exhibit 2. 1 execution version agreement and plan of merger dated as of may 17, 2011 agreement and plan of merger dated as of may 17, 2011 by and among shire pharmaceuticals inc. ( “ parent ” ), shire pharmaceuticals inc. ( “ parent ” ), abh merger sub inc. ( “ merger sub ” ), advanced biohealing, inc. ( the “ company ” ), advanced biohealing, inc. ( the “ company ” ), solely for the purposes of section 2. 7 and articles iii, ix and x, canaan vii l. p. solely for the purposes of section 2. 7 and articles iii, ix and x, canaan vii l. p. ( the “ equityholders ’ representative ” ) and, solely for the purposes of section 10. 17, shire plc solely for the purposes of section 10. 17, shire plc ( “ buyer parent ” ) table of contents page article i. definitions 1 section 1. 1 certain definitions 1 section 1. 2 certain additional definitions 12 section 1. 3 determination of pro rata amounts hereunder 14 article ii. the merger 15 section 2. 1 the merger 15 section 2. 2 effects of the merger 15 section 2. 3 closing 15 section 2. 4 effective time 15 section 2. 5 certificate of incorporation and bylaws ; directors and officers 15 section 2. 6 conversion of securities ; treatment of company options and warrants 16 section 2. 7 total cash equity price adjustments 18 section 2. 8 payment of company transaction expenses ; pro - rata bonuses 21 section 2. 9 calculations and iterative process 21 article iii. exchange of company certificates 22 section 3. 1 exchange of company certificates 22 section 3. 2 appraisal rights 24 section 3. 3 escrow 24 section 3. 4 no further ownership rights in shares of company capital stock ; closing of company transfer books 24 article iv. representations and warranties of the company 25 section 4. 1 authority 25 section 4. 2 organization ; subsidiaries 26 section 4. 3 capitalization 26 section 4. 4 conflicts 27 section 4. 5 consents, approvals, etc 27 section 4. 6 financial statements ; sec filings 28 section 4. 7 undisclosed liabilities 28 section 4. 8 certain changes or events 28 section 4. 9 tax matters 28 section 4. 10 litigation and governmental orders 30 section 4. 11 compliance with laws 30 section 4. 12 permits 30 section 4. 13 regulatory matters 30 section 4. 14 tangible property