Revolutionizing the Treatment of Cancer

Revolutionizing the Treatment of Cancer September 2013

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, as a result of certain risks and uncertainties, including 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: Revolutionizing the Treatment of Cancer Identify novel drug targets which are specific to cancer cells: Increased efficacy, reduced toxicity Efficacy against multiple drug resistant cancer cells Synergism with existing cytotoxic compounds Nano Polymer Drug Conjugate System (NPDCS) combines existing anticancer agents with a polymer/signaling moiety which directs the drug directly to the tumor: Lower risk strategy that utilizes clinically proven anticancer drugs Maximizes drug levels in the cancer tumor and minimizes circulating drug levels Maximizing efficacy and minimizing toxicity 3

Rexahn Investment Highlights Rapidly advancing pipeline: Initiating three clinical trials in 2013 with data in 2014 Pipeline Archexin: Akt1 inhibitor in Phase II clinical development for pancreatic cancer, and an additional indication RX 3117: DNA synthesis inhibitor completed successful exploratory Phase I trial in solid tumors IND cleared FDA and Phase I clinical development will be initiated in 4Q13 Supinoxin (RX 5902): p68 RNA Helicase inhibitor. Phase I clinical trial in cancer patients with solid tumors ongoing Nano Polymer Drug Conjugate System (NPDCS) RX 21101: polymer conjugated form of docetaxel containing a signaling moiety which directs the drug into the tumor maximizing efficacy and minimizing toxicity Strong Intellectual Property position 4

Deep Oncology Pipeline Drug Candidate Mechanism of Action Preclinical Phase I Phase II Phase III Archexin RX 3117 Akt1 Inhibitor DNA Synthesis Inhibitor Supinoxin TM (RX 5902) p68 RNA Helicase Inhibitor Nano Polymer Drug Conjugate System (NPDCS) RX 21101 Docetaxel Conjugate 5

Financial Highlights As of September 1, 2013, cash and cash equivalents on hand totaled approximately $15.7 million For the six month period ended June 30, 2013, total operating expenses were $3.8 million Burn rate of $0.9M/month expected for next 12 months 134.2 million shares of common stock outstanding 6

New and Experienced Management Team Peter D. Suzdak Ph.D., (CEO) CEO as of February 2013 Over 28 years of experience in pharmaceutical industry Formerly at Corridor Pharma, Cardioxyl Pharma, Guilford Pharmaceuticals, Novo Nordisk A/S, NIH, Pfizer Rick Soni, M.B.A., (President & COO) Over 25 years of experience in pharmaceutical industry Formerly at Otsuka America Pharmaceuticals, Novartis, and Schering Plough Ted Jeong, D.Mgt., (Sr. VP & CFO) Over 16 years of experience in capital raising and investment Formerly at Hyundai Venture Investment Corporation 7

RX 3117

RX 3117: Best in Class Antimetabolite Nucleoside Mechanism Current and Future Indications Advantages Patent Clinical Development Inhibition of DNA synthesis Induction of apoptotic cell death Activated by UCK, which is different from gemcitabine Solid tumors: pancreas, NSCLC, colon, renal and other solid tumors Better efficacy and safety than gemcitabine in animal models Activity against gemcitabine resistant cancer cells Superior pharmacokinetic profile compared to gemcitabine: active following oral administration and longer half life Potential market leader in gemcitabine market Patent expires in 2024 Completed exploratory clinical trial in cancer patients for oral bioavailability, safety and pharmacokinetics IND filed (July 2013) and Phase I trial in cancer patients anticipated to start in 2H13 9

RX 3117: Status Investigational New Drug (IND) application for RX 3117 was submitted in July 2013 and has now cleared the 30 day review period by the US Food and Drug Administration (FDA) Rexahn expects to initiate a Phase I clinical trial in cancer patients with solid tumors during the fourth quarter of 2013 Rexahn will be exploring potential partnering opportunities with oncology focused pharmaceutical companies Original deal with Teva was an early preclinical deal Any future deal will be a clinical stage deal with superior financial terms 10

RX 3117: Termination of Collaboration with Teva Collaboration with Teva terminated August 2013 Teva has invested $9.1M in the development of RX 3117 According to Teva RX 3117 appears to have potential in various indications, but does not align with Teva s new Oncology strategy Therapeutic core areas of focus to be Neurology and Respiratory therapeutic areas Teva has terminated a total of 15 programs in the past 2 years Teva to cut $2B in expenses in next 5 years* Teva has terminated four Oncology programs in the past 12 months (CT 011 (Curetech), Lyndor Bioscience, Obatoclax (Cephalon))* * Teva Investor Day Presentation, December 2012, subsequent Teva press releases and FierceBiotech 2012, 2013 11

