ATOS / Atossa Therapeutics, Inc. - SEC-Einreichungen, Jahresbericht, Proxy Statement

RESTRICTED STOCK UNIT AWARD AGREEMENT UNDER THE ATOSSA THERAPEUTICS, INC. 2020 STOCK INCENTIVE PLAN

Exhibit 10.2 RESTRICTED STOCK UNIT AWARD AGREEMENT UNDER THE ATOSSA THERAPEUTICS, INC. 2020 STOCK INCENTIVE PLAN Name of Grantee: No. of Restricted Stock Units: Grant Date: Pursuant to the Atossa Therapeutics, Inc. 2020 Stock Incentive Plan, as amended through the date hereof (the “Plan”), Atossa Therapeutics, Inc. (the “Company”) hereby grants an award of Restricted Stock Units (an “Award”) to th

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 7, 2026 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commission F

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 8, 2026 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commission F

Atossa Therapeutics Reports First Quarter 2026 Financial Results and Provides a Corporate Update

Exhibit 99.1 Atossa Therapeutics Reports First Quarter 2026 Financial Results and Provides a Corporate Update SEATTLE, WASHINGTON, May 8, 2026 — Atossa Therapeutics, Inc. (Nasdaq: ATOS) (Atossa or the Company), a clinical-stage biopharmaceutical company developing novel therapies in oncology and other areas of high unmet clinical need, today announces its financial results and provides an update o

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2026 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from XXXXXXXX XX, XXXX to XXXXXXXX XX, XXXX Commiss

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 13, 2026 Atossa Therapeutic

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 13, 2026 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissio

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Defin

ARS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark one) շ Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the fiscal year ended December 31, 2025 OR ն Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the transition period from: to Commission File Number: 001-35610 ATOSSA THERAP

Atossa Therapeutics Reports Fourth Quarter and Year-End 2025 Financial Results and Provides a Corporate Update

Exhibit 99.1 Atossa Therapeutics Reports Fourth Quarter and Year-End 2025 Financial Results and Provides a Corporate Update SEATTLE, March 25, 2026 — Atossa Therapeutics, Inc. (Nasdaq: ATOS) (Atossa or the Company), a clinical-stage biopharmaceutical company developing novel therapies in oncology and other areas of high unmet clinical need, today announces its financial results for the fourth quar

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark one) ☒ Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the fiscal year ended December 31, 2025 OR ☐ Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the transition period from: to Commission File Number: 001-3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 25, 2026 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissio

LIST OF SUBSIDIARIES

Exhibit 21.1 LIST OF SUBSIDIARIES Atossa Genetics UK Ltd. Atossa Genetics AUS Pty Ltd.

DESCRIPTION OF THE REGISTRANT’S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934

Exhibit 4.6 DESCRIPTION OF THE REGISTRANT’S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 The following is a description of the authorized capital stock of Atossa Therapeutics, Inc. (the “Company” or “we” or “our”). The following description of our common stock is a summary and does not purport to be complete. It is subject to and qualified in its entirety by

Exhibit 10.11# SEPARATION AGREEMENT RECITALS

10202 5th Ave NE, Suite 200 • Seattle, WA 98125 USA Exhibit 10.11# SEPARATION AGREEMENT This Separation Agreement (“Agreement”) is made as of November 15, 2025 (the “Execution Date”) between Heather Rees (“Employee”) and Atossa Therapeutics, Inc. (the “Company”). Employee and the Company will be referred to collectively as the “Parties.” RECITALS WHEREAS, Employee’s employment with the Company has

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☒ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☐ Defin

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 19, 2026 Atossa Therapeu

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 19, 2026 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commis

AT THE MARKET OFFERING AGREEMENT

EX-1.1 Exhibit 1.1 AT THE MARKET OFFERING AGREEMENT February 20, 2026 Rodman & Renshaw LLC 600 Lexington Avenue, 32nd Floor New York, NY 10022 Ladies and Gentlemen: Atossa Therapeutics, Inc., a corporation organized under the laws of Delaware (the “Company”), confirms its agreement (this “Agreement”) with Rodman & Renshaw LLC and its successors and permitted assigns (the “Manager”) as follows: 1.

Up to $50,000,000 Common Stock

424B5 Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-279367 PROSPECTUS SUPPLEMENT (To prospectus dated May 23, 2024) Up to $50,000,000 Common Stock We have entered into an At the Market Offering Agreement (the “Sales Agreement”) with Rodman & Renshaw LLC (“Rodman” or the “Sales Agent”) relating to shares of our common stock, $0.18 par value per share (the “common stock”).

The date of this prospectus supplement is February 20, 2026.

424B3 Filed Pursuant to Rule 424(b)(3) Registration No. 333-279367 Prospectus Supplement (To Prospectus dated May 23, 2024) This prospectus supplement supplements and amends the prospectus dated May 23, 2024 (the “Prospectus”), as supplemented and amended by that certain prospectus supplement dated November 19, 2024 covering the offering, issuance and sale of up to a maximum aggregate offering pri

FORM 8-K Item 3.01 Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 17, 2026 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commis

FORM 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 20, 2026 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commiss

CERTIFICATE OF AMENDMENT TO THE AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF ATOSSA THERAPEUTICS, INC.

Exhibit 3.1 CERTIFICATE OF AMENDMENT TO THE AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF ATOSSA THERAPEUTICS, INC. Atossa Therapeutics, Inc., a corporation organized and existing under the laws of the State of Delaware (the “Corporation”), hereby certifies as follows: FIRST: That the current name of the Corporation is Atossa Therapeutics, Inc., and the Corporation was originally incorporat

NASDAQ: ATOS www.atossatherapeutics.com Corporate Presentation January 8, 2026 COVER

NASDAQ: ATOS www.atossatherapeutics.com Corporate Presentation January 8, 2026 COVER Disclaimer This presentation may contain certain forward-looking statements related to Atossa Therapeutics, Inc. (the “Company”) that involve risks and uncertainties. 01 Actual results, outcomes, or the timing of actual results or outcomes may differ significantly from those discussed in forward-looking statements

FORM 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 9, 2026 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 6, 2026 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissi

Atossa Therapeutics Receives FDA “Study May Proceed” Letter for (Z)-Endoxifen Investigational New Drug Application for Metastatic Breast Cancer

Exhibit 99.1 Atossa Therapeutics Receives FDA “Study May Proceed” Letter for (Z)-Endoxifen Investigational New Drug Application for Metastatic Breast Cancer SEATTLE, WA, January 6, 2026 (GLOBE NEWSWIRE) — Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical-stage biopharmaceutical company developing innovative medicines for unmet medical needs, today announced that the U.S. Food and Drug Administr

PROPOSAL NO. 1 APPROVAL OF A REVERSE STOCK SPLIT PROPOSAL NO. 2 APPROVAL OF THE ADJOURNMENT OF THE SPECIAL MEETING, IF NECESSARY OR APPROPRIATE, TO SOLICIT ADDITIONAL PROXIES SECURITY OWNERSHIP OF BENEFICIAL OWNERS AND MANAGEMENT APPENDIX A CERTIFICA

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Defin

PROPOSAL NO. 1 APPROVAL OF A REVERSE STOCK SPLIT PROPOSAL NO. 2 APPROVAL OF THE ADJOURNMENT OF THE SPECIAL MEETING, IF NECESSARY OR APPROPRIATE, TO SOLICIT ADDITIONAL PROXIES SECURITY OWNERSHIP OF BENEFICIAL OWNERS AND MANAGEMENT APPENDIX A CERTIFIC

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☒ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☐ Defin

Atossa Therapeutics Details Accelerated FDA Strategy to Advance (Z)-Endoxifen Across Breast Cancer Continuum Company positioned to pursue expedited regulatory pathways in metastatic, neoadjuvant, and risk-reduction settings

Exhibit 99.1 Atossa Therapeutics Details Accelerated FDA Strategy to Advance (Z)-Endoxifen Across Breast Cancer Continuum Company positioned to pursue expedited regulatory pathways in metastatic, neoadjuvant, and risk-reduction settings SEATTLE, December 4, 2025 — Atossa Therapeutics, Inc. (Nasdaq: ATOS) (“Atossa” or the “Company”), a clinical-stage biopharmaceutical company focused on transformin

