Atossa Therapeutics Announces Second Quarter 2025 Financial Results and Provides a Corporate Update
FDA Provides Positive Feedback, Clears Path for Atossa to File IND for (Z)-Endoxifen in Metastatic Breast Cancer; FDA Indicates No Additional Toxicity Studies Required
Strong I-SPY2 Results Reinforce Efficacy of Atossa's Monotherapy at 3-weeks
SEATTLE, Aug. 12, 2025 /PRNewswire/ -- Atossa Therapeutics, Inc. (NASDAQ:ATOS) (Atossa or the Company), a clinical-stage biopharmaceutical company developing innovative medicines for breast cancer, today announced its financial results for the second quarter ended June 30, 2025 and provided an update on recent company developments.
"Atossa continues to make meaningful and measurable progress across our pipeline, underscored by recent, highly constructive interactions with the FDA that further support our (Z)-endoxifen development strategy in metastatic breast cancer," stated Dr. Steven Quay, Chairman and CEO of Atossa Therapeutics. "With a strong balance sheet, we believe we are well-positioned to execute on our planned upcoming IND submission and advance our metastatic clinical program toward key value-creating milestones. We remain disciplined in our capital strategy and have deliberately chosen not to utilize our ATM facility at recent share price levels, which we believe significantly undervalue the true potential of our Company. As we progress toward multiple upcoming potential catalysts, we are confident that our focused execution, scientific rigor, and unwavering commitment to patients will demonstrate the substantial intrinsic value of Atossa and position (Z)-endoxifen to make a meaningful impact in the treatment of breast cancer."
Clinical & Regulatory Developments
Positive FDA Feedback on (Z)-Endoxifen Program - In July 2025, Atossa announced it received highly constructive written feedback from the U.S. Food and Drug Administration (FDA), supporting the Company's proposed dose optimization trial in estrogen receptor positive, human epidermal growth factor receptor 2 negative (ER+/HER2-) metastatic breast cancer and allowing the Company to meet the requirements of Project Optimus. The FDA agreed that existing clinical and nonclinical data are sufficient to initiate the monotherapy arm (Part A) of the study and agreed with the scientific rationale for combination therapy arms (Part B) using standard-of-care agents, such as CDK4/6 inhibitors, PI3K inhibitors, mTOR inhibitors, and capecitabine. The Agency also indicated that no additional general toxicity or neurotoxicity studies are required and confirmed that Atossa's cardiac safety assessment monitoring protocol is sufficient for the monotherapy portion of the trial. These developments support the Company's plan to file an Investigational New Drug (IND) application with the FDA, which is expected in Q4 2025.
Clinical Trial Readouts & Scientific Validation
I‑SPY 2 Endocrine Optimization Sub‑Study Results (Monotherapy with Low-Dose 10 mg (Z)-endoxifen), In May 2025, Atossa released full results from the Phase 2 pilot within the I‑SPY 2 trial. Among 20 women with stage II/III ER+, HER2‑ breast cancer.
Primary endpoint achieved with 95 percent of subjects completing at least 75 percent of planned dosing.
Median Ki‑67 dropped from 10.5 percent at baseline to 5 percent by Week 3, with 65 percent achieving Ki‑67 ≤ 10 percent. Ki-67 is a widely used biomarker in pathology to assess the extent to which cancer cells are dividing and is often correlated with tumor behavior and prognosis. The POETIC (Peri-Operative Endocrine Therapy for individualized Care) trial, a large phase 3 study conducted in the UK and sponsored by the Institute of Cancer Research and the Royal Marsden NHS Foundation Trust, demonstrated that early changes in Ki-67 are strongly prognostic. Published in 2020, the trial showed that women with ER+/HER2− breast cancer whose Ki-67 levels fell from >10 percent at baseline to ≤10 percent after just two weeks of neoadjuvant aromatase inhibitor therapy had a 5-year recurrence rate of 8.4 percent, compared to 21.5 percent in those whose Ki-67 remained above 10 percent.
