Actinium Pharmaceuticals develops targeted radiotherapies for cancer using its Antibody Radiation Conjugates platform and alpha-emitting radioisotopes. Company updates commonly focus on ATNM-400, an Actinium-225 antibody radioconjugate studied in solid tumor models including prostate, lung, and breast cancer, and Actimab-A, or lintuzumab-Ac225, an Actinium-225 therapy targeting CD33 in acute myeloid leukemia.
Additional announcements describe radiochemistry work such as chelator-to-antibody ratio optimization, preclinical data presented at oncology and nuclear medicine meetings, and the company's broader radiotherapy platform across solid tumors, hematologic malignancies, and conditioning for cellular therapies.
Actinium Pharmaceuticals (NYSE American: ATNM) presented new radiochemistry data at SNMMI 2026 on May 31, 2026, showing that optimizing chelator-to-antibody ratio (CAR) for Actinium-225 radioconjugates affects radiolabeling, antigen binding, internalization, and biodistribution.
Lower-CAR constructs maintained tumor uptake while reducing liver and spleen exposure, potentially widening the therapeutic index across Actinium’s radioconjugate pipeline.
Actinium Pharmaceuticals (NYSE American: ATNM) received two Canadian patent allowances covering its Actimab-A and Iomab-ACT programs. These patents extend protection for Actimab-A plus CLAG-M in AML and CD45-targeted conditioning for gene-edited cell therapies, reinforcing a global estate of about 250 patents and applications, with Canadian terms into 2038 and 2039.
Actinium Pharmaceuticals (NYSE American: ATNM) will present new ATNM-400 Actinium-225 antibody radioconjugate data at the SNMMI 2026 meeting in Los Angeles through three scientific posters covering prostate cancer, non-small cell lung cancer and radioconjugate optimization.
The company also received an NYSE American notice for not meeting certain stockholders’ equity listing standards and must submit a compliance plan by June 26, 2026, to avoid potential delisting actions by November 27, 2027.
Actinium (NYSE: ATNM) announced three abstracts at SNMMI 2026 (May 30–June 2, Los Angeles) presenting preclinical data for ATNM-400 and radiochemistry optimization. The posters report ATNM-400 activity in KRAS-mutated NSCLC and PSMA-high/low/negative prostate cancer models and CAR optimization for 225Ac radioconjugates.
Actinium Pharmaceuticals (NYSE: ATNM) presented preclinical AACR 2026 data showing ATNM-400, an Ac-225 radioconjugate, with pan-tumor activity in prostate, EGFR-mutant lung, and HER2+ breast cancer models.
Data show efficacy in low/negative PSMA prostate models, superior activity versus several approved ADCs and targeted agents, durable control post-treatment in breast models, and no in vivo toxicities at therapeutic doses.
Actinium (NYSE:ATNM) presented AACR 2026 data showing that Actimab-A (lintuzumab-Ac225) drives mutation-agnostic anti-leukemic activity via transcriptional reprogramming, shifting AML cells from proliferation toward differentiation and apoptosis. Combinations with revumenib, gilteritinib, and azacitidine enhanced in vivo killing across models and primary patient samples, independent of FLT3, NPM1, KMT2A, IDH1/2, or TP53 status. Prior clinical work in >150 AML patients showed a manageable safety profile and supports Actimab-A as a universal combination backbone across AML treatment settings.
Actinium Pharmaceuticals (NYSE: ATNM) announced two AACR 2026 abstracts to be presented April 21, 2026, highlighting new preclinical data for ATNM-400 and a differentiated mechanism for Actimab-A. ATNM-400 shows pan-tumor Ac-225 radioconjugate activity; Actimab-A shows mutation-agnostic transcriptional reprogramming that may enhance AML therapy response. Posters: ATNM-400 #5824 and Actimab-A #5827 in session Radiopharmaceutical Platforms for Theranostic Precision Oncology, April 21, 2:00–5:00 PM PT, Poster Section 16.
Actinium Pharmaceuticals (NYSE American: ATNM) will present two abstracts at the AACR Annual Meeting 2026 in San Diego on April 21, 2026, within the Experimental and Molecular Therapeutics category.
Abstract details (titles and full text) will be publicly available March 17, 2026 at 4:30 PM ET via the AACR Online Program Planner. Presentations focus on ATNM-400 and Actimab-A programs and radiopharmaceutical theranostic platforms using Ac-225.
Actinium Pharmaceuticals (NYSE: ATNM) presented preclinical data for ATNM-400, an Actinium-225 antibody radioconjugate, at SABCS 2025 showing potent anti-tumor activity across HR+, TNBC, and tamoxifen- and trastuzumab-resistant breast cancer models.
Key findings include significant tumor-growth inhibition in HR+ and TNBC models, increased target expression and enhanced cytotoxicity in treatment-resistant models, combination-induced tumor regression in a trastuzumab-resistant model, sustained tumor uptake through 144 hours, and rapid clearance from normal organs suggesting a differentiated tolerability profile.
Actinium Pharmaceuticals (NYSE: ATNM) will present preclinical data for ATNM-400, a first-in-class Actinium-225 antibody radioconjugate, showing potent anti-tumor activity in triple-negative breast cancer (TNBC) and efficacy in models resistant to tamoxifen and trastuzumab. Data include tumor growth inhibition exceeding 100% at higher doses, elevated target expression in resistant lines, combination activity with standard agents, and a favorable tolerability profile in xenograft models. The program also showed activity in metastatic castrate-resistant prostate cancer and non-small cell lung cancer. The presentation is scheduled for December 11, 2025 at 5:00 PM CT at the San Antonio Breast Cancer Symposium.