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 4, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commiss

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from XXXXXXXX XX, XXXX to XXXXXXXX XX, XXXX Commission File Number: 001-35610 ATOSSA THERAPEUTICS, INC.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 12, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commis

Atossa Therapeutics Reports Third Quarter 2025 Financial Results and Provides a Corporate Update Company reports progress to file planned IND for (Z)-endoxifen in mBC with CRO selection and streamlined development programs for potential 2026-NDA enab

Exhibit 99.1 Atossa Therapeutics Reports Third Quarter 2025 Financial Results and Provides a Corporate Update Company reports progress to file planned IND for (Z)-endoxifen in mBC with CRO selection and streamlined development programs for potential 2026-NDA enabling activities, including a Type C meeting with the FDA, to potentially accelerate (Z)-endoxifen in breast cancer risk reduction Appoint

EMPLOYMENT AGREEMENT

Exhibit 10.1 EMPLOYMENT AGREEMENT This EMPLOYMENT AGREEMENT (the “Agreement”) is entered into effective as of October 14, 2025 (the “Effective Date”), by and between Atossa Therapeutics, Inc. (the “Company”) and Mark Daniel (“Executive”). WHEREAS, the Company wishes to employ Executive as the Chief Financial Officer of the Company and Executive wishes to work in such capacity; and WHEREAS, the Com

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): October 14, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commiss

Atossa Appoints Mark Daniel, CPA, as Chief Financial Officer to Lead Finance, Systems, and Capital Strategy for Commercial Readiness 25+ year life-sciences finance leader brings revenue-forecasting rigor, public-company controls, and capital-markets

FOR IMMEDIATE RELEASE Exhibit 99.1 Atossa Appoints Mark Daniel, CPA, as Chief Financial Officer to Lead Finance, Systems, and Capital Strategy for Commercial Readiness 25+ year life-sciences finance leader brings revenue-forecasting rigor, public-company controls, and capital-markets experience as Atossa prepares for commercial operations with (Z)-endoxifen SEATTLE — October 14, 2025 — Atossa Ther

FORM 8-K The information in this Current Report on Form 8-K, including the exhibit hereto, shall not be deemed to be “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of Sec

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 26, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commi

NASDAQ: ATOS www.atossatherapeutics.com Corporate Presentation September 26, 2025 COVER

NASDAQ: ATOS www.atossatherapeutics.com Corporate Presentation September 26, 2025 COVER Disclaimer This presentation may contain certain forward-looking statements related to or Atossa Therapeutics, Inc. (the “Company”) that involve risks and uncertainties. 01 Actual results and events may differ significantly from results and events discussed in forward-looking statements. 02 Factors that might c

Atossa Therapeutics Announces Regulatory Strategy Aimed at Accelerating Development of Low-Dose (Z)-Endoxifen for Breast Cancer Risk Reduction Type C FDA Meeting Requested, Update Expected by Year-End 2025

Exhibit 99.1 Atossa Therapeutics Announces Regulatory Strategy Aimed at Accelerating Development of Low-Dose (Z)-Endoxifen for Breast Cancer Risk Reduction Type C FDA Meeting Requested, Update Expected by Year-End 2025 SEATTLE — September 8, 2025 —Atossa Therapeutics, Inc. (Nasdaq: ATOS; “Atossa” or the “Company”) announced today it has requested a Type C meeting with the U.S. Food and Drug Admini

FORM 8-K Item 8.01 Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): September 8, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commis

FORM 8-K Item 3.01 Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 21, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from XXXXXXXX XX, XXXX to XXXXXXXX XX, XXXX Commission File Number: 001-35610 ATOSSA THERAPEUTICS, INC.

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

Exhibit 99.1 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, August 12, 2025 — Atossa Therapeut

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 12, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissi

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 13, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commission

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2025 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from XXXXXXXX XX, XXXX to XXXXXXXX XX, XXXX Commission File Number: 001-35610 ATOSSA THERAPEUTICS, INC.

Atossa Therapeutics Announces First Quarter 2025 Financial Results and Provides a Corporate Update Announced strategic plan to advance (Z)-endoxifen for metastatic breast cancer indication Enhanced (Z)-endoxifen intellectual property portfolio with t

Exhibit 99.1 Atossa Therapeutics Announces First Quarter 2025 Financial Results and Provides a Corporate Update Announced strategic plan to advance (Z)-endoxifen for metastatic breast cancer indication Enhanced (Z)-endoxifen intellectual property portfolio with three new U.S. patents, expanding IP portfolio to more than 200 patent claims related to (Z)-endoxifen Ended first quarter 2025 with $65.1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 8, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commission F

FORM 8-K Item 8.01 Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 7, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commission

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Defin

As filed with the Securities and Exchange Commission on March 26, 2025

As filed with the Securities and Exchange Commission on March 26, 2025 Registration No.

ARS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark one) Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the fiscal year ended December 31, 2024 OR Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the transition period from: to Commission File Number: 001-35610 ATOSSA THERAPEUTI

Filing Fee Table

Exhibit 107 CALCULATION OF FILING FEE TABLE Form S-8 Atossa Therapeutics, Inc. Table 1 – Newly Registered Securities Security Type Security Class Title Fee Calculation Rule Amount Registered (1) Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Equity Common Stock, $0.18 par value 457(a) 12,000,000 $0.725(2) $8,700,000(2) $153.10 per $1,0

List of Subsidiaries

Exhibit 21.1 LIST OF SUBSIDIARIES Atossa Genetics UK Ltd. Atossa Genetics AUS Pty Ltd.

Atossa Therapeutics Announces Full Year 2024 Financial Results and Provides Corporate Update Ended 2024 with $71.1 million of cash and cash equivalents and no debt Conference Call and Webcast Scheduled for Tuesday, March 25, 2025, at 8:30 a.m. Easter

EX-99.1 2 atos-ex991.htm EX-99.1 Exhibit 99.1 Atossa Therapeutics Announces Full Year 2024 Financial Results and Provides Corporate Update Ended 2024 with $71.1 million of cash and cash equivalents and no debt Conference Call and Webcast Scheduled for Tuesday, March 25, 2025, at 8:30 a.m. Eastern Time SEATTLE, March 25, 2025 - Atossa Therapeutics, Inc. (Nasdaq: ATOS) (“Atossa” or the “Company”), a

Description of Securities Registered Pursuant to Section 12 of the Securities Exchange Act of 1934.

Exhibit 4.6 DESCRIPTION OF THE REGISTRANT’S SECURITIES REGISTERED PURSUANT TO SECTION 12 OF THE SECURITIES EXCHANGE ACT OF 1934 The following is a description of the authorized capital stock of Atossa Therapeutics, Inc. (the “Company” or “we” or “our”). The following description of our common stock is a summary and does not purport to be complete. It is subject to and qualified in its entirety by

Insider Trading Policy

Exhibit 19.1 ATOSSA THERAPEUTICS, INC. STATEMENT OF COMPANY POLICY ON INSIDER TRADING AND DISCLOSURE This memorandum sets forth the policy of Atossa Therapeutics, Inc. (the “Company”) regarding trading in the Company’s securities as described below and the disclosure of information concerning the Company. This Statement of Company Policy on Insider Trading and Disclosure (the “Insider Trading Poli

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark one) ☒ Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the fiscal year ended December 31, 2024 OR ☐ Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the transition period from: to Commission File Number: 001-3

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 25, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissio

Atossa Therapeutics Announces Plans to Pursue Metastatic Breast Cancer Indication for (Z)-Endoxifen and Continued Engagement with FDA on Additional Indications

Exhibit 99.1 Atossa Therapeutics Announces Plans to Pursue Metastatic Breast Cancer Indication for (Z)-Endoxifen and Continued Engagement with FDA on Additional Indications SEATTLE, March 11, 2025 – 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 strategi

Financial Statements and Exhibits, Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 11, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissio

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): February 21, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commis

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): January 30, 2025 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commiss

Atossa Therapeutics Responds to PTAB Ruling on U.S. Patent No. 11,572,334 and Announces the Issuance of U.S. Patent No. 12,201,591

Exhibit 99.1 Atossa Therapeutics Responds to PTAB Ruling on U.S. Patent No. 11,572,334 and Announces the Issuance of U.S. Patent No. 12,201,591 SEATTLE, January 30, 2025 - Atossa Therapeutics, Inc. (Nasdaq: ATOS) (“Atossa” or the “Company”), a clinical-stage biopharmaceutical company dedicated to the prevention and treatment of breast cancer, today issued the following statement in response to the

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): December 10, 2024 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commis

Atossa Therapeutics to Present Pharmacokinetic and Tolerability Data from Phase 2 EVANGELINE Trial at the 2024 San Antonio Breast Cancer Symposium

Atossa Therapeutics to Present Pharmacokinetic and Tolerability Data from Phase 2 EVANGELINE Trial at the 2024 San Antonio Breast Cancer Symposium SEATTLE, December 10, 2024 - Atossa Therapeutics, Inc.

