Infliximab Biosimilar Reimbursement Benchmark Analysis

Infliximab biosimilars have done what they were designed to do at the system level: they brought prices down. The AJMC study found they saved the U.S. health care system between $260 million and $842 million in their first five years on the market, a figure payers point to as evidence the policy worked. That savings has to come from somewhere, and for infusion practices running buy-and-bill, it comes out of the same margin that keeps the lights on.

The mechanism is straightforward. Once biosimilars entered the infliximab market, the originator's cost per infusion and per vial dropped sharply between 2017 and 2021, squeezing margins across every infliximab product, brand and biosimilar alike. For a payer, that's a budget win. For an infusion center, drug margin isn't an accounting footnote, it's the financial engine that pays staff, rent, and equipment. When the price a practice pays to acquire a vial and the rate a payer reimburses for it start moving in different directions, the practice eats the difference. A system-level savings number like $260 million to $842 million doesn't say who absorbed the cost of getting there. It's entirely possible, and the data is consistent with this, that practices have been administering infliximab biosimilars at a loss while payers and patients keep the savings.

How ASP-based payment creates a structural mismatch between what practices pay and what they receive

The Inflation Reduction Act temporarily bumped that add-on higher for biosimilars whose ASP doesn't exceed the reference product's ASP. That add-on gets most of the attention, but it's the smaller lever in this equation. The number that actually sets the payment floor is the ASP itself, and that number can move in ways a practice has no control over.

This system worked cleanly on the assumption that biosimilar prices would track reliably below the originator's price, keeping the spread between acquisition cost and reimbursement predictable. That assumption doesn't hold once acquisition costs start moving independently of the ASP calculation. An ASPE issue brief found that for five of the eight reference biologics facing biosimilar competition in 2023, biosimilar payment limits ran materially below reference product payment limits, in some cases by as much as 70%. That's a steep drop in the payment floor for the exact products that payers are pushing practices toward.

Part of the problem is timing. ASP is calculated from manufacturer sales data reported in a prior quarter, so the rate a practice gets paid today reflects market conditions from months earlier rather than what the practice is paying its distributor this week. When a payer requires a biosimilar and that biosimilar's ASP-derived payment has fallen faster than the practice's real acquisition cost, what the practice pays exceeds what the payer sends back, producing a loss on every single infusion.

Local Infusion, which runs ambulatory infusion clinics across multiple states, has documented this exact inversion. The cost to buy Inflectra runs higher than what CMS reimburses for it. Avsola is worse: its acquisition cost is even higher, set against a reimbursement rate that falls well short of covering it. A practice administering Avsola is agreeing, by the economics of the product alone, to lose money on every vial, every infusion, and most patients need more than one vial per visit.

The obvious response is that practices can improve their position through group purchasing organizations or direct manufacturer contracts. That's true as far as it goes. Better acquisition pricing through a GPO narrows the gap. It doesn't close a gap this size when the reimbursement floor sits structurally below cost. At volume, the arithmetic still runs negative.

What each infliximab product's J-code and Q3 2026 payment rate means at the claim level

Every infliximab product on the market is its own billing event. Each one carries its own HCPCS code, its own ASP-derived payment rate, and its own unit math, and treating them as interchangeable at the billing desk is how claims get underpaid before they're even submitted. As of Q3 2026, the reference product Remicade bills under J1745, described as "injection, infliximab, excludes biosimilar, 10 mg," and pays at ASP+6% calculated on the reference product's own ASP. Inflectra bills under Q5103. Renflexis bills under Q5104, and its per-10 mg payment rate runs materially below the reference product's rate in the same quarter. Avsola bills under Q5121. Each of the biosimilar codes carries its own JW and JZ modifier requirements for single-dose containers, and getting those modifiers right on every claim matters for how much of a vial gets paid for versus written off as waste.

The unit arithmetic is where the most money gets lost, and it happens quietly. Because J1745 and its biosimilar equivalents are billed per 10 mg, not per mg, a full gram dose has to be billed as a large number of units, not a large number of milligrams. Billing staff most commonly default to one unit per milligram when the correct count is one unit per 10 milligrams. For a 350 mg dose, the correct unit count is 35. Get that wrong and the claim either gets rejected outright or paid at a fraction of what it should be, and either outcome repeats on every infusion for that patient until someone catches it. One systematic unit error on a single high-dose claim is a meaningful underpayment. Multiplied across a full year of infusion volume at a typical practice, a single recurring coding mistake becomes a real dent in annual revenue.

Infliximab dosing is weight-based, so vial waste occurs predictably whenever a patient's dose doesn't land on a clean 100 mg increment, and the JW modifier applies to most of those biosimilar infusions, with a specific denial type tied directly to product confusion: billing J1745, the originator code, for a biosimilar that was actually administered. That mismatch is preventable, but only with a hard checkpoint, a pharmacy-to-billing confirmation of product name and code on every single infusion before the claim goes out the door.

