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found that 15 of 16 evaluable patients on the drug had at least a 50 percent shrinkage of their lymph nodes, but some of them actually had increases in their lymphatic cell counts in the bloodstream. Those counts went up after initial treatment, but then started dropping over time, Gallagher says. This has prompted Calistoga and its scientific advisors to hypothesize that CAL-101 is essentially able to burrow deep into the bulky tumors of the lymphatic system and the bone marrow, get past the natural defense mechanisms tumors employ in that cellular environment, and flush them out into the circulating bloodstream. That’s something that standard treatments like chemotherapy and rituximab (Rituxan) aren’t very successful at doing, Gallagher says.
Time will tell with more follow-up whether the second, third, and further rounds of CAL-101 treatment will wipe out the circulating cancer cells, Gallagher says. It’s also got the company thinking about designing combination studies that might use CAL-101 to shake loose the bulky tumors in the lymph nodes, and give patients rituximab (Rituxan) when that drug has the best chance to work on cancer cells in the bloodstream, Gallagher says.
“We believe that these patients will ultimately convert from stable disease to partial responders, but we’re not there yet,” Gallagher says.
Cancer often bounces back after a drug shows initial tumor shrinkage ability, so how long will this tumor shrinkage effect really last? There’s not much data on this question, but Calistoga has seen at least one patient have tumor shrinkage continue for at least 224 days. That’s eight cycles of therapy and counting, Gallagher says. Another patient has gone seven cycles without seeing their disease worsen, and another has gone four cycles, she says.
Much more data will be available from Calistoga in December at the American Society of Hematology meeting. The company expects to have data from 80 to 90 patients from various cohorts of patients with chronic lymphocytic leukemia, indolent (slow-growing) non-Hodgkin’s lymphoma, aggressive non-Hodgkin’s lymphoma, acute myeloid leukemia, and multiple myeloma, Gallagher says. Based on that more full set of data, Calistoga plans to start a Phase II/III study that could be used for a new drug application to the FDA, Gallagher says.