the purity and drug loading values of the resulting conjugate species, in certain cases by several percent.
  • polymer conjugates prepared from starting materials prepared using the alkoxylation method described herein may therefore exhibit higher bioavailabilities than polymer conjugates prepared from commercially available multi-arm starting materials containing up to, e.g., 20% (e.g., 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20%), low molecular weight or other polymer impurities.
  • the partial mixed salt may comprise any one or more of the following structures, in addition to the fully drug loaded structure (i.e., having a glycine-modified irinotecan molecule covalently attached to each of the four polymer arms):
  • the multi-arm polymer conjugate compositions provided herein are intended to encompass any and all stereoisomeric forms of the conjugates comprised in such compositions.
  • the stereochemistry at C-20 of irinotecan, when in conjugated form such as in compositions of 4-arm-PEG-Gly-irino remains intact, i.e., C-20 retains its (S)-configuration when in its conjugated form. See, e.g., Example 4.
  • Yet another preferred multi-armed structure is a carboxymethyl modified 4-arm pentaerythritolyl PEG having a glycine linker intervening between the polymer portion in each arm and the active agent (polymer portion and linker shown above), where the active agent is 7-ethyl-10-hydroxy-camptothecin.
  • the multi-arm polymer is (i) fully loaded, as well as having (ii) three 7-ethyl-10-hydroxy-camptothecin molecules covalently attached thereto, (iii) two 7-ethyl-10-hydroxy-camptothecin molecules covalently attached thereto, and (iv) one 7-ethyl-10-hydroxy-camptothecin molecule covalently attached to the four-arm polymer core.
  • Yet another representative multi-armed conjugate structure is a carboxymethyl modified 4-arm glycerol dimer (3,3′-oxydipropane-1,2-diol) PEG having 7-ethyl-10-hydroxy-camptothecin (SN-38) molecules covalently attached to the polymer core.
  • the multi-armed polymer core is fully loaded with drug (i.e., having four 7-ethyl-10-hydroxy-camptothecin molecules covalently attached thereo), or is less than fully loaded (i.e., having one, two, or three 7-ethyl-10-hydroxy-camptothecin molecules covalently attached thereto) are included herein.
  • the conjugate having drug (i.e., 7-ethyl-10-hydroxy-camptothecin) covalently attached to each polymer arm is shown below.
  • the conjugate is a multi-armed structure comprising a carboxymethyl modified 4-arm glycerol dimer (3,3′-oxydipropane-1,2-diol) PEG having irinotecan molecules covalently attached to the polymer core.
  • the multi-armed polymer core is fully loaded with drug (i.e., having four irinotecan molecules covalently attached thereo), or is less than fully loaded (i.e., having one, two, or three irinotecan molecules covalently attached thereto) are included herein.
  • the subject compositions can be, among other things, partial mixed acid salts. That is to say, mixed salt conjugates are provided in a composition such that basic nitrogen atoms in the conjugate (as well as in the bulk composition) may individually be present in either protonated or non-protonated forms with the protonated nitrogen atoms (referred to as acid salts) having one of two different counter anions.
  • One anion corresponds to the conjugate base of a strong inorganic acid such as a hydrohalic acid, sulfuric acid, nitric acid, phosphoric acid, nitrous acid, and the like; the other anion corresponds to the conjugate base of a strong organic acid such as trifluoroacetate.
  • the subject mixed acid salt compositions are stably and reproducibly prepared.
  • a mixed acid salt as provided herein is characterized in terms of its bulk or macro properties. That is to say, basic nitrogen atoms (i.e., amino groups) in the conjugate exist individually in either neutral (non-protonated) or protonated form, the protonated forms associated with one of two different possible counterions. While the present compositions are characterized based on bulk properties, different individual molecular species are contained within the bulk composition. Taking the exemplary 4-arm polymer conjugate described in Example 1,4-arm-PEG-Gly-Irino-20K, the mixed acid salt product contains any of a number of individual molecular species.
  • each polymer arm contains an irinotecan molecule that is in neutral form, i.e., its amino group is unprotonated. See structure I below.
  • Another molecular species is one in which each polymer arm contains an irinotecan molecule in protonated form. See structure IV below.
  • An additional molecular species is one in which three of the polymer arms contain an irinotecan molecule that is in protonated form, and one polymer arm contains an irinotecan molecule in neutral form (structure III).
  • two of the four polymer arms contain an irinotecan molecule in neutral form (i.e., its amino group is unprotonated), and two of the four polymer arms contain an irinotecan molecule that is in protonated form (structure II).
  • irinotecan molecule in neutral form (i.e., its amino group is unprotonated)
  • structure II in protonated form
  • sub-species of molecules are possible containing different combinations of counterions.
  • the schematic below illustrates various possible combinations; the table that follows indicates possible combinations of protonated acid salts corresponding to each structure.
  • polymer prodrug conjugates are obtained as mixed acid salts of both hydrochloric acid and trifluoroacetic acid.
  • hydrochloric acid is introduced by the use of an acid salt form of the active agent molecule to form the resulting polymer conjugate, while the trifluoroacetic acid is introduced to the reaction mixture in a deprotection step (although any strong acid may be used).
  • the active agent or modified active agent as illustrated in Example 1
  • the resulting conjugate is unexpectedly and reproducibly obtained as a partial mixed acid salt having surprising and beneficial properties, to be described in greater detail below.
  • the mixed acid salt conjugates described herein preferably contain fairly well-defined proportions and ranges of each component (i.e., free base, inorganic acid salt, organic acid salt).
  • the characteristics of the mixed acid salt product may of course, vary depending upon changes to the synthesis conditions employed.
  • the polymer conjugate mixed acid salt is consistently recovered as having the greatest relative molar amount of basic nitrogen atoms in protonated form in comparison to free base (or unprotonated) nitrogens (calculated with respect to basic nitrogen atoms in the active agent).
  • free base (or unprotonated) nitrogens calculated with respect to basic nitrogen atoms in the active agent.
  • the partial mixed salt composition is characterized as having the greatest relative molar amount of TFA salt (in comparison to hydrochloride salt and free base). In yet another particular embodiment, the partial mixed salt composition is characterized as typically comprising a lesser relative molar amount of hydrohalic salt (in comparison to TFA salt), and even less of unprotonated (free base) nitrogens. In one embodiment, the partial mixed salt composition comprises approximately 30-75 mole percent TFA salt, approximately 15-45 mole percent hydrohalic acid salt, and 2-55 mole percent free base. These relative amounts may of course vary with variations in process conditions for making the mixed acid salt.
