Greenwich LifeSciences, Inc.

Greenwich LifeSciences, Inc. is a clinical-stage biopharmaceutical company focused on its Phase III clinical trial, Flamingo-01, which is evaluating GLSI-100, an immunotherapy to prevent breast cancer recurrences ¹. GP2 is a 9 amino acid transmembrane peptide of the HER2/neu protein, a cell surface receptor protein that is expressed in a variety of common cancers, including expression in 75% of breast cancers at low (1+), intermediate (2+), and high (3+ or over-expressor) levels ². The combination of GP2 + GM-CSF is called GLSI-100 ³. The company is currently expanding Flamingo-01 into Europe with plans to open up to 150 sites globally ⁴. Flamingo-01 is designed to evaluate the safety and efficacy of GLSI-100 in HER2/neu positive patients with residual disease or high-risk pathologic complete response at surgery and who have completed both neoadjuvant and postoperative adjuvant trastuzumab based treatment ⁵.

The company does not own or operate manufacturing facilities for the production of its product candidate nor does it have plans to develop its own manufacturing operations in the foreseeable future, currently depending on third-party contract manufacturers for all required raw materials, active pharmaceutical ingredients, and finished product candidate for clinical trials and potential commercial supply ⁶. In April 2009, the company entered into an exclusive license agreement with The Henry M. Jackson Foundation (HJF) pursuant to which HJF granted the company exclusive worldwide rights to several U.S. and foreign patents and patent applications covering methods of using GP2 as an immunotherapy that elicits a targeted immune response against HER2/neu-expressing cancers ⁷. In consideration for such licensed rights, the company issued HJF 202,619 shares of its common stock ⁸. The company is required to pay an annual maintenance fee and milestone payments of up to an aggregate of $5.7 million, and is also required to make 2.5-5% royalty payments based on the sales of GP2 and to reimburse HJF for patent expenses ⁹.

The company has no products approved by regulatory authorities and has not generated any revenues from collaboration and licensing agreements or product sales to date ¹⁰. For the years ended December 31, 2025 and 2024, the company reported a net loss of $19.4 million and $17.4 million, respectively ¹¹. As of December 31, 2025, the company had an accumulated deficit of $87.1 million ¹². The company does not expect to generate revenues for many years, if at all ¹³. As of May 26, 2026, the company had 4 full-time employees and 9 part-time employees ¹⁴.

In the Phase IIb and 3 Phase I clinical trials where 146 patients received GP2 immunotherapy, there were no serious adverse events observed related to the immunotherapy or any other GP2 combination treatments ¹⁵. In the Phase IIb clinical trial, 89 patients were treated with GP2 + GM-CSF and 91 placebo patients were treated with GM-CSF alone ¹⁶. After 5 years of follow-up in the Phase IIb trial, there was a substantial reduction in cancer recurrences in the HER2/neu 3+ patients who were treated with GLSI-100, followed, and remained disease free over the first 6 months ¹⁷. The GP2 issued patents provide protection ranging from 2026 through 2032 in major markets such as the U.S., Europe, Japan, Australia, and Canada ¹⁸. The company plans to register GP2 as a biologic, which may be subject to 10-12 years market exclusivity in the U.S. upon receiving marketing approval ¹⁹.

The company is developing follow-on indications for GP2 by designing and planning additional clinical trials to expand the breast cancer patient population and to pursue additional HER2/neu-expressing cancers ²⁰. Pending the receipt of sufficient capital, the Phase III clinical trial can be supplemented with additional clinical trials designed to evaluate the safety and efficacy of GLSI-100 in other patient populations ²¹. The American Cancer Society estimates that approximately 1 in 8 U.S. women (12.8%) will develop invasive breast cancer over her lifetime ²². The American Cancer Society, Economic Impact, & European Cancer Information System 2025 estimate approximately 700,000 new breast cancer patients per year and 9.5 million current breast cancer survivors in the U.S. and Europe in 2025 ²³. An estimated 42,000 female breast cancer deaths will occur in the U.S. in 2025 ²⁴.

The company has commenced Flamingo-01, a Phase III clinical trial with Baylor College of Medicine as the global primary investigator site, which includes an interim analysis and uses a similar treatment regime as the Phase IIb clinical trial ²⁵. The primary objective of Flamingo-01 is to assess the safety and efficacy of GLSI-100 compared to placebo in HLA-A*02 positive and HER2/neu positive breast cancer patients who have a high risk of disease recurrence and have completed both neoadjuvant and postoperative adjuvant trastuzumab-based standard of care therapy ²⁶. The company is currently expanding Flamingo-01 into Europe with plans to open up to 150 sites globally ²⁷.

The total cost to complete an interim analysis and file a BLA application for drug approval in the U.S. could exceed $30 million; however, the company believes that it has budget flexibility with respect to the design of the Phase III clinical trial ²⁸. The company believes that it may be able to alter the cost of its Phase III clinical trial by adjusting the enrollment rate, the number of patients, and/or the number of immunological assays ²⁹. The company is considering various options to fund the Phase III clinical trial including financing and/or strategic transactions ³⁰. A long term global and regional licensing process has been initiated and will continue as the Phase III trial commences ³¹.