Open Market Sale Agreement SM, dated November 19, 2024, by and between Atossa Therapeutics, Inc. and Jefferies LLC

Exhibit 1.1 OPEN MARKET SALE AGREEMENTSM November 19, 2024 JEFFERIES LLC 520 Madison Avenue New York, New York 10022 Ladies and Gentlemen: Atossa Therapeutics, Inc., a Delaware corporation (the “Company”), proposes, subject to the terms and conditions stated herein, to issue and sell from time to time through Jefferies LLC, as sales agent and/or principal (the “Agent”), shares of the Company’s com

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 19, 2024 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commis

Up to $100,000,000 Common Stock

Filed Pursuant to Rule 424(b)(5)  Registration No. 333-279367 PROSPECTUS SUPPLEMENT Up to $100,000,000 Common Stock We have entered into an Open Market Sale AgreementSM (the “Sale Agreement”) with Jefferies LLC (“Jefferies” or the “Sales Agent”) relating to shares of our common stock, $0.18 par value per share. Under this prospectus supplement and the accompanying prospectus, and in accordance wit

ATOS / Atossa Therapeutics, Inc. / VANGUARD GROUP INC Passive Investment

SC 13G/A 1 UnitedStates13GAtossaTher.txt 240.13d-102 Schedule 13G - Information to be included in statements filed pursuant to 240.13d-1(b), (c), and (d) and amendments thereto filed pursuant to 240.13d-2. Securities and Exchange Commission, Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No. 1)* (Name of Issuer) Atossa Therapeutics Inc (Title of Class of S

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 12, 2024 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commis

Atossa Therapeutics Announces Third Quarter 2024 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces Third Quarter 2024 Financial Results and Provides Corporate Update • Announced positive topline results from KARISMA-Endoxifen Phase 2 study which demonstrated that low doses of (Z)-endoxifen significantly reduced mammographic breast density (MBD), addressing a key breast cancer risk factor • Released a preliminary analysis from I-SPY 2 Endocrine Optimiza

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from XXXXXXXX XX, XXXX to XXXXXXXX XX, XXXX Commission File Number: 001-35610 ATOSSA THERAPEUTICS, INC.

ATOS / Atossa Therapeutics, Inc. / BlackRock, Inc. Passive Investment

SC 13G 1 us04962h5063110824.txt us04962h5063110824.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: ) ATOSSA THERAPEUTICS, INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 04962H506 - (CUSIP Number) September 30, 2024 - (Date of Event Which Requires Filing of this Statement) Check the appropriate

ATOS / Atossa Therapeutics, Inc. / VANGUARD GROUP INC Passive Investment

SC 13G/A 1 UnitedStates13GAtossaTher.txt 240.13d-102 Schedule 13G - Information to be included in statements filed pursuant to 240.13d-1(b), (c), and (d) and amendments thereto filed pursuant to 240.13d-2. Securities and Exchange Commission, Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No. )* (Name of Issuer) Atossa Therapeutics Inc (Title of Class of Se

Atossa Therapeutics Reports Positive KARISMA-Endoxifen Trial Results: (Z)-Endoxifen Shown to Significantly Reduce Mammographic Breast Density, Potentially Paving the Way for Innovative Cancer Prevention Strategies

Exhibit 99.1 Atossa Therapeutics Reports Positive KARISMA-Endoxifen Trial Results: (Z)-Endoxifen Shown to Significantly Reduce Mammographic Breast Density, Potentially Paving the Way for Innovative Cancer Prevention Strategies SEATTLE, November 4, 2024 - Atossa Therapeutics, Inc. (Nasdaq: ATOS) ("Atossa" or the "Company"), a clinical-stage biopharmaceutical company developing innovative medicines

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): November 4, 2024 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commiss

ATOS / Atossa Therapeutics, Inc. / BlackRock, Inc. Passive Investment

us04962h5063102224.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: ) ATOSSA THERAPEUTICS, INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 04962H506 - (CUSIP Number) September 30, 2024 - (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursu

For the Three Months Ended June 30,

Exhibit 99.1 Atossa Therapeutics Announces Second Quarter 2024 Financial Results and Provides Corporate Update • Presented data showing 100% disease control rate after 24-week treatment with (Z)-Endoxifen in 40mg cohort of Phase 2 EVANGELINE study at the American Association for Cancer Research (AACR) Annual Meeting • Completed enrollment in 80mg PK Run-in Cohort for EVANGELINE trial • Completed P

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): August 12, 2024 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from XXXXXXXX XX, XXXX to XXXXXXXX XX, XXXX Commission File Number: 001-35610 ATOSSA THERAPEUTICS, INC.

Employment Agreement with Heather Rees Dated July 1, 2024

Exhibit 10.2 EMPLOYMENT AGREEMENT This EMPLOYMENT AGREEMENT (the “Agreement”) is entered into as of July 1, 2024 (the “Effective Date”), by and between Atossa Therapeutics Inc. (the “Company”) and Heather Rees (“Executive”). WHEREAS, the Company wishes to employ Executive as the Chief Financial Officer of the Company and Executive wishes to work in such capacity; and WHEREAS, the Company and Execu

Certificate of Amendment to Amended and Restated Certificate of Incorporation

Exhibit 3.1 CERTIFICATE OF AMENDMENT TO THE AMENDED AND RESTATED CERTIFICATE OF INCORPORATION OF ATOSSA THERAPEUTICS, INC. Atossa Therapeutics, Inc., a corporation organized and existing under the laws of the State of Delaware (the “Corporation”), hereby certifies as follows: FIRST: That the current name of the Corporation is Atossa Therapeutics, Inc., and the Corporation was originally incorporat

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 27, 2024 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commission

2020 Stock Incentive Plan, as Amended

Exhibit 10.1 ATOSSA THERAPEUTICS, INC. 2020 STOCK INCENTIVE PLAN (Most Recently Amended effective as of June 27, 2024) SECTION 1. GENERAL PURPOSE OF THE PLAN; DEFINITIONS The name of the plan is the Atossa Therapeutics, Inc. 2020 Stock Incentive Plan (the “Plan”). The purpose of the Plan is to encourage and enable the officers, employees, Non-Employee Directors and other key persons (including Con

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Defin

107 Spring Street, Seattle, WA 98104

May 21, 2024 VIA EDGAR United States Securities and Exchange Commission Division of Corporation Finance 100 F Street, N.

LETTER

United States securities and exchange commission logo May 21, 2024 Steven Quay Chairman, Chief Executive Officer and President Atossa Therapeutics Inc.

May 14, 2024

May 14, 2024 VIA EDGAR Securities and Exchange Commission Division of Corporation Finance 100 F Street, N.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from XXXXXXXX XX, XXXX to XXXXXXXX XX, XXXX Commission File Number: 001-35610 ATOSSA THERAPEUTICS, INC.

