exhibit 4. 1 number shares trbn 0001 incorporated under the laws of cusip 89778n 10 2 the state of delaware trubion pharmaceuticals, inc. see reverse for certain definitions this certifies that by : is the record holder of u countersigned. s. and fully paid and non - assessable shares of common stock, 0. 001 par value per share, of st ock trubion pharmaceuticals, inc. transferable on the books of the corporation in person or by duly authorized attorney upon surrender of this certificate properly endorsed. this certificate registered : is not valid until countersigned by the transfer agent and registered by the registrar. transfer witness the facsimile seal of the corporation and the facsimile signatures of its duly authorized officers. transfer dated : agent authorized and corpora tion secretary chief executive president signa ture registrar exhibit 4. 1 number shares trbn 0001 incorporated under the laws of cusip 89778n 10 2 the state of delaware trubion pharmaceuticals, inc. see reverse for certain definitions this certifies that by : is the record holder of u countersigned. s. and fully paid and non - assessable shares of common stock, 0. 001 par value per share, of st ock trubion pharmaceuticals, inc. transferable on the books of the corporation in person or by duly authorized attorney upon surrender of this certificate properly endorsed. this certificate registered : is not valid until countersigned by the transfer agent and registered by the registrar. transfer witness the facsimile seal of the corporation and the facsimile signatures of its duly authorized officers. transfer dated : agent authorized and corpora tion secretary chief executive president signa ture registrar number shares trbn 0001 incorporated under the laws of cusip 89778n 10 2 the state of delaware trubion pharmaceuticals, inc. see reverse for certain definitions this certifies that by : is the record holder of u countersigned. s. and fully paid and non - assessable shares of common stock, 0. 001 par value per share, of st ock trubion pharmaceuticals, inc. transferable on the books of the corporation in person or by duly authorized attorney upon surrender of this certificate properly endorsed. this certificate registered : is not valid until countersigned by the transfer agent and registered by the registrar. transfer witness the facsimile seal