AGREEMENT TO JOINTLY FILE SCHEDULE 13D

 
            Exhibit
      99.1

AGREEMENT
TO
JOINTLY FILE SCHEDULE 13D

            The
      undersigned hereby agree to jointly prepare and file with regulatory
      authorities a Schedule 13D and any future amendments thereto reporting
      each of the undersigned’s ownership of securities of Cougar Biotechnology,
      Inc. and hereby affirm that such Schedule 13D is being filed on behalf of
      each of the undersigned.

                                                      Dated:
      February 3, 2009

                                                /s/ Xxxxxxx
      X. Xxxxxxxxx, M.D.
                                                 
                                                Xxxxxxx
      X. Xxxxxxxxx, M.D.

                                                Horizon
      BioMedical Ventures, LLC
                                                 
                                                by: 
                                                /s/ Xxxxxxx
      X. Xxxxxxxxx, M.D.
                                                 
                                                Xxxxxxx
      X. Xxxxxxxxx, M.D.,

                                                Managing
      Member

Document Metadata

AGREEMENT TO JOINTLY FILE SCHEDULE 13D

Document Metadata


Dated: February 3, 2009		/s/ Xxxxxxx X. Xxxxxxxxx, M.D.
		Xxxxxxx X. Xxxxxxxxx, M.D.


	Horizon BioMedical Ventures, LLC


	by:	/s/ Xxxxxxx X. Xxxxxxxxx, M.D.
		Xxxxxxx X. Xxxxxxxxx, M.D.,
		Managing Member