Filing Fee Table

Calculation of Filing Fee Tables Form S-3 (Form Type) Atossa Therapeutics, Inc. (Exact Name of Registrant as Specified in its Charter) Table 1: Newly Registered and Carry Forward Securities Security Type Security Class Title Fee Calculation or Carry Forward Rule Amount Registered Proposed Maximum Offering Price Per Unit Maximum Aggregate Offering Price Fee Rate Amount of Registration Fee Carry For

Form of Senior Indenture

Exhibit 4.1 ATOSSA THERAPEUTICS, INC. Debt Securities Indenture Dated as of [ ] [ ]., as Trustee CROSS-REFERENCE TABLE This Cross-Reference Table is not a part of the Indenture TIA Section Indenture Section 310(a)(1) 7.10 (a)(2) 7.10 (a)(3) N.A. (a)(4) N.A. (b) 7.08; 7.10; 12.02 311(a) 7.11 (b) 7.11 (c) N.A. 312(a) 2.05 (b) 12.03 (c) 12.03 313(a) 7.06 (b)(1) N.A. (b)(2) 7.06 (c) 12.02 (d) 7.06 314

Atossa Therapeutics Announces First Quarter 2024 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces First Quarter 2024 Financial Results and Provides Corporate Update • Presented data from EVANGELINE study showing 100% disease control rate at 24-weeks • Initiated study evaluating (Z)-endoxifen in combination with abemaciclib (VERZENIO®) • Ended first quarter 2024 with $84.0 million of cash and cash equivalents and no debt SEATTLE, May 13, 2024— Atossa T

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM S-3 REGISTRATION STATEMENT THE SECURITIES ACT OF 1933 ATOSSA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter)

As filed with the Securities and Exchange Commission on May 13, 2024 Registration Statement No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 13, 2024 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commission

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 (Amendment No. ) Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☒ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☐ Defin

ARS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark one) ☒ Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the fiscal year ended December 31, 2023 OR ☐ ☐ Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the transition period from: to Commission File Number: 001-35610 ATOSSA THER

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K/A CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K/A CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 1, 2024 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissi

Atossa Therapeutics Announces Year-End 2023 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces Year-End 2023 Financial Results and Provides Corporate Update • Fully enrolled two Phase 2 studies with data from both expected in the second half of 2024 • First patient dosed in new Phase 2 breast cancer prevention study • Data from ongoing Phase 2 EVANGELINE study scheduled to be presented at 2024 AACR Annual Meeting • Ended 2023 with $88.5 million of

Employment Agreement with Greg Weaver Dated June 1, 2023

Exhibit 10.12 EMPLOYMENT AGREEMENT This EMPLOYMENT AGREEMENT (the “Agreement”) is entered into as of June 1, 2023 (the “Effective Date”), by and between Atossa Therapeutics Inc. (the “Company”) and Gregory Weaver (“Executive”). WHEREAS, the Company wishes to employ Executive as the Executive Vice President and Chief Financial Officer of the Company and Executive wishes to work in such capacity; an

Incentive Compensation Clawback Policy

Exhibit 97.1 INCENTIVE COMPENSATION CLAWBACK POLICY Recoupment of Incentive-Based Compensation It is the policy of Atossa Therapeutics, Inc. (the “Company”) that, in the event the Company is required to prepare an accounting restatement of the Company’s financial statements due to material non-compliance with any financial reporting requirement under the federal securities laws (including any such

Employment Letter with Heather Rees Dated October 6, 2023

EXHIBIT 10.13 [*] = Certain confidential information contained in this document, marked by brackets, has been omitted because it is both (i) not material and (ii) is the type that the registrant treats as private or confidential. October 6, 2023 Heather Rees [*] *Delivered via email Dear Heather, A significant factor in our success at Atossa Therapeutics is our people and the effort and talent the

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark one) ☒ Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the fiscal year ended December 31, 2023 OR ☐ Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the transition period from: to Commission File Number: 001-3

Atossa Therapeutics Announces Year-End 2023 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces Year-End 2023 Financial Results and Provides Corporate Update • Fully enrolled two Phase 2 studies with data from both expected in the second half of 2024 • First patient dosed in new Phase 2 breast cancer prevention study • Data from ongoing Phase 2 EVANGELINE study scheduled to be presented at 2024 AACR Annual Meeting • Ended 2023 with $88.5 million of

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): April 1, 2024 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commission

List of Subsidiaries

Exhibit 21.1 LIST OF SUBSIDIARIES Atossa Genetics UK Ltd. Atossa Genetics AUS Pty Ltd.

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 15, 2024 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissio

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): March 09, 2024 Atossa Therapeutics, Inc. (Exact name of Registrant as Specified in Its Charter) Delaware 001-35610 26-4753208 (State or Other Jurisdiction of Incorporation) (Commissio

Atossa Therapeutics Appoints Breast Cancer Specialist Tessa Cigler, M.D., M.P.H. to its Board of Directors

EXHIBIT 99.1 Atossa Therapeutics Appoints Breast Cancer Specialist Tessa Cigler, M.D., M.P.H. to its Board of Directors SEATTLE, March 12, 2024 — Atossa Therapeutics, Inc. (Nasdaq: ATOS) (“Atossa” or the “Company”), a clinical stage biopharmaceutical company developing innovative medicines in areas of significant unmet medical need in oncology with a focus on breast cancer, today announced that Te

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35610 ATOSS

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): November 13, 2023 Atossa Therapeu

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): November 13, 2023 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commis

Atossa Therapeutics Announces Third Quarter 2023 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces Third Quarter 2023 Financial Results and Provides Corporate Update ● Achieved significant enrollment milestones in ongoing Phase 2 clinical trials ● Four ongoing Phase 2 studies evaluating (Z)-endoxifen, including recently announced study in DCIS ● Ended third quarter 2023 with $94.0 million of cash and cash equivalents SEATTLE, November 13, 2023 (GLOBE N

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): November 9, 2023 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commiss

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): October 6, 2023 (October 2, 2023)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): October 6, 2023 (October 2, 2023) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorp

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): September 28, 2023 (September 26,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): September 28, 2023 (September 26, 2023) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report: August 30, 2023 Atossa Therapeutics, Inc. (Exact name of registrant

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report: August 30, 2023 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commission File Number) (I.R.S. Employer I

Atossa Therapeutics Announces Second Quarter 2023 Financial Results and Provides Corporate Update

EXHIBIT 99.1 Atossa Therapeutics Announces Second Quarter 2023 Financial Results and Provides Corporate Update ● Achieved significant enrollment milestones in three ongoing Phase 2 clinical trials ● Broadened patent protection for proprietary (Z)-endoxifen ● Strengthened management team with appointment of Greg Weaver as Chief Financial Officer ● Ended second quarter 2023 with $99.4 million of cas

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): August 14, 2023 Atossa Therapeuti

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): August 14, 2023 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commissi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35610 ATOSSA THERAPEUTICS, INC.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): July 13, 2023 (July 13, 2023) Ato

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): July 13, 2023 (July 13, 2023) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporat

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): June 28, 2023 (June 27, 2023) Ato

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): June 28, 2023 (June 27, 2023) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporat

Atossa Therapeutics Announces $10M Stock Repurchase Program

Exhibit 99.1 Atossa Therapeutics Announces $10M Stock Repurchase Program SEATTLE, June 27, 2023 (GLOBE NEWSWIRE) — Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical stage biopharmaceutical company developing innovative proprietary medicines to address significant unmet needs in oncology with a focus on breast cancer, today announces that its Board of Directors has approved a share repurchase pr

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): June 23, 2023 (June 21, 2023) Ato

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): June 23, 2023 (June 21, 2023) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporat

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): June 1, 2023 (May 26, 2023) Atoss

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): June 1, 2023 (May 26, 2023) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporatio

Financial Statements and Exhibits, Changes in Registrant's Certifying Accountant

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): May 22, 2023 (May 17, 2023) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporatio

Letter from BDO USA LLP, dated May 22, 2023

Exhibit 16.1 May 22, 2023 Securities and Exchange Commission 100 F Street N.E. Washington, D.C. 20549 We have been furnished with a copy of the response to Item 4.01 of Form 8-K for the event that occurred on May 17, 2023, to be filed by our former client, Atossa Therapeutics, Inc. We agree with the statements made in response to that Item insofar as they relate to our Firm. Very truly yours, /s/

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): May 15, 2023 Atossa Therapeutics,

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): May 15, 2023 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commission

Atossa Therapeutics Announces First Quarter 2023 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces First Quarter 2023 Financial Results and Provides Corporate Update ● Two Phase 2 trials investigating (Z)-endoxifen in neoadjuvant setting initiated and are enrolling patients ● Full enrollment of Phase 2 KARISMA mammographic breast density study expected by end of 2023 ● Ended first quarter 2023 with $103.9 million of cash and cash equivalents and no deb

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35610 ATOSSA THERAPEUTICS, INC.

