Advent Technologies Holdings, Inc. (ADN)

Advent Technologies Holdings, Inc. was an advanced materials and fuel cell technology company headquartered in Boston, Massachusetts. Its operating company, Advent Technologies, Inc., was founded in 2006 and developed high-temperature proton exchange membrane (HT-PEM) fuel cell technology, which can use fuels such as methanol or hydrogen and tolerate higher operating temperatures than conventional low-temperature cells.

The company made membrane electrode assemblies, fuel cell stacks and systems for stationary and portable power. Target applications included backup power, aviation, automotive and defense uses. It also offered materials for sensors and other electronic uses, and it operated research and manufacturing sites in the United States and Greece.

Advent became public through a business combination with AMCI Acquisition Corp., a special purpose acquisition company, completed in February 2021. After the merger, the combined company traded on Nasdaq under the symbol ADN, with warrants quoted as ADNWW. It acquired UltraCell, a U.S. maker of fuel cell systems for defense customers, in 2021 and pursued European and U.S. growth plans.

Like other early-stage fuel cell companies, Advent recorded losses and needed outside capital to fund operations. Its revenue was modest relative to its costs, and its share price fell substantially after the SPAC transaction. Those financial conditions led to difficulties meeting Nasdaq's continued listing standards.

On August 18, 2025, Nasdaq staff notified the company that it no longer satisfied Listing Rules 5550(b)(1), 5550(b)(2) and 5550(b)(3), which relate to stockholders' equity, market value of listed securities and net income. Advent appealed to the Listing Qualifications Hearings Panel, which held a hearing on October 7, 2025. On October 28, 2025, the panel issued a decision to suspend the company from Nasdaq.

The securities were suspended on October 30, 2025, so October 29, 2025 was the last day of regular Nasdaq trading. The staff delisting determination became final on December 12, 2025, and was published on January 13, 2026. Removal from listing took effect at the opening of trading on February 2, 2026, with the stock having moved to over-the-counter quotation under the symbol ADNH.

The delisting was not connected to an acquisition, so shareholders received no consideration from a buyer. The sequence of events illustrates how the Nasdaq process works for companies that fall short of multiple continued listing standards: a staff determination, an appeal to a hearings panel, a suspension from trading, and then a formal Form 25 delisting. After suspension the common stock moved to over-the-counter quotation as ADNH, where liquidity and disclosure standards differ from those of a national exchange.