WASHINGTON (dpa-AFX) - Actinium Pharmaceuticals Inc. (ATNM) announced positive results from its Phase 1 Actimab-A trial in patients newly diagnosed with acute myeloid leukemia (AML) who are over the age of 60. The median age of patients in the trial was 77 years (range 68-87 years) of which 67% had intermediate-risk cytogenetics and 33% had unfavorable cytogenetics. Importantly, the complete response rate at the dose level which the Company intends to progress into the Phase 2 trial was 50% in patients with low peripheral blast (PB) burden. Most serious adverse events (SAEs) were infections and cytopenias that are considered to be consequences of AML and not drug related.
The c8ompany announced that it will proceed with a Phase 2 trial with Actimab-A at 2 µCi/kg/fractionated dose, the highest dose level from the Phase 1 trial. For the Phase 2 trial, modifications will be made to the protocol including the removal of low dose cytarabine, which has already been agreed to with the FDA, and the mandatory use of hydroxyurea, which can be used per the current protocol, to reduce PB burden with the goal of accelerating patient enrollment and improving patient outcomes.
The recently completed Phase 1 trial totaled 18 patients having a median age of 77 of which 78% were 75 and older and 28% were 80 and older. Complete responses were observed in 28% of patients at all dose levels and in the three highest dose levels complete response rates equaled 33%. Importantly, the complete response rate at the dose level which the Company intends to progress into the Phase 2 trial was 50% in patients with low PB burden. Of the 18 patients, 67% presented with low PB burden.
Also, 67% of patients had secondary AML resulting from myelodysplastic syndrome (MDS). No early mortality was observed within 28 days and 56 day early mortality was observed in 11% of patients. Dose limiting toxicities (DLTs) were observed in 2 patients and both were grade 4 and neither of which were extramedullary. Most serious adverse events (SAEs) were infections and cytopenias that are considered to be consequences of AML and not drug related.
The Phase 2 portion of the trial will enroll an additional 47 patients bringing the total number of patients in the Phase 1/2 Actimab-A trial to 65. This multi-center, single arm trial will enroll patients newly diagnosed with AML who are over the age of 60. The number of centers for the Phase 2 portion of the trial are expected to be at least double the number of centers in the Phase 1 portion of the trial.
In addition, the protocol for the Phase 2 trial has been revised to eliminate low dose cytarabine, which the FDA has already agreed to. The peripheral blast burden key threshold level will serve as an inclusion criteria going forward and the use of hydroxyurea to control peripheral blast burden, which was permitted in the Phase 1 protocol, will be mandated in order to lower PB burden. Patient enrollment is expected to commence in the second half of 2016.
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