RNN Rexahn Pharmaceuticals, Inc.

 Investor Presentation  September 2015  1 

 Safe Harbor Statement  The statements that follow (including projections and business trends) are forward-looking statements. Rexahn’s actual results may differ materially from anticipated results and expectations expressed in these forward-looking statements, including as a result of certain risks and uncertainties, such as Rexahn’s lack of profitability, the need for additional capital to operate its business to develop its product candidates; the risk that Rexahn’s development efforts relating to its product candidates may not be successful; the possibility of being unable to obtain regulatory approval of Rexahn’s product candidates; the risk that the results of clinical trials may not be completed on time or support Rexahn’s claims; demand for and market acceptance of Rexahn’s drug candidates; Rexahn’s reliance on third party researchers and manufacturers to develop its product candidates; Rexahn’s ability to develop and obtain protection of its intellectual property; and other risk factors set forth from time to time in our filings with the Securities and Exchange Commission. Rexahn assumes no obligation to update these forward-looking statements.  2 

   Rexahn: Developing the Next Generation of Cancer Therapies*  3  REXAHN’S PLATFORM FOR GROWTHNew Management Team – Proprietary Technologies – Robust Clinical & Pre-Clinical Pipeline  Therapies target onlycancer cells  Unique mechanismof action      3in clinicaltrials  Novelproducts in pipeline      Efficacy against toughest cancers  Addressingunmetneeds      Clinical Proof of conceptdata  2016-2017transformative years    *Based on pre-clinical animal model data 

   AGENDANext Generation of Cancer Therapies  The Company  The Pipeline  The Future                  4 

 Rexahn: At a Glance  Clinical stage biopharmaceutical company developing novel targeted cancer therapeuticsselectively destroy cancer cellsspare normal, healthy cellsHeadquartered in Rockville, MarylandNYSE MKT: RNNMarket cap: $105M7% owned by management/insidersCash and investments at June 30, 2015: $26.0MEstimated quarterly burn rate: ~4.0MGAAP net loss for the three months ended June 30, 2015: $(0.02)  5 

   New, Experienced Leadership Team – Built in Last 2 Years  Reza Mazhari, Vice President, Translational Medicine  Experienced pharmaceutical executive; success taking multiple compounds from concept to clinic Co-Founder of Cardioxyl Pharmaceuticals, VP, Drug Discovery and Development at Cerecor    Ted Jeong D.Mgt., Sr. Vice President and Chief Financial Officer  Extensive experience in venture capital and investment bankingOversees all aspects of capital raising, accounting, operations, and corporate development     Ely Benaim M.D., Chief Medical Officer  25+ years experience in healthcare including 15 years of clinical research experience in academia, government and pharmaceutical industryExtensive experience in global regulatory affairs    Peter Suzdak Ph.D., Chief Executive Officer  25+ years experience in the biopharmaceutical industryBroad experience spanning pre-clinical, development and commercialization; 18 IND filings, 3 NDA submissions 

 A Diversified Portfolio of Targeted Cancer Therapeutics  DrugCandidate  Mechanismof Action  Preclinical  Phase I  Phase Ib/IIa  Preliminary Data  Clinical Proof of Concept  SupinoxinTM (RX-5902)  Phosphorylated p68 inhibitor        Phase IQ3 2015  Initiate 2016  RX-3117  Cancer cell specific nucleoside analog         Phase I Q3 2015  Initiate 2016  Archexin®  Akt-1 inhibitor         Phase IIa Part 1 H2 2015  Complete 2016                RX-21101  Docetaxelconjugate                    Targeted Nano Technology Drug Delivery Platform  7 

 What Differentiates Rexahn’s Programs: Potential Advantages Over Existing and Emerging Therapies  8    Traditional Chemotherapy  PD1 / CAR T-CellTherapies  RexahnTherapies  Selectively targets cancer cells        Reduced adverse events        Convenient oral dosing(Supinoxin™ and RX 3117)        Active against toughest cancers        Synergistic with existing therapies        Broad spectrum of anti-cancer activity                            ü    ü                ü    ü  ü  ü  ü  ü  ü 

   AGENDANext Generation of Cancer Therapies  The Company  The Pipeline  The Future                  9 

