Inhibitors of human ezh2, and methods of use thereof

Abstract

The invention relates to inhibition of wild-type and certain mutant forms of human histone methyltransferase EZH2, the catalytic subunit of the PRC2 complex which catalyzes the mono- through tri-methylation of lysine 27 on histone H3 (H3-K27). In one embodiment the inhibition is selective for the mutant form of the EZH2, such that trimethylation of H3-K27, which is associated with certain cancers, is inhibited. The methods can be used to treat cancers including follicular lymphoma and diffuse large B-cell lymphoma (DLBCL). Also provided are methods for identifying small molecule selective inhibitors of the mutant forms of EZH2 and also methods for determining responsiveness to an EZH2 inhibitor in a subject.

1 .- 20 . (canceled) 
     
     
         21 . A method comprising
 detecting the presence of a mutation in the EZH2 SET domain of SEQ ID NO: 6, in a sample from a subject in need thereof, wherein said detecting comprises screening, at amino acid position Y641, of SEQ ID NO: 1 or at a corresponding amino acid position in isoform a (SEQ ID NO: 3), or isoform b (SEQ ID NO: 5), for the presence of at least one mutation, wherein the mutation at amino acid position Y641 is selected from the group consisting of a substitution of phenylalanine (F) for the wild type residue tyrosine (Y) at amino acid position 641 of SEQ ID NO: 1 (Y641F); a substitution of histidine (H) for the wild type residue tyrosine (Y) at amino acid position 641 of SEQ ID NO: 1 (Y641H); a substitution of asparagine (N) for the wild type residue tyrosine (Y) at amino acid position 641 of SEQ ID NO: 1 (Y641N); a substitution of serine (S) for the wild type residue tyrosine (Y) at amino acid position 641 of SEQ ID NO: 1 (Y641S); and a substitution of cysteine (C) for the wild type residue tyrosine (Y) at amino acid position 641 of SEQ ID NO: 1 (Y641C), and wherein the mutation increases EZH2 trimethylation of Lys27 of histone H3 (H3-K27); and   identifying the subject as a candidate for treatment with an EZH2 inhibitor based on the presence of a detected EZH2 mutation;   administering a therapeutically effective amount of an EZH2 inhibitor sufficient to inhibit proliferation of cancer cells in the subject, wherein the EZH2 inhibitor inhibits the conversion of H3-K27 to trimethylated H3-K27.   
     
     
         22 . The method of  claim 21 , wherein said subject has a cancer selected from leukemia, melanoma, and lymphoma, or is at risk of developing a cancer selected from leukemia, melanoma, and lymphoma. 
     
     
         23 . The method of  claim 22 , wherein said lymphoma is selected from the group consisting of Non-Hodgkin's lymphoma, follicular lymphoma and diffuse large B-cell lymphoma (DLBCL) of germinal center B cell-like (GCB) subtype. 
     
     
         24 . The method of  claim 21 , wherein inhibition of EZH2 is selective inhibition. 
     
     
         25 . The method of  claim 21 , wherein the inhibitor of EZH2 inhibits histone methyltransferase activity of wild-type EZH2. 
     
     
         26 . The method  claim 21 , wherein the inhibitor of EZH2 is a small molecule. 
     
     
         27 . The method of  claim 21 , wherein the inhibitor of EZH2 inhibits histone methyltransferase activity of wild-type EZH2. 
     
     
         28 . The method of  claim 26 , wherein the EZH2 inhibitor is 
       
         
           
           
               
               
           
         
       
       or a pharmaceutically acceptable salt thereof.