RX 3117: Exploratory Phase I clinical Trial (Completed) Exploratory Phase I clinical trial of RX 3117 in cancer patients conducted in Europe in 2012 Oral administration of RX 3117 demonstrated an oral bioavailability of 56% and a plasma half life (T 1/2 ) of 14 hours Superior profile compared to gemcitabine RX 3117 was safe and well tolerated in all subjects throughout the dose range tested 12

RX 3117: Preclinical Data Broad spectrum anti tumor activity against 50 different human cancer cell lines Efficacy in 12 mouse xenograft models superior to that of gemcitabine In human cancer cell lines made resistant to the anti tumor effects of gemcitabine, RX 3117 still retains its full anti tumor activity Tumor volume (mm 3 ) Days Colo-205 xenograft mice model 13

RX 3117 Phase I Clinical Trial Design Dose escalation study to determine safety and efficacy in patients with solid tumors Decision to escalate dose made by external safety review committee approximately 14 days after first cycle is complete Patients have the possibility to receive up to 8 cycles of treatment Patients are scanned (CT or MRI) for assessment of solid tumors Scan is repeated at the end of every 2 cycles of treatment Initiate in 4Q13 Initial clinical data available in 2H14 14

Archexin

Archexin: Best in Class Akt1 Inhibitor Mechanism Inhibitor of the protein kinase Akt1 Involvement in tumor cell growth, survival and angiogenesis Inhibition of Akt1 mediated drug resistance Clinical Development Phase I trial in cancer patients completed Pancreatic cancer Phase IIa completed Phase IIa trial to begin in 2H13 Advantages Patent Targeting a major signal system Excellent safety profile in humans Orphan designations for 5 cancers (pancreatic cancer, ovarian cancer, stomach cancer, RCC, glioblastoma) Patent expires in 2025 16

Archexin s Attractive Commercial Opportunity ARCHEXIN is: Well POSITIONED to address unmet medical needs in Pancreatic, Ovarian and Stomach cancer, Renal cell carcinoma, Glioblastoma (all orphan drug designation granted by the FDA), Prostate and Hematological malignancies EFFECTIVE in combination with gemcitabine reducing risk and safety concerns increased efficacy A NOVEL modality, EASY to manufacture and has a follow on targeted nano formulation that will afford INCREASED life cycle management Percentage of patients 100 80 60 40 20 0 Renal Cell Carcinoma Current Unmet Medical Need Treated Patients Ovarian Prostate Pancreatic Multiple sources: Decision Resources, Feb 2010 targeted oncology market report, Cancer.gov, NCI 17

Target: Akt1 Significant increase in the activated form of Akt1 (Phosphorylated Akt1) in cancer cells Results in increased tumor cell growth/size, proliferation, survival, neovascularization and resistace to cytotoxic agents Native Akt1 Activated Akt1 mrna expression of Akt1 Archexin selectively blocks the native and activated forms of Akt1 18

Archexin: Phase I Clinical trial (completed) Phase I objective To determine maximum tolerated dose, safety and pharmacokinetic profiles Phase I results: MTD was 250 mg/m 2 /d in Patients with an advanced cancer after up to two cycles of treatment The dose limiting toxicity was Grade 3 fatigue; no significant hematological abnormalities Phospho Akt1 being developed as a clinical biomarker J Clin Onc, 2007 ASCO Annual Meeting Proceedings Part I. Vol 25, No. 18S (June 20 Supplement), 2007: 3564 19

Archexin: Phase IIa Study in Metastatic Pancreatic Cancer (completed) Archexin in combination with gemcitabine was safe, well tolerated and demonstrated preliminary signs of efficacy in patients with advanced pancreatic cancer Open label 2 stage study to assess the safety and efficacy of Archexin in combination with gemcitabine 31 subjects enrolled (10 for safety, 21 for efficacy) with ages ranging 18 65 years with metastatic pancreatic cancer Archexin in combination with gemcitabine provided a median survival of 9.1 months compared to the historical survival data of 5.65 months (Burris et al., 1997, J. Clin Oncol 15:2403) for standard single agent gemcitabine therapy Most frequently reported adverse events include constipation, nausea, abdominal pain, and pyrexia, regardless of relatedness 20

Archexin: Potent anti proliferative effects against cancer cell lines expressing activated Akt1 Archexin potently inhibits the growth of cancer cell lines containing activated Akt1 Board spectrum of potential clinical utility 21

Archexin: Clinical Development Plan Expand Phase II program to include additional cancer types with increased activated Akt1 A scientific, clinical and business analysis of potential indications for a Phase IIa clinical trial with Archexin has been completed Rexahn is now working with key clinical opinion leaders to finalize the design of a Phase IIa clinical trial in a selected tumor type Rexahn anticipates updating investors on the tumor type selection and Phase IIa trial timeline early in the fourth quarter of 2013 22

Supinoxin TM (RX 5902)