 Advancing Our Clinical-Stage Products*  10    DRUGCANDIDATE  POTENTIALINDICATION  STATUS  MARKETOPPORTUNITY  Supinoxin™  Relapsed & Refractory Solid Tumors  Phase I  >$3B  RX-3117  Gemcitabine Resistant Solid Tumors  Phase Ib  >$4B  Archexin®  Metastatic Renal Cell Carcinoma  Phase IIa  >$700M    *Company estimates based on information from Datamonitor, Global Data and MedTrack reports as of August 2015 

 SUPINOXIN™ OVERVIEWPotential First-in-Class Inhibitor of a Unique Cancer Protein  The CandidateOrally active, highly potent small molecule inhibitor of phosphorylated p68 (p-p68)Significant Unmet Medical NeedDemonstrated activity in >100 human cancer cell lines including: triple-negative breast, colon, ovarian, pancreas, non small cell lung cancer, and renalClinical Development – Status Phase I clinical trial with Supinoxin™ in cancer patients is ongoingPreliminary data expected Q3 2015Initiate Clinical Proof-of-Concept study in 2016Commercial PotentialPotential market opportunity: >$3BStrong intellectual property protectionOngoing corporate partnership discussions  11 

   SUPINOXIN™ UNIQUE MECHANISM OF ACTIONPotent, Well-Tolerated with Activity Against Difficult-to-Treat Cancers*  12  Decreases proliferation / growth of cancer cellsSynergy with existing anti-cancer drugsActive against hard-to-treat cancers    Supinoxin™ MOA supports a biomarker strategy for patient selection  ADVANTAGES  *Based on available clinical and pre-clinical data as of August 2015 

 SUPINOXIN™ EVIDENCE OF SUCCESSBlocks the Growth of Human Triple-Negative Breast Cancer Cells  13  Large opportunity: Triple Negative Breast Cancer represents 20% of breast cancer diagnoses with limited treatment options; potential rapid path to market     Human Triple-Negative Breast Cancer (MDA-MB-231) Xenograft Model    Days  Last dose  Supinoxin™(160 mg/kg, po, qwk x 3)  Supinoxin™(320 mg/kg, po, qwk x 3)  Supinoxin™(600 mg/kg, po, qwk x 3)  Abraxane (5 mg/kg, iv, biwk x 3)  Vehicle  No tumor growth 

   SUPINOXIN™ EVIDENCE OF SUCCESSSurvival Benefit in Human Triple Negative Breast Cancer Animal Models  14  SupinoxinTM cessation  Human Triple Negative Breast Cancer (MDA-MB-231) Xenograft Model    Supinoxin™ (600 mg/kg, po, 5 qwk x3)  Abraxane (5mg/kg, iv, biwk x 3)  Vehicle  Supinoxin™ (320 mg/kg, po, 5 qwk x3)  Supinoxin™ (160 mg/kg, po, 5 qwk x3) 

 SUPINOXIN™ TRIAL STATUSOngoing Phase I Dose-Escalation Trial  15  Primary Endpoints    MaximumTolerated Dose(MTD)  25, 50, 100, 150, 225, 300 , 425, 575, and 775 mg dose cycles completePatient enrollment and dosing ongoingMaximum tolerated dose (MTD) not yet achieved   Dose Limiting Toxicities  Not yet determined  Safety Profile*  Preliminary - Safe and well tolerated requiring testing of additional higher doses to define MTDPreliminary data expected Q3 2015  Secondary Endpoints    Pharmacokinetics  Dose-proportional exposure – Estimated oral bioavailability of 51%Pharmacokinetics similar to what was seen in preclinical modelsPreliminary data expected Q3 2015  Tumor Response  Preliminary data expected Q3 2015  *Based on available clinical data as of August 2015 

 SUPINOXIN™ NEXT STEPSClinical Plan – Determine Clinical Activity Prior to Initiating Pivotal Phase Ib/IIa Clinical Trial  16  DrugCandidate  2015  H1 2016  H2 2016 / 2017  Indication  SupinoxinTM(RX-5902)                                                             Phase Ib/IIa  Phase Ib/IIa  Phase Ib/IIa  Phase Ib Safety + MTD Study      New Study 3 arms  Triple-negativebreast cancer  Colon cancer  Ovarian cancer 

