Atossa Therapeutics Announces Plans to Pursue Metastatic Breast Cancer Indication for (Z)-Endoxifen and Continued Engagement with FDA on Additional Indications
Atossa Therapeutics (NASDAQ: ATOS) has announced its strategic focus on developing (Z)-endoxifen for metastatic breast cancer treatment, while simultaneously pursuing additional indications with FDA guidance.
Early clinical trials have shown promising results, with (Z)-endoxifen demonstrating:
- More than doubled median progression-free survival compared to tamoxifen (7.2 vs. 2.4 months) in CDK4/6i-naïve patients
- Clinical benefits in patients who progressed on tamoxifen, including partial responses and stable disease lasting 2-3 years
- Favorable safety profile comparable to tamoxifen
The company is also advancing additional indications including breast cancer prevention and neoadjuvant therapy. In early-stage patients, (Z)-endoxifen maintained a Ki-67 ≤10% response rate above 85% across all dose levels, suggesting effective tumor proliferation reduction.
Atossa Therapeutics (NASDAQ: ATOS) ha annunciato il suo focus strategico nello sviluppo di (Z)-endoxifene per il trattamento del cancro al seno metastatico, mentre persegue simultaneamente ulteriori indicazioni con la guida della FDA.
I primi studi clinici hanno mostrato risultati promettenti, con (Z)-endoxifene che dimostra:
- Una sopravvivenza libera da progressione mediana più che raddoppiata rispetto al tamoxifene (7,2 contro 2,4 mesi) in pazienti naïve a CDK4/6i
- Benefici clinici in pazienti che hanno mostrato progressione con il tamoxifene, inclusi risposte parziali e malattia stabile che dura 2-3 anni
- Un profilo di sicurezza favorevole comparabile a quello del tamoxifene
L'azienda sta anche avanzando in ulteriori indicazioni, tra cui la prevenzione del cancro al seno e la terapia neoadiuvante. Nei pazienti in stadio precoce, (Z)-endoxifene ha mantenuto un tasso di risposta Ki-67 ≤10% superiore all'85% in tutti i livelli di dose, suggerendo una riduzione efficace della proliferazione tumorale.
Atossa Therapeutics (NASDAQ: ATOS) ha anunciado su enfoque estratégico en el desarrollo de (Z)-endoxifeno para el tratamiento del cáncer de mama metastásico, mientras persigue simultáneamente indicaciones adicionales con la guía de la FDA.
Los primeros ensayos clínicos han mostrado resultados prometedores, con (Z)-endoxifeno demostrando:
- Más del doble de la mediana de supervivencia libre de progresión en comparación con el tamoxifeno (7.2 frente a 2.4 meses) en pacientes naïve a CDK4/6i
- Beneficios clínicos en pacientes que progresaron con tamoxifeno, incluyendo respuestas parciales y enfermedad estable que dura de 2 a 3 años
- Un perfil de seguridad favorable comparable al del tamoxifeno
La compañía también está avanzando en indicaciones adicionales, incluyendo la prevención del cáncer de mama y la terapia neoadyuvante. En pacientes en etapa temprana, (Z)-endoxifeno mantuvo una tasa de respuesta Ki-67 ≤10% superior al 85% en todos los niveles de dosis, sugiriendo una reducción efectiva de la proliferación tumoral.
Atossa Therapeutics (NASDAQ: ATOS)는 전이성 유방암 치료를 위한 (Z)-엔독시펜 개발에 전략적 초점을 맞추고 있으며, FDA의 지침에 따라 추가 적응증을 동시에 추구하고 있습니다.
초기 임상 시험에서 (Z)-엔독시펜은 다음과 같은 유망한 결과를 보여주었습니다:
- CDK4/6i에 대해 면역이 없는 환자에서 타목시펜에 비해 7.2개월(타목시펜 2.4개월)로 중앙 무진행 생존 기간이 두 배 이상 증가
- 타목시펜에서 진행된 환자에서 부분 반응과 2-3년 지속되는 안정된 질병을 포함한 임상적 이점
- 타목시펜과 비교할 때 유리한 안전성 프로필
회사는 유방암 예방 및 신보조 요법을 포함한 추가 적응증도 발전시키고 있습니다. 초기 단계 환자에서 (Z)-엔독시펜은 모든 용량 수준에서 Ki-67 ≤10% 반응률을 85% 이상 유지하여 효과적인 종양 증식 감소를 시사합니다.
