Acid Salt Forms of Polymer-Drug Conjugates and Alkoxylation Methods
Among other aspects, provided herein is a mixed-acid salt of a water-soluble polymer-drug conjugate, along with related methods of making and using the same. The mixed-salt acid salt is stably formed, and appears to be more resistant to hydrolytic degradation than the corresponding predominantly pure acid salt or free base forms of the polymer-drug conjugate. The mixed acid salt is reproducibly prepared and recovered, and provides surprising advantages over non-mixed acid salt forms of the water-soluble polymer drug conjugate.
1 . A composition comprising mixed salts of water-soluble polymer-active agent conjugates, wherein the active agent in the conjugate has at least one basic amine group, and further wherein for each amine group within the active agent, the amine group is either protonated or unprotonated, where any given protonated amine group is an acid salt form of an inorganic acid or trifluoroacetic acid (TFA).
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4 . The composition of claim 1 , where the inorganic acid is hydrochloric acid.
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7 . The composition of claim 1 , wherein said water soluble polymer is a poly(ethylene glycol).
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10 . The composition of claim 1 , wherein the water-soluble polymer-active agent conjugate corresponds to structure (I):
and n is an integer ranging from about 20 to about 500.
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14 . The composition of claim 4 , wherein about 25-40 mole percent of the amine groups within the active agent are protonated as the HCl salt, and about 5-35 mole percent of the amine group within the active agent are non-protonated (i.e., as the free base).
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17 . A method for preparing 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) to form a deprotected inorganic acid/TFA mixed salt,
(ii) coupling the deprotected inorganic acid/TFA mixed 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 said polymer active agent conjugate, said polymer-active agent conjugate characterized by having said one or more amino groups present in a combination of free base, inorganic acid salt, and TFA salt form.
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21 . The method of claim 17 , wherein the reagent is an activated polyethylene glycol ester.
22 . The method of claim 21 , wherein the polyethylene glycol reagent is a branched reagent having three or more polymer arms.
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25 . The method of claim 17 , wherein the base is an amine.
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32 . The method of claim 17 , wherein the active agent is a camptothecin is selected from camptothecin, irinotecan, SN-38.
33 . The method of claim 32 , wherein the amine-containing active agent in protected form is t-boc-glycine irinotecan.
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39 . A mixed salt reproducibly prepared by the method of claim 17 , possessing relative molar amounts of inorganic acid addition salt, trifluoroacetic acid salt and free base that vary by no more than about fifteen percent in consistency from batch to batch.
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46 . A pharmaceutically acceptable composition comprising (i) a mixed salt of claim 1 or prepared by the method of claim 17 , and (ii) lactate buffer, in lyophilized form.
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51 . A method comprising the step of 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.
52 . The method of claim 51 , wherein the previously isolated alkoxylatable oligomer has a known and defined weight-average molecular weight of greater than 500 Daltons.
53 . The method of claim 51 , wherein both the previously isolated alkoxylatable oligomer and the alkoxylated polymeric product are soluble in the suitable solvent.
54 . The method of claim 51 , wherein the previously isolated alkoxylatable oligomer is prepared by (a) alkoxylating a precursor molecule having a molecular weight of less than 300 Daltons to form a reaction mixture comprising an alkoxylatable oligomer, and (b) isolating the alkoxylatable oligomer from the reaction mixture.
55 . The method of claim 51 , wherein the alkoxylation utilizes ethylene oxide as an alkoxylation agent.
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66 . The method of claim 51 , wherein the previously isolated alkoxylatable oligomer has the following structure:
wherein the average value of n within the structure is from 2 to 50.
67 . The method of claim 51 , wherein the alkoxylated polymeric material has the following structure:
wherein the average value of all the instances of n within the structure is from 10 to 1000.
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79 . The method of claim 51 , wherein the suitable solvent is toluene used in quantities that after ethoxylation the solvent consists more than 25 wt % and less than 75 wt % of the reaction mixture.
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90 . The method of claim 51 , wherein the step of alkoxylating is carried out under alkoxylating conditions wherein the amount of water present is less than 14 ppm.
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93 . A composition comprising the alkoxylated polymeric product prepared in accordance with the method of claim 51 .
94 . The composition of claim 51 , wherein the purity of the alkoxylated polymeric product is greater than 92 wt % and the total content of high molecular weight impurities and diols is less than 8 wt %.
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96 . The method of claim 51 , further comprising the step of modifying the alkoxylated polymeric material to bear a reactive group to thereby form a water-soluble polymer reagent.
97 . The method of claim 96 , wherein the water-soluble polymer reagent has the following structure:
wherein each n is from about 40 to about 500.
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100 . A composition comprising mixed salts of four-arm polymer conjugates, wherein at least 90% of the four-arm conjugates in the composition:
(i) have a structure encompassed by the formula,
C—[CH 2 —O—(CH 2 CH 2 O) n —CH 2 —C(O)—Term] 4 ,
wherein
n, in each instance, is an integer having a value from 5 to 150 (e.g., about 113), and
Term, in each instance, is selected from the group consisting of —OH, —OCH 3 ,
—NH—CH 2 —C(O)—OH, —NH—CH 2 —C(O)—OCH 3 ,
and —NH—CH 2 —C(O)—O-Irino (“GLY-Irino”), wherein Irino is a residue of irinotecan; and
(ii) for each Term in the at least 90% of the four-arm conjugates in the composition, at least 90% thereof are —NH—CH 2 —C(O)—O-Irino,
and further wherein for each amino group within each Irino in the at least 90% of the four-arm conjugates in the composition, each amino group is either protonated or unprotonated, where any given protonated amino group is an acid salt form of an inorganic acid or trifluoroacetic acid.