CytRx Corporation (Nasdaq: CYTR), a biopharmaceutical company specializing in oncology, today announced that preliminary results from its ENABLE Phase 2 proof-of-concept trial demonstrated that bafetinib, the Company's Bcr-Abl, Lyn and Fyn kinase inhibitor, was clinically active in a group of patients with relapsed or refractory B-cell chronic lymphocytic leukemia (B-CLL) who have failed several other treatments for their cancer. Based on this indication of clinical activity and the low incidence of adverse events, additional patients enrolled in the ENABLE Phase 2 clinical trial will receive bafetinib as a single agent at a higher dose.
“Lyn kinase, a primary target of bafetinib, is important to the activation and growth of B cells. It is upstream from both PI3kinase delta and Bruton's tyrosine kinase in B-CLL and may regulate the activity of these other kinases in B cell malignancies.”
"We are highly optimistic about bafetinib's prospects based on the preliminary results, which provide an initial indication that this drug candidate's unique kinase inhibition could be efficacious in treating B-CLL and other cancers where approved therapies have failed," said CytRx President and CEO Steven A. Kriegsman. "Due to the low incidence of adverse events, we are now able to increase the dose of bafetinib administered to newly enrolled patients, thus increasing the potential for greater efficacy."
Of the 16 patients enrolled in the ENABLE Phase 2 clinical trial, 11 patients were evaluable for tumor response (patients who have received both baseline and follow-up tumor assessments). At the time of evaluation, the median duration of treatment for all patients was two months, and five of these 11 patients had received three to five months of bafetinib therapy; five patients either did not receive baseline or follow-up assessments. The median number of prior therapies for the full group is three, with a range between one and five prior therapies, and nine of 12 patients demonstrated unfavorable cytogenetics (del 17p; 13). This subgroup of patients typically has fast disease progression and shorter median overall survival.
All 11 evaluable patients demonstrated ≥50% elevation in their lymphocyte counts during the first two months of treatment, similar to other kinase inhibitors being tested in B-CLL patients. Six demonstrated >50% shrinkage in their lymph nodes and/or spleen, two patients had stable disease and three patients had progressive disease at their initial assessments. Lymph node softening also was noted in these patients. Only one grade 3 or 4 adverse event (grade 3 elevated liver enzymes) was noted, which resolved when bafetinib administration was ceased. Grade 1 and 2 adverse events included elevated liver enzymes with normal bilirubin, fatigue and gastrointestinal symptoms.
"These favorable initial Phase 2 clinical trial results of bafetinib's activity and safety mark an important step in our goal to become a leading oncology therapeutics company. Further, we were able to obtain these results quickly after initiating enrollment in this clinical trial, validating our strategy to rapidly and cost-effectively conduct proof-of-concept trials in patients with advanced-stage cancers prior to moving into larger clinical trials," Mr. Kriegsman added.
The ENABLE Phase 2 clinical trial, which is expected to enroll a total of 30 patients, is being performed at M.D. Anderson Cancer Center, City of Hope Medical Center and Cancer Care Centers of Texas. Patients self-administer bafetinib twice daily every day and continue treatment as long as their cancer is controlled and no intolerable side effects occur. The trial's objectives are to assess preliminary efficacy of administration of bafetinib in B-CLL patients and evaluate its safety in this patient population.
"These results are very encouraging," said Daniel Levitt, M.D., PhD, Chief Medical Officer at CytRx. "Lyn kinase, a primary target of bafetinib, is important to the activation and growth of B cells. It is upstream from both PI3kinase delta and Bruton's tyrosine kinase in B-CLL and may regulate the activity of these other kinases in B cell malignancies."
B-CLL is the most common form of leukemia in adults in Western countries. More than 17,000 new cases of B-CLL are reported in the U.S. each year; however up to an estimated 40% of cases may not be reported due to under-diagnosis and lack of placement in cancer registries. Virtually all patients are older than 55 years at presentation, with an average age of 70 years. Patients in the high-risk B-CLL have a median overall survival of one to five years.