No flash. Little drama. And it works.

Charles River Laboratories International Inc. might be the most important life sciences player you’ve never heard of. Founded in 1947, the contract research company is more than twice as old as the biotech industry it serves. Its chief executive has steered the business for more than two decades and has no plans to retire.

The Wilmington company focuses not on the eureka moments that define so many biotechs but on the behind-the-scenes services they outsource — from testing compounds for toxicity to supplying antibodies for drug production to genetically engineering mice and rats for animal drug trials.

As the life sciences sector has mushroomed in Massachusetts and beyond, Charles River Labs has emerged as an indispensable player. It works for every one of the 100 largest global drug developers and played a supporting role in more than half of the 86 new medicines approved by the Food and Drug Administration in 2014 and 2015.

“Our scale and our depth and our scientific acumen have reached the point now for a lot of things where it’s eclipsed our clients,’’ said James C. Foster, 65, the expansion-minded Charles River chief executive. “We can do it as fast or faster, as well or better scientifically, and always with a better value proposition.’’

If that sounds a tad boastful, Foster is quick to add that the value proposition involves not only saving its customers money, but letting them spend more time on “pure innovation’’ — identifying scientific breakthroughs and finding compounds that can neutralize diseases.

Customers are buying in. Charles River’s operating earnings climbed nearly 9 percent to $179.3 million last year, while sales advanced 5.1 percent to a record $1.36 billion. Its shares, which closed Friday at $73.74, have nearly doubled over the past five years, although they have fallen 8.3 percent in 2016 with the broader pullback in financial markets.

Standing by a window in a new office in Boston’s Back Bay neighborhood, Foster looked across the river for which his company is named and motioned toward Kendall Square in Cambridge.

“There are hundreds of clients within a mile of here,’’ he said.

One of those Kendall Square clients, venture capital firm MPM Capital, starts and bankrolls early-stage life sciences companies. It relies on Charles River for about 80 percent of the preclinical research and development at more than two dozen biotech companies in its portfolio. While the venture firm once worked with several contractors for everything from drug safety assessments to early-stage research experiments, it has consolidated most of its outsourcing with Charles River in recent years.

“They are the Mercedes of the industry,’’ MPM cofounder Ansbert Gadicke said. “They have a deep scientific bench, and they can help us understand the regulatory requirements and interpret the scientific data. At this point, they are really the provider for all of our portfolio.’’

Charles River is a public company with family roots. Foster’s father, veterinarian Henry Foster, founded the company to breed laboratory animals for an earlier generation of drug companies and academic research labs sprouting up in the region.

As the company grew, it became a leading supplier of mice and rat “models’’ genetically altered with human cancers or compromised immune systems for research experiments. Charles River went public in 1968 but was purchased by health care products giant Bausch & Lomb Inc. in 1984 for $110 million.

James Foster, who joined the company in 1976 as general counsel, was elevated by Bausch & Lomb to chief executive at Charles River in 1992 and ran it as a division of the parent company for seven years. When Bausch & Lomb decided to spin off the unit, Foster led a leveraged buyout in 1999. He took the company public for a second time the following year in a $224 million initial public offering.

Foster, who has led Charles River as a public company, a corporate subsidiary, and a private company with outside investors, said he has learned to adapt to different owners with different expectations as the biopharmaceutical industry has evolved.

“You always work for someone,’’ he said, a lesson he tells business students he teaches at MIT’s Sloan School of Management.

Relations with owners have not always been smooth. In 2010, at a time when Charles River’s stock was trading close to $30 a share, Foster came under sharp criticism from a group of activist investors, including hedge fund JANA Partners LLC, who objected to the price tag of a planned $1.6 billion takeover of Chinese drug maker WuXi PharmaTech Inc.

They also questioned the strategic rationale of the deal and Charles River’s track record in integrating previous acquisitions. Ultimately, the company was forced to abandon the WuXi deal — which Foster viewed as key to its global growth — and add a pair of board members backed by dissident shareholders.

But when some activists began pressing to sell or break up Charles River, Foster and the board held fast until the investors turned their attention elsewhere and ultimately cashed out of the stock. The company then resumed its acquisition binge with new intensity.

Under Foster, Charles River Labs has acquired more than 65 companies over the past 15 years, including five in the past 18 months alone. The goal has been to create a “one-stop shopping’’ model as more biopharma clients decide which services to outsource and which to keep in-house.

When it completes its $585 million buyout of WIL Research Laboratories LLC of Ashland, Ohio, a deal unveiled last month, Charles River Labs will strengthen its agricultural and chemical testing business and gain a toehold in contract drug manufacturing, a market in which it has lagged.

“They’ve expanded their capabilities enormously and really become a partner to drug developers at a much earlier stage of the discovery process,’’ said John L. Sullivan, research director at Boston health care investment bank Leerink Partners. “Their name might not be on the drug labels, but they play a critical role in the development of the drugs.’’

Competitors, from Albany Molecular Research Inc. of Albany, N.Y., to Laboratory Corporation of America of Burlington, N.C., are trying to challenge Charles River’s leadership position in the lab services business. But with Big Pharma companies doing less work in their own labs, and many biotechs operating as so-called virtual businesses that farm out most of their research, there’s plenty of room for growth in contract research.

Charles River is continuing to expand. This year, it reopened a Shrewsbury research complex it had closed in 2010. It hired more than 500 workers last year, boosting its payroll to 8,500 employees in 70 locations worldwide, including about 1,000 in Massachusetts.

It has also begun a pilot program to work in partnership with biotechs and smaller drug developers on some early-stage research at Charles River facilities, suggesting a potential new direction for the company. In that program, Charles River scientists work next to its customers’ scientists as they test new compounds.

Charles River shows no signs of slowing down. But one thing it has no intention of doing is licensing technology from academic labs and becoming a drug developer in its own right.

“We will always stop short of competing with our clients,’’ ­Foster said.

Robert Weisman can be reached at robert.weisman@globe.com. Follow him on Twitter @GlobeRobW.