Sophiris Bio Inc. (NASDAQ: SPHS) (the “Company” or “Sophiris”), a biopharmaceutical company developing PRX302 (topsalysin) for the treatment of urological diseases, today announced that the first patients have been dosed in a Phase 2a proof of concept trial of PRX302 as a treatment for localized low to intermediate risk prostate cancer.

“The highly targeted treatment with PRX302, which selectively destroys prostate tissue, makes PRX302 a promising treatment approach for localized prostate cancer,” stated Professor Mark Emberton, Director of the Division of Surgery and Urologist at University College London.

“This new trial is very exciting. PRX302 has the potential to provide patients with clinically significant, localized low to intermediate risk prostate cancer a tissue-sparing cancer treatment that carries little in the way of side effects,” said Dr. Hashim Ahmed, Principal Investigator for the study, Division of Surgery and Interventional Sciences, University College London.

The Phase 2a proof of concept study is a single-center, open-label study that will enroll approximately 20 patients. Previously obtained multi-parametric magnetic resonance imaging (mpMRI) of tumor lesions in each patient’s prostate, mapped to real-time three-dimensional transrectal ultrasound (TRUS), will be used in the study to guide the injection of PRX302 to treat a single, histological-proven, clinically significant lesion area in each patient’s prostate. Although the primary objective of the study is safety and tolerability, the key efficacy variable is the change in the treated clinically significant lesion on biopsy after six months.

“PRX302 is a novel targeted approach for the treatment of clinically significant, localized prostate cancer that is still confined within the prostate gland,” said Allison Hulme, Ph.D., chief operating officer and head of R&D at Sophiris. “PRX302 has been engineered to be activated only by enzymatically active prostate specific antigen (PSA) which is present only in prostate tissue, including the transition zone of the prostate as well as prostate cancer cells. PRX302 can be focally delivered by an intraprostatic injection directly into and around the tumors within the prostate where there are high levels of enzymatically active PSA to activate the drug.”

PRX302 for the Targeted Treatment of Localized Prostate Cancer

PRX302 has the potential to provide a focal targeted therapy for the ablation of localized prostate cancer while potentially avoiding many of the complications and side effects associated with whole gland radical treatments. The increasing use of multi-parametric magnetic resonance imaging (mpMRI) and advances in mapping previously obtained mpMRI images with live 3D ultrasound images enable the physician to more accurately locate tumors within the prostate when taking biopsies. This increases the accuracy with which men with clinically significant lesions are identified. It also enables the injection of PRX302 directly into previously identified clinically significant tumors located within the prostate. The targeted focal treatment of prostate cancer is in line with current treatments for solid tumors, such as breast or liver, where the goal is to remove the tumor and preserve as much of the organ as possible.

About Localized Prostate Cancer

Prostate cancer is the second most common form of cancer in men in the US with an estimated 220,800 new cases in 2015. Approximately 80% of patients in the US are diagnosed with localized disease. Research has shown that patients with early localized disease have a low likelihood of the cancer spreading beyond the confines of the prostate; however, men with clinically significant, localized disease choose to undergo radical therapies. Radical therapies include surgery to remove the entire prostate and/or radiation. Potential toxicities from radical treatments can be significant and permanent and include erectile dysfunction, incontinence and rectal toxicity.

About Sophiris

Sophiris Bio Inc. is a biopharmaceutical company developing PRX302, a clinical-stage, targeted therapy for the treatment of urological diseases. PRX302 is in Phase 3 clinical development for the treatment of the symptoms of benign prostatic hyperplasia (BPH) and is designed to be as efficacious as pharmaceuticals, less invasive than the surgical interventions, and without the sexual side effects seen with existing treatments. PRX302 is also currently in a Phase 2a proof of concept study for the treatment of localized low to intermediate risk prostate cancer. For more information, please visit www.sophiris.com.

Certain statements included in this press release may be considered forward looking, including any expectations relating to the results of Sophiris’ Phase 3 clinical trial of PRX302 for BPH and the Phase 2a proof of concept trial for the treatment of localized low to intermediate risk prostate cancer and expectations about efficacy of PRX302, the timing of receipt of data from the proof of concept study or Sophiris’ capital requirements. Such statements involve known and unknown risks, uncertainties and other factors that may cause actual results, performance or achievements to be materially different from those implied by such statements, and therefore these statements should not be read as guarantees of future performance or results. Some of the risks and uncertainties that could cause actual results, performance or achievements to differ include without limitation, risk associated with the process of developing, manufacturing commercial scale drug products, obtaining regulatory approval of and commercializing treatments that are safe and effective, and in the endeavor of building a business around such treatments. All forward-looking statements are based on Sophiris’ current beliefs as well as assumptions made by and information currently available to Sophiris and relate to, among other things, anticipated financial performance, business prospects, strategies, regulatory developments, clinical trial results, market acceptance, ability to raise capital and future commitments. Readers are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date of this press release. Due to risks and uncertainties, including the risks and uncertainties identified by Sophiris in its public securities filings; actual events may differ materially from current expectations. Sophiris disclaims any intention or obligation to update or revise any forward-looking statements, whether as a result of new information, future events or otherwise.