X0202 4 2008-05-28 0 0001298521 Trubion Pharmaceuticals, Inc TRBN 0001229592 GILLIS STEVEN ARCH VENTURE PARTNERS 1000 2ND AVENUE, SUITE 3700 SEATTLE WA 98104 1 0 0 1 10% Owner Indirect Common Stock 2357046 I By ARCH entities Stock option (right to buy) 6.63 2008-05-28 4 A 0 5000 0.00 A 2018-05-28 Common stock 5000 5000 D Represents (a) 2,209,741 shares held by ARCH Venture Fund V, L.P., (b) 132,802 shares held by Healthcare Focus Fund, L.P. and (c) 14,503 shares held by ARCH V Entrepreneurs Fund, L.P. (together, the "ARCH Entities"). The reporting person is an employee of ARCH Venture Corporation, a service provider to the ARCH Entities. The reporting person disclaims beneficial ownership of the shares held by each of the ARCH Entities, except to the extent of his proportionate pecuniary partnership interest in ARCH Venture Fund V, L.P. Option vests 100% on May 15, 2009, subject to the individual's provision of service to the issuer on such date. /s/ Muchelle Burris as attorney-in-fact for Steven Gillis 2008-05-29