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): May 4, 2023 (May 4, 2023) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No.1)

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No.1) Filed by the Registrant ☑ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☐ Defin

Amended and Restated Bylaws

Exhibit 3.2 AMENDED AND RESTATED BY-LAWS OF ATOSSA THERAPEUTICS, INC. (the “Corporation”) ARTICLE I Stockholders SECTION 1. Annual Meeting. The annual meeting of stockholders (any such meeting being referred to in these By-laws as an “Annual Meeting”) shall be held at the hour, date and place within or without the United States which is fixed by the Board of Directors, which time, date and place m

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): April 26, 2023 Atossa Therapeutic

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): April 26, 2023 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commissio

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): April 4, 2023 (April 4, 2023) Ato

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): April 4, 2023 (April 4, 2023) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporat

ARS

1 Atossa Therapeutics, Inc. 107 Spring Street Seattle, Washington 98104 NOTICE OF ANNUAL MEETING OF STOCKHOLDERS To Be Held on May 4, 2023 at 6:00 A.M. Pacific Time Virtual Meeting to be Held Live via the Internet at: http://www.viewproxy.com/AtossaTherapeutics/2023/htype.asp Technical Support Contact: [email protected] or call 1-866-612-8937 Dear Stockholder: You are cordially invited

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No.  )

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 (Amendment No.  ) Filed by the Registrant ☑ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☑ Defi

List of Subsidiaries

Exhibit 21.1 LIST OF SUBSIDIARIES Atossa Genetics UK Ltd. Atossa Genetics AUS Pty Ltd.

Form of Indemnification Agreement

EXHIBIT 10.3 ATOSSA THERAPEUTICS, INC. INDEMNIFICATION AGREEMENT This Indemnification Agreement (“Agreement”) is made effective as of January 6, 2020 (the “Effective Date”) by and between Atossa Therapeutics, Inc., a Delaware corporation (the “Company”), and (“Indemnitee”). RECITALS WHEREAS, the Company, which is organized under the General Corporation Law of the State of Delaware (“DGCL”), wishes

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): March 22, 2023 Atossa Therapeutic

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): March 22, 2023 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commissio

Period-Period Change

EXHIBIT 99.1 Atossa Therapeutics Announces Year-End 2022 Financial Results and Provides Corporate Update SEATTLE, March 22, 2023 (GLOBE NEWSWIRE) — Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical stage biopharmaceutical company developing innovative proprietary medicines to address significant unmet needs in cancer, today announced financial results for the fiscal quarter and fiscal year ende

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark one) ☒ Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the fiscal year ended December 31, 2022 OR ☐ Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the transition period from: to Commission File Number: 001-35610 ATOSSA THERAP

Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): March 13, 2023 (March 10, 2023) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorpor

ATOS / Atossa Therapeutics Inc / VANGUARD GROUP INC - SCHEDULE 13G/A Passive Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 (Amendment No.: 1)* Name of issuer: Atossa Therapeutics Inc. Title of Class of Securities: Common Stock CUSIP Number: 04962H506 Date of Event Which Requires Filing of this Statement: December 30, 2022 Check the appropriate box to designate the rule pursuant to which this Schedule is fil

Atossa Therapeutics Announces Third Quarter 2022 Financial Results and Provides Corporate Update

EXHIBIT 99.1 Atossa Therapeutics Announces Third Quarter 2022 Financial Results and Provides Corporate Update SEATTLE, November 7, 2022 (GLOBE NEWSWIRE) - Atossa Therapeutics, Inc. (Nasdaq: ATOS), today announces financial results for the fiscal quarter ended September 30, 2022, and provides an update on recent company developments. Atossa is a clinical-stage biopharmaceutical company seeking to d

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2022 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35610 ATOSSA THERAPEUTICS, INC.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): November 7, 2022 Atossa Therapeut

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): November 7, 2022 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commiss

Notice of Delisting or Failure to Satisfy a Continued Listing Rule or Standard; Transfer of Listing

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): October 7, 2022 (October 5, 2022) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorp

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): August 8, 2022 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commissio

Atossa Therapeutics Announces Second Quarter 2022 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces Second Quarter 2022 Financial Results and Provides Corporate Update SEATTLE, August 8, 2022 (GLOBE NEWSWIRE) - Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical-stage biopharmaceutical company seeking to develop innovative proprietary medicines in oncology and infectious disease with a current focus on breast cancer and COVID-19, today announces financ

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2022 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35610 ATOSSA THERAPEUTICS, INC.

ATOS / Atossa Therapeutics Inc / BlackRock Inc. Passive Investment

us04962h5063070822.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: ) ATOSSA THERAPEUTICS, INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 04962H506 - (CUSIP Number) June 30, 2022 - (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursuant t

Other Events

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): July 7, 2022 (July 1, 2022) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporatio

Regulation FD Disclosure

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): July 1, 2022 (June 28, 2022) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporati

Regulation FD Disclosure

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): June 6, 2022 (June 1, 2022) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporatio

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): May 16, 2022 (May 13, 2022) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporatio

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2022 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35610 ATOSSA THERAPEUTICS, INC.

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): May 9, 2022 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commission F

Atossa Therapeutics Announces First Quarter 2022 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces First Quarter 2022 Financial Results and Provides Corporate Update SEATTLE, May 09, 2022 (GLOBE NEWSWIRE) - Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical-stage biopharmaceutical company seeking to develop innovative proprietary medicines in oncology and infectious disease with a current focus on breast cancer and COVID-19, today announces financial

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 Filed by the Registrant ? Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ? Definitive Proxy State

PRELIMINARY PROXY STATEMENT – SUBJECT TO COMPLETION UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934

PRELIMINARY PROXY STATEMENT ? SUBJECT TO COMPLETION UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark one) ? Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the fiscal year ended December 31, 2021 OR ? Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the transition period from: to Commission File Number 001-35

Atossa Therapeutics Announces Year-End 2021 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces Year-End 2021 Financial Results and Provides Corporate Update SEATTLE, February 28, 2022 (GLOBE NEWSWIRE) - Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical-stage biopharmaceutical company seeking to develop innovative medicines in oncology and infectious disease with a current focus on breast cancer and COVID-19, today announces financial results for

List of Subsidiaries

Exhibit 22.1 LIST OF SUBSIDIARIES Atossa Genetics UK Ltd. Atossa Genetics AUS Pty Ltd.

