ATNM-400 / Actinium Pharmaceuticals - LARVOL DELTA

First-In-Human Phase 1 Study of ATNM-400, Actinium-225 Antibody Radioconjugate, in Metastatic Castration-Resistant Prostate Cancer (mCRPC) (ESMO 2026) - No abstract available

First-in-human • Metastases • P1 data • Castration-Resistant Prostate Cancer • Genito-urinary Cancer • Oncology • Prostate Cancer • Solid Tumor

RADIANZ: First-In-Human Phase 0 Imaging Study of ⁸⁹Zr-ATNM-400 in Patients with Solid Tumors (ESMO 2026) - No abstract available

Clinical • First-in-human • P1 data • Oncology • Solid Tumor

ATNM-400: A First-in-Class Actinium-225 Antibody Radioconjugate Demonstrating Durable, Mutation-Agnostic Anti-Tumor Activity in Non-Small Cell Lung Cancer Models (SNMMI 2026) - "Although approved EGFR inhibitors (osimertinib) and KRAS G12C inhibitors (sotorasib and adagrasib) provide benefit in molecularly defined NSCLC subsets, responses are heterogeneous and resistance is inevitable, highlighting the need for mutation-agnostic therapeutic strategies...ATNM-400 was also tested head-to-head with additional approved agents in NSCLC, namely TROP-2 ADC Dato-DXd, and EGFR-cMET bispecific antibody amivantamab... ATNM-400 demonstrates potent and durable anti-tumor activity with favorable tolerability across multiple preclinical NSCLC models independent of oncogenic driver mutation status. Broad target expression, including in treatment-resistant disease, together with the high-linear energy transfer of 225Ac, supports ATNM-400 as a mutation-agnostic targeted alpha therapy with potential to address key limitations of genotype-restricted systemic treatments in NSCLC. These findings support further translational development and clinical evaluation of..."

IO biomarker • Preclinical • Lung Cancer • Non Small Cell Lung Cancer • Oncology • Solid Tumor • KRAS

ATNM-400: A First-in-Class Actinium-225 Antibody Radioconjugate Demonstrating Durable, Mutation-Agnostic Anti-Tumor Activity in Non-Small Cell Lung Cancer Models (SNMMI 2026) - "Although approved EGFR inhibitors (osimertinib) and KRAS G12C inhibitors (sotorasib and adagrasib) provide benefit in molecularly defined NSCLC subsets, responses are heterogeneous and resistance is inevitable, highlighting the need for mutation-agnostic therapeutic strategies...ATNM-400 was also tested head-to-head with additional approved agents in NSCLC, namely TROP-2 ADC Dato-DXd, and EGFR-cMET bispecific antibody amivantamab... ATNM-400 demonstrates potent and durable anti-tumor activity with favorable tolerability across multiple preclinical NSCLC models independent of oncogenic driver mutation status. Broad target expression, including in treatment-resistant disease, together with the high-linear energy transfer of 225Ac, supports ATNM-400 as a mutation-agnostic targeted alpha therapy with potential to address key limitations of genotype-restricted systemic treatments in NSCLC. These findings support further translational development and clinical evaluation of..."

IO biomarker • Preclinical • Lung Cancer • Non Small Cell Lung Cancer • Oncology • Solid Tumor • KRAS

Actinium Pharmaceuticals Oral Presentation at SNMMI 2026 Highlights ATNM-400 Overcoming Resistance to All Three Approved Androgen Receptor Inhibitors and Offers Flexible, Well-Tolerated Dosing in Prostate Cancer Models (Actinium Pharmaceuticals Press Release) - "ATNM-400 remained potent against cells and tumors resistant to all three approved ARPIs, achieved 94% tumor growth inhibition as a single agent and durable complete responses in combination, and maintained a consistent, clean safety profile across both single-bolus and repeat-dose regimens...In a low-PSMA, moderate-target tumor model (22Rv1), a single bolus dose of ATNM-400 (40 or 30 µCi/kg) delivered superior tumor control versus fractionated dosing, and a repeat 30 µCi/kg regimen sustained tumor control and survival through day 60 with all regimens outperforming 177Lu-PSMA-617 and showing minimal deviation from vehicle in blood, liver, and kidney safety markers."

