Companies large and small, domestic and foreign, turn to Jayun Koo for advice on securities law and general corporate matters. Jayun represents issuers, underwriters, and institutional investors in public and private securities transactions, including initial public offerings, follow-on offerings, ATMs, PIPEs, up-listing offerings, reverse mergers and other public company strategic transactions across a wide range of sizes and levels of complexity. She also handles SEC reporting and compliance and corporate governance matters and also regularly represents foreign issuers accessing the U.S. capital markets.

Emerging growth technology companies particularly appreciate Jayun’s understanding of their unique needs and her ability to provide tailored guidance and practical solutions to achieve their objectives. Jayun regularly operates as an outside general counsel for many of her clients, collaborating when necessary with the firm’s M&A, FDA, IP, Tech Transfer, Employee Benefits and Executive Compensation, and litigation teams.

Jayun’s clients also benefit from her experience and proactive approach. Her understanding of public companies’ responsibilities and disclosure requirements enables her to anticipate and address issues before they become concerns. With experience on both the issuer and underwriter side, she is especially adept at efficiently guiding clients through transactions subject to additional limitations and layers of restrictions imposed by the securities laws and the stock exchanges.

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  • Represented VBI Vaccines in its successful underwritten public offering and concurrent registered direct offering of common shares for aggregate gross proceeds of approximately $71.9 million.
  • Represented a biotechnology company in its follow-on offerings involving preferred stock units and pre-funded warrants.
  • Represented the underwriter in an underwritten offering of units and pre-funded units.
  • Represented an Israeli specialty biopharmaceutical company in its public offering of American Depositary Shares.
  • Represented PhaseRx, Inc. in its initial public offering.
  • Private securities offerings and other securities transactions.
  • Reporting obligations under the Securities Exchange Act of 1934.
  • Preparation of registration statements on Forms S-8 and S-4.
  • Compliance with corporate governance best practices and regulations, such as: NYSE and NASDAQ requirements with respect to board composition, committee charters and other listing standards; State law governing shareholder meetings; and Disclosure committee. policies and charters, information disclosure policies; and enterprise risk management policies.
  • Preparation of securities filings, including Schedule 13D and Section 16 filings.
  • Mergers and acquisitions involving public and private entities.
  • Women in Bio, Member
  • Asian American Bar Association of New York, Member


J.D., Columbia Law School, 2010, Journal of Asian Law, Staff Editor

B.A., University of Pennsylvania, 2006, magna cum laude




New York

Jayun Koo in Law360: ‘Attys Navigate IPO Drought:’
September 26, 2022

Haynes Boone Partner Jayun Koo was featured in an Law360 article. Below is an excerpt: Despite a significant drop in the volume of initial public offerings this year, capital market lawyers at several BigLaw firms are still looking to train aspiring young attorneys to bolster their practice, saying there is plenty of work in the pipeline. There had been "a steady stream" of smaller offerings this [...]