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): February 28, 2022 (February 24, 2022) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of in

ATOS / Atossa Therapeutics Inc / CVI Investments, Inc. - SC 13G/A Passive Investment

CUSIP No: 04962H506 SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO ? 240.13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO ? 240.13d-2. (Amendment No. 1)* Atossa Therapeutics, Inc. (Name of Issuer) Common Stock, $0.18 par value per share (Title of Class of Securities) 04962H506 (CUSIP Num

ATOS / Atossa Therapeutics Inc / VANGUARD GROUP INC - SCHEDULE 13G Passive Investment

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Schedule 13G Under the Securities Exchange Act of 1934 Name of issuer: Atossa Therapeutics Inc. Title of Class of Securities: Common Stock CUSIP Number: 04962H506 Date of Event Which Requires Filing of this Statement: December 31, 2021 Check the appropriate box to designate the rule pursuant to which this Schedule is filed: ☒ Rule 13d-1(b)

ATOS / Atossa Therapeutics Inc / BlackRock Inc. Passive Investment

us04962h5063020422.txt SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No: ) ATOSSA THERAPEUTICS, INC - (Name of Issuer) Common Stock - (Title of Class of Securities) 04962H506 - (CUSIP Number) December 31, 2021 - (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the rule pursua

ATOS / Atossa Therapeutics Inc / Empery Asset Management, LP - ATOSSA THERAPEUTICS, INC. Passive Investment

SC 13G/A 1 p22-0101sc13ga.htm ATOSSA THERAPEUTICS, INC. SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. 1)* Atossa Therapeutics, Inc. (Name of Issuer) Common Stock, par value $0.18 (Title of Class of Securities) 04962H506 (CUSIP Number) December 31, 2021 (Date of event which requires filing of this statement) Check the

Atossa Therapeutics Announces Third Quarter 2021 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces Third Quarter 2021 Financial Results and Provides Corporate Update SEATTLE, November 15, 2021 (GLOBE NEWSWIRE) - Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical-stage biopharmaceutical company seeking to develop innovative proprietary medicines in oncology and infectious disease with a current focus on breast cancer and COVID-19, today announces fina

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): November 15, 2021 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commis

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2021 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35610 ATOSSA THERAPEUTICS, INC.

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): October 6, 2021 (October 6, 2021) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorp

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 Filed by the Registrant ? Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ? Definitive Proxy State

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): September 8, 2021 (September 7, 2021) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of in

Current Report

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): August 13, 2021 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commissi

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended June 30, 2021 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35610 ATOSSA THERAPEUTICS, INC.

Atossa Therapeutics Announces Second Quarter 2021 Financial Results - Provides Corporate Update and Information about Upcoming Stockholder Meeting

Exibit 99.1 Atossa Therapeutics Announces Second Quarter 2021 Financial Results - Provides Corporate Update and Information about Upcoming Stockholder Meeting SEATTLE, August 13, 2021 (GLOBE NEWSWIRE) - Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical-stage biopharmaceutical company seeking to discover and develop innovative medicines in oncology and infectious disease with a current focus on

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 Filed by the Registrant ? Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ? Definitive Proxy State

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 Filed by the Registrant ? Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ? Definitive Proxy State

Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers, Submission of Matters to a Vote of Security Holders

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): May 18, 2021 (May 14, 2021) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporatio

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ? QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2021 OR ? TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35610 ATOSSA THERAPEUTICS, INC.

Atossa Therapeutics Announces First Quarter 2021 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces First Quarter 2021 Financial Results and Provides Corporate Update SEATTLE, May 14, 2021 (GLOBE NEWSWIRE) - Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical-stage biopharmaceutical company seeking to discover and develop innovative medicines in oncology and infectious disease with a current focus on breast cancer and COVID-19, today announces financia

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): May 14, 2021 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commission

- FORM DEFA14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 Filed by the Registrant ? Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ? Definitive Proxy State

VIA EDGAR

VIA EDGAR April 27, 2021 United States Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F Street, N.

LETTER

United States securities and exchange commission logo April 26, 2021 Steven C. Quay, M.D., Ph.D. Chief Executive Officer and President Atossa Therapeutics, Inc. 107 Spring Street Seattle, Washington 98104 Re: Atossa Therapeutics, Inc. Registration Statement on Form S-3 Filed April 21, 2021 File No. 333-255411 Dear Dr. Quay: This is to advise you that we have not reviewed and will not review your r

- FORM S-3

Table of Contents As filed with the Securities and Exchange Commission on April 21, 2021 Registration Statement No.

- FORM DEF 14A

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 Filed by the Registrant ? Filed by a Party other than the Registrant ? Check the appropriate box: ? Preliminary Proxy Statement ? Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ? Definitive Proxy State

- FORM PRE 14A

PRE 14A 1 atos20210330pre14a.htm FORM PRE 14A UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 SCHEDULE 14A PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES EXCHANGE ACT OF 1934 Filed by the Registrant ☑ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☑ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted

List of Subsidiaries

Exhibit 22.1 LIST OF SUBSIDIARIES Atossa Genetics UK Ltd. Atossa Genetics AUS Pty Ltd.

Atossa Therapeutics Announces Year End 2020 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces Year End 2020 Financial Results and Provides Corporate Update SEATTLE, March 31, 2021 (GLOBE NEWSWIRE) - Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical-stage biopharmaceutical company seeking to discover and develop innovative medicines in oncology and infectious disease with a current focus on breast cancer and COVID-19, today announced financial r

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K (Mark one) ? Annual Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the fiscal year ended December 31, 2020 OR ? Transition Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 For the transition period from: to Commission File Number 001-35

As filed with the Securities and Exchange Commission on March 31, 2021

As filed with the Securities and Exchange Commission on March 31, 2021 Registration No.

2020 Stock Incentive Plan, as amended

Exhibit 99.1 ATOSSA THERAPEUTICS, INC. 2020 STOCK INCENTIVE PLAN (Amended effective as of March 29, 2021) SECTION 1.GENERAL PURPOSE OF THE PLAN; DEFINITIONS The name of the plan is the Atossa Therapeutics, Inc. 2020 Stock Incentive Plan (the ?Plan?). The purpose of the Plan is to encourage and enable the officers, employees, Non-Employee Directors and other key persons (including Consultants and p

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): March 31, 2021 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commissio

Form of Warrant

Exhibit 4.1 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE ?SECURITIES ACT?), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

Current Report on Form 8-K, as Exhibit 1.1

Exhibit 1.1 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this ?Agreement?) is dated as of March 22, 2021, between Atossa Therapeutics, Inc., a Delaware corporation (the ?Company?), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a ?Purchaser? and collectively the ?Purchasers?). WHEREAS, subject to the terms and condition

17,361,100 Shares of Common Stock

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-248555 PROSPECTUS SUPPLEMENT (To Prospectus dated September 10, 2020) 17,361,100 Shares of Common Stock We are offering 17,361,100 shares (the “shares”) of our common stock, par value $0.18 per share (the “common stock”) pursuant to this prospectus supplement and the accompanying prospectus. In a concurrent private placement,

Placement Agency Agreement between Atossa Therapeutics, Inc. and Maxim Group LLC, dated March 22, 2021.

Exhibit 1.2 March 22, 2021 Mr. Steven C. Quay Chief Executive Officer Atossa Therapeutics, Inc. 107 Spring Street Seattle, WA 98104 Dear Mr. Quay: This letter (the ?Agreement?) constitutes the agreement between Maxim Group LLC, a limited liability company formed under the laws of the State of New York (?Maxim? or the ?Placement Agent?) and Atossa Therapeutics, Inc., a company incorporated under th

Entry into a Material Definitive Agreement, Financial Statements and Exhibits

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of report (Date of earliest event reported): March 23, 2021 (March 22, 2021) ATOSSA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorpor

Form of Lock-up and Voting Agreement dated March 22, 2021

Exhibit 1.3 LOCK-UP AND VOTING AGREEMENT This Lock-Up and Voting Agreement (this ?Lock-Up and Voting Agreement?) is being delivered to you in connection with that certain Share Purchase Agreement (the ?SPA?) by and between Atossa Therapeutics, Inc., a Delaware corporation (the ?Company?), and the person(s) or entity(ies) named on the signature pages hereto (collectively, the ?Holder?). Reference i

- FORM S-3MEF

As filed with the Securities and Exchange Commission on March 22, 2021 Registration Statement No.

Termination of a Material Definitive Agreement

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of report (Date of earliest event reported): March 22, 2021 (March 22, 2021) ATOSSA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorpor

ATOSSA THERAPEUTICS, INC. 10,500,000 Shares Common Stock

Table of Contents Filed Pursuant to Rule 424(b)(2) File No. 333-252335 PROSPECTUS ATOSSA THERAPEUTICS, INC. 10,500,000 Shares Common Stock This prospectus covers the sale of an aggregate of 10,500,000 shares (the “shares”) of our common stock, $0.18 par value per share (the “common stock”), by the selling stockholders identified in this prospectus (collectively with any of the holder’s transferees

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United States securities and exchange commission logo January 28, 2021 Kyle Guse Chief Financial Officer and General Counsel ATOSSA THERAPEUTICS, INC.

