Celladon Corporation, a clinical-stage biotechnology company developing novel therapies for patients with heart failure and other diseases characterized by SERCA enzyme deficiencies, announced that its lead product candidate, MYDICAR, has been granted breakthrough therapy designation by the US Food and Drug Administration (US FDA) for reducing hospitalisations for heart failure in NYHA class III or IV chronic heart failure patients who are NAb negative.

This designation is intended to expedite the development and review of drugs for serious or life-threatening conditions and where preliminary clinical evidence suggests it provides a substantial improvement over existing therapies.

Celladon is developing MYDICAR as a novel, first-in-class therapy for patients with chronic heart failure due to systolic dysfunction. MYDICAR uses genetic enzyme replacement therapy to correct the deficiency in the enzyme SERCA2a, which is an enzyme that becomes deficient in heart failure patients and results in inadequate pumping of the heart. Celladon has developed a companion diagnostic to identify the patients who are AAV1 NAb negative and therefore eligible for MYDICAR treatment.

"We are looking forward to working with the senior staff at the FDA to determine the most expeditious path to bring MYDICAR to patients with advanced heart failure. This breakthrough therapy designation validates MYDICAR's unique characteristics and clinical data to date and underscores the urgent need for new treatments for heart failure," said Krisztina Zsebo, Ph.D., president and chief executive officer of Celladon. "MYDICAR has the potential to provide transformative disease-modifying effects with long-term benefits in heart failure patients with a single administration. Our goal is to bring MYDICAR to market as quickly as possible in the United States, where we estimate approximately 350,000 heart failure patients with currently limited remaining treatment options could be eligible for therapy."

Celladon is currently evaluating MYDICAR in the Phase 2b CUPID 2 trial to determine its efficacy in reducing the frequency of and/or delaying heart failure-related hospitalisations. This randomized, double-blind, placebo-controlled, multinational trial is evaluating a single intracoronary infusion of MYDICAR versus placebo added to a maximal, optimised heart failure regimen in patients with NYHA class III or IV symptoms of chronic heart failure due to systolic dysfunction. Patient enrollment has been completed and 250 patients have been randomised in this trial. The company expects to report results in April 2015.

The breakthrough therapy designation was enacted as part of the FDA Safety and Innovation Act of 2012 (FDASIA). The breakthrough therapy programme is intended to streamline drug development and review of innovative new medicines that address certain unmet medical needs for serious or life-threatening diseases or conditions. The criteria for breakthrough therapy designation require preliminary clinical evidence indicating that the drug may demonstrate a substantial improvement over existing therapies on at least one clinically significant endpoint.

A breakthrough therapy designation conveys all of the fast track programme features, as well as a commitment that FDA will work closely with the drug sponsor on an efficient drug development program. The statute calls for reducing exposure of patients to a potentially less-effective active control drug. However, FDA intends to expedite the development and review of a breakthrough therapy by intensively involving senior managers and experienced review staff in a proactive, collaborative, cross-disciplinary review.

MYDICAR uses gene therapy to selectively target and restore SERCA2a enzyme levels by transferring the SERCA2a gene directly into cardiac muscle cells, which improves the heart's ability to pump blood.

MYDICAR utilises a non-pathogenic recombinant adeno-associated virus (AAV) and is delivered directly to the heart in a routine outpatient procedure, similar to an angiogram, in a cardiac catheterisation laboratory.

Results of the 39-patient Phase 2a CUPID 1 clinical trial of a single intracoronary infusion of high-dose MYDICAR in patients with advanced heart failure due to a systolic dysfunction showed the therapy was safe and well tolerated in the study. In CUPID 1, MYDICAR reduced heart failure-related hospitalizations and improved patients' symptoms, quality of life and key markers of cardiac function predictive of survival, such as elevated levels of natriuretic peptides and left ventricular end systolic volume.

Long-term follow-up results from CUPID 1 showed that in the additional two-year follow-up period, the durability of reduced cardiovascular and terminal events previously observed in the MYDICAR high-dose cohort at 12 months was maintained.

The risk of recurrent cardiovascular events in the presence of terminal events over three years of follow up was reduced by 82 per cent in the high-dose group compared with the placebo group (p=0.048). No safety concerns were noted during the three-year follow-up period for patients who received MYDICAR.