The company expects to continue to incur significant expenses and operating losses for the foreseeable future, and anticipates these losses to increase as it continues to research, develop and seek regulatory approvals for its product candidate and any additional product candidates it may acquire, and potentially begin to commercialize product candidates that may achieve regulatory approval ³². The company may also encounter unforeseen expenses, difficulties, complications, delays and other unknown factors that may adversely affect its business ³³. The size of its future net losses will depend, in part, on the rate of future growth of its expenses and its ability to generate revenues ³⁴.

The company expects to expend substantial resources for the foreseeable future to continue the clinical development and manufacturing of its product candidate and the advancement and expansion of its preclinical research pipeline ³⁵. These expenditures will include costs associated with research and development, potentially acquiring new product candidates or technologies, conducting preclinical studies and clinical trials and potentially obtaining regulatory approvals and manufacturing products, as well as marketing and selling products approved for sale, if any ³⁶. The company's budgets and future capital requirements depend on many factors, including the scope, progress, results and costs of its ongoing and planned development programs for its product candidate, as well as any additional clinical trials it undertakes to obtain data sufficient to seek marketing approval for its product candidate ³⁷.

The company may seek additional capital through a variety of means, including through private and public equity offerings and debt financings, collaborations, strategic alliances and marketing, distribution or licensing arrangements ³⁸. To the extent that the company raises additional capital through the sale of equity or convertible debt securities, or through the issuance of shares under management or other types of contracts, or upon the exercise or conversion of outstanding derivative securities, the ownership interests of its stockholders will be diluted ³⁹. If the company raises additional funds through collaborations, strategic alliances, or marketing, distribution or licensing arrangements with third parties, it may have to relinquish valuable rights to its technologies, future revenue streams, product or product candidate or grant licenses on terms that may not be favorable to it ⁴⁰.

The company's future commercial strategy, if its GP2 immunotherapy or any future product candidates are approved, may include the use of strategic partners, distributors, a contract sales force, or the establishment of its own commercial and specialty sales force for the U.S. market, as well as similar strategies for regions and territories outside the U.S. ⁴¹. The company plans to further evaluate these options as it approaches submission of a new drug application or biologics license application for one of its product candidates for one or more indications ⁴². During the period of exclusivity, the company intends to advance GP2 into a Phase III clinical trial in the U.S. and pursue a European and global clinical trial strategy to support GP2 registration outside of the U.S. ⁴³.

The company's strategy during such time also includes building a commercialization team, pursuing additional funding, and pursuing strategic collaborations to support the future global marketing and sales of GP2, if approved ⁴⁴. Pending the receipt of sufficient capital, the Phase III clinical trial can be supplemented with additional clinical trials designed to evaluate the safety and efficacy of GLSI-100 in patients immediately upon diagnosis in parallel to neoadjuvant treatment and surgery, other HLA patients in the same HER2/neu 3+ breast cancer patient population, breast cancer patients who are low to intermediate expressors of HER2/neu (1-2+), or other HER2/neu-expressing cancers including, but not limited to, ovarian, gastrointestinal, and colon cancers ⁴⁵.

The company faces substantial risks including that it has incurred substantial losses since its inception and anticipates continuing to incur substantial and increasing losses for the foreseeable future, with a net loss of $19.4 million for the year ended December 31, 2025 and an accumulated deficit of $87.1 million as of December 31, 2025 ⁴⁶. The company needs significant additional financing to fund its operations and complete the development and, if approved, the commercialization of its product candidate, and if unable to raise capital when needed, could be forced to delay, reduce or eliminate its product development programs or commercialization efforts ⁴⁷. The total cost to complete an interim analysis and file a BLA application for drug approval in the U.S. could exceed $30 million ⁴⁸. The company's future success is dependent on the regulatory approval of its product candidate, and clinical drug development involves a lengthy and expensive process with an uncertain outcome ⁴⁹. The company is dependent on technologies it licenses from HJF, and if it loses the right to license such technologies, its ability to develop new products would be harmed ⁵⁰. The company relies on third parties to conduct its preclinical studies and clinical trials, and if these third parties do not successfully carry out their contractual duties or meet expected deadlines, the company may not be able to obtain regulatory approval for or commercialize its current or future product candidates on a timely basis, if at all ⁵¹. The company faces substantial competition, which may result in others discovering, developing or commercializing products before or more successfully than it does ⁵².

The tone of management's message to shareholders is focused on the substantial risks and uncertainties inherent in the company's forward-looking statements, which are based on a series of expectations, assumptions, estimates and projections about the company and are not guarantees of future results or performance ⁵³. Management emphasizes that the company may not actually achieve the plans, intentions or expectations disclosed in these forward-looking statements and that actual results or events could differ materially ⁵⁴. The strategic priorities emphasized include the successful completion of the Phase III Flamingo-01 clinical trial, the need to raise substantial additional capital to fund operations, and the dependence on obtaining necessary regulatory approvals to market and commercialize the product candidate ⁵⁵. Management specifically highlights the projected financial position and estimated cash burn rate, the success, cost and timing of clinical trials, and the ability to obtain and maintain intellectual property protection as key forward-looking considerations ⁵⁶.