Cemiplimab-RWLC

Milestone follows FDA clearance of MAIA’s amended investigational new drug (IND) submission highlighting improved manufacturing capabilities and efficiencies U.S. expansion is funded by a $2.3 million NIH grant to MAIA to support third-line treatment evaluation CHICAGO, Sept. 16, 2026 (GLOBE NEWSWIRE) -- MAIA Biotechnology, Inc. (NYSE American: MAIA) (“MAIA”, the “Company”), a clinical-stage biopharmaceutical company focused on developing targeted immunotherapies for cancer, today announced that the first U.S. patient has been dosed in its Phase 2 THIO-101 trial expansion evaluating its telomere-targeting lead candidate, ateganosine, in third-line non-small cell lung cancer (NSCLC). The U.S. Phase 2 expansion is funded by a $2.3 million grant from the National Institutes of Health (NIH) to support third-line treatment evaluation and MAIA has activated 3 sites in the U.S. MAIA holds FDA Fast Track designation for ateganosine, a dual mechanism therapy designed to break down telomere structure and function in cancer cells while inducing immune activation. Prior data from THIO-101 Parts A and B show overall survival (OS) beyond 24 months in eight patients receiving ateganosine sequenced with a checkpoint inhibitor. “We have worked diligently to advance ateganosine into the U.S. market, and dosing the first patient in the United States represents a major milestone for our ongoing Phase 2 clinical trial,” said Vlad Vitoc, M.D., Founder and Chief Executive Officer of MAIA. “Our collaborations with some of the nation’s top institutions and foremost oncologists further strengthen the trial as we evaluate ateganosine for patients in advanced stages of this exceedingly hard-to-treat disease. We believe the data generated through the THIO-101 program may also support a potential pathway toward FDA accelerated approval. With patients now enrolled across four continents, the study has evolved into a truly global effort focused on addressing a critical unmet need in cancer care.” About Ateganosine Ateganosine (THIO, 6-thio-dG or 6-thio-2’-deoxyguanosine) is a first-in-class investigational telomere-targeting agent currently in clinical development to evaluate its activity in non-small cell lung cancer (NSCLC). Telomeres, along with the enzyme telomerase, play a fundamental role in the survival of cancer cells and their resistance to current therapies. The modified nucleotide 6-thio-2’-deoxyguanosine induces telomerase-dependent telomeric DNA modification, DNA damage responses, and selective cancer cell death. Ateganosine-damaged telomeric fragments accumulate in cytosolic micronuclei and activates both innate (cGAS/STING) and adaptive (T-cell) immune responses. The sequential treatment of ateganosine followed by PD-(L)1 inhibitors resulted in profound and persistent tumor regression in advanced, in vivo cancer models by induction of cancer type–specific immune memory. Ateganosine is presently developed as a second or later line of treatment for NSCLC for patients that have progressed beyond the standard-of-care regimen of existing checkpoint inhibitors. About THIO-101 Phase 2 Clinical Trial THIO-101 is a multicenter, open-label, dose finding Phase 2 clinical trial. It is the first trial designed to evaluate ateganosine’s anti-tumor activity when followed by PD-(L)1 inhibition. The trial is testing the hypothesis that low doses of ateganosine administered prior to cemiplimab (Libtayo ® ) will enhance and prolong immune response in patients with advanced NSCLC who previously did not respond or developed resistance and progressed after first-line treatment regimen containing another checkpoint inhibitor. The trial design has two primary objectives: (1) to evaluate the safety and tolerability of ateganosine administered as an anticancer compound and a priming immune activator (2) to assess the clinical efficacy of ateganosine using Overall Response Rate (ORR) as the primary clinical endpoint. The expansion of the study will assess overall response rates (ORR) in advanced NSCLC patients receiving third line (3L) therapy who were resistant to previous checkpoint inhibitor treatments (CPI) and chemotherapy. Treatment with ateganosine followed by cemiplimab (Libtayo ® ) has shown an acceptable safety pro date in a heavily pre-treated population. For more information on this Phase II trial, please visit ClinicalTrials.gov using the identifier NCT05208944. About MAIA Biotechnology, Inc. MAIA is a targeted therapy, immuno-oncology company focused on the development and commercialization of potential first-in-class drugs with novel mechanisms of action that are intended to meaningfully improve and extend the lives of people with