Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Carbohydrate doai
Reexamination Certificate
2001-12-21
2004-04-06
Peselev, Elli (Department: 1623)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Carbohydrate doai
C514S229800, C514S449000, C530S391700, C536S006400, C540S462000, C549S510000
Reexamination Certificate
active
06716821
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to cytotoxic agents bearing reactive polyethylene glycol linkers and methods for making such agents. These agents may be used in the production of cytotoxic conjugates, or for other purposes, such as in an affinity resin for use in the isolation of cellular components that recognize and bind the cytotoxic agents.
The present invention also relates to novel cytotoxic conjugates comprising polyethylene glycol linkers, methods of making the conjugates, and their therapeutic use. More specifically, the invention relates to novel cytotoxic conjugates comprising cytotoxic agents joined to cell-binding agents using hetero-bifunctional polyethylene glycol linkers, methods for making the conjugates and their therapeutic use. These novel cytotoxic conjugates have therapeutic use in that the cytotoxic portion of the conjugates can be delivered to specific cell populations in a targeted fashion, due to the linkage of the cytotoxic agent to a cell-binding agent.
BACKGROUND OF THE INVENTION
Conjugates of highly cytotoxic agents, such as maytansinoids and CC-1065 analogs, and cell-binding agents have been shown to possess exceptional target-specific anti-tumor activity (U.S. Pat. Nos. 5,208,020, 5,416,064, 5,475,092, 5,585,499, and 5,846,545). In such cytotoxic conjugates, the cytotoxic agent is bound to the cell-binding agent via a disulfide bond or via a short disulfide-containing linker. It has been previously shown that such disulfide-containing linkers are both stable upon storage, and efficiently cleaved inside a tumor cell to release fully active drug (Liu et al.,
Proc. Natl. Acad. Sci
. 93:8618-8623 (1996); Chari et al.,
Cancer Res
. 55:4079-4084 (1995); Chari, R. V. J.,
Adv. Drug Delivery Rev
. 31:89-104 (1998)). Cleavage likely occurs via disulfide exchange between the disulfide-linked cytotoxic agent and an intracellular thiol, such as glutathione.
However, because most highly-potent cytotoxic agents used in cytotoxic conjugates are hydrophobic, two technical difficulties arise. The first is that conjugation reactions between cytotoxic agents and cell-binding agents require reaction conditions that address the hydrophobic nature of the cytotoxic agents. These conditions include very dilute solutions, the use of large volumes, and the presence of large amounts of non-aqueous co-solvents, which may damage the proteinacious cell-binding agents. As a result, preparation and purification processes become quite cumbersome, and the final cytotoxic conjugate is obtained in low concentration, necessitating the administration of large volumes to patients.
The second technical difficulty is that cytotoxic conjugates prepared using disulfide bonds or short disulfide-containing linkers are only sparingly soluble in pharmaceutical solutions typically used for parenteral administration to patients. It is therefore difficult to produce formulations for such conjugates.
Thus, in order to develop improved methods for producing cytotoxic conjugates, and increase the flexibility in formulating pharmaceutical solutions containing the conjugates, there is a need to address the hydrophobicity of both the cytotoxic agents and the cytotoxic conjugates produced using cytotoxic agents.
One manner in which to meet both of these goals would be to develop novel linker molecules that allow the hydrophobic cytotoxic agents to be manipulated under aqueous conditions and permit the formation of a cytotoxic conjugate that is soluble under both aqueous and non-aqueous conditions.
Polyethylene glycol (PEG) has been found to be useful in the conversion of cytotoxic drugs into prodrugs, thereby extending the half-life of the drugs in circulation in vivo, and improving their water solubility (for a review see Greenwald, R. B.,
J. Controlled Release
74:159-171 (2001)). For example, the anti-cancer drug Taxol has been converted into the prodrug PEG-Taxol by linking PEG via an ester bond to the C-2′ position of Taxol (U.S. Pat. No. 5,824,701; Greenwald et al.,
J. Med. Chem
. 39:424-431 (1996); Greenwald et al.,
J. Org. Chem.
60:331-336 (1995)).