Preclinical • Prostate Cancer

Actinium Pharmaceuticals…announced it will provide a program update on its first-in-class Actinium-225 (225Ac) antibody radioconjugate, ATNM-400, highlighting new data that will be showcased across three presentations at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2026 Annual Meeting (PRNewswire) - "Two of the presentations showcase ATNM-400's differentiated profile across prostate cancer and non-small cell lung cancer (NSCLC), while a third demonstrates the importance of radioconjugate optimization for radiotherapies in the context of the Company's pipeline candidates....The data to be presented reinforce the meaningful progress of the ATNM-400 program and its potential as a mutation-agnostic, pan-tumor therapy, while also demonstrating the strength of the underlying radioconjugate platform that supports Actinium's broader pipeline."

Preclinical • Non Small Cell Lung Cancer • Prostate Cancer

ATNM-400: A First-in-Class Actinium-225 Antibody Radioconjugate Demonstrating Potent PSMA-Independent Efficacy in Prostate Cancer Models (SNMMI 2026) - "ATNM-400 demonstrates robust, PSMA-independent antitumor activity across PCa models, including PSMA-low, PSMA-negative, and PSMA-targeted therapy-resistant disease. By targeting a non-PSMA antigen linked to aggressive biology and resistance, ATNM-400 overcomes a key limitation of current PSMA-directed radioligand therapies and delivers favorable tumor retention with rapid normal tissue clearance, supporting a strong therapeutic index. ATNM-400 consistently outperformed both 177Lu-PSMA-617 and 225Ac-PSMA-617 in vivo, including in PSMA-therapy-resistant models, positioning ATNM-400 as a next-generation 225Ac antibody radioconjugate with potential utility as monotherapy across all prostate cancer disease states (HSPC, CRPC, and mCRPC) and as a complementary option before or after PSMA-targeted radioligand therapy."

Clinical • Preclinical • Castration-Resistant Prostate Cancer • Genito-urinary Cancer • Hormone Sensitive Prostate Cancer • Oncology • Prostate Cancer • Solid Tumor • FOLH1

ATNM-400: A First-in-Class Actinium-225 Antibody Radioconjugate Demonstrating Potent PSMA-Independent Efficacy in Prostate Cancer Models (SNMMI 2026) - "ATNM-400 demonstrates robust, PSMA-independent antitumor activity across PCa models, including PSMA-low, PSMA-negative, and PSMA-targeted therapy-resistant disease. By targeting a non-PSMA antigen linked to aggressive biology and resistance, ATNM-400 overcomes a key limitation of current PSMA-directed radioligand therapies and delivers favorable tumor retention with rapid normal tissue clearance, supporting a strong therapeutic index. ATNM-400 consistently outperformed both 177Lu-PSMA-617 and 225Ac-PSMA-617 in vivo, including in PSMA-therapy-resistant models, positioning ATNM-400 as a next-generation 225Ac antibody radioconjugate with potential utility as monotherapy across all prostate cancer disease states (HSPC, CRPC, and mCRPC) and as a complementary option before or after PSMA-targeted radioligand therapy."

Clinical • Preclinical • Castration-Resistant Prostate Cancer • Genito-urinary Cancer • Hormone Sensitive Prostate Cancer • Oncology • Prostate Cancer • Solid Tumor • FOLH1

ATNM-400: A First-in-Class Actinium-225 Antibody Radioconjugate Demonstrating Potent PSMA-Independent Efficacy in Prostate Cancer Models (SNMMI 2026) - "ATNM-400 demonstrates robust, PSMA-independent antitumor activity across PCa models, including PSMA-low, PSMA-negative, and PSMA-targeted therapy-resistant disease. By targeting a non-PSMA antigen linked to aggressive biology and resistance, ATNM-400 overcomes a key limitation of current PSMA-directed radioligand therapies and delivers favorable tumor retention with rapid normal tissue clearance, supporting a strong therapeutic index. ATNM-400 consistently outperformed both 177Lu-PSMA-617 and 225Ac-PSMA-617 in vivo, including in PSMA-therapy-resistant models, positioning ATNM-400 as a next-generation 225Ac antibody radioconjugate with potential utility as monotherapy across all prostate cancer disease states (HSPC, CRPC, and mCRPC) and as a complementary option before or after PSMA-targeted radioligand therapy."