  • the mole percentage of trifluoroacetic acid salt ranges from about 45 to 70
  • the mole percentage of hydrochloric acid salt ranges from about 20 to 38
  • the mole percentage of free base ranges from about 10 to 35.
  • active agent basic nitrogen (e.g., amino) groups within the conjugate are present in the highest molar percentage as the trifluoroacetic acid salt, in the second highest molar percentage as the hydrochloric acid salt, and in the third or least highest molar percentage as the free base.
  • the mole percentages of hydrochloride salt and free base in the conjugate are about the same.
  • the product contained about 50 mole percent trifluoroacetic acid salt, about 30 mole percent hydrochloric acid salt, and about 20 mole percent free base.
  • Example 6 it can be seen that mixed acid salt conjugates have been prepared, where the relative molar amounts of each of TFA salt, hydrodrochloride salt, and unprotonated material among the four different lots exhibit a high level of consistency. Similar to the results in Example 1, the polymer conjugate mixed acid salt is consistently recovered as having the greatest relative molar amount of basic nitrogen atoms in protonated form in comparison to free base (or unprotonated) nitrogens (calculated with respect to basic nitrogen atoms in the active agent). In the lots summarized in Table 2, the partial mixed salt compositions having the greatest relative molar amount of HCl salt in comparison to TFA salt and free base.
  • the partial mixed salt composition may be characterized as typically comprising a lesser relative molar amount of TFA salt in comparison to the HCl salt, and even less of unprotonated (free base) nitrogens.
  • the partial mixed salt composition will comprises at least about 20 mole percent TFA, or at least about 25 mole percent TFA. Exemplary ranges of TFA salt within the mixed salt composition may range from about 20-45 mole percent, or from about 24-38 mole percent, or even from about 35 to 65 mole percent.
  • the composition may, in certain embodiments, possess from about 30 to 65 mole percent hydrochloride, or from about 32 to 60 mole percent hydrochloride, or preferably, from about 35 to 57 mole percent hydrochloride.
  • the mixed acid salt conjugates described herein were generally found to possess greater stability than either the pure HCl salt or the free base forms of the conjugate. See, e.g., Example 3 and FIG. 1 , illustrating the results of stress stability tests on compositions containing varied amounts of salt and free base forms of an exemplary conjugate. 4-arm-PEG-GLY-IRT. A positive correlation was observed between increased stability towards hydrolysis and increased molar percentage of salt in the final conjugate product. Based upon the slopes of the graphs, it can be determined that as free base content increases, product stability decreases. A correlation between decrease in product and increase in irinotecan over time was observed, thereby leading to a determination that the mode of decomposition observed under the conditions employed was ester bond hydrolysis.
  • FIG. 2 further illustrates that stability (or resistance) against hydrolytic degradation is greater for conjugates possessing a greater degree of protonated amine groups (i.e., acid salt). For instance, it was observed that conjugate product containing 14 molar percent or more free base was notably less stable towards hydrolysis than the corresponding acid salt-rich product.
  • product rich in the hydrochloride salt appears to be more susceptible to cleavage of the water-soluble polymer backbone than the mixed salt form containing a measurable amount of free base.
  • decomposition of the mixed salt conjugate appears to be attributable primarily to hydrolytic release of drug rather than cleavage of the polymer backbone.
  • Such backbone decomposition appears, however, to be relevant only under accelerated stress conditions.
  • mixed salt forms of the conjugate are prepared in high lot-to-lot consistency—that is to say, having relatively consistent molar ratios of trifluoroacetate, halide (or other suitable inorganic acid anion) and free base in the final conjugate product.
  • Table 1 of Example 2 roughly 50 mole percent of drug basic nitrogen groups are associated with trifluoroacetic acid. This mole percentage is fairly consistently observed from lot-to-lot.
  • roughly 30 mole percent of conjugate drug amino (or other basic nitrogen) groups are fairly consistently associated with hydrochloric acid, i.e., provided as the HCl salt. It follows that the free base form of drug amino (or other basic nitrogen) groups in the conjugate are also stably and reproducibly prepared.
  • Example 6 based upon a slightly revised manufacturing method, it can be seen that despite differences in the actual relative molar amounts of protonated and unprotonated species, and within the protonated species; TFA versus hydrochloride salt, mixed acid salts were reproducibly prepared.
  • a mixed acid salt of a water soluble polymer conjugate can be readily prepared from commercially available starting materials in view of the guidance presented herein, coupled with what is known in the art.
  • the mixed salt polymer-active agent conjugate comprises a water-soluble polymer covalently attached to one or more active agent molecules each possessing one or more basic nitrogen atoms, such as an amino group, when in conjugated form.
  • Amine groups in the resulting conjugate may be primary, secondary, or tertiary amino groups.
  • Linear, branched, and multi-arm water-soluble polymer reagents are available from a number of commercial sources as described above.
  • PEG reagents such as a multi-armed reactive PEG polymer may be synthetically prepared as described herein.
  • the partial mixed acid salt can be formed using known chemical coupling techniques for covalent attachment of activated polymers, such as an activated PEG, to a biologically active agent (See, for example, POLY ( ETHYLENE GLYCOL ) CHEMISTRY AND BIOLOGICAL APPLICATIONS , American Chemical Society, Washington, D.C. (1997); and U.S. Patent Publication Nos. 2009/0074704 and 2006/0239960). Selection of suitable functional groups, linkers, protecting groups, and the like to achieve a mixed acid salt in accordance with the invention; will depend, in part, on the functional groups on the active agent and on the polymer starting material and will be apparent to one skilled in the art, based upon the content of the present disclosure.
  • the method comprises provision of an amine—(or other basic nitrogen)-containing active agent in the form of an inorganic acid addition salt, and a trifluoroacetic acid treatment step.
  • the conjugate product or an intermediate in the synthetic pathway can be reacted with an inorganic acid to form an inorganic acid addition salt at a later stage in the process, to thereby introduce a second counterion (in addition to trifluoroacetate) into the reaction.
  • Reference to an “active agent” in the context of the synthetic method is meant to encompass an active agent optionally modified to possess a linker covalently attached thereto, to facilitate attachment to the water-soluble polymer.
  • the method comprises the steps of (i) deprotecting an inorganic acid salt of an amine—(or other basic nitrogen)-containing active agent in protected form by treatment with trifluoroacetic acid (TFA) to form a deprotected mixed acid salt, (ii) coupling the deprotected inorganic acid salt of step (i) with a water-soluble polymer reagent in the presence of a base to form a polymer-active agent conjugate, and (iii) recovering the polymer active agent conjugate.
