This excerpt taken from the TPTX 10-K filed Mar 29, 2007.
6. EXECUTION OF DOCUMENTS. You hereby acknowledge and agree that the manner selected by the Company by which you indicate your consent to your Grant Notice is also deemed to be your execution of your Grant Notice and of this Agreement. You further agree that such manner of indicating consent may be relied upon as your signature for establishing your execution of any documents to be executed in the future in connection with your Award. This Agreement shall be deemed to be signed by the Company and you upon the respective signing by the Company and you of the Grant Notice to which it is attached.