Bispecific antibodies binding ALK-1 and BMPR-2

Abstract

The present invention relates to bispecific antibodies binding human ALK-1 and human BMPR-2. Also provided are BsABs which are agonists of ALK-1/BMPR-2 signaling, and BsABs which do not trigger osteogenic signaling. Furthermore, the invention relates to pharmaceutical uses of the BsABs, in particular for the treatment of pulmonary hypertension. Also provided are methods to screen for BsABs for use in the therapy, e.g., of pulmonary hypertension.

1 . A bispecific antibody (BsAB), wherein said BsAB comprises two binding domains, wherein the first binding domain is specific for ALK-1 and the second binding domain is specific for BMPR-2. 
     
     
         2 . A BsAB according to  claim 1 , wherein the ALK-1 is human ALK-1 or a fragment thereof, and wherein the BMPR-2 is human BMPR-2 or a fragment thereof. 
     
     
         3 . A BsAB according to  claim 1 , wherein said BsAB has agonistic activity for ALK-1/BMPR-2 signaling in a target cell. 
     
     
         4 . A BsAB according to  claim 3 , wherein said target cell is an endothelial cell. 
     
     
         5 . A BsAB according to  claim 1 , wherein said BsAB promotes dimerization of ALK-1 and BMPR-2. 
     
     
         6 . A BsAB according to  claim 1 , wherein said BsAB promotes dimerization of ALK-1 and BMPR-2, such that an EC50 of the BsAB can be determined in a suitable assay to detect dimerization of ALK-1 and BMPR-2. 
     
     
         7 . A BsAB according to  claim 1 , wherein an effective dose of said BsAB promotes phosphorylation of SMAD1 and/or SMAD5. 
     
     
         8 . A BsAB according to  claim 1 , wherein an effective dose of said BsAB has an anti-apoptotic effect in endothelial cells. 
     
     
         9 . A BsAB according to  claim 1 , wherein an effective dose of said BsAB reduces the apoptosis of endothelial cells observed upon starvation of the cells. 
     
     
         10 . A BsAB according to  claim 1 , wherein an effective dose of said BsAB reduces the apoptosis of endothelial cells treated with an effective dose of TNFα and/or cycloheximide (CHX). 
     
     
         11 . A BsAB according to  claim 1 , wherein the BsAB binds ALK-2 or an antigen according to SEQ ID 117 with an affinity that is lower or equal to the binding affinity of the BsAB for bovine serum albumin. 
     
     
         12 . A BsAB according to  claim 1 , wherein an EC50 of said BsAB has a lower osteogenic activity than an EC50 of rhBMP-9. 
     
     
         13 . A BsAB according to  claim 1 , wherein C2C12 cells treated with the EC50 of rhBMP-9 have a higher alkaline phosphatase (ALP) activity than C2C12 cells treated with the same concentration of BsAB. 
     
     
         14 . A BsAB according to  claim 1 , wherein said BsAB has no osteogenic activity in C2C12 cells. 
     
     
         15 . A BsAB according to  claim 1  for use as a medicament. 
     
     
         16 . A BsAB according to  claim 1  for use in the treatment of pulmonary hypertension. 
     
     
         17 . A method to test the suitability of a BsAB for use in therapy comprising
 (i) analyzing the ability of the BsAB to promote dimerization of ALK-1 and BMPR-2, and   (ii) optionally comparing the binding affinities of the BsAB for ALK-2 and BSA, and   (iii) selecting the BsAB as suitable, where the BsAB at least promotes dimerization of ALK-1 and BMPR-2 as determined according to step (i) and optionally binds ALK-2 with an affinity that is lower or equal to the BsABs affinity for BSA, as determined according to step (ii).   
     
     
         18 . A method to test the suitability of a BsAB for use in therapy comprising
 (i) analyzing the ability of the BsAB to promote dimerization of ALK-1 and BMPR-2, and   (ii) optionally analyzing the ability of the BsAB to promote dimerization of ALK-2 and BMPR-2, and   (iii) selecting the BsAB as suitable, where the BsAB at least promotes dimerization of ALK-1 and BMPR-2 as determined according to step (i) and optionally does not promote dimerization of ALK-2 and BMPR-2 as determined according to step (ii).