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VIA EDGAR January 28, 2021 United States Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F Street, N.

LETTER

United States securities and exchange commission logo January 28, 2021 Kyle Guse Chief Financial Officer and General Counsel ATOSSA THERAPEUTICS, INC.

- FORM S-3

Table of Contents As filed with the Securities and Exchange Commission on January 22, 2021 Registration Statement No.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* Atossa Therapeutics, Inc. (Name of Issuer) Common Stock, $0.18 par value per share (Title of Class of Sec

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* Atossa Therapeutics, Inc. (Name of Issuer) Common Stock, $0.18 par value per share (Title of Class of Securities) 04962H506 (CUSIP Number) January 6, 2020 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the r

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO § 240.13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO § 240.13d-2. (Amendment No. ___)* At

CUSIP No: 04962H506 SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO § 240.13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO § 240.13d-2. (Amendment No. )* Atossa Therapeutics, Inc. (Name of Issuer) Common Stock, $0.18 par value per share (Title of Class of Securities) 04962H506 (CUSIP Numb

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO § 240.13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO § 240.13d-2. (Amendment No. 1)* Atos

CUSIP No: 04962H506 SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO § 240.13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO § 240.13d-2. (Amendment No. 1)* Atossa Therapeutics, Inc. (Name of Issuer) Common Stock, $0.18 par value per share (Title of Class of Securities) 04962H506 (CUSIP Num

Atossa Therapeutics, Inc.

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* Atossa Therapeutics, Inc. (Name of Issuer) Common Stock, par value $0.18 (Title of Class of Securities) 04962H506 (CUSIP Number) January 6, 2021 (Date of event which requires filing of this statement) Check the appropriate box to designate the rule pursuant to which th

Units consisting of an Aggregate of 23,850,000 Shares of Common Stock and Warrants Convertible Into 17,887,500 Shares of Common Stock (and the Shares of Common Stock Underlying the Warrants)

Table of Contents Filed Pursuant to Rule 424(b)(3) Registration No. 333-248555 PROSPECTUS SUPPLEMENT (To Prospectus dated September 10, 2020) Units consisting of an Aggregate of 23,850,000 Shares of Common Stock and Warrants Convertible Into 17,887,500 Shares of Common Stock (and the Shares of Common Stock Underlying the Warrants) We are offering units consisting of an aggregate of 23,850,000 shar

Placement Agency Agreement between Atossa Therapeutics, Inc. and Maxim Group LLC, dated January 6, 2021

Exhibit 1.2 January 6, 2021 Mr. Steven C. Quay Chief Executive Officer Atossa Therapeutics, Inc. 107 Spring Street Seattle, WA 98104 Dear Mr. Quay: This letter (the “Agreement”) constitutes the agreement between Maxim Group LLC, a limited liability company formed under the laws of the State of New York (“Maxim” or the “Placement Agent”) and Atossa Therapeutics, Inc., a company incorporated under t

Entry into a Material Definitive Agreement, Financial Statements and Exhibits - FORM 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of report (Date of earliest event reported): January 8, 2021 (January 6, 2021) ATOSSA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorp

Form of Warrant

Exhibit 4.1 FORM OF COMMON STOCK PURCHASE WARRANT ATOSSA THERAPEUTICS, INC. Warrant Shares: [] Initial Exercise Date: [], 2021 THIS COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the date hereof (th

Securities Purchase Agreement dated January 6, 2021

Exhibit 1.1 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of January 6, 2021, between Atossa Therapeutics, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and conditio

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* Atossa Therapeutics, Inc. (Name of Issuer) Common Stock, $0.18 par value per share (Title of Class of Sec

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G Under the Securities Exchange Act of 1934 (Amendment No. )* Atossa Therapeutics, Inc. (Name of Issuer) Common Stock, $0.18 par value per share (Title of Class of Securities) 04962H506 (CUSIP Number) December 17, 2020 (Date of Event Which Requires Filing of this Statement) Check the appropriate box to designate the

Current Report on Form 8-K, as Exhibit 4.1

Exhibit 4.1 NEITHER THIS SECURITY NOR THE SECURITIES FOR WHICH THIS SECURITY IS EXERCISABLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTR

Entry into a Material Definitive Agreement, Financial Statements and Exhibits - FORM 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of report (Date of earliest event reported): December 21, 2020 (December 17, 2020) ATOSSA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of in

14,000,000 Shares of Common Stock

Table of Contents Filed Pursuant to Rule 424(b)(5) Registration No. 333-248555 PROSPECTUS SUPPLEMENT (To Prospectus dated September 10, 2020) 14,000,000 Shares of Common Stock We are offering 14,000,000 shares (the “shares”) of our common stock, par value $0.18 per share (the “common stock”) pursuant to this prospectus supplement and the accompanying prospectus. In a concurrent private placement,

Securities Purchase Agreement dated December 17, 2020

Exhibit 1.1 SECURITIES PURCHASE AGREEMENT This Securities Purchase Agreement (this “Agreement”) is dated as of December 17, 2020, between Atossa Therapeutics, Inc., a Delaware corporation (the “Company”), and each purchaser identified on the signature pages hereto (each, including its successors and assigns, a “Purchaser” and collectively the “Purchasers”). WHEREAS, subject to the terms and condit

Placement Agency Agreement between Atossa Therapeutics, Inc. and Maxim Group LLC, dated December 17, 2020.

Exhibit 1.2 December 17, 2020 Mr. Steven C. Quay Chief Executive Officer Atossa Therapeutics, Inc. 107 Spring Street Seattle, WA 98104 Dear Mr. Quay: This letter (the “Agreement”) constitutes the agreement between Maxim Group LLC, a limited liability company formed under the laws of the State of New York (“Maxim” or the “Placement Agent”) and Atossa Therapeutics, Inc., a company incorporated under

SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO § 240.13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO § 240.13d-2. (Amendment No. ____)* A

CUSIP No: 04962H506 SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 13G (Rule 13d-102) INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT TO § 240.13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED PURSUANT TO § 240.13d-2. (Amendment No. )* Atossa Therapeutics, Inc. (Name of Issuer) Common Stock, $0.18 par value per share (Title of Class of Securities) 04962H506 (CUSIP Numb

Underwriting Agreement, dated as of December 8, 2020, between Atossa Therapeutics, Inc. and Maxim Group LLC

Exhibit 1.1 14,575,000 SHARES of Common Stock, 5,425 SHARES OF SERIES C CONVERTIBLE PREFERRED STOCK, AND 15,000,000 WARRANTS (EXERCISABLE for 15,000,000 shares OF COMMON STOCK) OF Atossa Therapeutics, Inc. UNDERWRITING AGREEMENT December 8, 2020 Maxim Group LLC As the Representative of the Several underwriters, if any, named in Schedule I hereto 405 Lexington Avenue, 2nd Floor New York, New York 1

Financial Statements and Exhibits - FORM 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Date of report (Date of earliest event reported): December 14, 2020 (December 8, 2020) ATOSSA THERAPEUTICS, INC. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of inc

Form of Warrant

Exhibit 4.1 FORM OF COMMON STOCK PURCHASE WARRANT ATOSSA THERAPEUTICS, INC. Warrant Shares: [] Initial Exercise Date: [], 2020 THIS COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the date hereof (th

Certificate of Designation of Preferences, Rights and Limitations of Series C Convertible Preferred Stock

Exhibit 3.1 ATOSSA THERAPEUTICS, INC. CERTIFICATE OF DESIGNATION OF PREFERENCES, RIGHTS AND LIMITATIONS OF SERIES C CONVERTIBLE PREFERRED STOCK PURSUANT TO SECTION 151 OF THE DELAWARE GENERAL CORPORATION LAW The undersigned, Steven C. Quay and Kyle Guse, do hereby certify that: 1. They are the President and Secretary, respectively, of Atossa Therapeutics, Inc., a Delaware corporation (the “Corpora