  • the resulting polymer-active agent conjugate composition is characterized by having the one or more amino (or other basic nitrogen-containing) groups present in a combination of free base, acid salt, and TFA salt form.
  • the product therefore comprises both inorganic acid salt and trifluoroacetate salt, as well as a proportion of basic groups in the conjugate that are in unprotonated or free base form.
  • the combined molar amounts of inorganic acid salt and trifluoroacetic acid salt are less than the total number of basic amino or other nitrogens contained in the conjugate product.
  • the camptothecins since the 20-hydroxyl group of compounds within the camptothecin family is sterically hindered, a single step conjugation reaction is difficult to accomplish in significant yields.
  • a preferred method is to react the 20-hydroxyl group of the bioactive starting material, e.g., irinotecan hydrochloride, with a short linker or spacer moiety carrying a functional group suitable for reaction with a water-soluble polymer.
  • a short linker or spacer moiety carrying a functional group suitable for reaction with a water-soluble polymer.
  • Preferred linkers for reaction with a hydroxyl group to form an ester linkage include t-BOC-glycine or other amino acids such as alanine, glycine, isoleucine, leucine, phenylalanine, and valine having a protected amino group and an available carboxylic acid group (See Zalipsky et al, “Attachment of Drugs to Polyethylene Glycols”, Eur. Polym. J ., Vol. 19, No. 12, pp. 1177-1183 (1983)).
  • Other spacer or tinker moieties having an available carboxylic acid group or other functional group reactive with a hydroxyl group and having a protected amino group can also be used in lieu of the amino acids described above.
  • Typical labile protecting groups include t-BOC and FMOC (9-flourenylmethloxycarbonyl).
  • t-BOC is stable at room temperature and easily removed with dilute solutions of trifluoroacetic acid and dichloromethane.
  • FMOC is a base labile protecting group that is easily removed by concentrated solutions of amines (usually 20-55% piperidine in N-methylpyrrolidone).
  • the carboxyl group of N-protected glycine reacts with the 20-hydroxyl group of irinotecan hydrochloride (or other suitable camptothecin, such as 7-ethyl-10-hydroxy-camptothecin, or any other active agent) in the presence of a coupling agent (e.g., dicyelobexylcarbodiimide (DCC)) and a base catalyst (e.g., dimethylaminopyridine (DHAP) or other suitable base) to provide N-protected linker modified active agent, e.g., t-Boc-glycine-irinotecan hydrochloride.
  • a coupling agent e.g., dicyelobexylcarbodiimide (DCC)
  • a base catalyst e.g., dimethylaminopyridine (DHAP) or other suitable base
  • DHAP dimethylaminopyridine
  • each reaction step is conducted under an inert atmosphere.
  • the amino protecting group, t-BOC(N-tert-butoxycarbonyl), is removed by treatment with trifluoroacetic acid (TFA) under suitable reaction conditions. It is in this step that trifluoroacetic acid is typically introduced into the reaction mixture.
  • the product is linker modified active agent, e.g., 20-glycine-irinotecan TFA/HCl. Illustrative reaction conditions are described in Example 1, and may be further optimized by routine optimization by one of skill in the art.
  • the molar amounts of inorganic acid and trifluoroacetic acid in the decoupled product are determined by a suitable analytical method such as HPLC or ion chromatography, to allow greater precision and product consistency in the coupling step.
  • Deprotected active agent (optionally linker modified), e.g., 20-glycine-irinotecan TFA/HCl
  • a desired polymer reagent e.g., 4-arm pentaerythritolyl-PEG-succinimide (or any other similarly activated ester counterpart) in the presence of a coupling agent (e.g., hydroxybenzyltriazole (HOBT)) and a base (e.g., DMAP, trimethyl amine, triethyl amine, etc.), to form the desired conjugate.
  • a coupling agent e.g., hydroxybenzyltriazole (HOBT)
  • a base e.g., DMAP, trimethyl amine, triethyl amine, etc.
  • the amount of base added in the conjugation step is in a range of approximately 1.0 to 2.0 times, or from about 1.0 to 1.5 times, or from about 1.0 to 1.05 times, the sum of the moles of TFA and the moles of inorganic acid determined for the starting material, in this case, 20-glycine-irinotecan TFA/HCl.
  • the resulting partial mixed acid salt is reproducibly prepared such that the relative molar amounts of inorganic addition salt, trlfluoroacetic acid salt, and free base in the conjugate composition vary by no more than about 25%, and even more preferably by no more than about 15%, from batch to batch.
  • the foregoing measure of consistency is determined over at least five batches (e.g., from 5 to 7), where failed batches that are clearly outliers are excluded from the calculation.
  • conjugation step is conducted in the presence of excess base, it is surprising to discover that the resulting conjugate is stably formed as a partial mixed acid salt, i.e., such that a significant amount of basic amino or other nitrogen containing groups in the conjugate are protonated rather than being in free base form.
  • Reaction yields for the coupling reaction are typically high, greater than about 90% (e.g., about 95% on average).
  • the partial mixed acid salt conjugate is recovered, e.g., by precipitation with ether (e.g., methyl tert-butyl ether, diethyl ether) or other suitable solvent.
  • ether e.g., methyl tert-butyl ether, diethyl ether
  • the product may be further purified by any suitable method. Methods of purification and isolation include precipitation followed by filtration and drying, as well as chromatography. Suitable chromatographic methods include gel filtration chromatography, ion exchange chromatography, and Biotage Flash chromatography. One preferred method of purification is recrystallization.
  • the partial mixed acid salt is dissolved in a suitable single or mixed solvent system (e.g., isopropanol/methanol), and then allowed to crystallize.
  • Recrystallization may be conducted multiple times, and the crystals may also be washed with a suitable solvent in which they are insoluble or only slightly soluble (e.g., methyl tert-butyl ether or methyl-tert-butyl ether/methanol).
  • the purified product may optionally be further air or vacuum dried. Even upon repeated purification, the product is typically recovered as a mixed acid salt rather than as the free base. Even upon additional treatment with base, the conjugate remained in the form of a partial mixed acid salt having the features described herein.
  • the resulting conjugate is a partial mixed salt, i.e., where certain of the basic nitrogen atoms are in neutral or free base form and other basic nitrogen atoms, e.g., amino groups, are protonated.
