Actinium Pharmaceuticals' (ATNM) Iomab-B is an induction and conditioning agent designed to enable patients with relapsed or refractory acute myeloid leukemia (AML) to receive a bone marrow transplant. Iomab-B was developed by scientists at the Fred Hutchinson Center Research Center, an organization with three Nobel Prizes in physiology and medicine. Actinium is currently enrolling patients in a Phase 3 trial is called SIERRA.
BMT is the only curative option for patients with AML and Iomab-B comes from an excellent pedigree. Fred Hutchinson is a recognized leader in the field of BMT and previous data with Iomab-B shows an impressive increase in overall survival compared to the current standard of care (1). Fred Hutchinson is obviously one of the participating centers in the Phase 3 SIERRA trial. However, what I find equally impressive is the current participation in SIERRA by some of the other leading BMT centers in the U.S. I think this positions SIERRA well for success when data read-out in 2018.
Actinium announced the initiation of the SIERRA in June 2016. SIERRA - Study of Iomab-B in Elderly Relapsed or Refractory AML - is a Phase 3, randomized, controlled, multi-center study with a target enrollment of 150 patients with relapsed or refractory AML over the age of 55. Patients are split equally between Iomab-B and physician's choice conventional salvage care prior to BMT. The primary endpoint of SIERRA is durable complete remission (dCR) at six months. Secondary outcome measures include overall survival (OS) at one-year and safety.
Iomab-B does several things designed to improve the odds of survival for elderly patients with relapsed or refractory AML, including reducing the time needed to prepare the patient for a BMT from weeks to days and reducing the cost of care. Conventional care induction and conditioning agents for elderly patients with relapsed or refractory AML include MEC (mitomycin + etoposide + cytarabine), CLAG-M (cladribine + cytarabine + mitoxantrone + filgrastim), and FLAG-IDA (fludarabine + cytarabine + idarubicin + filgrastim). Often two or more rounds of inpatient chemotherapy regimens are necessary to achieve full ablation. It can take 28-42 days and cost upwards of $200,000. Iomab-B is designed to achieve full bone marrow ablation in only six days.
Finally, Iomab-B is designed to be less toxic and have significantly better tolerability than the conventional standard of care. Investors should know, myeloconditioning / myeloablation before BMT is an incredibly complex and delicate balance between safety and efficacy (2). Failure to ablate enough cells can result in high relapse rates or increased risk of Graft vs. Host Disease (GvHD), whereas overly intense therapy causes an increased risk of treatment-related mortality. Selective radiation of leukemia cells using a highly specific radiolabeled monoclonal antibody like Iomab-B has the potential to improve results by targeting malignant cells and causing less systemic damage to surrounding organs (3).
Leading Centers Buy-Into Iomab-B Concept
In February 2017, Actinium participated at the combined annual meeting of the Center for International Blood & Marrow Transplant Research (CIBMTR) and the American Society for Blood and Marrow Transplantation (ASBMT), highlighting past data on Iomab-B and engaging with leading BMT key opinion leaders. The excitement around Iomab-B and SIERRA is high. This is evident by the participation in SIERRA by some of the leading BMT centers in the U.S.
This is important because if Actinium is going to change the standard of care for elderly patients with relapsed or refractory AML, they are going to need support from the top BMT KOLs to get it done. Actinium already has an impressive network of scientific advisors, but now that these leading centers are actively recruiting patients in SIERRA, the nation's top KOLs in BMT can gain first-hand experience with Iomab-B and see the benefits in the clinical setting.
Participation Bodes Well For Commercial Success
The participation in SIERRA by the nation's top BMT centers also positions Actinium well for commercial success once Iomab-B gains approval. The BMT market in the U.S. is highly concentrated. There are roughly 150 BMT centers in the country and the top 30 centers perform 50% of all the AML BMT procedures. Eight of these centers are currently recruiting patients in SIERRA. Prospective Payment System (PPS) exempt cancer centers perform over 20% of the AML BMT procedures and these centers could be reimbursed immediately once Iomab-B gains approval.
The U.S. FDA has already granted Actinium Orphan Drug designation to Iomab-B. The market opportunity with Iomab-B is significant. According to the American Cancer Society, there will be an estimated 21,380 new cases of AML in the U.S. in 2017. Another 27,500 new cases arise in Europe each year. The U.S. NCI estimated 73% of newly diagnosed AML patients are over the age of 55 and there are no currently approved treatment options for these elderly patients with relapsed or refractory disease. It's an estimated patient population of approximately 15,000 individuals, the majority of who cannot tolerate standard conditioning regimens that allow them to progress to a BMT.
By offering a more effective and more tolerable solution to these elderly relapsed or refractory AML patients, Actinium is sitting on a sizable market opportunity with Iomab-B. Standard conditioning regimens cost between $50,000 and $200,000. They can also take as long as 28 to 42 days. At $75,000 for a course of treatment (my guess) over only six days for Iomab-B, this is a $1.15 billion peak market opportunity. And, given that Actinium will target only a few dozen BMT centers with a focused sales force, it's an opportunity the company can easily tackle alone.
Additionally, given the positive news last month that the European Medicines Agency (EMA) finds the trial design, primary endpoint, and planned statistical analysis of SIERRA acceptable and can serve as the basis for submission of a Marketing Authorization Application (MAA) in Europe, I think Actinium has an excellent opportunity to partner Iomab-B for commercialization in Europe and use the upfront licensing cash to fund the U.S. launch.
BMT is one of the fastest growing hospital procedures according to the Healthcare Cost and Utilization Project, AHRQ; US Dept. of HHS. Iomab-B offers a better solution - cheaper, faster, safer, and more effective - than the current standard of care. KOL interest in the drug is high and the company has partnered with some of the leading centers in the U.S. to enroll patients in SIERRA. This is likely why the EMA agreed to accept the data for regulatory filings in Europe.
We are likely to see an interim safety update from the data monitoring committee (DMC) once the first 25% of patients in SIERRA receive treatment. I expect this to occur in the next few months. Two more safety updates at 50% and 75% completion are expected to follow months later, with the top-line data from SIERRA likely during the second half of 2018. I think this will be a major transformative event for Actinium Pharmaceuticals and shareholders.
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