“While angioplasty can provide short-term symptom relief for patients with PAD below the knee, the procedure lacks durability, often resulting in return of symptoms and repeat interventions. There is a substantial need for new therapies that could improve the outcomes associated with angioplasty procedures, and I look forward to evaluating the potential of vonapanitase in this study,” said Jihad A. Mustapha, M.D., F.A.C.C., F.S.C.A.I., Director of Cardiovascular Research at Metro Health Hospital, and the study’s lead investigator.

The multicenter, randomized, double-blind, placebo-controlled, dose-escalation Phase 1 study will enroll up to 40 patients with PAD undergoing angioplasty of an artery below the knee. Immediately following angioplasty, patients will receive a single administration of either vonapanitase or placebo via a drug- delivery catheter, the Bullfrog® Micro-Infusion Device developed and manufactured by Mercator MedSystems. The study will assess the safety and technical feasibility of vonapanitase administration and will also capture exploratory outcome measures. The Company previously reported the successful completion of a Phase 1 study examining the safety and technical feasibility of administering vonapanitase via the Bullfrog Micro-Infusion Device to patients undergoing angioplasty of an artery above the knee.

Nonclinical studies suggest that vonapanitase, a recombinant human elastase, fragments elastin fibers in blood vessel walls without affecting collagen, which preserves vessel strength. These studies also demonstrated that vonapanitase treatment at sufficient concentrations caused substantial elastin fragmentation in the vessel wall, resulting in acute, localized, permanent arterial dilation.

“We believe that vonapanitase has the potential to address a range of unmet medical needs for patients with kidney and vascular diseases. Our ongoing clinical development in PAD will guide future development and complements our Phase 3 program of vonapanitase in hemodialysis vascular access,” said Timothy Noyes, President and Chief Executive Officer of Proteon.

PAD is a global health problem characterized by a blockage in the arteries that provide blood to the legs. Many patients undergo invasive revascularization procedures, which have poor long-term durability resulting in the potential for repeat interventions and the risk of further disease progression.

In addition to the ongoing Phase 1 studies in PAD, Proteon is currently conducting two Phase 3, multicenter, randomized, double-blind, placebo-controlled clinical studies evaluating vonapanitase in patients with chronic kidney disease (CKD) undergoing surgical creation of an arteriovenous fistula for hemodialysis vascular access. Proteon expects to release top-line data from the first Phase 3 study, PATENCY-1, in December 2016.

About Peripheral Artery Disease (PAD)

Patients with peripheral artery disease (PAD) of the lower extremities experience stenosis, or blockage, in the arteries providing blood to the legs. These patients typically present with exercise-induced leg pain, a condition known as intermittent claudication. Symptoms of claudication include impaired walking function as patients quickly experience leg pain that can be resolved only through rest. In advanced cases of PAD, known as critical limb ischemia, a severe lack of blood flow causes leg pain at rest, which can result in gangrene or tissue death and the need for amputation. Current revascularization procedures to address PAD are often ineffective and lack durability, resulting in ongoing suffering for patients. PAD is a global problem affecting a large and growing number of people in developed and developing countries. An estimated eight to twelve million Americans are affected by PAD.

About Vonapanitase

Vonapanitase (formerly PRT-201) is an investigational drug designed to treat vessel injury response that leads to blockages in blood vessels and reduced blood flow. Vonapanitase is applied in a single administration and is currently being studied in two Phase 3 clinical trials, PATENCY-1 and PATENCY-2, in patients with chronic kidney disease (CKD) undergoing surgical creation of a radiocephalic arteriovenous fistula (AVF) for hemodialysis, and two Phase 1 clinical trials in patients with peripheral artery disease (PAD). Vonapanitase has received fast track and orphan drug designations from the U.S. Food and Drug Administration (FDA), and orphan medicinal product designation from the European Commission, for hemodialysis vascular access indications.

About Proteon Therapeutics

Proteon Therapeutics is committed to improving the health of patients with kidney and vascular diseases through the development of novel, first-in-class therapeutics. Proteon’s lead product candidate, vonapanitase, is an investigational drug intended to improve arteriovenous fistula (AVF) patency, the period of time during which an AVF remains open with adequate blood flow to enable hemodialysis. Proteon is currently evaluating vonapanitase in two Phase 3 clinical trials, PATENCY-1 and PATENCY-2, in patients with chronic kidney disease (CKD) undergoing surgical creation of a radiocephalic AVF for hemodialysis, and two Phase 1 clinical trials in patients with peripheral artery disease (PAD). For more information, please visit www.proteontherapeutics.com.

Cautionary Note Regarding Forward-Looking Statements

This press release contains statements that are, or may be deemed to be, “forward-looking statements.” In some cases these forward-looking statements can be identified by the use of forward-looking terminology, including the terms “estimates,” “anticipates,” “expects,” “plans,” “intends,” “may,” or “will,” in each case, their negatives or other variations thereon or comparable terminology, although not all forward-looking statements contain these words. These statements, including when the Company expects to report top-line data from the PATENCY-1 Phase 3 clinical study, the number of patients to be enrolled in the Phase 1 clinical studies of vonapanitase in patients with PAD, the potential surgical and endovascular applications or routes of administration for vonapanitase, the potential treatment of renal and vascular diseases, including PAD, with vonapanitase, the effect of vonapanitase in patients with CKD or PAD, whether vonapanitase improves AVF patency, whether vonapanitase improves the durability of treatment for PAD or reduces the symptoms of PAD, and those relating to future events or our future financial performance or condition, involve substantial known and unknown risks, uncertainties and other important factors that may cause our actual results, levels of activity, performance or achievements to differ materially from those expressed or implied by these forward-looking statements. These risks, uncertainties and other factors, including whether our cash resources will be sufficient to fund our operating expenses and capital expenditure requirements for the period anticipated; whether data from early nonclinical or clinical studies will be indicative of the data that will be obtained from future clinical trials; whether vonapanitase will advance through the clinical trial process on the anticipated timeline and warrant submission for regulatory approval; whether such a submission would receive approval from the Food and Drug Administration or equivalent foreign regulatory agencies on a timely basis or at all; and whether we can successfully commercialize and market our product candidates, are described more fully in our Annual Report on Form 10-K for the year ended December 31, 2015, as filed with the Securities and Exchange Commission (“SEC”) on March 14, 2016, and our subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, as filed with the SEC, particularly in the sections titled “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations.” In light of the significant uncertainties in our forward-looking statements, you should not place undue reliance on these statements or regard these statements as a representation or warranty by us or any other person that we will achieve our objectives and plans in any specified time frame, or at all. The

forward-looking statements contained in this press release represent our estimates and assumptions only as of the date of this press release and, except as required by law, we undertake no obligation to update or revise publicly any forward-looking statements, whether as a result of new information, future events or otherwise after the date of this press release.

Investor Relations Contact

George Eldridge, Proteon Therapeutics, Senior Vice President and Chief Financial Officer 781-890-0102
[email protected]

Media Contact

Cara Mayfield, Ten Bridge Communications 857-242-1872 [email protected]