  • the protonated amine groups are in the form of acid salts with differing anions, one anion corresponding to the conjugate base of an inorganic acid, the other anion being trifluoroacetate (or the conjugate base of an organic acid as previously described).
  • a partial mixed salt refers to the bulk product rather than necessarily referring to individual molecular species contained within the bulk product.
  • individual molecular species contained within the mixed salt may contain amine groups that are in free base and in protonated form as described above.
  • a mixed salt may contain a mixture of molecular species (e.g., having all amine groups in free base form, having all amine groups in protonated form, either as the salt of an inorganic acid, the salt of trifluoroacetic acid or other suitable organic acid, or a mixture of both, various combinations of the foregoing, etc.), such that the features of the bulk product are as described herein.
  • the conjugate is a polymer conjugate comprising only one active agent amine group.
  • the mixed salt must necessarily be such that the bulk product is a mixture of molecular species to arrive at a mixed salt as described generally herein.
  • the mixed acid salt product is stored under conditions suitable for protecting the product from exposure to any one or more of oxygen, moisture, and light. Any of a number of storage conditions or packaging protocols can be employed to suitably protect the acid salt product during storage.
  • the product is packaged under an inert atmosphere (e.g., argon or nitrogen) by placement in one or more polyethylene bags, and placed in an aluminum lined polyester heat sealable bag.
  • the partial mixed acid salt conjugates may be in the form of a pharmaceutical formulation or composition for either veterinary or human medical use.
  • An illustrative formulation will typically comprise a partial mixed acid salt conjugate in combination with one or more pharmaceutically acceptable carriers, and optionally any other therapeutic ingredients, stabilizers, or the like.
  • the carrier(s) must be pharmaceutically acceptable in the sense of being compatible with the other ingredients of the formulation and not unduly deleterious to the recipient/patient.
  • the partial mixed acid salt conjugate is optionally contained in bulk or in unit dose form in a container or receptacle which includes packaging that protects the product from exposure to moisture and oxygen.
  • the pharmaceutical composition may include polymeric excipients/additives or carriers, e.g., polyvinylpyrrolidones, derivatized celluloses such as hydroxymethylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose, Ficolls (a polymeric sugar), hydroxyethylstarch (HES), dextrates (e.g., cyclodextrins, such as 2-hydroxypropyl- ⁇ -cyclodextrin and sulfobutylether- ⁇ -cyclodextrin), polyethylene glycols, and pectin.
  • polymeric excipients/additives or carriers e.g., polyvinylpyrrolidones, derivatized celluloses such as hydroxymethylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose, Ficolls (a polymeric sugar), hydroxyethylstarch (HES), dextrates (e.g., cyclodext
  • compositions may further include diluents, buffers, binders, disintegrants, thickeners, lubricants, preservatives (including antioxidants), flavoring agents, taste-masking agents, inorganic salts (e.g., sodium chloride), antimicrobial agents (e.g., benzalkonium chloride), sweeteners, antistatic agents, surfactants (e.g., polysorbates such as “TWEEN 20” and “TWEEN 80”, and pluronics such as F68 and F88, available from BASF), sorbitan esters, lipids (e.g., phospholipids such as lecithin and other phosphatidylcholines, phosphatidylethanolamines, fatty acids and fatty esters, steroids (e.g., cholesterol)), and chelating agents (e.g., EDTA, zinc and other such suitable cations).
  • diluents e.g., buffers, binders, disintegrants, thicken
  • compositions according to the invention are listed in “Remington: The Science & Practice of Pharmacy”, 19 th ed. Williams & Williams, (1995), and in the “Physician's Desk Reference”, 52 nd ed., Medical Economics, Montvale, N.J. (1998), and in “Handbook of Pharmaceutical Excipients”, Third Ed., Ed. A.H. Kibbe, Pharmaceutical Press, 2000.
  • the mixed acid salt may be formulated in a composition suitable for oral, rectal, topical, nasal, ophthalmic, or parenteral (including intraperitoneal, intravenous, subcutaneous, or intramuscular injection) administration.
  • the mixed acid salt composition 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 mixed acid salt into association with a carrier that constitutes one or more accessory ingredients.
  • the mixed acid salt e.g., 4-arm-PEG-Gly-Irino-20K
  • the amount of conjugate product contained in the single use vial is the equivalent of a 100-mg dose of irinotecan.
  • the lyophilized composition includes 4-arm-PEG-Gly-Irino-20K(combined with lactate buffer at pH 3.5.
  • the lyophilized composition is prepared by combining 4-arm-PEG-Gly-Irino-20K, e.g., in an amount equivalent to a 100-mg dose of irinotecan, with approximately 90 mg of lactic acid, and the pH of the solution adjusted to 3.5 by addition of either acid or base.
  • the resulting solution is then lyophilized under sterile conditions, and the resulting powder is stored at ⁇ 20° C. prior to use.
  • the lyophilized composition Prior to intravenous infusion, is combined with a solution of dextrose, e.g., a 5% (w/w) solution of dextrose.
  • the amount of mixed acid salt (i.e., active agent) in the formulation will vary depending upon the specific active agent employed, its activity, the molecular weight of the conjugate, and other factors such as dosage form, target patient population, and other considerations, and will generally be readily determined by one skilled in the art.
  • the amount of conjugate in the formulation will be that amount necessary to deliver a therapeutically effective amount of the compound, e.g., an alkaloid anticancer agent such as irinotecan or SN-38, to a patient in need thereof to achieve at least one of the therapeutic effects associated with the compound, e.g., for treatment of cancer.
  • compositions will generally contain anywhere from about 1% by weight to about 99% by weight conjugate, typically from about 2% to about 95% by weight conjugate, and more typically from about 5% to 85% by weight conjugate, and will also depend upon the relative amounts of excipients/additives contained in the composition. More specifically, the composition will typically contain at least about one of the following percentages of conjugate: 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, or more by weight.
  • compositions suitable for oral administration may be provided as discrete units such as capsules, cachets, tablets, lozenges, and the like, each containing a predetermined amount of the conjugate as a powder or granules; or a suspension in an aqueous liquor or non-aqueous liquid such as a syrup, an elixir, an emulsion, a draught, and the like.
  • Formulations suitable for parenteral administration conveniently comprise a sterile aqueous preparation of the mixed acid salt conjugate, which can be formulated to be isotonic with the blood of the recipient.
  • Nasal spray formulations comprise purified aqueous solutions of the multi-armed polymer conjugate with preservative agents and isotonic agents. Such formulations are preferably adjusted to a pH and isotonic state compatible with the nasal mucous membranes.
