WE CLAIM:
1. A. hydrohalide salt form of a polymer-active agent conjugate corresponding to structure (1):
o , n°V
VV^ tf H O \\ >^
/ \ /™"N
O vrvU
CD
wherein each n is an integer ranging from about 20 to about 500 and greater than 95 mole percent of irircotecan's basic nitrogen atoms are protonated in hydrohalide (HX) salt form, where X is selected from fluoride, chloride, bromide, and iodide.

2. The hydrohaiide salt as claimed inclaim 1, wherein greater than 96 mole percent of iriootecan's basic nitrogen atoms are protonated in hydrohaiide salt form.
3. The hydrohaiide salt as claimed inclaim 2, wherein greater than 97 mole percent of irinotecan's basic nitrogen atoms are protonated in hydrohaiide salt form.
4. The hydrohaiide salt as claimed in claim 3, wherein greater than 98 mole percent of irinoteean's basic nitrogen atoms are protonated in hydrohaiide salt form.
5. The hydrohaiide salt as claimed in claims 1-4, wherein the hydrohaiide salt is a hydrochloride salt.
6. The hydrochloride salt as claimed in claim 5, wherein the weight average molecular weight of the conjugate is about 23,000 daltons,
7. The hydrochloride salt as claimed in claim 5, wherein ti is an integer ranging from about SO to about 150.
8. The hydrochloride salt as claimed in claim 7, wherein n has an average value in each aim of about 113,
9. A method for preparing a composition comprising a hydrohaiide salt of a polymer-active agent conjugate corresponding to structure (I), the method comprising:

■V-o v^o p N^K, N
) -^
A— \/^~0
(I)
(i) treating glycine-irinotecan hydrohalide, where the amino group of glycine is in protected form, with a molar excess of hydrohalic acid to thereby remove the protecting group to form deprotected glycine-irinotecan hydrohalide,
(is) coupling the deprotected glycine-irinotecan hydrohalide from step (i) with a polymer reagent bearing an active ester in the presence of a base, to form 4-ami-pentaerythritolyl-polyethylene glycol-carboxymethyl-glycine-irinotecan hydrohalide salt, and
(iii) recovering the 4-arm-pentaerythritolyl-polyethylene glycol-carboxymethy!-glycine-irinotecan hydrohalide salt by precipitation.
10. The method as claimed in claim 9, where the recovered 4-arm-pentaerythritolyI-poIyethylene glycol-carboxymethyl-glycine-irinotecan hydrohalide possesses greater than 95 mole percent of irinotecan's basic nitrogen atoms in hydrohalide (HX) salt form.

11. The method as claimed in claim 10, wherein the recovered 4-arm-pentaerythritolyl-poiyethySene glycol-carboxymethyl-glyoine-irinotecan hydrohaiide possesses greater that 96 mole percent of irinotecan's basic nitrogen atoms in hydrohaiide (HX) salt form.
12. The method as claimed in claim 11, wherein the recovered 4-arm-pentaerythritolyl-polyethylene glycol-carboxymethyl-glycine-irinotecan hydrohaiide possesses greater that 97 mole percent of irinotecan's basic nitrogen atoms in hydrohaiide (HX) salt form,
13. The method as claimed in claim 12, wherein the recovered 4-arra-peniaerythriiolyl-polyethylene glycoj-carboxymethyl-glycme-irinoteean hydrohaiide possesses greater that 98 mole percent of irinotecan's basic nitrogen atoms in hydrohaiide (HX) salt form.
14. The method as claimed in claim 9, further comprising (iv) analyzing the recovered 4-arm-pentaerythritolyl-polyethylene glycol-carboxymethyl-giycme-irinotecan hydrohaiide salt for haiide content, and, in the event the halide content is less than 95 mole percent, (v) dissolving
the recovered 4-arm-pentaerythritolyl-polyethylene gjycol-carboxymethyl-gjycine-irinotecan hydrohaiide salt in ethyl acetate, and adding additional hydrohalie acid.
15. The method as claimed in claim 14, wherein the analyzing is by ion chromatography (IC).
16. The method as claimed in claim 14 or claim 15, wherein the hydrohalie acid is added in the form of an ethanol solution.
17. The method as claimed in claim 16, wherein following the adding of additional hydrohalie acid in step (v), die 4-arm-pentaerythntoJyl-poiyethyiene glycol-carboxymethyl-glycine-irinotecan hydrohaiide salt is recovered by precipitation.
18. The method as claimed in claim 17, wherein the precipitation in step (v) is effected by cooling.
19. The method as claimed in claims 9 to 19, wherein the glycine-irinotecan
hydrohaiide in protected form is treated with a ten-fold or greater molar excess of hydrohalie acid to thereby remove the protecting group to form glycine-irinotecan hydrohaiide.

