Sophiris Bio Inc. announced final results from its Phase 3 "PLUS-1" study of PRX302 as a treatment for lower urinary tract symptoms of benign prostatic hyperplasia (BPH, enlarged prostate). PRX302 demonstrated a statistically significant improvement in International Prostate Symptom Score (IPSS) total score from baseline over 12 months compared to the vehicle-only control group (7.60 vs. 6.58 point overall improvement; p = 0.043), the primary endpoint of the study.

PRX302 continues to demonstrate a favorable safety profile, with no evidence of any treatment related sexual or cardiovascular side effects. The primary efficacy endpoint of the IPSS total score change from baseline over 52 weeks was analyzed, per guidance from the FDA, using the repeated measures linear mixed model applied to the modified intent-to-treat population of every patient randomized and dosed with study drug. The 7.60-point overall improvement for the PRX302 group was statistically significantly superior to the 6.58 point improvement in the vehicle-only group (p = 0.043).

In a secondary efficacy analysis of IPSS total score using an ANCOVA model and LOCF (Last Observation Carried Forward) to impute missing post-baseline data, the improvement in IPSS for PRX302 was well sustained over the 52 weeks following the single administration. The maximal effect of 8.31 points improvement in IPSS vs vehicle 6.89 points (p = 0.012) was achieved at Week 18 with 8.04 points of improvement for PRX302 still remaining at Week 52 vs 6.64 points for patients treated with vehicle only (p = 0.022) representing an end-of-study preservation of 97% of the peak benefit. Secondary efficacy endpoints included analysis of Qmax (maximum urine flow) change from baseline over 52 weeks by the repeated measures linear mixed model, which showed overall improvement of 1.77 mL/sec for PRX302, representing a statistical trend that narrowly missed statistical significance(p = 0.055) compared to the vehicle group.

An additional efficacy endpoint was the patient self-assessment of disease specific Quality of Life. On the 0 to 6 point Quality of Life (QOL) from the IPSS questionnaire, the PRX302 average change from the 4.5 point baseline was a sustained 1.6 to 1.7 points improvement from Weeks 18 through 52, which was statistically significantly superior to vehicle for every post-baseline visit beginning at Week 18 (reaching p = 0.004). PRX302 treatment was generally well-tolerated, and no patient was withdrawn from the study or had their study drug injection altered because of an adverse event (AE).

The safety profile was consistent with that reported in the TRIUMPH Phase 2 trial published in the Journal of Urology in April 2013. Adverse events occurring in >5% of patients treated with PRX302 regardless of assessed relatedness to study treatment are set out. These adverse events are not unexpected manifestations of the intraprostatic cellular destruction and resultant inflammation integral to the PRX302 mechanism of action.

The median duration for each of these adverse events was typically less than one day. In general, these adverse events were mild or moderate, transient, began within the first few days after treatment (primarily on the same day as the study drug injection) and were resolved without consequences.