  • Formulations for rectal administration may be presented as a suppository with a suitable carrier such as cocoa butter, or hydrogenated fats or hydrogenated fatty carboxylic acids.
  • Ophthalmic formulations are prepared by a similar method to the nasal spray, except that the pH and isotonic factors are preferably adjusted to match that of the eye.
  • Topical formulations comprise the multi-armed polymer conjugate dissolved or suspended in one or more media such as mineral oil, petroleum, polyhydroxy alcohols or other bases used for topical formulations.
  • media such as mineral oil, petroleum, polyhydroxy alcohols or other bases used for topical formulations.
  • the addition of other accessory ingredients as noted above may be desirable.
  • compositions are also provided which are suitable for administration as an aerosol, e.g., by inhalation. These formulations comprise a solution or suspension of the desired multi-armed polymer conjugate or a salt thereof.
  • the desired formulation may be placed in a small chamber and nebulized. Nebulization may be accomplished by compressed air or by ultrasonic energy to form a plurality of liquid droplets or solid particles comprising the conjugates or salts thereof.
  • the mixed acid salts described herein can be used to treat or prevent any condition responsive to the unmodified active agent in any animal, particularly in mammals, including humans.
  • One representative mixed acid salt, 4-arm-pentaerythritolyl-PEG-glycine-irinotecan, comprising the anti-cancer agent, irinotecan, is particularly useful in treating various types of cancer.
  • the partial mixed acid salts conjugates are useful in treating solid type tumors such as breast cancer, ovarian cancer, colon cancer, gastric cancer, malignant melanoma, small cell lung cancer, non-small cell lung cancer, thyroid cancers, kidney cancer, cancer of the bile duct, brain cancer, cervical cancer, maxillary sinus cancer, bladder cancer, esophageal cancer, Hodgkin's disease, adrenocortical cancer, and the like.
  • mixed acid salts include lymphomas, leukemias, rhabdomyosarcoma, neuroblastoma, and the like.
  • the mixed salt conjugates are particularly effective in targeting and accumulating in solid tumors.
  • the mixed salt conjugates are also useful in the treatment of HIV and other viruses.
  • conjugates such as 4-arm-pentaerythritolyl-PEG-glycine-irinotecan have also been shown to be particularly advantageous when used to treat patients having cancers shown to be refractory to treatment with one or more anticancer agents.
  • Methods of treatment comprise administering to a mammal in need thereof a therapeutically effective amount of a partial mixed acid salt composition or formulation as described herein.
  • Additional methods include treatment of (i) metastatic breast cancer that is resistant to anthracycline and/or taxane based therapies, (ii) platinum-resistant ovarian cancer, (iii) metastatic cervical cancer, and (iv) colorectal cancer in patients with K-Ras mutated gene status by administering a partial mixed acid salt composition.
  • a mixed acid salt of a conjugate such as 4-arm-pentaerythritolyl-PEG-glycine-irinotecan as provided herein is administered to a patient with locally advanced metastatic breast cancer at a therapeutically effective amount, where the patient has had no more than two prior (unsuccessful) treatments with anthracycline and/or taxane based chemotherapeutics.
  • a composition as provided herein is administered to a patient with locally advanced or metastatic ovarian cancer at a therapeutically effective amount, where the patient has shown tumor progression during platinum-based therapy, with a progression-free interval of less than six months.
  • a mixed acid salt (e.g., such as that in Example 1) is administered to a subject with locally advanced colorectal cancer, where the colorectal tumor(s) has a K-Ras oncogene mutation (K-Ras mutant types) such that the tumor does not respond to EGFR-inhibitors, such as cetuximab.
  • Subjects are those having failed one prior 5-FU containing therapy, and are also irinotecan na ⁇ ve.
  • a therapeutically effective dosage amount of any specific mixed acid salt will vary from conjugate to conjugate, patient to patient, and will depend upon factors such as the condition of the patient, the activity of the particular active agent employed, the type of cancer, and the route of delivery.
  • camptothecin-type active agents such as irinotecan or 7-ethyl-10-hydroxy-camptothecin
  • dosages from about 0.5 to about 100 mg camptothecin/kg body weight, preferably from about 10.0 to about 60 mg/kg, are preferred.
  • even less of the mixed acid salt may be therapeutically effective.
  • the dosage amount of irinotecan will typically range from about 50 mg/m 2 to about 350 mg/m 2 .
  • Methods of treatment also include administering a therapeutically effective amount of a mixed acid salt composition or formulation as described herein (e.g., where the active agent is a camptothecin type molecule) in conjunction with a second anticancer agent.
  • a mixed acid salt composition or formulation as described herein e.g., where the active agent is a camptothecin type molecule
  • camptothecin-based conjugates are administered in combination with 5-fluorouracil and folinic acid as described in U.S. Pat. No. 6,403,569.
  • the mixed acid salt compositions may be administered once or several times a day, preferably once a day or less.
  • the duration of the treatment may be once per day for a period of from two to three weeks and may continue for a period of months or even years.
  • the daily dose can be administered either by a single dose in the form of an individual dosage unit or several smaller dosage units or by multiple administration of subdivided dosages at certain intervals.
  • Pentaerythritolyl-based 4-ARM-PEG 20K -OH was obtained from NOF Corporation (Japan). 4-ARM-PEG 20K -OH possesses the following structure (wherein each n is about 113): C—(CH 2 O—(CH 2 CH 2 O) N H) 4 .
  • Irinotecan-HCl-trihydrate (1 mole or 677 g) and DMF (10 L) were charged into a distiller at 60T.
  • full vacuum was slowly applied in order to remove water from the irinotecan-HCl-trihydrate by azeotropic distillation at 60° C.
  • heptane up to 60 L was charged into the distiller to remove residual DMF at 40-50° C.
  • the azeotropic distillation was stopped and the solid (irinotecan-HCl) was allowed to cool to 17 ⁇ 2° C.
  • the resulting clear solution was cooled to room temperature, followed by its addition to heptane with mixing. The mixture was mixed for an additional 0.5 to 1 hour, during which time a precipitate formed. The precipitate was drained and filtered to obtain a wet cake, and then washed with heptane (up to 6 L). The wet cake was vacuum-dried to yield t-boc-glycine-irinotecan powder for use in Step 2. Yield >95%.
  • the t-boc-glycine-irinotecan (1 mole) from Step 1 was dissolved in DCM with agitation to form a visually homogeneous solution.
