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Gilead Sciences, Inc.

BiotechnologyFounded 1987
Reviewed by Swet Parvadiya
Company data updated: October 2026

Leadership History

Gilead Sciences: CEO History

4 leaders · 1987 to present

Who is the CEO of Gilead Sciences?

Daniel P. O'Day is the CEO of Gilead Sciences, in the role since 2019. The first chief executive was Michael Riordan, from 1987.

Current CEO
Daniel P. O'Day (since 2019)
First CEO
Michael Riordan (1987)
Leaders documented
4
Founded
1987
NameRoleFromToYears in role
Daniel P. O'DayChairman and Chief Executive Officer2019Present7
John F. MilliganChief Executive Officer201620182
John C. MartinChief Executive Officer1996201620
Michael RiordanChief Executive Officer198719969
Who was CEO of Gilead Sciences before Daniel P. O'Day?
John F. Milligan was CEO of Gilead Sciences from 2016 to 2018, before Daniel P. O'Day took over in 2019.

Company Overview

Gilead Sciences is one of the largest US biotechnology companies, with about 17,000 employees and a market value near $180B in September 2026. It turned HIV into a manageable chronic disease with tenofovir-based medicines, cured most hepatitis C patients with Sovaldi and Harvoni, and supplied the first approved COVID-19 antiviral, Veklury. Today HIV accounts for roughly 71% of revenue, with oncology and liver disease making up most of the rest. The company is headquartered in Foster City, California.

Daniel P. O'Day

Chairman and Chief Executive Officer

2019 – Present

7 years (current)

Key Decisions & Impact

Recruited from Roche Pharmaceuticals in 2019, Daniel O'Day was brought in to engineer a critical strategic pivot for Gilead. Recognizing that the company's historic dominance in Hepatitis C was rapidly fading, he directed a reallocation of corporate capital toward building a high-quality oncology franchise. He initiated a severe restructuring of the executive team, bringing in outside talent to accelerate the integration of complex acquisitions like Immunomedics. Furthermore, he defended and expanded Gilead's crucial HIV franchise, championing the development of ultra-long-acting therapies to ensure long-term market dominance.

Legacy

O'Day's leadership has transformed Gilead from a specialized virology company into a diversified, global biopharmaceutical leader. While his aggressive oncology acquisitions required upfront capital expenditure, they provided the company with the strong, diverse clinical pipeline necessary to survive the eventual patent expirations of its core HIV medications. His strategic vision has stabilized the company's long-term revenue projections and restored investor confidence.

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John F. Milligan

Chief Executive Officer

2016 – 2018

2 years

Key Decisions & Impact

Milligan engineered the massive $11 billion acquisition of Pharmasset in 2011, securing the foundational compound that became Sovaldi.

Legacy

During his nearly three decades at Gilead, he helped build the company's HIV franchise before orchestrating the monumental financial success of the HCV cures.

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John C. Martin

Chief Executive Officer

1996 – 2016

20 years

Key Decisions & Impact

Martin relentlessly pursued the aggressive commercialization of single-pill HIV regimens, turning Gilead into the undisputed leader in infectious disease therapeutics.

Legacy

As CEO for two decades, he took Gilead from a small biotech startup to a pharmaceutical behemoth, generating tens of billions in revenue from Truvada and Sovaldi.

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Michael Riordan

Chief Executive Officer

1987 – 1996

9 years

Key Decisions & Impact

Riordan founded Gilead with an initial focus on the highly experimental field of antisense oligonucleotides before pivoting toward antiviral small molecules.

Legacy

He successfully navigated the brutal early stages of biotech funding, taking the company public in 1992 and establishing its foundational viral research culture.

Source →

Challenges & Strategic Context

Gilead's challenges are concentration and replacement. HIV products made up about 71% of FY2025 revenue, and Biktarvy faces loss of exclusivity in the next decade, so the company needs new HIV regimens (lenacapavir-based combinations such as bictegravir/lenacapavir) and non-HIV growth. Cell therapy sales fell 7% in 2025 on in- and out-of-class competition, Veklury fell 49%, and Trodelvy lost its bladder cancer indication and missed the primary endpoint of the ASCENT-07 breast cancer trial. The Medicare Part D redesign cost the HIV business an estimated $900M in 2025. In HIV, ViiV Healthcare (GSK, Pfizer and Shionogi) competes with long-acting cabotegravir regimens, and Merck is developing its own long-acting options.

Gilead Sciences CEO and Leadership FAQ

Who have been the primary Chief Executive Officers of Gilead Sciences since its founding?

Key CEOs in Gilead's history include founder Michael L. Riordan (1987-1996), John C. Martin (1996-2016, who built Gilead into a biotech colossus), John F. Milligan (2016-2018), and Daniel O'Day (2019-present).

What monumental achievements occurred during Dr. John C. Martin's 20-year tenure as CEO?

Dr. John C. Martin transformed Gilead from a small research venture into one of the world's most profitable biopharma companies. He developed the first once-daily single-tablet HIV treatments (Atripla, Truvada), executed the landmark $11 billion acquisition of Pharmasset (yielding Sovaldi/Harvoni), and expanded global medicine access.

What strategic changes has Daniel O'Day implemented since becoming CEO in 2019?

Daniel O'Day revitalized Gilead's pipeline by pivoting into oncology through the $21 billion acquisition of Immunomedics (Trodelvy), expanding Kite Pharma's CAR-T manufacturing footprint, leading the emergency scale-up of Veklury during COVID-19, and advancing long-acting lenacapavir.

What was the background of founder Dr. Michael L. Riordan when he established Gilead in 1987?

Dr. Michael L. Riordan was a physician and Harvard Medical School and Johns Hopkins graduate who, after contracting dengue fever, recognized the critical medical need for antiviral medicines that could treat systemic viral infections directly at the cellular level.

How did Dr. John F. Milligan contribute to Gilead's scientific and commercial expansion?

Dr. John F. Milligan, a research chemist who joined Gilead in 1990 as employee number 32, served as COO, CFO, and ultimately CEO (2016-2018), orchestrating the launch of Biktarvy and the visionary $11.9 billion acquisition of Kite Pharma in 2017.

What corporate governance and executive compensation principles guide Gilead's leadership?

Gilead's Board of Directors ties executive compensation to rigorous performance benchmarks including non-GAAP operating income, pipeline clinical trial progression milestones, oncology revenue diversification metrics, and total shareholder return (TSR) relative to the S&P 500 Biotechnology Index.

How did Daniel O'Day reshape Gilead's executive management committee?

Daniel O'Day recruited high-quality pharmaceutical leaders across oncology, commercial operations, and clinical development from Roche, Genentech, and Bristol Myers Squibb, modernizing Gilead's commercial execution and clinical trial design capabilities.

What scientific advisory board members shaped Gilead's early corporate culture?

Gilead's early scientific advisory board included Nobel laureates Harold Varmus and Paul Berg, along with prominent virologists, establishing a culture of uncompromised scientific rigor and molecular innovation that persists across its Foster City laboratories.

Who is the CEO of Gilead?

Daniel O'Day serves as CEO. He was hired from Roche in 2019 to execute a massive strategic pivot. Because the HIV market is saturated and Hep C is cured, O'Day has spent massive billions aggressively buying cancer startups to turn Gilead into a dominant oncology powerhouse.

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Content is for informational purposes only. Not financial advice. Data sourced from SEC filings, annual reports, and public records. See our full disclaimer and methodology.