Potent conjugates and hydrophilic linkers

Abstract

Linkers for binding drugs to cell binding agents are modified to hydrophilic linkers by incorporating a polyethylene glycol spacer. The potency or the efficacy of the cell-binding agent-drug conjugates is surprisingly enhanced several folds in a variety of cancer cell types, including those expressing a low number of antigens on the cell surface or cancer cells that are resistant to treatment. A method for preparing maytansinoids bearing a thioether moiety and a reactive group which allows the maytansinoid to be linked to a cell-binding agent in essentially a single step is also provided.

Description

[0001]This is a continuation of U.S. application Ser. No. 12 / 574,466 filed Oct. 6, 2009.FIELD OF THE INVENTION[0002]The present invention relates to new linkers to link drugs (e.g. cytotoxic agents) to cell-binding agents (e.g., antibodies) in such a way that the linker contributes in increasing the activity of the drug. In particular, the present invention relates to the use of novel hydrophilic linkers, wherein such linkers enhance the potency or the efficacy of the cell-binding agent-drug conjugates by several fold in a variety of cancer cell types, including those expressing a low number of antigens on the cell surface or cancers that are resistant to treatment. The present invention also relates to a method for preparing maytansinoids bearing a thioether moiety and a reactive group which allows the maytansinoid to be linked to a cell-binding agent.BACKGROUND OF THE INVENTION[0003]Antibody conjugates of cytotoxic drugs are being developed as target-specific therapeutic agents. A...

AI Technical Summary

Benefits of technology

[0008]The present invention addresses the problem of resistance by designing new linkers to link drugs to cell-binding agents in such a way that the linker contributes in increasing the activity of the drug. Thus, the present invention improves the manner in which drugs are linked to a cell-binding agent such that the linker design provides conjugates that are active across a broad spectrum of tumors, particularly in low antigen expressing or drug resistant tumors.

[0009]The present invention is based on the novel finding that when traditional linkers (e.g. SMCC, STAB etc, described in U.S. Patent Publication No. 20050169933) are modified to hydrophilic linkers by incorporating a polyethylene glycol [PEGn, (—CH2CH2O)n)] spacer, the potency or the efficacy of the cell-binding agent-drug conjugates is surprisingly enhanced several fold in a variety of cancer cell types, including those expressing a low number of antigens on the cell surface.

[0010]Also, these PEG-containing conjugates unexpectedly are more potent than the previously described conjugates toward cell lines that are resistant to treatment.

[0011]In addition, in the case of antibody conjugates, incorporation of hydrophilic linkers allowed the conjugation of up to 15 molecules of a drug per antibody molecule with high yield and no aggregation or precipitation. These conjugates with hydrophilic linkers with up to 15 molecules of a drug linked per antibody molecule bound with high affinity to target antigen (similar to that of unmodified antibody).

Problems solved by technology

Although, antibody-cytotoxic drug conjugates show cell killing activity in vitro and anti-tumor activity in vivo, their potency is diminished in many cases, especially when the antigen expression on the target cancer cell is low, or when the target cells are resistant to the treatment.

This is often the case in the clinical setting, resulting in low to modest anti-tumor activity in patients.

However, this process is cumbersome and several analogs have to be synthesized, and often modification in the structure of the drug results in loss of biological activity.

These multiple reaction and purification steps result in low yield of the final conjugate and can be expensive and cumbersome when one considers implementing these steps on a large scale.

An additional drawback to these methods is the conjugate heterogeneity that is introduced when unreacted crosslinker remains linked to the cell-binding agent without attached drug.

Images