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Spero Eyes First Trial, Gets $30M More to Battle Drug-Resistant Bugs

Xconomy Boston — 

With three different ways of attacking troublesome drug-resistant bacteria in its portfolio, Spero Therapeutics has begun to resemble something of an antibiotics roll-up. And now it’s got another $30 million to continue the work, with its first big clinical test coming later this year.

Spero said today it has raised a $30 million Series B financing, matching the $30 million Series A round the company closed last June. The same investors, led by founding backer Atlas Venture, have returned to provide the new round of funding, which Spero will use to advance a pipeline of potential antibiotics for tough-to-kill bugs. The company has now raised about $63 million since its inception in 2014.

As I wrote in June, Spero started out with one program in place—a method of essentially disarming bacteria, rather than killing them. But it has since broadened its focus, deciding to accumulate assets through acquisitions and take what CEO and Atlas entrepreneur-in-residence Ankit Mahadevia called a “comprehensive approach to the space.” It cut a deal with a little-known Finnish company, Northern Antibiotics Ltd., in June. That gave Spero a group of so-called “potentiators” meant to help already-approved antibiotics handle gram-negative bacteria, which have a cellular membrane that other bacteria don’t, and that existing drugs have a tough time penetrating through. (Gram-positive bacteria, by comparison, don’t have that extra membrane and are easier to treat.)

And just a month ago, Spero inked a deal with a biotech from Montana, Promiliad Biopharma, giving it a third weapon against gram-negative infections. These drugs are next-gen versions of what are known as dihydrofolate reductase (DHFR) inhibitors—they hamper a bacterium’s ability to make DNA. While there are several other DHFR-blocking antibiotics available—among them trimethoprim (Primsol)—Mahadevia says Spero aims to develop some specifically meant for gram-negative infections, which “historically DHFR inhibitors haven’t been able to do.” (Mahadevia wouldn’t explain specifically what makes these drugs unique, other than to say they’ve got “some novel parts to the chemistry” that will enable Spero to develop them in “an IP-protected way.”)

Since the Series A, Spero has been hiring several senior level folks, many of whom come from Cubist, the Massachusetts antibiotics giant that Merck bought for about $10 billion last year. Spero has about 20 staffers now and plans to continue to put cash into its existing programs, and search for other potential assets elsewhere. Mahadevia notes that Spero has brought in one asset each year.

“I wouldn’t sign us up for that, but we’ll continue to build our pipeline aggressively from the outside,” he says. “We think we’re onto something different, something quite broad, and I think that’s why we’ve been able to really in a short time catalyze the investment that we have.”

Spero will find out soon whether all this will lead to a real impact on healthcare, and the scourge of so-called “superbugs” that can resist common antibiotics (such bacteria kill 23,000 Americans every year, according to the Centers for Disease Control and Prevention). Spero’s lead drug, known as SPR741, will begin its first clinical trial later this year, with data expected in 2017. The drug is one of Spero’s potentiators, and would be co-administered along with an antibiotic to, as Mahadevia says, “create a gap in the fence around a gram-negative bug.” The antibiotic—possibly a macrolide, for instance, a type of antibiotic that historically only works against gram-positive bugs—would then be able to find its target and do its work.

Mahadevia wouldn’t say which antibiotic the company will test SPR741 with, or what the proposed infection would be. “That’s part of the work we’re doing,” he says. Spero may consider teaming SPR741 with an antibiotic already in a pharma company’s pipeline—it would have to cut a deal to do that—or other antibiotics that are “free and clear” for Spero to use, he says.

“We’ll likely have a hybrid [approach],” he says.

Roche has an option to acquire Spero’s third program after a Phase 1 trial. Mahadevia says that work is still at an early stage, and won’t be tested in a clinic this year.

Along with Atlas, Spero’s investors include the VC arms of GlaxoSmithKline (SR One) and Merck (Merck Research Ventures), Lundbeckfond Ventures, The Kraft Group, and Partners Innovation Fund.