cancer. Our lead program is ateganosine (THIO), a potential first-in-class cancer telomere targeting agent in clinical development for the treatment of NSCLC patients with telomerase-positive cancer cells. For more information, please visit . Forward Looking Statements MAIA cautions that all statements, other than statements of historical facts contained in this press release, are forward-looking statements. Forward-looking statements are subject to known and unknown risks, uncertainties, and other factors that may cause our or our industry’s actual results, levels or activity, performance or achievements to be materially different from those anticipated by such statements. The use of words such as “may,” “might,” “will,” “should,” “could,” “expect,” “plan,” “anticipate,” “believe,” “estimate,” “project,” “intend,” “future,” “potential,” or “continue,” and other similar expressions are intended to identify forward looking statements. However, the absence of these words does not mean that statements are not forward-looking. For example, all statements we make regarding (i) the initiation, timing, cost, progress and results of our preclinical and clinical studies and our research and development programs, (ii) our ability to advance product candidates into, and successfully complete, clinical studies, (iii) the timing or likelihood of regulatory filings and approvals, (iv) our ability to develop, manufacture and commercialize our product candidates and to improve the manufacturing process, (v) the rate and degree of market acceptance of our product candidates, (vi) the size and growth potential of the markets for our product candidates and our ability to serve those markets, and (vii) our expectations regarding our ability to obtain and maintain intellectual property protection for our product candidates, are forward looking. All forward-looking statements are based on current estimates, assumptions and expectations by our management that, although we believe to be reasonable, are inherently uncertain. Any forward-looking statement expressing an expectation or belief as to future events is expressed in good faith and believed to be reasonable at the time such forward-looking statement is made. However, these statements are not guarantees of future events and are subject to risks and uncertainties and other factors beyond our control that may cause actual results to differ materially from those expressed in any forward-looking statement. Any forward-looking statement speaks only as of the date on which it was made. We undertake no obligation to publicly update or revise any forward-looking statement, whether as a result of new information, future events or otherwise, except as required by law. In this release, unless the context requires otherwise, “MAIA,” “Company,” “we,” “our,” and “us” refers to MAIA Biotechnology, Inc. and its subsidiaries. Investor Relations Contact +1 (872) 270-3518 ir@maiabiotech.com

CHICAGO, Sept. 15, 2026 (GLOBE NEWSWIRE) -- MAIA Biotechnology, Inc. (NYSE American: MAIA) (“MAIA”, the “Company”), a clinical-stage biopharmaceutical company focused on developing immunotherapies for cancer, today announced that Board member Ramiro Guerrero, JD, LL.M. has increased his ownership stake in the Company through open market purchases totaling approximately $252,284. A total of 185,078 shares of MAIA common stock were acquired by Mr. Guerrero between August 20, 2026, and September 10, 2026, at an average common stock price of $1.36. MAIA also announced that 73,000 shares of MAIA common stock were acquired by Founder and CEO Vlad Vitoc, M.D. on September 14, 2026, at an average common stock price of $1.37. “Our increased investments reflect the confidence we share across our leadership team in MAIA’s science, clinical strategy and long-term commercial potential,” said Dr. Vitoc. “With a growing body of clinical evidence supporting the ateganosine program, we believe MAIA is entering an increasingly important period in its development.” “As MAIA has stated previously, its ongoing pivotal Phase 3 trial offers a statistically high probability of technical success,” Mr. Guerrero added. “I continue to believe MAIA is well positioned to create a great deal of value for its shareholders over time.” MAIA’s ongoing pivotal Phase 3 trial THIO-104 evaluates ateganosine sequenced with checkpoint inhibitor cemiplimab versus investigator’s choice in third-line non-small cell lung cancer (NSCLC). Statistical assessments of ateganosine suggest a high probability of technical success and potential early full commercial approval if Phase 3 interim data is consistent with Phase 2 THIO-101 trial results. MAIA recently announced