On June 4, 2019 Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) ("Actinium") reported new data from the ongoing pivotal Phase 3 SIERRA study of Iomab-B’s single agent effect in patients with active, relapsed or refractory AML or Acute Myeloid Leukemia age 55 and above (Press release, Actinium Pharmaceuticals, JUN 4, 2019, View Source [SID1234536852]). The data was presented by SIERRA investigator Benjamin Tomlinson, M.D., Adult Hematologic and Stem Cell Transplant Section, Seidman Cancer Center, University Hospitals Case Medical Center (Cleveland, OH) in a poster presentation at the 2019 ASCO (Free ASCO Whitepaper) or American Society of Clinical Oncology (ASCO) (Free ASCO Whitepaper) Annual Meeting that is being held from May 31st – June 4th at the McCormick Place, Chicago.

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Dr. Tomlinson, said, "Older patients with active, relapsed or refractory AML are an underserved patient population. These patients, particularly those with high blast counts as seen in the SIERRA trial, are not typically considered candidates for transplant, which is a potentially curative treatment for AML, and have a poor prognosis with other therapeutic options. Iomab-B has uniquely demonstrated an ability to effectively condition these patients for transplant with robust engraftment. We hypothesized that this successful engraftment is due to the myeloablation and anti-leukemic effect of Iomab-B, since these patients had a median of 30% bone marrow blasts prior to transplant. Therefore, we are highly encouraged to observe that Iomab-B as a single agent has a significant anti-leukemic effect and rapidly reduces peripheral blasts."

The poster can be accessed on Actinium’s website (Click Here).

The poster evaluated data from the first 25% of patients (38) from the SIERRA trial where a total of 29 patients received Iomab-B. This included 19 patients who received Iomab-B directly and 10 patients who received Iomab-B via crossover after conventional care salvage chemotherapy failed to produce a complete response. Previously presented preliminary feasibility data from the SIERRA trial demonstrated that all patients receiving Iomab-B had robust BMT or Bone Marrow Transplant donor engraftment and donor chimerism without delay. The new data presented at ASCO (Free ASCO Whitepaper) evaluated Iomab-B’s effect as a single agent on white blood cells, lymphocytes and peripheral blasts. Of the 16 patients for whom data was available, there was a median reduction of peripheral blasts of 98% by day 3 and 100% reduction by day 8 following Iomab-B administration and prior to any other pre-BMT conditioning. Rapid reduction of peripheral blasts has been observed as an independent prognostic marker that is predictive of both CR or Complete Response and RFS or Relapse-Free Survival in patients with AML after receiving cytotoxic chemotherapy. Gianfaldoni et al1 performed an analysis of 30 newly diagnosed AML patients who were treated with cytotoxic induction chemotherapy and found that a rapid reduction of peripheral leukemia blasts correlated with responses and all patients that achieved CR had a rapid reduction of their peripheral blasts. Elliot et al2, performed a retrospective analysis of 86 adult patients with AML and identified time to clearance of circulating leukemia blasts as an independent prognostic marker of RFS that superseded all other known risk factors including karyotype and number of cycles of induction therapy needed to achieve CR.

"We are delighted that Iomab-B continues to generate encouraging data in the SIERRA trial," said Dr. Mark Berger, Actinium’s Chief Medical Officer. "This is the first time single agent Iomab-B clinical data has been presented and we are quite excited by the rapid peripheral blast reduction that has been observed thus far. Peripheral blast reduction is a highly relevant clinical measure and we are optimistic that it will have a positive impact on durable complete response rates, which is the primary endpoint of the SIERRA trial. We are confident that this data will be well received by SIERRA investigators and will add to the strong engraftment data that has been already reported at ASH (Free ASH Whitepaper) and TCT. Collectively, we are encouraged that Iomab-B is continuing to exemplify best-in-class transplant conditioning potential for this difficult to treat patient population."

Sources:

1) Gianfaldoni et al. clearance of leukemic blasts from peripheral blood during standard induction treatment predicts the bone marrow response in acute myeloid leukemia: a pilot study. British Journal of Haematology, 2006 March 16; 134, 54-57.

2) Elliott et al. Early peripheral blood blast clearance during induction chemotherapy for acute myeloid leukemia predicts superior relapse-free survival. Blood. 2007 Dec 15; 110(13):4172-4. Epub 2007 Oct 1.

About Iomab-B

Iomab-B is an ARC or Antibody Radiation-Conjugate comprised of the anti-CD45 antibody apamistamab and the radioisotope iodine-131 that is intended to be a re-induction and conditioning agent prior to a BMT or bone marrow transplant. Iomab-B was developed at the Fred Hutchinson Cancer Research Center and has been studied in over 300 patients in multiple hematologic indications across 12 clinical trials in addition to the ongoing SIERRA study in older patients with active, relapsed or refractory AML or Acute Myeloid Leukemia prior to patients receiving an allogeneic BMT or bone marrow transplant. Iomab-B is Actinium’s lead targeting conditioning ARC in its multi-target, multi-indication targeted conditioning pipeline that includes the Iomab-B and Actimab-MDS programs for BMT and the Iomab-ACT program that will study a lower dose of Iomab-B for lymphodepletion prior to CAR-T and other cellular therapies.

About Actinium Pharmaceuticals, Inc.

Actinium Pharmaceuticals, Inc. is a clinical-stage biopharmaceutical company focused on improving patient access and outcomes to cellular therapies such as BMT or Bone Marrow Transplant and CAR-T with its proprietary ARC or Antibody Radiation-Conjugate targeted conditioning technology. Actinium