  • TFA 15.8 mole
  • Residual starting material was measured by RP-HPLC and determined to be less than about 5%.
  • Acetonitrile was then added to the reaction solution to form a visually homogeneous solution at R.T. This solution was then added to MTBE (46.8 kg) being sufficiently agitated at 35° C. to promote crystallization.
  • DCM in the reaction solution was replaced with acetonitrile by distillation at 15 to 40° C.
  • the product-containing solution was added into approximately 50% less volume of MTBE (23 kg) being sufficiently agitated at the crystallization temperature (35° C.). Mixing was continued for a half to one hour. The resulting solid was filtered and the cake washed with MTBE.
  • the glycine-irinotecan-TFA/HCl salt powder from Step 2 was added to a reaction vessel to which was added DCM (approx. 23 L). The mixture was agitated for approximately 10 to 30 minutes to allow the glycine-irinotecan-TFA/HCl salt to disperse in DCM. Triethyl amine (approx. 1.05 moles (HCl TFA) moles in glycine-irinotecan TFA/HCl salt powder) was then added slowly, at a rate which maintained the pot temperature at 24° C. or below. The resulting mixture was agitated for 10 to 30 minutes to allow dissolution of the GLY-IRT (glycine-modified irinotecan) free base.
  • GLY-IRT glycine-modified irinotecan
  • Crude product was precipitated by adding the reaction solution into MTBE (113.6 L) agitated at room temperature over a period of from 1-1.5 hours, followed by stirring. The resulting mixture was transferred into a filter-drier with an agitator to remove the mother liquor. The precipitate (crude product) was partially vacuum-dried at approximately at 10 to 25° C. with minimum intermittent stirring.
  • Crude product was then placed into a reaction vessel, to which was added IPA (72 L) and MeOH (8 L), followed by agitation for up to 30 minutes. Heat was applied to achieve visually complete dissolution (a clear solution) at 50° C. pot temperature, followed by agitation for 30 to 60 minutes. The solution was then cooled to 37° C., held there for several hours, followed by cooling to 20° C. The mixture was transferred into an agitated filter dryer, and filtered to remove mother liquor to form a cake on a filter. The cake was washed with 70% MTBE in IPA and 30% MeOH and partially vacuum-dried.
  • API The product (“API”) was packaged into double bags sealed under an inert atmosphere, and stored at ⁇ 20° C. without exposure to light. Product yield was approximately 95%.
  • Example 1 The product from Example 1 was analyzed by ion chromatography (IC analysis). See Table 1 below for IC analytical results for various product lots of 4-arm-PEG-Gly-Irino-20K.
  • Example 1,4-arm-PEG-Gly-Irino-20K is a partial mixed salt of approximately 50 mole percent TFA salt, 30 mole percent HCl salt, and 20 mole percent free base, based upon conjugated irinotecan molecules in the product.
  • the mixture of salts was observed even after repeated (1-3) recrystallizations of the product.
  • Example 1,4-arm-PEG-Gly-Irino-20K, compound 5. (approximately 1-2 g) was weighed into PEG PE ‘whirl top’ bags and placed into another ‘whirl top’ bag in order to simulate the API packaging conditions.
  • samples were placed in an environmental chamber at 25° C./60% RH for 4 weeks.
  • samples were placed in an environmental chamber at 40° C./75% RH for up to several months (results shown in FIG. 2 and FIG. 3 ). Samples were taken and analyzed on a periodic basis over the course of the studies.
  • FIG. 1 4-arm-PEG-Gly-Irino-20K peak area percents for samples stored at 25° C. and 60% relative humidity are plotted versus time.
  • the data shown are for samples consisting of >99% HCl salt ( ⁇ 1% free base, triangles), 94% total salt (6% free base, squares), and 52% total salt (48% free base, circles).
  • the slopes of the graphs indicate that as free base content increases, the stability of the product decreases.
  • FIG. 2 and FIG. 3 show another set of data obtained from the sample containing >99% HCl salt ( ⁇ 1% free base, squares) and a sample consisting of 86% total salts (14% free base, diamonds) that were stored at 40° C. and 75% relative humidity.
  • FIG. 2 shows the increase in free irinotecan over 3 months for both samples. This data is consistent with the data from the previously described study (summarized in FIG. 1 ), which shows that product with a higher free base content is less stable with respect to hydrolysis.
  • FIG. 3 shows the increase in smaller PEG species for the same samples over 3 months. The increase in smaller PEG species is indicative of decomposition of the PEG backbone to provide multiple PEG species.
  • the irinotecan hydrochloride starting material is optically active, with C-20 in its (S)-configuration.
  • the C-20 position in irinotecan bears a tertiary alcohol, which is not readily ionizable, hence this site is not expected to racemize except under extreme (strongly acidic) conditions.
  • a chiral HPLC method was used to analyze irinotecan released from product via chemical hydrolysis.
  • All PEGylated irinotecan species are considered as part of 4-arm-PEG-Gly-Irino-20K; each specie cleanly hydrolyzes to produce irinotecan of >99% purity.
  • the main, fully drug-loaded DS4 species (dnig covalently attached on each of the four polymer arms) and the partially substituted species—DS3 (drug covalently attached on three polymer arms), DS2 (drug covalently attached on two of the polymer arms) and DS1 species (drug covalently attached on a single polymer arm)—all hydrolyze at the same rate to release free drug, irinotecan.
  • FIG. 5 and FIG. 6 present graphs which show the theoretical hydrolysis rates versus experimental data for the chemical hydrolysis (in the presence of enzyme) and plasma hydrolysis, respectively. In both cases, the theoretical predictions are based on identical rates for the hydrolysis of each species to produce the next-lower homologue plus free irinotecan (i.e., DS4>DS3>DS2>DSI).
  • IRT-HCl-3H 2 O (45.05 g, 66.52 mmol) was charged into a reactor.
  • Anhydrous N,N-dimethylformamide (DMF) (666 mL, 14.7 mL/g of IRT-HCl-3H 2 O, DMF water content NMT 300 ppm) was charged to the reactor. With slow agitation, the reactor was heated to 60° C. (jacket temperature). After the irinotecan (IRT) was fully dissolved (5-10 minutes), vacuum was slowly applied to reach 5-10 mbar and DMF was distilled off. When the volume of condensed distillate (DMF) reached 85-90% of the initial DMF charge, the vacuum was released.