20. The method as claimed in claim 19, wherein the glycine-irinateean hydrohalide in protects
form Is treated with a molar excess of hydrohalic acid in a range of ten-fold to 25-fold to
thereby remove the protecting group to form glycine-irinotecan hydrohalide,
21. The method as claimed in claims 9-20, wherein the glycine-irinotecan hydrohalide in protected form is ter-butyloxycarbonyS(Boe)-g1ycine-irinotecan hydrochloride, where the amino group of glycine is Boc-protected.
22. The method as claimed in claims 9-21, wherein the glycine-irinotecan
hydrohalide in step (i) is glycine-irinotecaTi hydrochloride in protected form, and the glycine-irinotecan hydrochloride in protected form is treated with hydrochloric acid to remove the protecting group.
23. The method as claimed in claim 22, where the glycine-irinotecan hydrochloride in protect* form is treated with a solution of hydrochloric acid in dioxane.
24. The method as claimed in claims 9-23, where step (i) further comprises isolating the glycine-irinotecan hydrohalide prior to step (ii).
25. The method as claimed in claim 24, where the isolating of the glycine-irinotecan hydroha!: prior to step (ii) is by precipitation.
26. The method as claimed in claim 25, where the glycine-irinotecan hydrohalide is precipitate vi a addition of rnethyltertbutylether (MTBE).
27. The method as claimed in claims 9-26, where the base in step (ii) is an amine.
28. The method as claimed in claim 27, where the amine is selected from trimethyl amine, triethyl amine, and dimethylamino-pyridine.
29. The method as claimed in claim 28, where the base is triethylaraine.

30. The method as claimed in claims 9-29, where step (ii) is carried out in a chlorinated solvent.
31. The method as claimed in claims 9-30, where the precipitation in step (iii) comprises addition of methyltertbutyl ether.

32. A composition comprising a hydrohalide salt of 4-arm-pentaerythritoly]-
polyethylene glycol-carboxymethyl-glycine-irmotecan prepared as claimed in claims 9-31,
33. A pharmaceutically acceptable composition comprising the hydrohalide salt as claimed in
claims 1- 8 or 32 and a pharmaceutically acceptable excipient.
34. The pharmaceutically acceptable composition as claimed in claim 33 comprising lactate
buffer, in lyophilized form.
35. The composition as claimed inclaim 34 contained in a single use vial.
36. A sterile composition as claimed in claim 35, wherein the amount of hydrohalide salt contained in the vial is the equivalent of a 100-mg dose of irinotccan.
37. The composition of as claimed in claim 33, wherein the polymer reagent bearing an active ester
is obtainable from a method comprising: alkoxylating in a suitable solvent a previously
isolated alkoxylatable oligomer to form an aikoxyiated polymeric material, wherein the
■previously isolated alkoxylatable oligomer has a known and defined weight-average ...
molecular weight of greater than 300 Daltons; modifying the aikoxyiated polymeric material, in one or more steps, to bear an active ester, thereby forming a polymer reagent bearing an
active ester.

38. The composition as claimed in claim 37, wherein the polymer reagent bearing an active ester
has the following structure:
/
K f >-<,
k V
9 ° 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-Oil, -OGH3,
$ ,-NH-CH2-C(0)-OH,-NH-CH2-C(0)-OCH3,

y~ /o
^-O <* rv\J
i
>-V HO /~i/ D
and -NH-CH2-C(0)-Q-Irino ("GLY-Irino"), wherein Irino is a residue of irinoteean; and
(ii) for each Term in the at least 90% of the four-arm conjugates in the composition, at
least 90% thereof arc -NH.-CH2-C(0)-0-Irino5 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 will either be protonated or unprotonated, where any given protonated amino group is a hydrochloride salt.