Atossa Therapeutics (NASDAQ: ATOS) a annoncé son orientation stratégique vers le développement de (Z)-endoxifène pour le traitement du cancer du sein métastatique, tout en poursuivant simultanément d'autres indications avec l'orientation de la FDA.
Les premiers essais cliniques ont montré des résultats prometteurs, avec (Z)-endoxifène démontrant :
- Une survie médiane sans progression plus que doublée par rapport au tamoxifène (7,2 contre 2,4 mois) chez les patients naïfs à CDK4/6i
- Des bénéfices cliniques chez les patients ayant progressé sous tamoxifène, y compris des réponses partielles et une maladie stable durant 2-3 ans
- Un profil de sécurité favorable comparable à celui du tamoxifène
L'entreprise avance également dans d'autres indications, y compris la prévention du cancer du sein et la thérapie néoadjuvante. Chez les patients à un stade précoce, (Z)-endoxifène a maintenu un taux de réponse Ki-67 ≤10% supérieur à 85% dans tous les niveaux de dose, suggérant une réduction efficace de la prolifération tumorale.
Atossa Therapeutics (NASDAQ: ATOS) hat seinen strategischen Fokus auf die Entwicklung von (Z)-Endoxifen zur Behandlung von metastasierendem Brustkrebs bekannt gegeben, während gleichzeitig weitere Indikationen unter Anleitung der FDA verfolgt werden.
Frühe klinische Studien haben vielversprechende Ergebnisse gezeigt, wobei (Z)-Endoxifen Folgendes demonstriert:
- Mehr als doppelte mediane progressionsfreie Überlebenszeit im Vergleich zu Tamoxifen (7,2 vs. 2,4 Monate) bei CDK4/6i-naiven Patienten
- Klinische Vorteile bei Patienten, die mit Tamoxifen fortgeschritten sind, einschließlich partieller Ansprechen und stabiler Erkrankung über 2-3 Jahre
- Ein günstiges Sicherheitsprofil, das mit Tamoxifen vergleichbar ist
Das Unternehmen verfolgt auch weitere Indikationen, einschließlich der Prävention von Brustkrebs und neoadjuvanter Therapie. Bei Patienten im Frühstadium hielt (Z)-Endoxifen eine Ki-67 ≤10% Ansprechrate von über 85% in allen Dosisstufen aufrecht, was auf eine effektive Tumorproliferationsreduktion hindeutet.
- Doubled progression-free survival compared to tamoxifen (7.2 vs 2.4 months)
- Strong efficacy with 85% Ki-67 response rate in neoadjuvant therapy
- Clinical benefit in tamoxifen-resistant patients lasting 2-3 years
- Favorable safety profile despite higher potency
- Larger and longer clinical trials still required for prevention and neoadjuvant indications
- FDA approval pathway not yet clearly defined
- Currently in early clinical stages without market approval
Insights
Atossa Therapeutics' strategic decision to prioritize a metastatic breast cancer indication for (Z)-endoxifen represents a pragmatic approach to drug development that could significantly accelerate their path to market. This strategic pivot offers several advantages:
The metastatic setting typically requires smaller, shorter clinical trials compared to prevention or neoadjuvant indications, which would optimize Atossa's capital deployment – particularly important given their
Moreover, the demonstrated activity in patients who progressed after tamoxifen therapy suggests potential positioning as a valuable second-line treatment option. This approach allows Atossa to potentially secure an initial approval in an area of high unmet need while simultaneously pursuing broader indications that could substantially expand their addressable market.
While the competitive landscape in metastatic breast cancer is challenging, (Z)-endoxifen's favorable safety profile coupled with its efficacy signals could position it as a differentiated therapy. The company's parallel engagement with the FDA on prevention and neoadjuvant indications demonstrates a comprehensive long-term strategy that balances near-term approval potential with broader market opportunities.
The strategic pivot toward a metastatic breast cancer indication for (Z)-endoxifen demonstrates sound clinical development planning. The reported
Particularly significant is the activity observed in patients who progressed on tamoxifen but subsequently responded to (Z)-endoxifen. This suggests the compound may overcome certain resistance mechanisms – a important advantage in hormone receptor-positive breast cancer where resistance inevitably develops. The mechanism likely relates to (Z)-endoxifen being a more potent SERM and the primary active metabolite of tamoxifen itself.