  • DMF condensed distillate
  • Heptane (1330 mL, 30.0 mL/g of IRT-HCl-3H 2 O, water content NMT 50 ppm) was introduced into the reactor and the jacket temperature was lowered to 50° C. Heptane was vacuum distilled (100-150 mbar) until the volume of the distillate was about 90% of the initial charge of heptane. Two more cycles of heptane distillation were carried out (2 ⁇ 1330 mL heptane charge and distillation). A solvent phase sample was taken from the reactor and was analyzed for DMF content using GC to ensure a DMF content of less than 3% w/w. (In the event the residual DMF was >3.0% w/w, a fourth azeotropic distillation cycle would be performed). The resultant slurry was used for the coupling reaction (Part 2).
  • a DCM solution of DCC (1.5 equiv in 40 ml, of dichloromethane) was prepared and added into the reactor over 15-30 min, and the resultant reaction mixture was stirred at 17° C. (batch temperature) for 2-3 hr. The reaction was monitored by HPLC to ensure completion. A pre-made quenching solution was charged into the reaction mixture to quench any remaining DCC.
  • the pre-made quenching solution is a pre-mixed solution of TFA and IPA in dichloromethane, prepared by mixing TFA (1.53 mL, 0.034 mL/g IRT-HCl-3H 2 O) and IPA (3.05 mL, 0.068 mL/g IRT-HCl-3H 2 O) in DCM (15.3 mL, 0.34 mL/g IRT-HCl-3H 2 O), and was added to the reactor V1 over 5-10 minutes when the conversion was at least 97%. The contents were agitated for additional 30-60 min to allow quenching. The DCU-containing reaction mixture was filtered through a 1 micron filter into another reactor.
  • the reaction filtrate was distilled to 1 ⁇ 3 its volume under vacuum at 35 C.
  • Isopropyl alcohol (IPA) 490.5 mL, 10.9 mL/g IRT-HCl-3H 2 O
  • IPA isopropyl alcohol
  • the resulting homogeneous solution was concentrated by vacuum distillation to approximately 85% of the initial IPA charge volume and the resultant concentrate was cooled to 20° C. (jacket temperature).
  • the reaction mixture in WA was transferred over 60-80 min into heptane (1750 mL, 38.8 mL heptane/g IRT-HCl-3H 2 O) at 20° C.
  • Boc-Gly-IRT-HCl 41.32 g, 52.5 mmol, from step 1) under an inert atmosphere.
  • Anhydrous DCM (347 mL, 8.4 mL of DCM/g of Boc-Gly-IRT-HCl) was added to the reactor and the contents were agitated at 17° C. until complete dissolution (15-30 min approximately).
  • TFA 61.98 mL, 691.5 mmol, 1.5 mug of Boc-gly-IRT-HCl
  • the reaction was monitored for completion by HPLC (limit: not less than 97%).
  • the reaction was diluted with acetonitrile (347 ml., 8.4 mL of ACN/g of Boc-gly-IRT-HCl).
  • the jacket temperature was set to 15° C. and the reaction mixture was concentrated under vacuum until the final residual pot volume was approximately 85% of the initial acetonitrile charge (295-305 ml, approximately).
  • the resulting acetonitrile solution was added slowly to a reactor containing methyltert-butyl ether (MTBE, 1632 mL, 39.5 mL of MTBE/g of Boc-gly-IRT-HCl) over a period of 30-60 minutes.
  • the precipitated product was gently mixed for 30 minutes and collected by filtration.
  • the reactor was rinsed with MTBE (410 mL) and the gly-IRT-HCl/TFA filter cake was washed with the rinse.
  • the product was dried under vacuum at 17° C. for a minimum of 12 hours. Yield: 42.1 g (102%).
  • Gly-IRT HCl-TFA (10.0 g) was charged to a 250 mL reactor and flushed with argon. The jacket temperature was set at 20° C. DCM (166 mL) and TEA (2.94 g) were added. The solution was mixed for 10 minutes. An initial charge of 4-armPEG20K-SCM was added (47.6 g) and the reaction mixture stirred for 30 minutes. A sample was taken and analyzed by HPLC. The HPLC data showed 18% remaining Gly-IRT. A second charge of 4-armPEG20K-SCM (10.7 g) was added to the reaction mixture and the solution stirred for approximately 2 hours. A sample was withdrawn for HPLC analysis. The HPLC analysis data showed 1.5% remaining Gly-IRT.
  • the reaction solution was then slowly added to MTBE (828 mL) to precipitate the product.
  • the precipitate was stirred for 30 minutes and collected via filtration.
  • the wet cake was washed with a mixture of 30% Methanol/70% MTBE (830 mL).
  • the product was then charged to a reactor containing a mixture of 30% Methanol/70% MIRE (642 mL) and the mixture was stirred at 20° C. for 20 minutes.
  • the mixture was filtered and the wet cake was washed on the filter with a mixture of 30% Methanol/70% MTBE (642 mL).
  • the product was dried under vacuum at 20° C.
  • the dried product was charged to a reactor containing ethyl acetate (642 mL). The mixture was heated to 35° C. to achieve complete dissolution. The warm solution was filtered if necessary to remove undissolved particulates, and then cooled to 10° C. with stirring. The precipitated 4-armPEG20K-glycine-irinotecan hydrochloride-trifluoroacetate product was filtered and the wet cake was washed on the filter with a mixture of 30% Methanol/70% MTBE (642 mL). The product was then dried under vacuum at 20° C. Yield: 54 g (approximately 85%).
  • batches prepared as described show consistent ratios of TEA salt, hydrochloride salt and free base. Based upon a review of the batch information, it appears that a higher chloride content in the glycine-irinotecan TFA/HCl intermediate leads to a higher the chloride content in the final mixed salt conjugate product.
  • a starting material such as irinotecan hydrochloride having a fairly constant chloride content
  • a glycine-irinotecan TFA/HCl salt can be prepared having a fairly constant chloride content.
  • preferred ranges of TFA in the mixed acid salt conjugate are from about 20 to about 45 mole percent, preferably from about 22 to 40 mole percent, or from about 24 to 38 mole percent.
  • preferred ranges in the mixed acid salt conjugate are from about 30 to 65 mole percent chloride, or from about 32 to 60 mole percent chloride, or from about 35 to 57 mole percent chloride.
  • Ethylene oxide is a very reactive compound that can react explosively with moisture, thus leaks in the reaction and transfer apparatus should carefully avoided. Also, care should be taken in operations to include having personnel work behind protective shields or in bunkers.
