On November 3, 2022 Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company) a leader in the development of targeted radiotherapies, reported that positive results from the Phase 1 trial evaluating Actimab-A with salvage chemotherapy regimen CLAG-M in fit patients with relapsed or refractory acute myeloid leukemia (AML) that is being conducted at the Medical College of Wisconsin as investigator sponsored study (Press release, Actinium Pharmaceuticals, NOV 3, 2022, View Source [SID1234623052]). These data were detailed in an abstract accepted for oral presentation at the 64th Annual ASH (Free ASH Whitepaper) Meeting & Symposium being held December 10-13, 2022 in New Orleans, Louisiana.

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Survival, Response and MRD Negativity Findings
Median Overall Survival (OS) of 12 months amongst all patients (n=21)
1-year OS of 53% and 2-year OS of 32%
Overall Response Rate (ORR) of 67% across all dose cohorts
72% MRD negativity rate in patients achieving CRc
ORR of 83% at the recommended Phase 2 dose of 0.75uCi/kg of Actimab-A with CLAG-M
Actimab-A CLAG-M combo was active in patients with TP53 mutations with an ORR of 73% and an ORR of 55% in patients previously treated with venetoclax
Dr. Sameem Abedin, Assistant Professor at Froedtert & Medical College Wisconsin and Principal Investigator of the Study, commented, "The median overall survival of 12 months and 2-year overall survival of 32% is highly impressive in these relapsed or refractory patients, where a majority of treated patients have adverse cytogenetics including TP53 mutations and received prior venetoclax therapy. These are extremely difficult to treat patients with very limited treatment options and their expected median overall survival is approximately 2 to 3 months."

"These data strongly support the further clinical development of this novel targeted radiotherapy-based combination. We are excited that our hypothesis of adding Actimab-A to CLAG-M to eliminate residual leukemia cells, resulting in deeper remissions and survival with acceptable tolerability given targeted nature of Actimab-A is strongly supported by these findings," concluded Dr. Abedin.

Patient Characteristics
Patients had relapsed or refractory AML and deemed fit with adequate organ function
Patients received a median of two lines of prior therapy
57% received prior venetoclax therapy
67% of patients had adverse cytogenetics, 52% had TP53 mutations
Median age was 63 years
Patients had median blast CD33 expression of 77% (>25% required for enrollment)
52% of patients had secondary AML or treatment related AML
Dr. Avinash Desai, Actinium’s Chief Medical Officer, commented, "Improvements in overall survival have been difficult to achieve in relapsed or refractory AML patients, particularly for those with TP53 mutations. Additionally, as venetoclax-based treatments have become a standard of care, physicians need better treatment options to then manage the significant number of patients that do not respond, stop treatment due to toxicities or relapse and who have a median overall survival of just 2.4 months. We are incredibly excited by these data that clearly show Actimab-A’s potential to improve patient outcomes when combined with CLAG-M. Further, it shows how Actimab-A can be utilized in combination with other therapies and add potency, which supports our strategy to establish it as a backbone therapy for AML with other therapies. With our recommended phase 2 dose finalized and these strong rates of MRD negativity and overall survival, we look forward to providing updates on our development and regulatory strategy as we work to bring this important combination to patients."

ASH Oral Presentation Details
Title: Lintuzumab-Ac225 with Combination with Intensive Chemotherapy Yields High Response Rate and MRD Negativity in R/R AML with Adverse Features

Maiti et al. Outcomes of relapsed or refractory acute myeloid leukemia after front-line hypomethylating agent and venetoclax regimens. Hematoligica 2021 Mar 1; 894-898
Ganzel et al. Very poor long-term survival in past and more recent studies for relapsed AML patients: The ECOG-ACRIN experience. American Journal of Hematology. 2018 Aug; 93(8): 1074–1081