Exhibit 10.3


                                                                                        
Exhibit
      10.3

     

                                                                                         Execution
      Copy


     

    AMENDMENT
      NO. 1 TO
      COLLABORATIVE DEVELOPMENT 

    AND
      LICENSE
      AGREEMENT

    


    This
      Amendment No. 1 (this
      "Amendment No. 1") to the Collaborative
      Development and License Agreement (this
“Agreement”)
      entered into as of July 7, 2006 (the "Agreement Effective Date") by and between
      ImmunoGen,
      Inc., a Massachusetts corporation with its principal place of business at 128
      Sidney Street, Cambridge, Massachusetts, USA 02139 (“ImmunoGen”) and Biotest AG,
      a corporation organized under the laws of Germany having an address of
      Landsteinerstraße 5, D-63303 Dreieich, Germany (“Biotest”) is dated
      as of August 23,
      2006 (the “Amendment Effective Date”). 

    


    Capitalized
      terms used but
      not otherwise defined herein shall have the meanings ascribed to such terms
      in
      the Agreement.

    


    WHEREAS,
      on the Agreement
      Effective Date, ImmunoGen and Biotest entered into the Agreement for the purpose
      of Developing
      and Commercializing Licensed Products derived from the conjugation of Biotest’s
      proprietary [***] Antibodies with ImmunoGen’s maytansine derivatives; and

    


    WHEREAS,
      the Parties
      hereto desire to amend the Agreement as set forth herein.

    


    NOW,
      THEREFORE, in
      consideration of the mutual covenants contained herein, and for other good
      and
      valuable consideration, the Parties hereto, intending to be legally bound,
      hereby agree as follows:

    


    1. The
      introduction of
      Section 6.4.1 of the Agreement and Sections 6.4.1(a) and 6.4.1(b) of the
      Agreement are hereby deleted in their entirety and replaced with the
      following:

     

    


     

    “6.4.1
      Payment
      of Royalties.
      Biotest shall pay
      ImmunoGen a royalty based on Annual Net Sales of each Royalty-Bearing Product
      commencing with the Calendar Year (or partial Calendar Year) in which the First
      Commercial Sale of such Royalty-Bearing Product occurs and ending upon
      expiration of the Royalty Term for such Royalty-Bearing Product, at the
      following rates; provided, that, for the purpose of clarity, to the extent
      a
      Royalty-Bearing Product is not covered by a Valid Claim in a country in the
      Territory, the Net Sales of such Royalty-Bearing Product in such country shall
      not be included in the calculation of Annual Net Sales used to determine the
      royalty rates in Sections 6.4.1(a) and 6.4.1(b) on and after [***] ([***])
      years
      from the date of First Commercial Sale of such Royalty-Bearing Product in such
      country:

     

     

    
      
        1

        Portions
          of this Exhibit were omitted and have been filed separately with the Secretary
          of the Commission pursuant to the Company’s application requesting confidential
          treatment under Rule 24b-2 of the Securities Exchange Act of
          1934.

        
        

      

      
        
        

        
          

        

      

      
        
        

      

    


    


     

    (a) Biotest
      Products

     

    


    
      	
              Annual
                Net Sales of 

              Biotest
                Products Worldwide

               

            	 	
               

              Royalty
                Rate

            
	
              Up
                to $[***]

               

            	 	
              [***]%

            
	
              Equal
                to or greater than $[***]

            	 	
              [***]%

            


    

    


    


    (b)
       Co-Developed
      Products

     

    (i)
      Early Stage Co-Developed Products

     

    
      	
              Annual
                Net Sales Outside 

              Co-Development
                Territory

               

            	 	
               

              Royalty
                Rate

            
	
              Up
                to $[***]

               

            	 	
              [***]%

            
	
              Equal
                to or greater than $[***]

            	 	
              [***]%

            


    

    


    (ii)
      Late Stage Co-Developed Products

     

    
      	
              Annual
                Net Sales Outside 

              Co-Development
                Territory

               

            	 	
               

              Royalty
                Rate

            
	
              Up
                to $[***]

               

            	 	
              [***]%

            
	
              Equal
                to or greater than $[***]

            	 	
              [***]%”

            


    

     

    


    2. The
      Parties hereby confirm
      and agree that, except as amended hereby, the Agreement remains in full force
      and effect and is a binding obligation of the Parties hereto. This Amendment
      No.
      1 may be executed simultaneously in counterparts, each of which shall be deemed
      an original.

    


    


    IN
      WITNESS WHEREOF, the
      Parties have caused this Amendment to be executed by their duly authorized
      representatives.

     

     

    
       

       

      
        	 IMMUNOGEN, INC.	 	 Biotest AG
	 	 	 	 	 
	 By: 	 	 	 By:	 
	 Name:	 	 	 Name:	 Dr. Martin
                Reinecke
	 Title:	 	 	 Title:	 VP,
                Strategic Alliances
	 	                                 	 	 	 
	 	 	 	 	 
	 	 	 	 By:	 
	 	 	 	 Name:	 Prof. Dr.
                Gregor Schulz
	 	 	 	 Title:	 Chief
                Executive Officer
	 	 	 	 	 


      




    
      
        
          2

          Portions
            of this Exhibit were omitted and have been filed separately with the
            Secretary
            of the Commission pursuant to the Company’s application requesting confidential
            treatment under Rule 24b-2 of the Securities Exchange Act of
            1934.