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- Marked increases in overall survival observed across soft tissue sarcoma patients - - Demonstrated improvement of median progression free survival in patients with dedifferentiated liposarcoma (DDLPS) - - DDLPS expansion cohort enrolling to inform a potential Phase 3 registration trial - SAN CARLOS, Calif., June 03, 2023 (GLOBE NEWSWIRE) -- Apexigen, Inc. (Nasdaq: APGN) a clinical-stage company focused on developing innovative antibody-based therapeutics for the treatment of cancer with a focus on immuno-oncology, today announced the presentation of new data from a Phase 2 investigator-sponsored trial in collaboration with Columbia University, evaluating sotigalimab (sotiga), Apexigen’s agonist antibody targeting CD40, in combination with standard-of-care doxorubicin (dox), in patients with advanced soft tissue sarcoma (STS). These data were presented in a poster presentation on June 3, 2023 at the ASCO Annual Meeting being held both virtually and in person in Chicago, IL. Sotiga combined with dox was safe and well tolerated and indicated increases in overall survival (OS) with a median OS of 35.6 months across all STS patients evaluated, which is markedly higher than the historical OS of 12.8 to 20 months of dox alone across STS subtypes. Moreover, subtype-specific analysis demonstrated improvement in median progression-free survival (mPFS) of 10.95 months in patients with dedifferentiated liposarcoma (DDLPS) which is markedly higher than the historical mPFS of 4 months in patients with DDLPS. “We are excited to present new data at ASCO from the Phase 2 trial in patients with advanced STS that supports further development of sotiga-based combinations and underscores the significant opportunity to provide patients with meaningful clinical benefit characterized by rapid, deep and durable responses with a favorable safety profile,” said Xiaodong Yang, M.D., Ph.D., Chief Executive Officer of Apexigen. “Notably, we are encouraged by the median overall survival results across sarcoma subtypes and the data demonstrating that the subgroup of patients with DDLPS treated with sotiga in combination with dox achieved a mPFS, more than double that seen historically with dox alone. We look forward to building on these impressive findings with our DDLPS expansion cohort, which will potentially inform a Phase 3 registration study in DDLPS.” Key Takeaways: The open-label, single-arm, multicenter Phase 2 trial enrolled patients with advanced STS, including DDLPS, leiomyosarcoma (LMS), and undifferentiated pleomorphic sarcoma (UPS) and treated patients with a combination of sotiga and dox. The primary endpoint was objective response rate (ORR), and secondary endpoints were progression-free survival and safety. Interim results indicated marked increases in OS across STS subtypes compared to historical standard-of-care dox monotherapy with a median OS of 35.62 months (n=32), which is remarkably higher than the historical OS of 12.8 to 20 months across STS subtypes.Subtype-specific analysis demonstrated an mPFS of 10.95 months for DDLPS patients (n=9), which is remarkably higher than the historical mPFS of 4 months for standard-of-care dox in patients with DDLPS.The interim ORR observed in the trial is comparable to the ORR of single-agent doxorubicin in the STS population. Durable objective responses and stable disease have been observed beyond what might be expected from single-agent doxorubicin.Overall, sotiga combined with dox was safe and well tolerated. Grade 3/4 treatment-related adverse events (TRAEs) occurred in 56% (18/32) of patients – the most common grade 3/4 TRAEs were neutropenia (31%), febrile neutropenia (19%), and anemia (19%) and were consistent with the safety profile of doxorubicin monotherapy.3/32 (9.4%) withdrew study treatment for AEs.Cytokine release syndrome was reported in 19% of patients – all grade 1/2.There were no additive/synergistic or unexpected AEs observed with the combination. More information about the study is available here (NCT03719430). The abstract (#11565) is accessible on the ASCO Congress portal, and additional details are provided below. Title: A phase 2 trial with a safety lead-in to evaluate the addition of sotigalimab, a CD40 agonistic monoclonal antibody, to standard-of-care doxorubicin for the treatment of advanced sarcomaFormat: Poster (Bd #499)Session Title: SarcomaSession Date and Time: Saturday, June 3 from 1:15 p.m. to 4:15 p.m. CT About Apexigen Apexigen is a clinical-stage biopharmaceutical company focused on discovering and developing a new generation of antibody therapeutics for oncology, with an emphasis on new immuno-oncology agents designed to harness the patient’s immune system to combat and eradicate cancer. Sotigalimab and Apexigen’s other programs were discovered using Apexigen’s proprietary APXiMAB™ discovery platform. This platform has enabled Apexigen and its collaboration partners to discover and develop therapeutic antibodies against a variety of molecular targets, including targets that are difficult to drug with conventional antibody technologies. Multiple product candidates have been discovered using the APXiMAB platform, one of which is commercially available and the others are in clinical development, either internally by Apexigen or by its licensees. For more information, please visit www.apexigen.com. Forward-Looking Statements This press release contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, including statements regarding Apexigen’s ability to provide innovative oncology