KIRK RANDAL J sold PGEN

Footnotes

The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $3.90 to $4.42, inclusive. The reporting person undertakes to provide to the issuer, any security holder of the issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in footnote (2) to this Form 4.; Randal J. Kirk controls each of Kapital Joe, LLC ("Kapital Joe"), R.J. Kirk Declaration of Trust ("R.J. Kirk DOT"), Parkview 2020 Limited Partnership ("Parkview 2020"), JPK 2008 LLC ("JPK 2008"), JPK 2009 LLC ("JPK 2009"), JPK 2012 LLC ("JPK 2012"), MGK 2008 LLC ("MGK 2008"), MGK 2009 LLC ("MGK 2009"), MGK 2011 LLC ("MGK 2011"), ZSK 2008 LLC ("ZSK 2008"), ZSK 2009 LLC ("ZSK 2009"), Kellie L. Banks (2009) Long Term Trust ("Kellie L. Banks LTT"), Lotus Capital (2000) Company, Inc. ("Lotus"), Sunset 2020 LLC ("Sunset 2020") and Third Security, LLC ("Third Security"). Shares held by these entities may be deemed to be 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.