UPDATED: Celladon shares blasted as gene therapy for heart failure bombs in PhIIb

Celladon CEO Krisztina Zsebo

Celladon's lead program--as well as its stock price--crashed after the biotech ($CLDN) announced Sunday evening that its heart therapy Mydicar failed the primary and secondary endpoints in a Phase IIb trial, losing out in a full lineup of efficacy tests. Its shares were routed in premarket trading, dropping 78% as analysts and investors considered the implications.

A year ago, the FDA handed out "breakthrough" status for Celladon's Mydicar, a gene therapy designed to insert a functioning copy of the SERCA2a gene into heart cells in an effort to salvage declining hearts and improve pumping power. That helped direct the stock into the stratosphere a month ago, but shares have since fallen by half as Celladon got closer to revealing the crucial outcome.

The primary endpoint was an improvement in heart failure-related hospitalizations or ambulatory treatment for worsening heart failure with a secondary endpoint comparing Mydicar to a placebo for all-cause death, need for a mechanical circulatory support device, or heart transplant.

"We are surprised and very disappointed that Mydicar failed to meet the endpoints in the CUPID2 trial, and we are rigorously analyzing the data in an attempt to better understand the observed outcome," said Krisztina Zsebo, the CEO of San Diego-based Celladon. "At the same time we are evaluating our other programs in order to determine the best path forward to maximize shareholder value."

At the time Celladon achieved the breakthrough designation last year, Zsebo told FierceBiotech that a Phase III follow-up could well be an expected requirement at the FDA, while the EMA might well go ahead with an approval based on positive Phase IIb CUPID-2 results. But that's all academic now. At this juncture, the biotech has to figure out how to reorganize and push forward in the face of a stinging setback.

Celladon was tapped as a 2012 Fierce 15 company after a trio of Big Pharma companies--Pfizer ($PFE), Novartis ($NVS) and Johnson & Johnson ($JNJ)--all backed a $53 million round to fund the Phase IIb trial.

The company struck a partnership with Servier to collaborate on a SERCA2b approach that could also work for heart disease, diabetes and neurodegenerative diseases.

- here's the release

Special Report: FierceBiotech's 2012 Fierce 15 - Celladon

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