[GPC Biotech AG Letterhead]





BY EDGAR

Securities and Exchange Commission
Division of Corporation Finance
450 Fifth Street, N.W.
Washington, D.C.  20549

Attention:  Mr. Jim Rosenberg


                                                               September 8, 2006

Re:      GPC Biotech AG
         Form 20-F for Fiscal Year Ended December 31, 2005
         File No. 0-50825

Dear Mr. Rosenberg:

         On September 7, 2006, Kristina Beirne of our company spoke with Mark
Brunhofer of your staff regarding GPC Biotech AG's response to the comment
letter, dated August 16, 2006, concerning the above captioned Annual Report on
Form 20-F. Due to vacation schedules in Europe and limited staff, we were unable
to respond to the aforementioned comment letter within the time period
requested.

         As discussed with Mr. Brunhofer, this letter confirms that GPC Biotech
AG will provide its response letter by October 2, 2006.

         Please contact the undersigned at +49 (89) 8565-2625 or Kristina Beirne
at (609) 524-1028 if you have any questions or comments or require any
additional information in connection with this letter.

GPC BIOTECH AG


/s/ Mirko Scherer
- --------------------------------
Mirko Scherer
Senior Vice President and CFO


cc:  Mark Brunhofer, Securities and Exchange Commission, Senior Staff Accountant
     Bernd R. Seizinger, GPC Biotech AG
     Brent Hatzis-Schoch, GPC Biotech AG
     Kristina Beirne, GPC Biotech AG
     Danielle Carbone, Shearman & Sterling LLP