The >85% Ki-67 response rate in the neoadjuvant setting further validates the compound's biological activity, as Ki-67 reduction strongly correlates with improved long-term outcomes in hormone-sensitive breast cancer. Importantly, this effect was observed regardless of ovarian function status, suggesting efficacy across pre- and post-menopausal populations.
From a development perspective, focusing on metastatic disease provides a more efficient path through clinical trials while preserving future opportunities in prevention and early-stage settings. While the metastatic breast cancer landscape is competitive with established CDK4/6 inhibitor combinations, (Z)-endoxifen's favorable safety profile could position it as an important addition to the treatment armamentarium, particularly for patients who have progressed on existing endocrine therapies.
SEATTLE, March 11, 2025 (GLOBE NEWSWIRE) -- Atossa Therapeutics, Inc. (Nasdaq: ATOS) (“Atossa” or the “Company”), a clinical-stage biopharmaceutical company dedicated to the prevention and treatment of breast cancer, today announced its strategic decision to pursue a metastatic breast cancer indication for (Z)-endoxifen. Atossa believes that pursuing a metastatic indication may offer a more efficient regulatory pathway to deliver (Z)-endoxifen to women in urgent need, and simultaneously plans to work with the FDA to advance additional indications, such as breast cancer prevention and neoadjuvant therapy, that often require larger and longer clinical trials.
Addressing the High Unmet Need in Metastatic Breast Cancer
Metastatic breast cancer remains a significant area of unmet medical need, with current treatment options often providing limited durability of response and substantial side effects. (Z)-endoxifen, a potent and well-tolerated selective estrogen receptor modulator (SERM), has shown encouraging signals in previous clinical trials, which we believe supports its potential to fill this critical gap in treatment.
Promising Data from Phase 1 and Phase 2 Trials
(Z)-endoxifen has shown encouraging results in early-stage trials, which we believe reinforces its potential as a transformative therapy for breast cancer. Key findings from early clinical programs include:
- Significantly improved progression-free survival (PFS) in CDK4/6i-naïve patients: (Z)-endoxifen more than doubled the median PFS compared to tamoxifen (7.2 vs. 2.4 months), highlighting its potency in an endocrine-sensitive population.
- Substantial activity observed even after tamoxifen progression: Patients in the crossover arm who progressed on tamoxifen and switched to (Z)-endoxifen experienced clinical benefit, including partial responses and prolonged stable disease exceeding 2-3 years in some cases.
- Favorable safety profile: Despite its higher potency, (Z)-endoxifen has not shown unexpected safety concerns beyond what is typically seen with tamoxifen and has been generally well-tolerated.
Dr. Steven Quay, Chairman and Chief Executive Officer of Atossa Therapeutics, stated: “Our decision to advance (Z)-endoxifen into a metastatic breast cancer indication underscores our unwavering commitment to developing a best-in-class therapy for women facing this devastating disease. The encouraging clinical data that has been generated to date supports the potential of (Z)-endoxifen to provide a meaningful benefit to patients who have exhausted other treatment options. By pursuing this strategy, we believe we are not only addressing an urgent medical need but also fortifying the path forward for expanding (Z)-endoxifen’s role across the full spectrum of breast cancer prevention and treatment. We look forward to providing future updates as we execute this plan.”
The Strategic Advantage of a Metastatic Indication
We believe that pursuing an initial approval in metastatic breast cancer provides an efficient regulatory and clinical path to market, potentially allowing Atossa to more rapidly bring (Z)-endoxifen to patients who need it most. This approach can also strengthen the foundation for the expansion of (Z)-endoxifen into earlier-stage disease settings, where (Z)-endoxifen has already shown significant promise in reducing tumor proliferation and preventing recurrence.
Advancing Additional Indications in Prevention and Early-Stage Disease
Beyond metastatic disease, Atossa remains committed to demonstrating the broad clinical utility of (Z)-endoxifen across the breast cancer treatment paradigm. Since the release of compelling data at the end of 2024, the Company is actively engaging with the FDA to further define a regulatory path forward for additional indications, including in:
- Breast Cancer Prevention: Prior studies have indicated that (Z)-endoxifen can significantly reduce breast tissue density and estrogen receptor activity, key risk factors for developing breast cancer.
