Big news for the estimated 90,000 Americans with gout who don’t find relief from current gout medications. The U.S. Food and Drug Administration (FDA) in 2010 approved a drug called pegloticase, brand name Krystexxa, aimed specifically at helping those patients who don’t get better with conventional treatment.

According to answers sent via e-mail from FDA spokespersons Sarah Okada, MD, Clinical Team Leader, Rheumatology, Division of Pulmonary, Allergy, and Rheumatology Products and Badrul Chowdhury, MD, PhD, Director, Division of Pulmonary, Allergy, and Rheumatology Products, “People with severe chronic gout that has not been adequately controlled on other available therapies now have a therapeutic option that gives them a reasonably good chance of achieving control.”

Gout is a type of arthritis that occurs when uric acid builds up in blood, causing urate crystals to settle in joint, triggering gout attacks of intense pain, inflammation and stiffness. The condition affects more than six million people and more men get the condition then women. Obesity and diabetes are often associated with gout. Genetic factors and diet can also play a role in triggering the condition.

Until now, all gout medications on the market have been pills that are taken orally and prevent gout attacks by lowering uric acid in blood in one of two ways. Most commonly they decrease the production of uric acid by preventing purines, a type of protein produced naturally by the body and found in a variety of foods (such as beer and certain meats and beans), from turning into uric acid so it can’t crystallize in the joints. Other gout drugs increase the excretion of uric acid through urine.

“Patients with insufficient control, or who were not able to tolerate these medications, did not have many options, other than treatment of acute attacks of gout,” according to the e-mail from FDA spokespersons. “Krystexxa provides for the option of a different mechanism of action for patients with chronic gout who have not been adequately controlled with these other therapies, and may be uniquely helpful for treating patients with inadequately controlled severe disease that includes build up of lumps of uric acid crystals.”

Krystexxa also lowers uric acid, but in a different way. The medication is the first biologic developed for gout and requires an intravenous infusion, IV, every two weeks. This is because it involves an enzyme that wouldn’t be absorbed in pill form.

“Krystexxa is an enzyme that acts directly on uric acid, turning it into a different molecule, allantoin, that can be readily excreted in the urine,” according to the e-mail from FDA spokespersons.

Stage III clinical trials conducted by scientists at Duke University showed the drug successfully treated gout in about 40 percent of more than 200 study participants.

“We see impressive clinical results in less than six months that have never been demonstrated in any other clinical approach for gout patients,” says Paul Hamelin, president of Savient Pharmaceuticals Inc., manufacturer of Krystexxa.

But the medication is not without side effects. In approving the new drug, the FDA is recommending that physicians give patients a corticosteroid and antihistamine before an infusion to prevent the kind of allergic reactions that affected one out of every four clinical trial participants. Mild reactions included skin rashes, hives, shortness of breath, chest discomfort, redness and itching. Severe reactions included wheezing, lip or tongue swelling, changes in blood pressure and anaphylaxis cases. The FDA says no one died in the clinical trials from these reactions, but stresses they have the potential to be life-threatening.

“Reactions to the infusion occurred relatively frequently,” according to the e-mail from FDA spokespersons. “More severe, potentially life-threatening, allergic reactions occurred in about one in every 20 patients.

The FDA says other side effects include nausea, vomiting, constipation and chest pain. Krystexxa wasn’t tested on patients with congestive heart failure, so the FDA urges caution in giving it to patients with that condition.

Hyon Choi, MD, DrPH, professor of medicine at Boston University School of Medicine says this drug definitely has a role for those patients who fail to get a benefit from conventionally available gout medicine, such as allopurinol. But he says patients need to be aware of the challenges that will come with it too, especially the fact that some won’t tolerate it well.

“The problem is this is a foreign protein so people tend to develop antibodies so it loses efficacy or people develop hyper sensitive reactions,” Dr. Choi says. “Some people lose the efficacy after a few treatments and those people won’t get a benefit. But a lot of people do. But it does involve IVs, physician visits and it is costly, more than the regular oral pills. So it is useful for certain segments of gout patients, but not all of them.”

The FDA initially declined approval of the company’s drug, citing concerns about the proposed changes to the manufacturing process.

In clinical trials, 1 out of 4 patients receiving pegloticase experienced a severe allergic reaction. For that reason, the FDA has advised doctors to prescribe corticosteroids and antihistamine medications before treatment to minimize the risks.

Other side effects observed in clinical trials included gout flares, nausea, bruising, irritation of the nasal passages, constipation, chest pain and vomiting.