|   | [ University of Glasgow letterhead ] |
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| Pathfinder, LLC12 Bow StreetCambridgeMA 02138USA  |     19 April 2012 |
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| STRICTLY PRIVATE AND CONFIDENTIAL                 |

| 1.   | The Subsequent Period will be extended for a further period of twelve (12) months (and so the Subsequent Period will now expire on 23 March 2013); |
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| 2.   | The research to be carried out by the University during the extended portion of the Subsequent Period is set out in Appendix 1 to this letter; |
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| 3.   | In consideration of the research services to be conducted by the University during the extended portion of the Subsequent Period, the Company shall pay to the University the sum of four hundred and thirty one thousand, six hundred and twenty eight poundsand fifty three pence (£431,628.53).  Such sum will be payable in twelve (12) equal instalments monthly in arrears, the first instalment being due on 23 April 2012 and each subsequent instalment being due on the 23rd day of the relevant calendar month.  Such sums shall be paid by the Company to the University by way of a bank transfer. |
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| 4.   | The Research Agreement will continue in full force and effect, as varied by the terms of this letter, unless and until terminated in accordance with its terms. |
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| 5.   | This letter will be governed by and construed in accordance with the laws of Scotland |
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|   By: /s/ Richard L. Franklin          Richard L. Franklin, CEO .................................................... |   4/24/12.......................... |
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| For and on behalf of Pathfinder, LLC                                                                                                                                                                                                            | Date                                                                          |

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