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Proteon Therapeutics Announces Publication in the Journal of Cardiovascular Pharmacology of Promising Nonclinical Results for Vonapanitase in Peripheral Artery Disease
Initiation of Two Phase 1 Clinical Trials of Vonapanitase in PAD Expected in 2016

WALTHAM, Mass., April 13, 2016 (GLOBE NEWSWIRE) -- Proteon Therapeutics Inc. (Nasdaq:PRTO), a company developing novel, first-in-class pharmaceuticals to address the medical needs of patients with kidney and vascular diseases, today announced publication of additional nonclinical data on investigational drug vonapanitase in peripheral artery disease (PAD). The ex vivo study demonstrated that a single treatment of vonapanitase following angioplasty of excised atherosclerotic human tibial arteries altered artery compliance. Increased compliance is known to correlate with arterial dilation.

The study, titled "Recombinant Human Elastase Alters the Compliance of Atherosclerotic Tibial Arteries After Ex Vivo Angioplasty", was published in the Journal of Cardiovascular Pharmacology. Proteon's Senior Vice President and Chief Medical Officer, Steven Burke, M.D., is the senior author of the published manuscript.

PAD is often caused by atherosclerosis and can frequently occur in the tibial arteries, which are located below the knee and supply blood to the lower leg and foot. This study was designed to compare the effects of vonapanitase and placebo on excised atherosclerotic human tibial arteries following ex vivo angioplasty. Assessments included elastin content in the arterial wall and arterial compliance, which is a measure of an artery's ability to expand with changes in blood pressure. Data from the study demonstrated that vonapanitase treatment ex vivo reduced elastin content by 60% compared to placebo and altered arterial compliance. Increased compliance is known to correlate with arterial dilation.

"Current interventional treatments for patients with PAD below the knee, such as balloon angioplasty, lack durability," said Timothy Noyes, President and Chief Executive Officer of Proteon. "These data published in the Journal of Cardiovascular Pharmacology support our hypothesis that a single, local administration of vonapanitase may augment the effects of balloon angioplasty through enhanced artery dilation."

This study supports other clinical and nonclinical results evaluating the potential use of vonapanitase in PAD. Proteon announced in August of 2015 the completion of a Phase 1 PAD clinical study indicating that catheter-based administration of vonapanitase using the Mercator MedSystems Bullfrog® Micro-Infusion Device to the superficial femoral or popliteal artery following angioplasty was generally well tolerated and technically feasible. Proteon announced in January of 2015 the publication of nonclinical data demonstrating that vonapanitase treatment of atherosclerotic human tibial arteries ex vivo without prior angioplasty resulted in an increase in artery diameter.

Based on these data and other nonclinical results, Proteon expects to initiate two Phase 1 clinical studies in PAD in 2016. Proteon is also currently conducting two Phase 3 multicenter, randomized, double-blind, placebo-controlled clinical studies of vonapanitase in patients with chronic kidney disease (CKD) undergoing surgical creation an arteriovenous fistula (AVF) for hemodialysis vascular access. Data from the first Phase 3 study is expected in December of 2016.

About Peripheral Arterial Disease
Peripheral artery disease (PAD) is characterized by atherosclerosis in the arteries of the legs, which leads to poor blood flow. Patients with PAD may experience muscle pain during walking, suffer from ulcers that are slow to heal or, in the most severe cases, require amputation. PAD affects eight million Americans and is a significant cause of both morbidity and mortality (source: American Heart Association).

About Vonapanitase
Vonapanitase (formerly PRT-201) 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. Vonapanitase is applied in a single administration and is currently being studied in two Phase 3 clinical trials in patients with chronic kidney disease (CKD) undergoing surgical creation of a radiocephalic AVF for hemodialysis. 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. Vonapanitase may have multiple surgical and endovascular applications in which vessel injury leads to blockages in blood vessels and reduced blood flow, and has completed a Phase 1 clinical trial in patients with symptomatic peripheral artery disease (PAD).

About Proteon Therapeutics
Proteon Therapeutics Inc. is developing novel, first-in-class pharmaceuticals to address the medical needs of patients with kidney and vascular diseases. The company is headquartered in Waltham, Mass. For additional 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 "believes," "estimates," "anticipates," "expects," "plans," "intends," "may," "could," "might," "will," "should," "approximately," "potential," or, in each case, their negatives or other variations thereon or comparable terminology, although not all forward-looking statements contain these words. These statements, including those regarding the potential surgical and endovascular applications for PRT-201, the expected timing of the Phase 1 studies in PAD, the potential treatment of renal and vascular diseases with PRT-201, the effect of PRT-201 in patients with CKD, 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 the our operating expenses and capital expenditure requirements for the period anticipated; whether data from early clinical trials will be indicative of the data that will be obtained from future clinical trials; whether PRT-201 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 on March 14, 2016, 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.

Company Contact
George Eldridge, Senior Vice President and Chief Financial Officer
781-890-0102
geldridge@proteontherapeutics.com

Media Contact
Chris Erdman, MacDougall Biomedical Communications
781-235-3060
proteon@macbiocom.com

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