Units Consisting of an Aggregate of 14,575,000 Shares of Common Stock 5,425 Shares of Series C Convertible Preferred Stock and Warrants Convertible Into Up to 15,000,000 Shares of Common Stock (and the Shares of Common Stock Underlying the Preferred

Table of Contents Filed Pursuant to Rule 424(b)(3) Registration Statement No. 333-250820 Units Consisting of an Aggregate of 14,575,000 Shares of Common Stock 5,425 Shares of Series C Convertible Preferred Stock and Warrants Convertible Into Up to 15,000,000 Shares of Common Stock (and the Shares of Common Stock Underlying the Preferred Stock and Warrants) Units consisting of an aggregate of 14,57

Form of Series C Convertible Preferred Stock

Exhibit 3.1 FORM OF ATOSSA THERAPEUTICS, INC. CERTIFICATE OF DESIGNATION OF PREFERENCES, RIGHTS AND LIMITATIONS OF SERIES C CONVERTIBLE PREFERRED STOCK PURSUANT TO SECTION 151 OF THE DELAWARE GENERAL CORPORATION LAW The undersigned, Steven C. Quay and Kyle Guse, do hereby certify that: 1. They are the President and Secretary, respectively, of Atossa Therapeutics, Inc., a Delaware corporation (the

Financial Statements and Exhibits - FORM 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): December 8, 2020 (December 8, 2020) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of inco

Form of Common Stock Purchase Warrant

Exhibit 4.1 FORM OF COMMON STOCK PURCHASE WARRANT ATOSSA THERAPEUTICS, INC. Warrant Shares: [] Initial Exercise Date: [], 2020 THIS COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the date hereof (th

Form of Warrant Agency Agreement

Exhibit 4.2 ATOSSA THERAPEUTICS, INC. and VSTOCK TRANSFER, LLC, as Warrant Agent Form of Warrant Agency Agreement Dated as of , 2020 FORM OF WARRANT AGENCY AGREEMENT WARRANT AGENCY AGREEMENT, dated as of , 2020 (“Agreement”), between Atossa Therapeutics, Inc., a corporation organized under the laws of the State of Delaware (the “Company”), and VStock Transfer, LLC., a limited lability company orga

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VIA EDGAR December 7, 2020 United States Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F Street, N.

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VIA EDGAR December 7, 2020 United States Securities and Exchange Commission Division of Corporation Finance Office of Life Sciences 100 F Street, N.

Form of Certificate of Designations of Preference, Rights and Limitations of Series C Convertible Preferred Stock

Exhibit 3.8 FORM OF ATOSSA THERAPEUTICS, INC. CERTIFICATE OF DESIGNATION OF PREFERENCES, RIGHTS AND LIMITATIONS OF SERIES C CONVERTIBLE PREFERRED STOCK PURSUANT TO SECTION 151 OF THE DELAWARE GENERAL CORPORATION LAW The undersigned, Steven C. Quay and Kyle Guse, do hereby certify that: 1. They are the President and Secretary, respectively, of Atossa Therapeutics, Inc., a Delaware corporation (the

Form of 2020 Warrant Agency Agreement

Exhibit 4.10 ATOSSA THERAPEUTICS, INC. and VSTOCK TRANSFER, LLC, as Warrant Agent Form of Warrant Agency Agreement Dated as of , 2020 FORM OF WARRANT AGENCY AGREEMENT WARRANT AGENCY AGREEMENT, dated as of , 2020 (“Agreement”), between Atossa Therapeutics, Inc., a corporation organized under the laws of the State of Delaware (the “Company”), and VStock Transfer, LLC., a limited lability company org

Form of Underwriting Agreement

Exhibit 1.1 [ ] SHARES of Common Stock, [ ] SHARES OF SERIES C CONVERTIBLE PREFERRED STOCK, AND [ ] WARRANTS (EXERCISABLE for [ ] shares OF COMMON STOCK) OF Atossa Therapeutics, Inc. UNDERWRITING AGREEMENT December [ ], 2020 Maxim Group LLC As the Representative of the Several underwriters, if any, named in Schedule I hereto 405 Lexington Avenue, 2nd Floor New York, New York 10174 Ladies and Gentl

- FORM S-1/A

Table of Contents As filed with the Securities and Exchange Commission on December 1, 2020 Registration No.

Form of 2020 Warrant

Exhibit 4.9 FORM OF COMMON STOCK PURCHASE WARRANT ATOSSA THERAPEUTICS, INC. Warrant Shares: [] Initial Exercise Date: [], 2020 THIS COMMON STOCK PURCHASE WARRANT (the “Warrant”) certifies that, for value received, or its assigns (the “Holder”) is entitled, upon the terms and subject to the limitations on exercise and the conditions hereinafter set forth, at any time on or after the date hereof (th

- FORM 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): November 26, 2020 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commis

LETTER

United States securities and exchange commission logo November 27, 2020 Steven C. Quay Chairman, Chief Executive Officer and President Atossa Therapeutics, Inc. 107 Spring Street Seattle, WA 98104 Re: Atossa Therapeutics, Inc. Registration Statement on Form S-1 Filed November 20, 2020 File No. 333-250820 Dear Mr. Quay: This is to advise you that we have not reviewed and will not review your regist

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United States securities and exchange commission logo November 27, 2020 Steven C. Quay Chairman, Chief Executive Officer and President Atossa Therapeutics, Inc. 107 Spring Street Seattle, WA 98104 Re: Atossa Therapeutics, Inc. Registration Statement on Form S-1 Filed November 20, 2020 File No. 333-250820 Dear Mr. Quay: This is to advise you that we have not reviewed and will not review your regist

Registration Statement - FORM S-1

Table of Contents As filed with the Securities and Exchange Commission on November 20, 2020 Registration No.

Financial Statements and Exhibits, Results of Operations and Financial Condition

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): November 13, 2020 Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of incorporation) (Commis

Atossa Therapeutics Announces Third Quarter 2020 Financial Results and Provides Corporate Update

Exhibit 99.1 Atossa Therapeutics Announces Third Quarter 2020 Financial Results and Provides Corporate Update SEATTLE, November 13, 2020 (GLOBE NEWSWIRE) - Atossa Therapeutics, Inc. (Nasdaq: ATOS), a clinical-stage biopharmaceutical company seeking to discover and develop innovative medicines in areas of significant unmet medical need with a current focus on breast cancer and COVID-19, today annou

Quarterly Report - FORM 10-Q

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended September 30, 2020 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission file number: 001-35610 ATOSSA THERAPEUTICS, INC.

ATOSSA THERAPEUTICS, INC. Up to $10,000,000 Common Stock

Filed Pursuant to Rule 424(b)(3) Registration No. 333-248555 PROSPECTUS SUPPLEMENT (To Prospectus dated September 10, 2020) ATOSSA THERAPEUTICS, INC. Up to $10,000,000 Common Stock We have entered into an Equity Distribution Agreement, dated September 25, 2020, or the Distribution Agreement, with Maxim Group LLC, or Maxim, relating to shares of our common stock, par value $0.18 per share, offered

Financial Statements and Exhibits - FORM 8-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of Earliest Event Reported): September 25, 2020 (September 25, 2020) Atossa Therapeutics, Inc. (Exact name of registrant as specified in its charter) Delaware 001-35610 26-4753208 (State or other jurisdiction of

Equity Distribution Agreement, dated as of September 25, 2020, by and between Atossa Therapeutics, Inc. and Maxim Group LLC

Exhibit 1.1 ATOSSA THERAPEUTICS, INC. $10,000,000 COMMON STOCK EQUITY DISTRIBUTION AGREEMENT September 25, 2020 Maxim Group LLC 405 Lexington Avenue New York, New York 10174 Ladies and Gentlemen: Atossa Therapeutics, Inc., a Delaware corporation (the “Company”), confirms its agreement (this “Agreement”) with Maxim Group LLC, as follows: 1. Issuance and Sale of Shares. The Company agrees that, from