Protagonist cans ulcerative colitis trial after flunking interim review 

Histopathological image of the active stage of ulcerative colitis. (KGH/GFDL)

Protagonist Therapeutics has scrapped a phase 2b ulcerative colitis trial of its lead program PTG-100. The oral alpha-4-beta-7 integrin antagonist peptide performed badly enough in the first 65 patients for a data monitoring committee to rule it would be futile to continue.

Newark, California-based Protagonist has built its pipeline—and landed a deal with Johnson & Johnson—on a technology platform designed to discover oral peptides. The platform gained preliminary validation in 2016 when a phase 1 trial of PTG-100 demonstrated dose-dependent pharmacodynamic activity. But now the program has failed at the first hurdle in phase 2.

The data monitoring committee ruled that PTG-100 was destined to fail after seeing data on the first 65 patients in a planned 240-subject trial. Protagonist has yet to share a look at the data but pointed to an “unexpectedly high placebo rate” in its explanation of what happened.


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Management is now assessing the full data set before deciding on a path forward, but the picture for the asset looks bleak. Protagonist has halted enrollment in the phase 2 and asked investigators to stop dosing patients who are already in the trial. The company has also hit pause on its plans to run a phase 2/3 trial of PTG-100 in chronic pouchitis.

It is possible the chronic pouchitis trial could survive the setback in ulcerative colitis, but as it stands there looks to be a chance that this is the end of the line for PTG-100. That would make PTG-300, an injectable iron overload treatment that came through phase 1 last year, Protagonist’s most advanced wholly owned asset.

The wipeout of PTG-100 may also dampen expectations for PTG-200, the oral IL-23R candidate J&J secured rights to last year for $50 million upfront and $940 million in milestones. That drug has a different—and widely researched—target than PTG-100 but is the fruit of the same platform as its more advanced sibling.   

Shares in Protagonist fell 60% in early morning trading.

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