- Analysis of 2
Actimab-A Phase 1 clinical trials show that 42% of patients with low
peripheral blast (PB) burden responded to Actimab-A while no patients
with high PB burden responded to Actimab-A
- Key threshold level for low PB Burden per PB Burden Hypothesis identified as 200 blasts/µL
- Actimab-A has progressed to Phase 2 trial as a monotherapy via two simple fifteen minute injections administered a week apart in patients below PB burden threshold
Actinium
Pharmaceuticals, Inc. (NYSE MKT:ATNM) ("Actinium" or "the Company"), a
biopharmaceutical company developing innovative targeted therapies for
cancers lacking effective treatment options, announced today that
results from its Phase 1 trial of Actimab-A were presented at the 58th
American Society of Hematology Annual Meeting (ASH) that is currently
ongoing in San Diego, CA. Data from the previously conducted Phase 1
study pertaining to safety, efficacy and PB burden were highlighted
during the poster session. Actimab-A is currently being studied in a
53-patient Phase 2 clinical trial as a monotherapy for patients newly
diagnosed with Acute Myeloid Leukemia (AML) age 60 and above who are
ineligible for currently used induction therapies. The Phase 2 trial is
studying Actimab-A as a monotherapy administered via two fifteen minute
intravenous injections of 2.0 μCi/kg/fraction of Actimab-A given a week
apart. PB burden below 200 blasts/µL will serve as an inclusion criteria
and patients above this threshold will be administered hydroxyurea to
reduce their peripheral blasts counts prior to Actimab-A administration.
Results from the Phase 1 trial showed that patients with PB burden
below 200 blasts/µL who received a dose of 2.0 μCi/kg/fraction of
Actimab-A saw a 50% response rate.
Actinium’s PB
burden hypothesis states that patients below the key threshold level of
200 blasts/µL have an increased response rate to Actimab-A while
patients above the key threshold are unlikely to respond. An analysis of
2 clinical trials with Actimab-A totaling 38 patients, of which 36 were
evaluable, showed that 42% (8 of 19) of patients with blasts counts
below 200/µL responded to Actimab-A while no patients with blast counts
above 200/µL responded to Actimab-A. The Phase 1 trial was a dose
escalation study using a 3+3 design. Dose escalation proceeded if
dose-limiting toxicities (DLT) were seen in less than 33% of patients.
Maximum tolerable dose (MTD) was not reached in the Phase 1 trial.
Dr.
Joseph Jurcic, Director of Hematologic Malignancies and Professor of
Medicine at Columbia University Medical Center and Principal
Investigator of the study said, “Older patients with AML, particularly
those that have progressed from MDS, are difficult to treat and have
very few treatment options since many have already received
lower-intensity therapy with hypomethylating agents. The results from
this Phase 1 trial were encouraging in regards to both the safety and
efficacy of Actimab-A. We are particularly excited to have identified
that patients with peripheral blasts below 200/µL have higher response
rates to Actimab-A and that we can reduce blast counts in patients above
that level using hydroxyurea. Actimab-A has shown promise in older AML
patients, including those previously treated for MDS--a population
excluded from trials with most novel agents, including ongoing studies
with other CD33-directed therapies. We look forward to continuing to
study Actimab-A in the ongoing Phase 2 trial and potentially meeting
this critical need.”
Of the 18 patients in the
Phase 1 trial, 28% (5 of 18) had objective responses (2 CR, 1CRp and 2
CRi). Amongst patients with objective responses, median response
duration was 9.1 months (range, 4.1-16.9 months). At the 3 highest dose
levels in the Phase 1 trial (1.0 μCi/kg/fraction - 2.0 μCi/kg/fraction)
objective responses were seen in 33% of patients (5 of 15). Mean bone
marrow blast reduction amongst evaluable patients was 66% with 57% of
patients having bone marrow blast reduction of 50% or greater and 79% of
patients (11 of 14) had bone marrow blast reductions after Cycle 1 of
therapy. The Phase 1 trial enrolled patients newly diagnosed with AML
who are age 60 and above who were administered Actimab-A in combination
with low-dose Cytarabine. Median patient age was 77 with 67% of patients
having prior myelodysplastic syndrome (MDS) of which, 83% received
prior therapy consisting of either hypomethylating agents (HMAs) or a
hematopoietic stem cell transplant (HSCT).
