Krystexxa carries a wholesale acquisition cost of around $650,000 per year, making it one of the most expensive drugs on the market. That price reflects a combination of factors: a tiny patient population, a complex biological manufacturing process, orphan drug protections, and corporate ownership that prioritizes revenue growth. No single reason explains the cost, but together they create a drug with almost no downward pricing pressure.
A Very Small Patient Pool Drives Prices Up
Krystexxa treats uncontrolled gout, a condition where the body accumulates so much uric acid that standard medications can’t bring it under control. Only about 3% to 10% of gout patients in the United States fall into this category, and an even smaller fraction end up on Krystexxa. When a drug serves a narrow population, the manufacturer spreads its research, manufacturing, and regulatory costs across far fewer paying patients. The math is straightforward: fewer patients means a higher price per patient to recoup investment and generate profit.
This is the core logic behind expensive specialty drugs. A cholesterol medication taken by tens of millions of people can be priced at a few hundred dollars a month and still generate enormous revenue. A drug taken by a few thousand people cannot. Krystexxa sits at the extreme end of that spectrum.
Biological Manufacturing Is Inherently Costly
Krystexxa is not a simple pill made from chemical ingredients. It’s a biologic, meaning it’s produced using living cells. The active ingredient is a modified version of an enzyme (uricase) that breaks down uric acid in the bloodstream. Producing it requires genetically engineered bacteria to manufacture the protein, followed by an additional chemical modification called PEGylation, where polymer chains are attached to the protein’s surface. Those polymer chains act as a shield, preventing the immune system from immediately attacking and destroying the foreign enzyme.
This is a multi-step process that demands specialized facilities, strict quality controls, and often third-party contractors for the PEGylation step. Each batch must be tested to confirm the enzyme retained its activity and the polymer coating was properly attached. Compared to manufacturing a traditional small-molecule pill, which involves mixing and compressing chemical compounds, biologics are far more expensive to produce, store, and transport (they typically require refrigeration and careful handling).
Orphan Drug Status Limits Competition
The FDA granted Krystexxa orphan drug designation in 2001 for treating severe gout that doesn’t respond to conventional therapy. Orphan drug status was created to incentivize companies to develop treatments for rare diseases, and it comes with powerful perks: tax credits during development, reduced regulatory fees, and most importantly, seven years of market exclusivity after approval. During that window, the FDA won’t approve another version of the same drug for the same condition.
Krystexxa first received marketing approval in September 2010, with exclusivity lasting through September 2017. It then received a second approval in July 2022, which triggered a new exclusivity period that hasn’t yet expired. These protections effectively block generic or biosimilar competitors from entering the market, removing the primary force that drives drug prices down over time. Without a competing product, there’s no reason for the manufacturer to lower the price.
Corporate Ownership Favors Premium Pricing
Krystexxa was originally developed by Savient Pharmaceuticals, then acquired by Horizon Therapeutics, which invested heavily in expanding the drug’s use and clinical data. In October 2023, Amgen completed its acquisition of Horizon Therapeutics in a deal that added Krystexxa to Amgen’s rare disease portfolio. Amgen described the acquisition as strengthening its inflammation lineup with “first-in-class, early-in-lifecycle medicines” and projected it would boost earnings per share starting in 2024.
That language tells you how Amgen views the drug: as a revenue growth engine. When a pharmaceutical company pays a premium to acquire another company partly for a single drug, the acquiring company has every incentive to maintain or increase that drug’s price to justify the acquisition cost. There is no generic competitor and no comparable alternative, so the pricing power is essentially unchecked by market forces.
The True Cost Goes Beyond the Drug Itself
The $650,000 annual figure covers the drug alone, but patients face additional costs layered on top. Krystexxa is given as an intravenous infusion, typically every two weeks, which means each dose involves clinic or infusion center fees, nursing time, and premedications. Before each infusion, patients receive steroids and sometimes antihistamines to reduce the risk of allergic reactions. Each of those components generates its own billing code and charge. Over a full course of treatment, these administration costs can add thousands of dollars to the total.
There’s also the cost of the immunosuppressive therapy now commonly paired with Krystexxa. A major clinical trial showed that adding methotrexate (an immune-suppressing drug) increased the proportion of patients who responded to treatment from about 39% to 71%. This co-therapy protocol has become standard practice because it prevents the body from developing antibodies that neutralize the drug, which was a major problem in earlier use. Methotrexate itself is inexpensive, but the additional blood monitoring and office visits it requires add to the overall treatment burden.
What Patients Actually Pay
Few patients pay the full list price out of pocket. Amgen runs a commercial co-pay program that can reduce out-of-pocket costs to as little as $0 for eligible patients. The catch: you must have commercial (private) insurance. The program explicitly excludes anyone covered by Medicare, Medicaid, VA benefits, TRICARE, or any other government-funded plan. Since uncontrolled gout disproportionately affects older adults, many of whom are on Medicare, a significant portion of the patient population can’t access manufacturer assistance.
For commercially insured patients, the co-pay program covers both the drug cost and infusion administration fees. But the full cost still flows through the insurance system, which means it contributes to higher premiums and plan costs for everyone. The list price matters even when individual patients don’t see it on their bills.
Why No Cheaper Alternative Exists
Uricase, the enzyme Krystexxa is built on, doesn’t naturally exist in humans. We lost the gene for it millions of years ago through evolution, which is why humans are uniquely susceptible to gout among most mammals. Krystexxa uses a pig-derived version of this enzyme, modified to work in human bodies. There is currently no oral form, no biosimilar, and no competing injectable uricase on the U.S. market. A few research groups have explored alternative versions of PEGylated uricase, but none have reached approval.
Until a biosimilar or competing biologic clears the FDA and reaches the market, Krystexxa will remain the only option for patients with refractory gout who have exhausted all other treatments. That monopoly position, combined with orphan drug protections, complex manufacturing, a small patient base, and corporate revenue targets, is why the price sits where it does.