Clinical • Preclinical • Castration-Resistant Prostate Cancer • Genito-urinary Cancer • Hormone Sensitive Prostate Cancer • Oncology • Prostate Cancer • Solid Tumor • FOLH1

Actinium Pharmaceuticals Announces Three SNMMI 2026 Presentations Highlighting Differentiated Profile of ATNM-400 Across Lung and Prostate Cancer and Radioconjugate Optimization (PRNewswire) - "ATNM-400 in NSCLC: New data demonstrates ATNM-400's potential in KRAS-mutated models supporting its development as a mutation-agnostic therapy in settings where resistance to EGFR- and KRAS-targeted agents remains a major clinical challenge...ATNM-400 in prostate cancer: New data further supports ATNM-400 as a potential treatment option across the spectrum of PSMA-high, PSMA-low, and PSMA-negative disease, addressing a key limitation of PSMA-targeted therapies...Radioconjugation platform: New data demonstrates that optimizing chelator-to-antibody ratio (CAR) improves tumor targeting, internalization, and pharmacokinetics of 225Ac-labeled antibodies, directly supporting ATNM-400 development and reinforcing a proprietary radiochemistry capability that underpins Actinium's broader pipeline."

Preclinical • Non Small Cell Lung Cancer • Prostate Cancer

First target disclosure for the preclinical development of ATNM-400, a first-in-class actinium-225 radioconjugate with pan-tumor efficacy in solid tumors (AACR 2026) - "In vivo, ATNM-400 demonstrated sustained tumor uptake with off-target exposure in normal tissues, driving potent anti-tumor activity in:• Prostate cancer: ATNM-400 outperformed androgen receptor (AR) pathway inhibitor enzalutamide, 177Lu-PSMA-617, and 225Ac-PSMA-617, producing durable regressions and complete responses in enzalutamide- and 225Ac-PSMA-617-resistant models.• EGFR-mutant lung cancer: ATNM-400 synergized with EGFR inhibitor osimertinib, achieving complete cures in animals, correlating with increased target expression in osimertinib-resistant models.• Breast cancer: ATNM-400 exhibited tumor regressions in HR+ breast cancer, TNBC and combination activity in estrogen receptor (ER) inhibitor tamoxifen- and HER2 antibody trastuzumab-resistant tumors, correlating with increased target expression. ATNM-400 exhibits robust pan-tumor activity, overcomes resistance to AR, EGFR, and HER2/ER-targeted therapies, and demonstrates a favorable safety profile. These..."

Pan tumor • Preclinical • Breast Cancer • Genito-urinary Cancer • HER2 Breast Cancer • HER2 Positive Breast Cancer • Hormone Receptor Breast Cancer • Hormone Receptor Positive Breast Cancer • Lung Cancer • Oncology • Prostate Cancer • Solid Tumor • Triple Negative Breast Cancer

Actinium Pharmaceuticals, Inc. Announces Compelling Pan-Tumor Data for ATNM-400 Demonstrating Broad Efficacy Across Prostate, Lung, and Breast Cancer Models at the 2026 American Association of Cancer Research Annual Meeting (PRNewswire) - "In prostate cancer, ATNM-400 demonstrates efficacy across both high PSMA-expressing and, importantly, low PSMA-expressing prostate cancer models, unlike many PSMA-targeted radioligand therapies that work only in PSMA-high settings; In EGFR-mutant non-small cell lung cancer, ATNM-400 demonstrates greater tumor growth inhibition than osimertinib (a tyrosine kinase inhibitor) plus chemotherapy and outperforms the approved Trop-2 ADC Dato-DXd (DATROWAY), the EGFR-cMET bispecific antibody amivantamab (RYBREVANT) and the experimental EGFR-HER3 ADC izalontamab brengitecan, supporting potential use across first-, second-, and third-line treatment settings; In breast cancer, new head-to-head data shows ATNM-400 achieves efficacy comparable to the approved HER2-ADC trastuzumab deruxtecan (ENHERTU) in trastuzumab-resistant models, with durable tumor control observed after treatment discontinuation..."

Preclinical • HER2 Positive Breast Cancer • Non Small Cell Lung Cancer • Prostate Cancer

ATNM-400 is a novel Actinium-225 antibody radioconjugate with strong efficacy in preclinical models of prostate cancer (AACR 2025) - "ATNM-400 showed strong anti-tumor efficacy and a favorable safety profile in preclinical PCa models. These results highlight ATNM-400's potential as a transformative therapeutic option for PCa patients with unmet clinical needs."

Preclinical • Castration-Resistant Prostate Cancer • Genito-urinary Cancer • Oncology • Prostate Cancer • Solid Tumor • FOLH1

Actinium Pharmaceuticals Announces New Pan-Tumor Preclinical Data for ATNM-400 in Solid Tumors and Differentiated Mechanism for Actimab-A in AML to be Presented at 2026 AACR Annual Meeting (PRNewswire) - "New data underscoring the potential of ATNM-400 as a first-in-class Ac-225 radioconjugate with broad pan-tumor efficacy across multiple solid tumor models. Actimab-A demonstrates mutation-agnostic efficacy and a novel mechanism that enhances response to standard AML therapies. Multiple data catalysts for ATNM-400 and Actimab-A in 2026; and posters for each to be presented on April 21, 2026 at AACR 2026 in San Diego, CA."

