Gilead Sciences vs Pfizer: Founders, CEOs and History
Gilead Sciences was founded in 1987 by Michael L. Riordan and is led by Daniel P. O'Day. Pfizer was founded in 1849 by Charles Pfizer, Charles Erhart and is led by Albert Bourla.
Company facts
Gilead Sciences
- Founded
- 1987
- Headquarters
- Foster City, California
- Current CEO
- Daniel P. O'Day
- Employees
- 17,000
Pfizer
- Founded
- 1849
- Headquarters
- New York, New York
- Current CEO
- Albert Bourla
- Employees
- 75,000
Founders
Gilead Sciences
Michael L. Riordan
Michael Riordan founded Gilead in Foster City, California, in 1987. Before that he trained in medicine and worked in venture capital at Menlo Ventures, which provided early funding.
Pfizer
Charles Pfizer
Pfizer possesses a historic, immigrant founding story, rooted entirely in the rapid industrial expansion of 19th-century Brooklyn and defined by an effective, intensely meticulous German chemist and his ambitious confectioner cousin.
Charles Erhart
Charles Erhart's role in Pfizer's founding is less celebrated than his cousin's, partly because the company carries Charles Pfizer's name and partly because his commercial contributions were less visible than the scientific achievements that drove the company'…
CEOs and their tenures
Gilead Sciences
- Michael Riordan1987–1996
Chief Executive Officer
Chief executive of Gilead Sciences from 1987 to 1996.
Source - John C. Martin1996–2016
Chief Executive Officer
Chief executive of Gilead Sciences from 1996 to 2016.
Source - John F. Milligan2016–2018
Chief Executive Officer
Chief executive of Gilead Sciences from 2016 to 2018.
Source - Daniel P. O'Day2019–present
Chairman and Chief Executive Officer
O'Day's leadership has transformed Gilead from a specialized virology company into a diversified, global biopharmaceutical leader.
Source
Pfizer
- Ian Read2010–2018
Chief Executive Officer
Chief executive of Pfizer from 2010 until December 31, 2018; Albert Bourla succeeded him as CEO on January 1, 2019.
Source - Albert Bourla2019–present
Chairman and Chief Executive Officer
A veterinarian by training who joined Pfizer Animal Health in 1993, Bourla became CEO on January 1, 2019 and Chairman in 2020.
Source - Dave Denton2022–2026
Chief Financial Officer
Former CVS Health CFO who ran Pfizer finance through the Seagen financing and cost program, leaving on August 15, 2026 for a consumer goods company.
Source - Chris Boshoff2025–present
Chief Scientific Officer and President, Research & Development
Former Chief Oncology Officer who took over all of Pfizer R&D effective January 1, 2025.
Source - Cecile Guegan2026–present
Interim Chief Financial Officer
Previously senior vice president of finance for Pfizer's global biopharmaceuticals business; became interim CFO after Dave Denton left on August 15, 2026.
Source
Timeline: Gilead Sciences and Pfizer side by side
1849Pfizer
Pfizer Founded
Charles Pfizer and Charles Erhart founded the company in Brooklyn.
1944Pfizer
Penicillin Scale-Up
Pfizer helped industrialize penicillin production during World War II.
1987Gilead Sciences
Founding of Gilead Sciences
Michael L. Riordan founded the company, originally called Oligogen, in Foster City, California, to develop antisense and antiviral therapies.
1992Gilead Sciences
Initial Public Offering
Gilead went public on Nasdaq, giving it the capital to keep developing antiviral drugs.
2000Pfizer
Warner-Lambert Deal
Pfizer acquired Warner-Lambert, adding Lipitor.
2001Gilead Sciences
Approval of Viread
The FDA approved Viread (tenofovir disoproxil fumarate), the nucleotide analog that became the backbone of Gilead's HIV franchise.
2003Gilead Sciences
Acquisition of Triangle Pharmaceuticals
Gilead acquired Triangle Pharmaceuticals, gaining emtricitabine, which it combined with tenofovir to create Truvada.
2011Gilead Sciences
Acquisition of Pharmasset
Gilead acquired Pharmasset for about $11 billion, gaining sofosbuvir, the basis of hepatitis C cures Sovaldi and Harvoni.
2017Gilead Sciences
Acquisition of Kite Pharma
Gilead acquired Kite Pharma for about $11.9 billion, adding the CAR-T therapy Yescarta.
