Exhibit 10.1

AMENDMENT NO. 1 TO REGISTRATION RIGHTS AGREEMENT

This AMENDMENT NO. 1 TO REGSITRATION RIGHTS AGREEMENT (this “Amendment”) dated
May 14, 2007 and effective as of April 30, 2007, is entered into by and among
Alteon Inc., a Delaware corporation (the “Company”), and the purchasers (the
“Purchasers”) identified on the signature pages to that certain Registration
Rights Agreement dated as of January 11, 2007 (the “Registration Rights
Agreement”).

WHEREAS, in connection with the execution and delivery of that certain Note and
Warrant Purchase Agreement, dated as of January 11, 2007, by and among the
Company and the Purchasers, the Company issued and sold to the Purchasers (i) an
aggregate of $3,000,000 of its Senior Convertible Secured Promissory Notes (the
“Notes”), each dated January 11, 2007, and (ii) warrants (the “Warrants”), each
dated January 11, 2007, to purchase and aggregate of 25,734,453 shares of the
common stock, $0.01 par value per share (the “Common Stock”) of the Company, and
the Company granted the Purchasers certain registration rights with respect to
the Common Stock issuable upon conversion of the Notes and exercise of the
Warrants pursuant to the Registration Rights Agreement, and 

WHEREAS, in accordance with Section 6(g) of the Registration Rights Agreement,
the Company and the Purchasers desire to amend the Registration Rights Agreement
as set forth herein.

NOW THEREFORE, in consideration of the mutual covenants contained herein, and
for good and valuable consideration, the receipt and sufficiency of which is
hereby acknowledged, the Company and each of the Purchasers agree as follows:

1.  Amendment to Registration Rights Agreement. The definition of Filing Date is
hereby deleted in its entirety and replaced with the following:
 
“Filing Date” means, with respect to the initial Registration Statement required
hereunder, June 15, 2007, with respect to any additional Registration Statements
which may be required pursuant to Section 3(c), the 30th day following the date
on which the Company first knows, or reasonably should have known that such
additional Registration Statement is required hereunder.
 
2.  Ratification. The parties hereby ratify and confirm in all respects the
Registration Rights Agreement, as amended by this Amendment.
 
3.  Governing Law. All questions concerning the construction, validity,
enforcement and interpretation of the Registration Rights Agreement shall be
governed by and construed and enforced in accordance with the internal laws of
the State of New York, without regard to the principles of conflicts of law
thereof.
 
 
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4.  Other Matters. The Company hereby acknowledges and agrees that the execution
and delivery by the Purchasers of this Amendment shall not be deemed to create a
course of dealing or otherwise obligate the Purchasers to execute similar
extensions, amendments or waivers under the same or similar circumstances in the
future.
 
5.  Execution. This Amendment may be executed in two or more counterparts, all
of which when taken together shall be considered one and the same agreement and
shall become effective when counterparts have been signed by each party and
delivered to the other party, it being understood that both parties need not
sign the same counterpart. In the event that any signature is delivered by
facsimile transmission or by e-mail delivery of a “.pdf” format data file, such
signature shall create a valid and binding obligation of the party executing (or
on whose behalf such signature is executed) with the same force and effect as if
such facsimile or “.pdf” signature page were an original thereof.
 

 
[remainder left intentionally blank]
 
 
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IN WITNESS WHEREOF, the undersigned hereby executes this Amendment No. 1 as of
the date first set forth above..
 

ALTEON INC.
 
 
Address for Notice:
By:/s/ Noah Berkowitz                                                   
Name: Noah Berkowitz
Title: President
 
221 West Grand Avenue
Montvale, NJ 07645
With a copy to (which shall not constitute notice):
 
Mintz Levin Cohn Ferris Glovsky and Popeo, P.C.
One Financial Center
Boston, MA 02111
Attn: William T. Whelan, Esq.
 

[REMAINDER OF PAGE INTENTIONALLY LEFT BLANK
SIGNATURE PAGE FOR PURCHASER FOLLOWS]
 
 
 

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IN WITNESS WHEREOF, the undersigned hereby executes this Amendment No. 1 as of
the date first set forth above. 

THE PURCHASERS:
 
BAKER/TISCH INVESTMENTS, L.P.
By:   Baker/Tisch Capital, L.P.,
         its general partner
By:   Baker/Tisch Capital (GP), LLC,
         its general partner
 
By:   /s/ Felix Baker                               
Name: Felix Baker, Ph.D.
Title: Managing Member
 
BAKER BIOTECH FUND I, L.P.
By:   Baker Biotech Capital, L.P.,
         its general partner
By:   Baker Biotech Capital (GP), LLC,
         its general partner
 
By:          /s/ Felix Baker                                
Name: Felix Baker, Ph.D.
Title: Managing Member
 
Baker Brothers Life Sciences, L.P.
By:   Baker Brothers Life Sciences Capital, L.P.
         its general partner
By:   Baker Brothers Life Sciences Capital (GP), LLC
         is general partner
 
By:   /s/ Felix Baker                               
        Name: Felix Baker, Ph.D.
         Title: Managing Member
 
14159, L.P.
By:   14159 Capital, L.P.,
         its general partner
By:   14159 Capital (GP), LLC,
         is general partner
 
By:   /s/ Felix Baker                               
         Name: Felix Baker, Ph.D.
         Title: Managing Member
 
 
Address for Notice:
667 Madison Avenue
17th Floor
New York, NY 10021

 

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