A
formal interim analysis will occur after 31 patients receive Actimab-A,
which the Company expects to occur in mid-2017. The Company anticipates
the Phase 2 trial to be complete by the end of 2017.
“Actimab-A,
given its benign toxicity profile combined with potent efficacy as
evidenced by the results presented today along with its ease of
administration via 2 injections, represents an exciting therapy for
elderly patients with AML,” said Sandesh Seth, Executive Chairman of
Actinium. “Due to our peripheral blast burden hypothesis and optimized
Phase 2 protocol we have great excitement for the current Phase 2
clinical trial and future development pathways for Actimab-A.”
About Actimab-A
Actimab-A,
Actinium's most advanced alpha particle immunotherapy (APIT) product
candidate, is currently in a 53-patient, multicenter Phase 2 trial for
patients newly diagnosed with AML age 60 and above. Actimab-A is being
developed as a first-line therapy and is a monotherapy that is
administered via two 15-minute injections that are given 7 days apart.
Actimab-A targets CD33, a protein abundantly expressed on the surface of
AML cells via the monoclonal antibody, HuM195, which carries the potent
cytotoxic radioisotope actinium-225 to the AML cancer calls.
Actinium-225 gives off high-energy alpha particles as it decays, which
kill cancer cells and as actinium-225 decays it produces a series of
daughter atoms, each of which gives off its own alpha particle,
increasing the chances that the cancer cell will be destroyed. Actimab-A
is a second-generation therapy from the Company’s HuM195-Alpha program,
which was developed at Memorial Sloan Kettering Cancer Center and has
now been studied in almost 90 patients in four clinical trials.
Actimab-A has been granted Orphan Drug Designation for newly diagnosed
AML age 60 and above.
About Actinium Pharmaceuticals, Inc.
Actinium
Pharmaceuticals, Inc. is a biopharmaceutical company developing
innovative targeted therapies for patients with cancers lacking
effective treatment options. Actinium's proprietary platform utilizes
monoclonal antibodies to deliver radioisotopes directly to cells of
interest in order to kill those cells safely and effectively. The
Company's lead product candidate Iomab-B is designed to be used, upon
approval, in preparing patients for a hematopoietic stem cell
transplant, commonly referred to as bone marrow transplant. A bone
marrow transplant is often the only potential cure for patients with
blood-borne cancers but the current standard preparation for a
transplant requires chemotherapy and/or total body irradiation that
result in significant toxicities. Actinium believes Iomab-B will enable a
faster and less toxic preparation of patients seeking a bone marrow
transplant, leading to increased transplant success and survival rates.
The Company is currently conducting a single pivotal 150-patient,
multicenter Phase 3 clinical study of Iomab-B in patients with relapsed
or refractory acute myeloid leukemia (AML) age 55 and older. The
Company's second product candidate, Actimab-A, is currently in a
multicenter open-label, 53-patient Phase 2 trial for patients newly
diagnosed with AML age 60 and over. Actimab-A is being developed to
induce remissions in elderly patients with AML who lack effective
treatment options and often cannot tolerate the toxicities of standard
frontline therapies. Actinium is also utilizing its alpha-particle
immunotherapy (APIT) technology platform to generate new drug candidates
based on antibodies linked to the element Actinium-225 that are
directed at various cancers that are blood-borne or form solid tumors.
Actinium Pharmaceuticals is based in New York, NY. To learn more about
Actinium Pharmaceuticals, please visit www.actiniumpharma.com and to follow @ActiniumPharma on Twitter please visit, www.twitter.com/actiniumpharma.
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