AMENDMENT NO. 1 TO OPTION AND LICENSE AGREEMENT

Exhibit 10.54

Confidential treatment has been requested for portions of this exhibit. The copy filed herewith omits the information subject to the confidentiality request. Omissions are designated as [***]. A complete version of this exhibit has been filed separately with the Securities and Exchange Commission.

AMENDMENT NO. 1 TO

OPTION AND LICENSE AGREEMENT

This Amendment No. 1 (this “ Amendment ”) to Option and License Agreement effective as of September 27th, 2004 (the “ Amendment Date ”) is entered into by and between Sanquin Blood Supply Foundation for the purpose of this Amendment acting through her Research Division, formed under the laws of the Netherlands (“ CLB ”), and Seattle Genetics, Inc., a Delaware corporation (“ SGI ”).

RECITALS

WHEREAS, SGI and CLB previously entered into an Option and License Agreement dated July 5, 2001 (the “ License Agreement ”);

WHEREAS, the parties now wish to amend the License Agreement on the terms set forth herein;

NOW THEREFORE, in consideration of the mutual covenants set forth below, the parties amend the License Agreement and otherwise agree as follows (with all capitalized terms used but not defined herein having the meanings set forth in the License Agreement):

AGREEMENT

1. Section 1 of the License Agreement is amended to add a new definition of “Phase I Clinical Trial” to read as follows:

“ Phase I Clinical Trial ” shall mean a clinical trial designed to evaluate the pharmacokinetic and pharmacodynamic properties, maximum tolerated dose, dosing interval, and absorption, distribution, metabolism and excretion of a candidate drug.”

2. Section 6.3 of the License Agreement is amended and restated to read in its entirety as follows:

6.3 Milestone Payments . Within [***] following the occurrence of each of the events specified below for the first Licensed Product only, SGI shall pay to CLB the following amounts: