Calistoga Pharmaceuticals has been stirring up buzz at medical meetings for more than a year about how its experimental treatment is shrinking tumors for patients with certain blood cancers that resist other therapies. And today the Seattle-based company is showing still more evidence that strengthens the medical case for its drug, as the tumor shrinkage effect appears to be long-lasting, and the drug looks like it can be safely combined with other standard meds.
The latest data about Calistoga’s experimental drug, CAL-101, is being presented today at the American Society of Hematology meeting in Orlando, FL. The main study has been expanded over time to include 177 patients, and has been adjusted since it started in June 2008 to now focus primarily where it appears to be most effective: patients with chronic lymphocytic leukemia and slow-growing or “indolent” non-Hodgkin’s lymphoma. Even after patients saw their disease worsen following multiple rounds of treatment, the Calistoga drug kept their tumors from spreading for more than a year, researchers said. And an early look at a second study of the Calistoga therapy said it didn’t appear to add any extra side effects when combined with standard drugs like Cephalon’s bendamustine (Treanda) or Roche and Biogen Idec’s rituximab (Rituxan).
“As we’ve added more and more numbers of patients, you can see it’s not a statistical fluke,” says Carol Gallagher, Calistoga’s CEO. “The response rates we are seeing are real, and so is the duration of response.”
Calistoga, which raised its first sizable venture round in 2007, has been emerging for some time now as one of the top private biotech companies in Seattle. The company has attracted another $70 million in venture capital over the past 18 months to drive the development of this drug, which is seeking to attack cancer through a hot avenue known as the PI3 kinase pathway. Scientists are excited about this pathway because it is thought to control critical cell processes like proliferation, migration, and cell survival. When these normal functions get flipped into an overactive mode, it’s a hallmark of cancer cells growing out of control.
Pharma heavyweights like GlaxoSmithKline, Novartis, and Sanofi-Aventis are pursuing this strategy, yet Calistoga is seeking to differentiate itself by aiming for more specific types of PI3 kinase, particularly one known as the delta isoform. By being more specific, it hopes to be more potent against particular blood cancers that overexpress the delta isoform, and minimize side effects.
Calistoga’s first study enrolled a wide variety of patients with blood cancers. More than half of them had relapsed or didn’t respond any more to existing therapies. Without receiving any other combination treatments, people in the study took CAL-101, a twice-daily oral pill, for a 28-day course of therapy, for as many as 12 cycles. Researchers enrolled patients with five different kinds of malignancies in this study, looking for signs in which CAL-101 showed the most promise.
The strongest evidence over time appears to be for two forms of blood cancers—chronic lymphocytic leukemia, and slow-growing “indolent” non-Hodgkin’s lymphoma.
First, here’s what is known about chronic lymphocytic leukemia. There were 54 patients
