is thread through a large artery in the thigh. The theory is that heart cells will take up the gene, which revamps the cell machinery to produce increased amounts of the enzyme, improving the heart’s ability to contract.
Last month, Celladon published results of an early-stage trial of nine patients in the Journal of Cardiac Failure. The study reported no significant safety issues and found that six months after treatment five patients had improved symptoms and increased left ventricular function. The left ventricle is the chamber of the heart that pumps blood to the body and is typically impaired in heart failure patients. Two patients with low levels of pre-existing antibodies showed no improvement.
Celladon has enrolled 20 of an anticipated total of 37 patients in a mid-stage trial; results are expected by early 2010. The trial is for people with advanced heart failure – those who become winded performing routine activities, like getting up to answer the phone. Zsebo said such patients are “on the trajectory” for a heart transplant or for receiving a left ventricular assist device, an implantable mechanical heart pump. About 1.5 million Americans have advanced heart failure.
The potential market for the drug could be half that number, however. UC San Diego cardiologist and Celladon adviser Howard Dittrich said half of the patients recruited for the mid-stage trial were rejected because they had low levels of antibodies to the virus, and scientists have concluded the gene therapy won’t work for them. This could mean that 50 percent of people with advanced heart failure won’t be eligible for Celladon’s drug.
Celladon, with five employees and 10 contract workers, has enough money to complete the mid-stage study and fund the company through completion of a partnering transaction, Zsebo said. Celladon was spun out of the UC San Diego incubator in 1994.
At the meeting this week, Zsebo shared some of the scientific lessons the company has learned working on its gene therapy, called Mydicar.
One myth Zsebo hoped to put to rest was the notion that gene therapy can’t be safely administered through the bloodstream. The worry was that the gene would end up organs where it didn’t belong and cause havoc. But Celladon found that wasn’t the case. The immune system ultimately eliminated the virus from the body, Zsebo said, and the SERCA2a gene was not expressed in cells outside the heart.