Preclinical • Acute Myelogenous Leukemia • Solid Tumor

Actinium Pharmaceuticals, Inc. to Present Two Abstracts at the 2026 AACR Annual Meeting (PRNewswire) - "AACR Presentations to Feature ATNM-400 and Actimab-A Programs Across Solid Tumors and Hematologic Oncology Applications....The AACR 2026 data will highlight Actinium's differentiated biology-driven approach to targeted radiotherapy development including: Targeting resistance-associated biology rather than tumor surface expression alone; Leveraging the high-linear energy transfer (LET) of Ac-225 to deliver potent, tumor-specific cytotoxicity; Building a radiotherapy franchise comprised of multiple pan-tumor assets."

Clinical • Preclinical • Acute Myelogenous Leukemia • Castration-Resistant Prostate Cancer • Non Small Cell Lung Cancer • Triple Negative Breast Cancer

Anti-tumor activity of ATNM-400, a first-in-class Actinium-225 antibody radioconjugate, in tamoxifen and trastuzumab resistant breast cancer models (SABCS 2025) - "While antibody drug conjugates (ADCs) like trastuzumab deruxtecan (Enhertu) show strong efficacy in HER2+ and HER2-low BC, their use is limited by interstitial lung disease toxicities. ATNM-400 shows strong anti-tumor efficacy and favorable tolerability across multiple BC subtypes, including models resistant to tamoxifen and trastuzumab. These findings support further development of ATNM-400 as a novel therapeutic approach for patients with limited options following endocrine or HER2-targeted therapy failure-both as monotherapy and rational combination regimens."

Preclinical • Breast Cancer • HER2 Breast Cancer • HER2 Positive Breast Cancer • Hormone Receptor Breast Cancer • Hormone Receptor Positive Breast Cancer • Oncology • Solid Tumor • Triple Negative Breast Cancer • ER

Phase 1 trial of a novel antibody-targeted radiotherapy in patients with metastatic castrate-resistant prostate cancer (mCRPC) (ANZCTR) - P1 | N=42 | Not yet recruiting | Sponsor: Actinium Pharmaceuticals Australia Pty Limited

New P1 trial • Castration-Resistant Prostate Cancer • Genito-urinary Cancer • Oncology • Prostate Cancer • Solid Tumor • ERBB3

Actinium Pharmaceuticals Presents New Preclinical Data Demonstrating Potent Anti-Tumor Activity of ATNM-400 Across Multiple Breast Cancer Subtypes Including Hormone Receptor-Positive, Triple-Negative, and Tamoxifen- and HER2 Therapy-Resistant Breast Cancer Models at SABCS 2025 (PRNewswire) - "ATNM-400 demonstrated significant tumor-growth inhibition (TGI) in HR+ (MCF7) and TNBC (MDA-MB-468) in vivo models, with all treatment regimens well tolerated and no significant changes in body weight observed...Trastuzumab-resistant BT474-Clone5 breast cancer cells or Tamoxifen-resistant MCF7-Tam1 breast cancer cells exhibited increased target expression, resulting in enhanced in vitro cytotoxicity with ATNM-400; Combining ATNM-400 with either trastuzumab or tamoxifen resulted in greater cytotoxicity versus monotherapy and produced in vivo tumor regression in the trastuzumab-resistant model....ATNM-400 treatment of these trastuzumab-resistant breast cancer cells caused significant increase in phosphorylated H2AZ (pH2AX), consistent with alpha-particle–driven double-strand DNA damage."

Preclinical • Hormone Receptor Positive Breast Cancer • Triple Negative Breast Cancer

Actinium Pharmaceuticals Announces ATNM-400 Data Demonstrating Potent Efficacy in Triple-Negative Breast Cancer and Ability to Overcome Endocrine and HER2-Targeted Therapy Resistance Being Presented at the San Antonio Breast Cancer Symposium (GlobeNewswire) - "In HR+ MCF-7 xenograft models triple-negative and MDA-MB-468 models, ATNM-400 achieved robust tumor growth inhibition (TGI) across dose levels with TGI exceeding 100% at higher doses....ATNM-400 retained significant efficacy in both tamoxifen-resistant and trastuzumab-resistant cell lines and xenograft models, demonstrating its ability to overcome established resistance mechanisms that limit current therapies."

