X0306 4 2013-12-17 0 0000894158 Synthetic Biologics, Inc. SYN 0001091823 KIRK RANDAL J C/O THIRD SECURITY, LLC 1881 GROVE AVENUE RADFORD VA 24141 0 0 1 0 0001356090 INTREXON CORP C/O LEGAL DEPARTMENT 20374 SENECA MEADOWS PARKWAY GERMANTOWN MD 20876 0 0 1 0 Common Stock 2013-12-17 4 P 0 500000 1.00 A 3625000 I by NRM VII Holdings Common Stock 2013-12-17 4 P 0 2000000 1.00 A 8675768 I by Intrexon Randal J. Kirk controls NRM VII Holdings I, LLC ("NRM VII Holdings"). Shares held by this entity may be deemed to be indirectly beneficially owned (as defined under Rule 13d-3 promulgated under the Securities Exchange Act of 1934, as amended) by Mr. Kirk. Mr. Kirk disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein. Randal J. Kirk, directly and through certain affiliates, has voting and dispositive power over a majority of the outstanding capital stock of Intrexon Corporation ("Intrexon"). Mr. Kirk may therefore be deemed to have voting and dispositive power over the shares of the issuer owned by Intrexon. Shares held by Intrexon may be deemed to be indirectly beneficially owned (as defined under Rule 13d-3 promulgated under the Securities Exchange Act of 1934, as amended) by Mr. Kirk. Mr. Kirk disclaims beneficial ownership of such shares, except to the extent of any pecuniary interest therein. /s/ Randal J. Kirk 2013-12-19 /s/ Randal J. Kirk, CEO Intrexon Corporation 2013-12-19