Proteon triggers a stock implosion as its first PhIII proves to be a bust

Steven Burke, Proteon

Steven Burke, Proteon

This morning it was Proteon Therapeutics’ $PRTO turn to join the queue of small biotechs to step on a land mine.

The Waltham, MA-based biotech’s shares cratered, plunging 70% in pre-market trading after the biotech reported that their Phase III trial of vonapanitase (which used to be called PRT-201) failed the primary endpoint on reducing the risk of what’s called primary unassisted patency — the length of time from fistula surgical creation to the first occurrence of a fistula thrombosis or corrective procedure to restore blood flow.

The drug was developed to help patients with chronic kidney disease maintain an open fistula to allow adequate blood flow needed for hemodialysis.

The researchers zeroed in on signs of drug activity, noting a 17% risk reduction on the primary endpoint and so-called suggestions that the drug was working for secondary patency, the time to final failure. And the company will look for some vindication in an ongoing Phase III trial. But quite a few investors don’t appear ready to hang on for Round II.

More than 300 patients were enrolled in the first Phase III trial.

The micro cap ended Monday with a market cap of $164 million, which largely went up in smoke.

“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,” said Steven Burke, MD, Senior Vice President and Chief Medical Officer of Proteon Therapeutics. “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.”

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