 Advancing Our Clinical-Stage Products*  17    DRUGCANDIDATE  POTENTIALINDICATION  STATUS  MARKET OPPORTUNITY  Supinoxin™  Relapsed & Refractory Solid Tumors  Phase I  >$3B  RX-3117  Gemcitabine Resistant Solid Tumors  Phase Ib  >$4B  Archexin®  Metastatic Renal Cell Carcinoma  Phase IIa  >$700M    *Company estimates based on information from Datamonitor, Global Data and MedTrack reports as of August 2015 

 RX-3117 OVERVIEWNovel Next Generation Nucleoside Compound  The CandidateCancer cell specific small molecule nucleoside analogue that inhibits DNA and RNA synthesis causing cell death Prodrug activated by UCK2 which is only present in cancer cellsActive following oral administrationSignificant Unmet Medical NeedGemcitabine-resistant cancers: bladder, colon, pancreatic, non-small cell lung cancer, renal and other solid tumorsClinical Development – StatusCompleted Phase I trial confirming oral bioavailability and initial safetyPhase Ib clinical trial in cancer patients is ongoingPreliminary data expected Q3 2015Initiate Clinical Proof-of-Concept study in 2016Commercial PotentialPotential market opportunity: >$4BStrong intellectual property portfolioOngoing partnership discussions  18 

   Anti-tumor activities against a broad spectrum of cancersAnti-cancer effect on gemcitabine resistant cancers    RX-3117 UNIQUE MECHANISM OF ACTIONWell Tolerated with Tumor-Specific Activity in Drug-Resistant Cancers*  19  RX-3117 MOA supports a biomarker strategy for patient selection  ADVANTAGES      *Based on available clinical and pre-clinical data as of August 2015 

 RX-3117 EVIDENCE OF SUCCESSEfficacy Against Broad Range of Human Cancer Cell Types  20  % Tumor InhibitionAnimalXenograftModel  Colon  Lung  Panc  Renal  Ovary  Cervical              TUMOR TYPE  More effective than Gemcitabine across broad range of human tumor types    RX-3117  Gemcitabine   

     Tumor Growth Inhibition  RX-3117 EVIDENCE OF SUCCESSEffective Against Gemcitabine Resistant Cancers – Key Advantage  21  25%-40% of cancer patients receiving gemcitabinerapidly become resistant to chemotherapy  RX-3117resulted ingreater tumorgrowth inhibitionthan seen withgemcitabine  Patient derived xenograft model of human pancreatic cancer (Champions TumorGraft®)* P<0.05   The Need   

 RX-3117 TRIAL STATUSOngoing Phase Ib Dose-Escalation Trial  Primary Endpoints    MaximumTolerated Dose(MTD)  30, 60, 100, 150, 200, 500, 1000, and 1500 mg dose cycles completePatient enrollment and dosing ongoingMaximum tolerated dose (MTD) not yet achieved   Dose Limiting Toxicities  Not yet determined  Safety Profile*  Preliminary - Safe and well tolerated requiring testing of additional higher doses to define MTDPreliminary data expected Q3 2015  Secondary Endpoints    Pharmacokinetics  Preliminary data expected Q3 2015  Tumor Response  Preliminary data expected Q3 2015  22  *Based on available clinical data as of August 2015 

 RX-3117 NEXT STEPSClinical Plan – Determine Clinical Activity Prior to Initiating a Pivotal Phase Ib/IIa Clinical Trial  23  DrugCandidate  2015  H1 2016  H2 2016 / 2017  Indication  RX-3117                                                            Phase Ib/IIa  Phase Ib/IIa  Phase Ib/IIa  Phase Ib Safety + MTD Study      New Study 3 arms  Pancreatic cancer  Bladder cancer  NCSL cancer 

 Advancing Our Clinical-Stage Products*    DRUGCANDIDATE  POTENTIAL INDICATION  STATUS  MARKET OPPORTUNITY  Supinoxin™  Relapsed & Refractory Solid Tumors  Phase I  >$3B  RX-3117  Gemcitabine resistant Solid Tumors  Phase Ib  >$4B  Archexin®  Metastatic Renal Cell Carcinoma  Phase IIa  >$700M    24  *Company estimates based on information from Datamonitor, Global Data and MedTrack reports as of August 2015 