2020Gilead Sciences
Acquisition of Immunomedics
Gilead acquired Immunomedics for about $21 billion, adding the Trop-2 antibody-drug conjugate Trodelvy.
2020Pfizer
BioNTech COVID Vaccine Partnership
Pfizer and BioNTech brought Comirnaty through emergency authorization.
2023Pfizer
Seagen Acquisition
Pfizer completed the $43 billion Seagen acquisition.
2024Gilead Sciences
PURPOSE 1 Trial Results
Twice-yearly lenacapavir showed zero HIV infections among women in the PURPOSE 1 prevention trial.
2025Gilead Sciences
Yeztugo Approval and FY2025 Results
The FDA approved Yeztugo (lenacapavir) in June 2025 as the first twice-yearly HIV PrEP option. Gilead finished 2025 with $29.4 billion in revenue and $14.3 billion in Biktarvy sales.
2025Pfizer
Chris Boshoff Becomes CSO
Chris Boshoff became Chief Scientific Officer and President, Research & Development effective January 1, 2025.
2025Pfizer
Metsera Acquisition
Pfizer completed its acquisition of obesity drug developer Metsera in November 2025 for up to about $10 billion including CVRs.
2025Pfizer
FY2025 Revenue Base
Pfizer reported $62.579 billion of FY2025 revenue.
2026Gilead Sciences
Arcellx, Tubulis and Ouro Acquisitions
Gilead closed acquisitions of Arcellx (April, about $7.8 billion implied equity value), Tubulis (May, $3.15 billion upfront) and Ouro Medicines ($1.675 billion upfront).
2026Pfizer
Innovent Oncology Collaboration
Pfizer signed a 12-program cancer collaboration with Innovent Biologics: $650 million upfront and up to $9.85 billion in milestones.
Acquisitions
Gilead Sciences
- Arcellx, Inc.2026$7.8B
- Tubulis GmbH2026$3.1B
- Ouro Medicines2026$1.7B
- CymaBay Therapeutics2024$4.3B
- Immunomedics, Inc.2020$21B
- Forty Seven, Inc.2020$4.9B
Pfizer
- Metsera, Inc.2025$7B
- Seagen Inc.2023$43B
- Medivation Inc.2016$14B
- Wyeth2009$68B
- Pharmacia Corporation2003$60B
- Warner-Lambert Company2000$111B
Questions about Gilead Sciences vs Pfizer
Who is the CEO of Gilead Sciences, Inc. and Pfizer Inc.?
Gilead Sciences, Inc. is led by Daniel P. O'Day and Pfizer Inc. is led by Albert Bourla. Both serve as the top executive responsible for the company's strategy, operations, and financial performance.
When was Gilead Sciences, Inc. founded vs Pfizer Inc.?
Pfizer Inc. was founded in 1849 — 138 years before Gilead Sciences, Inc., which was founded in 1987. Pfizer Inc.'s longer operating history gives it a deeper track record but also potentially more institutional inertia compared to the younger Gilead Sciences, Inc..
How many employees does Gilead Sciences, Inc. have compared to Pfizer Inc.?
Gilead Sciences, Inc. employs approximately 17,000 people, while Pfizer Inc. employs approximately 75,000. Pfizer Inc. has the larger workforce at 75,000 employees, compared to Gilead Sciences, Inc.'s 17,000. A higher headcount does not necessarily imply greater efficiency — it often reflects differences in business model (e.g., manufacturing vs. software).
Where are Gilead Sciences, Inc. and Pfizer Inc. headquartered?
Both Gilead Sciences, Inc. and Pfizer Inc. are headquartered in United States, meaning they operate under the same primary regulatory and tax environment.
Who founded Gilead Sciences, Inc. and Pfizer Inc.?
Gilead Sciences, Inc. was founded by Michael L. Riordan. Pfizer Inc. was founded by Charles Pfizer, Charles Erhart.
Which company has a longer operating history — Gilead Sciences, Inc. or Pfizer Inc.?
Pfizer Inc. has been operating for approximately 177 years, making it the more established of the two companies. Gilead Sciences, Inc. has been in operation for around 39 years. A longer operating history often signals greater institutional resilience and brand recognition, though it can also mean slower adaptation to new market conditions.
Figures come from each company's filings and the sources linked beside them. Amounts reported in another currency are shown in US dollars at an approximate rate and marked with ~. Back to the Gilead Sciences vs Pfizer overview