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| 1. | I have reviewed this report on      Form 10-Q of Rexahn Pharmaceuticals,  Inc.; |
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| 2. | Based on my knowledge, this      report does not contain any untrue statement of a material fact or omit to      state a material fact necessary to make the statements made, in light of      the circumstances under which such statements were made, not misleading      with respect to the period covered by this  report; |
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| 3. | Based on my knowledge, the      financial statements, and other financial information included in this      report, fairly present in all material respects the financial condition,      results of operations and cash flows of the registrant as of, and for, the      periods presented in thisreport; |
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| 4. | The registrant’s other certifying      officer and I are responsible for establishing and maintaining disclosure      controls and procedures (as defined in Exchange Act Rules 13a-15(e)      and 15d-15(e)) for the registrant and  have: |
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|   | a) | Designed such disclosure controls      and procedures, or caused such disclosure controls and procedures to be      designed under our supervision, to ensure that material information      relating to the registrant, including its consolidated subsidiaries, is      made known to us by others within those entities, particularly during the      period in which this report is being  prepared; |
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|   | b) | Not      applicable; |
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|   | c) | Evaluated the effectiveness of      the registrant’s disclosure controls and procedures and presented in this      report our conclusions about the effectiveness of the disclosure controls      and procedures, as of the end of the period covered by this report based      on such evaluation; and |
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|   | d) | Disclosed in this report any      change in the registrant’s internal control over financial reporting that      occurred during the registrant’s most recent fiscal quarter (the      registrant’s fourth fiscal quarter in the case of an annual report) that      has materially affected, or is reasonably likely to materially affect, the      registrant’s internal control over financial reporting;      and |
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| 5. | The registrant’s other certifying      officer and I have disclosed, based on our most recent evaluation of      internal control over financial reporting, to the registrant’s auditors      and the audit committee of the registrant’s board of directors (or persons      performing the equivalentfunctions): |
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|   | a) | All significant deficiencies and      material weaknesses in the design or operation of internal control over      financial reporting which are reasonably likely to adversely affect the      registrant’s ability to record, process, summarize and report financial      information; and |
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|   | b) | Any fraud, whether or not      material, that involves management or other employees who have a      significant role in the registrant’s internal control over financial      reporting. |
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| /s/ Chang H. Ahn                                        |   |
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| Chang      H. Ahn                                            |   |
| Chief      Executive Officer of Rexahn Pharmaceuticals, Inc. |   |

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