Supinoxin: Best in Class p68 Helicase Inhibitor Mechanism Inhibition of p68 RNA helicase Blocks upregulation of cancer related genes Current and Future Indications Solid tumors: pancreas, NSCLC, colon, renal and other solid tumors Advantages Anti proliferative effects Synergistic with cytotoxic agents Efficacy against drug resistant cancer cells Orally bioavailable Patent Patent expires in 2025 Clinical Development IND filed Phase I clinical trial in cancer patients ongoing 24

Supinoxin s Attractive Commercial Opportunity Supinoxin is: EFFECTIVE against most difficult cancers Melanoma, Renal Cell Carcinoma, Ovarian and Pancreatic cancer (fastest growing drugtreatable pool populations*) EFFECTIVE against multi drug resistance, based on resistance reversing effects in drug resistant cancer cells EFFECTIVE as a combination therapy growth inhibition of cancer cells in combination with leading anticancer drugs CONVENIENT Oral availability will increase patient compliance Percentage of patients 100 80 60 40 20 0 Current Unmet Medical Need Treated Patients Melanoma Renal Cell Carcinoma Ovarian Pancreatic Multiple sources: Decision Resources, Feb 2010 targeted oncology market report, Cancer.gov, NCI 25

Supinoxin: Mechanism of action Summary Phosphorylated p68 is highly expressed in cancer cells (not in normal cells) Results in upregulation of cancer related genes P p68 Resulting in cancer cell proliferation/tumor growth Supinoxin Selectively blocks Phosphorylated p68 Decreased proliferation/growth of cancer cells Synergism with cytotoxic agents Activity against drug resistant cancer cells Upregulation of Cyclin D1, C jun and C myc Cancer cell Proliferation/Tumor growth 26

Supinoxin: Phase I Clinical Trial Ongoing Conducted at three clinical oncology centers in the United States Dose escalation design Decision to escalate the dose will be made after one cycle of treatment, based on safety and tolerability Each patient will then have the ability to continue on drug for a total of six cycles of treatment. Patients will be assessed by CT or MRI prior to the start of therapy and after every two cycles of therapy for tumor progression Rexahn anticipates updating investors on this Phase I trial in early 2014 27

Supinoxin: Increased Survival in Human Renal Cell Carcinoma and Pancreatic Cancer Xenograft Models 28

Nano Polymer Drug Conjugate System (NPDCS)

Nano Polymer Drug Conjugate System (NPDCS) Combines existing chemotherapeutic agents with a proprietary polymer carrier that contains a signaling moiety which directs the drug directly into the tumor Minimizes the levels of freely circulating drug thereby reducing potential adverse events Maximizes accumulation of drug in the tumor thereby increasing antitumor activity NPDCS is a broad platform that has the potential to generate multiple drug candidates going forward First drug candidate: RX 21101, a polymer conjugated form of docetaxel Preclinical studies demonstrated increased efficacy and reduced toxicity, as compared to intravenously administered free docetaxel. 30

Corporate Overview Milestones Highlights

Major Milestones in 2013/2014 Filed RX 3117 IND (July 2013) In licensed Nano Polymer Drug Conjugate System (NPDCS) (July 2013) First cancer patient dosed with Supinoxin TM (RX 5902) (August 2013) Initiate Phase II clinical study with Archexin (4Q13) Initiate Phase I clinical study with RX 3117 in cancer patients with solid tumors (4Q13) Initial data from RX 5902 Phase I clinical study (3Q14) Initial data from Archexin Phase II studies (4Q14) Initial data from RX 3117 Phase I clinical trial (4Q14) 32

Financial Highlights Rexahn Financial Highlights Ticker RNN Exchange NYSE MKT Market Price (9/6/13) $0.48 Market Capitalization (9/6/13) $64 MM Shares Outstanding (9/6/13) 134.2 MM Insider Ownership 10% Cash Balance (9/1/13) $15.7 MM Monthly Est. Cash Burn $0.9 MM 33

Rexahn Investment Highlights Rapidly advancing pipeline: Initiating three clinical trials in 2013 with data in 2014 Pipeline Archexin: Akt1 inhibitor in Phase II clinical development for pancreatic cancer, and a additional indication RX 3117: DNA synthesis inhibitor completed successful exploratory Phase I trial in solid tumors IND cleared FDA and Phase I clinical development will be initiated in 4Q13 Supinoxin (RX 5902): p68 RNA Helicase inhibitor. Phase I clinical trial in cancer patients solid tumors ongoing Nano Polymer Drug Conjugate System (NPDCS) RX 21101: polymer conjugated form of docetaxel containing a signaling moiety which directs the drug into the tumor maximizing efficacy and minimizing toxicity Strong Intellectual Property position 34

Revolutionizing the Treatment of Cancer REXAHN PHARMACEUTICALS, INC. 15245 Shady Grove Road, Suite 455 Rockville, MD 20850 Tel. 240 268 5300 Fax. 240 268 5310 www.rexahn.com