positive initial efficacy data from the ongoing Phase 2 THIO-101 clinical trial expansion, Part C, with third-line studies showing a disease control rate (DCR) of 90.5% 1 in the efficacy evaluable population who had at least one tumor scan after starting treatment. As of September 14, 2026, MAIA’s directors and officers hold a 21.34% stake in the Company. About Ateganosine Ateganosine (THIO, 6-thio-dG or 6-thio-2’-deoxyguanosine) is a first-in-class investigational telomere-targeting agent currently in clinical development to evaluate its activity in non-small cell lung cancer (NSCLC). Telomeres, along with the enzyme telomerase, play a fundamental role in the survival of cancer cells and their resistance to current therapies. The modified nucleotide 6-thio-2’-deoxyguanosine induces telomerase-dependent telomeric DNA modification, DNA damage responses, and selective cancer cell death. Ateganosine-damaged telomeric fragments accumulate in cytosolic micronuclei and activates both innate (cGAS/STING) and adaptive (T-cell) immune responses. The sequential treatment of ateganosine followed by PD-(L)1 inhibitors resulted in profound and persistent tumor regression in advanced, in vivo cancer models by induction of cancer type–specific immune memory. Ateganosine is presently developed as a second or later line of treatment for NSCLC for patients that have progressed beyond the standard-of-care regimen of existing checkpoint inhibitors. About MAIA Biotechnology, Inc. MAIA is a targeted therapy, immuno-oncology company focused on the development and commercialization of potential first-in-class drugs with novel mechanisms of action that are intended to meaningfully improve and extend the lives of people with cancer. Our lead program is ateganosine (THIO), a potential first-in-class cancer telomere targeting agent in clinical development for the treatment of NSCLC patients with telomerase-positive cancer cells. For more information, please visit . Forward Looking Statements MAIA cautions that all statements, other than statements of historical facts contained in this press release, are forward-looking statements. Forward-looking statements are subject to known and unknown risks, uncertainties, and other factors that may cause our or our industry’s actual results, levels or activity, performance or achievements to be materially different from those anticipated by such statements. The use of words such as “may,” “might,” “will,” “should,” “could,” “expect,” “plan,” “anticipate,” “believe,” “estimate,” “project,” “intend,” “future,” “potential,” or “continue,” and other similar expressions are intended to identify forward looking statements. However, the absence of these words does not mean that statements are not forward-looking. For example, all statements we make regarding (i) the initiation, timing, cost, progress and results of our preclinical and clinical studies and our research and development programs, (ii) our ability to advance product candidates into, and successfully complete, clinical studies, (iii) the timing or likelihood of regulatory filings and approvals, (iv) our ability to develop, manufacture and commercialize our product candidates and to improve the manufacturing process, (v) the rate and degree of market acceptance of our product candidates, (vi) the size and growth potential of the markets for our product candidates and our ability to serve those markets, and (vii) our expectations regarding our ability to obtain and maintain intellectual property protection for our product candidates, are forward looking. All forward-looking statements are based on current estimates, assumptions and expectations by our management that, although we believe to be reasonable, are inherently uncertain. Any forward-looking statement expressing an expectation or belief as to future events is expressed in good faith and believed to be reasonable at the time such forward-looking statement is made. However, these statements are not guarantees of future events and are subject to risks and uncertainties and other factors beyond our control that may cause actual results to differ materially from those expressed in any forward-looking statement. Any forward-looking statement speaks only as of the date on which it was made. We undertake no obligation to publicly update or revise any forward-looking statement, whether as a result of new information, future events or otherwise, except as required by law. In this release, unless the context requires otherwise, “MAIA,” “Company,” “we,” “our,” and “us” refers to MAIA Biotechnology, Inc. and its subsidiaries. Investor Relations Contact +1 (872) 270-3518 ir@maiabiotech.com 1 As of July 6, 2026