solutions, meet the needs of patients and provide meaningful clinical benefits; the potential attributes, uses and effectiveness of its lead candidate sotigalimab; and Apexigen’s beliefs with respect to the successful development of sotigalimab. Any statements contained herein that are not statements of historical fact may be deemed to be forward-looking statements. In addition, any statements that refer to projections, forecasts or other characterizations of future events or circumstances, including any underlying assumptions, are forward-looking statements. The words “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “intends,” “may,” “might,” “plan,” “possible,” “potential,” “predict,” “project,” “should,” “would” and similar expressions may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking. The forward-looking statements contained in this press release are based on certain assumptions and analyses made by Apexigen’s management in light of their respective experience and their perception of historical trends, current conditions and expected future developments and their potential effects on Apexigen, as well as other factors they believe are appropriate in the circumstances. There can be no assurance that future developments affecting Apexigen will be those that Apexigen has anticipated. These forward-looking statements involve a number of risks, uncertainties (some of which are beyond Apexigen’s control) or other assumptions that may cause actual results or performance to be materially different from those expressed or implied by these forward-looking statements, including Apexigen’s early stages of clinical drug development, Apexigen’s ability to achieve successful clinical results with sotigalimab, Apexigen’s competitors developing and marketing products that are more effective, safer, or less expensive than Apexigen’s product candidates, delays or difficulties in the enrollment of patients in Apexigen’s clinical trials, or that Apexigen will have sufficient capital to operate as anticipated. Should one or more of these risks or uncertainties materialize, or should any of our assumptions prove incorrect, actual results may vary in material respects from those projected in these forward-looking statements. Additional factors that could cause actual results to differ are discussed under the heading “Risk Factors” and in other sections of Apexigen’s filings with the SEC, and in its current and periodic reports filed or furnished from time to time with the SEC. All forward-looking statements in this press release are made as of the date hereof, based on information available to Apexigen and Apexigen assumes no obligation to update or revise any forward-looking statement, whether as a result of new information, future events or otherwise, except as may be required under applicable securities laws. Investor Contact:Bruce MackleLifeSci Advisors+1-646-889-1200bmackle@lifesciadvisors.com Apexigen Contact:William DukeChief Financial OfficerApexigen, Inc.+1-650-931-6236ir@apexigen.com

Sponsored research data presented in a poster presentation at the American Association for Cancer Research (AACR) Annual Meeting 2023 Annamycin demonstrated increased penetration and accumulation in the liver, which correlated with high antitumor activity in HEPA 1-6 hepatocellular carcinoma and CT26 colon cancer liver metastasis models Ongoing clinical trials evaluating Annamycin for the treatment of STS lung metastases (STS lung mets) and acute myeloid leukemia (AML) HOUSTON, April 18, 2023 /PRNewswire/ -- Moleculin Biotech, Inc., (Nasdaq: MBRX) ("Moleculin" or the "Company"), a clinical stage pharmaceutical company with a growing pipeline, including Phase 2 clinical programs, for hard-to-treat tumors and viruses, today announced that positive preclinical data regarding the Company's next-generation anthracycline, Annamycin, was presented at the American Association for Cancer Research (AACR) Annual Meeting 2023, taking place April 14-19, 2023, at the Orange County Convention Center in Orlando, FL. This research was sponsored by the Company. The poster titled, Exploration of Annamycin Organotropism to Target Primary and Metastatic Liver Cancers was presented by Rafal Zielinski, Ph.D., Department of Experimental Therapeutics, Division of Cancer Medicine, The University of Texas MD Anderson Cancer Center as part of the Experimental and Molecular Therapeutic Session: "Novel Antitumor Agents, PI3K/AKT Inhibitors, Proteasome Inhibitors, and Topoisomerases." The poster outlined results from the analysis of the pharmacokinetics of two formulations of Annamycin, liposome formulated drug product (L-ANN) and free Annamycin (ANN), in the liver in comparison with doxorubicin (DOX) and to determine its tumoricidal potential in a hepatocellular carcinoma (HCC) model in situ and in experimental models of liver metastasis. "Annamycin has continued to demonstrate in preclinical models promising results in hard-to-treat tumors. We are pleased with the findings from these preclinical models in HCC, the most common type of primary liver cancer that is responsible for more than 12,000 deaths per year in the US. The high antitumor activity seen preclinically with Annamycin is very encouraging and provides validation for expanded studies to assess activity in different tumor liver metastasis models as well as HCC models," commented Walter Klemp, Chairman and Chief Executive Officer of Moleculin. Annamycin is the Company's next-generation anthracycline that has been designed to be non-cardiotoxic (unlike currently prescribed anthracyclines) and