If You Invested in Third Harmonic Bio, Inc. (THRD)

Third Harmonic Bio, Inc. (THRD) was a clinical-stage biopharmaceutical company listed on The Nasdaq Stock Market under the ticker symbol THRD. According to its public disclosures, the company focused on advancing the next wave of medicine for dermal, respiratory, and gastrointestinal inflammatory diseases through the development of novel, highly selective, small-molecule inhibitors of KIT, a cell surface receptor that serves as the master regulator of mast cell function and survival.

Third Harmonic Bio described itself as targeting mast-cell-mediated inflammatory diseases by inhibiting KIT, a cell surface receptor that acts as a master regulator of mast cell function and survival. Early clinical studies cited by the company indicated that KIT inhibition has the potential to transform the treatment of a broad range of mast-cell-mediated inflammatory diseases. The company’s lead product candidate was THB335, a titratable, oral, small molecule inhibitor of KIT.

Over time, Third Harmonic Bio’s development focus shifted from its first-generation KIT inhibitor, THB001, to THB335. Company disclosures noted that development costs related to THB001 had been terminated, while research and development spending increased for the THB335 program. THB335 was evaluated in a Phase 1 single ascending dose (SAD) and multiple ascending dose (MAD) clinical trial in healthy volunteers, designed to assess safety and tolerability, characterize pharmacokinetics, and measure pharmacodynamic effects through reductions in serum tryptase, a biomarker associated with mast cell activation and correlated with clinical response in urticaria studies.

The Phase 1 SAD/MAD trial of THB335 included once-daily dosing cohorts and evaluated dose-dependent exposure and pharmacodynamic effects. Company reports indicated that THB335 showed a half-life of approximately 40 hours, enabling once-daily dosing, and that dose-dependent increases in exposure were observed across SAD and MAD cohorts. In MAD cohorts, trough plasma exposures exceeded the KIT IC90 at certain dose levels, and dose-dependent reductions in serum tryptase were observed, with mean reductions from baseline reaching levels the company believed could have potential clinical benefit in chronic spontaneous urticaria (CSU).

Safety data disclosed by Third Harmonic Bio from the THB335 Phase 1 trial indicated that THB335 was generally safe and well tolerated in SAD cohorts. In MAD cohorts, there were isolated, transient asymptomatic transaminase elevations, some of which occurred in placebo subjects. The company reported that, based on expert review, it did not believe a single transaminase event in an active subject was drug-related. Consistent with KIT biology, adverse events such as hair color change and reductions in hemoglobin and neutrophil counts were observed in MAD cohorts, described as largely dose-dependent and resolving during follow-up.

Third Harmonic Bio’s disclosures emphasized chronic spontaneous urticaria as a key target indication for THB335. The company conducted Phase 2 readiness activities and reported completion of clinical, toxicology, and manufacturing work to support a Phase 2 trial in CSU. It also reported plans to submit regulatory filings to seek clearance for Phase 2 initiation and described a planned 12-week, placebo-controlled Phase 2 study in CSU, although the broader corporate strategy subsequently changed.

In parallel with its clinical work, Third Harmonic Bio initiated a strategic review process to explore opportunities to maximize shareholder value, including potential strategic transactions and business combinations. The company reported halting all non-THB335 research and discovery activities and undertaking a significant reduction in workforce, while highlighting what it described as a strong cash and cash equivalents position in its financial reports.

A major change in corporate status followed. On April 10, 2025, the company’s board of directors approved a Plan of Liquidation and Dissolution, subject to stockholder approval. Third Harmonic Bio subsequently announced that its stockholders overwhelmingly approved the Plan of Dissolution at the Annual Meeting of Stockholders held on June 5, 2025. The Plan of Dissolution contemplated an orderly wind down of operations, distribution of remaining cash to stockholders, and sale of the company’s assets and intellectual property, including the THB335 program.

In connection with the Plan of Dissolution, Third Harmonic Bio announced that it would initiate a sale process for THB335 and related intellectual property. The company reported completing additional Phase 1 cohort work with a new capsule formulation of THB335 intended for future clinical development and stated that it had completed all activities needed to support a Phase 2 clinical trial in CSU, but the asset was to be sold as part of the liquidation process.

The company’s regulatory filings document its transition from an active Nasdaq-listed issuer to a dissolved entity. An 8-K filed on July 31, 2025 noted that Third Harmonic Bio filed a Certificate of Dissolution with the Secretary of State of the State of Delaware on July 31, 2025, which became effective upon filing, in accordance with the previously approved Plan of Dissolution. The same filing explained that the board fixed July 31, 2025 as the record date for stockholders entitled to receive future liquidation distributions and that the company instructed its transfer agent to close its stock transfer books and discontinue recording transfers of common stock as of the close of business on that date.

Also on July 31, 2025, Third Harmonic Bio filed a Form 25 with the SEC to effect the voluntary delisting of its common stock from The Nasdaq Stock Market under Section 12(b) of the Securities Exchange Act of 1934. The Form 25 indicated that the delisting would be effective on or about August 10, 2025, ten days after the filing. In connection with the delisting, the company requested that trading in its common stock on Nasdaq be suspended before the market opened on July 31, 2025.

On August 11, 2025, Third Harmonic Bio filed a Form 15 with the SEC, certifying and providing notice of termination of registration of its common stock under Section 12(g) of the Exchange Act and suspension of its duty to file reports under Sections 13 and 15(d). The Form 15 cited applicable Exchange Act rules and reported the approximate number of holders of record as of the certification date.

These steps mean that Third Harmonic Bio, Inc. no longer operates as a publicly reporting company and its common stock is no longer listed on Nasdaq. The company’s remaining activities, as described in its dissolution-related filings, focus on liquidation, satisfaction of liabilities, maintenance of reserves, and distribution of available assets to stockholders in accordance with Delaware law and the approved Plan of Dissolution.

Business focus before dissolution

Before adopting the Plan of Dissolution, Third Harmonic Bio’s business was centered on the discovery and development of small-molecule inhibitors of KIT for inflammatory diseases affecting the skin, respiratory tract, and gastrointestinal system. The company repeatedly described KIT as a master regulator of mast cell function and survival, and it viewed mast-cell-mediated inflammation as a key driver of the diseases it aimed to address. Its lead candidate, THB335, was characterized as a titratable, oral small molecule inhibitor of KIT, with Phase 1 data in healthy volunteers and planned development in chronic spontaneous urticaria.

Company reports emphasized that early clinical studies suggested KIT inhibition could significantly change treatment paradigms for a broad range of mast-cell-mediated inflammatory diseases. Third Harmonic Bio’s research and development spending patterns, as disclosed in its financial reports, reflected increasing investment in THB335 and a shift away from its earlier THB001 program.

Trading status and corporate structure

Third Harmonic Bio’s common stock previously traded on The Nasdaq Stock Market under the symbol THRD. Following stockholder approval of the Plan of Dissolution, the company notified Nasdaq of its intention to voluntarily delist and deregister its common stock. The Form 25 filed on July 31, 2025 and the subsequent Form 15 filed on August 11, 2025 confirm that the company’s Nasdaq listing and Exchange Act registration have been terminated. The company’s Certificate of Dissolution, filed July 31, 2025, marks its transition into the dissolution phase under Delaware law.