Preclinical • HER2 Positive Breast Cancer • Hormone Receptor Positive Breast Cancer • Triple Negative Breast Cancer

ATNM-400, a first-in-class Actinium-225 antibody radioconjugate, demonstrates potent anti-tumor activity and overcomes resistance to enzalutamide and 177Lu-PSMA-617 in prostate cancer models (PCF 2025) - "We hypothesized that ATNM-400 would provide superior efficacy compared to current options and overcome resistance to AR inhibitors (enzalutamide) and PSMA-directed radioligands (177Lu-PSMA-617 or 225Ac-PSMA-617). ATNM-400 showed robust and durable anti-tumor efficacy and a favorable safety profile in preclinical PCa models. These findings support ATNM-400 as a next-generation Actinium-225 therapy - with potential as 1) Monotherapy in CRPC (pre-177Lu-PSMA-617), 2) Combination therapy with AR pathway inhibitors, or 3) Sequential therapy after ARPI or 177Lu-PSMA-617 failure. ATNM-400 holds promise to address critical gaps in mCRPC treatment landscape."

Preclinical • Castration-Resistant Prostate Cancer • Genito-urinary Cancer • Oncology • Prostate Cancer • Solid Tumor • FOLH1

Actinium Pharmaceuticals, Inc. to Highlight ATNM-400 Data in Hormone-Resistant and HER2-Resistant Breast Cancer at the 2025 San Antonio Breast Cancer Symposium, Expanding Pan-Tumor Profile Across Three Solid Tumor Indications (PRNewswire) - "New preclinical data to show anti-tumor activity of ATNM-400 in hormone-resistant and HER2-resistant breast cancer, addressing the need for new treatment options beyond tamoxifen and trastuzumab."

Preclinical • HER2 Breast Cancer • Hormone Receptor Breast Cancer

Actinium Announces Superior Anti-Tumor Activity of ATNM-400 in Lung Cancer Compared to the Leading First, Second and Third-Line Approved EGFR Mutant Therapies and Mechanistic Synergy with Osimertinib at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics (Actinium Pharmaceuticals Press Release) - "ATNM-400 exhibits superior efficacy with 3-5x greater tumor growth inhibition compared to front line therapy osimertinib (EGFR TKI TAGRISSO), second line therapy Dato-DXd (Trop-2 ADC DATROWAY) and third line therapy amivantamab (EGFR-cMET bispecific RYBREVANT); Combination of ATNM-400 and osimertinib resulted in complete tumor regression in 100% of tumor bearing animals; synergistic mechanism supported by increased ATNM-400 target antigen expression after EGFR inhibition with osimertinib."

Preclinical • Non Small Cell Lung Cancer

ATNM-400, a first-in-class Actinium-225 antibody radioconjugate, demonstrates potent anti-tumor activity and overcomes osimertinib resistance in lung cancer models (AACR-NCI-EORTC 2025) - "ATNM-400 shows strong anti-tumor efficacy and favorable tolerability across multiple LC subtypes, including Osi resistant models. These findings support further development of ATNM-400 as a novel therapeutic approach for LC patients with limited options following TKI therapy failure- both as monotherapy and in rational combination regimens or post-resistance to TKI."

Preclinical • Lung Cancer • Non Small Cell Lung Cancer • Oncology • Solid Tumor • CDKN2A • HER-2 • KRAS • TP53

Actinium Pharmaceuticals Presents New Data Demonstrating Potent and Durable Efficacy of ATNM-400, a First-in-Class Multi-Tumor Actinium-225 Radiotherapy, at the 32nd Annual Prostate Cancer Foundation Scientific Retreat (PRNewswire) - "ATNM-400 demonstrated superior and 5-times more durable anti-tumor efficacy extending to 100 days compared to approximately 20 days with enzalutamide alone...ATNM-400 overcame 177Lu-PSMA-617 resistance with approximately 5-times long tumor control and 2-times longer overall survival in tumor bearing animals...ATNM-400 targets a highly differentiated, non-PSMA antigen associated with the development and progression of prostate cancer, exhibiting potent therapeutic activity independent of PSMA expression levels; The expression of the ATNM-400 antigen target was not altered post-177Lu-PSMA-617; 22Rv1 cell lines are low-PSMA expressing and LNCaP cell lines are high-PSMA expressing."

Preclinical • Prostate Cancer

Actinium to Present ATNM-400 Preclinical Data Highlighting Durable Tumor Control and Ability to Overcome Resistance to Standard-of-Care Prostate Cancer Therapies at the 32nd Annual Prostate Cancer Foundation Scientific Retreat (PRNewswire)

Preclinical • Castration-Resistant Prostate Cancer