Median functional tumor volume, as assessed by MRI, decreased by 77.7 percent from baseline to surgery, and the longest tumor diameter dropped by 36.8 percent from baseline to preoperative MRI.
Safety was favorable: adverse events were predominantly Grade 1; vasomotor symptoms (hot flushes) and fatigue were most common. Only three Grade 3 events (two skin infections, one post‑procedural infection) occurred in a single patient and were deemed unrelated to the study drug; no Grade 4 or Grade 5 events were reported.
I-SPY 2 - Endocrine Optimization Pilot Analysis (Combination therapy of 40 mg (Z)-endoxifen and Eli Lilly's abemaciclib)
Patient recruitment continues at a faster rate than anticipated, with 41 patients initiated as of July 29, 2025.
Other ongoing Phase 2 Programs - Atossa continues to evaluate (Z)-endoxifen in two other Phase 2 trials: one in women with ductal carcinoma in situ (DCIS) and one in women with ER+/HER2- breast cancer, as previously disclosed.
Intellectual Property & Patent Portfolio
New U.S. Patents - In mid‑May 2025, Atossa announced the issuance of U.S. Patent No. 12,281,056, containing 58 claims relating to the enteric oral formulations of (Z)-endoxifen, including features of improved purity, stability, and bioavailability.
Recent Patent Challenges - Two of Atossa's patents are currently the subject of post‑grant challenges (i.e., U.S. Patent Nos. 11,261,151 and 12,071,391), which may result in modification or invalidation of certain patent claims; however, such proceedings are common for high‑value pharmaceutical IP, and we remain confident in our ability to vigorously defend these patents. The majority of Atossa's intellectual property is unaffected. Atossa holds four additional issued U.S. patents with claims to endoxifen—U.S. Patent Nos. 11,680,036, 12,201,591, 12,275,684, and 12,281,056—with over 200 total claims covering proprietary manufacturing methods, stable crystalline forms, and multiple sustained‑release and enteric oral formulations of (Z)‑endoxifen. We believe that these patents, along with pending applications worldwide, provide substantial additional protection for our lead program.
Strategic Outlook & Upcoming Milestones
Atossa remains focused on executing its breast cancer development strategy. Key upcoming deliverables include:
Announcement of Contract Research Organization (CRO) selected to execute the metastatic dose ranging study in coordination with Atossa clinical personnel.
Disclosure of dose-ranging trial design, including specifics on patient selection criteria and combination treatment backbone.
Targeting IND submission in Q4 2025, in alignment with feedback under the FDA Project Optimus initiative.
Advancing enrollment and data generation from ongoing Phase 2 trials.
Working with the FDA on regulatory strategies for breast cancer indications beyond metastatic breast cancer, including treating women in the adjuvant setting, patients with DCIS, and in reducing the incidence of breast cancer in high-risk women.
Comparison of Three and Six Months Ended June 30, 2025 and 2024
Operating Expenses. Total operating expenses were $9.0 million and $16.5 million for the three and six months ended June 30, 2025, respectively, which was an increase of $1.9 million and $2.4 million from total operating expenses for the three and six months ended June 30, 2024 of $7.1 million and $14.1 million, respectively. Factors contributing to the increased operating expenses in the three and six months ended June 30, 2025 are explained below.
Research & Development (R&D) Expenses. The following table provides a breakdown of major categories within R&D expenses for the three and six months ended June 30, 2025 and 2024, together with the dollar change and percentage change in those categories (dollars in thousands):
For the Three Months Ended June 30,
For the Six Months Ended June 30,
2025
2024
Increase (Decrease)
% Increase (Decrease)
2025
2024
Increase (Decrease)
% Increase (Decrease)
Research and Development Expense
Clinical and non-clinical trials
$
4,089
$
2,501
$
1,588
63 %
$
6,836
$
5,384
$
1,452
27 %
Compensation
856
679
177
26 %
1,736
1,305
431
33 %
Professional fees and other
557
373
184
49 %
1,087
613
474
77 %
Research and Development Expense Total
$
5,502
$
3,553
$
1,949
55 %
$
9,659
$
7,302
$
2,357
