ABP 959’s Launch: Upending a $4B Revenue Stream
Alexion’s Soliris (eculizumab) anchored the paroxysmal nocturnal hemoglobinuria (PNH) market with approximately $4 billion in global sales last year. Even listing at $440,000 to $500,000 per US patient annually, depending on payer and contract, it wasn’t just about clinical merit. Years of regulatory exclusivity, orphan drug pricing, and high switching barriers let Alexion (now AstraZeneca) extract extraordinary margins from a small patient base. This was pharma at its most calculated.
Biosimilar launches like Coherus’ Udenyca and Amgen’s Mvasi broke the $1 billion annual threshold within three years, thanks to aggressive discounts in oncology, where payers had real leverage and guidelines favored competition. PNH is tougher, slower: a rare disease, US prevalence 5,000-10,000, with deeply conservative prescriber habits. Which is exactly why Amgen’s ABP 959, freshly FDA-approved for 2025, is under the microscope. The real question: will a 20-30% net discount actually dislodge the incumbent?
Deal flow tells an early story. The expectation is a 25% lower ABP 959 list price, landing near $350,000 per patient per year. Amgen’s biggest PBM contracting file points to initial rebates driving net pricing under $300,000, assuming solid formulary status. If that holds, PBMs and plans could reclaim $50,000-$100,000 per patient, not chump change. A 20% patient switch turns into $200 million shifted within three years. On a market this rarefied, the payers are paying close attention.
For current pricing and contract benchmarks, see RxInfo.ai.
When Prescribers Drag Their Heels: The Slow Burn of Biosimilar Uptake
Listening to Amgen’s Q2 2025 earnings call, you’d almost expect ABP 959 to ramp up like biosimilar Herceptin or Avastin. It won’t. The numbers say otherwise. IQVIA’s biosimilar adoption trackers put the three-year post-launch share at just 22% for complex, specialty-driven agents, and it falls to 14% in orphan disorders. PNH? Neurologists and hematologists don’t change regimens easily. Even mild immunogenicity fears keep about half of them from even considering a switch for at least a year if patients are stable on Soliris.
But payers are in no mood to wait. By mid-2026, three of the five largest US commercial plans are set to move ABP 959 ahead of Soliris, layering on step edits and prior auth for anyone clinging to the originator. Medicaid and several BCBS plans have hinted at similar “biosimilar first” moves, following much the same playbook as Neulasta. For most rare disease prescribers, that’s more decisive than any mountain of phase III data, and, frankly, more persuasive.
The upshot? PBMs are poised to double the biosimilar adoption rate compared to oncology launches. ABP 959 topping a 25% share by late 2027 now seems realistic, even as Alexion’s sales force holds out hope for slower erosion. And, honestly, no one in the field expects a stampede. More like a slow, relentless tide.
Margins, PBMs, and the Squeeze on Pharmacies
Specialty pharmacies accustomed to Soliris’ rich wholesale acquisition cost and fat reimbursement spreads have enjoyed margins north of $5,000 per PNH script. Those days are fading. ABP 959 will come out with a 20% acquisition cost discount compared to Soliris, but reimbursement rates will peg to the biosimilar’s ASP, not the legacy brand’s. Pharmacies face margin compression as PBMs scoop up some of the surplus. This has happened with every complex, infused biosimilar so far; the story repeats.
For pharmacy operators, it’s a mixed bag: fewer dollars per fill, yes, but less inventory risk as biosimilar shares climb. Scale will matter more; smaller specialty shops that can’t land manufacturer discounts or navigate limited distribution may get squeezed right out of the channel. PBMs, on the other hand, stand ready to capture larger rebates and spreads, especially if they can drive rapid conversion from Soliris to ABP 959.
For a deeper look at PBM margin dynamics post-biosimilar, see RxPBM.ai.
For Alexion: How Much Can the Franchise Withstand?
By 2028, Alexion won’t be standing idle. The company is moving fast to migrate patients to Ultomiris (ravulizumab), its longer-acting successor, which is relatively insulated from biosimilar competition until the early 2030s. Leaked outlooks from AstraZeneca’s 2024 buy-side roadshow peg Soliris’ US revenue hit at 35-40% within two years of ABP 959’s launch, roughly $500 million if current usage trends hold. Switching to Ultomiris helps soften the blow, with pricing set a tick below Soliris, so gross margins remain robust for now.
The field is splitting. Some clinicians and patients will dig in with Soliris out of habit or comfort, others will move to Ultomiris to sidestep payer resistance, and an increasing number will go to ABP 959 if plans keep squeezing. For Alexion, at this point, Soliris is less about new starts, more about hanging on to legacy patients and fending off escalating rebates.
For ongoing news on biosimilars entering the PNH and rare disease space, track updates at RxNews.ai.
Conclusion: It’s Disruption, But Not an Avalanche
ABP 959 underlines a hard truth: biosimilar launches now revolve less around science, more around the mechanics of payer mandates and contract math. Even with 25%+ discounts, actual patient switches in PNH happen over years. Not months. Still, dollars at stake are massive. By 2027, biosimilars may grab up to 30% of the US market, reshuffling leverage among pharma, payers, PBMs, and specialty pharmacies. Alexion? They’re left managing a slow fade on Soliris, buying time with Ultomiris. Which, to me, feels like the new normal in rare disease competition.
