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2 biotechs look to market knee pain treatments

Treating the aches and pains of baby boomers is turning into a speciality for some local biotechs.

Flexion Therapeutics Inc., a rapidly growing Burlington company, said Monday that it’s applied for Food and Drug Administration approval of a steroid hormone injection to treat osteoarthritis in the knee. Unlike other treatments already on the market, Flexion’s time-released medicine provides relief lasting several months.

Meanwhile, Centrexion Therapeutics Corp., led by former Pfizer Inc. chief executive Jeffrey B. Kindler, said it’s moving from Baltimore to Boston to accelerate its own pipeline of experimental pain drugs. The three-year-old startup’s lead drug candidate — a synthetic form of trans-capsaicin, a medicine derived from the chili plant — also targets osteoarthritis knee pain.


More than 14 million Americans were diagnosed with the condition last year. Many of them receive steroid or hyaluronic acid injections in their knees, some several times a year, but relief typically lasts only about two to four weeks. A large number of patients eventually resort to knee replacements.

As baby boomers age, “it’s hard to underestimate the extent of the problem,” said Dr. Timothy E. McAlindon, chief of rheumatology at Tufts Medical Center in Boston, who has consulted for Flexion. “There’s a huge unmet need for effective treatments for a common disorder.”

Like many injections now on the market, Flexion’s treatment, called Zilretta, is also a kind of inflammation-suppressing steroid. But it uses a delivery system in which small particles known as microspheres release the therapy gradually in patients’ joints over an extended period.

In a late-stage clinical study, Flexion chief executive Michael D. Clayman said, “We achieved good therapeutic concentration of the drug in the knee for up to three months following a single injection. We feel we have the first meaningful innovation in this space in decades.”

Centrexion’s experimental drug, which also is injected, will be tested in a late-stage study next year. It showed positive results in a mid-stage trial by binding to receptors at the ends of pain fibers to stop the signal sent to the brain and spinal cord, said chief medical officer Randall M. Stevens.


“The pain relief in absolute [terms] was greater than we’ve seen with other treatments,” said Stevens, a pharmaceutical industry veteran who helped develop five approved drugs at other companies, including the osteoporosis medicine Boniva. He said the Centrexion treatment lasts for up to six months.

Industry analysts have estimated Flexion’s drug eventually could become a top-selling medicine, generating $800 million to more than $1 billion a year. Patients would receive injections in their knees at the office of an orthopedic specialist, a procedure lasting less than a minute. The same system could eventually be used to administer other pain drugs.

Nine-year-old Flexion, founded by two veterans of Eli Lilly & Co., has more than doubled in size, to about 100 employees, in the past year. The FDA granted Zilretta fast-track status in 2015, a designation given to drugs that can offer significant improvement over therapies already on the market. The approval process is expected to take between six months and a year. If the medicine does get the go-ahead for US sale, Flexion could expand its staff to more than 250 by the end of next year, Clayman said.

Flexion, which raised $75 million in a 2014 initial public offering, will not set a price for its time-released injections until the medicine wins regulatory approval. But Clayman said it’s likely to be about $500 a dose.


Centrexion, a privately held company using technology developed by neurosurgery professor emeritus James Campbell at Johns Hopkins University School of Medicine, isn’t as far along. But its knee treatment eventually could compete with Flexion’s, as well as with other drugs on the market.

The move to 200 State St. in Boston will help it recruit scientific and business talent, said Kindler, who plans to commute from his Connecticut home three to four days a week. Kindler, who graduated from Tufts University and sits on its board, said he decided to launch the company partly because his wife suffers from osteoarthritis knee pain.

By February, Centrexion’s Boston office should have about 15 employees, many transferring from Baltimore. But it expects to grow substantially as more researchers are hired to develop a portfolio of treatments for different types of pain.

“We’re going to build a real important company here,” Kindler said. “Truthfully, Boston is where it’s at for biotech. This is the center for academic scientists, clinicians, investors, and business people in all the disciplines you need. You really have to be in Boston.”

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

Correction: An earlier version of this story misspelled the name of Flexion’s chief executive and incorrectly reported the date the company was granted fast-track status.