- 99.8% tumor growth inhibition achieved
with a single dose of ATNM-400 in preclinical prostate cancer
models
- ATNM-400 accumulated in tumors for up to
144 hours and showed minimal uptake in healthy tissues in prostate
cancer xenograft model
- Initial ATNM-400 preclinical data to be
presented at AACR including results in Pluvicto resistant prostate
cancer models
NEW
YORK, March 27, 2025 /PRNewswire/ -- Actinium
Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or
the Company), a pioneer in the development of targeted
radiotherapies, today announced ATNM-400, a novel, non-PSMA
targeting, first in class radiotherapy for prostate cancer
utilizing the Actinium-225 (Ac-225) radioisotope. Initial
preclinical data from ATNM-400 will be presented at the American
Association for Cancer Research (AACR) Annual Meeting being held on
April 25 - 30, 2025, in Chicago, IL. The ATNM-400 AACR abstract will
include the results from in vitro and in vivo studies including
biodistribution imaging and efficacy analyses with various dose
levels of ATNM-400. Actinium continues to advance ATNM-400 with
additional data expected from Pluvicto-resistant prostate cancer
models at AACR. Pluvicto (Lu-177-PSMA-617) is a prostate-specific
membrane antigen (PSMA) directed targeted radiotherapy that uses
the beta-particle emitting radioisotope Lutetitium-177 (Lu-177)
that is approved for patients with metastatic prostate cancer.
Pluvicto is marketed and sold by Novartis and generated sales of
$1.39 billion in 2024. ATNM-400 is
differentiated from Pluvicto as it targets a different marker than
PSMA that has been shown to be overexpressed in patients with
prostate cancer and uses the alpha-particle emitter Ac-225, which
is more potent than Lu-177 but has a shorter path length, which
could result in fewer off-target effects.
Sandesh Seth, Actinium's Chairman
and CEO, said, "The current era of radiotherapy is built on the
clinical and commercial success of Pluvicto in prostate cancer. The
field is now looking to address patients that do not respond or
progress after Pluvicto therapy. We believe ATNM-400 can address
this high unmet need and we are incredibly excited by our data to
date. As anticipated, we have seen robust tumor control and
ATNM-400 has shown to be well tolerated in preclinical studies,
which we believe is due to the precise and potent cell-killing of
Ac-225. We are also highly excited by the results of our
biodistribution studies that showed selective tumor uptake with
minimal uptake in normal tissues. By focusing on a non-PSMA target,
we also believe ATNM-400 has the potential to address some of the
toxicities reported with Pluvicto and other PSMA targeting
radiotherapies such as xerostomia. We are eager to present our
ATNM-400 data at AACR and to continue to advance this highly novel
prostate cancer candidate."
Highlights from the abstract include:
- ATNM-400 selectively binds to prostate cancer cells, undergoes
rapid internalization, and induces dose-dependent cytotoxicity
- In prostate cancer xenograft mouse models, ATNM-400 accumulated
in tumors for up to 144 hours, while showing minimal uptake in
normal tissues
- Small animal SPECT/CT imaging with Indium-111-labeled antibody
confirmed selective tumor accumulation and clearance from healthy
tissues
- A single dose of ATNM-400 achieved 68.5% tumor growth
inhibition at 20 µCi/kg and 99.8% at 40 µCi/kg, with all doses
being well tolerated
ATNM-400 AACR Presentation Details
Title: ATNM-400 is a novel Actinium-225 antibody radioconjugate
with strong efficacy in preclinical models of prostate cancer
Abstract Number: 578
Session: PO.ET08.01 - Theranostics and Radiotheranostics
Date & Time: April 27, 2025 –
2:00 pm – 5:00
pm
About Actinium Pharmaceuticals, Inc.
Actinium is a pioneer in the development of targeted
radiotherapies intended to meaningfully improve patient outcomes.
Actinium is advancing its lead product candidate Actimab-A, a CD33
targeting therapeutic, as potential backbone therapy in acute
myeloid leukemia (AML) and other myeloid malignancies leveraging
the mutation agnostic alpha-emitter radioisotope payload
Actinium-225 (Ac-225). Actimab-A has demonstrated potential
activity in relapsed and refractory acute myeloid leukemia (r/r
AML) patients in combination with the chemotherapy CLAG-M including
high rates of Complete Remissions (CR) and measurable residual
disease (MRD) negativity leading to improved survival outcomes and
is being advanced to a pivotal Phase 2/3 trial. In addition,
Actinium is engaged with the National Cancer Institute (NCI) under
the Cooperative Research and Development Agreement (CRADA) for
development of Actimab-A in AML and other myeloid malignancies. The
first clinical trial under the CRADA will evaluate the triplet
combination comprised of Actimab-A, Venetoclax (Abbvie/Roche) an
oral Bcl-2 inhibitor and ASTX-727 (Taiho Oncology, an Otsuka
holdings company) a novel oral hypomethylating agent (HMA) in
frontline acute myeloid leukemia (AML) patients. Additionally,
Actinium is developing Actimab-A as a potential pan tumor therapy
in combination with PD-1 checkpoint inhibitors including
KEYTRUDA® and OPDIVO® by depleting myeloid
derived suppressor cells (MDSCs), which represents a potential
multi-billion-dollar addressable market. Iomab-ACT, Actinium's next
generation conditioning candidate, is being developed with the goal
of improving patient access and outcomes for potentially curative
cell and gene therapies. Iomab-B is an induction and conditioning
agent prior to bone marrow transplant in patients with r/r AML,
which Actinium is seeking a potential strategic partner for the
U.S. ATNM-400 is Actinium's novel non-PSMA targeting Ac-225
radiotherapy for prostate cancer, which is supported by preclinical
data and is being advanced to clinical trials. In addition, the
company's R&D efforts are primarily focused on advancing
several preclinical programs for solid tumor indications. Actinium
holds 230 patents and patent applications including several patents
related to the manufacture of the isotope Ac-225 in a
cyclotron.
For more information, please
visit: https://www.actiniumpharma.com/
Forward-Looking Statements
This press release may contain projections or other
"forward-looking statements" within the meaning of the
"safe-harbor" provisions of the private securities litigation
reform act of 1995 regarding future events or the future financial
performance of the Company which the Company undertakes no
obligation to update. These statements are based on management's
current expectations and are subject to risks and uncertainties
that may cause actual results to differ materially from the
anticipated or estimated future results, including the risks and
uncertainties associated with preliminary study results varying
from final results, estimates of potential markets for drugs under
development, clinical trials, actions by the FDA and other
governmental agencies, regulatory clearances, responses to
regulatory matters, the market demand for and acceptance of
Actinium's products and services, performance of clinical research
organizations and other risks detailed from time to time in
Actinium's filings with the Securities and Exchange Commission (the
"SEC"), including without limitation its most recent annual report
on form 10-K, subsequent quarterly reports on Forms 10-Q and Forms
8-K, each as amended and supplemented from time to time.
Investors:
investorrelations@actiniumpharma.com
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SOURCE Actinium Pharmaceuticals, Inc.