However, PEG used in such applications is usually very large (average molecular weight of 40,000). Such size is required to significantly alter the pharmacokinetics of the drug. The drug molecules are also typically reacted with PEG via an ester or carbamate group of the drug, which can result in a drastic decrease in drug potency. In addition, the PEG moiety must be cleaved in vivo by some enzymatic mechanism to restore the activity of the drug, a process which is often inefficient. Finally, PEG used in such applications is typically mono-functional, i.e., only one terminus of the PEG molecule is modified so that it can be linked to the drug.
The present inventors have prepared novel PEG linking groups that provide a solution to both of the difficulties discussed above. These novel PEG linking groups are soluble both in water and in non-aqueous solvents, and can be used to join one or more cytotoxic agents to a cell-binding agent. The PEG linking groups are hetero-bifunctional linkers in that they bind to cytotoxic agents and cell-binding agents at opposite ends of the linkers through a functional sulfhydryl or disulfide group at one end, and an active ester at the other end. The linking groups have the two-fold advantage over other linking groups in that (1) they can be chemically joined to a cytotoxic agent in a non-aqueous solvent via a disulfide bond, thereby surmounting the hydrophobic nature of the agent and making it soluble in both non-aqueous and aqueous solvents, and (2) cytotoxic conjugates produced using the linking groups have greater solubility in water, thereby permitting much greater flexibility in the formulation of pharmaceutical solutions for parenteral administration to patients.
Thus, herein disclosed are cytotoxic agents bearing a PEG linking group having a terminal active ester, and cytotoxic conjugates comprising one or more cytotoxic agents joined to a cell-binding agent via a PEG linking group. In addition, a therapeutic composition comprising a cytotoxic conjugate is disclosed.
Also disclosed are methods of preparing cytotoxic agents bearing a PEG linking group having a terminal active ester, and methods of preparing cytotoxic conjugates comprising one or more cytotoxic agents joined to a cell-binding agent via a PEG linking group. Finally, a method for killing selected cell populations using cytotoxic conjugates is disclosed.
SUMMARY OF THE INVENTION
In one embodiment of the invention, cytotoxic agents bearing a polyethylene glycol (PEG) linking group having a terminal active ester are disclosed. The cytotoxic agents contemplated in this, and each proceeding embodiment, include a thiol-containing maytansinoid, thiol-containing taxane, thiol-containing CC-1065 analogue, thiol-containing daunorubicin analogue and thiol-containing doxorubicin analogue, and thiol-containing analogues or derivatives thereof. The core of the terminal active esters of the PEG linking group contemplated in this, and each proceeding embodiment, are esters that readily react with amino groups, including N-succinimidyl, N-sulfosuccinimidyl, N-phthalimidyl, N-sulfophthalimidyl, 2-nitrophenyl, 4-nitrophenyl, 2,4-dinitrophenyl, 3-sulfonyl-4-nitrophenyl or 3-carboxy-4-nitrophenyl esters.
In a preferred embodiment, the PEG linking group has from 1 to 20 monomeric units. In an equally preferred embodiment, the PEG linking group has from 21 to 40 monomeric units. In a further equally preferred embodiment, the PEG linking group has from 41 to 1000 monomeric units.
Specifically contemplated is a cytotoxic agent, bearing a polyethylene glycol (PEG) linking group having a terminal active ester and 1 to 20 monomeric units, of formula 2:
wherein Z is said cytotoxic agent;
wherein Q is R
2
COO—, R
2
R
3
NCOO—, R
2
OCOO—, R
2
O—, R
2
CONR
3
—, R
2
R
3
N—, R
2
OCONR
3
—, or S—,
wherein:
R
2
is SCR
4
R
5
R
6
—,
R
4
, R
5
and R
6
are each H, linear alkyl, cyclic alkyl or branched alkyl, and may be the same or different,
R
Chari Ravi V. J.
Miller Michael Louis
Widdison Wayne Charles
Zhao Robert Yongxin
Immunogen Inc.
Peselev Elli
LandOfFree
Cytotoxic agents bearing a reactive polyethylene glycol... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cytotoxic agents bearing a reactive polyethylene glycol..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cytotoxic agents bearing a reactive polyethylene glycol... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3242048