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Sorbent Therapeutics Seeks to Fight Heart Failure in Unusual Arena: The Gut

Xconomy San Francisco — 

Heart failure is a huge market with 5 million sufferers in the U.S., but it can be a pretty dull space for investors, since it’s widely treated today with cheap generics that have been around a long time. So how is it that Sunnyvale, CA-based Sorbent Therapeutics was able to raise $53 million in venture capital in the past year for a new kind of drug against this disease?

What’s different here is that Sorbent is betting it has found a way to treat a common complication of heart failure by aiming at a surprising target—the gut. I heard more of the explanation recently from Sorbent’s CEO, Detlef Albrecht, after the company disclosed its latest financing from Novartis Venture Funds, Sofinnova Ventures, Arch Venture Partners, CMEA Capital, and AgeChem.

The idea at Sorbent is to develop a polymer-based drug that you swallow, and which lingers in gastrointestinal tract, acting like a sponge to soak up excess sodium, potassium, and fluids, before carrying all that extra baggage to the exits with the feces. This is different from conventional small-molecule pills, or biotech drugs, which get absorbed into the bloodstream and broken down through the liver or kidneys—where unpredictable side effects can sometimes occur. And despite the widespread availability of cheap generics like diuretics, ACE inhibitors, or aldosterone receptor antagonists, an estimated 1.2 million heart failure patients in the U.S. have no easy way to get rid of the excess fluids, and they end up getting hospitalized, Albrecht says.

It turns out quite a few people with failing hearts also have failing kidneys which prevent diuretics from working the way they should, Albrecht says. And that creates an opportunity for an alternative such as the one Sorbent is developing.

“If you can keep fluid out of the system or remove it without going through the kidney, you have an attractive product,” Albrecht says.

Albrecht has been around the block with these kind of molecules through past executive stints in R&D at Ilypsa, and a successor company, Santa Clara, CA-based Relypsa. Ilypsa developed a polymer that was supposed to be used to soak up excess phosphate molecules in the blood of patients with kidney failure who are undergoing dialysis treatment. That drug made a return for Ilypsa’s investors and employees in June of 2007, when Amgen agreed to acquire the company for $420 million in cash.

Soon after, some of the key managers—Albrecht included—started anew with Relypsa. That company took the same scientific concept and applied it in a different way—this time, creating a polymer drug designed to soak up excessive amounts of potassium that build up in the blood of kidney dialysis patients. The clinical verdict on that drug isn’t in yet, but Relypsa raised a whopping $70 million in its Series B venture round last September.

Albrecht left Relypsa in late 2009, and soon started sniffing around VC groups for new opportunities, he says. Knowing Albrecht’s experience with the Ilypsa/Relypsa crew, Jim Healy of Sofinnova Ventures and David Collier of CMEA Ventures encouraged him to take a look at Sorbent. “I was aware of it,” Albrecht says, “But there was no data in public domain, except patents. I didn’t know how good the data was.”

The company, founded in 2005, had developed its polymer to the point where it had made it into clinical trials with about 100 people. It was positioned to get rid of not just potassium, but also sodium and excess fluids, Albrecht says. But there was a problem. Investors didn’t like changes coming to Medicare reimbursement procedures. The new system said dialysis centers could no longer bill the government to reimburse for each new therapy, but were instead given a flat amount from Medicare per patient, which was supposed to cover the patient’s whole regimen. That seemed to put the squeeze on new therapies trying to enter the dialysis world, Albrecht says.

Instead, while Albrecht was scoping out the startup, he wondered if the Sorbent drug might be useful in a less crowded space like heart failure.

The professional opportunity, meanwhile, struck him as interesting—but only to a point. At the time, Sorbent was headquartered in the Chicago area, since it was founded there in 2005 by a group of former executives from Baxter Healthcare. Albrecht, a resident of the Bay Area, said he wasn’t interested in moving to Chicago. So, partly because it was Albrecht’s preference and partly to be closer to the investors and a larger biotech talent pool, Sorbent made its move to the Bay Area a year ago, he says.

Albrecht isn’t saying a whole lot yet publicly about the clinical trial plan, but I did get a sense of the patient population he has in mind. Heart failure, in which the heart muscle enlarges and loses its ability to efficiently pump blood, leads to fluid buildup in the lungs and legs, making people fatigued and chronically short of breath. While many of them can be treated with diuretics to flush the excess fluid out of their system, quite a few can’t be treated effectively because they also have chronic kidney disease. These are the heart failure patients who are the best candidates for a drug like Sorbent’s, which stays entirely within the GI tract, and never needs to go through the kidneys.

“The less the kidneys work, the less the diuretics work,” Albrecht says. “So what often happens is you go to higher diuretic doses, and that leads to increased mortality. It’s a vicious cycle.” Instead, he says, Sorbent’s drug could allow patients to go on a low-dose diuretic, get rid of excess fluids, and stay out of the hospital.

But polymer drugs have their drawbacks. They have traditionally had to be given in lots of pills per day, which is inconvenient for patients, and makes it harder for many to stick with their doctor’s instructions. Albrecht said he didn’t want to discuss yet what kind of dosing requirements Sorbent’s drug will have.

The new shot of cash, Albrecht says, will help the company get through its mid-stage clinical trial of its drug for congestive heart failure patients, Albrecht says. There is also an ongoing, randomized, placebo-controlled study that should yield data early next year, he says. The money should last through the end of 2013, by which time Sorbent ought to know what kind of drug it really has on its hands.

Like everything in biotech, this story will be driven by data. “The degree of relief our product can provide will determine degree of use,” Albrecht says.