  • Anhydrous toluene (4 L) was refluxed for two hours in a two gallon jacketed stainless steel pressure reactor. Next, a part of the solvent (3 L) was distilled off under atmospheric pressure. The residual toluene was then discharged out and the reactor was dried overnight by passing steam through the reactor jacket and applying reduced pressure 3-5 mm Hg. Next the reactor was cooled to room temperature, filled with anhydrous toluene (4 L) and pentaerythitol based 4ARM-PEG-2K (SUNBRIGHT PTE®-2000 pentaerythritol, molecular weight of about 2,000 Daltons, NOF Corporation; 200 g, 0.100 moles) was added.
  • the solvent was distilled off under reduced pressure, and then the reactor was cooled to 30° C. under dry nitrogen atmosphere.
  • One liter of molecular sieves-dried toluene (water content ⁇ 5 ppm) and liquid sodium-potassium alloy (Na 22%, K 78%; 1.2 g) were added to the reactor.
  • the reactor was warmed to 110° C. and ethylene oxide (1,800 g) was continuously added over three hours keeping the reaction temperature at 110-120° C. Next, the contents of the reactor were heated for two hours at 100° C., and then the temperature was lowered to 70° C. Excess ethylene oxide and toluene were distilled off under reduced pressure.
  • GFC Gel Filtration Chromatography
  • NOF Corporation is a current leader in providing commercial PEGs.
  • a fresh commercially available pentaerythritol-based 4ARM-PEG-20K (SUNBRIGHT PTE®-20,000, molecular weight of about 20,000 Daltons, NOF Corporation) was obtained and analyzed using Gel Filtration Chromatography (GFC).
  • GFC Gel Filtration Chromatography
  • the flow of the mobile phase (0.1M NaNO 3 ) was 0.5 ml/min.
  • the GFC chromatogram is shown in FIG. 8 .
  • a twenty gallon jacketed stainless steel pressure reactor was washed two times with 95 kg of deionized water at 95° C. The wash water was removed and the reactor was dried overnight by passing steam through the reactor jacket and applying reduced pressure (3-5 mm Hg).
  • the reactor was filled with 25 kg of anhydrous toluene and a part of the solvent was distilled off under reduced pressure. The residual toluene was then discharged out and the reactor was kept under reduced pressure.
  • the reactor was cooled to room temperature, filled with anhydrous toluene (15 L) and pentaerythritol (1,020 g) was added. Part of the solvent ( ⁇ 8 L) was distilled off under reduced pressure, and then the reactor was cooled to 30° C. under dry nitrogen atmosphere.
  • Liquid sodium-potassium alloy Na 22%, K 78%; 2.2 g was added to the reactor.
  • Anhydrous ethylene oxide 14,080 g was continuously added over three hours keeping the reaction temperature at 150-155° C.
  • the contents of the reactor were heated for 30 min at ⁇ 150° C., and then the temperature was lowered to ⁇ 70° C.
  • Excess ethylene oxide and toluene were distilled off under reduced pressure. After distillation, the contents of the reactor remained under reduced pressure and a nitrogen sparge was performed to remove traces of ethylene oxide. Finally the product was drained from the reactor giving 14,200 g of viscous liquid.
  • GFC Gel Filtration Chromatography
  • a twenty gallon jacketed stainless steel pressure reactor was washed two times with 95 kg of deionized water at 95° C. Water was discharged out and the reactor was dried overnight by passing steam through the reactor jacket and applying reduced pressure 3-5 mm Hg.
  • the reactor was filled with 25 kg of toluene and a part of the solvent was distilled off under reduced pressure. The residual toluene was then discharged out and the reactor was kept under reduced pressure. Next the reactor was cooled to room temperature, filled with anhydrous toluene (21 L) and previously isolated alkoxylatable oligomer: pentaerythritol based 4ARM-PEG-2K from the Example 10 (2,064 g) was added.
  • Part of the solvent (16 L) was distilled off under reduced pressure, and then the reactor was cooled to 30° C. under dry nitrogen atmosphere.
  • Four liter of molecular sieves-dried toluene (water content ⁇ 5 ppm) and liquid sodium-potassium alloy (Na 22%, K 78%; 1.7 g) were added, and the reactor was warmed to 110° C.
  • ethylene oxide (19,300 g) was continuously added over five hours keeping the reaction temperature at 145-150 T.
  • the contents of the reactor were heated for 30 min at ⁇ 140° C., and then the temperature was lowered to 100° C.
  • Glacial acidic acid 100 g was added to neutralize the catalyst.

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US10058554B2 (en) 2005-09-30 2018-08-28 Indivior Uk Limited Sustained release small molecule drug formulation
US10376590B2 (en) 2007-05-25 2019-08-13 Indivior Uk Limited Sustained delivery formulations of risperidone compound
US11712475B2 (en) 2007-05-25 2023-08-01 Indivior Uk Limited Sustained delivery formulations of risperidone compound
US10010612B2 (en) 2007-05-25 2018-07-03 Indivior Uk Limited Sustained delivery formulations of risperidone compounds
US11013809B2 (en) 2007-05-25 2021-05-25 Indivior Uk Limited Sustained delivery formulations of risperidone compound
US9320808B2 (en) 2009-11-18 2016-04-26 Nektar Therapeutics Acid salt forms of polymer-drug conjugates and alkoxylation methods
US11834553B2 (en) 2009-11-18 2023-12-05 Nektar Therapeutics Alkoxylation methods
US10592168B1 (en) 2010-06-08 2020-03-17 Indivior Uk Limited Injectable flowable composition comprising buprenorphine
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US10172849B2 (en) 2010-06-08 2019-01-08 Indivior Uk Limited Compositions comprising buprenorphine
US10198218B2 (en) 2010-06-08 2019-02-05 Indivior Uk Limited Injectable flowable composition comprising buprenorphine
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US10111955B2 (en) 2014-12-04 2018-10-30 Delta-Fly Pharma, Inc. PEG derivative
US10548984B2 (en) * 2015-02-04 2020-02-04 United Arab Emirates University RVG Derived peptides
US20180028675A1 (en) * 2015-02-04 2018-02-01 United Arab Emirates University Rvg derived peptides
CN110256533A (zh) * 2018-03-12 2019-09-20 博瑞生物医药（苏州）股份有限公司 一种高纯度的多臂抗癌偶联物
US11253603B2 (en) 2018-09-17 2022-02-22 The Children's Hospital Of Philadelphia Polymer-based macromolecular prodrugs
US11642414B2 (en) 2018-09-17 2023-05-09 The Children's Hospital Of Philadelphia Polymer-based macromolecular prodrugs

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