has been shown in animal models to accumulate in the lungs at up to 30-fold the level of doxorubicin (a commonly prescribed anthracycline), as well as demonstrating the ability to avoid the multidrug resistance mechanisms that typically limit the efficacy of doxorubicin and other currently prescribed anthracyclines. The levels of ANN and DOX in plasma and tissue homogenates were assessed using LC/MS. The antitumor efficacy of L-ANN was studied using HEPA 1-6 hepatocellular carcinoma models (subcutaneous, orthotopic, and experimental liver metastatic models) as well as CT26 colon cancer and MIA PaCa-2 pancreatic cancer liver metastasis models. Data Highlights: ANN exhibited significantly higher accumulation in the liver parenchyma when compared to DOX (6-fold higher AUC values). Researchers observed clear inhibition of the subcutaneous tumor growth after systemic (IV) administration of L-ANN. Increased liver uptake of the drug had a direct effect on activity of the drug in vivo. Remarkable activity of L-ANN was observed in orthotopic models. Significant inhibition of the tumor growth and extension of the survival of L-ANN treated mice vs. vehicle-receiving animals was observed in HEPA 1-6 models (median survival 29.5 vs 50 days (p<0.0001) and 28 vs 59 days (p<0.0001), respectively). L-ANN treatment resulted in dramatic increase in survival (median survival >407 days) in the CT26 colon cancer experimental metastasis model. In a separate experiment, significant delay in tumor progression was also observed in pancreatic cancer (MIA PaCa-2) liver metastasis model. Annamycin is currently being evaluated in ongoing clinical trials for the treatment of STS lung metastases and AML. For more information about the ongoing trials, please visit clinicaltrials.gov and reference identifiers NCT04887298 and NCT05319587, respectively. Unless specifically noted otherwise, references to "Annamycin" refer to the liposome formulated form of the drug. About Annamycin Annamycin is the Company's next-generation anthracycline that has been shown in animal models to accumulate in the lungs at up to 30-fold the level of doxorubicin. Importantly, Annamycin has also demonstrated a lack of cardiotoxicity in multiple early-stage human clinical trials, including ongoing trials for the treatment of acute myeloid leukemia (AML) and STS lung metastases. For that reason, although additional data will be necessary, the Company believes Annamycin may not face the same usage limitations imposed on doxorubicin, one of the most common currently approved anthracyclines. Annamycin is currently in development for the treatment of AML and STS lung metastases and the Company believes the drug may have the potential to treat additional indications. About Moleculin Biotech, Inc. Moleculin Biotech, Inc. is a clinical stage pharmaceutical company with a growing pipeline, including Phase 2 clinical programs, for hard-to-treat tumors and viruses. The Company's lead program, Annamycin is a next-generation anthracycline designed to avoid multidrug resistance mechanisms with little to no cardiotoxicity. Annamycin is currently in development for the treatment of relapsed or refractory acute myeloid leukemia (AML) and soft tissue sarcoma (STS) lung metastases. Additionally, the Company is developing WP1066, an Immune/Transcription Modulator capable of inhibiting p-STAT3 and other oncogenic transcription factors while also stimulating a natural immune response, targeting brain tumors, pancreatic and other cancers, and WP1220, an analog to WP1066, for the topical treatment of cutaneous T-cell lymphoma. Moleculin is also engaged in the development of a portfolio of antimetabolites, including WP1122 for the potential treatment of COVID-19 and other viruses, as well as cancer indications including brain tumors, pancreatic and other cancers. For more information about the Company, please visit and connect on Twitter, LinkedIn and Facebook. Forward-Looking Statements Some of the statements in this release are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, Section 21E of the Securities Exchange Act of 1934 and the Private Securities Litigation Reform Act of 1995, which involve risks and uncertainties. Although Moleculin believes that the expectations reflected in such forward-looking statements are reasonable as of the date made, expectations may prove to have been materially different from the results expressed or implied by such forward-looking statements. Moleculin has attempted to identify forward-looking statements by terminology including 'believes,' 'estimates,' 'anticipates,' 'expects,' 'plans,' 'projects,' 'intends,' 'potential,' 'may,' 'could,' 'might,' 'will,' 'should,' 'approximately' or other words that convey uncertainty of future events or outcomes to identify these forward-looking statements. These statements are only predictions and involve known and unknown risks, uncertainties, and other factors, including those discussed under Item 1A. "Risk Factors" in our most recently filed Form 10-K filed with the Securities and Exchange Commission ("SEC") and updated from time to time in our Form 10-Q filings and in our other public filings with the SEC. Any forward-looking statements contained in this release speak only as of its date. We undertake no obligation to update any forward-looking statements contained in this release to reflect events or circumstances occurring after its date or to reflect the occurrence of unanticipated events. Investor Contact: JTC Team, LLC Jenene Thomas (833) 475-8247 [email protected] SOURCE Moleculin Biotech, Inc.