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Nektar Therapeutics : Patent Issued for N-Maleimidyl Polymer Derivatives

07/09/2014 | 06:45pm US/Eastern
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By a News Reporter-Staff News Editor at Life Science Weekly -- A patent by the inventor Shen, Xiaoming (Millbrae, CA), filed on May 9, 2013, was published online on July 1, 2014, according to news reporting originating from Alexandria, Virginia, by NewsRx correspondents (see also Nektar Therapeutics).

Patent number 8765111 is assigned to Nektar Therapeutics (San Francisco, CA).

The following quote was obtained by the news editors from the background information supplied by the inventors: "Covalent attachment of the hydrophilic polymer poly(ethylene glycol), abbreviated PEG, also known as poly(ethylene oxide), abbreviated PEO, to molecules and surfaces is of considerable utility in biotechnology and medicine. In its most common form, PEG is a linear polymer terminated at each end with hydroxyl groups: HO--CH.sub.2CH.sub.2O--(CH.sub.2CH.sub.2O).sub.n--CH.sub.2CH.sub.2--OH

"The above polymer, alpha-,omega-dihydroxylpoly(ethylene glycol), can be represented in brief form as HO-PEG-OH where it is understood that the -PEG- symbol represents the following structural unit: --CH.sub.2CH.sub.2O--(CH.sub.2CH.sub.2O).sub.n--CH.sub.2CH.sub.2-- where n typically ranges from about 3 to about 4000.

"PEG is commonly used as 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 that is subject to ready chemical modification. The structure of mPEG is given below. CH.sub.3O--(CH.sub.2CH.sub.2O).sub.n--CH.sub.2CH.sub.2--OH

"Random or block copolymers of ethylene oxide and propylene oxide, shown below, are closely related to PEG in their chemistry, and they can be substituted for PEG in many of its applications. HO--CH.sub.2CHRO(CH.sub.2CHRO).sub.nCH.sub.2CHR--OH wherein each R is independently H or CH.sub.3.

"PEG is a polymer having the properties of solubility in water and in many organic solvents, lack of toxicity, and lack of immunogenicity. One use of PEG is to covalently attach the polymer to insoluble molecules to make the resulting PEG-molecule 'conjugate' soluble. For example, it has been shown that the water-insoluble drug paclitaxel, when coupled to PEG, becomes water-soluble. Greenwald, et al, J. Org. Chem., 60:331-336 (1995).

"To couple PEG to a molecule, such as a protein, it is often necessary to 'activate' the PEG by preparing a derivative of the PEG having a functional group of terminus thereof. The functional group is chosen based on the type of available reactive group on the molecule that will be coupled to the PEG. For example, the functional group could be chosen to react with an amino group on a protein in order to form a PEG-protein conjugate. There is a continuing need in the art for new activated PEG derivatives useful for coupling to biologically active molecules."

In addition to the background information obtained for this patent, NewsRx journalists also obtained the inventor's summary information for this patent: "The invention provides multi-functional N-maleimidyl polymer derivatives, such as bifunctional and multi-arm N-maleimidyl PEG derivatives, and methods for preparing such derivatives. The derivatives of the invention have no linking group between the terminus of the polymer backbone and the nitrogen atom of the maleimidyl moiety. The absence of a linker minimizes structural complexity of the derivative and simplifies synthesis of the derivative. Further, the 'linkerless' derivatives of the invention typically cost less to produce and exhibit reduced likelihood of degradation in vivo. Such maleimidyl-activated polymers are suitable for coupling to other molecules bearing thiol groups, including, but not limited to, proteins having one or more cysteine thiol groups.

"The invention provides a multi-functional N-maleimidyl polymer derivative comprising a water soluble and non-peptidic polymer backbone having an average molecular weight from about 800 Da to about 100,000 Da, the polymer backbone having a first terminus bonded to a first functional group and a second terminus having a terminal carbon, wherein said terminal carbon of said second terminus is directly bonded to a N-maleimidyl moiety having the structure:

"##STR00001## wherein L is the point of bonding to the terminal carbon of the second terminus of the polymer backbone. The second functional group may be a second maleimidyl moiety or any other functional group known in the art that will not react with a maleimidyl group. The polymer backbone has two or more termini 'activated' with a functional group such as a maleimidyl group.

"The polymer backbone is preferably a poly(alkylene glycol), copolymer thereof, terpolymer thereof, or mixture thereof. Examples include poly(ethylene glycol), poly(propylene glycol), and copolymers of ethylene glycol and propylene glycol. As explained in greater detail below, preferred embodiments of the invention utilize PEG polymers, such as bifunctional PEG, multiarmed PEG, forked PEG, branched PEG, pendent PEG, and PEG with degradable linkages therein.

"The invention provides two methods of preparing the linkerless N-maleimidyl polymer derivatives. In one method, a water-soluble and non-peptidic polymer backbone having an average molecular weight from about 800 Da to about 100,000 Da, the polymer backbone having a first terminus bonded to a first functional group and a second terminus bonded to an amine group, is reacted with maleic anhydride to form an open ring intermediate. The open ring intermediate is heated in the presence of acetic anhydride and a salt of acetic acid, such as sodium or potassium acetate, to form a multi-functional N-maleimidyl polymer derivative product. In a second method, an N-alkoxycarbonylmaleimide is reacted with the water-soluble and non-peptidic polymer backbone having an average molecular weight of about 800 Da to about 100,000 Da and a terminal amine group to form the N-maleimidyl polymer derivative product in a single step. In one embodiment, the polymer backbone used in either reaction method is X-PEG-NH.sub.2, wherein PEG is poly(ethylene glycol) and X is a second functional group.

"Using either method, the N-maleimidyl polymer derivative product can be purified prior to use. For example, ion exchange chromatography and precipitation techniques can be employed to purify the final product. The N-maleimidyl polymer derivative product can be reacted with a biologically active agent to form a biologically active polymer conjugate. As noted above, the N-maleimidyl polymer derivatives are particularly suited for reaction with thiol groups, such as thiol groups on proteins or peptides."

URL and more information on this patent, see: Shen, Xiaoming. N-Maleimidyl Polymer Derivatives. U.S. Patent Number 8765111, filed May 9, 2013, and published online on July 1, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8765111.PN.&OS=PN/8765111RS=PN/8765111

Keywords for this news article include: Alkenes, Ethylene Glycols, Nektar Therapeutics.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC

(c) 2014 NewsRx LLC

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