How payer formulary mandates and step therapy are reshaping which products practices can administer

National payers moved in 2026 toward biosimilar-mandatory or strongly biosimilar-preferred infliximab policies, taking the decision out of the practice's hands. A practice can no longer pick the infliximab product with the healthiest spread between acquisition cost and reimbursement. It administers whatever the payer has authorized, or the claim doesn't get authorized.

UnitedHealthcare's commercial policy in 2026 is a clear example. It denies Remicade, billed under J1745, unless the prescriber documents a trial of at least 14 weeks on Inflectra or Avsola that produced minimal clinical response, or documents intolerance or contraindication to those products. Inflectra (Q5103) and Avsola (Q5121) sit on UnitedHealthcare's preferred list. Renflexis (Q5104) does not, and it requires the same medical necessity documentation as Remicade to get approved.

That pattern holds beyond UnitedHealthcare. Cigna and several Aetna plans also designate Inflectra and Avsola as preferred and classify Renflexis as non-preferred. This creates a real problem for practices, because Renflexis pays at a rate materially below the reference product's rate, and whether administering it makes financial sense depends entirely on how its actual acquisition cost stacks up against that lower payment floor, contract by contract, payer by payer.

White-bagging mandates complicate the picture further. When a payer requires a specialty pharmacy to dispense the drug instead of letting the practice acquire it directly, buy-and-bill as a model disappears for that patient. The practice keeps only the administration fee and loses the drug margin. Figuring out which model a given payer requires, and whether that requirement can be negotiated or challenged under state law, has to happen before the first prior authorization goes in, not after a claim comes back wrong.

Prior authorization timing for recurring infliximab treatments compounds the financial risk built into the product economics

Infliximab isn't a one-time treatment. Patients come back for infusions on a recurring schedule, and that recurring structure turns the prior authorization process into a repeating point of failure rather than a single hurdle cleared at intake. One missed deadline doesn't cost a practice one infusion. It can cost several.

Prior authorization denials climbed sharply in 2026, with most of that increase concentrated in high-complexity specialty infusion and biologic therapies, the exact category where payers have the strongest financial incentive to scrutinize every cycle closely. Medicare Advantage plans have made this worse for specialty injectables specifically: step therapy requirements have turned these drugs into a denial magnet, with denial rates for biologics and high-cost autoimmune therapies running common and substantial.

Payers have also tightened the mechanics around each cycle. By 2026, many require lab work before every infusion, cap how much a dose can be adjusted, set tighter reauthorization windows, and demand fresh documentation to support weight-based dosing. Each of those requirements functions as a checkpoint, and a late or incomplete submission at any one of them voids coverage for that cycle.

This produces what amounts to a reauthorization trap. If the original authorization covers a set number of sessions or a defined window, and the reauthorization request doesn't go in before that window closes, every later session in that same treatment course gets delivered with no valid authorization on file. A biologic infusion delivered without authorization represents exposure running into thousands of dollars in drug cost alone, on a single visit.

The CMS Interoperability and Prior Authorization Final Rule, CMS-0057-F, took effect in 2026 and requires payers to issue standard decisions within 7 calendar days and urgent decisions within a short defined window. It also requires payers to give a specific reason for every denial, which ends the era of vague "does not meet criteria" rejections and gives practices something concrete to appeal. The rule further requires payers to publicly report their denial rates, which gives practices a way to benchmark payer behavior and spot outliers.

None of that removes the operational burden. Authorization management for infliximab has to run as an ongoing lifecycle process tied to each patient's treatment course, tracking expiration dates, reauthorization windows, and payer-specific documentation requirements, not as a task finished once at the front end and forgotten.

AR Aging, Underpayment Data, and the Accumulation of Practice-Level Financial Damage

None of the risks described so far stay contained to a single claim. They build into measurable dysfunction in accounts receivable, and without detection at the line level, that dysfunction turns into permanent write-offs on claims that were worth a great deal of money to begin with. A single infusion visit for a biologic therapy can carry a very large billed charge, so a denied or underpaid claim at that ticket size is a cash-flow event with real weight behind it.

The scale of what's at stake appears in the benchmarks infusion and specialty practices use to judge their own AR health. The Healthcare Financial Management Association holds that late-stage AR should stay below a defined share of total receivables, and infusion-specific benchmarks set an even tighter threshold, because claim sizes are larger and the odds of ever collecting a claim drop sharply the longer it sits unresolved. A first-pass denial rate above a modest threshold signals a systemic problem, not a run of bad luck. And remittance-to-contract variance, if nobody is tracking it, can let a meaningful share of a year's collections slip through underpaid without anyone noticing.

For patients on multi-vial biosimilar regimens, these losses don't just add up, they stack. If the gap between reimbursement and acquisition cost is already negative per vial, and the practice is also absorbing underpayment on the administration side of the claim, the loss on that patient compounds across several layers at once, cycle after cycle.

The only real defense is catching the underpayment at the moment it happens, and that moment is payment posting. Drug reimbursement under buy-and-bill shifts by product, by payer, and by ASP quarter, so a payment posting process that doesn't check each remit against the expected contracted rate at the line level has no way to catch an underpayment while there's still time to correct it. Once a claim ages past that correction window, the underpayment becomes a loss the practice simply absorbs.