Proteon tanks after kidney disease drug fails again in phase 3

Kidney care
Proteon expects to have $16.5 million in cash and sellable investments as of the end of the month. (Getty/Trish233)

Proteon Therapeutics has failed another phase 3 chronic kidney disease trial. The latest failure raised significant doubts about the future of vonapanitase, wiping 85% off Proteon’s stock price and leaving the company to consider strategic alternatives. 

Vonapanitase is a recombinant human elastase Proteon moved into phase 3 in the belief it improves fistula outcomes in patients undergoing or preparing for hemodialysis. That belief, which Proteon held despite not knowing vonapanitase’s mechanism of action, took a hit when the drug failed the first phase 3 late in 2016. 

Proteon responded by revising the statistical plan of the second trial, increasing the target patient enrollment and raising cash to execute the strategy. The changes had little effect on the outcomes.

Vonapanitase failed to beat placebo against the co-primary endpoints in the second trial. Patients who received a single dose of vonapanitase were no more likely to achieve the use of a fistula than their peers on placebo. And their fistulas lasted no longer than those in the control arm. The study missed another efficacy endpoint, too.

The findings quash hopes raised by a secondary endpoint of the original phase 3, leaving the fate of vonapanitase and Proteon itself in doubt. Proteon said it will evaluate the results and its strategic alternatives over the coming weeks. 

Management may struggle to identify encouraging paths forward for the company. Proteon expects to have $16.5 million in cash and sellable investments by the end of the month. And the list of people and businesses interested in funding further work on a twice-failed asset is likely to be short. Proteon is testing vonapanitase in peripheral artery disease but lacks a pipeline beyond the asset.

The release to disclose the latest phase 3 is lacking the glimmer of hope that encouraged Proteon to push on after the first clinical failure, suggesting that the program may have reached the end of the road.