- Neoadjuvant Therapy: Data from early-stage patients indicate that the 4-week Ki-67 ≤
10% response rate remained consistently above 85 percent across all dose levels, regardless of the presence of ovarian function. These findings suggest that (Z)-endoxifen may effectively reduce tumor proliferation, which may lead to improved surgical outcomes and long-term prognosis.
Atossa Therapeutics remains dedicated to accelerating the development of (Z)-endoxifen with the goal of helping patients across all stages of breast cancer to benefit from its therapeutic potential.
About Atossa Therapeutics
Atossa Therapeutics, Inc. (Nasdaq: ATOS) is a clinical-stage biopharmaceutical company dedicated to transforming breast cancer treatment through innovative science and patient-focused solutions. The company’s lead product candidate, (Z)-endoxifen, is a highly potent SERM designed for use across the breast cancer spectrum, including prevention, neoadjuvant, adjuvant, and metastatic settings. Atossa is committed to advancing its robust clinical research programs to improve patient outcomes while creating sustainable value for shareholders. For more information, visit atossatherapeutics.com.
FORWARD LOOKING STATEMENTS
This press release contains certain information that may constitute forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. We may identify these forward-looking statements by the use of words such as “expect,” “potential,” “continue,” “may,” “will,” “should,” “could,” “would,” “seek,” “intend,” “plan,” “estimate,” “anticipate,” “believe,” “design,” “predict,” “future,” or other comparable words. All statements made in this press release that are not statements of historical fact, including statements regarding data related to the (Z)-endoxifen program, the safety, tolerability and efficacy of (Z)-endoxifen, the potential of (Z)-endoxifen as a breast cancer prevention and treatment agent, the potential indications that the Company may pursue for (Z)-endoxifen, the potential for (Z)-endoxifen to receive regulatory approval, benefits of the Company’s strategy of pursuing a metastatic indication for (Z)-endoxifen, the expected design and enrollment of trials and timing of data and related publications, and the potential market and growth opportunities for the Company, are forward-looking statements. Forward-looking statements in this press release are subject to risks and uncertainties that may cause actual results, outcomes, or the timing of actual results or outcomes, to differ materially from those projected or anticipated, including risks and uncertainties associated with: our ability to obtain patent coverage for our product candidates; macroeconomic conditions and increasing geopolitical instability; the expected timing of releasing data; any variation between interim or preliminary and final clinical results or analysis; actions and inactions by the FDA and foreign regulatory bodies; the outcome or timing of regulatory approvals needed by Atossa, including those needed to continue our planned (Z)-endoxifen trials; our ability to satisfy regulatory requirements; our ability to regain compliance or maintain compliance with the continued listing requirements of the Nasdaq Stock Market; our ability to successfully develop and commercialize new therapeutics; the success, costs and timing of our development activities, including our ability to successfully initiate or complete our clinical trials, including our (Z)-endoxifen trials; our anticipated rate of patient enrollment; our ability to contract with third-parties and their ability to perform adequately; our estimates on the size and characteristics of our potential markets; our ability to successfully defend litigation and other similar complaints and to establish and maintain intellectual property rights covering our products; whether we can successfully complete our clinical trial of oral (Z)-endoxifen in women with mammographic breast density and our trials of (Z)-endoxifen in women with breast cancer, and whether the studies will meet their objectives; our expectations as to future financial performance, expense levels and capital sources, including our ability to raise capital; our ability to attract and retain key personnel; our anticipated working capital needs and expectations around the sufficiency of our cash reserves; and other risks and uncertainties detailed from time to time in Atossa’s filings with the Securities and Exchange Commission, including without limitation its Annual Reports on Form 10-K and Quarterly Reports on 10-Q. Forward-looking statements are presented as of the date of this press release. Except as required by law, we do not intend to update any forward-looking statements, whether as a result of new information, future events or circumstances or otherwise.
Investor and Media Contact:
Michael Parks
VP, Investor and Public Relations
484-356-7105
michael.parks@atossainc.com
FAQ
What are the key clinical trial results for ATOS's (Z)-endoxifen in metastatic breast cancer?
How does ATOS's (Z)-endoxifen perform in neoadjuvant breast cancer therapy?
What is the safety profile of ATOS's (Z)-endoxifen compared to tamoxifen?
What additional indications is ATOS pursuing for (Z)-endoxifen beyond metastatic breast cancer?
