Proteon Therapeutics Inc. (NASDAQ: PRTO) saw its shares absolutely crater on Tuesday after the company reported top-line results from its late-stage chronic kidney disease (CKD) trial. The company announced that its first Phase 3 clinical trial with investigational vonapanitase, Patency-1, did not meet its primary endpoint of improved primary unassisted patency compared to placebo.

However, the top-line results for the trial’s secondary endpoint suggested that vonapanitase may improve secondary patency compared to placebo. Also data from one of the trial’s three tertiary endpoints suggested vonapanitase may improve unassisted fistula use for hemodialysis.

The trial’s primary endpoint, primary unassisted patency, is the length of time from fistula surgical creation to the first occurrence of a fistula thrombosis or corrective procedure to restore or maintain patency (blood flow). Vonapanitase-treated patients had a 17% reduction in the risk of primary unassisted patency loss over one year, compared to the placebo. At the end of one year, 42% of patients who received vonapanitase retained primary unassisted patency, compared to 31% of the placebo-treated patients.

In terms of the secondary endpoint, at the end of one year, 74% of vonapanitase-treated patients maintained secondary patency, compared to 61% of placebo-treated patients.

The adverse effects were relatively similar between the vonapanitase-treated patients and the placebo-treated patients. The most common adverse effects were consistent with medical events experienced by CKD patients undergoing radiocephalic fistula surgery.

Steven Burke, M.D., senior vice president and chief medical officer of Proteon Therapeutics, commented:

We are disappointed that the study missed the primary endpoint. However, it appears that vonapanitase had a drug effect and we are encouraged by the secondary patency and fistula use for hemodialysis findings in this trial, both of which we believe are clinically important. We plan to review the full data set from PATENCY-1 and further investigate these findings in our ongoing Phase 3 clinical trial, PATENCY-2.

Shares of Proteon were trading down about 73% at $2.70 on Tuesday, with a consensus analyst price target of $20.43 and a 52-week trading range of $2.60 to $16.48.

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