Proteostasis shares zoom north as their cystic fibrosis doublet causes a stir in small study — triggering an online brawl

Sometimes it’s the smallest studies that gain the biggest reactions from the investment crowd that follows biotech.

Case in point: Little Proteostasis Therapeutics hit big-time pay dirt on Thursday, watching its stock $PTI swoop up 448% on some intriguing early data on a handful of patients suffering from cystic fibrosis.

Meenu Chhabra, CEO

Breaking 21 patients homozygous for the F508del mutation into various dose groups for their CF doublet therapy, researchers teased out some significant results for the few people in the high dose cohort that was evaluable at the time of the Phase I cutoff for their readout.

For the 300 mg ppFEV1 cohort there was a statistically significant increase from baseline to day 7 of 6.3%, which registered as a 5.9% increase on day 14. Compared to a placebo, the same PTI-801 300 mg/PTI-808 300 mg cohort hit +8.3% and +6.6% at 7 and 14 days. They added that they also tracked a statistically significant decrease in sweat chloride concentration from baseline.

There’s another 400 mg cohort that’s being tracked now, with a triplet to follow.

The kicker is here:

“The current improvement in ppFEV1 for standard of care doublets is on average 3%-4% in the F508del homozygous patient population,” said Damian Downey, a lecturer in respiratory medicine at Queen’s University Belfast.

The numbers got a close review by analysts in the field. Leerink’s Joseph Schwartz noted Proteostasis’ mixed results as an add-on for Orkambi, from Vertex. But, he added, “PTI’s own proprietary combo bodes well in our view for preliminary triplet data expected this quarter.”

Baird’s Brian Skorney also gave the data a thumbs up as an indicator of the potential of the triple:

The combo of PTI-808 and PTI-801 showed initial FEV1 results that are comparable to Vertex’s Orkambi and Symdeko in cystic fibrosis patients. Although we believe this combo would have a difficult development pathway, given the availability of the Vertex doublets, we do believe it creates an opportunity for it to develop its amplifier, PTI-428, in a proprietary triple combination. We will see initial triple combo data this quarter that we believe will be a significant positive catalyst for the stock.

Vertex stock dropped 3.5%, which triggered a defensive scrum on Twitter as some of the company’s defenders turned ugly on the pressure. So far, Vertex has stared down repeated challenges to its frontrunner status. But it didn’t get off so lightly on this run.

Proteostasis’ KOLs, meanwhile, will continue to talk up their new-found status in CF.

”Doublet combinations, the current standard of care for many CF patients, are the benchmark for current treatment in cystic fibrosis.  These data are the first results seen using an entirely new CF doublet, compare favorably to standard of care, and demonstrate the potential of next-generation CFTR modulators to further improve outcomes in this disease,” said Carsten Schwarz, head of the Adult Cystic Fibrosis Centre, Lung-Transplantation Program, and Endoscopy Unit, Department of Pediatric Pneumology and Immunology, Charité, Berlin University Medical Center. “I look forward to results from the fourth dosing cohort and to understanding the potential of another novel combination, PTI-801, PTI-808 and PTI-428.”

Researchers will be adding more data this quarter and in early 2019.

The fighting has just begun.

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