Seattle-based Calistoga Pharmaceuticals has gathered more evidence that it may have a real drug for blood cancers, which is shrinking tumors in patients without killing too many other healthy cells in the blood.
The drug, CAL-101, didn’t work for everybody, but it did cause tumors to shrink at least by half for 60 percent of patients with a slow-growing malignancy called indolent non-Hodgkin’s lymphoma, researchers reported today at the American Society of Hematology (ASH) annual meeting in New Orleans. That result was based on 9 out of 15 patients, who were part of a wider study that included 57 patients with a variety of different malignancies.
The new findings are the latest step forward for Calistoga, as it has emerged on the national scene this year. The privately held company raised $30 million in venture capital in May from Frazier Healthcare Ventures, Alta Partners, Three Arch Partners, and Amgen Ventures to pursue drugs that block one of the hot targets of the moment in cancer biology—the PI3 kinase pathway. A few weeks after raising the cash, Calistoga reported interim results at a pair of cancer meetings that showed its drug was causing tumor shrinkage in about half of the first 24 evaluated patients, even at less than ideal doses.
The company has been so encouraged by the early results that it is planning for the next step of clinical trials, to start in the middle of 2010, that could provide the basis for an application to the FDA for clearance to start selling CAL-101 in the U.S.
“Certainly we still have to see the duration of the data, and it’s still early days,” says CEO Carol Gallagher, who was attending the ASH meeting in New Orleans. “But we’re hearing the investigators talk, and it’s rewarding to hear them tell some dramatic stories.”
One of the researchers on the CAL-101 study, Ian Flinn of Sarah Cannon Research Institute in Nashville, TN, said in a Calistoga statement that the results are “very encouraging.”
What did the researchers actually see? There are a lot of numbers to digest, as usual, so I figured a chart might be helpful. Researchers didn’t see any complete responses, in which tumors are totally eradicated, but they did see partial responses, in which tumors shrink by 50 percent or more. Below I’ve separated out different patient groups, and listed how many patients responded to the drug in each group based on what I gathered from Gallagher:
| Responders | Percentage | |
| Slow-growing “indolent” non-Hodgkin’s lymphoma | 9/15 | 60 percent |
| Mantle cell lymphoma | 6/7 | 86 percent |
| Chronic lymphocytic leukemia | 4/17 | 24 percent |
| Diffuse large B-cell lymphoma | 0/5 | 0 percent |
| Acute myeloid leukemia | 0/9 | 0 percent |
The patients who entered this study were quite sick. About half had relapsed prior to entering the study, and they had received a median of 4.5 treatment cycles. The most common serious side effect