 ARCHEXIN® OVERVIEWPotential Best-in-Class AKT-1 Inhibitor  The CandidateNovel inhibitor of cancer cell signaling protein, Akt-1, increasing cancer cell deathTargets clinically validated cancer pathwayAlso inhibits drug resistance; synergistic with approved drugsSignificant Unmet Medical NeedCurrently targeting metastatic renal cell carcinoma (mRCC) Clinical Development – StatusCompleted Phase I trial in cancer patientsPancreatic cancer- Phase IIa completedPhase IIa trial in metastatic RCC – ongoingInitial combination safety data mid 2015Commercial PotentialFDA orphan drug designation for 5 cancers (renal, glioblastoma, ovarian, stomach, pancreas)Potential market opportunity: >$700MStrong intellectual property portfolioOngoing partnership discussions  25 

     ARCHEXIN® UNIQUE MECHANISM OF ACTIONArchexin® Targets A Clinically Validated Cancer Pathway*  PI3K/AKT-1/mTOR pathway involved in cancer cell growth and proliferationAKT-1 inhibitionBlocks the development of resistance to mTOR and TKI inhibitorsBlocks the growth/proliferation of cancer cells  Decreases proliferation / growth of cancer cellsDecreases new blood vessel growthDecreases drug resistance   Mechanism of Action    ADVANTAGES  26      PI3K  Growth Factors  AKT-1    Target SpecificPhosphorylation Events(Nucleus/Cytoplasm)  ApoptosisCell Cycle Regulation  DNA RepairMetabolism  GrowthTranslation  mTOR  SunitinibSorafenibAitinibPazopanib  Everolimus  Archexin  X  Cell Membrane  Tyrosine KinaseReceptor      Integrin            Membrane recruitmentactivation      CytokineReceptor          X  X  AKT-1 may be used as a biomarker to aid in patient selection  *Based on available pre-clinical data as of August 2015 

     Archexin®: A Selective Inhibitor of AKT-1  27  Xenograft model using luciferase-expressinghuman pancreatic cancer cells  Control +Archexin (1 week) +Archexin (2 weeks)  Anti-cancer activity against multiple solid cancer tumorsSynergistic with mTOR and tyrosine kinase inhibitorsPrevents the development of resistance to mTOR inhibitors  Archexin®: AKT-1 Inhibitor 

 ARCHEXIN® TRIAL STATUSCompleted Phase I and Phase IIa Trials  28  Primary Endpoints    MaximumTolerated Dose(MTD)  250 mg/m2/d in patients with an advanced cancer after up to two cycles of treatment  Dose Limiting Toxicities  Grade 3 fatigue; no significant hematological abnormalities  Phase I (Cancer Patients with Solid Tumors)  Primary Endpoint    TumorResponse  Archexin in combination with gemcitabine provided a median survival of 9.1 months compared to 5.65 months for gemcitabine alone  Phase IIa (Metastatic Pancreatic Cancer Patients) 

 29  Phase IIa    StudyDesign  Metastatic renal cell carcinoma (mRCC)Second line therapyAdministered in combination with everolimus (Affinitor®)Part A: Identify maximum tolerated dose in combination with everolimus Part B: Determine safety and efficacy in 30 additional mRCC patients      ARCHEXIN® STATUS AND NEXT STEPSOnly Selective AKT-1 Inhibitor in Clinical Development - Status 

   AGENDANext Generation of Cancer Therapies  The Company  The Pipeline  The Future                  30 

 Robust Pipeline Targeting Multiple Cancer Indications  31  DrugCandidate  2015  H1 2016  H2 2016 / 2017  Proposed Indications  Supinoxin™(RX-5902)                   Triple-negative breast cancer          Colon cancer          Ovarian cancer  RX-3117                  Pancreatic cancer          Bladder cancer          NSCL cancer  Archexin®        Metastatic renal cell cancer  Phase Ib/IIa  Phase Ib/IIa  Phase Ib/IIa  Phase Ib/IIa  Phase Ib/IIa  Phase Ib/IIa  Phase Ib Safety + MTD Study  Complete Phase Ib Safety + MTD Study  Ph IIaData Readouts  Initiate Ph IIa Safety +Efficacy Study Part 2  Report Ph IIa SafetyData Part 1 

         Advance cancer therapies through proof-of-concept clinical development  Establish partnerships with pharmaceutical companies; focus on maximizing shareholder value        Advance pre-clinical oncology programs to address significant unmet needs  32 

 Investor Presentation  September 2015  33