ESSA Pharma Inc. (EPIX)

ESSA Pharma Inc. was a clinical-stage pharmaceutical company founded in 2009 and based in Vancouver, British Columbia, with operations in South San Francisco, California. Its research focused on prostate cancer, particularly forms that no longer respond to conventional hormone therapy. The company was incorporated in Canada, and its common shares traded on Nasdaq under the symbol EPIX.

The company's lead candidate was masofaniten, also known as EPI-7386, an orally administered small molecule designed to bind the N-terminal domain of the androgen receptor. This approach was intended to address resistance mechanisms that can limit drugs targeting the receptor's ligand-binding domain. The compound was studied in patients with metastatic castration-resistant prostate cancer, including in combination with approved androgen receptor pathway inhibitors.

ESSA's science drew on work originating at the British Columbia Cancer Agency and related research collaborations. The company maintained collaboration and clinical supply arrangements with larger pharmaceutical firms, among them Janssen, Astellas, and Bayer, to evaluate combinations with existing therapies. These relationships supported clinical studies but did not result in a commercial partner for masofaniten.

In 2025, ESSA reported that results from its clinical program did not support continued development of masofaniten. The board then discontinued the program and reviewed strategic alternatives for the company, which had limited remaining resources and no marketed products. The review led to an agreement to be acquired in a transaction structured as a plan of arrangement under Canadian corporate law.

Under the arrangement, XenoTherapeutics, a Massachusetts-based nonprofit research organization focused on xenotransplantation, acquired all of ESSA's outstanding common shares through its subsidiary, Xeno Acquisition Corp. Shareholders were entitled to approximately $0.1242 per share in cash, together with one contingent value right per share. Each right carries the potential for payments of up to approximately $0.14, up to roughly $6.7 million in the aggregate, depending on the outcome of certain contingent liabilities and related expenses.

The Supreme Court of British Columbia issued its final order approving the arrangement on October 7, 2025, and ESSA announced completion of the transaction on October 9, 2025. ESSA requested that Nasdaq file a Form 25 to delist its common shares, and the form was filed on October 9, 2025. The company stated that it expected to deregister its shares under the Securities Exchange Act of 1934 about ten days after closing.

Leerink Partners served as exclusive financial advisor to ESSA, with Blake, Cassels & Graydon LLP and Skadden, Arps, Slate, Meagher & Flom LLP acting as its Canadian and U.S. legal counsel. Following the closing, ESSA became a wholly owned subsidiary of the acquirer and no longer has publicly traded securities.