CAR T-cell immunotherapy was seen to eradicate or shrink tumors in 70% of patients with chronic lymphocytic leukemia (CLL) who had exhausted other treatment options, according to a clinical trial report.
Among those who had no sign of cancer left in the bone marrow four weeks after treatment, all had survived with no signs of cancer after six months.
Researchers at the Fred Hutchinson Cancer Research Center also suggested, based on the studies, that analyzing bone marrow using a new genetic technique is a better method than the more commonly used cell counts when attempting to determine a prognosis for the disease.
The report, “Durable Molecular Remissions in Chronic Lymphocytic Leukemia Treated With CD19-Specific Chimeric Antigen Receptor–Modified T Cells After Failure of Ibrutinib,” described the outcomes of 24 CLL patients whose cancer had progressed after treatment with Imbruvica (ibrutinib), which was approved for the treatment of CLL in 2014. The research was published in the Journal of Clinical Oncology.
“It was not known whether CAR T-cells could be used to treat these high-risk CLL patients,” Cameron Turtle, an immunotherapy researcher at Fred Hutch and lead author of the study, said in a press release. “Our study shows that CD19 CAR T-cells are a highly promising treatment for CLL patients who have failed ibrutinib.”
CD19 is a molecule found on the surface of leukemia cells. T-cells, gathered from a patient, are engineered to specifically recognize this factor. When that happens, the body launches an aggressive immune response toward these cancer cells.
The Phase 1/2 study (NCT01865617) — which is still recruiting participants — included patients who had failed a median of five previous treatment rounds. The participants’ ages ranged from 40 to 73.
Before injecting the engineered T-cells into patients, their white blood cells were destroyed by chemotherapy.
One patient had a severe toxic response to the treatment and was not assessed for the therapy’s effects. Among the remaining patients, 16 of 23 — 70% — had a response four weeks after treatment.
Not all patients had chemotherapy before CAR T-cell treatment, but among the 19 who did, four had a complete response, and 10 had a partial response.
Two additional patients responded after a second round of chemotherapy and CAR T-cell treatment.
Analyzing bone marrow using a method that can sort cancerous cells from normal cells indicated that 88% were free of disease after treatment. But repeating the analysis in 12 of these patients using a method called IGH deep sequencing showed that only 58% of them had no disease present in the bone marrow.
Those in which the genetic analysis found no traces of cancer all survived with no further traces of disease for a median of 6.6 months after treatment.
For more information about the trial, which also includes patients with relapsed or refractory non-Hodgkin’s lymphoma or acute lymphoblastic leukemia, see the trial registration page at this link. The trial treats patients at the Seattle Cancer Care Alliance clinic.